ENVIRONMENTAL QUESTION
The use of nuclear power raises important environmental questions. It is an apparent failure to tackle these satisfactorily that has led to much of the popular disapprobation that the nuclear industry attracts. There are two adjuncts to nuclear generation that cause the greatest concern: nuclear weapons and nuclear waste.
While the nuclear industry would claim that the civilian use of nuclear power is a separate issue to that of atomic weapons, the situation is not that clear-cut. Nuclear reactors are the source of the plutonium that is a primary constituent of modern nuclear weapons. Plutonium creation depends on the reactor design; a breeder reactor can produce large quantities while a PWR produces very little. Nevertheless, all reactors produce waste that contains dangerous fissile material. This is a subject of international concern.
The danger is widely recognized. Part of the role of the International Atomic Energy Agency is to monitor nuclear reactors and track their inventories of nuclear material to ensure than none is being sidetracked into nuclear weapons construction. Unfortunately, this system can never be foolproof. It seems that only if all nations can be persuaded to abandon nuclear weapons can this danger, or at least the popular fear of it, be removed. Such an agreement looks highly improbable.
The problem is political in nature. Nevertheless, it carries a stigma from which the industry can never escape. The prospect of a nuclear war terrifies most people. Unfortunately, for the nuclear power industry, some of the after-effects of nuclear explosion can also be produced by a major civilian nuclear accident. The contents of a nuclear reactor core include significant quantities of extremely radioactive nuclei. If these were released during a nuclear accident they would almost inevitably find their way into humans and animals via the atmosphere or through the food chain.
Large doses of radioactivity or exposure to large quantities of radioactive material kills relatively swiftly. Smaller quantities of radioactive material are lethal too, but over longer time scales. The most insidious effect is the genesis of a wide variety of cancers, many of which may not become apparent for 20 years or more. Other effects include genetic mutation that can lead to birth defects.
The prospect of an accident leading to a major release of radio-nuclides has created a great deal of apprehension about nuclear power. The industry has gone to extreme lengths to tackle this apprehension by building ever-more sophisticated safety features into their power plants. Unfortunately, the accidents at Three Mile Island in the United States, Chernobyl in the Ukraine, and Fukushima Daiichi in Japan remain potent symbols of the danger.
This danger has been magnified by a rise in international terrorism. The threat now exists that a terrorist organization might cause a nuclear power plant accident or, by exploiting contraband radioactive waste or fissile material, cause widespread nuclear contamination.
So far a nuclear incident of catastrophic proportions has been avoided, though both Chernobyl and Fukushima have caused extensive disruption, and in the case of the former, a disputed number of deaths as a result of radio- active exposure. Smaller incidents have been more common and low-level releases of radioactive material have taken place. The effects of low levels of radioactivity have proved difficult to quantify. Safe exposure levels are used by industry and regulators but these have been widely disputed. Only the elimination of radioactive releases from civilian power stations is likely to satisfy a large sector of the public.
Radioactive Waste
As the uranium fuel within a nuclear reactor undergoes fission, it generates a cocktail of radioactive atoms within the fuel pellets. Eventually the fissile uranium becomes of too low a concentration to sustain a nuclear reaction. At this point the fuel rod will be removed from the reactor. It must now be disposed of in a safe manner. Yet after more than 60 years of nuclear fission, no safe method of disposal has been developed.
Radioactive waste disposal has become one of the key environmental battlegrounds over which the future of nuclear power has been fought. Environ- mentalists argue that no system of waste disposal can be absolutely safe, either now nor in the future. And since some radio-nuclides will remain a danger for thousands of years, the future is an important consideration.
Governments and the nuclear industry have tried to find acceptable solutions. But in countries where popular opinion is taken into consideration, no mutually acceptable solution has been found. As a result, most spent fuel has been stored in the nuclear power plants where it was produced. This is now causing its own problems as storage ponds designed to store a few years’ waste become filled, or overflowing.
