Japan news, june 6.no.1 reactor vessel damaged 5 hours after quake

No.1 reactor vessel damaged 5 hours after quake
Japan's nuclear regulator says the meltdown at one of the Fukushima reactors came about 5 hours after the March 11th earthquake, 10 hours earlier than initially estimated by the plant's operator.

The government's Nuclear and Industrial Safety Agency on Monday issued the results of its analysis of data given to it by Tokyo Electric Power Company.

The report says the fuel rods in the Number 1 reactor began to be exposed 2 hours after the earthquake due to the loss of the reactor's cooling system in the tsunami. Its fuel rods may have melted down 3 hours later, causing the damage to the reactor. This means the meltdown occurred about 10 hours earlier than TEPCO estimated last month.

The nuclear agency also says a meltdown damaged the Number 2 reactor about 80 hours after the quake, and the Number 3 reactor 79 hours after the quake.

The agency's analysis shows that the Number 2 reactor damage came 29 hours earlier than the TEPCO estimate, and the Number 3 reactor damage came 13 hours later than in the utility's assessment.

The agency says the total amount of radioactive iodine 131 and cesium 137 released from the Numbers 1, 2 and 3 reactors for the 6 days from March 11th is estimated at 770,000 terabecquerels.

That is about twice the figure mentioned in April when the agency upgraded the severity of the accident to the highest level of 7 on an international scale.

The agency attributes the discrepancies to the assumption that radioactive substances might have been released from the Number 2 reactor containment vessel as well as from its suppression chamber.
Monday, June 06, 2011 21:03 +0900 (JST)