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Reducing Plutonium Holdings

Published on October 18, 2018: The Denki Shimbun (The Electric Daily News)
Shojiro Matsuura
Advisor

As has been reported, the current Japan-US Atomic Energy Agreement reached its 30-year deadline on July 16 and was automatically renewed. Now, if either Japan or the United States gives notice of its intent to withdraw, then this agreement will lapse after six months. It has, in fact, been pointed out that this arrangement mirrors a very unstable situation. Nevertheless, according to conventional wisdom in keeping with international relations in our world today, the advantages and disadvantages to both countries, should this agreement lapse, are quite clear. Automatic renewal provides quite stable continuity.

Still, this agreement, which was based upon the conclusion reached in the International Nuclear Fuel Cycle Evaluation (INFCE, 1977~79), is a very important pact that both Japan and the United States concluded after participants on both sides toiled and poured in their wisdom to work out the specifics. It has also been said that this agreement constructed a solid framework within which Japan, seeking to complete its nuclear fuel cycle, implemented the internationally-accepted atoms-for-peace program. There were many difficult issues related just to this implementation that had to be overcome. Some of the key matters have already been pointed out in this column by Keiji Miyazaki, Kumao Kaneko, and Masao Nakamura (see articles published on July 30, August 1 and August 30, respectively), all of whom are well acquainted with the circumstances of that time.

In spite of the different perspectives, one issue that has regularly been pointed out is plutonium. The core concern here is that the amount of separated plutonium held by Japan is much more than what was expected. In addition, commentators in many quarters have argued that further increases in Japan’s holdings will raise nuclear proliferation concerns.

The principal cause of the increase in Japan’s plutonium holdings has been the lack of progress, compared to estimates, in the evolution and development Japan’s fast reactor, which was projected to require a large quantity of plutonium. In addition, Japan has not been able to use plutonium in its commercial light water reactors, which proceeded concurrently, as initially planned due to a variety of difficulties, one of which is the accident at Fukushima Daiichi Nuclear Power Station.

The situation is much the same in other pioneering countries seeking to complete their nuclear fuel cycle plans. Nevertheless, doesn’t Japan, a nation, which has sought single heartedly to perfect an entire nuclear fuel cycle for peaceful use, have an international responsibility to present some sort of specific and realistic measures to reduce the amount of separated plutonium that it holds as well as implement these measures and explain the process to the international community?

When I was involved in the INFCE roughly 40 years ago, I believed that an overabundance of anything would create instability and disharmony, and that a technical means should be put in place to balance plutonium propagation and reduction as well. Sometime later in the mid-1990s, I presented a basic concept to fellow researchers with whom I was acquainted, describing the necessity of developing a particular type of plutonium burning fuel. At the root of this basic concept was synroc (synthetic rock), which had been developed for disposing of high-level waste. The idea was that the proper quantity of plutonium oxide would be mixed into this material to form a rock-type fuel, which could be loaded around a light water reactor core to use up all the plutonium. Researchers at the former Japan Atomic Energy Research Institute made considerable progress in the basic research relevant to this proposal. Around 2000, it was empirically and theoretically concluded that “the characteristics of rock-type fuel, whose mixture has been adjusted, are almost the same as mixed oxide (MOX) fuel, and its plutonium combustion efficiency is roughly twice that of MOX fuel.” Final disposal of this rock fuel without modification is also possible. It may also be used as an industrial radiation source until the level of radiation intensity attenuates.

Just as the Japan-US Atomic Energy Agreement still shows us today, we need to think about taking out and dusting off old ideas, ones that were put away based on results from years ago, and mobilize all our resources to rectify the present discord and disharmony as we seek to expand future uses of nuclear power.

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