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News Navigator: What is 'pluthermal' nuclear power generation?

This photo shows the spent fuel pool at reactor No. 3 at Shikoku Electric Power Co.'s Ikata Nuclear Power Plant, where used MOX fuel is being stored, in Ikata, Ehime Prefecture, on Jan. 14, 2020. (Pool)

The Mainichi Shimbun answers some common questions readers may have about the reuse of plutonium for power generation.

    Question: I've heard that there are problems with a type of nuclear fuel used in power plants in Japan. It was called "plu-" something...

    Answer: It must be "pluthermal" power generation you're thinking of. Plutonium extracted from used nuclear fuel and then processed can be used as nuclear fuel again. Producing electricity using such recycled nuclear fuel is called pluthermal power generation. In this method, conventional nuclear fuel and recycled nuclear fuel at a ratio of 2 to 1 are put into nuclear reactors.

    Q: Isn't it called "recycled fuel power generation"?

    A: That recycled nuclear fuel is called "MOX (mixed oxide) fuel," and it's a mixture of recycled plutonium and uranium. "Pluthermal" is a Japanese-English word referring to the method of power generation using "plutonium" in a conventional "thermal" nuclear reactor.

    Q: Why generate power by the pluthermal method?

    A: MOX fuel is planned to be used in next-generation "fast-breeder" reactors, but there has yet to be a completion date set for the new design. As a result, the amount of plutonium for MOX fuel held by power companies across Japan has increased to some 46 metric tons. That's enough for thousands of nuclear bombs, and Japan would be criticized by the international community if it kept the plutonium instead of using it for generating power. That's why power companies in Japan are seeking to generate power by the "pluthermal" method: to consume their plutonium stocks.

    Q: Is the plutonium being used up?

    A: No. There are only four reactors in Japan that can generate power by the "pluthermal" method and that the Nuclear Regulation Authority has permitted to resume operations, with only one currently in service. The power industry had planned to run 16 to 18 such reactors, but following the 2011 meltdowns at Tokyo Electric Power Company Holdings Inc.'s Fukushima Daiichi nuclear plant, the industry revised its target down to a minimum of 12 MOX-fuel-capable reactors in operation by fiscal 2030. Even if they go into operation, however, experts have pointed out that these reactors cannot be expected to consume as much plutonium as fast-breeder reactors.

    (Japanese original by Suzuko Araki, Science & Environment News Department)

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