Uncertainty and sensitivity analysis of radionuclide migration through the engineered barriers of deep geological repository: Case of RBMK-1500 SNF. (April 2015)

• Record Type: Journal Article
• Authors: Narkuniene, Asta; Poskas, Povilas; Kilda, Raimondas; Bartkus, Gytis
• Is Part Of: Reliability engineering & system safety. Volume 136(2015:Apr.)
• Page Start: 8
• Page End: 16
• Publication Date: 2015-04
• Subjects: RBMK-1500 spent nuclear fuel -- Geological disposal -- Uncertainty -- Sensitivity -- Radionuclide migration; Reliability (Engineering) -- Periodicals; System safety -- Periodicals; Industrial safety -- Periodicals; Fiabilité -- Périodiques; Sécurité des systèmes -- Périodiques; Sécurité du travail -- Périodiques; 620.00452
• DOI: 10.1016/j.ress.2014.11.011
• Languages: English
• ISSNs: 0951-8320

Abstract

Abstract: Like other nuclear countries, Lithuania is facing the problem of spent nuclear fuel (SNF) disposal from RBMK 1 -1500 type reactors at the Ignalina NPP (~22, 000 of the SNF assemblies). The application of probabilistic and deterministic methods for uncertainty assessment and important parameter ranking is of high importance in order to build confidence in the assessment results on radionuclide migration and indicates directions for further uncertainty reduction. This study is devoted to the uncertainty and sensitivity analysis of radionuclide migration through the engineered barriers of a conceptual geological repository for RBMK-1500 SNF disposal. The analysis was performed using computer codes AMBER (United Kingdom) and MATLAB (Sweden). The analysis showed that the uncertainty of defect enlargement time had no significant impact on 129 I and 226 Ra peak flux from the engineered barriers yet it was an important parameter for time dependent mean flux of 129 I. Sensitivity analysis revealed that in the case of 129 I peak flux, further investigations should be oriented to more precise determination of diffusion coefficient in bentonite, instant release fraction and SNF dissolution rate. In the case of 226 Ra, efforts to reduce the uncertainty of SNF dissolution rate, sorption coefficient in bentonite and equivalent flow rate should be made. Highlights: Importance of uncertainty of main transport related parameters is nuclide specific. Parameter ranking varies for performance metrics (peak flux, time dependent flux). Uncertainty of defect enlargement is important for the mean flux of 129 I. 129 I and 226 Ra peak flux is insensitive to defect enlargement time.