[en] Short communication

[en] Golder Associates has developed a project planning methodology designed particularly for projects with significant uncertainties attached, such as the siting of nuclear waste facilities. It was used to evaluate alternative strategies for obtaining the licence to open the Waste Isolation Pilot Plant (WIPP), the proposed US repository for transuranic waste. (Author)

[en] This paper briefly reviews the sources of uncertainty in performance assessment analyses and discusses the role that sensitivity and uncertainty methods play in the DOE's effort to develop and license a nuclear waste repository in a geologic medium. In keeping with the focus of this conference, these topics are related primarily to groundwater movement and radionuclide transport analyses. Because methods for quantifying uncertainty exist and are applied primarily for uncertainties arising from spatial variability, and to a lesser degree alternative conceptual models, much discussion in this paper regards these uncertainties. Other types of uncertainty may be equally or more important, but less information is available

[en] Short communication

[en] Male Wistar rats were restricted on iodine intake by feeding pure diets, without iodine addition. The high fat diet contained 50% fat (HFD), the low fat diet 3% fat(LFD). Control animals received the same diets, but with iodine addition. After feeding the diets for 7 or 19 weeks liver deiodinase activity was estimated. The iodine deficient animals showed a diminished enzyme activity in both diet groups. But after feeding the diet without iodine addition for 7 weeks the deiodinase activity significantly decreased in the HFD-group only in relation to liver weight per 100 g body weight. After 19 weeks the liver deiodinase activity in the HFD-group was diminished significantly, but the decrease was much smaller than in the LFD-group. The estimation of relative thyroid weight and iodoamino acid distribution demonstrate that the level of iodine deficiency was in iodine restricted HFD-rats greater than in appropriate LFD-rats. This result was verified by investigations of thyroidal radio iodine uptake and iodine content, PB¹³¹I, serum iodine and T₄ levels in both diet groups. The reason for the lower decrease of deiodinase activity at higher iodine deficiency in HFD-rats as compared to LFD-rats and the possible importance of food enriched with fat in endemic goiter areas is discussed. (author)

[en] The objective of the present study is to construct three-dimensional geological and structural models to be used within the SKI SITE-94 project as a base for modelling hydrogeological, hydrochemical, and rock mechanical bedrock conditions, mass transport and layout of a hypothetical repository. The basic input data in the SITE-94 geological and structural models are restricted to geological and structural readings and geophysical measurements made prior to building the Hard Rock Laboratory. 114 refs, 82 figs, 28 tabs

[en] This report concerns a study which is part of the SKI performance assessment project SITE-94. SITE-94 is a performance assessment of a hypothetical repository at a real site. The main objective of the project is to determine how site specific data should be assimilated into the performance assessment process and to evaluate how uncertainties inherent in site characterization will influence performance assessment results. Other important elements of SITE-94 are the development of a practical and defensible methodology for defining, constructing and analyzing scenarios, the development of approaches for treatment of uncertainties, evaluation of canister integrity, and the development and application of an appropriate Quality Assurance plan for Performance Assessments. (111 refs.)

[en] Modeling Research Group 3 has identified a number of general areas for which technical questions remain unanswered. The group further ranked the areas in order of preceived importance. In each area a number of specific questions were raised and in some cases, a strategy was proposed to address those questions. The following issues and concerns are discussed: flow behavior in fractures and fracture/matrix interactions; model validation; need for new and improved modeling; treatment of uncertainty; scale effects; preferential pathways for flow and transport; scenario development and description;definition and treatment of model boundary conditions; treatment of system heterogeneity; experimentation related to modeling; engineering measures to improve performance of the natural barrier

[en] During the period from 1977-1986 SKB (Swedish Nuclear Fuel and Waste Management CO) performed surface and borehole investigations of 14 study sites for the purpose of assessing their suitability for a repository of spent nuclear fuel. The next phase in the SKB site selection programme will be to perform detailed characterization, including characterization from shafts and/or tunnels, of two or three sites. The detailed investigations will continue over several years to provide all the data needed for a licensing application to build repository. Such an application is foreseen to be given to the authorities around the year 2003. It is presently not clear if anyone of the study sites will be selected as a site for detailed characterization. Other sites with geological and/or socio-economical characteristics judged more favourable may very well be the ones selected. However, as a part of the background documentation needed for the site selection studies to come, summary reports will be prepared for most study sites. These reports will include scope of activities, main results, uncertainties and need for complementary investigations. This report concerns the Fjaellveden study site. (au)

[en] A simple evaluation of groundwater flux and potential for radionuclide transport at the Aespoe site, from fundamental hydrologic principles, indicates that, based upon data that are available from surface-based investigations, it is not possible to confirm that the bedrock has a high capacity to retard radionuclide release to the surface environment. This result is primarily due to the high spatial variability of hydraulic conductivity, and high uncertainty regarding the relationship among hydrologic and transport parameters within conductive elements of the bedrock. A comparison between Aespoe and seven other study sites in Sweden indicates that it is difficult or impossible to discriminate among these sites in terms of the geologic barrier function, based upon the types of data that are available from present-day methods of site characterization. Groundwater flux is evaluated by a one-dimensional application of Darcy's law to a set of simple, potential pathways for groundwater flow from the repository, which are chosen to yield an appraisal of the wide bounds of possible system behaviour. The configurations of the pathways are specified based on simple assumptions of flow-field structure, and hydraulic driving forces are specified from consideration of regional and local topographic differences. Results are expressed in terms of a parameter group that has been shown to control the barrier function. Comparisons with more detailed hydrological modelling of Aespoe show that, although a reduction in uncertainty is achieved, this reduction is not sufficient to distinguish between good and poor performance of the geologic barrier at the site. 38 refs