One cooling pipe breach caused by earthquake, not tsunami | Japan Times

Thursday, May 26, 2011

Cooling pipe breach now laid to temblor

Reactor design rethink looms after Tepco damage report


Tokyo Electric Power Co. admitted Wednesday that one of the critical cooling pipes at its Fukushima No. 1 nuclear power plant’s reactor unit 3 may have been damaged in the March 11 megaquake.

Tepco suggested earlier that no major damage, including ruptures in the facility’s main steam pipes, had occurred at the reactor until the massive tsunami hit after the magnitude 9.0 quake.

But if the temblor had actually damaged the High-Pressure Core Flooder system — which is used to supply coolant water to a reactor core in emergencies to keep nuclear fuel from overheating — power suppliers across the country might be forced to reconsider the quake resistance designs for their reactors.

“If we do our analysis on the premise that there was a leak in the piping, it matches (data) in reality,” a Tepco official said at a news conference.

“We can’t deny the possibility,” the official added.

At the No. 3 reactor, a quake greater than anticipated under resistance guidelines occurred, knocking out electricity to the power plant and precipitating the current crisis.

The piping was housed in a building that was designed to resist direct damage from tsunami.

Another analysis by Tepco has shown that breaches may have occurred at containment vessels encasing reactors 1 and 2 at the power plant, possibly causing leaks of highly radioactive water there.

The possible breaches to the containment vessels there are certain to compound efforts to deal with accumulating contaminated water at the sites, raising questions about the viability of a Tepco plan to re-establish a stable cooling system by around mid-July.

Tepco said if it hypothesizes that a breach of about 3 cm wide occurred at the reactor 1 containment vessel 18 hours after the quake and widened to about 7 cm 50 hours later, that corresponds well to changes in pressure readings inside the containment vessel.

The utility also hypothesized that a breach roughly 10 cm wide occurred at the No. 2 reactor’s containment vessel 21 hours after the quake due to elevated temperatures, among other factors.

This finding also corresponds with data obtained.

Tepco also said it believes that parts used to ensure air tightness may have broken from overheating.

Projections halted

The Meteorological Agency has stopped providing projections of the spread of radioactive substances from the Fukushima No. 1 nuclear plant now that the International Atomic Energy Agency is no longer requesting them, agency officials said Wednesday.

The IAEA had asked for the projections to gauge the potential impact on other countries of radiation leaking from the nuclear plant following the megaquake and tsunami.

The projections were made up to three times a day immediately after the crisis erupted and, recently, three times a week in reports to the IAEA.

The Meteorological Agency had made the projections available on its website since April 5 as instructed by the government.

The IAEA terminated the request Monday night without specifying why and noted it could make a new request if there were any developments to warrant it, Japanese officials said.

However, the agency will not give projections unless the U.N. nuclear watchdog asks them to, the officials said.

The projection had been based on an assumption that 1 becquerel of iodine-131 is discharged from the nuclear plant every 72 hours. Projected concentration data did not reflect reality.


One cooling pipe breach caused by earthquake, not tsunami | Japan Times — 1 Comment

  1. For the ordinary people it matters little what caused the breach. They suffer.  

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