The Study on Uranium Waste Disposal Repository(Phase 2)

Saito, Shigeyuki*; Ikuse, Hiroyuki*

(1)study on disposal condition of uranium-bearing waste. Performance of daughter nuclides in uranium-bearing disposal (into approximately-100m-depth) is estimated by investigation of differential equation. And relationship between variation of parameter and dose rate is investigated form the point of release coefficient, solubility, infiltration, water velocity, distribution coefficient (Kd), distance to river. Influence to daughter nuclides in case of shift of Kd is investigated. If Kd of daughter nuclides are smaller than that of parent nuclide, daughter nuclides may travel without radioactive equilibrium. Furthermore, the less is the distance to river, the more is maximum dose rate, when assessment duration is limited. (2)study on concentration and flux of natural radioactive elements Concentration data of natural radionuclides and some chemical species have been examined regarding Japanese geological environment by literature survey, and the characteristics of their statistical distributions have been obtained using a method of statistical analysis. Deep considerations have been made on the characteristics and their related factors on each geological environment based on the information of chemical species and geological characteristics. Furthermore, a hypothetical methodology of an assessment of natural fluxes which reflect geological environments in Japan has been presented for a description of credibility and applicability of natural safety indicators by considering a timescale of an assessment, information of data acquisition mehtod and data accumulation, credibility of matter cycle, and differences of areas for the assessment.