Geological Problems in Radioactive Waste Isolation A WORLD WIDE REVIEW

The problem of isolating radioactive wastes from the biosphere presents specialists in the fields of earth sciences with some of the most complicated problems they have ever encountered. This is especially true for high level waste (HLW) which must be isolated in the underground and away from the biosphere for thousands of years. The most widely accepted method of doing this is to seal the radioactive materials in metal canisters that are enclosed by a protective sheath and placed underground in a repository that has been carefully constructed in an appropriate rock formation.<br><br>The HLW problem is complicated because of the heat generated during the decay process. If the HLW is not stored at the surface for a lengthy period of time so as to lose much of its thermal generating capacity, the heat released in the underground can raise the temperature of the repository over a long period of time with a maximum increase of as much as 200 C. The projected size of a repository involves a rock volume on the order of a cubic kilometer, and to predict the effects of significantly raising the temperature of the rock by this amount involves a number of complicated questions. To simplify this problem, several countries have decided to store their HLW at the surface for 40 to 50 years to dissipate the generated heat and minimize the temperature increases in the underground repository.<br><br>The first investigations on storing radioactive waste underground were started in United States in the early 1960s in a salt mine near Lyons, Kansas and in West Germany in 1965 using an underground laboratory in the Asse salt mine. The early work at Asse was concerned mainly with various disposal techniques for isolating low level and medium level radioactive wastes in rock salt. Later investigations concentrated on problems concerned with high level waste (Langer el al., 1990). The first effort to study the problems of isolating HLW in granitic rock was initiated in late Spring 1977, when another underground laboratory was set up in an abandoned iron ore mine at Stripa, Sweden. This program was accomplished as part of a Swedish-American cooperative program that was initiated by a bilateral agreement between the U. S. Energy Research and Development Administration (now the U.S. Department of Energy) and the Swedish Nuclear Fuel Supply Company (Wilhcrspoon and Dcgcrman, 1978). The program was later expanded into the International Stripa Project that is still operating today.<br><br>Essentially every country that is generating electricity in nuclear power plants is faced with the problem of isolating the radioactive wastes that are produced. The general consensus is that this can be accomplished by selecting an appropriate geologic setting and carefully designing the rock repository. Much new technology is being developed to solve the problems that have been raised and there is a continuing need to publish the results of new developments for the benefit of all concerned.<br>