Recovery efforts continue at Japan's Fukushima nuclear plant

Washington (Platts)--21Mar2011/630 am EDT/1030 GMT

Pressure levels rose then stabilized Sunday in one of the crippled reactors at the Fukushima I nuclear power plant in Japan, government and industry officials said.

Plans being considered earlier Sunday to vent radioactive steam from the reactor to reduce pressure were deferred and workers will continue to monitor reactor pressure, Tokyo Electric Power Co. said in a statement Sunday afternoon local time.

Efforts continue to restore outside electric power to instruments and safety systems at the site's six reactors and spent fuel pools. The Japan Atomic Industrial Forum, the nation's nuclear industry group, said in an update that as of 10 pm Sunday local time (1300 GMT), an external power cable had been connected to the "distribution switchboards" at units 1 and 2. Efforts were continuing to restore external power to units 3 and 4. Fuel is still "partially or fully exposed" in units 1, 2 and 3, JAIF said, creating a risk of fuel damage, generation of explosive hydrogen gas and possible core melting.

Reactor pressure levels are "stable" at units 1 and 3, but is "unknown" for unit 2, JAIF said.

Injection of seawater to cool reactor cores continues at units 1, 2 and 3, Tepco said.

Cooling capability was restored Sunday to spent fuel pools at units 5 and 6, where temperatures had been rising, JAIF said. Emergency workers continued efforts Sunday to spray water into the pools at units 3 and 4 and that had some effect, it said without providing details. Seawater "injection" continues at the unit 2 pool and is being "considered" for the unit 1 pool, the group said.

Chief Cabinet Secretary Yukio Edano suggested at a briefing Sunday local time that the Fukushima reactors will never be restored to operation.

"As the government has [nuclear energy] authorities, it's difficult for me to say anything definite before following the appropriate procedures," Edano said according to a report by Australian ABC News.

"Looking at the plant from an objective point of view, I think it's clear in a way if the Fukushima Daiichi plant is in a state of being able to function or not," Edano said. "I hope you can get it from the way I said it."

US Nuclear Regulatory Commission Chairman Gregory Jaczko said in an interview on C-SPAN Sunday that the most urgent priority remains restoring reliable cooling to Fukushima's reactors and spent fuel pools.

He declined to assess the plant's current safety status, saying "it's still a very difficult situation."

Jaczko also declined to comment on a New York Times report Saturday that said Tepco executives may have "wasted precious time in the early hours of the nuclear crisis, either because of complacency or because they did not want to resort to emergency measures that could destroy the valuable plant."

The story quoted Kuni Yogo, formerly an atomic energy policy planner in Japan's Science and Technology Agency, as saying he believed Tepco executives "did not recognize the risks soon enough. They failed to cool the reactors on the day of the earthquake, March 11, and even after a hydrogen explosion the following day, they waited more than four hours to start dousing the reactors with seawater. They did not even try to put water into the spent fuel pools for several days."

Jaczko said only that "we will have an opportunity when the crisis is resolved to go back and see how decisions were made."

The US NRC is conducting short-term and long-term safety reviews to determine what issues the Fukushima accident raises for the US fleet of 104 nuclear power reactors, roughly a fourth of which are similar in design and vintage to the stricken Japanese units. The NRC staff will brief the commission Monday morning on the accident.

Much more detailed information on the events in Japan will be available to inform the long-term NRC safety review, which will take "several months," Jaczko said.

FRENCH REGULATOR SAYS JAPANESE SITUATION STILL 'PRECARIOUS'

The situation at Japan's Fukushima I nuclear power plant "remains serious and precarious," Olivier Gupta, deputy director general of France's nuclear safety authority ASN, told journalists in Paris Sunday morning local time.

Gupta said the most serious short-term danger was at the plant's unit 3 reactor, where Tepco had earlier in the day planned to vent the reactor vessel to relieve mounting pressure without knowing for sure whether the pressure suppression pool at the bottom of the containment was intact.

"If the pool is too damaged, the [radioactive] releases will not be filtered" before attaining the atmosphere, Gupta said. The pool is designed in normal operation to trap radionuclides via a bubbling mechanism before the containment gases are vented. Tepco said that the proposed venting would release radioactive materials totalling [6.5 Exabecquerels], "which surpasses the standard for a serious accident," he said.

France's Institute of Radiological Protection and Nuclear Safety on Thursday estimated that radioactive releases from the Fukushima plant so far were about an order of magnitude lower than that. Most of the releases have been from voluntary venting of the reactors at units 1, 2 and 3 to prevent pressure from building up inside. Up to now, all those releases have been filtered.

Gupta said that although Tepco was doing what it could to restore power and cooling to the stricken reactors and spent fuel pools at Fukushima, "the situation from a technical viewpoint has not changed significantly for several days."

Gupta added that the situation cannot be considered stabilized until Tepco has restored more permanent power supply and more lasting means of cooling the units than those being used now.

--Steven Dolley, steven_dolley@platts.com

--Ann MacLachlan, ann_maclachlan@platts.com

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