RELAP5/MOD3.2 Post Test Calculation of the PKL-Experiment PKLIII-B4.3 (NUREG/IA-0170)

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Publication Information

Date Published: December 1999

Prepared by:
L. Karner

Siemens Energierzeugung (KWU)
Freyerslebenstrasse 1
D-91058 Erlangen

Prepared as part of:
The Agreement on Research Participation and Technical Exchange
under the International Code Application and Maintenance Program (CAMP)

Office of Nuclear Regulatory Research
U.S. Nuclear Regulatory Commission
Washington, DC 20555-0001

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The PKL III test facility (Primär-Kreis-Lauf) simulates a typical 1300 MWe Pressurized Water Reactor of Siemens/KWU. In test B4.3, the influence of non-condensables on heat transfer in the steam generators during reflux condenser conditions was investigated.

This report presents the results of a post-test analysis of PKL III-B4.3 using RELAP5/Mod 3.2. A description of the input model is given, and the correspondence of measured and calculated results is discussed.

The results of the calculation show differences in the distribution of nitrogen in the primary system compared to the experiment. When nitrogen was injected into the hot leg of the primary system, the heat transfer in the affected steam generator decreased. In contrast to the experiment RELAP calculated that the volumes in the adjacent steam generator did not get the full amount of nitrogen and that nitrogen was transported from the steam generators to other locations during the course of the transient. Thus the heat transfer in these steam generators later increased in contradiction to the measured values.

In the steam generator tubes, RELAP calculated that the nitrogen accumulates in the descending part as predicted in the experiment. For the ascending U-tubes RELAP predicted that the nitrogen was transported to the loop seal, which was not seen in the experiment.

Fluctuations occured during the course of the RELAP5/Mod 3.2 analysis of the PKLIII B4.3 experiment. This phenomenon may be the main reason, that RELAP calculates the transport of nitrogen from the steam generators into the system and predicts finally a homogeneous distribution of nitrogen in the primary system. The analysis performs an inkind contribution to the CAMP contract.

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