Cabinet member Edano's explanation about the explosion at No.1 reactor at Press Conference: Steel Container [contains reactor core] is not damaged, No major radioactive leak detected, Next measure is already being implemented

• I’m going to explain our view about explosion occurred at15:36. 
• This is based on the explanations provided by TEPCO. 
• Container for the reactor’s core part is made out of steel. 
• And this steel container is covered by a thick layer of concrete wall and steel beams structure.
• The explosion blew away this concrete wall the exterior walls of the reactor building
• How the explosion happened?: inside of the reactor core, water level dropped too much. (Thus temp went up and more water turns into steam) 
• This steam leaked out to the space between container and concrete wall. 
• (?Somehow leaked steam turned into hydrogen?) 
• This hydrogen gas met with oxygen in that space 
• And caused massive explosion, blowing away concrete wall exterior walls of the reactor building

• But the steel container of reactor core is not damaged. 
• This has been confirmed. 
• Thus our view is that the explosion occurred was not a type of explosion which would release large quantity of radioactive substances. 
• We verified this by checking the radiation level measured at site.
• The level of radiation: at 15:36, when explosion happened: 1015 microSv
• at 15:40, it dropped to 860 microSv
• at 18:58, it further dropped to 70.5 microSv
• This means after the explosion, radiation level rather dropped continuously. 
• Also around 14:00, vent operation to release steam out of container started.
• It took time but opened vent finally at 16:00.
•  And ever since the pressure within the container has been dropping steadily.

• Thus, we can see that there is no major risk of massive leak of radioactive substances. 

• To prevent further damages, Tepco is going to fill the container with sea water. 
• Also to prevent reactor core from reaching another critical state, boric acid will be added to this sea water. [*boric acid will absorb neutron - and prevent nuclear/atomic chain reaction escalating into critical state.]
• At 20:20, this procedure actually already been starting. 

Japan mayor wants reactor near Tokyo decommissioned

Only 10 of Japan’s 54 commercial reactors remain operating seven months after the March disaster triggered a crisis at Tokyo Electric Power’s Fukushima Daiichi nuclear plant, as safety fears have left local authorities wary of restarting reactors once they go offline for routine maintenance.But Tokaimura Mayor Tatsuya Murakami was the first local official to call for scrapping a reactor altogether, warning that, if the wave that struck his village on March 11 had been slightly higher, the Tokai Daini reactor could have posed far graver danger than the Fukushima plant, as 1 million people live within a 30-km radius and it is much closer to Tokyo.A Tokaimura official said Wednesday that Murakami made his plea at a meeting the day before with nuclear disaster minister Goshi Hosono.”Shouldn’t the plant be decommissioned?” he was quoted as telling the meeting.The 33-year old reactor still has seven years before its operating license expires and Tokyo Electric Power Co had been counting on the 1,100-megawatt facility to help it make up for the 4,700 megawatts of lost power from the crippled Fukushima Daiichi plant.Prime Minister Noda has said that offline reactors under maintenance should restart once local authorities confirm they are safe, taking a softer line than his predecessor Naoto Kan, who concluded in March that nuclear power was no longer worth the risk after the world’s worst nuclear accident in 25 years.Japan’s nuclear plant operators are preparing to report the results of reactor stress tests to the country’s nuclear watchdog, the first step in a lengthy process that would ultimately require local authorities’ approval for restarts.Since the onset of the Fukushima crisis, Murakami has called on Japan to better care for residents who were forced to leave Fukushima prefecture because of the crisis and to stop operating old reactors given lax safety rules and a lack of contingency plans.Murakami was Tokaimura’s mayor in 1999 when a criticality accident at a Tokaimura uranium reprocessing facility resulted in two deaths, the worst nuclear accident in Japan until the Fukushima crisis.Japan Atomic Power, in which Fukushima plant operator Tokyo Electric Power is a major shareholder, brought its sole reactor at the Tokai Daini plant in Ibaraki prefecture to a state of cold shutdown on March 15.