Assessment of RELAP5/MOD3/V5M5 against the UPTF Test No. 11 (countercurrent flow in PWR hot leg)
- Siemens AG-KWU Group, Erlangen (Germany)
Analysis of the UPTF Test No. 11 using the [open quotes]best-estimate[close quotes] computer code RELAP5/MOD3/Version 5M5 is presented. Test No. 11 was a quasi-steady state, separate effect test designed to investigate the conditions for countercurrent flow of steam and saturated water in the hot leg of a PWR. Without using the code's new countercurrent flow limitation (CCFL) model, RELAP5/MOD3/V5M5 overestimated the mass flow rate of back down flowing water up to 35% (1.5 MPa runs) and 43% (0.3 MPa runs). This is the most obvious difference to RELAP5/MOD2, which did not allow enough countercurrent flow. From the point of view of performing plant calculations this is certainty an improvement, because the new junction-based CCFL option could be used to restrict the flows to a flooding curve defined by a user-supplied correlation. Very good agreement with the experimental data for 1.5 MPa -- which are relevant for SBLOCA reflux condensation conditions -- could be obtained using the code's new CCFL option in the middle of the inclined part (riser) of the hot leg. Using the same CCFL correlation for the simulation of 0.3 MPa test series -- typical for reflood conditions -- the code underestimated by 44% the steam mass flow rate at which complete liquid carry over occurs. An unphysical result was received using a CCFL correlation of the Wallis type with the intercept C = 0.644 and the slope m = 0.8. The unphysical prediction is an indication of possible programming errors in the CCFL model of the RELAP5/MOD3/V5M5 computer code.
- Research Organization:
- Nuclear Regulatory Commission, Washington, DC (United States). Office of Nuclear Regulatory Research; Siemens AG Unternehmensbereich KWU, Erlangen (Germany)
- Sponsoring Organization:
- NRC; Nuclear Regulatory Commission, Washington, DC (United States)
- OSTI ID:
- 6357917
- Report Number(s):
- NUREG/IA-0116; KWU--E412/91/E1002; ON: TI93014893
- Country of Publication:
- United States
- Language:
- English
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CONTAINERS
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EXPERIMENTAL DATA
FLOW RATE
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