"The tanks were built in a rush and we couldn't handle all the work"

August 28, 2013

TEPCO didn't take measurements of problem tank after ground sank

http://mainichi.jp/english/english/newsselect/news/20130828p2a00m0na010000c.html

Tokyo Electric Power Co. (TEPCO) performed only one check to make sure new storage tanks that were built to hold highly radioactive water at its Fukushima No. 1 Nuclear Power Plant were in the right position and weren't on a lean, it has been learned.

The finding comes after 300 tons of highly radioactive water leaked from one of the tanks in what the Nuclear Regulation Authority deemed to be on par with a Level 3 (serious incident) on the International Nuclear and Radiological Event Scale.

It is believed that the leak occurred as a result of the ground beneath the tank sinking, warping its steel body, but TEPCO didn't take any new measurements after this -- a fact highlighting the sloppy management of contaminated water at the plant.

In July 2011, TEPCO noticed that the concrete base for new tanks that were being tested had sunk about 20 centimeters into the ground. The utility disassembled the tanks and moved them to another location, but this month one tank was found to be leaking.

In a probe after the leak was detected, TEPCO learned that the leaking tank was built about one month before the ground was found to be sinking. However, detailed measurements including those to check whether the tank was leaning even slightly were conducted only once, before it was put into use. It also emerged that the reason TEPCO realized the ground was sinking was because there was a visible crack in the concrete base.

There are currently about 1,000 tanks on the premises of the crippled nuclear plant, including 350 of the same type as the one which leaked, but measurements were taken only once for each tank.

TEPCO is aware that the ground at the nuclear plant sank as a result of the March 2011 earthquake. When asked why the company was not more thorough when it came to checks, a representative explained, "The tanks were built in a rush and we couldn't handle all the work." In light of the possibility of similar problems occurring with other tanks, TEPCO set up a headquarters handling measures on contaminated water and storage tanks on Aug. 26, and will consider how to approach the situation.

Yuzo Onishi, a member of the government committee managing contaminated water who is versed in civil engineering work, said that when handling highly contaminated water, it is advisable to take measurements regularly to reduce risks.

At a Nuclear Regulation Authority (NRA) working group meeting on Aug. 27, TEPCO expressed the view that the radioactively contaminated water began leaking from the tank in early July, as radiation dosages of workers near the tanks started rising around July 9. Furthermore, based on the rate at which water was leaking, it had been previously calculated that the water started leaking about one month before the leak was detected on Aug. 19.

The NRA has citied the possibility of the leaking section being located at the bottom of the tank, and had instructed TEPCO to conduct a focused inspection. It says that if TEPCO does not adopt an appropriate response, it will consider issuing an order to TEPCO to take action.