Guest essay by Roger Graves
Whether or not one accepts the need to reduce CO2 emissions, a power source capable of providing reliable base load power with minimal fuel requirements should not be dismissed lightly. Yet nuclear power is commonly dismissed by many people, including journalists and public intellectuals, as too dangerous to be considered. This essay is an attempt to look at the dangers of nuclear power in a dispassionate manner. There will be two parts to it. The present essay is an examination of the facts regarding nuclear power, and nuclear accidents in particular, while a second essay will examine the theoretical aspects, particularly of radiation effects.
First, a few definitions. The energy associated with electromagnetic radiation, or more specifically with each quantum of radiation, is proportional to its frequency. If the frequency is high enough, and here we are talking of X-rays and gamma rays, the associated energy will be sufficient to strip electrons from atoms when the radiation interacts with matter. Such radiation is known for obvious reasons as ionizing radiation. Lower energy radiation, such as visible light and microwaves, has insufficient energy to strip electrons and is known as non-ionizing radiation.
Stripping electrons from complex organic molecules will presumably disrupt those molecules in some fashion, so it is reasonable to expect biological effects from exposure to ionizing radiation. Ionizing radiation exposure is measured in units of sieverts, named after the Swedish medical physicist Rolf Sievert. More specifically, the sievert is based upon the effect that ionizing radiation will have on human bodies. One seivert represents a very large dose, so exposure levels are usually expressed in millisieverts (mSv).
There are two schools of thought on ionizing radiation. The first is that the human species has evolved in a background of ionizing radiation, and is well adapted to it. Sources of natural background radiation include cosmic radiation, radioactive elements in the Earth’s crust, radon gas in the atmosphere, and radioactive isotopes in our food. The average dose we receive, on a worldwide basis, is 2.4 mSv per year, although this can vary significantly from place to place . Humans, according to this school of thought, are insensitive to radiation doses of this magnitude. Only when radiation levels are a couple of orders of magnitude or more higher do we have any cause for concern.
The second school of thought holds that all ionizing radiation is harmful, and that any exposure to it, down to the smallest detectable amount, carries a risk of cancer with it. This is the viewpoint espoused by the US National Academies’ seventh report on the biological effects of ionizing radiation, commonly known as BEIR VII . However, in my opinion there are some serious problems with this report, which I shall deal with in a later essay. Its overall finding that “the risk of cancer proceeds in a linear fashion at lower doses without a threshold and that the smallest dose has the potential to cause a small increase in risk to humans” is not altogether credible, considering the evolutionary background of the human race.
Notwithstanding theoretical arguments on the effects of radiation, it is instructive to look at the observed effects of radiation, with regard to the normal operation of nuclear power plants and with regard to nuclear accidents.
RADIATION LEVELS NEAR NUCLEAR PLANTS
Nuclear power stations contain large amounts of radioactive material, and it would be unrealistic to expect that there would not be at least some detectable radiation near them. A typical figure for the additional exposure caused by living near a normally-operating nuclear power station is 0.02 mSv/year , which is roughly 1% of the natural background radiation dose. Living near a nuclear power station for a year is equivalent to living in Denver (altitude 5000 feet) for two days, or taking a single US coast-to-coast flight, since higher altitude results in less shielding from cosmic rays.
A study published by the Canadian Nuclear Safety Commission in 2013 concluded that there was no evidence of increased cancer rates due to radiation effects on populations living within 25 km of Ontario’s Pickering, Darlington and Bruce nuclear power plants . The study found that while some cancer rates were higher than the general population, others were lower, without any consistent pattern, which is perhaps as good a definition of statistical variation as any.
While radiation levels from normally-operating nuclear plants are negligible, what would be the result of a major accident in a nuclear power station? To answer this question we can look at three such accidents, at Three Mile Island, Fukushima, and Chernobyl.
Three Mile Island
In 1979 a meltdown occurred in one of the reactors at Three Mile Island in Pennsylvania. Very little radiation was released. The average dose from the incident was less than one per cent of the natural background radiation. To quote the US Senate report on the accident: “The Special Investigation … found no persuasive evidence that releases during the accident resulted in adverse near-term physical health effects or will result in statistically significant long-term physical health effects” . A variety of epidemiology studies, e.g. , have since concluded that the accident had no observable long term health effects.
In March 2011 the Fukushima nuclear power station was hit by two major natural disasters in quick succession, first a massive earthquake, then a huge tsunami. As a result, over the next several days three of the six reactors at the site started overheating and went into meltdown.
While there were about 18,000 fatalities directly attributable to the earthquake and tsunami, there were no fatalities linked to short‑term over‑exposure to radiation at Fukushima, nor are any long-term health effects expected. The United Nations Scientific Committee on the Effects of Atomic Radiation (UNSCEAR) published a report in 2013 on radiation effects from the accident . The Committee found that:
· “The doses to the general public, both those incurred during the first year and estimated for their lifetimes, are generally low or very low. No discernible increased incidence of radiation-related health effects are expected among exposed members of the public or their descendants.”
· “No acute health effects (i.e. acute radiation syndrome or other deterministic effects) had been observed among the workers and the general public that could be attributed to radiation exposure from the accident.”
With regard to nuclear workers, the report goes on to say that 170 workers at the site received doses in excess of 100 mSv, averaging about 140 mSv. “No discernible increase in cancer in this group is expected, because its magnitude would be small in comparison with normal statistical fluctuations”.
Correlation of these predictions with actual long-term observed health effects will have to wait for many years yet, since the accident happened only a few years ago. However, data in this respect exists with regard to the Chernobyl accident, which is discussed below.
