Can this reactor design burn thorium fuel too?
We have thousands of years of thorium available.
A company spun off from MIT is claiming it has cracked the holy grail of nuclear technology: a reactor design that runs on materials the industry currently discards as waste and which could meet all of the world's power demands for the next 70 years. It's also "walk-away safe," the designers claim, making it immune to the kind …
I'm sure by the time we've burned our way through the current waste stockpile, we'll have developed better alternatives, including thorium burners. I'd like to see this line of research given a massive boost, as this is certainly our best source of power so far.
I'm curious though... does the total amount of waste take into consideration any contaminated materials as well, or just the used fuel? And how do we get at the existing stuff that's buried in various sealed sites? I'm guessing this is more for fresh and un-buried stuff.
Still, hats off to the brains behind it all!
Sure, it'll burn. Most Thorium, not 100% but really close, is 232Th and it can be bred, by absorbing neutrons, to 233U which can then be used in a reactor. Bonus, as 233U undergoes fission it emits neutrons which can be fed into the 234Th to create more fuel for the reactor. Better bonus, this works great in liquid fuel reactors like the one described.
If it really works like they say and at the cost given, all I can say is holy shit Batman, that's a long ball. Hell, even if it's a pretty good stride toward pulling it off it's still a long ball home run.
Nice work, cheers!
"If it really works like they say and at the cost given"
One thing about the cost, many current nuclear sites / nations are willing to pay lots of money to dispose of their nuclear waste*. So the operators of such a plant could get paid to burn the waste, even if it's just a small amount that only covers operational costs of the plant.
A 500 MWe plant operating for say 30 years, that's 262980 hours (call it 200k to account for downtime / maintenence). That's a lifetime supply of 100 million MWh. Even if the plant costs double the estimate (so, $3bn), the plant will be producing electricity at $30/MWh, or less than half even the cheapest of current cheap sources: http://en.wikipedia.org/wiki/Cost_of_electricity_by_source
Of course if there are many of these plants built and they have to compete between them for fuel, governments would no longer pay to get the current waste removed, but they could still probably at the least get the fuel for free. Sure, there are other cost factors involved, but essentially even if this plant costs 2-4 times what the designers claim, it will still be competitive with current fossil fuels.
*at least, I keep seeing estimates saying how many billions it would cost to get rid of the waste
"You're missing O&M (fairly minor), fuel (very small), and "cost of capital" (big) in that. would it were that simple...."
And I challenge James Micallef on building a 500 MW plant for even $3bn......
Realistically it's going to be no cheaper than a current generation reactor, and then suffer the same cost over-runs as all new technologies. In the nuclear sector the cost over-run for novel technologies is 300%.
So that makes the starting price when fully designed would be around $5bn minimum, and then the obligatory over-runs would take that first plant to $15bn. That might still develop new, workable technology that can be built subsequently at lower cost, but the electricity isn't going to be cheap from that first one.
And could I just say Andydaws, thank you for your excellent, excellent contributions!
"Actually, that's not far out of line with current costs....Votgle (the first gen III+ project in the US) is about $6bn/GW."
Well, there's a very obvious reason that the costs are close, because I used the Votgle estimates as a fair benchmark!
Worth noting that first reactor commissioning has already Votgle is already a year late for first reactor online, so the chances of completing on budget are negligible unless they've built in the fattest of fat contingencies.
@Ledswinger - hehe you're joking right? <rummages around in pockets> what can I get for 20 quid? :)
Seriously, I got the $3bn from doubling the estimate of the project designers. I have no idea how accurate or possible that is, but I think a factor of 2 on their estimate is reasonable. If it is, as you say, 3 times as much that's still not be too expensive, based on back-of-fag-packet rough calcs, always assuming that governments running old-generation reactors are willing to pay the costs to get rid of their spent fuel and thus provide these new reactors with free fuel.
@andydaws - cost of capital on $3bn would be quite large but I'm willing to bet that China / India etc would happily underwrite most of that if it meant solving their energy problems. Also (for the moment at least), credit is dirt cheap
"@Ledswinger - hehe you're joking right? <rummages around in pockets> what can I get for 20 quid? :Seriously, I got the $3bn from doubling the estimate of the project designers."
OK, you really reckon that you can get a 500 MW nuclear plant for $3bn or $1.5bn? Using totally unproven technology? I'd love to believe this was credible, but there's no evidence that it would be. At $1.5bn per 500 MW, the cost estimates are in CCGT territory. Maybe they are right, but we've had thirty years getting CCGT right, and there's no complex certifications, no complex fuel needs, no huge security needs, and we understand the underlying physics and chemistry very well indeed. If it goes catastrophically wrong you kill about fifteen engineers and technicians, with no harm to anybody else.
A CCGT takes gas, burns it in a turbine that spins a generator, and recovers power from superheated waste gas. Easy peasy. Do you really contend that these unproven nuclear technologies are comparable in their risk, complexity and cost?
"Do you really contend that these unproven nuclear technologies are comparable in their risk, complexity and cost?"
I wasn't contending anything.... maybe I should make it more clear, I have no idea what a 'traditional' nuclear power station costs to build, nor indeed a CCGT station etc. I was merely looking at the claimed cost of the designer, assume that they are being optimistic (because hey, it's their baby), and doubled their estimate.
If, as you say, their estimate is the same as CCGT plant, then it's indeed a bold (and probably off by a significant factor) claim.
Doing nuclear for double that ($3bn) is definitely overly optimistic for an initial build, but maybe can be approached if there are dozens of them being built every year for many years. More than the complex certifications, security etc, I think you hit the nail on the head with "we've had thirty years getting CCGT right".
When we are building dozens of CCGT plants, every time the builders are giving feedback to the designers to improve the design and lower the cost, as well as learning tricks and shortcuts that will reduce cost while still delivering the end result.
With nukes, there is no reason this process couldn't also happen IF we were building dozens of nuclear plants every year for many years, eventually the cost would drop significantly from the first build. BUT I doubt that this will happen, in the west at least, there is still too much unwarranted fear.
The elephant in the room on this one is that very little if any nuclear waste is buried in a sealed site. Most of it is still sitting on the reactor site where it was created and put into "temporary" storage. Particularly here in the US where we've been waiting since the 1950s for that salt site in Nevada to open only to discover it now won't happen.
Well then - why not build the new molten salt reactors on these same sites?
The sites are already there, and have experienced staff nearby, plus the waste does not have to be transported over a long distance. Existing sites will also have the high voltage generator sets and transmission transformers/wires too.
There aren't any "sealed sites".
The world's first geological repository is under construction in Sweden, but that's some years away from completion. Pretty much all the waste produced to date remains "above ground". In the UK, France and a few other places, a proportion of the waste is at reprocessing sites (Cap de la Hague in France, Sellafield UK). Even in those cases, only a minority of the waste has been reprocessed, and the fission products/non-fuel actinides separated out.
Outside that, almost all fuel remains at the reactor sites, in cooling ponds (in a couple of cases, it's in air cooled storage facilities - the largest is at the Wylfa magnox plant). In the Us, a lot of fuel has been moved out of ponds into air-cooled storage flasks, also held at individual reactor sites - since the US has failed to move ahead with a repository.
In that latter case, if they'd any sense, they'd simply move those flasks to somewhere like New Mexico, on a seismically stable site with dry weather,
"Well then - why not build the new molten salt reactors on these same sites?"
Please accept my "Great Ideas That Have Already Been Implemented" Award.
Virtually all recent nuclear projects (Oykluoto, Fallamanville, Vogtle) and all the proposed UK sites are indeed adjacent to existing or former power generation reactors. Doesn't help much with the costs. The experienced staff are already busy (and usually old), and the transmission connectors are the least of your cost worries.
The major gain in doing this is that common security can be implemented (a convenience rather than a cost saver), and the local population are usually very receptive to new nuclear reactors, reducing the planning difficulties by a few years.
I was also thinking along the lines of: if it becomes a large-scale reality and old reactors shut down, where does it get it's fuel from? So I guess option 1 is that it can directly run on previously-unused Uranium, or else Thorium.
But never mind, doesn't really matter because many of these plants can run for 50+ years, by the time they've burnt all the current waste we'll have new technology to use Thorium.
Or fusion. We're getting that within 50 years, right?
We have millions of years of thorium available. The common fallacy is to count only proven reserves, but these reserves are based on current, much depressed prices, as thorium is next to worthless. However, a 1GW plant, using a sigle ton of thorium per year could tolerate almost any price of fuel. This rises reserves of thorium to billions of tons.
El Reg's metals wide boy here. Thorium is not next to worthless. It has a negative value.
The costs of getting rid of some (radioactive waste storage, licenses etc) plus the fact that almost no one at all uses it for anything means that possession of thorium actually costs you money.
A decade or so ago I procured a 13 lb piece for a customer. The actual metal was given to me free. It then cost $27k for the licenses and transport (including 18 wheeler, police escort, the whole schlemiel) to get it to the punter. According to the industry data that was the only commercial transaction for thorium in the US that year.
Another comment on the same point. If you have a mineral with high Th content (say, tantalite, that's a possible one, or monazite for rare earths) then you can't just process the Th out and flog it onto someone. Because no one uses it. You've got to build the costs of storing radioactives into your plan. And at higher levels (say, 1% Th or so but that's just a guess) the costs of that make the original mineral worth a negative number. And there are mountains of all sorts of things out there that won't be mined because of a high Th content.
Strangely, an actual commercial use for thorium probably wouldn't require anyone to go mining for Th. It would just enable us all to tap deposits of other minerals with high Th content. Now that we've got (or are going to get) a place where we can send the Th then lots of deposits of Ta, Nb, REs and so on would become viable.
Right at the moment I've some samples of euxenite and fergusonite (Ta and Nb bearing) in a lab for testing. The question isn't "What's the Ta or Nb values?". It's "Is the Th so high that we just shouldn't bother mining these extensive and wonderfully cheap deposits in a low wage and poor country?"
I can't resist adding that in a previous job, after I had persuaded the "industrial chemist" to pursue alternative career opportunities, I found he had squirreled away a cupboard full of exotica. Including a kilo jar of thorium oxide. These had all been bought in the days before you had to fill in forms about this kind of stuff.
It "only" cost £4000 to get rid of it, making it worth even less than Tim's - i.e. -$6500 a kilo rather than -$5000.
I can't see why thorium can't be added to the waste, the layout's similar to a thorium molten salt reactor except that it misses out the intermediate heat exchanger, probably for simplicity. http://en.wikipedia.org/wiki/File:Molten_Salt_Reactor.svg has a chemical processing plant in the fuel loop too although you could probably just adjust the mix and store the reprocessed waste like we do now.
"has a chemical processing plant in the fuel loop too although you could probably just adjust the mix and store the reprocessed waste like we do now."
Not so. The loop is to extract certain poisons from the salt which kill the reaction. Before its development you needed 2 layers of different salt mix which had to remain remain separate. The chem plant makes it run with 1 mix. It was a breakthrough in making the molten salt reactor concept viable.
No, you need the chemical plant to remove the poisons even if the plant IS run without fuel breeding, or if you run separate fuel/breeder loops.
