{"Fukushima"} Unit 1 radiation levels within the reactor building measured 300 mSv/hr within hours of the earthquake indicated fuel melting had already begun. Engineers now think that molten fuel and assemblies slumped to the bottom of the reactor vessel (known as "slag") and melted a hole in the bottom of the containment shield within 16 hours of the event. TEPCo said that it had discovered an Olympic pool sized of highly radioactive water in the basement of Unit 1 over the weekend, the result of pumping cooling water over the reactor for the past three months. Containments of Unit 2 and 3 have also been breached by molten fuel. Robotic monitoring of radiation levels there indicate that is still far too 'hot' for humans to enter either reactor building. These developments mean that TEPCo's plan to bring the reactors to a cold shut down in nine months is unrealistic. Evacuation of contaminated villages beyond the original 20 kilometer exclusion zone finally began over the weekend as the Japanese government and TEPCo reluctantly begin to face the full ramifications of the nuclear disaster on their hands.
More:{6.5.11}The Japanese government has requested the closure of Hamaoka Nuclear Power Plant until its owner Chubu Electric Power builds stronger defenses against earthquakes and tsunamis. Hamaoka is located on the coast southwest of Tokoyo in a seismically active area. Government experts put the chance of a 8.0 magnitude trembler at 90% within the next thirty years. Chubu decommissioned the plant's two oldest reactors because of the prohibitive cost of upgrading them to withstand earthquakes. These reactors were built in the 70s as were the Fukushima-Daiichi reactors. The other three reactors were built in the 1980s. The company claims the newer models can withstand major earthquakes. But the Prime Minister said his request was motivated by consideration of the "tremendous repercussions a major accident at Hamakoa would have on the entire Japanese society". A Chubu source told Kyodo news that the company would comply with the request. Yet a third nuclear plant is in trouble in Fukui prefecture. The Tsuruga nuclear plant is leaking radioactivity from fuel rods into the cooling system. The utility said it would shut down the unit manually and examine the cooling system. TEPCo continues to struggle to bring the Fukushima reactors under control, almost two months after a major earthquake and tsunami destroyed four of the six reactors there.
{5.5.11}The Union of Concerned Scientists has released internal documents showing a disagreement among NRC staff about the safety of US nuclear power plants if they were to suffer a catastrophic loss of power of the same magnitude that crippled Fukushima-Daiichi in northern Japan. After the terror attacks of 2001, the NRC realized the vulnerability of US nuclear power installations to sabotage and issued new regulations requiring significant upgrades in security, safety equipment and practices. These procedures are referred to "B.5.b" measures and are not publicly available. Agency officials testified to Congress on March 30th that these measures make US plants safer should a disaster occur like the one at the Fukushima-Daiichi complex. NRC studied the problem of a complete power loss at a GE boiling water Mark I reactor at Peach Bottom, Pennsylvania similar to Fukushima Units 1-4 in a research project named SOARCA (State of the Art Reactor Consequence Analyses). Most experts believe that a loss of grid power and then exhaustion of back-up battery power caused a failure of the cooling systems in Fukushima Units 1-3, allowing the reactors to overheat and melt fuel. An e-mail exchange between NRC staff shows that analysts working directly with the Peach Bottom BWR reactor do not believe the B.5b measures are sufficient to mitigate a severe accident. The relevant measures require equipment to be on site but are untested, and some analysts consider their effectiveness to be "speculative" in "post-event" conditions. The congressional testimony of NRC officials did not reveal these private expressions of doubt.
At Fukushima, technicians are preparing to enter Unit 1 for the first time since the March 11th earthquake and tsunami. The goal is to place four air filtering devices that are intended to reduce radiation levels low enough to allow the construction of a stable cooling system for the reactor. At Unit 2, TEPCo is removing the highly radioactive waste water that has collected in the basement of the turbine building and in trenches outside the building. TEPCo also plans to build a dyke around Units 3 & 4 to protect them from another tsunami should it occur following one of the many aftershocks that are taking place.