Development of an advanced support system for site investigations

JAEA has the responsibility for R&D to enhance reliability of High Level Waste (HLW) disposal technology and to develop safety assessment methodology with associated databases; these should support both the implementer (NUMO) and the relevant regulatory organizations. With this responsibility, JAEA has initiated development of advanced technology in the field of Knowledge Engineering. Known as the Information Synthesis and Interpretation System (ISIS), it incorporates knowledge currently being obtained in the Underground Research Laboratory (URL) projects in Expert System (ES) modules for the Japanese HLW disposal program. This knowledge includes fundamental understanding of relevant geological environments, technical know-how for the application of complex investigation techniques, experience gained in earlier site work, etc. However, much knowledge is not undocumented because the knowledge is treated as tacit knowledge and, without focused action soon, may be permanently lost. Therefore, a new approach is necessary to transfer the knowledge obtained in these URL projects to support the site characterization and subsequent safety assessment of potential repository sites by NUMO and the formulation of guidelines by regulatory organizations. In this paper, we introduce the ES for selecting tracers for borehole drilling. ES is the system built by applying electronic information technology to support the planning, conducting investigations and assessing of investigation results. Tracers are generally used for borehole drilling to monitor and quantitatively assess the degree of contamination of groundwater by drilling fluid. JAEA uses fluorescent dye as tracer in drilling fluid. When a fluorescent dye is used for drilling, suitable type and concentration must be selected. The technical points to be considered are; 1) linearity of fluorescent spectrum intensity with variations in concentration, 2) pH dependence of fluorescent spectrum intensity, 3) stability of fluorescent dye, 4) sorption/adsorption properties for rock being investigated, 5) detection limit of analyzer, 6) comparison of the fluorescent spectrum with dissolved organics and tracers used in other boreholes. In addition, costs and environmental impact are important factors to be considered. Thus, significant knowledge is needed in selecting the tracer for actual investigations. Fortunately, the ES for tracer selection already contains much knowledge needed. For example, the chemical data set for a suite of fluorescence dyes is in the ES, along with guidelines for their use. Therefore, this ES can support the use of fluorescent dye as tracer in actual investigations, even if the investigating scientists have little or no experience with it. In conclusion, the ES modules are and will be built as a support system for future researchers to perform optimized site investigations in a user-friendly manner. In this paper, we introduce the ES for selection of borehole drilling fluid tracer. Eventually, ES covering the full range of site investigation methods will be developed.