Fission product release from nuclear fuel II. Validation of ASTEC/ELSA on analytical and large scale experiments

• A wide range of experiments is presented for the ASTEC/ELSA code validation.
• Analytical tests such as AECL, ORNL and VERCORS are considered.
• A large-scale experiment, PHEBUS FPT1, is considered.
• The good agreement with measurements shows the efficiency of the ASTEC modelling.
• Improvements concern the FP release modelling from MOX and high burn-up UO2 fuels.

This article is the second of two articles dedicated to the mechanisms of fission product release from a degraded core. The models of fission product release from nuclear fuel in the ASTEC code have been described in detail in the first part of this work (Brillant et al., this issue). In this contribution, the validation of ELSA, the module of ASTEC that deals with fission product and structural material release from a degraded core, is presented. A large range of experimental tests, with various temperature and conditions for the fuel surrounding atmosphere (oxidising and reducing), is thus simulated with the ASTEC code. The validation database includes several analytical experiments with both bare fuel (e.g. MCE1 experiments) and cladded fuel (e.g. HCE3, VERCORS). Furthermore, the PHEBUS large-scale experiments are used for the validation of ASTEC. The rather satisfactory comparison between ELSA calculations and experimental measurements demonstrates the efficiency of the analytical models to describe fission product release in severe accident conditions.