Nuclear Energy Institute Report on Japan’s Nuclear Reactors, April 7, 2011 (1:00 P.M. EDT)

Washington, D.C.–(ENEWSPF)–April 7, 2011 – UPDATE AS OF 1:00 P.M. EDT.
Tokyo Electric Power Co. continued to inject cooling water into reactors 1, 2 and 3 at the Fukushima Daiichi nuclear power plant, despite a 7.1 magnitude aftershock that hit 70 miles north of the plant.

The temblor, the largest aftershock since the 9.0 magnitude earthquake on March 11, hit at 11:32 pm JST today off the northeast coast. The Japanese government issued a tsunami warning after the earthquake, but lifted it about 90 minutes later.

Three nuclear power plants—Fukushima Daini, Fukushima Daiichi and Onagawa—were shaken, but officials reported no new damage and no injuries to employees. Two of the three electric power lines that supply the Onagawa plant were offline, but normal operations continued with the remaining power line to maintain reactor cooling systems. The plant had been safely shut down since March 11.

Fukushima Daiichi
Seawater radiation levels, while still significantly higher than government safety limits, have decreased near the power plant since TEPCO blocked a leak of highly radioactive water into the ocean. TEPCO said it is too early to credit stopping the leak with the decline.

Workers continued to inject nitrogen gas into the containment vessel of reactor 1, a process that began Wednesday. Inert nitrogen gas is used in reactor containment vessels to stabilize the atmosphere. The nitrogen injection is to prevent possible ignition of the hydrogen that is believed to be accumulating inside the reactor 1 containment. It is expected to take six days to complete the process. Spraying water onto the used fuel storage pools at reactors 1-4 was interrupted briefly because of the earthquake.

TEPCO continued its controlled discharge of low-level radioactive water into the Pacific Ocean to make room in storage tanks for more highly contaminated water on the site. The highly radioactive water in turbine building basements is hampering efforts to restore cooling systems, particularly for reactor 2, where the radiation is highest. Before the highly radioactive water is pumped into the wastewater storage tank, the facility must be inspected for damage, the Japan Atomic Industrial Forum reported. Inspection could take up to a week.

The Japanese government is evaluating possible evacuation of some residents from areas within 12.5 to 18.5 miles of the Fukushima Daiichi site. Residents in the 12.5-mile zone were evacuated early in the emergency. Those within the outer area have been advised to stay indoors. The additional evacuation would be from areas where radiation has accumulated since March 11.

A 7.1 magnitude aftershock in northeastern Japan today caused no damage to nuclear power plants in the area, the Nuclear and Industrial Safety Agency reported. Plant employees at the Fukushima Daiichi, Fukushima Daini and Onagawa plants were evacuated for safety after the temblor, which struck at 11:32 pm JST.

Two of the three electric power lines that supply the Onagawa site were down, officials said, but operations at the plant’s three reactors were continuing as normal with power from the remaining line. There was no change in radiation levels near the plant.

The reactors at the three sites had been shut down since the magnitude 9.0 earthquake on March 11.

There were no damages reported at the Fukushima Daiichi and Daini plants. At Daiichi, where engineers have been working to cool reactors since the March 11 earthquake, fresh water injection continued.