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US government calls on Japan to reduce plutonium stockpiles

Nuclear Monitor Issue: 

The US government has called on Japan to reduce its stockpiles of separated plutonium. The request was made by the US Department of State and National Security Council ahead of next month's extension of a bilateral nuclear cooperation agreement, Nikkei Asian Review reported.1

Japan can reprocess spent nuclear fuel under the Japan-U.S. Nuclear Cooperation Agreement, which is expected to be automatically extended beyond its expiration on July 16. If the two countries come to any agreement about Japan's plutonium stockpiling, it is unlikely to be included in the treaty-level Nuclear Cooperation Agreement.

Nikkei Asian Review reported that Japan's nuclear regulator is expected to adopt a policy of capping the plutonium stockpile and delaying the start-up of the Rokkasho reprocessing plant. However the start-up of Rokkasho has been delayed over 20 times and it is unclear whether serious consideration is being given to a further delay to deal with the problem of growing plutonium stockpiles.

Tokyo "will respond in good faith to the [US] request, but this will also require efforts by power companies," said a Japanese government source. "This isn't something that is going to happen overnight."1

The Asahi Shimbun newspaper reported that the Cabinet Office's Japan Atomic Energy Commission will incorporate measures to curb plutonium stockpiling in its five-point basic nuclear policy expected at the end of June; and that a reduction in plutonium stockpiles held by Japan will also be specified in the government's basic energy plan, which will be revised next month.2 The government's draft policy allows for separation of plutonium from spent fuel based on the projected amount to be used in reactors as mixed plutonium-uranium oxide fuel (MOX), Asahi Shimbun reported.

It seems that the government will pressure utilities to operate more reactors using MOX rather than conventional uranium fuel. The Federation of Electric Power Companies of Japan estimates that MOX fuel should be used at 16‒18 reactors to keep Japan's plutonium stockpile from rising.2 Of the nine reactors that have restarted in the past few years, four can use MOX fuel.2

The prospects for plutonium-fueled fast reactors could hardly be bleaker. Japan has permanently shut down the Monju fast reactor, and Japan's involvement in the planned ASTRID demonstration fast reactor in France is in doubt.3,4

Ending the reprocessing of Japan's spent fuel (currently in Europe, later at Rokkasho) would signal serious intent to address the problems associated with plutonium stockpiling (including the regional tensions and proliferations risks arising from Japan's plutonium program). But the Japanese government seems determined to go ahead with Rokkasho despite the endless delays and the mind-boggling increases in the cost estimates ‒ the latest estimate is ¥2.9 trillion (US$26.4 billion; €22.9 billion).2 Japan's Atomic Energy Commission estimated in 2011 that building Rokkasho and operating it for 40 years will cost ¥11.68 trillion (US$106 billion; €92 billion).5

Costs associated with reprocessing Japan's spent fuel in Europe are also mind-boggling. The Citizens' Nuclear Information Center reported in August 2017 that the cost of reprocessing and transporting back to Japan and managing the high level radioactive waste, which is at present overseas, is estimated at ¥13.9 trillion (US$127 billion; €110 billion) and fabrication of MOX fuel at ¥2.3 trillion (US$20.9 billion; €18.1 billion).6

(Written by Nuclear Monitor editor Jim Green.)

1. Nikkei Asian Review, 10 June 2018, 'US demands Japan reduce its plutonium stockpiles',

2. Yusuke Ogawa, Rintaro Sakurai and Shinichi Sekine / Asahi Shimbun, 17 June 2018, 'Japan to cap plutonium stockpile to allay U.S. concerns',

3. Asahi Shimbun, 31 May 2018, 'Scaling back of French reactor a blow for nuke fuel reprocessing',

4. Asahi Shimbun, 18 June 2018, 'EDITORIAL: Japan should disconnect from fast-breeder reactor project',

5. Atomic Energy Commission Bureau, 10 Nov 2011, 'Estimation of Nuclear Fuel Cycle Cost',

6. Citizens' Nuclear Information Center, July/August 2017, 'Project Cost Estimate for the Rokkasho Reprocessing Plant', Nuke Info Tokyo No. 179,