The Japan Times

Wednesday, February 02, 2000


Nuclear guideline draft defines what emergency is

A subcommittee of the Nuclear Safety Commission drew up guidelines Wednesday that include a requirement for operators of nuclear facilities to promptly inform local governments if monitors show gamma ray levels of 5 microsieverts per hour.

Under the guidelines, the government would set up a task force headed by the prime minister in the event radiation levels amount to 500 microsieverts per hour. One microsievert is a thousandth of a millisievert.

The guidelines would be utilized in the government's efforts to galvanize disaster prevention areas nationwide ahead of the implementation of new laws regarding nuclear safety that were enacted by the Diet in December.

Under Wednesday's guidelines, operators would have to notify local authorities if a monitoring device set up at the outermost point at a facility registers radiation of at least 5 microsieverts per hour for 10 minutes or more, or if two monitors pick up such radioactivity at the same time.

While this level is not harmful to humans, the new guidelines require prompt notification to authorities.

In addition, notification would also be required in the event unusual readings are picked up by monitors placed near vents as well as when problems that could lead to major disasters are detected.

If these new guidelines are applied to the September criticality accident at the JCO Co. uranium-processing plant in Tokai, Ibaraki Prefecture, notification would have been necessary immediately after the problem occurred.

With the 800 microsieverts detected in the emergency monitoring that ensued, a central government task force should have been set up swiftly after the disaster, which was triggered by workers who used a bucket to pour an unsafe amount of highly enriched uranium into a tank.

The latest revisions to nuclear safety legislation would have the central government, rather than local municipalities, play a major role in the event of nuclear disasters.