Masafumi Takubo and Frank von Hippel
On 26 December 2022, Japan Nuclear Fuel Limited announced another delay in completion of the Rokkasho Reprocessing Plant. The plant is already 25 years late; completion was originally scheduled for 1997 (in 2020 the startup of the plant was delayed until 2022). It is now projected to be completed in mid-2024 with plutonium-separation operations to begin a year later. The delays are significant for the accumulation and use of separated plutonium in Japan.
According to Japan's Federation of Electric Power Companies (FEPC), if and when the reprocessing plant operates at its design capacity of 800 tons of spent fuel per year, it will separate 6.6 tons of plutonium annually. This could lead to a rapid increase of Japan's stock of separated plutonium, which amounted to 45.8 tons as of the end of 2021: 36.5 tons in France and UK and 9.3 tons in Japan.
From breeders to MOX, and a growing plutonium stockpile
Between 1969 to 2001, Japan's utilities sent about 7100 tons of spent LWR and gas-cooled reactor fuel to France and the UK for reprocessing - originally to obtain startup plutonium for Japan's then-planned fleet of plutonium breeder reactors. About 45 tons of plutonium were separated from this fuel. Following the 1995 sodium fire at the Monju prototype fast breeder reactor, however, Japan's breeder-reactor program was delayed indefinitely.
To assure that Japan's plutonium accumulating in Europe and to be separated at the Rokkasho Reprocessing Plant would be used in fuel, FEPC announced in 1997 that, by 2010, 16-18 Japanese light-water-cooled power reactors (LWRs) would be loading 7-11 tons of plutonium annually in mixed oxide (MOX) fuel. As of the end of 2021, however, Japan's LWRs have used an average of only 0.2 tons of plutonium per year and cumulatively only 4.7 tons since MOX fuel for LWRs was first shipped to Japan from France and the UK in 1999.
In 2018, in an attempt to allay international concern about the size of Japan's stock of separated plutonium, Japan's Atomic Energy Commission (JAEC) issued a policy statement that Japan's stock of separated plutonium held in Japan and abroad would not increase from its then level of 46.6 tons (see also this IPFM blog post). Thus far, this policy objective has been realized - but only because of the continued delays in the startup of Japan's reprocessing plant.
Slow plutonium consumption
Between JAEC's 2018 declaration that Japan's stock of separated plutonium would not increase and the end of 2021, Japan's utilities used about 1.2 tons of plutonium in MOX fuel in four LWRs at an average rate of about 0.35 tons/year. (For the history of MOX fuel shipments and use by Japan, see Mixed Oxide (MOX) Fuel Imports/Use/Storage in Japan.)
New plutonium use plan already obsolete
In 2020, FEPC revised its 2009 goal of 16-18 reactors using MOX by 2015 downwards to 12 reactors by 2030. In FEPC's February 2022 update of its plutonium use plan, it announced that 0.7 tons/year will be used during FY 2022-2024, 1.0 ton in FY 2025, 2.1 tons in FY 2026, and about 6.6 tons/year by FY 2030. The last would match the projected separation rate of the Rokkasho Reprocessing Plant operating at full capacity.
Signs of trouble to this plan were immediately observed, however. Chubu Electric announced an indefinite delay in its plan to introduce MOX into its Hamaoka #4, followed by J-Power's announcement of another delay in the start date of its under-construction Ohma reactor - this time until fiscal year 2030. The Ohma reactor carries great weight in Japan's plutonium use plans because, unlike other Japanese reactors, which are limited to one third or less MOX fuel in their cores, it is a high-powered reactor designed to use a full MOX core. It will take 5 to 10 years to ramp up to a full core, however, with a planned loading rate of 1.7 tons of plutonium per year.
In 2010, construction began on a MOX fuel production plant next to the Rokkasho Reprocessing Plant. As of 26 October 2022, however, the plant was only 9.4% complete. Although the current announced plan is to start operation of the MOX plant by the end of September 2024, that date too will likely be delayed. If the reprocessing plant operates but the MOX plant does not, separated plutonium will accumulate at the Rokkasho Reprocessing Plant.
Plans for Japan's plutonium stockpile in Europe
Japan has almost 22 tons of plutonium stranded in the UK as of the end of 2021. The UK's MOX plant was shut down permanently in 2011, after 10 years of failed attempts to operate it. Japan's government has not yet officially responded to the UK government's 2011 offer to dispose of that plutonium for an agreed price with the UK's own 116.5 tons (as of the end of 2021) .
On the other hand, use of Japan's plutonium in France, where there is an operating MOX plant, is going slowly. Japan's utilities have begun trading plutonium to facilitate the use of this plutonium, amounting to almost 15 tons as of the end of 2021. Shikoku Electric and Kyushu Electric, which have almost used up their plutonium stocks in France, have a combined total of 2.5 tons in the UK. They plan to transfer the ownership of that plutonium to Tokyo Electric Power Company in exchange for TEPCO plutonium in France that TEPCO cannot use.
The challenge remains, however, of disposing of Japan's existing stock of 45.8 tons plus the 6.6 tons/year to be separated at the Rokkasho Reprocessing Plant if and when it operates at full capacity. This challenge could be made much more manageable and less costly to Japan's utilities if completion and operation of the Rokkasho Reprocessing Plant were cancelled. For reasons it has never adequately explained, however, cancellation still appears unthinkable for Japan's government.