As reported by the U.K. Guardian and posted at Commondreams, in yet another extremely belated announcement, the Japanese federal Nuclear and Industrial Safety Agency (NISA) has now admitted that "770,000 terabequerels – about 20% as much as the official estimate for Chernobyl – of radiation seeped from the plant in the week after the tsunami, more than double the initial estimate of 370,000." A becquerel is defined as one radioactive disintegration per second; a terabequerel is one trillion radioactive disintegrations per second. That initial estimate, however, was supposed to have accounted for the first month of the catastrophe; the new figure accounts for radioactivity releases during only the first week of the disaster. NISA has also now admitted, nearly three months after this nuclear calamity began on March 11th, that the Unit 1 reactor core completely melted down just five hours after the earthquake disabled the electrical grid, and then the tsunami crippled the plant's emergency backup cooling systems; NISA has also admitted a second reactor core melted down much more quickly than previously acknowledged. Of course, radioactivity releases have continued on even after that first week or month -- right up to the present moment, with the highest atmospheric releases yet detected at the nuclear power plant, with a 400 rem per hour lethal radioactivity dose rate in the Unit 1 reactor building, preventing human access. As that building was destroyed by the first of several giant hydrogen gas explosions, such highly radioactive steam could easily find its way out into the environment. An absorbed dose of 350 rem is fatal for 50% of the people exposed to it. BBC also reported on this story, as did the Wall Street Journal (subscription required).