Today’s status will summarize the work on all the Fukushima Daiichi Units.
The original plan to fill the reactor containment structures with water to a depth high enough to cover the fuel in the reactor vessels has been abandoned because of damage to the containment structures from the hydrogen explosions. The new plan calls for circulating water from the reactor buildings or containment into the reactor vessel piping which will cool the fuel and then leak out of the reactor vessels to the reservoir of water they are tapping. The new plan requires continuous pumping of water while the abandon plan required maintaining water level but would not need a continuous injection of water.
The Unit 1, 2, and 3 reactors contain damaged and melted fuel. Data is now available for Unit 1 which indicates extensive melting took place when power was lost and the water covering the fuel boiled off. The cladding and fuel overheated causing it to burn, releasing hydrogen and creating a molten mass which flowed to the bottom of the reactor vessel. The molten mass melted holes in welded seams at the bottom of the vessel. The injection of water into the reactor vessel is keeping the molten mass cool. Because the molten mass continues to produce heat from the radioactive isotopes, cooling will need to continue. Water continues to be injected into the three reactors at rates between 1800 to 2700 gallons/hour.
Work has begun on the putting in the circulating water system for Unit 1. They have started work on covering the damaged Unit 1 reactor building with construction fabric. The reactor building basement is flooded with 12 feet of radioactive water.
Four workers entered the Unit 2 reactor building for the first time since the earthquake. They did a survey of the building to map the radiation levels in order to plan the next tasks. The basement of the building and a piping tunnel are flooded.
130 tons (34,000 gallons) were pumped out of the Unit 3 reactor building yesterday lowering the level about 0.5 inches. There is about 56 inches of water remaining. Water was found to be leaking into the ocean on Monday. There was no status on whether the leak has been stopped. TEPCO has indicated the silt barrier for capturing some of the radioactive contaminants is not working. They are continuing to use zeolite to absorb the cesium.
The hydrogen explosion in the Unit 4 reactor building has now been attributed to hydrogen from Unit 3 which entered the building via a common duct. A video of the fuel in the Unit 4 spent fuel pool does not show the expected damage to the fuel which could have produced the amount of hydrogen needed to cause the explosion. The water level in the Unit 4 spent fuel pool is being maintained by the injection of water every other day.
Water is being pumped from the Units 5 and 6 buildings to makeshift tanks. This water is not highly radioactive.
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