Tokyo Electric Power Co. (TEPCO) announced that while transferring contaminated water containing radioactive material from leaking underground storage tank No. 3 to tank No. 6 at the Fukushima Daiichi Nuclear Power Plant on April 11 this year, water was discovered leaking from a joint connecting the piping being used for the transfer.

About 22 liters of water containing 6.4 billion becquerels of radioactive material leaked from the joint before the problem was chanced upon. TEPCO said the water leaked on top of the berm covering the storage tank and that there was no possibility of it seeping into the soil surrounding it.

There are seven underground water storage tanks at the Daiichi site and currently five are in use. To date, contaminated water has been found leaking from three of the five, tanks No.1 through No.3. Tank No. 3 was leaking the least and TEPCO surmised the leak was located near the upper part of the tank. In order to lower the level in that tank it began transferring approximately 10,400 tons of contaminated water to tank No. 6 at 2:00 p.m. on the 11th. Three minutes later workers found water leaking from the pump being used to drain the tank at the joint where it connect to the piping, and shut off the pump. The leaked water spread out over about 6 square meters of an earthen mound covering the tank and sunk into the soil. TEPCO announced that it would remove that portion of soil.

Results of an investigation by TEPCO of the connector revealed the clamping portion was uneven allowing small gaps to form. When the pump was installed last December no problem was reported with the clamp. However, this was the first time for the pump to be used and TEPCO had not carried out any test using regular water beforehand.

A TEPCO spokesperson apologized at a press conference held on the April 11, saying, “We should have tested the pump with regular water after it was first installed. We are sorry for any worry caused.”

Source: Yomiuri Online