Would this embargo have any bite?
Other than for a mild and temporary commercial disadvantage, it's hard to see how this would hurt Russia.
Although Russia's stocks of uranium are limited, like the USA, and the UK come to that, she has more than enough plutonium to destroy the world several times over. Russia also has significant reserves of thorium, which could supply her energy needs for a good many years. In addition, Gen-IV reactors, projected to be running within a decade or so, will be able to utilise a far greater proportion of uranium fuel than present-day reactors.
The USA put an embargo on sales of gas turbines to Russia some years ago, assuming that this would hinder the development of Siberian oilfields. The result was that Russia rapidly discovered how to make them and joined world leaders in turbine technology.
Similarly, an Australian embargo on uranium might actually do Russia a favour if it were to encourage her to put more emphasis on the new and more effective thorium powered nuclear technologies and thus take a lead in a large emerging world market.