Workers found a significant spill from a tank holding radioactive water at Fukushima Daiichi this week, while TEPCO pledged to reduce the levels of ambient radiation caused by the sheer number of similar tanks on site.
Recent developments at the severely damaged nuclear plant in Japan include:
Contaminated Water Overtops Tank
Late on Wednesday, workers discovered that about 100 metric tons of radioactive water had overflowed onto the ground from a storage tank. According to a TEPCO release, two valves on a pipe feeding water into the tank were left open by mistake and a third failed. Jiji Press and other outlets quoted the utility as saying workers had ignored an earlier alarm indicating the tank was full, assuming the valves were closed and the alarm was faulty. Water leaked from the top of the tank and drained through a rainwater spout that bypassed barriers at ground level. Technicians placed the gross beta radiation from the leaked water at 230 million becquerels per liter and radiation from cesium at 13,100 becquerels per liter. TEPCO said seawater testing and the layout of the surrounding area indicated the contaminated water did not reach the ocean.
TEPCO Pledges to Cut Dose at Property Boundary
The leaking tank is among scores of containers hastily assembled to store 340,000 metric tons of contaminated water pumped out of basements to date at the site where water accumulates at a rate of about 400 metric tons per day. X-rays created by the stored water pushed dose levels at the plant boundary to 8 millisieverts per year in December. On Feb. 14, TEPCO told regulators it plans to cut the portion of that dose attributable to the water to below 1 millisievert per year by the end of March, 2015. The company aims to confine ambient radiation at the plant boundary from all sources on-site to that level by March of 2016.