It should be obvious, really - if you're going to breed 233U from 232Th, it has to involve a neutron absorbtion, then a decay period (the actual process transmutes 232 Th to 233Pa by neutron capture, which then undergoes beta decay to become 233U). The necessary neutron flux is only available in the core, where active fission is going on. Therefore, you're pumping the breeder salt through the core, therefore it's absorbing neutrons, and if you allow the Pa burden to become too high, it closes the reaction down - and you need it to undergo two more captures to become useful fuel, ie 235U). It doesn't matter if it's mixed in with the fuel salt, or a separate circuit, its still absorbing neutrons.
MSRs also depend on active and continual removal of fission products from the fuel loop. Some of that's easy (letting Xe and I come out of solution) and some's hard (CS, Sr and similar via tricks like vacuum distillation, which is a sod, and would be a horror to maintain in a highly active environment). And if there's any production at all of higher transuranics (which there would be in there were any 238U in the fuel salt - and that's inevitably until and if you get to a completely closed 233U based cycle), there's no removal mechanism at all, short of pyrolitics or something like purex.
Can this reactor design burn thorium fuel too?
It doesn't sound too dissimilar to other Thorium-based molten salt reactors I've read about (including the fail-safe "plug" that melts and has the salts draining away into several sub-critically sized reservoirs), so I'm guessing yes. As I understand it, though, the fuel cycle for Thorium would have to include elements outside the actual reactor, for chemical separation of various waste (or "poison") isotopes that would get in the way of a self-sustaining reaction, and possibly other similar steps (for maintaining other ratios of elements). Someone here once pointed out that the chemical separation process is pretty nasty (dangerous) based on the need to use (iirc) fluorine. Apart from that, in a Thorium reactor, the main "fuel" is actually Uranium, which is a decay product of Thorium, so there shouldn't be that much difference in the reactor design.
I really, really, really hope this is real. And I really, really, really hope that if it is real, it happens.
Unfortunately, I suspect that the general population (and a good chunk of the non-general population, for that matter) will see 'nuclear', think 'fukushimachernobylmushroomcloudwasteexplodeohmygodcancer' and run screaming from our only real hope of freedom from fossil fuel.
The delays to the current increase in nukes (regardless of their type) is almost nothing to do with safety, it's the companies willing to invest in building them negotiating (demanding) a higher market energy price.
Unfortunately, since there's only one company left at the table, the conversation is mostly one-sided as we know we need a future energy supply and have almost no either viable options.
That someone at some point explains to the general populace what "Radioactive for thousands of years" means.
Because something that is radioactive for so long does emit a very low amount of energy, and it is not that dangerous as long as it is not dispersed.
The danger with radioactive stuff comes from short-lived and medium-lived isotopes.
I'm assuming there will need to be a full scale demonstration plant built, tested and certified. So it's years if not a decade or more away from commercial deployment. It's not going to be the thing that gets our government out of the hole it and its predecessors have dug, because long before its available we'll probably be having scheduled power cuts and a government telling us that it's good for us and that we're helping save the planet.
"we'll probably be having scheduled power cuts and a government telling us that it's good for us and that we're helping save the planet"
LONG POST, GET A COFFEE NOW
Very probably. From a UK perspective, this is what the near future holds for those responsible for UK energy policy:
1. Having given away sovereignty to the EU, and allowed the Eurocrats to invent the Large Combustion Plant Directive, allow one eighth of UK power generating plant to be forcibly retired by the end of 2015. That's 11.8 GW shutting down out of a total of 84 GW of reliable capacity, plus the separate closure of the Magnox plant at Wylfa, taking out another 1 GW. These retirements are already happening, and once retired there's not much chance of reinstatement - there's no commercial reason to mothball the plant, it is also very difficult to mothball coal fired plant, and there's a commercial imperative to dismantle the site and sell for redevelopment.
2. Commission a handful of new CCGT's in the next couple of years of around 6 GW (but with no central oversight of the commissioning dates, so real wing & prayer stuff). Hope that 6 GW minus 12.8 GW equals zero.
3. Introduce carbon floor tax. Look on in wonder as the marginal third of plant currently opted in for LCPD (ie coal plant that DECC think will keep running) exits the market because it isn't profitable to run. Subtract another 3 to 6 GW of capacity, and act surprised. Pray that peak demand of 60 GW continues to shrink. With a rising population, increased use of things like heat pumps, and sod all industry left to offshore, further falls in peak demand seem an act of faith, with any credible forecast indicating it ought to rise towards 62 GW.
4. Make warm, welcoming sounds about how all the many GW of renewables will fill the gap - ignoring that they will contribute nothing to peak demand because that's typically after dark on very cold, very still days. Continue to pour bill-payers money into renewables, despoiling the countryside for no benefit. Likewise, point to international interconnectors - again ignoring the fact that peak demand tends to be regional, and these can't be depended on at critical times. With Germany progressively closing down its nuclear fleet, Belgium and Switzerland likewise, the availability of surplus French nuclear power cannot be presumed, because those countries will become net importers. Historically Germany has been the swing producer of Europe, and exported power, so this is a big an unhelpful change.
5. Continue lacksadaisical UK approach to nuclear funding and approval. This is already on a knife edge, with nobody willing to commit to build unless the government agree that they will be paid double current wholesale prices. The two potential builders could both yet walk away from the table within weeks. Even so, the soonest new nuclear plants will be operational is a decade or more away. The actual construction is relatively quick - could be done in three years, but the design, procurement, legislative permissions and approvals and infrastructure enablement will treble that.
6. Realise that by January 2016 UK reserve margin will have fallen from around 20% to 8%, the lowest level in several decades - industry rules of thumb put minimum safe reserve capacity at 15%. This means that you're in trouble if more than three or four major power plants go offline at once. Convince yourself that this is fine. It isn't because you can expect two of the fifteen UK reactors to be offline even in the winter peak for statutory inspection, maintenance or repairs (you can't do the whole fleet all in the summer). So now if one or two conventional plants go down (or their transmission links fail), we're in big trouble.
7. Sometime between now and winter 2016/7 panic, and incentivise the building of new CCGT. These incentives will (as usual) be added to the peasants electricity bills. This creates a further problem, that UK generation will become yet more gas dependent, compounded by the circa 2019-2023 retirements of the older AGR nukes. Accelerated build of CCGT sounds good, because they're quick to build, but the bureacratic approvals still take years, the enabling infrastructure (eg high capacity gas lines) still takes years unless you've very lucky in location, and with procurement lead times it is still an absolute minimum of six years, often more like nine.
8. Lose next election, retire on fat, undeserved parliamentary pension, with equally undeserved "resettlement grant". Or in the case of DECC, retire early on gold plated and undeserved PCPS pension. Laugh at how you've made a comfortable and secure living from f***ing the country over.
If you've got this far, well done. There's a few minor simplifications in all of this, but as a broad brush this is all based on fact. Which is most unfortunate. If El Reg want to do some more digging to establish whether this is correct or not then I'd be willing to give some pointers to how to go about it.
>> Very probably. From a UK perspective, this is what the near future holds for those responsible for UK energy policy:
Brilliant, and what I've been trying to tell (without having all the numbers to hand) people for years. There is just one thing left out ..
At each stage of crisis, the treehuggers will wave their hands in the air dismissively, and point out that a) wind is reliable because it's always windy somewhere, and b) when we get smart meters, we'll **just** adjust our lecky usage to suit. Of course, anyone who actually has any idea how things actually works knows that both those arguments are male bovine manure.
The idiots in Westminster will just keep believing this idealogical rubbish, and keep repeating it in response to any criticism or suggestion of impending doom.
Meanwhile, anyone who cares about living a normal life is starting to look at putting their own small diesel genny in (if they are ina position to) - with heat recovery to make it (probably) cheaper than mains lecky for at least some of the time !
Written as one of those of us who remember the power cuts in the 70's, and how nuclear saved out bacon back then.
"Although the idea of disolving stuff in molten salt is quite enthralling."
It's common in many industrial processes already e.g. aluminium production. Note that the article should say a salt not salt which many might take to be sodium chloride.
"Or to put it another way, salt."
This has been a regular part of MSR designs. To remain solid the plug has to be actively cooled.
So a power failure to the support systems (as happened at Fukushima) goes like this.
Reactor contents spread out in holding tank and go sub critical and await collection and remelting. Massive increase in surface area allows heat to be taken away through conduction and (thermal) radiation.
I think you slightly underestimate the heat removal issue - we're talking in the order of 10-20MW in the immediate aftermath of a fuel drain-down. Expecting to do that simply through convection into air would require a pretty immense large area, nless you assume either pumped flow, or two-phase of some sort - and that implies a secondary coolant supply (probably water)
In reality, it probably two-phase cooling to get the decay heat away - which puts you back in the same sort of place that you've got on the 72-hour passive cooling arrangements on an AP1000 or EU-BWR. That is, a tank above the decay heat source, allowing boiling off the walls of the fuel draw down tank, with water supply by gravity.
Oh, and by the way - that drain-down tank is going to be a pretty huge source of "gamma shine" - which means it'd have to be behind several meters of concrete, and but still have to have good air/water low. And it also means that any equipment associated with it would have to be entirely remote-operation, and maintenance. Once that tank had been used, you'd not be re-entering it's immediate area for a few decades, to fix anything - like the pumps required to move the fuel back into the reactor.
That you won't be going near the tank for decades is better than not going within 100km of the destroyed nuclear power plant for eons. The point is that the tank is there for a major catastrophic disaster. So it doesn't matter if it takes days or weeks to cool down or that you might never be able to get the contents out.
I visited Fukushima City last year. It's about 60km NW from the Fukushima Daiichi plant on the coast, in line with one of the contamination plumes. It's got a higher background count than it did before the explosions and releases but it's not been evacuated. If I spent a year there I'd have picked up about 8-10 mSv of exposure or about 10% of the annual permitted dosage of a nuclear industry worker.
Is that true with regard to the storage tanks?
I'm an engineer with a professional passing interest in nuclear power. I've read numerous *shudders to say it* Wikipedia articles on the 1950's experiments into molten salt reactors and thorium reactors.
Is the energy density of the salt sufficiently high that decay heat is only a limited meltdown/containment failure risk? So passive cooling arrangements and heat sinks are sufficient.
Are tanks such as these really going to the that highly irradiated, the 1950's salt reactors, if the articles are correct, were routinely left unattended to "trip" off using this facility. That would suggest regular occurences of emptying the drain down tanks which would be unlikely if there was a high radiological risk.
It is however nice to see some new fast reactor concepts being considered it must be better to burn through our waste and create ultimate waste that only requires 100's of years of storage rather than 10,000's.
"Is the energy density of the salt sufficiently high that decay heat is only a limited meltdown/containment failure risk? So passive cooling arrangements and heat sinks are sufficient."
I've not considered density per se - I don't think it's a major driver in this. What I'm working on is a simple assumption that the decay heat removal requirements in toto are roughly similar between thermal designs - which has to be agood assumption. For a 500MWe unit, even assuming a 40-50% thermal efficiency, you're still producing 1-1.2GW at full power. And decay curves give us 7% or so of full power heat production on shutdown ((70MW or so) decaying over the first day to 20MW or so, and down to 10MW in another couple of days.
