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Decommissioning Monju, but how?

December 13, 2017

Editorial: Monju reactor will be decommissioned, but mountain of uncertainty remains



The Japan Atomic Energy Agency (JAEA) has submitted its plan to decommission the Monju experimental fast-breeder reactor in Tsuruga, Fukui Prefecture, to the Nuclear Regulation Authority (NRA).

The Monju reactor uses liquid sodium as a coolant, which reacts violently when exposed to water or air. There has never been a reactor like the Monju unit in the country, and so there is no precedent for decommissioning it. In short, this will be a very tough road, strewn with many obstacles.


In addition to giving the JAEA's proposal a vigorous vetting, it is essential that the NRA keep a careful watch on the plan's progress after approval.


According to the JAEA's plan, the Monju decommissioning will take 30 years, wrapping up in fiscal 2047. The work will be broken into four phases, with phase one -- including removal of the reactor fuel assemblies -- set for completion in fiscal 2022. In phase two and after, the JAEA will remove the radioactive sodium coolant and dismantle the Monju facility. The estimated cost for all this is about 375 billion yen.


However, there is currently only a detailed work schedule for phase one. Furthermore, Fukui Prefecture has demanded the spent reactor fuel be moved outside its borders, but there is as yet no place for it to go. Moreover, the decommissioning plan has no blueprint for how to get the sodium coolant out of the reactor, so the exact nature of the process has yet to be determined. The JAEA says that extracting the coolant is "sufficiently technically feasible," but NRA Chairman Toyoshi Fuketa has said that the JAEA "is being overly optimistic if it thinks it can do it just by going ahead with the project."


It was the JAEA's mismanagement of the Monju reactor, its repeated scandals including inspection oversights, which triggered the reactor's decommissioning in the first place. It is perfectly natural that the Fukui Prefectural Government is expressing misgivings about leaving the project in the hands of such an organization.


The central government will establish a committee to explain the structure and progress of the Monju decommissioning project to local residents. However, it should also reveal the information to the broader Japanese public, and be subject to its assessment.


France has already shuttered its fast-breeder reactors, and we would like to see Japan make the most of French experience and technology to help guarantee the Monju decommissioning is undertaken safely and soundly.


To date, development of the Monju fast-breeder reactor has cost the public purse over a trillion yen, though the unit has spent just 250 days on line. The cost of decommissioning the plant may also mount. Meanwhile, the Rokkasho nuclear fuel reprocessing plant in Aomori Prefecture -- another vital link in the government's fuel cycle plan -- has no immediate prospects of going into full operation.


The government began revamping its basic energy plan this past summer. The present proposal states that reliance on nuclear power will be reduced as much as possible. If that is indeed the goal, then first the government must decide once and for all that the stalled nuclear fuel cycle program needs to be reconsidered.


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