Photo/IllutrationMembers of the Fukui prefectural nuclear safety expert committee inspect the Monju prototype fast-breeder reactor in Tsuruga. (Ippei Yaoita)

The Japan Atomic Energy Agency (JAEA) on Aug. 30 started work to remove nuclear fuel from the Monju prototype fast-breeder reactor in the first stage of decommissioning the trouble-prone experimental reactor in Tsuruga, Fukui Prefecture.

It is the first step in a long and grueling process that will take three decades. Safe and steady progress is vital for achieving the goal.

Monju burns uranium-plutonium mixed oxide (MOX) fuel and is cooled by liquid sodium, instead of water.

Monju worked only very briefly during the more than 20 years of its life, and the government decided to pull the plug on the reactor at the end of 2016.

While the work to remove fuel continues, the liquid sodium coolant will be extracted from Monju, and related equipment will be dismantled. The reactor building will then be demolished and removed.

There have only been 10 or so cases of decommissioning a fast reactor in the world. These rare projects have been carried out in such countries as the United States, Britain and France. Maximum caution is in order to ensure safety in the process.

Plutonium is a material used to make atomic bombs. To avoid causing unnecessary concerns about nuclear proliferation, the operator should adequately share information about fuel transfer work with the International Atomic Energy Agency (IAEA).

According to the JAEA’s plan, 530 fuel assemblies will be removed from the reactor core and the storage tank outside the reactor, which are filled with sodium coolant. The fuel assemblies will be cleaned before being transferred to an on-site water-filled storage pool. This stage is scheduled to be completed by fiscal 2022.

Since sodium is not transparent, it is impossible to see the fuel assemblies submerged in liquid sodium while retrieving them.

Only two fuel assemblies have ever been transferred to the pool at the Monju plant. There are only about 10 workers who have experienced the task.

During a test operation eight years ago, refueling equipment fell into the reactor vessel. Work to remove fuel was originally scheduled to begin in late July, but the start has been delayed by one month due to a series of troubles with related equipment.

A rigorous system of checks and double-checks is indispensable for ensuring steady progress in the project.

Removing fuel is not the only part of the process that requires great care and caution. Sodium reacts violently with water or air. A sodium leak accident at Monju in 1995 caused a fire. Radioactive sodium requires particularly cautious handling.

The JAEA is known for its problem-plagued history. It has been criticized for poor safety consciousness and lax discipline.

While scrapping Monju, the JAEA will also decommission its facility to extract unused fissionable material, plutonium to be exact, from spent nuclear fuel in Tokai, Ibaraki Prefecture, in a 70-year-long process.

That means the JAEA will have to maintain high levels of alertness, attentiveness and discipline for a very long period of time.

Some 1.1 trillion yen ($10 trillion) has already been spent on the Monju project, and decommissioning the reactor will cost at least 375 billion yen. Most of the money has been or will be paid by taxpayers.

No sharp increase in the cost of decommissioning due to glitches or human errors is acceptable.

It should not be forgotten that the process also poses one common and sticky challenge involved in decommissioning any nuclear reactor.

No decision has been made on how to dispose of the nuclear fuel, sodium and other radioactive waste that will be produced in the decommissioning process.

Instead of postponing actions to tackle this challenge, the government should immediately embark on serious efforts to find a solution to this tough question.

--The Asahi Shimbun, Aug. 31