Longer intervals proposed for Japanese units

Tuesday, 4 September 2007 Japanese nuclear power plants could begin to operate for up to 24 months between inspections, under changes proposed by industry and safety authorities.

Under the current Reactor Regulation Law, all Japanese nuclear power plants are operated on a 13-month schedule, at the end of which maintenance and safety inspection takes place. However, in other countries is it common for similar reactors to operate on 18-month, or 24-month cycles, providing more consistency for grid managers and better economy for plant owners. The longest uninterrupted run of a light-water reactor is 739 days, recorded at LaSalle 1 in the USA in February.

Now, the Nuclear and Industrial Safety Agency (NISA) has said it will draft a ministerial ordnance with the aim of changing the law. Atoms in Japan reported that the decision was made after discussion with the Japan Power Engineering and Inspection Corporation and the Japan Society of Mechanical Engineers.

Providing ministerial approval is forthcoming, plant owners could apply to extend their operating cycles from the next financial year, which starts in April 2008. In total, three new inspection intervals would be available - at 13, 18 and 24 months, with 13 remaining standard initially.

To change from the default interval of 13 months, plant owners would have to provide extensive evidence of how each item of plant equipment would fare over longer periods, and describe in detail their new maintenance programs and operational plans.

NISA's proposal would be made available for public comment by the end of September and a trial of the new system would be carried out by the end of the year.

Further information

Nuclear Industrial and Safety Agency

WNA's Nuclear Power in Japan information paper

WNN: LaSalle plant runs up another record