5 Avril 2012
"(mainichi Japan) April 05, 2012"
TOKYO (Kyodo) -- The operator of the Fukushima Daiichi nuclear power plant said Wednesday that the injection of nitrogen gas into three crippled reactors ceased for over 2 hours, although it detected no abnormalities that could raise fears of a hydrogen explosion.
Tokyo Electric Power Co. said the interruption occurred possibly because a filter of the supply device was clogged by dust as a result of strong winds seen from Tuesday evening. The nitrogen supply device also stopped in March.
Following checks, the utility, known as TEPCO, found that the device had stopped operating after sounding an alarm at 9:51 a.m. Wednesday. But it took about an hour for workers to realize that the injection of the gas into the Nos. 1 to 3 reactors had stopped as the alarm cannot be detected at the operation center in real time.
The workers noticed by chance through a web camera at the plant's operation center that the measuring gauge for injection was pointing to zero at 10:55 a.m. and resumed nitrogen injection from 12:29 p.m. using different equipment, Tokyo Electric spokesman Junichi Matsumoto told a press conference.
Matsumoto said he will examine if any improvement can be made in monitoring arrangements.
Nitrogen injection into the reactors is vital to prevent a hydrogen explosion, which could result in the further release of massive amounts of radioactive substances into the atmosphere. The step is intended to keep hydrogen inside the reactors' primary containment vessels at low levels.
Matsumoto indicated that the failure to inject nitrogen would not immediately raise fears of an explosion, saying that it could take 30 to 50 hours until hydrogen concentrations inside the vessels reach dangerous levels.
The Nos. 1 to 3 reactors suffered meltdowns in the early days of the nuclear crisis at the Fukushima plant, triggered by the huge earthquake and tsunami on March 11, 2011.