Official Announcement On Cold Shutdown of Reactors in Japan

Sunday, 18 December 2011 16:55

Written by Navid Iqbal

Finally, a declaration has come on Friday from the Japan government on Tokyo Electric Power Company (TEPCO). The 3 crippled reactors are now in cold shutdown condition at Fukushima plant no. 1 and no longer leaking huge quantity of radiation.

If the declaration is correct and a stable cooling system for the reactors is achieved, it would be a great milestone in finishing the world’s most hazardous nuclear disaster since Chernobyl crisis, 1986. But there are still lots of doubts. Many skeptics have given their opinion that the announcement is slightly extra than political showing off.

The meaning of a cold shutdown is that the coolant temperatures of reactor core are lower than hundred degrees so that the water is not in boiling condition and the radioactive materials are not evading in large amounts from the cores. The three reactors have been noticeably damaged and the maximum of the dissolved fuel is supposed to enter throughout the pressure vessels and fall down to the base of external containment vessels. Still, it is not possible for TEPCO to measure the actual hotness at the base of containment vessels, the government announced the three reactors are now in a condition of cold shutdown as the temperatures at the base of pressure vessels, that are inside of  containment vessels, are far lower than boiling point.

Authorities said that from Friday the atmosphere temperature at the lower area of those containment vessels of reactors 1, 2 and 3 were 38.9⁰ C, 167.5⁰ C and 57.4⁰ C respectively. According to TEPCO, this designates the total containment vessels, which is the last protection to hold radioactive materials from spreading out, have been reserved securely cool through insertion of the coolant water.

Nevertheless, levels of the radiation are still excessively high to clearly verify the real conditions of melted fuel supposed to take position at the base of the vessels.

But TEPCO is saying that no longer the melted fuel is too hot to go through the last concrete cover of containment vessels as a small amount of carbon dioxide has been discovered in the air inside those vessels.

TEPCO said that the rate of radiation leakage from the 3 reactors remains under 1 millisievert/year. This was also mentioned as one most important cause for the Japan government to announce the achievement of cold shutdown.

Yet, experts are worried about long-term constancy of the total coolant arrangement, which is inserting water inside the cores of the reactors, given the threat of another earthquake as well as tsunami.