The temperature rise resulting from the radioactive decay of high level waste may cause geochemical and geomechanical reactions within the host rock, which are important for the development of final design criteria of a radioactive waste repository. A realistic and acceptable concept for a convincing safety analysis can be derived from the principle of multiple barriers:

  1. separate analysis of the effectiveness of the individual barriers,

  2. analysis of the physical and geochemical processes, which arise as a result of the interrelation between the barriers of different systems,

  3. comprehensive safety analysis of the final repository by identification and evaluation of the combined effects of all barriers under certain theoretically imaqinable events.

Calculations on the thermomechanical effects on the geological barrier and the proof of the integrity of the salt dome over long times are an important part of the safety analysis. A simplified model has been used for non site specific calculations. Some results of the calculation of the thermo-mechanical stress and strain field around the repository are discussed and their importance for the structural stability of the repository and the salt dome will he illustrated.

INTRODUCTION

The safe disposal of radioactive wastes is one of the most important problems of modern technology. In no other engineering project do safety aspects have such a foremost role as they do in waste disposal of atomic power plants. This requires the equal efforts of geo-scientists and engineers. The, in part, controversial and emotionally loaded public discussion on the problem of final storage.of radioactive wastes has given rise to the impression that decisive problems of this complex question were not recognized and that the scientists and experts were suddenly and without preparation confronted with this problem. This impression is wrong. The truth is, that geologists - also engineering geologists and rock mechanical engineers - have been working resolutely and systematically for more than ten years on the concept of final storage. In the Federal Republic of Germany the main emphasis of the research work was placed early upon a final storage in the diapiric salt structures of Northern Germany. This paper is a contribution to the discussion of the feasibility of the final storage concept. The special properties of rock salt, upon which the suitability for a long term safe final storage is based, are presented. Furthermore, unanswered questions and problems will at least be explained by means of examples, a concept for an extensive safety analysis will be presented and also on the basis of a calculation of thermo- mechanical effects, methods of solving the problems will be indicated.

SUITABILITY OF SALT DOMES FOR THE FINAL STORAGE OF RADIOACTIVE WASTES

In the following, final storage is understood to be the maintenance free, safe storage of radioactive wastes. Every final storage concept must therefore, fulfill the requirement that the wastes remain isolated from the biosphere until the activity of the separate radionuclides has subsided to an acceptable level. Depending on the composition of the waste products, this means a period between 103 and 106 years.

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