That's a lot of heat to lose - and without making the drain down tank huge, or of a geometry that'd be hideous to shield, I really can't see passive air cooling doing the job.
There's also a bit of a misunderstanding about the Oak Ridge reactors. They were extremely small - 5MWTh at full power, if I recall rightly. It's also worth understanding that yes, they were drained down - but also that they operated only intermittently. They also lacked any breeder blanket/salt arrangements, and (I think) had nothing like the full fission product extraction functions that would be needed in a commercial design. And, let's recall - radiological standards in the fifties were by current standards hideously lax!
I agree re the advanced fast concepts - and in all honest, see concepts like IFR as far more developed and ultimately viable that MSR. For the longer term, I suspect that the lead-cooled designs will emerge as leaders - concepts like BREST-1200 using online electrochemical processing of nitrate fuel, and operating at 700--800C have to be attractive. Yes, there are coolant chemistry issues (to do with the behaviour of oxygen in lead), but they look minor compared to the chemical challenges of MSR!
Hay, let's not down-vote a reply just because you don't like its implications. Most of us laypeople understand so few of the facts about this stuff that any and all educational replies are welcome.
You may think andydaws has missed the point, but unless his facts are wrong I don't think a downvote is fair.
Oil Barons want to make money, they don't particularly have some love affair with oil. They will simply start investing in this if they think it will return a good profit. At some point they will become Nuke Barons...
Another upside of not having to use fossil fuels for electricity is that the dwindling supply can be used for agriculture and medicine to a greater degree...
It's even more subtle than that....
I once got stuck next to the Tech Director of the UK's biggest plastic bag maker on a flight back from India (oh, the glamour of international business.....).
Most of the material that goes into plastics is used simply because there's not much other use for it. It's not readily crackable for petroleum products, and it's a bit more valuable than it would be just leaving it as part of the Asphalt residue. If the plastics industry didn't buy it, it'd mostly just end up in road tar - as the money is getting the petroleum bits out.
I can see Texans sweating over this long term... But short term, the U.S seems to be more focused on reducing reliance on foreign oil - something I'm sure the US oil Co's would see as being good for business. In any case, I'm sure there will be coal/oil/gas plants for many years to come, and cars won't be running on nuclear reactors any time soon anyway.
This would push governments strongly into higher electricity taxes.
This is biggest con going in the energy world: governments trying to make us consume less energy. As they are dependent on the vast revenues they get from energy (most of what you pay at the pump is tax), making us use less simply means the price will go up. The more you save in energy, the less you will save in cost terms.
This is also why I had to laugh at UK fuel strikes a long way back: Gordon Brown urging BP to lower prices was a bit like Gary Glitter and Jimmy Savile asking Catholic priests to go easy on them kids. They must have laughed themselves silly when they met.
In view of Peak Oil, it's high time we started planning to save oil for things that we can't make any other way. (Plastics, etc.) In other words, it's becoming too precious to burn for energy.
Fossil fuels took hundreds of millions of years to form, and there won't be any more in the lifetime of the human race. So let's take it easy consuming them.
In practice peak oil really refers to "peak cheap high quality oil". There's no shortage of hydrocarbons on the planet, and not even any shortage of oil - just that what's left is finite, and is progressively more expensive to produce and usually lower quality.
For product purposes you could distil what you want (rather inefficiently) from coal, you could use tar, or the more problematic oil reserves (deep sea sub-salt, shale oil etc). Or you can use natural gas, and even after all of those you've got things that we haven't a scooby how to exploit yet, such as gas hydrates.
The threat of peak oil is particularly to transport, since you want cheap, easily refined oil with high yields of the fractions suitable for internal combustion engines.
And if fission takes off, there's even work under way to use spare nuclear power to produce synthetic hydrocarbons. The US Navy's interested because it means carriers have to pack less fuel each time they refit. If they can pull it off, the oil companies will probably be paying more serious attention to nuclear power since it could actually disrupt their bread-and-butter industries.
What about them? Since the oil shocks of the 1970's, only about 3% of America's (for example) electricity supply comes from oil. The same goes for say, China which said company thinks would be a good market for the product. Most of their electricity comes from coal.
The only places that use oil for electricity are places swimming in oil - like Saudi Arabia or Iraq. And they would prefer instead to export it instead of consume it.
The salt plug is not a new concept, and has been around as long at molten salt reactors. Every LiFTER/MSR design has it, because it's an obvious, simple, and failure resistant safety feature. MSRs are also nice in that once they are off, it's relatively easy to turn them back on, which also means that if there is an issue there isn't as much incentive to try to keep it running. Let it shut off, sort out whats going on, then turn it back on. Easy.
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All your pipe work is full of solid salt. How do you melt it again?
Most of the salt will have drained into the holding tank. The pipes won't be blocked... rather crusty, perhaps, but they'd have lots of space still.
I am not a nuke engineer, but restarting the reactor doesn't seem like an impossible task. You heat your fuel load up to melting point in a filler tank above the reactor, and heat up the inlet sections of the reactor chamber so the fuel doesn't refreeze. You then let gravity drain the molten fuel into the reactor chamber, where nuclear reactions will keep it warm. It can then flow through the outlet pipes into teh heat exchangers, melting any residue as it goes. You might need to heat up the fuel pump to get it started again, as it would have to be above the heat exchanger and wouldn't have the hottest fuel running through it.
Hell, you could just lag the whole thing in heating elements, if it came to that. I don't doubt that the real system is rather more elegant.
It's slightly more complex than that Ru - let's recall we're discussing a mass of heavily radioactive material, that's only pump-amble when heated to something over 400-500C.
And no, I don't think you can make easy assumptions about drain-downs clearing pipework. Recall that this stuff starts cooling as soon as the nuclear reaction is closed down - and you've not a massive temperature range between operating range and solidification (since the meltable plug wouldn't work otherwise).
All of this has to be done technologies that basically involve no moving parts in contact with the actual salt
The thermal stressing implicit in (say) having one end of a heat exchanger at 500C, with the other end isolated from flow, maybe C cooler don't bear thinking about. Once, about 30 years ago I spent an amusing month modelling thermal stresses in the boiler skirt of the proposed commercial fast reactor, during a shutdown transient. it'd shear mild steel, easily. That didn't involve anything so severe as this.
And let's also recall, any pipework failure here doesn't just involve a loss of cooling function - it's spilling actual fuel, in a highly corrosive salt matrix,
Well, rather then speculate, lets see what someone who ACTUALLY RAN a MSR thought of the difficulties involved:
"From the months of operation and experiments, a very favorable picture emerged. In properly designed equipment, handling the high-melting salt proved to be easy. Maintenance of the radioactive systems was not easy, but there were no unforeseen difficulties, and control of contamination was, if anything less difficult than expected."
-- PAUL N. HAUBENREICH and J. R. ENGEL, "EXPERIENCE WITH THE MOLTEN-SALT
REACTOR EXPERIMENT," September 19, 1969
Arguably "easy" was overly optimistic, but the difficulties on the startup and shutdown procedure where a solved issue before 1970. MSRE was stopped and started multiple times during it's lifetime, so I would say the above comment covers that information. If any of you have a more authoritative source, I'd love to see it.
What on earth are you doing? Deriding a knowledgeable man with a misapplied citation, and as if that was not enough, spicing it up with ALL CAPS?
Problem is, that citation applies to a low-power experimental reactor. Even fusion is easy to achieve on that level.
Remember the Farnsworth device? Many geeks have built one at home. Of course, conveniently forgetting to tell their significant others, what they are actually up to. Some people just cannot cope with the knowledge of free neutrons flying around.
Andydaws, on the other hand, was talking about industrial scale. 1,21 jigawatts or thereabouts. Even a thing so simple as a piece of wire becomes a monster at the kiloamper scale - harder to calculate, harder to produce, harder to maintain. And most of the difficulties tend to increase exponentially.
Well, I've grown weary of all the thorium talk. It has definitely gone beyond technical - infinite repeats of the same old cliche's, from the thousands. It is a matter of faith now. Repeated like a mantra, propagated like a myth. Perhaps more plausible than some other myths, and it has chances to become a reality, but still a myth at the current stage. All puns fully intended.
Yes, thorium cycle looks so promising on the paper.
Yes, there is lots of thorium available.
Yes, there was a successful test reactor running in the sixties.
As for the "killed by the military-industrial complex" meme - well, duh. No.
Yes, it could be shut down for the weekends, unlike conventional reactors.
Yes, it could be cleaned out and refuelled relatively easily.
Yes, it could be started quite easily.
But there is another side to that coin, which gets so thoroughly ignored, so thoroughly rejected. Another telltale sign of a mythology instead of technology.
They could shut it down periodically - but then again, they absolutely had to. Reaction was not sustainable for the long periods. Removal of the inhibitors is extremely difficult here, as Andy has explained so many times. It needs a major breakthrough to become viable. And sadly, miracles are quite rare in that field.
They could shut it down quickly - but mainly because of the small size. Some of the residual heat could be absorbed in the structure and could be safely left there for a weekend. Few degrees one way or another did not matter much.
More power, more heat to remove - much slower shutdown sequences (yes, well, reaction stops quickly, but it takes many weekends before the reactor can be touched again)
Startup sequences suffer from the same effect - it takes quite a lot of time and work to get to the proper operating range.
They could clean it rather easily - again, because of the small scales involved. Many miles of plumbing and many tons of nasty substances are a much different story. And online cleaning is next to impossible right now.
Bottom line - this test reactor did confirm that the thorium cycle actually works. Which is wonderful. But those technical solutions do not scale much beyond that capacity point.
"What on earth are you doing? Deriding a knowledgeable man with a misapplied citation, and as if that was not enough, spicing it up with ALL CAPS?"
The PDF of the original article printed their names in all caps. This was common well into the 80's I cut and pasted there names from the title page of the article, rather then typing it in again. I am sorry of that offends your sensitive sensibilities.
"Andydaws, on the other hand, was talking about industrial scale. 1,21 jigawatts or thereabouts. Even a thing so simple as a piece of wire becomes a monster at the kiloamper scale - harder to calculate, harder to produce, harder to maintain. And most of the difficulties tend to increase exponentially."
Commercial viability starts at around 200 MW. While it is true that MSRE only ran at a 7MW, there have been no experiments testing above that. Any assertions about the difficulties really need experiments. We call it "science" maybe you have heard of it? Fortunately there are at this time a number of groups interested in conducting these experiments. If we're lucky, we'll get to see what really happens.
"Well, I've grown weary of all the thorium talk. It has definitely gone beyond technical - infinite repeats of the same old cliche's, from the thousands. It is a matter of faith now. Repeated like a mantra, propagated like a myth. Perhaps more plausible than some other myths, and it has chances to become a reality, but still a myth at the current stage. All puns fully intended."
The article was not talking about thorium as a fuel, It's only worth discussing as a the design similarities, should lead to similar properties (maybe not, but lets do some science and find out!)
