Radiation, Health, and the Environment
It is well known that ionizing radiation can kill and injure, and that radioactive substances can be poisonous. A dose of ten seivert (over the whole body, in a short time) to an adult human is considered infallibly lethal, and four to five sievert can be expected to cause death within thirty days in fifty percent of average adults, without medical treatment. Somewhat lower doses cause shattering diarrhea, temporary sterility, loss of hair, and a variety of other unpleasant symptoms, and elevate the lifetime risk of cancer, resulting in an overall shorter life expectancy. For exposures insufficient to cause erythema (sunburn), however, the case is far less clear.
One reason is that the world around us is naturally radioactive. Humans are constantly exposed to radiation from a variety of natural sources, and the biomedical significance of comparatively small artificial additions to this natural background is a nice question. Further, the damage done on a cellular scale by radiation is very much like the damage from many other causes, and the same natural mechanisms act to compensate for or repair it. Since variations in life expectancy and general health are influenced by a variety of factors, many of which are not known with any certainty, it is difficult to separate out the contribution of radiation.
An almost invariable human reaction to uncertainty and doubt is a shrill clamour that great dangers are concealed behind a facade of ignorance. The claims in this instance include a wide variety of illnesses, hereditary effects (which have not been observed in the descendants of atomic bomb survivors), and even an insidious loss of fertility among humans, animals, and plants, all from quite low doses. The startling vivacity of wildlife in the “exclusion zone” around Chernobyl should be sufficient to lay that idea to rest.
There is good evidence that the incidence of certain brain tumours is related to the use of X-rays in the treatment of childhood ringworm. And yet, it is a remarkable antidote to hysteria to realize that even doses calculated to make the hair fall out ― as much as 1.5 Gy ; one paper by a practitioner complains of sloppiness on the part of some colleagues, leading to definite symptoms of radiation sickness ― and applied directly over the brain during an especially vulnerable stage of life engender such effects only after the lapse of decades, and then only in a small fraction of the exposed population. The official position of the Health Physics Society, the professional organization for those who work directly with human exposure to ionizing radiation, is that there is insufficient clear evidence of any harm at low dose rates to make meaningful statements.
Conversely, the uncertainty concerning the degree of harm from low-dose radiation has led some to propose that it may have healthful effects, perhaps by stimulating the body’s natural repair mechanisms. (Aerobic exercise has just such an effect, and at high levels it produces very definite damage.) Just as people who subscribe to an exaggerated idea of the dangers of radiation tend to be strong opponents of atomic power, those who believe in “radiation hormesis” tend to be advocates. It is, however, by no means necessary to accept this hypothesis in order to conclude that the good of atomic power outweighs the actual or potential harm.
Atomic Power and Radiation
There is a common, but erroneous, idea that atomic power is a major contributor to radiation exposure. The assumption is a natural one. After all, atomic power plants use radioactive uranium for fuel, generate enormous radiation fluxes in operation, and create brand new radionuclides in the form of fission and activation products. For just this reason, standards for radiation exposures and releases in the nuclear industry are set on what is termed an ALARA basis, “as low as reasonably achievable”. In fact, however, the great energy content of nuclear fuels means that only a little material is involved, in comparison to other industries which handle radioactive substances ; and, in anything like normal circumstances, power reactors and related facilities are tightly sealed, so that very little material escapes.
To the contrary, it is not difficult to show that the use of atomic power reduces the radioactivity of the Earth (though the effect is small, since most of the planet’s radioactive content is far below the crust, where humans can’t get at it). The fission process, in effect, takes the energy which would drive a decay chain billions of years long, and releases it in moments. Long-lived radioactive nuclei are destroyed, and short-lived ones are created ; after three hundred years, the fission products are less radioactive than the ore mined to produce the fuel they came from.
The personnel of atomic plants are scrupulous in documenting discharges of radioactivity to the environment. So, for instance, we read of one release of 330 kBq, equivalent to perhaps ten domestic smoke detectors (which are not treated as radioactive waste requiring separate disposal), or the magazines in a small library. If not entirely convinced of the wisdom of ALARA, one might question whether the cost of reducing the release to this low level was commensurate with the benefit. Regardless, the result is that radiation exposure from the nuclear industry is better quantified and better publicized than exposure from other sources.
When we compare atomic power to its most direct competitors, we get quite a surprise. According to studies done at Oak Ridge National Laboratory, in the course of ordinary operations, workers in coal-burning power plants are exposed to between ten and one hundred times as much radiation, per kilowatt-hour sent out, as their counterparts in atomic plants. Given that coal is mined in great quantities, and moved long distances, and that the waste products of coal burning are often discharged right into the air and the waterways, it would not be surprising if general population exposure followed the same pattern.
Suppose, then, that burning coal results in thirty times as much radiation exposure to humans as fissioning atoms, for an equivalent amount of primary energy. According to the International Energy Agency, in 2011, coal (including peat) accounted for 28.8% of world primary energy production, and nuclear fission 5.1%. So, in that case, the radiation dose to the average person from coal energy was 170 times his dose from nuclear energy. Not to belabour the point, but replacing all coal with fission would result in a decrease of human radiation exposure from the energy industry equal to 164 times the current world total from atomic power.
Even in case of a major accident, radioactive releases from atomic power plants are not as consequential as they might seem. The Chernobyl meltdown of 1986 resulted in severe exposures to plant personnel and the ‘liquidators’ sent in to put out the fire ― some of them died of radiation poisoning. From the standpoint of global human exposure, however, it was not very significant.
