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Radiation truth: there is no threshold below which risk is zero

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Anti-nuclear demonstrators from Bosnia hold a banner with text 'We do not want another Chernobyl on Balkans' during a protest marking the 25th anniversary of the nuclear accident in Chernobyl in western town of Banja Luka 240 kms northwest of the Bosnian capital of Sarajevo, on Tuesday, April 26, 2011. Bottom text reads "better to be active today then radioactive tomorow". Photo: AP/Radivoje Pavicic

The Bulletin of the Atomic Scientists has published an article titled ‘Radiation exposure and the power of zero’. This talks breifly about the history of medical work with radiation, and the fallacy – alas not challenged enough – that there is no such thing as “safe” levels below which one is not harmed.

In 1895, the article recounts, Wilhelm Röntgen discovered x-rays and used them to take a picture of the bones inside his wife’s hand. A year later, Henri Becquerel realized that invisible emanations from uranium salts would expose photographic plates. Marie Curie and her husband Pierre carried this work further, leading to the use of mobile x-ray machines in World War I.

Madame Curie, it is said, enjoyed the glow from radioactive test tubes that she kept in her desk. She died at age 66 from aplastic anemia thought to be caused by her work with radiation. Were she alive today, she would undoubtedly follow the precautions that modern scientists take when dealing with radiation, and would not be carrying around radioactive material unprotected. Likewise, radiologists began taking steps to protect themselves from the damaging effects of radiation after noticing that people in this profession were dying at earlier ages than their colleagues who were not exposed to radiation.

[You can go to earlier coverage of the Fukushima nuclear emergency on this page. It contains excerpts, news reports, photos, graphics and links during the first weeks of the crisis.]

South Korean mothers stage an anti-nuclear energy rally to protect their children from radioactive exposure in Seoul, South Korea, Tuesday, April 19, 2011. Fears over possible radiation contamination are growing in South Korea, the country closest to Japan, after Japanese nuclear power plants were damaged by earthquakes last month. Photo: AP/Ahn Young-joon

Yet even in the 1970s it was common medical practice to x-ray pregnant women during labor to see if the pelvis was “adequate” — a procedure, incidentally, that was absolutely worthless. Sentinel work by Alice Stewart, a physician and epidemiologist who studied the effects of radiation on health, revealed that even one x-ray before birth could increase a child’s chances of getting leukaemia. Despite criticism of Stewart’s work by the nuclear industry, doctors no longer perform x-rays on pregnant women unless absolutely necessary. The trend throughout the nuclear age has been a growing recognition that there is no “safe” or “harmless” dose of radiation.

In 2006 the National Academies’ National Research Council published a comprehensive report, “Health Risks from Exposure to Low Levels of Ionizing Radiation (BEIR VII – Phase 2)” stating that radiation exposure has a linear relationship to the development of cancer. The report concluded that even low doses of ionizing radiation are likely to pose some health risks; there is no threshold of exposure below which the risk drops to zero.

Scientific arguments regarding the effects of particular doses of radiation will and should continue. However, to make this the focus of any discussion of nuclear safety obscures the real issue, thus missing the forest for the trees. The real issue is that the use of nuclear power and nuclear weapons is forcing humankind, and indeed the whole ecosystem, to participate in a particularly cruel and totally uncontrolled experiment. Given the scientific evidence that there is no safe dose of radiation, this is an experiment that has already gone awry. Indeed, if this were a true scientific experiment, it would have been halted a long time ago.

The Bulletin’s article, ‘Radiation exposure and the power of zero’, concludes by saying:

The real question is whether we, as a human race, can afford in good conscience to risk annihilation with our continued reliance on nuclear technology. Can we continue to despoil our environment with long-lived radioactive materials that are scattered to the wind and embedded in our precious soil, randomly exposing large populations, and foisting health impacts on unsuspecting future generations who have no choice in this matter?

We may choose to do so. But if we do, I am quite sure that our children and grandchildren will roundly condemn us for our lack of foresight and our selfishness. As they struggle to deal with a poisonous environment and waste that must be safeguarded for thousands of years, they will certainly wonder what possessed us to do this.

Around 900 demonstrators gather to protest against nuclear power in Helsinki on Tuesday, 26th April, 2011. The day marks the 25th anniversary of the Chernobyl nuclear disaster in 1986. Banner reads: Finland get rid of nuclear power. Photo: AP/Lehtikuva, Antti Aimo-Koivisto

One question in particular demands attention: Why was the actual event in Japan, an earthquake and tsunami, so different from the “credible” event that was expected?

Also in the Bulletin, the first of a contribution to a roundtable on ‘Fukushima: What don’t we know?’ starts to provide an answer. From our perspective as geoscientists, the article has said, this is the most important question because the definition of the credible event provides the basis against which a nuclear power plant is designed. In the case of the Fukushima Daiichi power station, the magnitude of the earthquake (9.0 on the Richter scale, or M9) and subsequent tsunami (with a reported wave height of 14 meters) exceeded the credible event on which the nuclear power plant’s design was based. The site has six nuclear reactors; three of them were operating at the time of the quake and successfully shut down in response to the ground shaking. Nevertheless, the power station and its spent fuel storage pools were overwhelmed by an event that had not been planned for — a “larger-than-expected” tsunami wave, leading to a sequence of catastrophic failures.

Some experts have since described the tsunami as a “rare” or “exceptional” event that was entirely out of the range of reasonable or credible expectation. But shallow, offshore earthquakes can cause tsunamis, and the height of the tsunami at Daiichi was certainly not unexpected for a 9.0 magnitude earthquake. In addition, there have been three 9.0 magnitude earthquakes during the past decade: Indonesia in 2004, Chile in 2010, and now Japan in 2011. The fact that such earthquakes occur infrequently over historical periods does not explain why the Fukushima nuclear power plant was not designed to withstand this type of geologic event.

From a geologic perspective, the earthquake and its great magnitude should not have been a surprise. Ten years ago, Japanese earth scientists, led by Koji Minoura at Tohoku University in Sendai, described a major earthquake and tsunami that happened in July 869 and was recorded in an historical document. This event, which is also clearly recorded in the coastal sediment of the Sendai plain, extended inland about four kilometers from the coast. Based on even older tsunami deposits that go back some 3,000 years, Minoura and his colleagues suggested a 1,000-year recurrence interval for large-scale earthquakes and tsunamis in Japan and presciently published their results in the Journal of Natural Disaster Science.

Their results and conclusions did not go unnoticed. Based on the Minoura et al. paper, Yukinobu Okamura, the director of Japan’s Active Fault and Earthquake Research Center, raised the possibility that a large tsunami could damage the Fukushima Daiichi plant. The plant operator, Tokyo Electric Power Company, dismissed these warnings.

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Written by makanaka

May 5, 2011 at 00:15

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