TEPCO to Redefine Its Idea of "Criticality"

Tokyo Shinbun (11/7/2011) reports:

東京電力は六日、福島第一原発の臨界判定基準を見直す方針を明らかにした。経済産業省原子力安全・保安院に先月提出した報告書では、半減期の短い希ガスが検出されないことを条件としていたが、今月二日に２号機で自発核分裂により発生したとみられる放射性キセノンを検出。実態と合わなくなり、修正を余儀なくされた。

On November 6, TEPCO disclosed its policy to review the standard to determine whether criticality has happened at Fukushima I Nuclear Power Plant. The report the company submitted to the Nuclear and Industrial Safety Agency under the Ministry of Economy, Trade and Industry defined the condition of criticality as whether noble gas with short half life was detected. However, radioactive xenon was detected in Reactor 2 on November 2, which is thought to have been created by spontaneous fission. TEPCO's definition didn't match the actual situation, and the company has no choice but redefine what it considers "criticality".

　二日にキセノンを検出した際、東電は「臨界の可能性がある」と発表したが、その後、検出量が少なかったことなどから「自発核分裂によるものだった」と訂正していた。

When xenon was detected on November 2, TEPCO announced "There is a possibility of criticality". However, the company corrected it as "spontaneous fission" partly because the amount of xenon detected was small.

　東電の川俣晋原子力品質・安全部長は、六日の記者会見で「再臨界かどうかでは、大変心配をおかけした。報告書の改訂版を準備している。その中で見解を示す」と述べた。

TEPCO's general manager Kawamata said in the press conference on November 6, "We're sorry we've had you worried over whether re-criticality happened or not. We are preparing the revised report, and we will elaborate on our view in that report."

　十月十七日に保安院に提出していた「中期的安全確保」に関する報告書では、キセノンなど半減期の短い希ガスが検出されないことが臨界判定基準だった。

In the report submitted to the NISA on October 17 on ensuring security in medium-term, the standard to judge the occurrence of criticality was the presence or absence of noble gas with short half life, such as xenon.

If this is true, then whoever crafted the October report to the NISA didn't know how xenon is apparently generated in spontaneous fission inside a normal reactor; and TEPCO has been operating this nuke plant for almost 40 years.

(Note to officials in Vietnam, Turkey, and India: Are you sure you want to import the Japanese nuclear power plant system?)

Tweet