Experts say long distance would dilute harmful exposure
By CLIFF PFENNING, The Portland Observer
In the wake of the devastating 9.0 earthquake and resulting tsunami that struck Japan Friday, world, national and state health officials have said the threat of significant levels of nuclear radiation from a stricken nuclear power complex reaching the U.S. is extremely low.
An explosion Monday night caused health officials in Japan to order more than 150,000 residents to remain indoors due to concerns about radiation poisoning, but Japan’s Chief Cabinet Secretary said Tuesday that radiation readings outside the power plant were close to not being considered harmful.
The Nuclear Regulatory Commission said this weekend the threat of radiation exposure to the West Coast of the United States remained extremely low, as did Dr. Mel Kohn, the director of the Public Health Division for Oregon.
Changing wind patterns as well as the upper atmospheric jet stream are significant factors in radiation reaching or not reaching the U.S.
The wind direction over the past few days caused at least some radiation to reach the USS Ronald Reagan, a nuclear-powered aircraft carrier, which was 100 miles of the Japan coast. Sensors detected airborne radioactive particles that were estimated at 30 times the normal radiation experienced from the environment.
For radioactive particles to reach the U.S., air currents would require them to be deposited into the upper atmospheric jet stream, which would involve the kind of explosion than seems highly unlikely at the Fukushima Daiichi plant says Kathryn Higley, head of the Oregon State Nuclear Engineering and Radiation Health Physics department.
“For any particles to reach the U.S., they would have to reach into the upper atmosphere and that would require a significant event that would need to generate a lot of heat,” Higley said Monday. “Of course, once it gets up there, it can stay up there for some time, but even then it’s going to be mostly cleaned up simply by rain.”
Higley said the atomic bombs dropped on Hiroshima and Nagasaki in 1945 would have been far more likely to have deposited radioactive particles that might have reached the U.S. simply because the plumes that were created by the blasts.
“Even then, you’d get more radiation exposure from a chest X-ray than you’d get from that,” she said, noting that a person would need hundreds of X-rays to develop cancer.
The threat of nuclear radiation caught the world’s attention in 1979 when the core of one of the two units at the Three Mile Island nuclear plant in Londonberry, Pa., suffered a meltdown, which resulted in the threat of radiation exposure for thousands of nearby residents and livestock.
In 1986, the nuclear reactor at Chernobyl in the Ukraine, experienced a much more severe explosion and large-scale radiation fallout that caused more than 300,000 residents to be resettled. The nearby city of Pripyat was abandoned.
Higley said the Chernobyl disaster, though, showed how nuclear fallout is restricted.
“That was a significant disaster, but exposure to radiation was contained to the surrounding areas,” she said. “Even at Chernobyl, the explosion did not send particles high enough for them to travel great distances.”
At the time of the Three-Mile Island and Chernobyl accidents, Oregon received power from the Trojan nuclear facility located in Rainier, where protests had begun as early as 1977, two years after its construction.
The Trojan plant produced as much as 12 percent of the state’s energy needs at one point, but it had several design problems that caused it to be shut down at least once. Portland General Electric shut the plant down permanently in 1992 following a release of documents that showed a number of scientists believed the plant might not be safe to operate.
Decommissioning began in 1993.
Nuclear power continues to be a significant resource for power-hungry nations despite the threat of accidents.
Although one study showed infant mortality rates to be higher in areas downwind of the Three Mile Island plant, a 1999 report by a Columbia University epidemiologist found that no deaths or significant long-term health problems were associated with the accident.
The plant at Three Mile Island remains operational and is expected to continue operations through 2034.