New types of reactors were designed, including the Fast Breeder reactor powered by plutonium and cooled by liquid sodium.

新型的反应堆被设计出来，包括由钚提供能量，液态钠参与冷却的快中子增殖反应堆。

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With plutonium no longer needed for use in the world's abandoned fast breeder reactor programmes and nuclear powers getting rid of their atomic weapons, large stockpiles of the highly toxic plutonium metal are starting to build up.

BBC: More suspect nuclear fuel found

And the fast-breeder type of nuclear reactor in which plutonium was used as fuel is no longer economic.

ECONOMIST: The nuclear industry