One avenue that has been explored is the reprocessing of spent fuel to remove the active ingredients. Some of the recovered material can be recycled as fuel. The remainder must be stored safely until it has become inactive. But reprocessing has proved expensive and can exacerbate the problem of disposal rather than assisting it. As a result, it too appears publicly unacceptable.
The primary alternative is to bury waste deep underground in a manner that will prevent it ever being released. This requires both a means to encapsulate the waste and a place to store the waste once encapsulated. Encapsulation techniques include sealing the waste in a glasslike matrix. Finding a site for such encapsulated waste has proved problematic. An underground site must be in stable rock formation in a region not subject to seismic disturbance. Sites in the United States and Europe have been studied but none has yet been accepted. Even if site approval is achieved, there appears little prospect of any nuclear waste repository being built until well into the middle of the 21st century.
Other solutions have been proposed for nuclear waste disposal. One involves loading the fuel into a rocket and shooting it into the sun. Another uti- lizes particle accelerators to destroy the radioactive material generated during fission.
Environmentalists argue that the problem of nuclear waste is insoluble and represents an ever-growing burden on future generations. The industry counters this, but in the absence of a persuasive solution its arguments lack weight. Unless a solution is found, the industry will continue to suffer.
Waste Categories
Spent nuclear fuel and the waste from reprocessing plants represent the most dangerous of radioactive wastes, but there are other types too. In the United States these first two types of waste are categorized as high-level waste4 while the remainder of the waste from nuclear power plant operations is classified as low-level waste. There is also a category called transuranic waste, which is waste containing traces of elements with atomic numbers greater than that of uranium (92). Low-level wastes are further subdivided into classes depending on the amount of radioactivity per unit volume they contain.
In the United Kingdom there are three categories of waste: high level, inter- mediate level, and low level. High level includes spent fuel and reprocessing plant waste, intermediate level is mainly the metal cases from fuel rods, and low level constitutes the remainder. Normally both high- and intermediate-level waste require some form of screening to protect workers, while low-level waste can be handled without a protective radioactive screen.
High-level wastes are expected to remain radioactive for thousands of years. It is these wastes that cause the greatest concern and for which some storage or disposal solution is most urgently required. But these wastes form a very small part of the nuclear waste generated by the industry. Most is low-level waste. Even so, it too must be disposed of safely. Low-level waste can arise from many sources. Anything within a nuclear power plant that has even the smallest exposer to any radioactive material must be considered contaminated. One of the greatest sources of such waste is the fabric of a nuclear power plant itself.
Decommissioning
A nuclear power plant will eventually reach the end of its life, and when it does, it must be decommissioned. At this stage the final, and perhaps largest, nuclear waste problem arises. After 30 or more years5 of generating power from nuclear fission, most of the components of the plant have become contaminated and must be treated as radioactive waste. This presents a problem that is enormous in scale and costly in both manpower and financial terms.
The cleanest solution is to completely dismantle the plant and dispose of the radioactive debris safely. This is also the most expensive option. A halfway solution is to remove the most radioactive components and then seal up the plant for 20–50 years, allowing the low-level waste to decay, before tackling the rest. Two Magnox reactor buildings in the United Kingdom were sealed in this way in 2011 and are expected to remain in that state for 65 years. A third solution is to seal the plant up with everything inside and leave it, entombed, for hundreds of years. This has been the fate of the Chernobyl plant.
Decommissioning is a costly process. Regulations in many countries now require that a nuclear-generating company put by sufficient funds to pay for decommissioning of its plants. The U.S. utility Southern California Edison has put aside $2.7 billion to decommission its San Onofre power plant, expect- ing this to cover around 90% of the total expenditure. Meanwhile, in 2011 the U.K. government estimated nuclear decommissioning costs for its existing power plants to be £54 billion. When building a new nuclear plant, the cost of decommissioning must, therefore, be taken into account.