COLD COMFORT FOR FUKUSHIMA DAIICHI NUCLEAR POWER PLANT HAS BEEN OFFICIALLY RECOGNISED

Japanese prime minister Yoshihiko Noda announced the status of the reactors during a meeting to discuss progress on the accident, saying that the achievement is considered as achieving 'convergence' with Tepco's roadmap for mitigating the accident. In other words, the recognition of cold shutdown formally brings to a close the 'accident' phase of events at the plant triggered by the 11 March tsunami.

Reactors are usually considered to be in cold shutdown when core temperatures inside the reactor are lower than 100°C. This condition was actually met by all of the Fukushima reactors over two months ago. However, in the case of the damaged reactors, the status also required radioactive releases to be brought under control, with operator Tepco not able to declare cold shutdown until releases were brought to a minimal level.Tepco's roadmap had scheduled the achievement of cold shutdown by the end of 2011, although the stricken units were reported to be close to cold shutdown as long ago as October.

All of the reactors that melted down at the Fukushima nuclear plant are now officially in "cold shutdown".

The truth is, this announcement is far more symbolic than it is practical. For another few years at least, it seems likely that the reactors will have to be actively pumped with water while their radioactive fuel slowly decays away. Meanwhile, residents who once lived near the plant will have to wait while the land around it is decontaminated — a process that involves the laborious removal of millions of cubic meters of topsoil.

REFERENCES

 http://online.wsj.com/article/SB10001424052970204336104577096281099680526.html

http://www.nature.com/news/fukushima-reaches-cold-shutdown-1.9674

http://www.iaea.org/newscenter/focus/fukushima/

http://online.wsj.com/article/SB10001424052970204358004577033522244084162.