"As for the "killed by the military-industrial complex" meme - well, duh. No."
Not really sure where this is coming from. I didn't mention it. I also did not mention the Illuminati, Xenu, or Atlantis.
"Bottom line - this test reactor did confirm that the thorium cycle actually works. Which is wonderful. But those technical solutions do not scale much beyond that capacity point."
This is speculation. Let's test it and find out. We need a 200MW reactor to be viable. I suspect using these student's idea, we dont even need that, but there are existing commercial reactors operating at this level so it's a decent target. Lets see how a real one actually performs. At least see what happens at say the 50MW level.
Some of those all-caps came from the paper, but the line "ACTUALLY RAN a MSR" came from you. It carried quite a lot of emotional bias. Not to mention that Andy's educated guess is quite different from a speculation.
OK, from my part it would have been better, if I had separated general ranting into a separate comment. Most of it was not about you personally. Then again, it shouldn't be a big problem, there were enough clues of ranting and jesting available in the comment.
One full agreement too. 50MW+ online plant would be a better test of viability. Most of the scaling issues would be apparent at that point.
Restarting it is a security issue. This is a walk away solution, it fails and you walk away, at least for some period of time.
You would need to make that holding tank removable, and that is not an easy task considering the volume it needs to be able to absorb all that heat generated in a failure process.
I do not think that these are designed to be restarted after such a failure, that is to be classed as an accident. They are just designed to be safe to the environment when an accident happens.
I would be happy to be proven wrong.
But, as I've pointed out before, all the drain-down gains you is that it ensures there's no continuing reaction. You have exactly the same problem of decay heat removal. Which is probably harder with a discrete mass, than if fuel is divided into individual pins (think of the surface area:volume ratio.
Let's just be clear - there was no continuing chain reaction at Fukushima. There was none at TMI.
In both of those cases, the issue was of decay heat removal.
And I'd really not try to "absorb" all the heat from decay. Assuming the average production over the first day of an accident is about 10MW (which is probably optimistic),and that's 860 Gigajoules - enough to raise about 1000 tonnes of steel from room temperature from it's melting point, and then to melt it.
You can't "absorb" the heat - you have to get rid of it to the atmosphere, or to water.
The British public are actually a pretty pragmatic lot, and unlike many of our foreign counterparts, we're much less likely to let an accident at an ancient design of nuclear plant built on a fault line in the world's worst earthquake zone dissuade us from building modern reactors here if it's good for our economy. Multiple polls in the last couple of years have shown that Brits like nuclear energy just fine, see e.g.
And a Daily Mail article highlighting how much we could save by scrapping wind and investing in Nuclear. The reader comments don't seem to reflect your caricature of that august publication's readership;
The real obstacle to nuclear is the typically large up-front cost, as compared to the stealth taxes which can be used to subsidize renewables.
"The real obstacle to nuclear is the typically large up-front cost, as compared to the stealth taxes which can be used to subsidize renewables."
Less of a problem than you might think for the nuke developers (we'll get to the customers further down). EdF and Hitachi want to invest in new UK nuclear plant, and if need be both would borrow money to do it. Energy companies and money markets have already found around £20bn to throw at renewables, in return for the subsidies, which come in three main forms: "must run" status - a huge hidden subsidy that requires National Grid to take anything that renewables generate; ROCs, or renewable obligation certificates granted to renewables operators which can then be sold profitably to fossil fuel generators; and then the further preferential rates that renewables can be sold for in the form of LECs (levy exemption certificates). And that's over and above the wholesale price. WInd farms under construction now expect to get wholesale prices of around £45/MWh, ROCs worth around £43/MWh and LECs worth around £5/MWh. There's no price put upon the "must run" status, but given that the merit curve would normally put such costly plant at the wrong end of the curve, I'd guess that we're actually talking about something with a value in the region of £30-£60/MWh.
So money to build isn't the problem. What is at issue is the risk over the project life, given the capricious and inept actions of governments and regulators, and that leads to higher financing and margin needs, which feed into higher rates. Whilst government are happy to give these guarantees of around £100+ per MWh to ineffectual wind farms, they seem to be rather more concerned about offering this to nuclear.
But what about customers? The result of going nuclear is more expensive electricity (like double what you now pay). If you don't want your power prices to go up by that much, then renewables need to be stopped, and nukes kicked into the long grass, and the solution then is a dash for gas (accompanied by a dash for fracking, to reduce the security of supply concerns).
Even if you stop the madcap renewable subsidies, you create a problem because of the huge installed wind capacity, in that these subsidies were contractual promises by government. If that "regulatory risk" crystallises in the form of a policy change that unilaterally cuts the over-generous subsidies, then why would energy companies and financiers invest further billions on the back of a promise to offer subsidies for nuclear from the same people? And that's the big hairy deal - renewables were never a solution, and they've made the underlying problems of cost worse. Any intelligent person could see how this would/will end, but still DECC and successive governments, egged on by the Wankers of Brussels chose policies that cost more but fixed nothing. So do we continue to pour money down that drain, or do we stop it and find that nobody will lend us the money to build a proper solution?
It wouldn't solve the problem, but we could all feel better if all of DECC, all of the consultants they employ, and all politicians involved over the past thirty years were taken to Beachy Head and thrown off.
Small point of information....
"WInd farms under construction now expect to get wholesale prices of around £45/MWh, ROCs worth around £43/MWh and LECs worth around £5/MWh. "
A ROC is worth rather more than that. They pay out two ways. One is the baseline price, which is what you've got there. The second is the payment from the "buy-out" fund.
Basically, any supplier who can't source enough ROCs pays a "fine" to DECC, equivalent to what the shortfall of ROCs should have cost. This is then divided up by those who have produced ROCs as a credit.
It's usually been worth £5-10 per ROC. Last year was the lowest ever, being worth an extra £3.58.
So the real worth of an ROC is about £46.60.
I know it is only anecdotal and I suspect your stereotypes hold quite well but my dad was a Lib Dem councillor, and a "green" type, and also very much pro-nuclear.
All these groups have people who are not morons and who are not blinkered.
What we need is for the sane members to push to have their voices heard.
That's what's confusing me: exactly what is new here? I'm all for nuke power from safe reactors and would love for this to take off, but I'm not seeing what the magic is in this new announcement. I thought our current nuclear 'waste' was only wasted because political constraints prevented it from being reprocessed?
Because, at the time, most of the reactors that used spent fuel were designed to ALSO produce high-purity nuclear fuel: the kind you need for WARHEADS. This and other Generation IV reactors, OTOH, are designed to consume the fuel as completely as possible: leaving probably only reactor poisons that by their nature aren't much good for any kind of fission reaction regardless of their purity level.
That said, I'm getting a feeling of "too good to be true" out of this reactor design. Many people claim "fail-safe" designs, but can they be conclusively proven? I'd be more interested in their work if they can substantiate their claims of utility and safety.
" I'd be more interested in their work if they can substantiate their claims of utility and safety."
How about running the plant at full power then turning off the coolant pumps as a demonstration?
in particular, the Thorium cycle: breed U233 from Th232, and then fission the U233. Takes a lot more neutrons to get all the way up from U233 to Plutonium, so production of Plutonium will be minimal.
U235 production might be more of a worry, but it involves isotope separation to extract it rather than chemistry. Hard to build a Uranium isotope separation plant without being noticed.
However, 233U is also fissile. Look up the bizarrely named "Teapot" bomb test.
The "prolifeferation-proof" claims for MSR leave me a little cold. It's usually claimed that the 233U produced is laced with a small but significant 232U content, and that this makes the resulting material hard to handle. But, looking at the decay chains, the 232U wouldn't be that problematic - it's it's decay daughters that are more of an issue.
So, first, assuming that there's an efficient Pa extraction process, it's hard to see why there'd be a parallel extraction of 232U - or that the two couldn't be separated chemically subsequently. Second, even if that weren't the case, chemical removal of the highly active daughters should be relatively simple (no harder than conventional extraction of Pu from spent fuel).
If you leave that in the salt solution, then it'll be consumed as nuclear fuel.
This isn't any different conceptually to a thorium reactor and it's been pointed out many times that thorium burners can easily eat what's currently classified as "waste"
This is important, when you realise that the high level radioactivity associated with spent rods in current technology is Cobalt and Caesium, with a dangerous lifepsan of about 200-500 years. After that, your waste repository becomes a low-emission, extremely high quality plutonium mine (98% U238) - and before that the Pu is easily separated from the nasties via chemical processes (in a thorium reactor you leave them in solution to burn up. It's only U234 whic h needs to be removed as it will poison the process if levels get too high. It's all pretty elegant, enriching isn't needed and because 100% of the fuel is used, a lump of thorium goes 30-40 times further than the same size lump of reactor-grade uranium (the process can be used to convert u238 to reactor fuel, eliminating 99% of the current volume of "high-level nuclear waste")
Even better, as it gives depleted uranium an economic value, there's less incentive to go making bullets out of the stuff (it burns like magnesium (which is why it's so devastating against tank crews) and it's chemically pretty toxic, no matter how "safe" it is radioactively speaking, so having DU-dust in the environment is not a good thing. Plutonium is an equally hazardous chemical toxin)
FWIW, boiling water reactor plants are highly inefficient for power generation. 60-70% of the energy liberated from fission ends up going up the cooling tower. The only way to improve things is to both go hotter (more efficient thermodynamics) and to make use of the "waste" heat (A norwegian streel mill is experimenting with this as a process heat source for steel mills, but anything which requires process heat can use it and the final low grade heat could trivially be used by agriculture or regional heating systems. Process heat can actually be increased slightly by using it to power heat pumps (cold stores, etc) using the electrolux cycle.
If you could make intrinsically safe units (solid state RTGs) tamperproof and politically acceptable then a 60-300kW unit could be plunked in the basement of medium sized apartment blocks, generating heat, cold and power for most of the inhabitants, or possibly a neighbourhood - reviving Edison's original vision of selling both services combined.
"This is important, when you realise that the high level radioactivity associated with spent rods in current technology is Cobalt and Caesium, with a dangerous lifepsan of about 200-500 years. After that, your waste repository becomes a low-emission, extremely high quality plutonium mine (98% U238) - and before that the Pu is easily separated from the nasties via chemical processes (in a thorium reactor you leave them in solution to burn up. It's only U234 whic h needs to be removed as it will poison the process if levels get too high. It's all pretty elegant, enriching isn't needed and because 100% of the fuel is used, a lump of thorium goes 30-40 times further than the same size lump of reactor-grade uranium (the process can be used to convert u238 to reactor fuel, eliminating 99% of the current volume of "high-level nuclear waste")"
Mostly correct (certainly in the fission products argument), but you miss a few of the "hard to handle" products - mostly the "heavier than plutonium" transuranics like Amerecium. They're the biggest contributor to spent fuel activity after the 200-300 year mark, and will keep fuel a lot hotter than the original ore (the baseline target for disposal) for some thousands of years. And no, an MSR cycle doesn't make significantly smaller proportions of those than a uranium one (after all, it's still ultimately fissioning uranium, with a 238 content in there).
