FIRST PUBLISHED: 6.32pm GMT
UPDATE 1: 6.47pm GMT, Status of Onagawa nuclear power plant
UPDATE 2: 1:10pm GMT 8 April, Status of Onagawa nuclear power plant
REVISION: Earthquake revised from 7.9 to 7.1 magnitude
Another powerful off shore earthquake has hit Japan's northeast. Diesel generators have replaced grid power at Higashidori nuclear power plant and the Rokkasho reprocessing facility but there has been no effect on safety at Fukushima Daiichi.
The Ministry of Economy Trade and Industry (Meti) said that seawater pumping to cool the reactor cores of Fukushima Daiichi 1, 2 and 3 continued after a brief evacuation on a tsunami warning. It had been predicted that the magnitude 7.1 aftershock from the quake of 11 March would cause a wave of only 50 centimetres at the plant, but elsewhere on the coast had been braced for waves of up to two metres.
Power from the grid through two of three connections was lost at the Onagawa nuclear power plant, where three reactors have been in cold shutdown since 11 March. Cooling systems are still in operation. According to operator Tohoku Electric Power Company, the plant also suffered water leaks at eight locations, including a spillage of about 3.8 litres in total from the three reactors' spent fuel pools.
The single reactor at Higashidori is offline for maintenance and its full core load of fuel is within the used fuel pond. When power from the grid was disrupted, cooling was maintained by emergency diesel generators. The Rokkasho reprocessing plant also lost grid power and is currently maintained by its diesels.
There have been no signs of any radioactive release from Higashidori, noted Meti. The reactor is a 1067 MWe boiling water reactor that started operation in 2005 owned by Tohoku Electric Power Company.
Another part of the Higashidori site is owned by Tokyo Electric Power Company, which had been preparing to start construction of a 1385 MWe Advanced Boiling Water Reactor (ABWR) unit there in coming weeks. This was to be followed by another unit of the same design and capacity. Tohoku also plans to build another ABWR there.
Other reactors in the region shut down since the 11 March earthquake - at Fukushima Daiini and at Tokai - reported no effect from the earthquake. They continue in cold shutdown, using grid power for cooling systems.
Researched and written
by World Nuclear News