Evaluating Chemical Toxicity of Surface Disposal of LILW-SL in Belgium
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Evaluating Chemical Toxicity of Surface Disposal of LILW-SL in Belgium D. Mallants1 , L. Wang1, E. Weetjens 1 , W. Cool 2 1 Belgian Nuclear Research Centre (SCK•CEN), Boeretang 200, 2400 Mol, Belgium 2 Belgian Agency for Radioactive Waste and Enriched Fissile Materials (ONDRAF/NIRAS), Kunstlaan 14, 1210, Brussel, Belgium ABSTRACT ONDRAF/NIRAS is developing and evaluating a surface disposal concept for low and intermediate level short-lived radioactive waste (LILW-SL) at Dessel, Belgium. In support of ONDRAF/NIRAS's assignment, SCK•CEN carried out long-term performance assessment calculations for the inorganic non-radioactive components that are present in LILW-SL. This paper summarizes the results obtained from calculations that were done for a heavily engineered surface disposal facility at the nuclear zone of Mol/Dessel. The calculations address the migration of chemotoxic elements from the disposed waste to groundwater. Screening calculations were performed first to decide which non-radioactive components could potentially increase concentrations in groundwater to levels above the groundwater standards. On the basis of very conservative calculations, only 6 out of 41 chemical elements could not be classified as having a negligible impact on man and environment. For each of these six elements (B, Be, Cd, Pb, Sb, and Zn), the source term was characterized in terms of its chemical form (i.e., metal, oxide, or salt), and a macroscopic transport model built that would capture the small-scale dissolution processes relevant to element release from a cementitious waste container. Furthermore, reliable transport parameters in support of the convectiondispersion-retardation (CDR) transport calculations were determined. This included derivation of (1) solubility for a cementitious near field environment based on thermodynamic equilibrium calculations with The Geochemist’s Workbench, and (2) distribution coefficients based on a compilation of literature values. Scoping calculations illustrated the effects of transport parameter uncertainty on the rates at which inorganic components in LILW-SL leach to groundwater. INTRODUCTION In the period 1998 to 2006, termed the preliminary project phase, ONDRAF/NIRAS worked in formal partnerships with representatives of four municipalities that hosted nuclear facilities to jointly develop disposal concepts for implementation at a site chosen within their municipal boundaries. Following technical studies and social and political dialogue in Belgium, the government has decided in 2006 that plans should be developed for a near surface disposal facility to accept LILW-SL (category A waste) at a site within the Mol/Dessel nuclear zone. In the project phase, now ongoing, detailed design and safety assessment studies are being carried out starting from the surface facility design developed within the preliminary project phase by the STOLA-Dessel partnership. This design will be the basis for the evaluation of the chemical toxicity of LILW-SL.
LILW-SL is known to contain a large fraction of in
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