They're fissionable - but not very much so at thermal energies. They can be burned, but only in fast reactors.
That's in large measure the elegance of design like IFR, that use a mixed actinide metal fuel. Using a pyroprocessing method that's basically electroplating in a molten salt medium, you don't ever need to separate the U/Pu/Am etc. from each other. The real virtue, though, is it doesn't have to happen in real time - the fuel can have a couple of years of cooling/decay, to get rid of the really hot stuff, then processed. With an MSR, you have to do it "real time", otherwise the reactor shuts down.
And looking at the reliability challenges of operating plant in a "hot" enviroment, real-timne scares me sh*tless.
Depleted uranium isn't particularly toxic either in its metal form (or oxide if it's the result of a DU weapon hitting an armoured vehicle and lighting off). Most uranium compounds are not absorbed easily by the body and excreted (if ingested or inhaled) quite soon after exposure. Same for plutonium although it is a bit more biologically reactive than uranium. The radiotoxicity of uranium generally (U-235 and U-238 which makes up nearly all of the uranium around) is very low; the raw ores which include billions of years of decay products are a lot more radioactive than refined metal and oxide-form fuel pellets. Pu isotopes are a lot more radioactive with shorter half-lifes and hence more radiologically dangerous if ingested or inhaled but again they don't tend to linger.
After WWII when uranium and plutonium became strategic materials being processed in tonne quantities in factories and enrichment plants a lot of research was done on their effects on the human body as contamination, ingestion, inhalation etc. were going to happen. The experimental results were as I described above, not much basically. There are a lot of other metals which are a lot more dangerous and biologically active such as arsenic, cadmium, beryllium, lead etc.
It wont be walk away safe.
Pu is fast fissile - it will be fissile without the moderator - tipping it into the holding tank will probably increase the reaction rate. Not what you want at all.
The real trouble with Pu is its so chemically different from anything else in the mix that even an idiot could extract it from the waste and make a weapon - if they lived long enough.
It might be easy to put one of these in a tower block cellar but any financial benefit would be lost by the small army needed to protect it.
It certainly sounds like they're on to something here. Kudos to them.
However... salt? An extremely corrosive substance (not the most corrosive by any means but still...) mixed with radioactive materials? Reassurances, please.
And, of course, even if all goes well, I'd say that it'll be 10 to 15 years before the first small-scale reactor is built to evaluate the safety/commercial issues.
That's just the way it is, folks.
...but therein lies a problem. Since these reactors aren't amenable to produce nuclear fuel capable of being weaponized, it will be a hard sell in the US. It will be a harder sell because of the billions already spent for the current setup...you know 'we can't let all this go to waste?'
But therein lies a safer future for multiple good reasons.
Apparently, these will mainly be going to China; not expected to sell well in US. As a life-long nuclear detractor that statement gives me some hope in this new/old technology. I had always believed that the nuclear power that we bought in the 'seventies was primarily for the purpose of arms manufacture. That was one of my main objections (the other being the long half-life of waste with no good plan for its disposal). Let's assume that my assumption was correct. Now, a technology conceived half a century ago but, for political reasons, not really developed until recently may soon be exported from USA to China. If so, it surely won't be for their ease of weapons manufacture. Good. That is how it should have always been. I am not completely sold yet. But this, and some other breeder designs, certainly looks promising.
OR; fast breeder reactors will continue to be used for plutonium production for the bombs that the Us aren;t still building, honest (because after all, that's what they're designed for), and the wastes from those could go into feeding these things, rather than having scores of massive radioactive ponds lying around the place holding all the high-level waste?
The UK's government has been wasting huge amounts of money for decades trying to make a waste reprocessing power plant or a useable fuel from the crap they already have and are still producing. If this is a legitimate and proven design of reactor they will jump at the chance.
Daily Mail readers have had Nuclear Power Stations inefficiently powering their well lit homes for decades, they won't stand in the way of a cheaper more efficient method, but the Flat-Earthers might.....
Paris, because she thinks she's atomic but she's just a waste too.
If this is a legitimate and proven design of reactor they
will should jump at the chance.
Fixed it for you.
(Sorry, I'm just too bloody cynical I know, but I doubt that there is a single current MP with the ability to think further than the week)
Germany has a carbon footprint of about 10 tonnes per person per year despite (or possibly because of) their dash for renewables backed by burning fossil carbon in the form of Russian natural gas as well as the hundreds of millions of tonnes of lignite and hard coal they burn each year to keep the lights on. France which generates 80% of its electricity from nuclear power stations has a carbon footprint of 5 tonnes per person per year, and has done so for about thirty years now since most of their reactor fleet came on stream in the mid-80s.
Search for Thorium Remix on YouTube and watch/listen to some of Kirk Sorenson's lectures on Thorium (LFTR) reactors for an excellent overview on the technology. This group from MIT seems to have seen these videos and are slanting the description of their process to feature the waste disposal aspects. This isn't brand new technology just coming out. The US government did a fair amount of research decades ago on this technology and even built some prototype reactors that rans for several years very reliably to verify some of the research. The Chinese learned of this design and the US happily handed them a copy of all the documentation. They will have a test reactor running by 2015 by some reports and perhaps as early as this year (2013) by others. If they file patents on the technology they develop along the way, other countries will have to pay homage (loads of cash) to build similar reactors or may have to purchase the hardware from Chinese manufacturers and then pay a royalty per megawatt.
Some assert that the US dropped the development of LFTR reactors as they do not produce nuclear material usable in weapons and instead put money into Fast Breeder reactors that did. There are now a couple of Fast Breeder reactors in the US that failed and are sealed off until the far future or until somebody can figure out a way to clean them up. This is news that doesn't get mentioned and one has to dig to find it.
The statement in the article that asserts that the manufacture of fuel for the current reactors is related to proliferation of weapons grade material is misleading. Reprocessing spent fuel can separate out materials that could be used in weapons with further processing, but the manufacture of fuel rods from new material does not.
Wrong. The reactor waste is just a part of the story. For each ton of fuel, about 20 tons of depleted uranium is produced, that could be used in breeders, including liquid-salt reactors. These tailings amount to millions of tons, enough to last for centuries. So there would be no need to mine a single ton of uranium before the fusion inevitably takes over.
But as someone who's actually worked on designing, building and operating nuclear plant (Heysham II, Torness and a dabble in Sizewell B), there's more than a touch of naievity (sp?) in both the engineering and the assumptions about how it could be brought to market. Plus a sonething that looks like some sleight of hand about fuel and waste cycles.
So, in no particular order.
First, MSRs can indeed in theory, be simple beasts, at least in terms of the reactor itself. However, what's usually omitted by the proponents are the issues associated with anciliary plant. An MSR basically demands that you reprocess in "real time" - typically, the entire fuel load has to pass through plant removing fission products and fuel precursors every 2-4 weeks. In the case of some products, that's relatively simple - xenons and iodines can be got out by spraying the fuel salt through an inert-gas chamber. Others - the less volatile medium weight fission products like strontiums and caesiums will need something like vacccum distillation. The most challenging is removing the protactinium fuel precursor (the cycle runs 232Th + n -> 233 Pa - e -> 233U). If not removed, the protactinium captures extra neutrons, needing to capture 2 in order to transmute to 235U. The protactinium has a big capture cross section, and if left in will badly reduce neutron economy, so it has to come out, both for the sake of breeding and basic operation. It's a bugger to remove - the most viable method involves bubbling fuel salt through a column of liquid bismuth.
All of which would be fine - but your working fluid is a highly radioactive molten halide salt at 500-600C. And the plant has to operate at pretty much the same levels of availability as the reactor itsself. designing and operting plant to acheive that is extremely hard - probably harder than desinging the reactor itself.
And don't be fooled by the fact that the fission products are removed from the reactor means that they're not a management challenge. Inventories of Xenons and iodines will be higher than a conventional plant - in conventional plant, they're transmuted away by neutron capture - in this, they're separated, and will have to be isolated, stored and cooled, alongside the other fission products. True, it's a lot smaller than the volume in a cnvetional spent fuel pool - but much hotter!
There are other issues, too. Keeping a graphite core in useable condition in the core of an AGR is a sod of a job - it suffers radiolytic corrosion, and tends to distort under high neutron fluxes (not good, as in extreme circumstances it cound cause control rods to jam). We ended up having to manage flux very actively, and to dope the CO2 coolant with methane to get 30-40 year design life. What this things core graphite will be like, with higher flux levels, and an inherently aggressive coolant/fuel medium doesn't look to be likely to have a long life - I'd guess 10-20 years.
On the fuel cycle, the advocates pull a small trick, in that they compare "once through" LWR cycles with a cycle that entails inherent reprocessing. A more appropriate comparator is something like the IFR/PRISM proposal - which has an on-site pyrolytic reprocessing cycle using mixed actinide metal fuel. The harder neutron flux (i.e. faster) is much better at removing transuranics than MSR's themal spectrum, and is at least as proliferation resistant, and fuel effficient.
Perhaps you might like to look at this
It describes in some detail an outline for a 1000MW(e) MSR including the real time chemical plant.
The real time chem plant is estimated at (roughly) a 15 foot high tower 4 feet in diameter (including the protactinium separator). It would therefor be feasible to build a redundant pair on site fairly easily. This is small by the standards of the bulk chemicals industry (or some branches of the fine chemicals industry).
"And don't be fooled by the fact that the fission products are removed from the reactor means that they're not a management challenge....True, it's a lot smaller than the volume in a cnvetional spent fuel pool - but much hotter!" If you mean temperature then it will cool much faster. If you mean radioactive IIRC their half lives are pretty short.
"All of which would be fine - but your working fluid is a highly radioactive molten halide salt at 500-600C. And the plant has to operate at pretty much the same levels of availability as the reactor itsself. designing and operating plant to achieve that is extremely hard - probably harder than desinging the reactor itself."
The design of equipment using molten salt is specialized but not uncommon. Aluminium separation cells use Floride salts and certain large electroplating cells also use molten salts.
"keeping a graphite core in useable condition in the core of an AGR is a sod of a job -" But this system is not gas cooled. I wonder if the high gas speed might have also been an issue? Neat trick with the Methane gas pyrolytic deposition BTW. I've heard of it on bench top rigs but not on a whole pile.
"What this things core graphite will be like, " Because the fuel is a liquid the moderator elements are much simpler (essentially rectangular pillars in the referenced report outline). Testing should be much simpler. There is also the point that not being intricately machined interlocking blocks they could be replaced by remote handling equipment (It may run hot in both senses of the word but an MSR is relatively low pressure) inserted through the ceiling. The massive improvement in computing resources available since the 1970s should make modelling core reactivity a much more accurate process than it was.
As for comparison well all working US reactors (AFAIK) are LWR, either pressurized or boiling water. They are therefor a known quantity.
The real problem is that companies in this business make money selling the nuclear fuel elements and as I have jokingly suggested in the past these reactors reduce the fueling problem to using a shovel.
