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Quake-resistance of No.1 reactor questioned

July 7, 2012


Reactor 1 quake-damaged?

Diet panel hits Tepco assumption that only tsunami killed power





Staff writer

The 9.0-magnitude quake that rocked the Fukushima No. 1 plant in March 2011 may have knocked out one of the emergency generators at reactor 1 before the site was engulfed by tsunami, according to a Diet panel's final report on the nuclear crisis.


The independent panel's findings, released Thursday, challenge Tokyo Electric Power Co.'s assertion that the tsunami single-handedly disabled all the plant's emergency power generators and that the massive temblor wasn't directly responsible.

If the diesel generator at the No. 1 reactor was crippled by the megaquake, this would seriously undermine Tepco's claims that the Fukushima No. 1 complex survived its initial impact and also question the quake-resistance of many other old reactors nationwide.

The government and Tepco should not assume that a "total power loss would have been averted if not for the tsunami," the panel stated in the report.

The power outage halted the critical cooling function in reactor cores, which led to three of the plant's units suffering meltdowns and emitting massive quantities of radioactive materials into the environment.

The panel suggested that some of the emergency generators at reactors 2 and 3 also might have been knocked out by the quake.

Tepco has consistently claimed that the initial tsunami that smashed into the power station at 3:35 p.m. on March 11 knocked out all the emergency generators, resulting in a total power outage.

But the panel pointed out that a wave gauge set up about 1.5 km off Fukushima's coast recorded the first tsunami sweeping by at exactly 3:35 p.m., and estimated that it would have taken at least two more minutes for it to reach the No. 1 plant.

This would mean that the power generators were knocked out sometime after 3:37 p.m.

But it is believed the power generator in question was disabled between 3:35 p.m. and 3:36 p.m., implying the quake rather than the waves was responsible, according to the report.

Reactor 1 had two emergency diesel generators in the basement of its turbine building. Given the massive flooding caused by the tsunami, the generator would still have ceased working eventually, even if it had survived the quake's impact.

But if the panel's findings are correct, tsunami safety measures alone might not have been enough to prevent the loss of emergency power, and therefore the meltdown at reactor 1.

On Thursday, Tepco spokesman Junichi Matsumoto reiterated the utility's view that all the generators at the plant were disabled by the first tsunami that washed ashore, citing the results of worker interviews.

"We did not hear that the diesel generator had stopped before the tsunami," Matsumoto told a new conference Thursday evening.

Unfortunately, it still remains impossible to verify which account is correct.

Sky-high radiation levels inside the plant's wrecked reactors, including the No. 1 unit, have prevented Tepco and the government from sending any workers inside the turbine buildings to visually inspect the damage and determine what actually caused the generators to stop functioning.

The report also pointed out that as Tepco, the Nuclear and Industrial Safety Agency and another independent panel created by the government to probe the nuclear disaster have all assumed the emergency power loss was caused by tsunami, no efforts have been made to further examine the matter.

"(That is) very regrettable, and (the investigators' findings) are insincere," the panel stated in the report.

Financial hit


The three Tohoku region prefectures hardest hit by last year's devastating earthquake and tsunami took an estimated ¥1.54 trillion hit to their economic output after losing seaside factories and other infrastructure, a government white paper said Friday.

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