This article has been updated with extra information on the earthquake made available by France's Institute for Radiological Protection and Nuclear Safety (Institut de Radioprotection et de Sûreté Nucléaire, IRSN) on 17 June.
Four nuclear power plants operated normally during the 6.8 magnitude earthquake in the prefecture of Iwate, northern Japan.
|Ventilation stacks of Fukushima I
Four power plants experienced tremors at 8.43am on 14 June as well as a used nuclear fuel reprocessing plant, an enrichment facility and a low-level radioactive waste store, according to an Atoms In Japan
report from the Japan Atomic Industry Forum. Few buildings were damaged in the country at large, but the tremors caused the deaths of nine people and injured a further 233.
The power plants, Onagawa, Higashidori, Fukushima I and Fukushima II - which between them sport 14 reactors - were all unaffected by the earthquake in any significant way. No damage has been reported, although checks are underway to make certain. A total four litres of water from cooling pools at Fukushima II unit 2 and 4 was shaken to the surrounding plant floor. Another 15 litres of water was displaced from pools at a solid radioactive waste facility at the plant. All the reactors operated normally through the earthquake and continue to do so, according to AIJ, which said the water spilled was about as radioactive as water in hot springs.
The epicentre of the earthquake was 390 km from Tokyo, and about 75 km and 175 km from the Onogawa and Fukushima I and II nuclear power plants on the Sea of Japan. The plants experienced ground acceleration rates of 0.1 g and 0.3 g respectively (100 and 300 gals), according to France's Institute for Radiological Protection and Nuclear Safety (Institut de Radioprotection et de Sûreté Nucléaire, IRSN), which added that Japanese regulations demand nuclear plants are able to withstand accelerations of 0.6 g (600 gals).
There were no alerts at the Rokkasho reprocessing facility, which has started some limited operations while nearing completion. The enrichment facility and low-level radioactive waste store at Rokkasho also felt tremors but were unaffected.
Fukushima I and II are owned by Tokyo Electric Power Company (Tepco), while Onagawa and Higashidori are owned by Tohoku Electric Power Company. Facilties at Rokkasho are operated by Japan Nuclear Fuel Ltd.
Last year, Tepco's Kashiwazaki Kariwa power plant was close to the epicentre of a 6.8 magnitude eathquake. All eight of the plant's reactors shut down safely while a small amount of water was shaken from cooling ponds and discharged to sea. Nuclear safety was maintained, but non-nuclear buildings and equipment at the plant suffered widespread damage and the plant remains offline for repairs. The loss of the plant's generation capacity has hurt Tepco financially as it has had to buy replacement power.