The temperature of the Fukushima No. 1 power plant’s No. 3 reactor is below 100 degrees, indicating that a cold shutdown may be within reach, Tokyo Electric Power Co. said Monday
It is the first time the temperature at the bottom of unit 3′s pressure vessel has fallen below 100 since the nuclear crisis was triggered by the March 11 earthquake and tsunami.
Reactor 1 is even lower — below 90 — but Tepco said it is too early to determine whether it achieved cold shutdown because it needs to re-evaluate the amount of fuel left inside.
Tepco said a new cooling method that involves showering the reactor core with water probably helped lower the temperature of reactor 3 and that it is considering applying the method to reactor 2 as well.
The cores of reactors 1 through 3 are assumed to have melted, and the fuel is believed to have sunken and solidified at the bottom of their pressure vessels.
The vessels must be below 100 degrees to achieve cold shutdown, which is defined by the government and Tepco as a state in which the release of radioactive materials is under control and exposure doses have been significantly reduced.