Network of sensors across U.S. monitors possible fallout

March 17, 2011 at 12:00a.m.

Los Angeles Times

LOS ANGELES

A network of sensors is watching and waiting for the first sign of nuclear fallout from the crippled Japanese reactors at the Fukushima plant 5,000 miles away.

Operated by the U.S. Environmental Protection Agency, the network — known as Radnet — is a system of 100 radiation monitors that operate 24 hours a day, spread across the United States.

The system is part of a much-larger interagency federal plan for emergencies having to do with radioactive releases. That plan is now in high gear, even as federal officials simultaneously try to calm the U.S. public over fears that fallout from Japan’s nuclear disaster will hit American shores.

The Nuclear Regulatory Commission, which oversees the nuclear industry, again said Wednesday that it does not expect dangerous levels of radioactivity to hit the West Coast of the U.S. But at the same time, it sharply raised its warning to American citizens — instructing them to evacuate at least 50 miles from the Fukushima complex.

The NRC released computerized projections showing that within a half-mile of the plant radiation levels were so high that people could receive a fatal dose and that even 50 miles away, they could receive more than 16 times the average annual dose individuals are exposed to from natural sources.

Those numbers were sharply higher than ones the NRC released in earlier days. But although the reactors are leaking more radiation now, experts continued to say that the particles would wash out of the atmosphere before they could reach the U.S.

So far, Tokyo Electric Power Co., which operates the Fukushima No. 1 facility, and the Japanese government have not released any measurements or estimates of the total amount of radioactivity released by the accident. These numbers would be critical to better projections of whether the material could affect other Asian nations, the Pacific islands or even the U.S.

Edwin Lyman, a nuclear specialist at the nuclear watchdog group Union of Concerned Scientists, said that although it’s true that the more radioactivity released in Japan the more could migrate away from the region, but he does not think the U.S. is at serious risk.

“We can never say never,” Lyman said. “My judgment is that there will probably be measurable radiation, but except for a few hotspots it is not something we should really worry about.”

Lyman noted that the NRC’s warning Wednesday to Americans in Japan to evacuate 50 miles from the Fukushima reactors is a long overdue admission that their prior warnings of a 10-mile exclusion zone from U.S. reactors during an emergency was inadequate.

Key federal officials involved in the monitoring program have so far not disclosed their predictions for U.S. radioactive exposure. The projections are being developed by the National Atmospheric Release Advisory Center operated at the Lawrence Livermore National Laboratory. This center, part of the Energy Department, uses sophisticated models on supercomputers to project the movement of radioactive particles and other toxic substances through the atmosphere.

However, a computer model of atmospheric currents developed by the Belgian Institute for Space Aeronomy shows that the Fukushima plumes theoretically can travel across the Pacific, though the levels of radioactivity that could reach the U.S. remain unclear.

The models show that even with prevailing easterly winds, the plumes whip back and forth over a wide area of Japan’s east coast, Russia’s Kamchatka Peninsula and the Aleutian Islands. It is unknown whether nuclear fallout is hitting the vast wilderness of north eastern Asia.

A leading radiological health expert at the Centers for Disease Control and Prevention, speaking on background, said Wednesday that the CDC is still confident that there will no serious health consequences in the U.S. But they are watching the situation carefully.

“We have a saying: ’Modeling is OK, but measurement is everything,”’ he said.

The Environmental Protection Agency said that it is watching the situation closely, but that its Radnet system has not yet detected radioactivity. It has added seven additional portable radiation monitors: two in Guam, three in Alaska and two in Hawaii.

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