Missing water located in the Unit 1 reactor basement

Unacceptably low levels of water within the unit 1 reactor pressure vessel have dogged TEPCO since the beginning of the crisis. After increasing rates of water injection for weeks on end with no appreciable increase in levels within the RPV or the containment vessel, Tepco engineers have been hard pressed to figure out where the water had gone. After initial reports that 3000 tons of water were 'missing', NHK now confirms that most of the water now occupies the unit 1 basement - and it's a whopping 4.2 meters deep.

Efforts to problem solve reactor woes are understandably difficult and dangerous, as seen by this recent chart of dose rates within the unit 1 reactor area.  The southeast corner is reading extremely high, as much as 2000 milliSievert/hour at one specific location.

In an interesting development, Tepco has plans to cover the unit 1 building with "a polyester sheet" that "will be attached to steel frames, enclosing the 50-meter-tall building. The company says the cover can withstand strong winds. TEPCO also says it will install a ventilator with a filter to capture radioactive materials that would otherwise be concentrated inside."

To minimize radiation exposure among its workers, the company says the steel frames will be pre-assembled as much as possible, shortening the set up time at the plant. Whether this tent and it's associated ventilation system will actually improve the working environment in unit 1 remains to be seen.  One thing it will certainly accomplish?  Block the public's view of what goes on at unit 1.

Update: You may want to pay attention to this development. Boric acid is now being injected into reactor 3, where temperatures have been rising and water levels have been falling. We need some follow up on that decision, and i hope it's not out of some fear of re-criticality.  Read the Tepco update here