Radioactive leak at Chiba ?

March 22, 2012

Chloride ion detected at radioactive waste disposal site in Chiba Prefecture

http://mdn.mainichi.jp/mdnnews/news/20120322p2a00m0na015000c.html

KIMITSU, Chiba -- Highly concentrated chloride ion was detected in a water well at a disposal site for radioactive waste from areas affected by last year's March 11 disasters here, suggesting that water stored at the site may have leaked, it has been learned.

While chloride ion is not particularly harmful, the Chiba Prefectural Government is moving quickly to perform an analysis of the situation, not excluding the possibility that radioactive cesium in the disposed materials may have also leaked.

The Chiba Prefectural Government became aware of the incident in January of this year when it detected doses of 250 to 580 milligrams of chloride ion per liter of water stored at an examination well at a radioactive disposal site in the prefectural city of Kimitsu. The doses far exceeded the 26 to 31 milligrams per liter estimated by the site's operating company Arax Group last December.

The disposal site, which is the prefecture's biggest, is used to store radioactive materials, including drain mud and ash from regions affected by the March 11, 2011 disasters. According to the prefectural government, the bottom of the site is covered with water-blocking sheets that are preventing any potential leaks to the exterior of the facility.

Officials at Arax Group have responded to the situation, saying that it is possible that some of the deicer it spread around the disposal site's pathways may have entered the well, thus resulting in the detection of highly concentrated chloride ion.

However, according to sources close to the case, a survey conducted by the prefectural government and the operating company has shown that among several wells located near pathways where deicer had been spread, there were wells where chloride ion doses were very low.

Based on these observations, the prefectural government assumes that the cause of the high chloride ion concentration is not the deicer materials, but points to the possibility that water has leaked from inside the facility.

Furthermore, based on the fact that a sensor at the bottom of the disposal site did not detect the abnormality, the Chiba Prefectural Government estimates that the possibility that a water-blocking sheet had ripped, causing a leak, is low. The prefectural government, however, also does not exclude the possibility that water had leaked from a place where a sensor was not attached.

As a result of the incident, the Chiba Prefectural Government has suspended all transportation operations to the site and has requested the operating company to investigate the situation.

"We are currently investigating the incident by looking at the possibility that it was caused by external and internal factors. We will do our best to provide higher safety operation standards," officials at Arax Group told the Mainichi in a recent interview.

Click here for the original Japanese story