Cooling system at Fukushima Daini reactivated

November 22, 2016

Quake prompts temporary halt to cooling of spent fuel rods at Fukushima No. 2 pool

http://www.japantimes.co.jp/news/2016/11/22/national/quake-prompts-temporary-halt-cooling-spent-fuel-rods-fukushima-no-2-pool/#.WDPyuX2Dmos

by Reiji Yoshida

Staff Writer

A powerful earthquake that rocked the Tohoku region Tuesday morning temporarily stopped the critical cooling system of a spent fuel pool of the Fukushima No. 2 nuclear power plant for about 100 minutes, Tokyo Electric Power Company Holdings Inc. said the same day.

The cooling system was automatically shut down at 6:10 a.m. at the No. 3 pool after sensors detected changes in the water level of a tank that pumps cooling water into the pool, home to 2,360 still-hot spent fuel assemblies and 184 unused ones.

Tepco spokesman Kenichi Nakakuki said the quake likely shook up the water inside the tank, triggering the automatic shutoff.

After confirming that no water had leaked from the tank, Tepco reactivated the cooling system at 7:47 a.m., Nakakuki said by telephone.

No radioactive materials have been leaked from the No. 2 plant, Tepco said. The station is located 12 km south of the heavily damaged Fukushima No. 1 nuclear power plant.

At 6:38 a.m., tsunami of 1 meter in height reached the coast facing the No. 1 plant, but there were no reports of new damage at the plant, Tepco said. The plant was wrecked in the triple meltdown crisis after the March 2011 tsunami-quake disaster.

The Fukushima No. 2 power plant, too, was damaged by the 2011 tsunami but workers there managed to safely shut down its reactors, barely avoided a meltdown crisis.

Operations at the No. 2 plant’s reactors have been suspended since the 2011 disaster due to strong opposition from local residents.

During the shutdown of the cooling system at the pool, the surface temperature of the water at the No. 2 plant rose by 0.2 degree to 29.5 degrees.

Thousands of nuclear fuel assemblies would be severely damaged, releasing massive amounts of radioactive materials into the environment, if the water in the spent fuel pools boils up and exposes the rods.

Internal rules at Tepco have set the upper limit of the pools’ surface temperatures at 65 degrees. If the cooling function was lost and unable to be recovered, the surface temperature would have risen to 65 degree in about seven days, according to Tepco.

In the wake of the 2011 meltdown crisis at the Fukushima No. 1 plant, Japan suspended operations of all of its 48 commercial reactors nationwide. Since then, four have been reactivated after passing stringent new safety regulations set by the Nuclear Regulation Authority.

All of the 48 reactor buildings have spent fuel pools that house thousands of fuel assemblies because Japan has yet to build a final disposal site for them due to opposition from local residents near candidate sites.

Prime Minister Shinzo Abe’s government has worked to reboot more reactors once they pass NRA’s safety standards test.

Cooling system restored at Daini plant

http://www3.nhk.or.jp/nhkworld/en/news/20161122_19/

The Tokyo Electric Power Company says it has restored a cooling system at the Fukushima Daini nuclear power plant that briefly stopped after Tuesday's earthquake.

TEPCO says the system that cools the spent nuclear fuel pool at the No.3 reactor halted about 10 minutes after a strong quake struck off Fukushima Prefecture in the morning.

The utility says it was able to reactivate the system's water pumps about one hour and 40 minutes later, and the cooling operation was restarted. It says no abnormalities were detected.

TEPCO officials said at a news conference that they believe the pumps stopped after the quake shook the water in the pool, activating an alert system.

They said the pool's water temperature was 29.5 degrees Celsius when the cooling operation was restarted. That was 0.2 degrees higher than before the pumps stopped. The upper limit for suspending operations is 65 degrees. Officials said that they also found no abnormalities with the fuel.

The TEPCO officials added that at the Daini plant, one of the monitors for observing nuclear materials in dust in the air also stopped due to a power outage. But it later resumed operation.

At the crippled Daiichi plant in the same prefecture, the officials said that they stopped transferring contaminated water at a water disposal facility as a precaution.

One-meter-high waves were observed at both nuclear plants around 6:30 AM.

The utility's officials also said they have detected no changes so far in radiation levels measured at monitoring posts around the plants.

Quake disrupts cooling of fuel at Fukushima No. 2 nuclear plant

THE ASAHI SHIMBUN

http://www.asahi.com/ajw/articles/AJ201611220029.html

Cooling equipment for a spent nuclear fuel pool at the Fukushima No. 2 nuclear power plant temporarily shut down after a magnitude-7.4 earthquake rocked eastern Japan on Nov. 22.

The plant’s operator, Tokyo Electric Power Co., is looking into the details of the incident that occurred at the No. 3 reactor building around 6:10 a.m., 11 minutes after the earthquake struck off the coast of Fukushima Prefecture.

Pumps for the cooling system automatically halted after an alarm was triggered when the water level fell in the tank that adjusts the water conditions in the spent fuel pool, according to the Nuclear Regulation Authority and TEPCO.

After workers checked the system and confirmed that there were no abnormalities, including water leaks, the cooling equipment was restarted at 7:47 a.m.

The pool accommodates 2,544 spent fuel assemblies.

The plant straddles the coastal towns of Tomioka and Naraha in the prefecture and is located 12 kilometers south of TEPCO’s crippled Fukushima No. 1 nuclear plant.

The water temperature in the pool was 28.7 degrees when the cooling equipment stopped. It had gradually increased to 29.5 degrees until operations resumed.

If the suspension continued, it would have taken seven days for the temperature to reach the maximum operational limit of 65 degrees.

According to TEPCO, the tide level in front of the Fukushima No. 1 nuclear plant was 1 meter high, but no abnormalities were confirmed at the plant.

No problems were reported at Japan Atomic Power Co.’s Tokai No. 2 nuclear power plant in Ibaraki Prefecture and Tohoku Electric Power Co.’s Onagawa nuclear power plant in Miyagi Prefecture. Monitoring posts that measure radiation levels in the air showed no abnormalities.