RICHLAND — As Japan faced the possibility of partial meltdown inside multiple nuclear reactors following Friday’s earthquake and tsunami, officials in the U.S. were assuring the public of the safety of reactors here.
U.S. nuclear plants are designed to have maximum earthquake protection, said Sen. Maria Cantwell, D-Wash., as she visited Richland on Saturday.
The Northwest’s only nuclear power plant, Energy Northwest’s Columbia Generating Station, is 10 miles north of Richland.
The Energy Northwest plant was designed to withstand a magnitude-6.9 earthquake near the plant, such as at Rattlesnake Mountain, said Brad Sawatzke, the plant’s chief nuclear officer.
Earthquakes more than magnitude-3 are uncommon in the area. There was a magnitude-3.8 earthquake close to Hanford in the 1970s. That’s large enough that it might shake objects off a shelf but should not cause structural problems in an ordinary building.
There also was a 3.7-magnitude earthquake in the Horse Heaven Hills south of Benton City in 2008.
In the region, the largest earthquake recorded was a 5.7-magnitude earthquake 72 miles from Hanford at Milton-Freewater in 1936, according to data collected for design of the Hanford vitrification plant.
The earthquake in Japan was a magnitude 8.9, but it appears that the Tokyo Electric Power Co. Fukushima No. 1 facility, the first reactor to have trouble, also was hit by the double punch of a tsunami.
The reactor automatically shut down when the earthquake hit, but then there were difficulties powering the system to cool down the fuel rods.
Some news reports indicated that the tsunami damaged the backup diesel generators, although the Nuclear Energy Institute said that had not been confirmed.
“It was an incredibly worst case (event),” Sawatzke said. Not just one natural disaster, but an earthquake and an tsunami hit the plant, he said.
“The real challenge in Japan appears to the be tsunami,” which would not be a problem at the inland Columbia plant, he said.
The Columbia Generating Station is a General Electric boiling water reactor like the Fukushima plant, but is more than a decade newer and with a design that has an improved and stronger containment dome.
It has a similar set of backup systems that starts with a diesel-generated power in case off-site power to the plant is lost. It also has batteries available.
Then it has a steam-driven turbine that could be used if power were lost to get cooling water into the reactor, Sawatzke said. The Nuclear Energy Institute said the Japanese reactor does not appear to have that capability.
“Our design and the way we operate the plant is safe for the public,” Sawatzke said.
In addition, U.S. reactors have severe accident management plans that anticipate serious events and lay out formal procedures to deal with them, said Steve Kerekes, spokesman for the Nuclear Energy Institute.
Japan has a strong nuclear safety program, but the United States has the strongest in the world, he said.
The Japanese government used the International Atomic Energy Agency’s International Nuclear and Radiological Event Scale on Saturday to give the problems of the Fukushima plant a level 4 rating, according to the Nuclear Energy Institute. That indicates an accident with local consequences.
The 1979, Three Mile Island accident had a level 5 rating, and the 1986 Chernobyl disaster had a rating of 7, the highest on the scale.
In the Three Mile Island accident, the maximum exposure to the public was 70 millirems after half the reactor core melted, Kerekes said. That compares to 300 millirems the average person receives annually from natural background radiation.
The Chernobyl disaster was in a plant that produced nuclear power, but was designed more like a weapons-production plant than those used in the United States for power production, according to Energy Northwest.
As of Saturday evening, it appeared that releases of radiation in Japan were small enough that they would not harm the public’s health, Kerekes said. The public was being evacuated in a zone extending about 12 miles from the plant.
Oregon and Washington were monitoring for radiation as a precaution, each said Saturday. Air samples were normal, as expected.
“Even in the event of a significant release from the reactor, radiation would be diluted before reaching our state and levels would be so low no protective action would be necessary,” said a statement from the Washington State Department of Health.