I've been seeing stuff like that for a good few years, John Smith, and as I said, it's more than a touch naive - and given that we're talking of at least three or four entirely separate physical processes (a spay/sparge for volatiles, vaccum distillation for medium-weight semi volatives, pyrolitics or similar for actinides, and a protactinium extraction process), I think someone's indulging in wishful thinking, if they think a single compact plant will do it.
We've then got minor issues like high-integrity, actively cooled shielded storage for the first two (and probably the space where the protactinium will have to dwell for a couple of years while it undergoes decay to 233U).
And no, simple redundancy won't do it - we're talking highly integrated plant that will be working in direct contact with a medium that's not only laced with fission products, but is in intimate contact with neutron emitters. It'll therefore be subject to significant activation. That's going to mean maintenance access will be essentially zero, unless you allow significant periods to allow activity to decay, before attempting access; which in it's turn means you're not talking about simple duplicate or triplicate redundancy, but manifold. If yuo've ever seen the maintenance access problems on plants like those at Sellafield - which only handle fuel, recall, after a decade or two of decay time, where as this is needing to cycle through the entire fuel load every month or so - you'd not dismiss this quite so casually.
"The design of equipment using molten salt is specialized but not uncommon. ",
However, not at nuclear standards or integrity/reliability. And not dealing with activated products in real time.
"Because the fuel is a liquid the moderator elements are much simpler (essentially rectangular pillars in the referenced report outline)."
To put it delicately - balls. The AGR moderator "bricks" were not notably complex in shape (basically octagonal section blocks with keyways for jointing.. And no, they weren't subject to direct loading from high velocity gas - each fuel channel had an inner liner, and the fuel stringers sit in their own sleeve. Geometry wasn't especially the issue - the reason they tended to distort was that partly there is obviously a neutron flux gradient across the brick. Now, if you think of the scale of an AGR core, and the scale of an MSR core - the latter being very much smaller - I'd reasonably expect gradients to be steeper in a smaller core.
And, I don't see concepts of in-situ replacement being even mildly credible - not after direct contact with fission-product bearing fuel salt. There were some thoughts given to trying that on AGRs in a depressurised state (and they don't have anything like the direct contamination issues) but it was quickly kyboshed as infeasible.
Interesting arguments on both sides.
It reminds me of jet engine development. The idea as sound in the 20's, but materials and machining accuracy meant it had to wait 15 years to get anywhere near working.
I think we need to ask..
1/. Is it theoretically feasible? The answer is probably yes.
2/. If it was feasible, would it be worth doing? Here its less clear, If it were massively expensive with no hope of getting cheaper, probably not.
3/. What are the key engineering challenges to achieving a working prototype? Here it would seem that the reactor itself is the easy bit, stripping crud out of the salt is the harder part. Well that was similar to the problem of refining uranium in the Manhattan project: istopic separation was a bitch - and it still is, and that is one reason why as soon as you have enough to breed plutonium, that's what you do to make firecrackers..
At this point you have - as with most 'great ides' a devil in the detail you have to look at long and hard, and especially in terms of the alternatives. WE do have ABWRs and PWRs that are perfectly capable of safe operation right now and which can and will use Plutonium MOX fuel. So there is no desperate rush to have waste burners and breeders yet. And there are other ways to burn waste as well. IIRC there is the Prism and another design around. And today we have heavy duty particle accelerators and lasers which can act as 'ignition' devices for otherwise sub critical piles of radioactive crud.
The real breakthrough we need is to get public perception of nuclear power on a new footing. Wade Allison is ploughing a lonely furrow there..
Once people realise that nuclear power is not the worst, but actually one of the best alternatives to fossil fuel, at least in electrical energy generation, spending dosh carefully on little projects to try out various technologies ,is a given.
I welcome this article, if for no more than the publicity.
There's a variation on
"2/. If it was feasible, would it be worth doing? Here its less clear, If it were massively expensive with no hope of getting cheaper, probably not."
that you need to add in - are there alternative technologies that do the same job better/cheaper.
"I've been seeing stuff like that for a good few years, John Smith, and as I said, it's more than a touch naive "
I cannot comment on the MIT groups work as I've not found enough details about it. However the report I referenced
Was prepared for Union Carbide Nuclear (the contractor who was running Oak Ridge National Laboratory in the early 1970s) by a group of relevant companies.
Ebasco Nuclear core design. Babcock & Wilcox Containment, heat exchangers, steam generators. Continental Oil. Chemical processing. Union Carbide Graphite tech. Cabot Corp Hastelloy N (radiation resistant superalloy grade) Byron Jackson Fused salt pumps.
I would not describe such a group as naive. I would say on the whole they were technically conservative. For example they were doubtful on the ability to seal large pieces of graphite from Xenon intrusion (which your mention of in situ grapite deposition suggests is no longer a problem). I think the SoP in pieces of high grade graphite has also improved considerably since then.
The chemical plant is described starting at page 169 of the document. Building a demo plant in the UK (which I suspect has never been done) sounds like a pretty good end of degree class project for Nuclear or Chemical Engineering.
Sounds very similar in principle to Thorium reactors, which are also molten salt reactors, use a frozen salt plug, and are walk-away safe. The main difference here seems to be that this design can take 'spent' nuclear waste and use it as fuel, which is a great idea.
If anyone is so inclined, there is a fantastic lecture on 'the Tube' about Thorium reactors, and why they are so great. Here's the link:
It's worth sticking with all the way through, if you can.
One may be wondering, "if Thorium is so great, why aren't we using Thorium reactors now?". The simple answer is, Governments want nuclear power plants not for the electricity, which is a useful by-product, but for the "waste" products, which are used in nuclear weapons.
To be fair, that's not so much the case any more, but it *definately* was in the 50's. Windscale was built for the express purpose of fueling the UKs nuclear weapons race with America. Surely the 'race' was with Russia, you say? No. It was with America. That Windscale produced electricity was simply a means of selling it to the public, and justification for the expenditure using tax-payers money.
All went swimmingly. Until it melted down! (Which was human error, shaving down the cores to make them thinner, so that they got hotter, and produced a stronger reaction. Un-seen hot-spots in the reactor caused them to melt.
http://www.youtube.com/watch?v=vZ4vtUzG6sQ (please forgive the scaremongering title, I picked this particular version on YT since the documentary is presented in a single 1:27:00 long video).
Windscale is now known as Sellafield.
A good weekend to all.
The "salt plug" is a useful eature - but people rather miss the point.
The salt plug prevents an ongoing nuclear reaction, by draining the fuel below the moderator, thus making the whole system sub critical.
But that's hardly a unique feature to the MSR, and nor does it remove the key issue in safety - which is removal of decay heat. Note that at Fukushima, in all cases the main chain reaction stopped - it had to as coolant/moderator was boiled out of the core. And in IFR designs, a mixture of doppler broadening and spatial effects also stops reactions as temperatures rise.
Even once the fuel is drained down, it's still necessary to remove decay heat (typically about 7% of full power at the point of shutdown, decaying down to 2-3% within a day. For a 500MWe reactor, that still means you're removing 20MW or so.
In some ways, the MSR makes that problem easier, in others harder. The fission product burden in the fuel salt is lower - because of the "real-time" reprocessing required to make the design work. But the total fission product burden is higher - the xenons and iodines aren't removed by neutron capture - and those and other fission products (roughly the same in quantity) still have to be isolated and cooled. Arguably, that's harder, as concentrating those products means that the cooling needs to be more aggressive (and reliable). Worse, since different products are isolated in different streams, the number of cooling systems proliferates, and reliability engineering 101 tells you that's a bigger challenge, not a lesser.
By th way, if anything 233U is a better bomb material that 239Pu. The claimed MSR advantage is that it's mixed with 232U, which is strngly radioactive - but then, so is 240Pu, which is inherent mixed into reactor grade plutonium. Making a bomb from either is much the same scale of technical challenge.
Not much information available (yet). They (CEO) are guessing 2 years to get benchtop data, 5-8 years to get through to prototype stage.
ThoriumMSR has a URL on this http://thoriummsr.com/q-and-a-with-russell-wilcox-of-transatomic-power/
I would guess the 3% efficiency number presented, is the typical efficiency of USA light water designs.
This design is expected to work with thorium or uranium, but will start with uranium. While the design produces much less waste (they think), it is not likely to be qualified to burn existing waste. So, we still need to deal with that, for probably at least another 20 years.
Another thread mentions that nitrate salts break down at 565 C, and the above thread says the reactor will like operate at 700C. So, it isn't likely to be nitrate salts. A question in the above thread had an answer that it isn't likely to be chloride salts. Another question about fuel, is that for new uranium fuel, the input is likely to be gaseous UF6, which suggests to me they are talking fluoride salts.
They aren't willing to say if this is thermal, fast or something else.
Someone in a thread somewhere, mentioned lithium. I'm not a big believer in lithium or beryllium, as they both undergo fission of a sort. Be-9 can absorb a gamma over 1.6 MeV, emit a photoneutron, and then decay into 2 He-4 nuclei, which looks a lot like fission. Li-6 can absorb a neutron and essentially split into H-3 and He-4. Li-7 doesn't have a big absorption cross section, but Li-8 beta decays to Be-8 with a short half life, and we get those 2 He-4 particles again (another essentially fission reaction).
They are calling it intrinsically safe, and yet it is supposed to have a graphite core. Graphite can store energy when used as a moderator, and annealing the graphite to release this energy becomes part of reactor operation. And the release of that energy in a large mass of graphite, can be a problem.
If they use uranium fuel, they will breed all the transuranics that uranium fueled reactors normally breed. That they think they can burn most of them away is useful. The problem with a lot of thorium fueled designs, is that 28 day Pa-233. If the fuel stays in the core, the Pa-233 has a big enough cross section for neutrons, that you make Pa-234, which provides access to all the transuranic production of uranium fueled reactors.
If this reactor can safely burn up transuranics and fission products, I would hope that they consider one (or a few) channels through the core of a refractory material, through which they can insert/circulate existing used fuel. It is not enough to just not generate more waste, we need a way to get rid of the existing waste.
And they might as well stick to uranium, until someone finds the magic to get most of the Th-232 to transform to U-233 correct.
"They aren't willing to say if this is thermal, fast or something else."
well, if it's not thermal, there's a very good question as to why there's a large chunk of graphite in there.....
And the graphite energy storage issue (Wigner energy) isn't an issue if the reactor works at about about 300C
"And the graphite energy storage issue (Wigner energy) isn't an issue if the reactor works at about about 300C"
So that should not be a problem.
On a side note Wigner energy (and the way it can be released) is a fascinating process. IIRC it allows the storage of fairly large amounts of heat energy in an inert solid that will not release it until raised above a threshold temperature and the heat is a relaxation effect, without any form of combustion.
My impression was the more perfect the solid the more heat you could store/release, making single crystal Silicon the ideal starting candidate.
I think you're misunderstanding where Wigner energy comes from. It's not heat storage per se - at least the input energy isn't heat, albeit it manifests itself as heat on release.
It's actually energy that's arisen from neutron collisions with the carbon atoms of the graphite crystalline matrix - basically, atoms that have been "knocked out of place" and have re-bonded in distorted patterns. That being the "annealing" point - it's when temperatures rise high enough that those distorted bonds are broken, and the matrix "snaps back" into it's lowest energy alignment state.