How can we say that? Consider for a moment the industry of mining and processing phosphate rock for agricultural fertilizer. Nobody would characterize this prosaic and necessary activity as belonging to the nuclear industry, or the field of radiation work. Yet it accounts for a large total radiation dose every year, because of a quirk of chemistry, by which minerals rich in phosphorus tend to concentrate uranium as well, with its daughter products. (In fact uranium has sometimes been produced as a by-product of phosphates.) Annual world human exposure to radioactives from the phosphate industry is estimated at 12μSv per person, or about 60 kSv in the mid-1980s ; total world human exposure (for all time) from Chernobyl, at 600 kSv, or ten years of phosphate production.
The American homeowner receives more radiation in an afternoon fertilizing his lawn, thanks to phosphates and potassium, than from all sources (including accidents) related to atomic power in a year. This, by the way, helps illustrate the problematical notion of ‘collective dose’. It should be clear that there is no meaningful equivalence between a dose of 10 Sv to one person, and a dose of 1 μSv (tiny in comparison to the natural background) to each of ten million.
A related concept to ALARA is ‘walk-away safety’. Nobody expects a fertilizer plant or an oil refinery to shut itself down safely if the plant workers suddenly leave in the middle of normal operations, even though ― on the basis of the evidence ― accidents at such facilities are far more likely to cause death and injury to personnel and the public. But exactly that has been touted as an advantage of certain new reactor designs. The bare possibility of such a thing is a testimony to the safety of atomic power.
Atomic Power and Human Welfare
The real question is not, what harm might atomic power do? but, what good can it do? And the answer comes back, “much”. Scarcely another human activity is subjected to a demand that it justify itself in terms of non-harmfulness. More than thirty thousand people are killed each year in automobile collisions, in the United States alone ― do we demand that people stop driving, until cars can be made perfectly safe? No! As a society, we think nothing of the annual one chance in ten thousand of dying on the road (let alone the radiation exposure from medical X-rays associated with injury accidents), when compared to the convenience of hopping in the car. The widespread use of atomic power brings with it no such risk, and its potential benefits are enormous.
Around the world, every year, thousands of people die in the process of mining coal. That is not ‘predicted excess cancer fatalities’, or some such faceless statistical measure. It is individual men and boys, women and girls, with names and families, who are crushed, or suffocated, or burned ― who go down into the pits and never come forth alive. And that leaves out all those who are crippled by injuries, or by the dust in their lungs. That we allow this to go on, when it need not, is deeply immoral. Uranium mining is not a pleasant business either ; mining never is, but the quantity of fuel required (especially with breeder reactors) to meet the needs of the world is so much less that the human and environmental costs cannot help but be less. Indeed, given that uranium and thorium can be recovered in large quantities as secondary products (even from coal waste), the required scale of mining activities is minuscule.
Atomic power can even help, however modestly, with that problem of traffic safety. In the United States, great tonnages of coal are moved every day by rail, one way from mines to power plants, a thousand kilometers or more in some cases, and the cars go back empty. (We are beginning to see a similar movement of oil.) This slow, low-value cargo burdens the rail system and contributes to poor on-time performance. Consequently, shippers often prefer to send goods by truck instead of train. And trucks, by virtue of their large size and long reaction time, contribute disproportionately to wrecks, traffic congestion, and wear and tear on the roadways.
Quite aside from these negative benefits, atomic power has its unique contributions to make. Smoke detectors, made with americium-241 obtained from power-reactor spent fuel, save numerous lives annually. In the field of medicine, vital diagnostic and theraputic procedures depend on artificial radioisotopes such as technetium-99m and iodine-131. Radioactive tracers and gages are crucial to industrial automation, and to safety inspections of everything from boilers to bridges. Space missions to the outer planets would be infeasible without isotopic heat and power sources.
More broadly, the fact that atomic power plants require very little fuel has important consequences. Even in wealthy countries, isolated communities are often dependent on diesel generators for electricity, tying them to costly and sometimes undependable fuel-oil shipments, restricting their development options, and exacerbating the trend of flight from the countryside. In poorer countries, where the need is dire, any kind of access to power outside the principal cities is uncertain, and too expensive for constructive employment. But one charge of nuclear fuel can deliver megawatts for decades ; indeed, the US Navy intends to simply decommission the new Virginia-class submarines after thirty-five years, rather than refuel them. Atomic ‘package plants’ could bring the full benefit of electrification (and, in many cases, plentiful heat) to remote districts without the complication of long power lines or other problematic infrastructure.
Likewise, even before breeder reactors enter the picture, a large power plant or even an entire country can easily stockpile fuel for years ahead. It was for this reason that the members of the European Coal and Steel Community resolved to emphasize the development of atomic power in the aftermath of the Suez crisis. They recognized that uranium and thorium represented a source of energy capable of substituting for fossil fuels, which could not effectively be embargoed after the fashion of oil. At the present day, we might add, ‘or shut off like gas’.
Radiation a Factor of Safety
Radioactivity is very easily detected. That it cannot ordinarily be discerned by the senses adds to the mystery and fear with which it is regarded. Nevertheless, remarkably simple instruments can not only establish the presence of radiation, but distinguish particular radionuclides in concentrations of parts per billion or less (certainly small enough to be innocuous), and trace them back to their sources. And, of course, there are only a few score significant radioactive species, as opposed to thousands upon thousands of potentially harmful chemicals.
Potent chemical fuels, although capable of releasing far less energy than nuclear fuels, are immsensely dangerous, both because of their potential for uncontrolled reaction, and because they are hard to track down. Nuclear fuels, which can only react under conditions which require careful arranging, provide an unmistakable signature of their presence. As a result, ordinary private citizens can conduct monitoring for their own satisfaction, which is well-nigh impossible where radioinert substances are concerned. Indeed, one of the ways chemical pollution has been tracked is by a naturally-occurring radioactive signature. Because of the singular detectibility of radiation, a dangerous condition at an atomic power facility is almost certain to be identified and corrected as soon as it appears.