Cooling of Fukushima Daiichi unit 2 has been upset by a
change in injection rates, leading to a rise in temperature that Tokyo
Electric Power Company (Tepco) is working to gradually correct.
Tepco has been injecting water into the reactor since 14 March 2011,
first using seawater and changing to fresh water 12 days later. Over
time, the accumulated decay heat produced by the reactor core was
gradually removed. By September 2011, Tepco had improved the water
injection method to include core spray systems as well as feedwater
injection, and temperatures fell below the landmark of 100ºC - and
eventually to about 50ºC.
This stability of unit 2 was disturbed for a few days, however, when
Tepco tried to improve cooling further by tuning the rates of water
injection. On 2 February, feedwater injection was reduced by two cubic
metres per hour and the core spray was stepped up by the same amount.
more in World Nuclear News
