Monju reactor set to restart

The test run of the prototype fast-breeder reactor (FBR) Monju in Tsuruga, Fukui Prefecture, is now expected to start after Golden Week, after prefecture Gov. Issei Nishikawa on April 28 gave the go-ahead for test runs to be conducted. The 280,000 kW reactor — an important part of Japan’s planned nuclear fuel cycle — has been inoperative for the 14 years and five months since Dec. 8, 1995, when some 640 kg of secondary-coolant sodium leaked and caused a fire.

This will be the first time for Japan to restart a reactor that has been out of operation for such a long time. Sodium reacts strongly with air and water. Some deterioration of the reactor’s components due to old age cannot be ruled out.

In March 2008 the Japan Atomic Energy Agency, the operator of Monju, admitted that a 15-km-long active seismic fault runs only about 500 meters from Monju, and that another 18-km-long active seismic fault runs directly under the reactor, about 5 km below ground level. The agency cannot be too careful in conducting test operations at Monju.

The agency also must remember that dishonesty in the wake of the 1995 accident, such as hiding video footage of the incident, deepened people’s suspicions about the safety and integrity of the FBR project. No matter how small in scale, if an accident occurs during the test run, it must not be covered up. All relevant information must be made public.

Monju uses a mixed nuclear fuel of uranium and plutonium, and is supposed to produce more fuel than it burns. In the nuclear fuel cycle, spent nuclear fuel will be reprocessed to extract plutonium, which will then be re-used to generate nuclear power. Some ¥900 billion, including ¥600 billion in construction costs, has been poured into the Monju project. Due to a series of complications, the completion of a separate, spent-nuclear-fuel reprocessing plant in Rokkasho, Aomori Prefecture, has been delayed.

In the first two months of test operations, the agency will operate Monju at zero output. Next year, it plans to achieve 40 percent output — the same level at which the 1995 accident occurred. In 2012, it will try to reach full output. The test-run results must be examined precisely and exhaustively to determine whether the Monju project is safe and worth continuing.