23 Novembre 2015
November 23, 2015
by Mizuho Aoki
After decades of repeated troubles, the Monju prototype fast-breeder reactor is at a crossroads.
Earlier this month, the Nuclear Regulation Authority lodged its first official request with the education and science ministry to find a new entity to replace the government-backed Japan Atomic Energy Agency (JAEA) to operate the trouble-plagued facility in Tsuruga, Fukui Prefecture.
The ministry has been given about six months to find a replacement. If it fails to do so, the NRA asked the ministry to conduct a fundamental rethink of Monju’s status, which, pundits say, could lead to its decommissioning.
Following are questions and answers about the accident-prone research facility that was completed in April 1991 but has remained, except for brief operational interludes, effectively idled since then.
What is Monju?
It is Japan’s sole prototype fast-breeder reactor, designed to produce more plutonium fuel than it consumes to generate electricity.
Once touted as a “dream reactor,” Monju is the central component of the country’s nuclear fuel cycle program aimed at resolving the nation’s shortage of natural energy sources.
The plan has been to extract plutonium and uranium from spent nuclear fuel and reprocess them into plutonium-uranium mixed oxide (MOX) fuel to be reused at the fast-breeder and other nuclear reactors. Had Monju worked according to plan, it was assumed Japan would no longer need to import uranium.
Monju reached criticality in April 1994 and began generating electricity for the first time the following year. However, it was forced to shut down in December 1995, following a sodium coolant leak and fire, and subsequent cover-up attempt.
Did it resume operation after the 1995 accident?
The reactor went online again in May 2010 for the first time in about 14 years. But just three months later, in August, it was again forced to shut down after a fuel-loading device fell into the reactor vessel.
Monju has been idle since then. Other troubles include JAEA’s failure in 2012 to inspect some 10,000 reactor components, including more than 50 parts vital for the reactor’s safety. This prompted the NRA in 2013 to issue an effective ban on restarting the reactor.
Due to a spate of accidents and JAEA’s apparent slipshod safety management, Monju has operated for just 250 days since it reached criticality in 1994.
Still, more than ¥1 trillion in taxpayers’ money has been poured into the facility. Reports say about ¥20 billion in funding is required annually to maintain Monju even when it is offline.
Earlier this month, Taro Kono, an anti-nuclear Cabinet minister in charge of administrative reforms, criticized the JAEA for wasting money on nuclear fuel transport ship Kaiei Maru, which has been used only four times since its introduction in 2006 but costs about ¥1.2 billion annually to maintain.
Why has Monju been prone to accidents?
Unlike ordinary nuclear reactors that use water as a coolant, the fast-breeder reactor uses sodium, which reacts violently with water.
Experts say Monju’s past accidents were partly due to the difficulty in handling sodium.
Will the science ministry be able to find a replacement for the JAEA?
It would be extremely difficult, experts say.
The key to operating the facility is whether a candidate has the skill and experience to handle sodium.
Hideyuki Ban, co-director of the Tokyo-based Citizens’ Nuclear Information Center, said companies that have been involved in Monju’s construction or operations, including Mitsubishi Heavy Industries Ltd. and the Japan Atomic Power Company, could be possible candidates.
But those companies’ knowledge and ability to handle sodium or Monju itself do not exceed that of the JAEA, he said.
“Although it has struggled, . . . (in the end the JAEA) has continued to run the facility up until now,” Ban said. “I believe there is no entity that has deeper knowledge (about Monju) than the JAEA.”
What would happen if the government scrapped the Monju project?
What the government fears most is that it could have a huge impact on the nuclear fuel cycle goals Japan has pursued since the 1950s.
“There is no change in the government’s policy to pursue (the nuclear fuel cycle) by gaining (the acceptance of) municipalities and the international community,” Chief Cabinet Secretary Yoshihide Suga said on Nov. 13.
Some 17,000 tons of spent fuel rods are stored at nuclear power plants across Japan, waiting to be reprocessed to extract plutonium. If the Monju project is scrapped, they may end up as dangerous waste with nowhere to go.
Experts say that because the government plans to restart reactors nationwide, the storage pools will become full of spent fuel rods. Thus it is widely believed that the government will continue to pursue the use of reprocessed fuel in ordinary light-water reactors even if the fast-breeder reactor project is discontinued.
How much plutonium does Japan possess?
As of December 2014, Japan had about 47.8 tons of plutonium, according to the Cabinet Office.
This includes about 10.8 tons in Japan and 37 tons that have been reprocessed and stored in the U.K. and France, waiting to be returned to Japan to be used as fuel.
NHK reported the amount is enough to make about 5,900 atomic bombs.
Are there any countries other than Japan pushing to develop fast-breeder reactors?
Russia, China and India are still eagerly pushing to develop fast-breeder reactors, but none has established the technologies to operate the reactors.
Many industrialized countries, including the U.K. and Germany, gave up development of the reactors a while ago, given the technical and cost hurdles.