Tokyo Electric Power (Tepco) reports that atmospheric readings have shot as high as 530 sieverts an hour inside the containment vessel of reactor No 2. That is one of three reactors that melted down after a tsunami inundated the north-east coast of Japan in March 2011. The previous high reading was 73 sieverts an hour. One sievert is enough to give a person acute radiation sickness. A single exposure of five sieverts will kill half the exposed people within a month. Exposure to 10 sieverts will kill all the people exposed within two to three weeks. The average America receives a dose per year of 6.2 milli-sieverts (mSv). A chest X-ray delivers 0.1 mSv, a mammogram, 0.3 mSv. Worldwide, the average dosage limit for nuclear workers is 20 mSv a year. The Fukushima reading shows just how hard it’s going to be to clean up the three reactors, a process already estimated to last 40 years. A remote-controlled robot Tepco plans to send into the reactor is built to sustain exposure to 1,000 sieverts before ceasing to operate. With radiation at its current level, the robot would survive for less than two hours.