Japanese nuclear regulators have ordered Tepco to investigate the cause of a leak from a plant used to treat contaminated water at the damaged Fukushima Daiichi plant.
|Puddles of leaked water around evaporative condensation apparatus at Fukushima (Image: Tepco)
A puddle of around 45 cubic metres of water was discovered inside a containment barrier around the evaporative condensation apparatus on 4 December. The apparatus is used to desalinate concentrated salt water produced during the treatment of radioactively contaminated water. Treated water is then re-used for cooling the stricken reactors at the site.
Subsequent investigations revealed a crack in the concrete barrier through which water was leaking into a gutter. Radiation dose rates at the surface of the water were measured at some 112 millisieverts per hour indicting some level of treatment but of course not full decontamination. The leak was stopped with sandbags, and the water that had accumulated inside the barrier was transferred by pump to a waste liquid storage tank.
The gutter into which the water had leaked is connected to the power station's central drainage channel. Plant owner Tokyo Electric Power Company (Tepco) reports that water samples taken from the water channel near the desalination apparatus and also at the seaward end of the drain returned radionuclide analyses that were similar to "or slightly higher" than previous readings, although samples taken the following day showed levels no different to those recorded before the leak.
Japan's Nuclear Industrial Safety Agency has instructed Tepco to investigate the cause of the leak and to take steps to prevent any similar incidents in future. Since there was a leak through the concrete barrier, the regulator has also instructed the company to immediately confirm the soundness of other barrages and strengthen them if necessary, as well as confirming the range and amount of the leakage, whether or not there was any discharge to the ocean, and evaluating the impact of any radioactive materials on the surrounding area.
Researched and written
by World Nuclear News