Radiation from Japan’s worsening nuclear crisis wasn’t detected in Hawaii yesterday, with the U.S. Environmental Protection Agency saying monitors here showed only normal background levels "thousands of times below any conservative level of concern."
The measurement came as radioactive fallout from Japan’s stricken reactors hit the West Coast as it was carried east on the high-altitude jet stream, and Hawaii residents watched closely for indications of radiation here.
The EPA said it has its "RadNet" network of radiation monitors deployed. The U.S. Department of Energy also has been monitoring. Neither system detected "any radiation levels of concern."
A monitoring station in Sacramento, Calif., did detect "miniscule quantities" of the radioactive isotope xenon-133, and the origin was determined to be consistent with a release from the Fukushima reactors in northern Japan, the two agencies said in a joint release.
The levels were approximately one-millionth of the dose rate that a person normally receives from rocks, bricks, the sun and other radiation background sources, the agencies said.
"These types of readings remain consistent with our expectations since the onset of this tragedy, and are to be expected in coming days," the statement said.
U.S. Energy Secretary Steven Chu said Wednesday that a partial nuclear meltdown had occurred at Fukushima. The severity of the damage and radiation release was upped by Japan to a 5 on a 1-to-7 international scale yesterday, putting it on par with the Three Mile Island accident in 1979. Chernobyl ranks as a 7.
The National Weather Service in Honolulu said yesterday that the core of the jet stream — high-speed winds that circle the globe from west to east, and generally north of Hawaii — didn’t dip down to Hawaii for the past several days and are not expected to do so in the next several days.
The winds travel at 18,000 to 35,000 feet in altitude and at speeds of more than 200 mph, the weather service said. The jet stream periodically extends south to Hawaii in the winter, forecaster Derek Wroe said.
"It would be very rare for the typical jet stream that we talk about to dip down this far south as you get out of the wintertime," Wroe said.
The EPA operates RadNet detectors on Oahu and the Big Island. Its readings are accessible at www.epa. gov/cdx.
Two additional RadNet detectors are expected to be in place on the North Shore and on Kauai this weekend.
The average person is exposed to about 620 millirems of radiation a year. People who work around radioactive material are limited at 5,000 millirems per year, the American Nuclear Society said.
According to the organization, a chest X-ray is 10 millirems, flying in a jetliner exposes a person to 0.5 millirems per hour and radon in the air can reach 228 millirems a year.
A television and computer screen can mean exposure to 1 millirem, and food and water contribute 40 millirems per year.
Donald Olander, professor emeritus of nuclear engineering at the University of California at Berkeley, downplayed the potential radiation risk to Hawaii from the overheating Japanese reactors.
"Even if there’s a really severe meltdown of the Chernobyl type — which I really don’t think is going to happen — the level of drift you get over there will just be barely readable," Olander said.