The Nuclear Safety Commission on Feb. 22 gave the go-ahead to starting the test run of the prototype fast-breeder reactor (FBR) Monju in Tsuruga, Fukui Prefecture. If the prefectural and municipal governments give their consent, the test run should begin by the end of March at the earliest.

The 280,000 kW FBR, which uses a mixed nuclear fuel of uranium and plutonium and is intended to produce more fuel than it burns, is an important part of a nuclear fuel cycle Japan hopes to establish. In the cycle, spent nuclear fuel will be processed to extract plutonium, which will be then used as nuclear fuel.

Monju started transmitting electricity Aug. 29, 1995. When it was operating at 40 percent of total output on Dec. 8 that year, some 640 kg of sodium used as secondary coolant leaked, causing a fire. The test run is about to start 14 years after the FBR became inoperative. Utmost care should be taken to ensure safety.

At first, the Japan Atomic Energy Agency will run Monju at zero output for two months. It plans to achieve a 40 percent output next year and 100 percent output in 2012. Full-scale operation is planned in or after 2013. Japan plans to begin running a demonstration FBR around 2025 and start operating a commercial FBR around 2050.

An FBR is a complex operation. It uses sodium, which strongly reacts with water or air, as coolant. Moreover, a 15-km-long active seismic fault runs only several hundred meters away from Monju’s site. The JAEA cannot be too careful in the FBR test run. It must disclose all relevant information if Monju develops irregularities.

Monju and the planned nuclear fuel cycle must overcome both safety and cost problems. Already, some ¥900 billion has been poured into Monju and about ¥20 billion is estimated to be needed annually if full-scale operation starts. The completion of a spent nuclear fuel reprocessing plant in Rokkasho, Aomori Prefecture, has been delayed following a series of troubles. A disposal site for high-level radioactive waste has not yet been chosen. The path for establishing a nuclear fuel cycle will not be easy.

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