Not enough water to cool the reactors - Why?

August 31, 2012

Fukushima reactors briefly did not get enough coolant water: TEPCO

http://mainichi.jp/english/english/newsselect/news/20120831p2g00m0dm023000c.html

TOKYO (Kyodo) -- The operator of the Fukushima Daiichi nuclear power plant said Thursday that the amount of water injected into the crippled Nos. 1 to 3 reactors temporarily dropped below the level regarded as necessary to keep the fuel inside cool.

Tokyo Electric Power Co. said the drop in the volume of the water did not affect the temperature of the reactor pressure vessels, while adding that the company is investigating the cause of the incident.

The utility known as TEPCO noticed that the three reactors were not getting enough water injection at 3 p.m. Thursday. Workers took measures to increase the water volume and they confirmed at about 4:30 p.m. that it recovered to the necessary level.

The Nos. 1 to 3 reactors need water injection between 4.3 tons and 6.1 tons per hour, but the volume stood at between 4.0 and 5.6 tons per hour at 3 p.m.

The three reactors suffered meltdowns in the nuclear crisis, triggered by the March 2011 massive quake and tsunami.