WASTE MANAGEMENT AND DISPOSAL

Radioactive waste has become a focus of some environmental concerns in con-nection with nuclear power. The main feature of wastes from nuclear power plants is that they arise in small quantities, which therefore can be more easily managed and disposed of. Box 3 compares the annual amounts of wastes from nuclear and coal fired power plants for the same electricity production.

Another perspective on the small amounts of wastes produced by nuclear power plants is given by some data from France, where over 75% of all electricity is produced by nuclear reactors. The following amounts of waste products arise annually per capita:

— 360 kg of domestic wastes;

— 7300 kg of agricultural wastes;

— 3000 kg of industrial wastes, of which 100 kg are toxic;

— 1.4 kg of radioactive wastes, of which 20 g are highly radioactive and only 1 g is long lived, requiring special attention for that reason.

disposal to which utilities, hospitals, industries, etc., can send their wastes, usually on a charge basis. Some countries have even set up separate organizations for LLW and HLW. It is common for these organizations to be charged with planning waste management operations outside the waste producing institutions, notably the power plants, including intermediate storage, and performing all prepara-tory research and investigations for disposal, in addition to the actual waste management operations.

5.1.1. Low and Intermediate Level Wastes

Well before a country considers developing a nuclear power programme, it will have been using radioisotopes and radiation sources in medicine, industry and research and there should therefore be a system in place for management of LLW arising from these uses, involving regulations, approved practices, storage and possi-bly LLW disposal. Experience from countries which have LLW disposal tends to indi-cate that establishment of an LLW disposal operation at an early stage to some extent may ease the waste issue, but it has to be borne in mind that any waste disposal sit-ing may involve much the same policy considerations as the sitsit-ing of a power plant (Section 7.1.1).

Operational radioactive waste from nuclear power plants is often treated (to reduce its volume) and/or conditioned ('immobilized', i.e. converted to a mechani-cally stable and insoluble form, and then packaged) prior to its disposal. Liquid waste is usually concentrated before immobilization. The volume of solid waste can be reduced by compaction and/or incineration. This area of LLW and ILW management, having been established and proven over the past forty years, is considered to be mature in terms of technology development. As a result, several effective, safe and feasible treatment and conditioning options exist for these types of waste.

Well proven technology is now being used for the disposal of LLW and ILW from nuclear power plant operation. The most common methods for LLW and some ILW involve shallow land burial in concrete lined trenches or disposal in structures on the ground surface. Safe near surface disposal of LLW and ILW has been practised in a number of countries for about thirty years. The rationale behind near surface disposal is that the time for which this type of waste needs to be kept isolated is relatively short (from one hundred to a few hundred years), and thus it is likely that the institutional or administrative control of the disposal site can be ensured during that period. Countries are continuing to rely on a combination of near surface and subsurface facilities for disposal of LLW and ILW, but are placing increased reliance on the use of engineered barriers to isolate the wastes. Some countries, including Sweden, dispose of LLW and ILW at much greater depths either because of a lack of suitable near surface locations or for reasons of national policy.

5.1.2. High Level Waste

Methods for immobilizing HLW are also available. With regard to permanent disposal of HLW, there is broad agreement among scientific organizations around the world that deep geological disposal is a suitable method for permanently isolating radioactive waste from the environment. Much development work has been done to validate the technology and demonstrate feasibility in model facilities.

There are many geologically suitable sites available for repositories for perma-nent disposal of HLW. However, the issues of public acceptance are considerable. The safety of deep geological disposal is achieved by the use of multiple barriers, includ-ing the waste form itself, corrosion resistant canisters, backfillinclud-ing and sealinclud-ing mate-rials placed in the excavations, and the geological medium in which the repository is built. Repositories are typically planned to be constructed at a depth of several hundred to one thousand metres in media such as granite or other crystalline rocks, bedded or domed salt formations, argillaceous deposits (e.g. clay or shale) or volcanic deposits (e.g. basalt or welded tuff). Several countries plan to operate deep geo-logical repositories for disposal of their spent fuel and HLW in the next twenty to thirty years.

Not all countries with nuclear power programmes would necessarily have suit-able geological formations for disposal of HLW. The problem could be more easily solved through international co-operative ventures for the back end of the fuel cycle, involving intermediate storage of spent fuel, possible reprocessing and MOX fabrica-tion where desirable, and disposal of HLW. However, there is now a general interna-tional position that each country should take care of its own radioactive wastes and this will have to be taken into account.

There is currently no final repository for HLW in operation but the technol-ogy of multilayered natural and engineered barriers which can be used is well stud-ied. Although there is no urgent need to begin HLW disposal it would be highly desirable if at least one government were to start disposal on a pilot scale to demon-strate confidence in the technical solutions which exist. Sweden plans to do this before 2005.