AmiMoJo writes "The ongoing leak of radioactive wastewater at the Fukushima Daiichi nuclear plant has been traced to an overflow tank that was built on a slope. Because one side of the tank is lower than the other, water slops over the side when it is nearly full. TEPCO estimates that 430 litres of wastewater seeped outside the barrier around the tank and say some of this water may have flowed into the sea, about 200 meters away. They detected 200,000 becquerels per liter of beta ray-emitting radioactive substances in water pooled inside the barrier around the tank. The safety limit is 30 becquerels per liter. Officials say that a miscommunication with contractors led to the blunder."