Temperature at the Bottom of Reactor 2 RPV Slowly Going Down, For Now

after pumping the largest amount of water since March 11, 2011, the temperature at the RPV bottom went from 72.2 degrees Celsius at 5AM on February 7 to 66.7 degrees at 5AM on February 8.

According to TEPCO's handout for the press on February 7, 2012, TEPCO has been injecting the water at the rate of 13.5 cubic meters (or tonnes)/hour in the Reactor 2 Pressure Vessel:

• The amount of the core spray system injection water was increased from 3.7 m3/h to 6.7 m3/h at 4:24 am on February 7.

• The amount of the continuing feed water system injection is 6.8 m3/h.

On February 1, the total amount of water being injected to the Reactor 2 RPV was 9 cubic meters/hour.

By the way, Mainichi Shinbun reported (2/7/2012) that the margin of error of the thermometers on the RPV may be 20 degrees Celsius:

温度計は事故後、最大２０度の誤差が生じた。東電は冷温停止状態の定義が「圧力容器底部が１００度以下」であることから、誤差を最大に見積もって８０度を超えれば地元自治体に通報すると保安規定で定めている。東電の松本純一原子力・立地本部長代理は６日の記者会見で「炉全体としては十分冷えており、冷温停止状態の判断を見直す必要はない」と話した。

Thermometers exhibited the maximum 20 degrees Celsius error after the March 11, 2011 accident. Since the definition of a cold shutdown state is "to keep the temperature at the bottom of the Reactor Pressure Vessel at 100 degrees Celsius and below", TEPCO's safety regulation specifies that the local municipalities are to be notified when the temperature exceeds 80 degrees Celsius given the maximum margin of error. TEPCO's Matsumoto said in the press conference on February 6, "The reactor is sufficiently cooled, and there is no need to revise the judgment of the cold shutdown state."

So, the current temperature of 66.7 could be as low as 46.7, or as high as 86.7. That's comforting.

The ever-incurious TEPCO and the overseeing agency NISA simply pump more water into the RPV, instead of ever wondering what may be causing the temperature to rise.

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