SO, unless, you happen to have an intense neutron source to hand, and a material that allows various forms of cross-bonding, wigner ain't going to happen.....
"I think you're misunderstanding where Wigner energy comes from."
I'm not. Technically it's strain energy. I've had to break pieces of wire by repeatedly flexing them. With stiff coat hanger wire the heat nearly burnt my hands. Hence my comment about "relaxation."
My instinct was that the more perfect the atomic structure the more energy could be stored by the neutron induced distortions, hence my remark about single crystal Silicon.
The US Oak Ridge National Laboratory ran one of these reactors for some years back in the 60s (a small one) but it was killed of by Washington, possibly at the behest of the vested interest of the solid nuclear fuel producers (what industry would choose to allow their customers to reduce their consumption by say 95%?)
A few years ago I started an no10 ePartition asking for the UK to research this, can't remember how many votes it got, few 100 I think.
There some technical issues to solve but the safety and environmental advantages are enourmous
Congrats to this lot for getting some publicity and hope it gets somewhere but expect the same vested interests to kill it. :-(
Sadly the world is ruled by greedy rich people and stupid politicians .
>>The initial design for WAMSR is a 500MWe (megawatt electrical) plant that can be manufactured as a standalone unit and be shipped directly to customers, ready to be fueled up and switched on. It would cost around $1.5bn
Crowdsource, anyone? I'll happily accommodate it in my backyard, for an appropriate percentage...
It might take something more than a Kickstarter level of funding to really get this going. Check out Flibe Energy's website. I would be more than happy to contribute some engineering to the project without cost. I could even be persuaded to work for equity rather than a paycheck as a part time job.
Existing companies in the nuclear business make their money selling fuel elements , not reactors.
It's like Gillette with disposable head razors or the gun business with bullets, or even perhaps the printer business with cartridges.
A solution which eliminates the consumables is not in their interests.
There is very little detail on the concept or their Special Sauce (C Lewis Page) but I will wish them well.
how long have you got....?
basically, it's the same as any other reactor - neutrons arise from fission events, then get absorbed into other fissionable nuclei, which fission and produce more neutrons than they absorb - the idea being you balance the production of neutrons, their absorbtion into fissionable nuclei and other parasitic materials, and losses by leakage out of the core.
The graphite is there because uranium nuclei are more prone to absorbing neutrons moving at around 2200m/s (thermal energies) than they are ones that have just been produced from fission at much higher speeds ("fast" energies). The neutrons bounce around hitting carbon atoms in the graphite (which doesn't absorb them) losing a bit of speed with each collision until they've slowed to thermal levels f energy, and will then tend to be absorbed and cause fission.
The problem is we lack an efficient industrial-scale way to convert thermal energy directly into electricity. The steam turbine process is three-step (heat->chemical->mechanical->electrical), but in the hundred-plus years since then we've yet to produce anything better. The closest we've gotten at this point IIRC is the Seeback thermoelectric engine, but it's less efficient and more expensive at scale than the turbine process and has issues of its own.
It seems similar to the Dunning Kruger effect, the less someone knows about something the more they underestimate its difficulty.
I'd trust Andydaws opinion more than the "how hard can it be!" brigade.
But a cheap, simple, efficient, reliable and safe power generation system would be really nice.
Ain't that the truth. Its possible engineering wise to prove that renewable energy is a waste of time in the UK* at least.
But most people confronted with the arguments and maths just glaze over and say 'well that's just YOUR OPINION.'
Oner wonders what the point of doing all those years at college actually was, if its just to be thrown back at you as an 'opinion' by some person who knows what they want to believe, and that's that.
Why bother designing an MSR from scratch when there are IFR-style reactors in operation since 1974?
Starting with 150 MWe BN-350 in 1974, 560MWe BN-600 operating since 1980, BN-800 nearing completion and BN-1200 under development.
I am sorry to hear that you have been disappointed by some of your previous contacts with most people. As a person myself, let me try to help, if I can. You can help me by correcting my misunderstandings too.
You start well by qualifying your strong assertion "engineering wise", yet you don't hold back with your punch line "a waste of time". In my experience most people tend to hear the conclusion more forcefully than the caveats. Especially when similar language might have hurt them in their own lives. Suggested wording: "not cost-justified given present pricing of externalities". But, what is that you say: "engineers are trained to design closed systems, and externalities are zero, engineering-wise"? And there is your other problem. You hear harsh words of rejection (see above) but draw the wrong conclusions. I speculate that most people might reckon 'engineering-wise' is necessary but not sufficient to decide how to proceed with systems that are unbounded or, put another that they are part of and cannot escape from. Suggested action: take it back on yourself. Most people are generally right. (Though paradoxically nearly every individual is an idiot in their own way). Help us to become even more right by giving your valuable wisdom, while not assuming our general ignorance.
(1) Much as I love this idea, and hope it is true and turns out to be practical - I REALLY REALLY HATE the prospect that the bloody economists will turn out to have been right when they waved their arms and said, "Oh, the engineers will come up with something. They always have before".
(2) Isn't it a sobering thought that, in 60 years, the best scientists and engineers in the world never came up with this (fairly simple) design before? Indeed, as has been explained, almost all of the design was invented a lifetime ago, but no one even tried to work out a way of using "waste" as fuel.
It seems we have, as a trump card, some very clever and creative people. But the way we are organized - and led by political hacks, businessman, banksters, etc. - hamstrings them almost to the point of uselessness. Thank God those two young postgrads got the time, funding, and opportunity to do their work. If it pans out, we owe them more than pretty well anyone else I can think of.
so were the breeder reactors and they died a slow death due to technical complications and cost. To contain a very hot and radioactive molten salt and to organize a reliable heat exchange with said molten salt might be a challenge. To keep the reaction mixture just right will be another.
Let's hope that it's more than a nice concept on paper.
I've been saying for years that if you give me a better alternative for dealing with nuclear waste that's going to be around for several hundred thousand years than burying it then I would get behind nuclear power. Looks like it's finally happened. Sure there's still waste, but much less waste that's dangerous for less than 1000 years is something that can be dealt with.
Not gonna junk any laws, but what about a proper Stirling solution instead.
And those of you who think they are unpractical toys, think again. Swedish submarine more or less sinking the fleet of great US, while training. Is powered by two sterling engines, while in silent mode.
Some of the successful Stirling engine manufacturers have mystically been bought up of energy companies. I investigated it due to a friend of mine is in the heat business, was wondering of how they could produce some electricity of the little waste heat they have.
Turns out a bigger, but similar company in Denmark has done just that, with their own designed sterling engine.
I would say that is better than steam engine. But principally pretty much the same.
The efficiency of a Stirling engine is still limited by the good old issue of peak temp relative to the temperature at which heat is rejected to ambient. THats fundamental/inherent.
IMO, stirling engines do have their place - but in those applications where the available heat source is comparatively low temperature. However, they don't as a rule look economically attractive when higher temperatures are available - or at larger scales.
I'd not sure you'd be about to convince me that we're about to see gigawatt-rated stirling units - afer all, reciprocating units really don't look good in any form in the megwatt and higher range.
NASA, or rather Boeing/Teledyne is going to a type of Stirling engine to replace conventional RadioIsotopic Thermal Generators (RTG's) on deep space vehicles. Maybe it will be possible to apply a similar technology to LFTR reactors, but turbine systems are the most efficient means of converting heat energy to mechanical energy. I believe that the designs I have seen thus far for the LFTR reactors use Helium or another gas as the primary working fluid rather than steam.
Consider that the auxiliary containment vault just happens to be half-full of water, either due to unimaginative design combined with years of neglect, or - for example - a tsunami has just flooded it on a day that's just one damn thing after another. Then the freeze plug melts (for whatever reason, perhaps related to the earthquake) and the molten and radioactive salt starts pouring into the underground vault half-full of water. This will result in a steam explosion of biblical proportions, scattering highly radioactive waste and contaminated steam out into the local area and beyond.
Next up for the failure mode lust is the usual failure of the heat exchanger. Leading to a radioactive mess plugging up the turbine. Costing billions.
Calling this conceptual design "fail safe" is not a good start.
Yeah, years of neglect on a primary safety feature of a nuclear power plant. Like we have seen happening entirely too many times already. And it's not like there was any water in Fukushima containment vessels when their cores spilled down there.
Failure of heat exchanger = over-threshold temperature of the salt = plug melts due to cooling system being designed to keep it from melting only up to the threshold salt temperature. That's even if it fails to shut down before that.
Also, plugging exactly which turbine?
Anyway, this "company spin-off of MIT" claiming "cracking a holy grail" which was cracked already in 1960s. Phew. I suspect it's just attempts to not miss the bandwagon and maybe bite off some market share before first BN series come online in China and Japanese get their derivative going.
Actually, there was water in the the lower parts of the Fukushima containments ("PCVS"s) if/when fuel exited the RPVs.
Before I go into that, just one point. There's a general assumption that fuel "melted through" the RPV bottom heads - however, what's emerging as instrumentation's introduced into the PCV's doesn't actually support that, or the idea that the PCVs are damaged to anything like the degree assumed.
On the first point, the most striking part is that in October last year, TEPCO introduced a radiation detector into the R1 PCV (R1 is generally assumed to be the worst damaged). They plotted radiation levels at various heights above the water level in the bottom of the PCV.
If the fuel had exited the RPV, the radiation levels should rise as you get closer to the base of the PCV - obviously, since the fuel would be the main source, and if the fuel was in large measure at the bottom of the PCV (even if part penetrating it) it'd be hottest nearest to the fuel.
In fact, that wasn't the case. Radiation levels were highest roughly on a level with the bottom of the RPV. Levels fell as the detector was moved lower into the PCV. It was LOWEST at the surface of the water pool in the bottom of the PCV.
The only sensible interpretation of that is that at very least the overwhelming majority of the fuel is in the RPV bottom head. But that's to be confirmed....
It was also interesting that the isotopic composition of the water in the bottom of the PCV was markedly different from that in the reactor basements - suggesting that the flow-path isn't RPV -> PCV -> basement.
Back to the water.....it's true the drywell wouldn't normally have water in it - but there was serious overpressurisation during the accident which would have buggered lots of seals, and have water flowing anyhow. There was also an issue that the suppression torus became overfilled, probably to a degree there'd have been back-flow into the drywell
One other oddment. There's now been a pretty comprehensive survey of the suppression torus of R2, - the one that was supposed have been damaged by a hydrogen explosion.
gives you the inspection summary.
It's been focussed on the vent pipes that connect the torus to the drywell. These have a large steel bellows arrangement to accomodate thermal movement, and are the weakest part of the overall system. They also have carious rubber and metal seals.
The striking thing is, five out of six have been inspected (by robotic camera), and so far, none has shown evidence of leakage.
This is the radiation survey I mentioned above:
And this is the water sampling exercise.
Note how different it is to the water in the turbine building - LOWER levels of radioactivity, and lower salinity. It suggests that even in the early stages of the accident, when seawater was being used to col the reactor, water wasn't tending to flow from the RPV to the PCV.
