Plant's Design, Safety Record Are Under Scrutiny

By NORIHIKO SHIROUZU and REBECCA SMITH

TOKYO—The design and safety record of the damaged power plant at the center of Japan's nuclear crisis are coming under scrutiny, even as authorities continue to struggle to keep its overheating reactors under control.

The Fukushima Daiichi nuclear power complex, where workers are battling to prevent dangerous releases of radioactive material, is Japan's oldest, with six reactors that all came online in the 1970s. The boiling-water reactors—an older nuclear technology—are housed in six square buildings lining a stretch of coast in northeastern Japan, giving the plant access to seawater if needed and making possible transporting heavy equipment by ship.

Reactor Monitor

View Graphics

Past Nuclear Incidents

View Graphics

The plant was central to a falsified-records scandal a decade ago that led its operator, Tokyo Electric Power Co., known as Tepco, to briefly shut down all its plants and led to the departure of a number of senior executives. Nuclear experts say that led to a number of disclosures of previously unreported problems at Fukushima Daiichi.

The plant's record after that information became available is consistent with the records of other Japanese plants, experts say, though any past incidents are likely to come under new scrutiny amid this crisis.

Any design issues that emerge will be studied closely by the industry as it pursues a planned global nuclear-power buildout. "The earthquake and tsunami we had last week both exceeded our engineering assumptions by a long shot," said Tetsuo Ito, head of Kinki University's Atomic Energy Research Institute, near Osaka. "The nuclear industry around the world probably will have to review how we set those assumptions in designing a nuclear power plant."

One area of scrutiny is the Fukushima Daiichi nuclear complex's back-up diesel-powered generators, which are below ground level and housed in secure rooms. The 13 generators are intended to kick in when the plant loses power.

Another is the proximity of the plant's six reactors to each other, as damage to one reactor contributed to damage to another, and their proximity hindered recovery efforts. The arrangement can be found at other plants to making moving equipment easier and keep the work force lower, said Mr. Ito, but now it looks like a "bad idea." "We need to strike a better balance of operational efficiency and safety," he said.

Terry Pickens, director of nuclear regulatory policy at Xcel Energy Inc. of the U.S., said there is no cookie-cutter reactor of the vintage of the Fukushima units because utilities in those days hired their own engineering firms and architects and customized designs. At Xcel's Monticello plant in Minnesota, diesel generators are kept as far apart as possible so that "a natural phenomenon isn't likely to take both of them out," said Mr. Pickens.

The Japanese plant lost power during Friday's earthquake. The three reactors in operation shut off automatically as designed, but a lack of electricity left workers unable to operate their cooling systems, leading to overheating. Tepco says the tsunami paralyzed all but one backup generator. Their fuel tanks, which were kept above ground, appear to have been washed away.

In a weekend briefing, Tepco Managing Director Akio Komori cited the elevation of the backup generators as one potential issue. A Tepco spokesman confirmed the remarks, adding that a full probe will have to wait while workers try to bring the reactors under control.

Another person familiar with the matter said the elevation of the generators may have been a flaw, though a fuller investigation is still needed.

A spokesman for Japan's Nuclear and Industrial Safety Agency, the nation's nuclear-power regulator, said Fukushima Daiichi's emergency generator design is "fairly prevalent" at other Japanese plants. The spokesman, Shigekatsu Ohmukai, disputed that the elevation of the diesel generators was a problem, saying the agency concluded the plant can withstand a certain size of tsunami. "Obviously the tsunami caused by Friday's earthquake exceeded our assumptions. That's the problem," he said.

In the U.S., where there are 23 similar reactors operated by 11 different companies, backup generators typically are housed in bunker-like buildings at ground level. They are designed with watertight fittings that are intended to keep water from floods or hurricanes out.

The Edwin Hatch plant in Georgia, operated by Southern Co., is "very similar" to units at Daiichi, said Jeff Gasser, Southern's executive vice president of nuclear operations. But emergency diesel generators are in a watertight building with 30-centimeter-thick concrete walls, between stalls holding generators. It has two per reactor and an extra, for a total of five generators for two reactors there. The plant stores the generators' fuel in underground tanks. The Hatch plant is about 20 meters above a nearby river.

Hiro Hasegawa, a Tepco spokesman in Tokyo, said other ways of situating the generator could pose problems. "The reactors are some 100 meters away from the shore, and the rooms that house those backup generators are fairly watertight," he said. "You could say we could've put them at a higher elevation, but that would make generators vulnerable to earthquakes."

"Obviously we have decided to keep the emergency diesel generators at a lower elevation by weighing those risks thoroughly," he added. "Hindsight is 20-20."

Prior to last week, the plant's worst-known safety incident occurred 33 years ago. Following the records scandal, Tepco revealed that an uncontrolled chain reaction occurred in 1978 in Fukushima Daiichi's No. 3 unit, when fuel rods fell into the reactor. The accident caused a nuclear reaction, the company said, though it quickly brought the situation under control.

Last year, the No. 2 reactor came to an automatic stop after problems with a generator resulted in a drop of the water level inside by about 1.8 meters. The company quickly restored the water level, it said.