Probability density functions for radionuclide migration properties of cementitious materials and their application in safety assessment

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Abstract

Post-closure safety assessment for repositories of radioactive waste includes long-term radionuclide release modelling from a multi-barrier surface or deep repository to the geosphere and biosphere. Modelling of the complex and interacting physical and chemical processes governing radionuclide migration in the near field of a repository requires adequate models and model parameters. This paper discusses a data collection and analysis procedure that is implemented in the safety assessment methodology developed at SCK•CEN in collaboration with ONDRAF/NIRAS. The emphasis here is on flow and transport parameters characteristic of cementitious materials such as structural concrete, concrete waste containers, and cementitious buffer material. The methodology for deriving best estimate parameters together with their probability density functions (pdfs) will be illustrated for the following parameters: K (saturated hydraulic conductivity), Dp (pore-water diffusion coefficient), Kd (distribution coefficient), and Cs (solubility). Best estimate values for parameters Dp, Kd, and Cs and their pdfs are discussed for sixteen radionuclides typical of low- and intermediate level short-lived radioactive waste. Data for this analysis was compiled from a literature review. Applications address radionuclide migration calculations from a surface repository to groundwater by means of a state-of-the-art numerical code. The results discussed include stochastic uncertainty and sensitivity analysis using the derived parameter pdfs. Results from sensitivity analysis show that, among the parameters tested, the variation in distribution coefficient Kd has the largest effect on radionuclide fluxes from the repository.

Details

Original languageEnglish
Title of host publicationProbability density functions for radionuclide migration properties of cementitious materials and their application in safety assessment
Place of PublicationBelgium
Pages1-10
Publication statusPublished - Sep 2005
EventICEM 2005 -10th International Conference on Environmental Remediation and Radioactive Waste Management - ICEM - International Conference on Environmental Management, Glasgow, Scotland, United Kingdom
Duration: 4 Sep 20058 Sep 2005

Conference

ConferenceICEM 2005 -10th International Conference on Environmental Remediation and Radioactive Waste Management
CountryUnited Kingdom
CityGlasgow, Scotland
Period2005-09-042005-09-08

Keywords

  • waste disposal, engineered barriers, safety data, performance assessment, data collection forms, concrete

ID: 201434