Factbox: Japan nuclear plants’ status after Thursday quake

(Reuters) – A major 7.4-magnitude aftershock rocked northeast Japan on Thursday, stirring worries of fresh damage to the coast devastated by last month’s massive quake and tsunami, which also triggered a nuclear safety crisis at the Fukushima Daiichi plant.

No damage from the aftershock was detected at the crippled Fukushima plant, operator Tokyo Electric Power Co (TEPCO) said.

Following are the most recent status updates of major nuclear plants in the affected area:

Fukushima Daiichi, in Fukushima prefecture, northeast Japan, operated by TEPCO

– No new damage reported. TEPCO still checking whether measuring equipment is in working order.

– Workers briefly evacuated after quake but are now back after tsunami warning lifted.

– No change in radioactivity after quake.

– Cool-down efforts at reactors 1, 2, and 3 continuing as before.

– No impact on nitrogen-injection process at reactor No.1.

Fukushima Daini, operated by TEPCO, shut down after March 11 quake.

– No damage detected after quake.

– No change in radioactivity after quake.

Onagawa nuclear plant, in Miyagi prefecture, northeast Japan, operated by Tohoku Electric Power, shut down after March 11 quake.

– Water leaks detected from spent fuel pools and other parts of plant.

– Two out of three power sources knocked out, leaving one power source to cool spent fuel.

– Cooling operations stopped, then resumed quickly. No rise in radioactivity detected.

– Onagawa still has emergency backup generator to fall back on.

Tomari nuclear plant, on northern island of Hokkaido, operated by Hokkaido Electric Power Co, operated normally since March 11 quake.

– Power output from No.1 and No.2 reactors cut briefly to 90 percent of capacity after Thursday’s quake, but output returned to normal by Friday morning. No.3 reactor continued to operate at full capacity.

Higashidori nuclear plant, in Aomori prefecture, northern Japan, operated by Tohoku Electric Power, shut since February for planned maintenance.

– Plant used backup generator after regular power source knocked out; external power sources restored by Friday morning.

Kashiwazaki Kariwa plant, in Niigata prefecture, northwest Japan, operated by TEPCO, continued operations after March 11 quake.

– TEPCO says plant is operating normally.

Tokai Daini, in Ibaraki prefecture, south of Fukushima, operated by Japan Atomic Power, shut after March 11 quake.

– No irregularities detected at this plant.

Rokkasho nuclear fuel reprocessing plant, in Aomori, northern Japan, operated by Japan Nuclear Fuel Ltd, has been operating on a test basis.

– The plant lost external power and was running on five emergency diesel generators, but is now switching back to external power sources.

Sources: Japan’s Nuclear and Industrial Safety Agency, Tokyo Electric Power Co (TEPCO), Japan Nuclear Fuel Ltd, public broadcaster NHK and other Japanese media.

(Reporting by Chizu Nomiyama, Risa Maeda and Yoko Kubota in Tokyo; Editing by Edmund Klamann)

Factbox: Japan nuclear plants’ status after Thursday quake