RELAP5/MOD2 calculations of OECD LOFT test LP-SB-2

Technical Report · Sun Apr 01 04:00:00 EDT 1990

DOI:https://doi.org/10.2172/7048769· OSTI ID:7048769

Hall, P C ^[1]

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1. Central Electricity Generating Board, Barnwood (UK). Generation Development and Construction Div.

To help in assessing the capabilities of RELAP5/MOD2 for PWR Fault Analysis, the code is being used by CEGB to simulate several small LOCA and pressurized transient experiments in the LOFT experimental reactor. The present report describes an analysis of small LOCA test LP-SB-02, which simulated a 1% hot leg break LOCA in a PWR, with delayed tripping of the primary coolant pumps. This test was carried out under the OECD LOFT Programme. An important deficiency identified in the code is inadequate modelling of the quality of the fluid discharged from the hot leg into the break pipework. This gives rise to large errors in the calculated system mass inventory. The effect of using an improved model for vapor pull-through into the break is described. A second significant code deficiency identified is the failure to predict the occurrence of stratified flow in the hot leg at the correct time in the test. It is believed that this error contributed to gross errors in the loop flow conditions after about 1300s. Additional separate effects data necessary to resolve the code deficiencies encountered are identified.

• Research Organization: Nuclear Regulatory Commission, Washington, DC (USA). Office of Nuclear Regulatory Research; Central Electricity Generating Board, Barnwood (UK). Generation Development and Construction Div.
• Sponsoring Organization: NRC
• OSTI ID: 7048769
• Report Number(s): NUREG/IA-0021; ON: TI90009567
• Country of Publication: United States
• Language: English

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