Over-reaction by authorities who initiated unnecessary mass evacuations may have resulted in some deaths. According to one report, “The psychological trauma of evacuation was a bigger health risk for most than any likely exposure from early return to homes” .
The Chernobyl accident in 1986 was the largest non-military radiological event ever to have occurred. The Soviet reactors in use at the time were designed without much thought for safety. The catastrophe occurred because some tests being conducted on a reactor went out of control; descriptions of the way the operators made ad hoc changes and overrode automatic safety features during the tests are hair-raising . According to a 1992 International Atomic Energy Agency report, “The accident can be said to have flowed from a deficient safety culture, not only at the Chernobyl plant, but throughout the Soviet design, operating and regulatory organizations for nuclear power that existed at that time” .
A 2008 UNSCEAR report confirmed that there were 28 deaths from massive radiation exposure in the days and weeks following the incident, and a further 19 deaths occurred during the period 1987-2004 in those who had received high doses, although not all of the latter were attributable to radiation exposure . The real death toll, however, is predicted to occur from cancers induced by long-term radiation exposure, although we must be cautious about this. Various environmental NGOs have produced what are generally recognized to be grossly inflated figures . A more realistic figure is contained in a paper published in the International Journal of Cancer (IJC) by an international team in 2006, some twenty years after the event . It put the number of cases caused by Chernobyl at 0.01% of all incident cancers in Europe since the accident, with the bulk of this increase occurring in the most affected regions (Ukraine, Belarus and the Russian Federation) . To quote this paper: “It is unlikely that the cancer burden from the largest radiological accident to date could be detected by monitoring national cancer statistics. Indeed, results of analyses of time trends in cancer incidence and mortality in Europe do not, at present, indicate any increase in cancer rates – other than of thyroid cancer in the most contaminated regions – that can be clearly attributed to radiation from the Chernobyl accident”.
Thyroid cancers following nuclear accidents are caused by ingestion of radioactive isotopes of iodine. These isotopes are typically airborne after a major nuclear accident, and can be ingested into the lungs. Iodine ingested in this way is normally excreted from the body within a day or two, except from the thyroid gland in which it tends to concentrate. Since the most important isotope, 131I, has a half-life of only eight days, the conditions leading to thyroid cancer constitute a fairly short-term problem. It is worth noting that radiation-caused thyroid cancers can largely be avoided by the simple expedient of issuing iodine tablets to the affected population immediately after an accident .
As reported in the IJC paper, the investigators looked for evidence from existing cancer statistics of increases in non-thyroid cancer rates, but found none (“… results of analyses of time trends in cancer incidence and mortality in Europe do not, at present, indicate any increase in cancer rates …”). They then applied the BEIR VII model to calculate the cancer rates that ought to have occurred according to the model, to arrive at their 0.01% estimate of all incident cancers. However, since this is a suspect model, it is quite likely that the actual number of non-thyroid cancer cases was much lower than this, possibly even zero, because no evidence of increased cancer rates had in fact been found. The figure of 16,000 or more cancer cases caused by Chernobyl that is frequently used by anti-nuclear groups is simply a mathematical projection based on this 0.01% figure without any relationship to real world data.
Some will claim that cancers can take considerably longer than 20 years to develop, and that we should be prepared for spikes in cancer rates up to 60 years after the event. As it happens, there is direct evidence to refute this. Two very large radiological events occurred over 70 years ago at Hiroshima and Nagasaki, and the surviving population’s health has been closely studied ever since. According to the Radiation Effects Research Foundation (RERF), jointly funded by the US and Japan to study radiation effects with regard to the atomic bomb, “The excess risk of leukemia, seen especially among those exposed as children, was highest during the first ten years after exposure, but has decreased over time and has now virtually disappeared. In contrast, excess risk for cancers other than leukemia (solid cancers) has stayed constant and seems likely to persist throughout the lifetime of the survivors” . This would imply that, whatever the Chernobyl-related cancer incidence rate might be now, it will probably stay more or less that way without any future spikes.
Radiation and Genetic Effects
One of the areas of concern about radiation exposure is the possibility that genetic mutations may occur in children as yet unborn. Again quoting the RERF, “Efforts to detect genetic effects began in the late 1940s and continue. Thus far, no evidence of increased genetic effects has been found” .
The three largest nuclear accidents to date, Three Mile Island, Fukushima, and Chernobyl, have produced no physical evidence, as opposed to predictions based on mathematical models, of increased non-thyroid cancer rates among the general population.
Thyroid cancers can occur with a major nuclear accident such as Chernobyl, but there is a simple mitigation method available, namely issuing iodine tablets to the affected population as soon as possible after the accident. This is not too much different from issuing a boiled-water advisory in the event of a water supply system problem.
Deaths from massive radiation exposure can occur in a major nuclear accident, but this is no different in principle from any other major industrial accident. Chernobyl caused less than 50 such deaths; for comparison, the 2009 Sayano-Shushenskaya hydroelectric accident in Russia caused 75 deaths , and the Bhopal disaster caused several thousand .
Apart from a few instances of deaths from massive radiation exposure, and easily avoidable thyroid cancers, there is no physical evidence, as opposed to theoretical projections, of long-term health effects from any nuclear accident to date. While nuclear accidents are to be deplored, there is no justification for singling out nuclear power as being especially dangerous. The fear of nuclear espoused by much of the media is vastly exaggerated.
Roger Graves is a physicist and risk management specialist who, much to his chagrin, is not associated with big nuclear, big oil, or big anything else.
- http://www.world-nuclear.org/info/Safety-and-Security/Safety-of- /Appendices/Fukushima–Radiation-Exposure/
- 9. https://en.wikipedia.org/wiki/Chernobyl_disaster