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Geological Disposal of Highly Radioactive Waste Is Based on a Multi-Barrier Approach to Safely Isolate the Waste from the Environment

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Geological Disposal of Highly Radioactive Waste Is Based on a Multi-Barrier Approach to Safely Isolate the Waste from the Environment Geological disposal of highly radioactive waste is based on a multi-barrier approach to safely isolate the waste from the environment. In a number of countries, research is being done at underground laboratories. (Credits: SKB, ANORA) A storage building for low- level radioactive wastes in the USA. (Credit: USDOE) At the Institute of Reactor Research in Switzer- land, some low-level radioactive wastes are stored on site. (Credit: UNIPEDE) IAEA BULLETIN, 4/1989 Features Radioactive waste management: World overview An update of trends and developments by J.L. Zhu and C.Y. Chan With a history of over 40 years of development, the what is being done on an international basis in this field. use of the atom can be classified as a maturing technol- The perspective of this summary is primarily from ogy. However, the benefits that result from the use of civilian nuclear power programmes. the atom are not without concerns. Few topics have commanded as much attention from scientists, govern- Trends and strategies ments, and the general public over the past 30 years as the subject of "nuclear waste" (radioactive waste) and As countries pursue, plan, and implement national what to do with it. In many countries, the future and con- programmes to manage various types of radioactive tinued use of nuclear power is contingent on acceptable waste, there are similar issues and some apparent trends solutions for waste management and disposal. in the approaches and strategies. In summary: • Emphasis is being placed upon demonstrating that Almost every one of the IAEA's 113 Member States all radioactive wastes, even the most highly radioactive generates some radioactive wastes. These wastes have wastes, can be safely isolated for the required time various forms and characteristics and they arise from period from man and the environment. Most countries nuclear generation of electricity, nuclear fuel cycle with nuclear power have programmes to study, develop, activities, industrial application, and work at research and demonstrate technical solutions to safely manage centres and hospitals, for example. The actual volumes radioactive waste. The purpose of many projects for of wastes from nuclear electricity generation and other research and development and demonstration is to show nuclear applications are small compared to those of that acceptable methods exist for long-term safe disposal other technologies or industries (i.e. coal-burning power of such wastes. These developments and continued stations). However, a major concern is that some radio- studies are important for several reasons: they will test active wastes can pose a threat to man and the environ- the latest conceptual solutions and options for waste ment for long periods of time. management and disposal; they will yield further test This report summarizes the national trends and strate- data that will help to improve computerized mathemati- gies for radioactive waste management and disposal, and cal models used to make safety assessments and evalua- tions of potential geological disposal conditions; and Mr Zhu is Director of the IAEA Division of Nuclear Fuel Cycle and Waste Management and Ms Chan is a staff member of the Division. they will help assess, through analytical modelling and In the United Kingdom each year, more than 4 million cubic metres of toxic waste are produced. Only 1.1% of this amount is radioactive waste. Of this HLW small fraction, most of the waste con- tains low levels of radioactivity. Source: UKAEA 0.1% IAEA BULLETIN, 4/1989 Features Radioactive waste terms For safety and technical reasons, the various forms of • Intermediate-level wastes (ILW) contain lower levels nuclear wastes are usually categorized by their levels of of radioactivity and heat content than high-level wastes, radioactivity, heat content, and potential hazard. The but they still must be shielded during handling and trans- IAEA has established definitions describing the technical port. Such wastes may include resins from reactor opera- features of radioactive wastes that are applied to their tions or solidified chemical sludges, as well as pieces of management in many countries. For general purposes, equipment or metal fragments. Commercial engineering however, more simplified descriptions and explana- processes are being used to treat and immobilize these tions of important terms may be useful to a basic wastes; disposal in surface structures or shallow burial is understanding: practiced widely. Some countries have built or plan to build shallow repositories in rock formations on land or • Half-life. This term refers to the