United States Nuclear Regulatory Commission - Protecting People and the Environment

RELAP5/MOD3.2 Assessment Using GERDA Small Break Test, 1605AA (NUREG/IA-0166)

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Publication Information

Date Published: July 1999

Prepared by:
W. Tietsch

ABB Reaktor GmbH
Dudenstrassee 44
D–68176 Mannheim, Germany

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 Small Break Loss of Coolant Accident (SBLOCA) Test Facility GERDA (Geradrohr Dampferzeuger Anlage) was designed to evaluate the post SBLOCA thermal-hydraulic events expected to occur in the German Mülheim-Kärlich plant. The scaled in volume 1:1 in height Test Facility was built and tested by B&W at the Alliance Research Centre (ARC) under contract of BBR (Brown Boveri Reaktor GmbH) now ABB Reaktor GmbH (Ref. /1/,/2/). The objective of the whole test program was to obtain detailed experimental data for the evaluation of single and composite SBLOCA phenomena and for the verification and the refinement of the analytical tools and models used to predict plant performance during SBLOCA transients.

This report presents the results of RELAP5/MOD3.2 assessment on the integral (composite) GERDA Test 1605AA which features a complete sequence of a 10 cm2 Reactor Vessel Leak transient conducted on April 12th, 1983. The purpose of the assessment analysis was to determine whether the tested RELAP version can predict the major phenomena of this complex transient and to provide some useful information both to code developers and analysts for the application on SBLOCA transients in 'Once-Through-Steam-Generator' Plants.

The results of the post test calculations were compared to the test data. This comparison has shown that in general most of the important phenomena are predicted quite well. However differences in details such as timing of key sequences and some disagreements, such as over and under predictions of certain key parameters were observed. In general it was concluded from the comparison that the predictability of such complex transients, especially the BCM (boiler-condenser) phase, is fairly good. However there were several deficiencies discovered mainly in predicting OTSG behaviour, leak flow and the refill phase during SBLOCA in an OTSG plant These finding should be used as a target for further fine tuning and enhancements of the code.

Additionally this report presents some base calculations identified as conditioning calculations of OTSG steady state and transient behaviour which is one of the essentials for the prediction of phenomena observed in the SBLOCA scenarios.

Finally a complete input listing of the RELAP5MOD3.2 GERDA model is included in appendix B.

The analysis presented here and the report is an inkind contribution to the CAMP contract.

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