TEPCO took the Kyodo News's line (see my post from yesterday) and announced that part of the highly contaminated, untreated water from the reactor basements stored in the nearby Process Main Building did leak into the trench, and got diluted by not-so-contaminated groundwater or dew condensation water dripping from an electrical duct.
Probably several tonnes of the highly contaminated water diluted with low contamination water resulting in 230 tonnes of water in the trench, hints TEPCO.
It sure looks like they waited until after the "cold shutdown/accident over" declaration on December 16 to tell you the bad news.
From Yomiuri Shinbun (12/19/2011):
TEPCO announced on December 9 that part of the highly contaminated water stored in the basement of the Process Main Building at Fukushima I Nuclear Power Plant may have leaked to the nearby trench (underground tunnel for the electrical wires).
About 230 tonnes of water was found in the trench on December 18. After analyzing the density of radioactive materials in the water, TEPCO concluded that the highly contaminated water had leaked into the trench, and got diluted by the groundwater and rainwater. According to the company's calculation, it is likely that several tonnes of contaminated water had leaked. Prime Minister Noda declared the end of the nuclear accident on December 16.
According to TEPCO, there is no danger of the water leaking outside the trench, as the groundwater level is higher than the trench. The connection between the Process Main Building and the trench had been sealed shut in April, and the last inspection was done in June. The company will monitor the level of water in the trench, and decide what to do.
From TEPCO's press release (12/19/2011)
The density of radioactive cesium turns out to be just what I reported yesterday
From TEPCO's information:
- Cesium-134: 4,200 becquerels/cubic centimeter
- Cesium-137: 5,400 becquerels/cubic centimeter
Water dripping from the duct:
- Cesium-134: 0.13 becquerel/cubic centimeter
- Cesium-137: 0.12 becquerel/cubic centimeter
Photo of the trench filled with water, from TEPCO's photo for the press, taken on December 18, 2011:
Photo of the duct for electrical cables: