Some margin of error

May 17, 2013

TEPCO: Less water than initially thought leaked from nuke plant tanks

http://ajw.asahi.com/article/0311disaster/fukushima/AJ201305170053

THE ASAHI SHIMBUN

A significantly smaller amount of radioactive water than originally believed leaked from underground storage tanks on the grounds of the Fukushima No. 1 nuclear power plant, according to new estimates by Tokyo Electric Power Co.

TEPCO said May 16 an estimated 300 liters of radioactive water escaped from the No. 2 storage tank, down from the 120,000 liters the utility initially estimated on April 6. The water leaks were first spotted at the No. 2 tank on April 5, followed by similar leaks found at the No. 3 tank on April 7, and the No. 1 tank on April 9.

On May 16, the utility also estimated the combined amount of radioactive water leaks from the No. 1 and No. 3 storage tanks at 90 liters maximum, which is 390 liters total leakage when the three tanks are combined.

TEPCO officials added that only an estimated maximum of 30 liters escaped into the soil, with the bulk of the radioactive leaks remaining within a three-layered sheet structure of the storage tanks. They attributed the overestimation for the No. 2 tank to errors in the readings of a water level gauge, which were used to evaluate the amount of leakage.

The new estimates were derived from radioactive substance concentrations in the leaked water and other data, TEPCO officials said.

Leak in Fukushima plant tank far smaller than earlier estimated

http://mainichi.jp/english/english/newsselect/news/20130517p2g00m0dm005000c.html

FUKUSHIMA, Japan (Kyodo) -- The operator of the crippled Fukushima Daiichi nuclear complex said Thursday that around 20 liters of radioactive water escaped from the first of three underground water tanks found to have leaked at the plant, much smaller than the earlier estimate of 120 tons.

Tokyo Electric Power Co. also said most of the 20 liters of water is believed to have remained within leak-detecting equipment located close to the No. 2 tank and did not seep into the soil.

TEPCO President Naomi Hirose told a press conference in Fukushima Prefecture that regardless of the volume, it was still "a fact" that leaks occurred at the plant, vowing to get to the bottom of the incidents.

The utility came up with the revised figure for the leaked water as it has been studying in detail a series of leaks confirmed in April from three of the plant's seven underground tanks. The incidents led the utility to decide to pump out all the contaminated water stored in the cisterns.

The handling of the radioactive water remains a challenge for TEPCO because the amount increases everyday as a result of continuing injections into the three reactors that suffered meltdowns during last year's nuclear crisis.

The underground cisterns were constructed to store part of the water but ended up being useless.

TEPCO has not yet determined exactly where the leak in the No. 2 tank occurred.

It also said the volume of polluted water that seeped into the soil from the Nos. 1 and 3 tanks was smaller than that from the No. 2 tank.