Behaviour of fission products under severe PWR accident conditions

The VERCORS programme is an analytical experimental programme focusing on the release of fission products (FP) and actinides from an irradiated fuel rod during a severe accident in a PWR. Following on from the HEVA programme, VERCORS was conducted in a similar manner in a high activity cell at the CEA Grenoble Centre over a 14-year period between 1989 and 2002. A total of 17 tests were carried out, in 3 experimental phases, on a facility that continued to evolve over time. The instrumentation progressively become more sophisticated, thus making it possible to extend the knowledge database to include the transport of FP (HT loop), or on the contrary focus on the release objective by associating the study of actinides (RT loop). The general description of the programme has already been presented in a previously published article, which is the first in a series of three articles on the same subject. The specific behaviour of fission gases (Xe and Kr) and volatile FP (I, Cs, Te, Sb, Ag, Rb and Cd) in terms of global release, release rate and transport is the subject of this second article. The third and the final part of this series of articles focusing on the VERSCORS programme will study the release of actinides and less volatile FP, respecting the classification previously identified, i.e. (1) semi-volatile FP composed of Mo, Ba, Rh, Pd, Tc, (2) very low-volatile FP composed of Sr, Y, Nb, Ru, La, Ce, Eu, and finally (3) non-volatile FP composed of Zr, Nd and Pr.