Enhancement of the methodology of repository design and post-closure performance assessment for preliminary investigation stage, 3; Progress report on NUMO-JAEA collaborative research in FY2013 (Joint research)

Shibata, Masahiro; Sawada, Atsushi; Tachi, Yukio; Makino, Hitoshi; Wakasugi, Keiichiro; Mitsui, Seiichiro; Kitamura, Akira; Yoshikawa, Hideki; Oda, Chie; Ishidera, Takamitsu; et al.

JAEA-Research 2014-030, 457 Pages, 2015/03

JAEA-Research-2014-030.pdf:199.23MB

JAEA and NUMO have conducted a collaborative research work which is designed to enhance the methodology of repository design and post-closure performance assessment in preliminary investigation stage. With regard to (1) study on rock suitability in terms of hydrology, based on some examples of developing method of hydro-geological structure model, acquired knowledge are arranged using the tree diagram, and model uncertainty and its influence on the evaluation items were discussed. With regard to (2) study on scenario development, the developed approach for "defining conditions" has been reevaluated and improved from practical viewpoints. In addition, the uncertainty evaluation for the effect of use of cementitious material, as well as glass dissolution model, was conducted with analytical evaluation. With regard to (3) study on setting radionuclide migration parameters, based on survey of precedent procedures, multiple-approach for distribution coefficient of rocks was established, and the adequacy of the approach was confirmed though its application to sedimentary rock and granitic rock. Besides, an approach for solubility setting was developed including the procedure of selection of solubility limiting solid phase. The adequacy of the approach was confirmed though its application to key radionuclides.

Scenario development for the risk-informed safety assessment of geological disposal

Makiuchi, Akie*; Ishida, Keisuke*; Kurosawa, Susumu*; Inagaki, Manabu*; Umeki, Hiroyuki*; Ebashi, Takeshi; Wakasugi, Keiichiro; Makino, Hitoshi; Shibata, Masahiro

no journal, , 

NUMO is developing a safety case for the geological disposal of vitrified high-level radioactive wastes and TRU wastes on the basis of the latest findings. In parallel, JAEA starts to investigate the geological disposal of spent fuel as an alternative disposal option. In such a situation, NUMO and JAEA have jointly established a scenario development method. Since the considerations of both probabilities and influences of scenarios or processes are focused on, the disaggregated approach is adopted. This approach had been recommended by ICRP, and applied to Japanese safety regulations for disposing low-level waste. To efficiently identify processes that may influence geological disposal systems, various supposable processes are analyzed in terms of their probabilities and influences on the safety function by conducting audits using FEP information. One remarkable feature of this method is its demand of high-level traceability of various judgments through analysis and definition of scenarios. Traceability is ensured by various tools and/or products. One such example is a "Safety Function/Variable/Process Diagram", which structurally illustrates interrelations between safety functions, processes and variables of geological disposal systems. This presentation will show the features of the abovementioned method in detail along with some examples of developed scenarios.