COBRA-NC code analysis of the Heissdampfreaktor (HDR) containment building following a small steam line break: Final report

Technical Report · Sat Nov 01 04:00:00 EST 1986

OSTI ID:7173238

Krotiuk, W J

COBRA-NC is a digital computer code that simulates the response of multicompartment light water reactor containments, and other buildings to postulated pipe breaks. The code has been used to perform post-test predictions of the response of the German HDR containment to a simulated small steam line break blowdown. Comparisons of calculated compartment transient pressures, and temperatures have been made with experimentally measured values. The COBRA-NC predictions for containment pressure and temperature agree fairly well with the data for about half the analyzed transient of 1200 seconds. The code correctly predicts the presence of vertical temperature stratification, and the flowing of liquid to the bottom of the containment. However, during the second half of the transient, the calculated results for pressure and temperature increase in magnitude instead of decreasing as shown in the measurements. This divergence is attributed to the lack of heat removal at the outside surface of the modeled HDR containment structure. Specifically, the heat transfer connection between the containment structure and the environment outside of the HDR containment is not specified in the supplied description of the HDR facility; thus, in the analyses performed, all outside surfaces of the modeled containment structures are assumed insulated. The agreement between the COBRA-NC predictions and the experimental measurements during the early part of the analyzed transient does provide optimism in the code's ability to predict small break long term temperature stratification and pressure effects in a multicompartment building, but further work must be performed to verify the code for the prediction of long duration transients.

• Research Organization: Pacific Northwest Lab., Richland, WA (USA); Electric Power Research Inst., Palo Alto, CA (USA)
• DOE Contract Number: AC06-76RL01830
• OSTI ID: 7173238
• Report Number(s): EPRI-NP-4941; ON: DE87004110
• Country of Publication: United States
• Language: English

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