The Influence of Accident Measures on the Source Term at Loss-of-Coolant Accidents in VVER-1000 Reactors

The source term released during a severe accident can be mitigated by accident management measures. Since several years we investigated the influence of a number of accident mangement strategies on the source term in a VVER-1000-type reactor using the Source Term Code Package (STCP). For each set of calculations recommendations have been formulated to minimize the radioactive releases to the environment. After investigating the "Station Blackout" (TMLB´)- sequence in the past a large break loss of coolant accident (AB-sequence) was selected as the basis of a new study. In this study five scenarios with different availability of ECC- and spray water are investigated depending on the onset of the core-concrete interaction (CCI) in the cavity. A comparison of the resulting source terms with those obtained in the calculations for the "Station Blackout' - sequence shows differences in both the time and the magnitude of a number of events. All the total releases during the AB-sequence are higher than in the TMLB'-sequence. This paper demonstrates the application of a Western code for safety assessment of Russian-design reactors.