Review of Release Evaluation Methodologies

The report describes the state of the art of various release evaluation methodologies used by the different organisations involved in the R2CA H2020 Project for different reactor types (PWR, VVER, EPR and BWR) and accidental scenarios (Loss of Coolant Accidents and Steam Generator Tube Rupture) for Design Basis Accidents ans Design Extension Conditions. It allows to identify the major source of uncertainties where modeling efforts could be made during the project to reduce the degree of conservatism and the use of decoupled approaches  for more realistic release estimates.

The report hightlights that despite sharing some assumptions, the approaches used by the different organisations significantly differs starting from the isotopic inventory definition and the volatile elements considered. For DBA conditions, the evaluations are usually performed with very conservative deterministic assumptions, the majority being based on decoupled approaches.