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ECN publication
Post-test analysis of PANDA test P4 [ECN-C--98-104 ; INNO-TEPSS(98)-D19]
Published by: Publication date:
ECN NUC 1999
ECN report number: Document type:
ECN-C--98-104 ECN publication
Number of pages: Full text:
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The results of a post-test analysis of the integral system test P4, whichhas been executed in the PANDA facility at PSI in Switzerland within the framework of Work Package 2 of the TEPSS project are presented. The post-test analysis comprises an evaluation of the PANDA test P4 and a comparison of the test results with the results of simulations using the RELAPS/MOD3.2, TRAC-BF1, and MELCOR 1.8.4 codes. The PANDA test P4 has provided data about how trapped air released from the drywell later in the transient affects PCCS performance in an adequate manner. The well-defined measurements can serve as an important database for the assessment of thermal hydraulic system analysis codes, especially for conditions that could be met in passively operated advanced reactors, i.e. low pressure and small driving forces. Based on the analysis of the test data, the test acceptance criteria have been met. The test P4 has been successfully completed and the instrument readings were with the permitted ranges. The PCCs showed a favorable and robust performance and a wide margin for decay heat removal from the containment. The PANDA P4 test demonstrated that trapped air, released from the drywell later in the transient, only temporarily and only slightly affected the performance of the passive containment cooling system. The analysis of the results of the RELAPS code showed that the overall behaviour of the test has been calculated quite well with regards to pressure, mass flow rates, and pool boil-down. This accounts both for the pre-test and the post-test simulations. However, due to the one-dimensional, stacked-volume modeling of the PANDA DW, WW, and GDCS vessels, 3D-effects such as in-vessel mixing and recirculation could not be calculated. The post-test MELCOR simulation showed an overall behaviour that is comparable to RELAPS. However, MELCOR calculated almost no air trapping in the PCC tubes that could hinder the steam condensation rate. This resulted in lower calculated pressure values, i.e. an overestimation of the actual PCC performance. Any stratification of the DW and WW gas space and the WW pool was not calculated by MELCOR since these volumes have been represented by a single node. The TRAC-BF1 calculations show a reasonable agreement with the P4 test, but only a part of the transient as well as part of the system have been analyzed with the code. Because of numerical problems, the wetwells were not included in the TRAC-BF1 model, but were replaced by BREAK components using tabulated pressure values that were based on the experimental results. 21 refs.

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