Steve Connor: Can Mox provide the answer this time around?

The debate over new nuclear reactors has overshadowed discussions about what should be done with Britain's immense stockpile of plutonium, which will exceed 100 tonnes when all of its spent nuclear fuel has been reprocessed.

We have the biggest civilian stockpile in the world because of some very bad decisions taken 50 years ago. It was decided that the small amount of plutonium found in spent fuel should be recycled for use in new generation of fast-breeder reactors. But the programme was cancelled some 20 years ago and, as we were committed to reprocessing, the result was a huge mountain of plutonium.

The plutonium was then turned into into a different kind of nuclear fuel – mixed oxide (Mox). Sellafield built a demonstration facility to show how this was done and then constructed a larger Mox Plant to make Mox for a world market. The plant cost £1.3bn, many times its original budget but it failed technically. Anyway the market for Mox fuel was never there, because a cheaper alternative, based on mined uranium ore, was plentiful.

Now the Government is on the verge of announcing yet another Mox plant to deal with Britain's plutonium legacy. It is a multibillion pound gamble by people who will have retired before we know whether the risk has paid off.