Post-test analyses of PANDA Test P7

The TEPSS project (Technology Enhancement for Passive Safety Systems) is a part of the European Research Framework Program. The objective of TEPSS project is to make significant additions to the technology related to advanced passive type Boiling Water Reactor (BWR) designs. Work Package 2 of the TEPSS project is concentrated on the PANDA test facility (Passive Decay Heat Removal and Depressurization Test Facility). The facility has been constructed at the Paul Scherrer Institute, Switzerland. A series of experiments (the P-series tests) has been performed at the PANDA facility within the TEPSS project. This report contains results of the post-test analytical simulation of the PANDA Integrated System Test P7. Simulations have been performed using the following computer codes: MELCOR 1.8.3, RELAP5/Mod3.2, TRAC-BF 1. Results of the calculations are compared to the measured data. Generally the results obtained with the codes are m agreement with experimental data. Sources of discrepancies between code results and experimental data are well understood. It has been observed that 'lumped parameter' codes, e.g. MELCOR, may have troubles if large degree of stratification develops in some parts of the system. On the other hand 'field codes', e.g. RELAP or TRAC, can only represent single non-condensable gas, which leads to troubles when a light gas (in case of P7 helium) is injected into steam-air atmosphere. In case of the TRAC code, a full scope analysis of the P7 test was not possible because of numerical problems. Only part of the system was modelled. It is therefore concluded that the MELCOR and RELAP codes can be used to simulate the behaviour of BWR containment with passive decay heat removal systems. Troubles encountered during TRAC-BF1 simulation make it doubtful whether the code is a useful tool for this kind of analysis. 16 refs