TSURUGA, Fukui Pref. — Five years after a sodium leak and fire shut down the Monju prototype fast-breeder reactor here, the battle over whether it should be put back into operation still rages.
|The Monju Fast-breeder Reactor sits silent on the Sea of Japan coast.|
Although officials claim drastic improvements in safety have been carried out and Monju should be restarted as soon as possible, local residents and others opposed to the plant remain unconvinced of its safety and are calling on the prefectural government to keep it closed.
The prototype fast-breeder reactor, the only one of its kind in Japan, was designed to burn plutonium rather than conventional uranium. Tsuruga, a city on the Sea of Japan coast, was chosen as its location in 1970.
Construction was not completed until 1991 due to environmental concerns and local opposition. Monju reached initial criticality in spring 1994. Throughout 1995, there were various minor maintenance problems that caused operational delays.
But on Dec. 8, 1995, intense vibration caused a thermometer inside a sodium coolant pipe to break. The pipe heated up and cracked at a point just over a ventilation duct.
|In the incident, a cooling pipe cracked, releasing about 640 kg of sodium coolant.|
Nearly 640 kg of sodium leaked onto the vent and the floor below the pipe. Since liquid sodium burns when it comes into contact with oxygen, a fire also broke out.
Power Reactor and Nuclear Fuel Development Corp. (PNC), the semigovernmental agency then in charge of Monju, tried to cover up the extent of the damage. The falsification included the editing of a videotape taken immediately after the accident, as well as the issuing of a gag order to staff regarding the existence of the real tapes.
Massive public outrage at the coverup destroyed PNC’s credibility and Ryutaro Hashimoto, who assumed the prime ministership a month later, publicly expressed his disgust at the operator.
The accident and ensuing coverup led to several changes in the Monju program.
For one thing, PNC was reorganized into the Japan Nuclear Cycle Development Institute (JNC) in October 1998. More importantly, Monju itself underwent alterations.
“There were four fundamental safety improvements introduced after the accident,” said Tadao Aoki, a senior engineer with the Monju Construction Office, which is part of the JNC.
First was a redesign of the reactor’s thermometer so that it could withstand strong vibrations when sodium passed through the coolant pipes. The second change was an agreement to introduce on-site TV cameras and fire detectors near the pipes, monitored from a control room.
A third change was to design a new drainage system, one with bigger pipes and more lines to make it possible to drain sodium from the room more quickly.
Finally, JNC agreed to introduce a nitrogen gas injection system so that should a sodium leak and fire occur again, the nitrogen would remove the oxygen from the room and minimize sodium burning. All four changes are now being put in place.
In addition to such technical changes, there have been numerous bureaucratic ones.
Prior to the 1995 accident, there was very little coordination between Monju authorities and the fire, police and ambulance units of Tsuruga. Since the accident, however, Aoki and JNC’s Tsuruga office spokesman Keiichi Setoguchi claimed, things have been changing.
“We’re making more efforts to work with local rescue units,” Setoguchi said, adding that emergency drills are now carried out twice a year.
Aware that public trust in Monju has yet to be restored, JNC instituted a campaign to attract tourists to the plant, pointing out that nearly 10,000 people a year are taken through the facility.
“Visitors are shown the exact spot where the leak occurred and given an explanation of what happened,” Setoguchi said. An adjacent building, MC Square, contains exhibits and models of the plant and a detailed explanation of how the leak occurred.
The public relations campaign is especially important because one requirement for Monju to resume operations is approval from the governor.
Although the central government is calling for an early restart, antinuclear activists and many local residents remain convinced that reopening Monju would be a disaster. They are pressuring Gov. Yukio Kurita not to grant permission to restart the plant.
“Fundamentally, nothing’s changed over the past five years. Monju remains dangerous and its safety cannot be guaranteed,” said Kiyoshi Yoshimura, an antinuclear activist based in Tsuruga.
Despite the safety measures, even Aoki admitted that as Monju is a prototype, it is only natural to expect glitches. But he added that this does not mean such problems pose serious safety problems.
Monju’s safety, however, is now a political, as well as a technical issue. As Yoshimura and Aoki indicated, there is a tug of war between not only pro- and antinuclear groups, but also between the prefectural and central governments.
“There are plans to build a Hokuriku shinkansen, but to where it will extend has not been decided. The Liberal Democratic Party members of the prefectural assembly are pressuring the governor to approve restarting Monju in the hopes that Tokyo will agree to extend the Hokuriku Shinkansen Line to Fukui,” Yoshimura charged.
Although Aoki and Setoguchi said they have no idea when the governor may approve the restart, some activists say it could happen quickly to improve Fukui’s chances of getting the bullet train.
Yet even if the governor approves a Monju restart tomorrow, it would be a while before operations could resume due to technical considerations as well as the need to finish putting into place the new safety measures.
“It would probably be about 2003 at the earliest before Monju would be ready to resume operations,” Aoki predicted.