That suggests a number of things - one of which is that the flow path for the water that's now being used to ccool the fuel is bypassing the PCV, and going into the reactor basement directly - probably through failed seals on something like the recirculation system, parts of which sit outside the PCV.
And that's NOT compatible with the idea that the bottom end of the RPV is grossly damaged. Or that PCV integrity is particularly bad - both of which should make fuel removal much easier.
Well, in molten salt or liquid metal-cooled reactors the danger of said fuel/coolant flash-boiling (thus the overpressure catastrophically damaging the containment vessel) on thermal sink failure is minimal compared to BWR or PWR types.
I can't say how exactly BN-800 is designed, but I'm pretty certain it's nothing like VVER-1000.
"I can't say how exactly BN-800 is designed, but I'm pretty certain it's nothing like VVER-1000"
It's certainly not anything like VVER-1000. It's a sodium cooled fast design, VVER is the Russian for Vodo-Vodyanoi Energetichesky Reactor, which translates as Water (cooled), Water (moderated) Power Producing Reactor.
I have a couple of issues with the article itself:
"As a side benefit, this could also reduce nuclear proliferation since countries would no longer have to
manufacturer nuclear fuel."
Well, it would remove the *excuse* of generating power from the nuclear proliferation problem, but since places like America have had plenty of options when it comes to development of nuclear power, and have instead opted for sources of power that also, just coincidentally *happens* to produce nuclear weapons, I would say that it's all a load of bollocks. Iran for example, could just as easily go the Thorium route like India has, but that's not what they *want*. They *want* an excuse to pretend to make electricity while actually making bombs.
"It would cost around $1.5bn – which may sound like a lot, but is dirt cheap compared to a garden-varity nuke plant these days."
A garden variety nuke plant also costs way less than they actually do, but when you have to go crazy on safety and insurance, costs spiral out of control. I'll believe them about costs when they start delivering plants in the real world, on time and on budget. We've all heard this line before. It also might be a reason they're looking to China for customers - when you don't have to worry about insurance claims from a population that has no legal recourse when it comes to What Happens When The State Fucks Everyone Hardcore, then things get stunningly cheap.
"when you don't have to worry about insurance claims from a population that has no legal recourse when it comes to What Happens When The State Fucks Everyone Hardcore, then things get stunningly cheap."
...unfortunately, that may be a bad thing in the long term: If the same guys design the nuke plants who design their car safety structures and formulate their baby food, they'll eliminate the salt plug to save 5000 Yuan, the thing will blow sky-high, and everyone in the rest of the world will throw out all nuclear power forever in a blind panic.
@Andydaws and others?
My experience with nukes is a smal onel, a SLOWPOKE. But, one of the things I've spent a little time thinking about, is how one might build a reactor someplace where there LOTS of real estate and no problems with water or neighbours (who don't want a nuke in their backyard). The Moon. If a person made a lot of "pebbles" with thorium in them, and only had a fraction of them in the core at any given time, the rest of the time they are in a disadvantageous geometry, allowing the Th-233/Pa-233/U-233 to run to somewhat to completion. Something like 9 hours in core, and 45 days out of core, before the cycle repeats. Any opinion as to whether that makes the thermal breeder for Th/U-233 work?
The obvious comment would be - how would you transmit the power back to where it's needed, i.e. here?
You do raise some interesting points, though. But first, once small correction. The in core time for every Pebble bed design I've seen is in weeks or months (you'd need significant dwell time to get useful levels of transmutation). What you wouldn't want is the sort of dwell time for fuel needed for LWRs - 18 months to 2 years.
As to the dwell time outside the reactor for 233Pa to decay to 233U, 45 days would be insufficient. Taking the old "ten half lives for 99.9% decay" rule, from memory the 233Pa half life is about 30 days - so, something in the order of 200-300 days to get reasonably pure 233U.
There's an additional aspect to this, which is to do with the nature of the fuel for pebble bed reators and its associated economics. The outer layers of PBR fuel is an extremely tough carbide ceramic (and the fuel inside is granules of uranium carbide in a carbon matrix). It's basically reprocessing-proof.
Which means if you don't have some fertile material in there, and sufficient enrichment that the fuel can carry a large burden of accumulated poisons, you can only use it on a once-through cycle and a burn-up to perhaps 50-60MWd/tonne.. That's probably acceptable at the moment, when uranium prices are low, but were they to rise significantly, or other technologies to establish better economy (IFR can easily run to an equivalent of 3000MWd/tonne).
So, if we're going to see commercial deployment of pebble bed designs, they'd almost certainly have to have soemthing of what you suggest - "seeding" with thorium alongside high uranium enrichment, and also loading the fuel with burnable poisons to supress reactivity in the earlier parts of the cycle.
BTW, there's another challenge on operating any reasonably conventional power source on the moon - any guesses what it might be?
I'm thinking of the situation where industry on the Moon is developing, and power is needed on the Moon. Yes, solar power is available. But, having a backup (gee, that last asteroid wiped out the transmission line) is useful. And being thermal, waste heat could be useful.
The idea of 9 hours, is to operate in circumstances where Xe-135 is less than equilibrium. No sense having a parasitic neutron reaction if you can avoid it. A person has to have too much fuel inventory to have 300 days out of core, but there is almost infinite real estate up there.
I know pebble designs on earth involve carbides and pyrolitic carbon, and carbon is in short supply on the Moon. Some other kind of pebble system would be needed. There is some deuterium in the solar wind, and many people have written about He-3 in the regolith. Is there enough deuterium in the regolith to make heavy water for a thermal reactor? Once you have a reactor, some neutrons will be absorbed by light hydrogen to make deuterium (and some absorbed by deuterium to make tritium).
On the Moon, access is less of a problem than here. It is also a much different kind of access. Political input to pebble design will be different.
I suspect you are talking about getting rid of waste heat in terms of a challenge. The same challenge is present just for mining. You need engines to run drills, dozers, .... They all make waste heat, but are smaller in scale.
Pumping waste heat into the ground might work, if you can find processes that can use that for a heat source.
The Three Mile Island and the Fukushima reactor explosions were not due to "flash-boiling" overpressure they were due to a high-temperature catalytic reaction involving the fuel rod cladding material, zirconium decomposing steam into hydrogen and oxygen which then recombined violently. Flash-boiling happens all the time in Boiling Water Reactors (BWRs) where water flashes into steam as it is sprayed onto hot fuel rods inside the reactor vessel.
there was no explosion at TMI.
There was some panic at the time (including Jimmy Carter), because there was hydrogen generation inside the RPV, from the reaction between hot zirconium and steam. It's not catalytic, though, it's a prefectly ordinary oxidation of the zirconium and H20, as below
Zn + H2O -> ZnO +H2
Which should give you a clue as to why there was no possibility of an explosion inside the RPV - there was no free oxygen with which the H2 could combust.
At Fukushima, the H2 was vented into the reactor buildings (instead of what should have been done, which was to vent it through the filtered exhaust staccks to atmosphere - mostly becuase Naoto Kan, the Japanese PM over-ruled the site engineers who'd wished to start venting early in the process - Kan banned it until he'd been able to hold a press conference!).
Obviously, O2 was available in the reactor buildings. BWRs run with an inerted atmosphere inside the primary containment, but not the secondary containment/reactor building. PWRs are built differently - the primary containment is much larger (pretty much equivalent to the BWR reactor building), and it's now usual practice to run with an inerted atmosphere except when personnel access is needed.
And no, water's not "sprayed" into BWRs in normal operation. Primary circuit water comes back to the RPV from the turbine condensor, enters as a flow on the outside of the "shroud", flows down outside the auunulus formed between the shroud and RPV wall to the bottom head, where it turns and flows up (as bulk liquid) through the core. The rate of flow, and the resultant height of the water column is used as a means of controlling reactivity. As it flows up through the core it boils in a perfectly normal nucleate boiling process, such that there's an increasing void component as you move up through the core.
"Flash Boiling" is a bit of a myth. Provided the water's able to wet the fuel surface, there's usually good heat transffer and there's no excessive pressure generation. What is a problem is a phenomenon called "film boiling", when a layer of steam gets form on the outside of the fuel, preventing wetting, and reducing heat transfer. It's a very transient issue - any roughness at all on the fuel can surface, or turbulence in the rising stream and the film collapses in milliseconds.
While zirconium has some wonderful nuclear properties, it has some annoying chemical properties.
If a nuclear accident results in molten zirconium, and some processes have reduced the oxygen content in containment, we still have another potential problem. Zirconium (titanium and hafnium, and some other metals) are all more than happy to undergo combustion by nitrogen. The lack of available oxygen does not necessarily indicate a lack of chemical heat generation potential with zirconium. On Earth, we have lots of nitrogen, on the Moon, it is rare.
"It's also "walk-away safe," the designers claim, making it immune to the kind of meltdown that destroyed the Fukushima reactors." The designers, graduate students, should get their designs checked out by experienced grey-haired engineers who know that ANYTHING can go wrong, and EVERYTHING will go wrong sometime.
Just because you can't imagine something going wrong doesn't mean the design is infallible. The name "Titanic" springs to mind.
Except they didn't -say- it was infallible, did they? They said it wasn't subject to the same type of failure as Fukushima. Unless your argument is that they need to have contingencies for the reactor becoming sentient, going rogue a la glados, and rebuilding itself to require diesel generators, you should start getting your posts checked by experienced grey-haired editors who understand the article you're reading...
As a number of the posts have pointed out this story does not represent a set of radical new ideas. It is instead an attempt at re-booting long standing concepts for the development of purely civil nuclear technologies. This is part of the problem; without a well funded government program to back the development of the early concept work this is unlikely to take off. The bits of government that excel at getting large technical development projects of the ground is the military and they have no interest in funding this type of initiative.
The big nuclear suppliers have invested huge amounts in designs that are evolutions of earlier nuclear reactors. For example, EDF have invested circa 700 million euros into their latest nuclear reactor design. They won't want to write of that sort of investment just because better alternatives exist. The nuclear industry is also comprised of a work force that has invested huge amounts of time and effort understanding current and legacy designs. Given those investments by a heavily trained workforce and the costs of designs of nuclear power station designs there is a natural inertia against change (especially radical change).
I have thought about this in the past and have considered setting up a charitable trust to fund PhDs that focus on new approaches in nuclear technology. With a view that today's bright PhD student in 20 or 30 years will be a senior engineer or designer in the nuclear industry. The funding would be for those PhDs that focused on civil nuclear technology, safety designs and uses for material currently labeled as nuclear waste.
I'd be interested if amongst the people that posted on here if anyone has thought about something similar?
Ability to re-use some of the nuclear waste, as MSR and "travelling wave" designs are promising, is an enormous incentive. 700 millions is peanuts compared to that.
Probably correct about military, though. They need mostly mobile designs, as compact as possible, and they can use highly enriched fuel to achieve this.
Then again - there are talks that Navy has several long-shot projects underway.
Like this one: http://en.wikipedia.org/wiki/Polywell#FY_2012_Work
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