The probability of containment failure by direct containment heating in Zion

Technical Report · Thu Dec 01 00:00:00 EST 1994

DOI:https://doi.org/10.2172/10106618· OSTI ID:10106618

Pilch, M M ^[1]; Yan, H; Theofanous, T G ^[2]

---

1. Sandia National Labs., Albuquerque, NM (United States)
2. California Univ., Santa Barbara, CA (United States)

This report is the first step in the resolution of the Direct Containment Heating (DCH) issue for the Zion Nuclear Power Plant using the Risk Oriented Accident Analysis Methodology (ROAAM). This report includes the definition of a probabilistic framework that decomposes the DCH problem into three probability density functions that reflect the most uncertain initial conditions (UO{sub 2} mass, zirconium oxidation fraction, and steel mass). Uncertainties in the initial conditions are significant, but our quantification approach is based on establishing reasonable bounds that are not unnecessarily conservative. To this end, we also make use of the ROAAM ideas of enveloping scenarios and ``splintering.`` Two causal relations (CRs) are used in this framework: CR1 is a model that calculates the peak pressure in the containment as a function of the initial conditions, and CR2 is a model that returns the frequency of containment failure as a function of pressure within the containment. Uncertainty in CR1 is accounted for by the use of two independently developed phenomenological models, the Convection Limited Containment Heating (CLCH) model and the Two-Cell Equilibrium (TCE) model, and by probabilistically distributing the key parameter in both, which is the ratio of the melt entrainment time to the system blowdown time constant. The two phenomenological models have been compared with an extensive database including recent integral simulations at two different physical scales. The containment load distributions do not intersect the containment strength (fragility) curve in any significant way, resulting in containment failure probabilities less than 10{sup {minus}3} for all scenarios considered. Sensitivity analyses did not show any areas of large sensitivity.

• Research Organization: Nuclear Regulatory Commission, Washington, DC (United States). Div. of Systems Research; Sandia National Lab. (SNL-NM), Albuquerque, NM (United States)
• Sponsoring Organization: Nuclear Regulatory Commission, Washington, DC (United States)
• DOE Contract Number: AC04-94AL85000
• OSTI ID: 10106618
• Report Number(s): NUREG/CR-6075; SAND-93-1535; ON: TI95005275; BR: GB0103012
• Resource Relation: Other Information: PBD: Dec 1994
• Country of Publication: United States
• Language: English

Related Subjects

22 GENERAL STUDIES OF NUCLEAR REACTORS
21 SPECIFIC NUCLEAR REACTORS AND ASSOCIATED PLANTS
99 GENERAL AND MISCELLANEOUS//MATHEMATICS, COMPUTING, AND INFORMATION SCIENCE
ZION-1 REACTOR
CONTAINMENT
ZION-2 REACTOR
RADIATION HEATING
FAILURES
PROBABILITY
RISK ASSESSMENT
REACTOR ACCIDENTS
DYNAMIC LOADS
DISTRIBUTION FUNCTIONS
PRESSURIZATION
PRESSURE DEPENDENCE
BLOWDOWN
SENSITIVITY ANALYSIS
REACTOR SAFETY
MATHEMATICAL MODELS
220900
210200
990200
POWER REACTORS
NONBREEDING
LIGHT-WATER MODERATED
NONBOILING WATER COOLED
MATHEMATICS AND COMPUTERS