Ground subsidence could have damaged leaky tank at Fukushima plant

August 25, 2013

THE ASAHI SHIMBUN

A tank that caused a serious leakage of radioactive water in the compound of the crippled Fukushima No. 1 nuclear power plant was transferred to its current location after causing the ground to subside where it was previously situated, Tokyo Electric Power Co., operator of the plant, said on Aug. 24.

TEPCO said the tank may have been damaged or distorted when the ground settled unevenly, which led to the leakage of about 300 tons of water highly contaminated with radioactive materials. The utility has acknowledged that the water may have reached the ocean, triggering a new crisis as it searches for the cause of the leak.

The 11-meter-high cylinder-shaped tank, with a diameter of 12 meters, has a storage capacity of 1,000 tons of water. It is made of steel plates connected with bolts, rather than being welded, which is considered a more sturdy construction method.

According to TEPCO, three tanks, including one that leaked the contaminated water, were initially installed at the previous location in June 2011.

The next month, workers poured water into the tanks to see whether they would leak. At that time, the ground subsided about 20 centimeters. Because of that occurrence, they dismantled the tanks.

Subsequently, the workers installed the tanks in the current location in October 2011. At that time, a subcontractor that checked the effects of the ground subsidence told TEPCO that there were no problems with them. They also poured water into the tanks at that time and confirmed that they were not leaking.

TEPCO plans to transfer highly contaminated water not only from the leaking tank, but also from the other two tanks on the site as a precautionary measure.

About 350 tanks of the same structure are currently being used in the compound of the nuclear plant to store water that was contaminated with radioactive materials.

“We are considering replacing them with new ones,” Zengo Aizawa, TEPCO executive vice president in charge of the nuclear power division, told reporters in the Fukushima prefectural government office in Fukushima on Aug. 24.

THE ASAHI SHIMBUN
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The photo taken by Tokyo Electric Power Co. on Aug. 23 shows the inside of the tank from which contaminated water leaked. Joint seams in which steel plates are connected with bolts can be seen. (Provided by TEPCO)

The photo taken by Tokyo Electric Power Co. on Aug. 23 shows the inside of the tank from which contaminated water leaked. Joint seams in which steel plates are connected with bolts can be seen. (Provided by TEPCO)

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  • The photo taken by Tokyo Electric Power Co. on Aug. 23 shows the inside of the tank from which contaminated water leaked. Joint seams in which steel plates are connected with bolts can be seen. (Provided by TEPCO)

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