The temperature at the base of the No. 2 reactor at the Fukushima No. 1 nuclear power plant fell below 100 C for the first time since the March disaster, according to Tokyo Electric Power Co.
TEPCO said the temperature was 99.4 C at 5 p.m. Wednesday. This means TEPCO has brought the temperatures at the base of the Nos. 1 to 3 reactors at the crippled plant to below 100 C, meeting one of the two conditions for the reactors to be in a stable cooling state, known as cold shutdown.
Compared with the Nos. 1 and 3 reactors, it took more time for TEPCO to cool the No. 2 reactor. On Sept. 14, the utility started increasing the amount of water injected into the reactor gradually from three to four tons per hour. The company also introduced a new method of spraying water from overhead like a shower. As a result, the amount of water injected into the No. 2 reactor reached 10 tons per hour by Monday.
Achieving cold shutdown is a major milestone in the Step 2 phase of the government's road map to contain the nuclear crisis triggered by the March 11 earthquake and tsunami. The government aims to complete Step 2 within the year. Achieving this will allow the government to move ahead with its study on whether it should allow evacuees to return home.
In addition to bringing the temperatures below 100 C, TEPCO needs to curb the leakage of radioactive substances from the plant significantly--another condition of cold shutdown.
(Sep. 30, 2011)