Washington (Platts)--13Mar2011/827 am EDT/1227 GMT

Japan, the most disaster-ready nation in the world, is struggling to cope from the massive 8.9-magnitude earthquake and the resulting tsunami that hit it on Friday. One of the major outcomes of the quake is the radiation threat from its largest power utility Tokyo Electric Power Company's Fukushima Daiichi nuclear plant.

Tepco began injecting sea water into a reactor at the Fukushima Daiichi nuclear power plant Saturday in an effort to maintain cooling of the unit, which lost power after the tsunami.

Tepco reported Saturday higher-than-normal levels of radioactivity at the site but did not provide numbers. Some people being evacuated from near the plant have been confirmed to have been exposed to radiation above the threshold considered low by Japan's Nuclear and Industrial Safety Agency.

Earlier, the International Atomic Energy Agency said radiation levels at the plant, which rose earlier, had fallen.

The effort to use sea water at the coastal plant to cool the Fukushima Daiichi reactor core was "an act of desperation," said Robert Alvarez, a senior scholar at the Institute for Policy Studies in the US and a former Department of Energy official. The effort may reflect a loss of water circulation capacity at the site, Alvarez said in a conference call sponsored by the anti-nuclear organization Nuclear Information and Resource Service.

Tepco said in an update on its website Saturday that injection of sea water into the reactor core, followed by addition of boron, which is used to reduce the rate of nuclear fission, began at 8:20 pm local time (1120 GMT) local time. The effort was later halted because of concerns about another possible tsunami brought on by an aftershock, Tepco said.

The utility said it shut all its seven operating power reactors at Fukushima after the earthquake. The six-unit Fukushima Daiichi station lost power, and emergency diesel generators that were designed as a backup failed about an hour after the earthquake, possibly because of the tsunami.

The government ordered the evacuation of residents living within 20 kilometers (12.4 miles) of Fukushima Daiichi, widening the area from the initial 3 km.

NISA has confirmed the presence of radioactive cesium-137 and iodine-131 in the vicinity of the plant, the IAEA said on its website.

The presence of cesium could be an indication of damage to the fuel in the reactor, Alvarez said.

The explosion at the Fukushima plant affected the concrete building that covers the top of the reactor's steel containment vessel, which remains intact, the IAEA said.

The cause of the explosion is unclear, but could have been an accumulation of hydrogen in the concrete building from the interaction of fuel cladding materials and water, former US Nuclear Regulatory Commission member Peter Bradford said during the NIRS call. That hydrogen could have been vented into the containment vessel and then migrated to the building where it could ignite when mixed with oxygen, he added.

The accident could significantly reduce public support for nuclear power around the world, Bradford said.

The nuclear industry will examine the root causes of the accident and seek to learn from it, Nuclear Energy Institute spokesman Tom Kauffman said Saturday.

"The world nuclear industry will be paying close attention to this," he said. Tepco and its workers have done "a heroic job" attempting to control the reactor, he added.

Dale Klein, a former chairman of the NRC, said in an interview Saturday that using seawater to flood Fukushima Daiichi's reactor core -- and containment as a precautionary measure -- is part of the plant's emergency planning process. "If you're near the end of your options, that's one of them," he said.

Klein said such a procedure leads him to believe the condensate tank was broken or empty or the pipes leading to it were broken because it would have been used otherwise. The condensate tank is used to provide water to the emergency core cooling system.

Klein, who chaired the NRC from July 2006 to May 2009, said future operation of the reactor "would be an economic decision that Tepco would have to make." But he expected the company to consider building a new one instead as "it would be a major cleanup of contaminated components and water."

The 460-MW unit 1 at Fukushima Daiichi began commercial operation in 1971 and is the oldest and smallest of the Fukushima reactors. Klein said he would characterize the quake impact on Fukushima-1 as "more like a Three Mile Island [but] with a lot more knowledge."

Operators at the Japanese unit "knew early on what they had to do, they just had trouble doing it," he said.

At the Three Mile Island-2 unit in Pennsylvania on March 28, 1979, operators mistakenly turned off the emergency core cooling system, which had automatically activated, because they believed the core was covered. The accident, in which there was a partial core meltdown, is considered the worst in US commercial nuclear power plant history but led to no deaths or injuries to plant workers, according to the NRC.

The workers at Fukushima-1 set up emergency diesel generators to provide backup power for the cooling system, but they apparently ran for only a short time before being damaged by the tsunami, Klein said. Backup power could have been provided by batteries but that typically lasts only a few hours, and damage to the surrounding area appears to have cut off the option of bringing in additional emergency diesel generators, he said.

"The earthquake had minimal impact; the tsunami had the impact," Klein said.

The problem in cooling Fukushima Daiichi was officially rated an accident on the IAEA scale Saturday, with a rating of 4 on the International Nuclear Events Scale, an accident with local consequences. Events can be rated from 1, an anomaly, to 7, a major accident.

The explosion of a reactor at the Chernobyl nuclear plant in Ukraine in 1986 was a level 7 event; the partial meltdown of the core at Three Mile Island-2 was rated 5, IAEA said.

Japanese authorities were reportedly planning to distribute potassium iodide tablets to residents around the plant. In the event of a radiation release from an accident, potassium iodide can protect the thyroid gland from possible radiation damage by blocking the absorption of radioactive iodine.

The Fukushima Daiichi reactor is a boiling water reactor or BWR design that has a large number of ways to get cooling water into the core, Ken Bergeron, a physicist and former Sandia National Laboratory scientist, said on the NIRS call. The design counts on steam-driven components that do not require offsite power except for controls, he said.

"They have a lot of options and they're using them now," Bergeron said.

But the small metal containment vessel in which the reactor is located does not present as much protection in case the core of fuel rods should melt, Bergeron said. Unlike the containment at Three Mile Island-2, that of Fukushima Daiichi might not survive a core melt, he added.

Nuclear reactors have various barriers -- including the containment building, reactor vessel and fuel cladding -- aimed at preventing the release of radioactivity in case of an accident or a terrorist attack.

The NRC is sending two BWR specialists to Japan as part of a delegation of US Agency for International Development workers. NRC has some of the top experts in BWRs and will assist Japan as much as possible, Chairman Gregory Jaczko said Saturday in the statement.

--William Freebairn, william_freebairn@platts.com --Tom Harrison, tom_harrison@platts.com

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