By Hiromi Kumagai
26 December 2015
(Asahi Shimbun) – Tokyo Electric Power Co. has unexpectedly been forced to deal with an increasingly large amount radioactive water accumulating at the crippled Fukushima No. 1 nuclear power plant after seaside walls to block the flow of groundwater were constructed in October.
TEPCO completed the walls on Oct. 26 to block contaminated groundwater from flowing into sea. The utility began pumping up groundwater from five wells dug between the walls and the plant's reactor buildings. The plan called for releasing the less contaminated water into the sea after a purification process, but TEPCO discovered that the water had larger amounts of radiation than it had expected.
TEPCO officials said the situation has left the utility with no option but to transfer 200 to 300 tons of groundwater each day into highly contaminated reactor buildings since November, a move that could further contaminate the water.
Comprised of numerous cylindrical steel pipes measuring 30 meters tall, the seaside walls were installed on the coastal side of the No. 1 to No. 4 reactor buildings to block contaminated groundwater flowing out of the highly contaminated buildings from reaching the ocean.
To control groundwater levels, TEPCO planned to release the less contaminated groundwater from the five wells into sea after a purification process.
However, the water from four of the wells was discovered to have high levels of tritium--a radioactive substance that is hard to remove--at levels higher than 1,500 becquerels per liter, which means the water cannot be released into sea.
To compound the problem, the seaside walls have also significantly raised groundwater levels, forcing the utility to pump a lot more groundwater than it originally planned.
TEPCO has been forced to temporarily transfer large amounts of the groundwater into highly contaminated reactor buildings, where it could become contaminated to an even further degree by being exposed to melted nuclear fuel.
The utility said it suspects the high levels of radiation found in the groundwater from the wells is due to the water being exposed to highly contaminated soil near the plant’s coastal embankment.
To reduce the amount of contaminated water at the plant, TEPCO began operations in September to pump up the groundwater in wells constructed around the reactor buildings to release it into the sea after a purification process.
The company initially announced that the project had reduced the amount of groundwater flowing into the contaminated reactor buildings from 300 tons to 200 tons a day.
The increasing amount of contaminated water has been stored in tanks constructed in the plant’s compound after going through operations to reduce contamination.
TEPCO plans to increase the amount of water it pumps from wells located elsewhere on the plant site to help reduce the amount of contaminated groundwater accumulating in the seaside wells.
Company officials admitted they are not sure when it can turn things around and reduce the amount of contaminated water at the Fukushima plant.