Venting of noncondensible gas from the upper head of B and W reactor vessel using hot leg U-bend vent valves
This report describes a RELAP5/MOD2 thermal-hydraulic analysis of noncondensible gas removal from the upper head of a B and W reactor vessel. Hot leg U-bend vent valves were modeled as the only venting mechanism available. The analysis will assist the US Nuclear Regulatory Commission (NRC) in determining whether two B and W plants should receive permanent exemptions from a reactor vessel upper heat vent requirement. Approximately 20% of the original noncondensible inventory was removed in 2400 seconds. The removal rate was approximately one percent per hundred seconds after the initial removal period. The analysis indicates that 59% of the original inventory could be removed in approximately 6900 seconds. The method of removal appears to produce brief periods of natural circulation interruption (100 seconds) during which the removal rates are most significant. Core heatup was insignificant during the periods of flow stagnation, and no cladding surface temperature excursions were predicted.
- Research Organization:
- EG and G Idaho, Inc., Idaho Falls (USA)
- DOE Contract Number:
- AC07-76ID01570
- OSTI ID:
- 6471946
- Report Number(s):
- EGG-RST-7006; ON: TI86004138
- Country of Publication:
- United States
- Language:
- English
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