Additional Media Studies for Site Suitability Criteria

Site suitability studies at LLL to date have considered repositories in bedded salt and shale. The models have been varied to include a number of dimensions, parameter values, histories, and potential failure modes.<br>These model studies have enabled us to provide preliminary site suitability criteria based on parameter sensitivity calculations and to begin uncertainty analyses.<br><br>Inasmuch as in situ tests are either underway or planned for the near future in other geologic environments in the United States, and since these environments may be recommended as waste repositories, work should begin immediately to produce results for these environments that are similar to those we have for the bedded media. Once the necessary data are available and the models developed, advanced analyses can be conducted in parallel with those on shale and bedded salt.<br><br>In this report we consider domed salt, basalt, and crystalline rock, comparing these three media with each other and with bedded salt and shale. Comparisons are made on the following basis:<br><br>1. The estimated level of effort required to develop models for these media that are similar in quality to those now available for bedded salt and shale. The models must therefore consider regional and local migration of wastes, recharge of the repository, dissolution, and other special effects.<br><br>2. Our present state of knowledge about the important physical and chemical properties of these media and the estimated level of effort necessary to develop data bases for each that are comparable to the data base we currently have for bedded salt and shale.<br><br>3. An evaluation of each medium as a suitable repository environment.<br>The evaluation is based on construction costs, colocation of other resources, availability of potential repository sites, retrievability of stored wastes, and suitability of physical and chemical properties. <br><br>We have reached two principal conclusions on the basis of this study.<br><br>1. The funding necessary to bring our understanding of domed salt, basalt, and crystalline rock to a level comparable to our current understanding of bedded salt is estimated to be $1457K, $813K, and $1742K, respectively, for the three media. In each case, roughly 75% of the effort would be devoted to model development and analysis, 25% to data base development.<br><br>2. Basalt and crystalline rock are about equally suitable as waste repositories in terms of all criteria except the availability of potential repository sites, where crystalline rock has a clear advantage. Domed salt should yield substantially lower construction costs than basalt or crystalline rock, but it is inferior in the categories of colocated resources and waste retrievability, and probably suitability of chemical and physical properties.<br><br>The funding estimates reflect not only the effort and time required for each medium study, but also the probable DOE schedule for experimental pilot plant work and for potential repository development. The studies should begin simultaneously, allowing them to be completed in the order: basalt, domed salt, crystalline rock. Hydrology studies and systems model development will be an extension of work either already completed or in progress at LLL. If studies of other environments and media become necessary, they can be made in the same way.<br>