Analyses of natural circulation during a Surry station blackout using SCDAP/RELAP5
The effects of reactor coolant system natural circulation on the response of the Surry nuclear power plant during a station blackout transient were investigated. A TMLB' sequence (loss of all ac power, immediate loss of auxillary feedwater) was simulated from transient initiation until after fuel rod relocation had begun. Integral analyses of the system thermal-hydraulics and the core damage behavior were performed using the SCDAP/RELAP5 computer code and several different models of the plant. Three scoping calculations were performed in which the complexity of the plant model was progressively increased to determine the overall effects of in-vessel and hot leg natural circulation flows on the plant response. The natural circulation flows extended the transient, slowing the core heatup and delaying core damage by transferring energy from the core to structures in the upper plenum and coolant loops. Increased temperatures in the ex-core structures indicated that they may fail, however. Nine sensitivity calculations were then performed to investigate the effects of modeling uncertainties on the multidimensional natural circulation flows and the system response. Creep rupture failure of the pressurizer surge line was predicted to occur in eight of the calculations, with the hot leg failing in the ninth. The failure time was fairly insensitive to the parameters varied. The failures occurred near the time that fuel rod relocation began, well before failure of the reactor vessel would be expected. A calculation was also performed in which creep rupture failure of the surge line was modeled. The subsequent blowdown led to rapid accumulator injection and quenching of the entire core. 18 refs., 105 figs., 17 tabs.
- Research Organization:
- Nuclear Regulatory Commission, Washington, DC (USA). Office of Nuclear Regulatory Research; EG and G Idaho, Inc., Idaho Falls (USA)
- DOE Contract Number:
- AC07-76ID01570
- OSTI ID:
- 6735604
- Report Number(s):
- NUREG/CR-5214; EGG-2547; ON: TI89001654
- Country of Publication:
- United States
- Language:
- English
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ACCIDENTS
BLACKOUTS
CIRCULATING SYSTEMS
COMPUTER CODES
COOLING SYSTEMS
ENERGY SYSTEMS
ENERGY TRANSFER
ENRICHED URANIUM REACTORS
FLUID MECHANICS
HEAT TRANSFER
HYDRAULICS
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POWER REACTORS
PWR TYPE REACTORS
REACTOR ACCIDENTS
REACTOR COMPONENTS
REACTOR COOLING SYSTEMS
REACTOR SAFETY
REACTORS
S CODES
SAFETY
SURRY-1 REACTOR
SURRY-2 REACTOR
SURRY-3 REACTOR
SURRY-4 REACTOR
THERMAL REACTORS
TRANSIENTS
WATER COOLED REACTORS
WATER MODERATED REACTORS