Fukushima: New Report Suggests Fuel Burned Through Vessels

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Summer has arrived in Japan. The pink cherry blossoms that offered some aesthetic respite from the destruction in the weeks after March 11 are long gone, and the heat —and all of the attendant challenges of living long-term with a nuclear disaster — have arrived. In Tokyo, where the mayor has set an ambitious energy reduction goal of 25% given the power plants now out of commission, some workers are shifting their work days to start at 7:30 a.m., and government offices have kicked off the “super cool biz” summertime dress code. On Tuesday, Tokyo announced it would start new radiation testing on beaches, rivers and lakes ahead of swimming season, in addition to the water monitoring that has been started by local governments.

The government also said it is considering further expanding the evacuation zone in certain “hot spots” around Fukushima where radiation levels are still measuring in excess of the exposure limit of 20 millisieverts per year. The announcement follows close on the heels of the government nuclear safety agency’s admission that it grossly underestimated the amount of radiation released in the days following the tsunami: as Eben wrote here earlier this week, the agency’s new estimate of 770,000 terabecquerels is nearly double TEPCO’s original estimate.

Equally worrying is the revelation in a 750-page report that fuel rods in three of Fukushima’s reactors have probably melted through their pressure vessels, or cores, and reached their outer containment vessels. The report, released yesterday by Japan’s emergency nuclear task force, says that fuel in reactors 1, 2 and 3, which TEPCO had acknowledged were in various stages of meltdown, had not only melted, but breached their protective vessels, where TEPCO says the melted fuel is submerged in water and cooling. The utility had previously indicated a breach was possible, and that contaminated water on the site could have come from inside the pressure vessels. This report seems to confirm that suspicion, but the scope of the contamination — including whether it could have reached the environment off the Fukushima power plant site — is not yet clear.

The new report, which Japan will submit to the IAEA, also advises that the Nuclear and Industrial Safety Agency (NISA), the agency tasked with monitoring the safety of Japan’s nuclear power plants, be moved out from under the Ministry of Trade. Last week, a preliminary report from the IAEA suggested that NISA lacked independence in the current structure. On Tuesday, an independent panel of experts also launched a probe into the disasters, headed by Yotaro Hatamura, a professor emeritus at the University of Tokyo.