Table of Contents
The Energy Challenge
Nuclear Power Facts
Nuclear Power Advantages
The Salient Points
Annex I: The DECADES Project
Annex II: Nuclear Power Case Studies
Small Waste Quantities
Confinement versus dispersion
There has been a continuous public concern that nuclear waste cannot be safely managed. However, managing nuclear waste is less of a problem because the quantities are remarkably small relative to the energy produced. The small quantities permit a confinement strategy for the radioactive material, beginning with the nuclear fission process and through to waste disposal, essentially isolated from the environment [Fig.: Two Alternative Waste Strategies]. Disposal techniques exist and the hazard decreases with time owing to radioactive decay. The main disposal options are simple near surface, engineered structures, mined cavities, and deep geological repositories. Some thirty countries currently operate licensed repositories for low and intermediate level radioactive waste.
In sharp contrast, disposal of the large quantities of fossil fuel waste follows an alternative dispersion strategy. Most of the waste (noxious gases and many toxic pollutants) is dispersed directly into the atmosphere while some solid waste containing toxic pollutants is buried in shallow ground, there being no practical alternative. The waste is dispersed or buried at concentrations considered not harmful. While the resulting impact can be small, the cumulative waste over many years from a large number of waste producing activities can easily overburden the natural environment, locally as well as globally.
Confinement is preferable to dispersion, but is economically feasible only when waste volumes are small and arise under easily controlled conditions. Most nuclear waste consists of relatively short lived low and intermediate level waste, annually some 450 and 350 tonnes respectively from a 1 000 MW(e) plant. Low level waste, which consists largely of minimally contaminated clothing, machine parts and industrial resins, can be placed in containers and disposed of in trenches covered by soil. The waste does not require shielding during handling or transportation and can be less radioactive than the equivalent weight of coal plant fly ash or even coffee beans, Brazil nuts and fertilizer which contain natural radioactive material. While not necessary for radiation protection purposes, waste can be isolated in engineered structures such as concrete lined trenches and vaults.
Intermediate level waste, which includes reactor parts and contaminated equipment, is packaged in cement inside steel drums. In a similar way to low level waste, it can be safely disposed of in near surface facilities. Nuclear power is not responsible for all radioactive waste. In the USA, nearly 50% by volume of non-defence related low and intermediate waste originates from government, industrial and medical activities.
High level waste
High level waste consists of liquid waste from reprocessing after the recovery of uranium and plutonium or spent fuel for ultimate disposal if it is not to be reprocessed. The spent fuel, some 12 000 tonnes from all operating plants, can be readily stored above or below ground awaiting decisions on long term disposal options. An interim storage period is necessary to allow the residual heat generated in the spent fuel to decrease, disposal being more practical after several decades. The volume of high level liquid waste from the reprocessing of 30 tonnes of spent fuel released annually from a 1 000 MW(e) plant, containing more than 99% of the radioactivity, is some 10 cubic metres. The waste can be vitrified to a glass solid and stored awaiting long term disposal.
To date no long term disposal site has been licensed in any country. Deep underground geological formations which have not been disturbed for many millions and even billions of years are being considered. Solid salt domes or granite tunnels several hundred metres below the surface are impervious to water ingress, which is the potential mechanism for material transport to the surface environment. A number of barriers would prevent the release and transport of disposed radioactive material; the canisters containing the vitrified waste, a surrounding absorbent clay backfill and the solid host material. Even if radioactive material were to escape from its vitrified state and not be retained in the clay backfill, the long path through the host rock to the surface would probably ensure sufficient dilution so as to pose little risk to human health or the environment.
A number of countries are developing repository concepts to handle vitrified waste as well as spent fuel. Startup times for repositories are likely at least a decade away. The most convincing demonstration to the public that high level waste can be managed will be the construction and operation of a repository. Disposal is blocked not by technical, but by political obstacles.
Time span issues
A common apprehension about radioactive waste concerns its long lived nature. Waste from reprocessing facilities, where much of the very long lived materials such as plutonium are removed, would decay to radioactive levels below that of natural uranium ore in less than one thousand years compared to more than ten thousand years without reprocessing. Waste pollutants from coal such as cadmium, lead or mercury - much of which are dispersed or disposed of in near surface facilities - remain toxic indefinitely. There is a growing recognition that management of indefinitely toxic waste and radioactive waste warrant a harmonized approach. However, managing toxic wastes from fossil fuels to standards proposed for high level radioactive wastes is not economically feasible.
Indicators to compare radioactive waste hazards with fossil fuel waste hazards have been developed. One such indicator is based on admissible concentrations of radioactive and toxic pollutants in water. For similar amounts of energy generated, in some one hundred years the amount of water necessary to dilute reprocessed radioactive waste to admissible concentrations would be less than the amount to dilute lignite waste to admissible concentrations - the reason being the relatively small quantity of radioactive material and the relatively rapid decay of reprocessing waste owing to the removal of long lived elements [Fig.: Comparison of Radioactive Waste Hazards with Fossil Fuel Waste Hazards].