This project was performed within the fifth and final phase of sub-project RAK-2.1 of
the Nordic CO-operative Reactor Safety Program, NKS. RAK-2.1 has also included
studies of reflooding of degraded core, recriticality and late phase melt progression.
Earlier source term calculations for Swedish nuclear power plants are based on the
integral code MAAP. A need was recognised to compare these calculations with
calculations done with mechanistic codes. In the present work SCDAP/RELAP5 and
CONTAIN were used.
Only limited results could be obtained within the frame of RAK-2.1, since many
problems were encountered using the SCDAP/RELAP5 code. The main obstacle was
the extremely long execution times of the MOD3.1 version, but also some dubious
fission product calculations. However, some interesting results were obtained for the
studied sequence, a total loss of AC power. The report describes the modelling
approach for SCDAP/RELAP5 and CONTAIN, and discusses results for the transient
including the event of a surge line creep rupture.
The study will probably be completed later, providing that an improved
SCDAP/RELAP5 code version becomes available .