TRAP-MELT3 calculations on an intermediate LOCA at the Loviisa nuclear power plant

Calculations are performed on a hypothetical severe accident at the Finnish LOVIISA VVER-440 nuclear reactor. The accident considered is an intermediate LOCA with loss of AC power (S1B). The code applied is TRAP-MELT3. The necessary MARCH3 data on thermal hydraulics and on fission product release from the damaged core were supplied by B.F.Schougaard, ELSAM. Output includes data for release of fission products to the containment and for the fission product retention in the primary system. For CsI, CsOH, and Te condensation on the walls is the most important retention mechanism, and retentions of 30-60 per cent are obtained. For low-volatiles only aerosol behaviour is considered and retentions of 8-30 per cent are obtained. A factor, which further limits the release is the low release of several species from the core. (orig.)