Tepco Says Fukushima Reactor Temperature Breaches Safety Limit

By Tsuyoshi Inajima - Feb 12, 2012 5:15 PM PT

Tokyo Electric Power Co. (9501) said the temperature in one of the damaged reactors at its Fukushima nuclear station rose to levels above safety limits even as it injected increased amounts of cooling water.
One of three thermometers indicated the temperature at the bottom of the No. 2 reactor pressure vessel rose to 89.2 degrees Celsius (192.56 Fahrenheit) as of 8:00 a.m. today, higher than the 80 degrees limit, Naohiro Omura, a spokesman for the utility, said by phone today. There are no signs of isotopes that would suggest the reactor has gone critical, and there’s been no increase in radiation around the site, the company said in a statement.
The other two thermometers showed temperatures of 32.8 degrees and 33.1 degrees at 8:00 a.m. local time, Omura said. The thermometers have a margin of error of as much as 20 degrees, he said.
Tepco and Japan’s government announced on Dec. 16 they succeeded in bringing the reactors into a safe state known as cold shutdown nine months after the March 11 earthquake and ensuing tsunami caused the worst release of radiation since the Chernobyl accident in 1986. Temperatures at the bottom of the No. 2 reactor vessel may have risen by about 40 degrees Celsius from 50.7 degrees Celsius since Feb. 1, even as the company increased the coolant being injected into the unit, raising questions about the validity the safety declaration.
“We think the thermometer may be faulty,” as the other two thermometers at the bottom of the vessel show temperatures are falling, said Omura. It’s also possible that unstable water flow into the unit may have kept the coolant from reaching part of melted fuel sufficiently, he said.
The utility increased the rate of coolant to 17.4 cubic meters per hour from 14.1 cubic meters per hour as of 3:30 p.m. yesterday, it said in the statement.
To contact the reporter on this story: Tsuyoshi Inajima in Tokyo at tinajima@bloomberg.net
To contact the editor responsible for this story: Amit Prakash at aprakash1@bloomberg.net
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