Risk assessment for the intentional depressurization strategy in PWRs

Technical Report · Tue Mar 01 04:00:00 EST 1994

OSTI ID:10140865

Dingman, S E ^[1]

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1. Sandia National Labs., Albuquerque, NM (United States)

An accident management strategy has been proposed in which the reactor coolant system is intentionally depressurized during an accident. The aim is to reduce the containment pressurization that would result from high pressure ejection of molten debris at vessel breach. Probabilistic risk assessment (PRA) methods were used to evaluate this strategy for the Surry nuclear power plant. Sensitivity studies were conducted using event trees that were developed for the NUREG-1150 study. It was found that depressurization (intentional or unintentional) had minimal impact on the containment failure probability at vessel breach for Surry because the containment loads assessed for NUREG-1150 were not a great threat to the containment survivability. An updated evaluation of the impact of intentional depressurization on the probability of having a high pressure melt ejection was then made that reflected analyses that have been performed since NUREG-1150 was completed. The updated evaluation confirmed the sensitivity study conclusions that intentional depressurization has minimal impact on the probability of a high pressure melt ejection. The updated evaluation did show a slight benefit from depressurization because depressurization delayed core melting, which led to a higher probability of recovering emergency core coolant injection, thereby arresting the core damage.

• Research Organization: Nuclear Regulatory Commission, Washington, DC (United States). Div. of Systems Research; Sandia National Labs., Albuquerque, NM (United States)
• Sponsoring Organization: Nuclear Regulatory Commission, Washington, DC (United States)
• DOE Contract Number: AC04-94AL85000
• OSTI ID: 10140865
• Report Number(s): NUREG/CR--6092; SAND--93-1737; ON: TI94009589; BR: GB0103012
• Country of Publication: United States
• Language: English

Related Subjects

21 SPECIFIC NUCLEAR REACTORS AND ASSOCIATED PLANTS
210200
22 GENERAL STUDIES OF NUCLEAR REACTORS
220900
BLACKOUTS
CONTAINMENT SYSTEMS
CORE FLOODING SYSTEMS
DEPRESSURIZATION
FUEL-COOLANT INTERACTIONS
MITIGATION
POWER REACTORS
NONBREEDING
LIGHT-WATER MODERATED
NONBOILING WATER COOLED
PRIMARY COOLANT CIRCUITS
PWR TYPE REACTORS
REACTOR CORE DISRUPTION
REACTOR SAFETY
RISK ASSESSMENT