Application of Decision Tree Technique to Sensitivity Analysis for Results of Radionuclide Migration Calculations

Nakajima, Kunihiko*; Makino, Hitoshi 

Uncertainties are always present in the parameters used for the nuclide migration analysis in the geological disposal system. These uncertainties affect the result of such analyses, e.g., and the identification of dominant nuclides. It is very important to identify the parameters causing the significant impact on the results, and to investigate the influence of identified parameters in order to recognize R&D items with respect to the development of geological disposal system and understanding of the system performance. In our study, the decision tree analysis technique was examined in the sensitivity analysis as a method for investigation of the influences of the parameters and for complement existing sensitivity analysis. As a result, results obtained from Monte Carlo simulation with parameter uncertainties could be distinguished with not only important parameters but also with their quantitative conditions (e.g., ranges of parameter values). Furthermore, information obtained from the decision tree analysis could be used 1) to categorize the results obtained from the nuclide migration analysis for a given parameter set, 2) to show prospective effect of reduction to parameter uncertainties on the results.