2012:58 Technical Note, Independent radionuclide transport modelling – Reproducing results for main scenarios

As part of the initial technical review of SR-Site, we applied a simplified model to approximate Swedish Nuclear Fuel and Waste Management Company (SKB) computations related to the transport of radionuclides at the planned KBS–3 repository at the Forsmark site in Sweden. The objective was to provide insights and recommendations to the Swedish Radiation Safety Authority (SSM) on potential clarifications and complementary information to be supplied by SKB, and identify

critical topics requiring further examination during the detailed review phase.

The specific objective of this task was to build a model to approximate a subset of calculation cases documented in the SKB Radionuclide Transport Report for the Safety Assessment SR-Site (SKB, 2010a), hereafter referred to simply as the “Radionuclide Transport Report.” The modelling focused on two scenarios: (i) Canister Failure by Corrosion and (ii) Canister Failure by Shear Load, to evaluate whether SKB computations of releases of radionuclides from breached canisters and the transport of these radionuclides in the groundwater to the biosphere are appropriate to support the safety assessment documented in the SR-Site main report (SKB, 2011).

The review evaluated (i) transparency of the SKB computations (e.g., are data and descriptions sufficient to reproduce computations?), (ii) appropriateness of the SKB performance assessment computations (e.g., are there any computations that could bias safety conclusions; are simplifications and assumptions made for the performance assessment appropriate?), and (iii) description of the overall SKB performance assessment (e.g., what key factors control dose estimates?). Neither adequacy of the input data nor the adequacy of the biosphere model was evaluated in this task.