time it takes for any under the sea. given radionuclide to lose half of its radioactivity. Most • High-level wastes (HLW) arise from the reprocessing significant fission products, which are highly radioactive, of spent fuel from nuclear power reactors through which have half-lives of about 30 years or less; for example, uranium and plutonium can be recovered for re-use. caesium-137. A few, such as iodine-129, have half-lives These wastes contain transuranic elements, and fission in the thousands of years. For perspective, natural products that are highly radioactive, heat-generating, uranium has a half-life of about 4500 million years, or and long-lived. Liquid HLW has been effectively stored in roughly the age of the earth. tanks at specially constructed facilities. Before final • Short-lived and long-lived wastes. These terms disposal and isolation from the biosphere, they require refer to a given radioactive element's half-life. Those with treatment and solidification. Spent fuel that is not half-lives longer than approximately 30 years are gener- reprocessed may be considered a high-level waste. ally considered long-lived. • Alpha-bearing wastes (also called transuranic, • Low-level wastes (LLW) contain a negligible amount plutonium-contaminated material, or alpha wastes) of long-lived radionuclides. Produced by peaceful include wastes that are contaminated with enough long- nuclear activities in industry, medicine, research, and by lived, alpha-emitting nuclides to make disposal at a nuclear power operations, such wastes may include shallow land burial site unacceptable. They arise prin- items such as packaged gloves, rags, glass, small tools, cipally from spent fuel reprocessing and mixed-oxide fuel paper, and filters which have been contaminated by fabrication. The wastes may be disposed of in a similar radioactive material. manner to HLW. validation and laboratory research, the capability of a waste repository to protect public health safely over the Environmental assessment long-term. Additional assurance on the long-term Following the recommendations of the Post-Accident behaviour of waste is being obtained from studies of Review Meeting on the Chernobyl Accident in 1986, the natural radioactive conditions, including the behaviour IAEA established an international study aimed at utilizing of radionuclides from uranium ore bodies that have been the environmental data which exist as a result of the fall- present and undisturbed in the earth's crust for millions out from the Chernobyl release. This study, known as the of years. Validation of Model Predictions (VAMP), seeks to take the advantage of the "natural laboratory" for validating • Several countries are building or planning environmental transfer models. Such models find appli- commercial-scale reprocessing and vitrification facili- cation in assessing the radiological impacts in all parts of ties. The reprocessing of spent fuel is planned or being the nuclear fuel cycle. It operates with four separate implemented by almost one-half of the countries with working groups of experts from research institutions in nuclear power. France and the United Kingdom have more than 20 Member States and has attracted co- sponsorship from the Commission of the European Com- had commercial reprocessing capabilities for nearly a munities (CEC). VAMP is scheduled to continue until decade. However, by the early 1990s, most of the other 1992. countries planning reprocessing will have operational The IAEA is also participating in a similar interna- facilities. tional study, the Biospheric Model Validation Study To improve vitrification technologies (the immobili- (BIOMOVS), initiated in 1986 by the Swedish National zation of waste into glass or glass-like form), some Institute of Radiation Protection (SSI). This study, which countries have built or plan to build small-scale pilot began prior to the Chernobyl accident, tests models for ecological transfer and bioaccumulation of the plants to demonstrate the technology at hand. A few full- radionuclides and other tracer substances. The study scale vitrification plants are presently in operation and has changed its original schedule to consider post- other plants are either in the planning or construction Chernobyl accident data and will now continue until phase. The Australian Nuclear Science and Technology 1991. — S. Hossain, Division of Nuclear Fuel Cycle and Organization (ANSTO) has recently started integrating Waste Management its Synroc small-scale demonstration plant with a larger plant where alternative calcination methods will be developed and studied. IAEA BULLETIN, 4/1989 Features • Most countries with nuclear power programmes are developing technology for deep geologic disposal facili- ties for high-level radioactive waste (HLW). The factors Synthetic rock influencing nuclear waste management depend on the country's policy and involvement in the various stages of At
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