Interpretation of risk significance of passive component aging using probabilistic structural analysis

Conference · Fri Jan 01 04:00:00 EST 1993

OSTI ID:6503121

Phillips, J H ^[1]; Atwood, C L ^[2]

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1. TENERA, L.P., Idaho Falls, ID (United States)
2. EG and G Idaho, Inc., Idaho Falls, ID (United States)

The probabilistic risk assessments (PRAs) being developed at most nuclear power plants to calculate the risk of core damage generally focus on the possible failure of active components. Except as initiating events, the possible failure of passive components is given little consideration. The NRC is sponsoring a project at INEL to investigate the risk significance of passive components as they age. For this project, we developed a technique to calculate the failure probability of passive components over time, and demonstrated the technique by applying it to a weld in the auxiliary feedwater (AFW) system. A decreasing yearly rupture rate for this weld was calculated instead of the increasing rupture rate trend one might expect. We attribute this result to infant mortality; that is, most of those initial flaws that will eventually lead to rupture will do so early in life. This means that although each weld in a population may be wearing out, the population as a whole can exhibit a decreasing rupture rate. This observation has implications for passive components in commercial nuclear plants and other facilities where aging is a concern. For the population of passive components that exhibit a decreasing failure rate, risk increase is not a concern. The next step of the work is to identify the attributes that contribute to this decreasing rate, and to determine any attributes that would contribute to an increasing failure rate and thus to an increased risk.

• Research Organization: EG and G Idaho, Inc., Idaho Falls, ID (United States)
• Sponsoring Organization: NRC; Nuclear Regulatory Commission, Washington, DC (United States)
• DOE Contract Number: AC07-76ID01570
• OSTI ID: 6503121
• Report Number(s): EGG-M-93123; CONF-930702--22; ON: DE93013664
• Country of Publication: United States
• Language: English

Related Subjects

22 GENERAL STUDIES OF NUCLEAR REACTORS
220200 -- Nuclear Reactor Technology-- Components & Accessories
220900* -- Nuclear Reactor Technology-- Reactor Safety
AUXILIARY SYSTEMS
COMPUTER CODES
JOINTS
NUCLEAR FACILITIES
NUCLEAR POWER PLANTS
P CODES
PIPES
POWER PLANTS
PROBABILITY
REACTOR COMPONENTS
RISK ASSESSMENT
STRESSES
THERMAL POWER PLANTS
TRANSIENTS
WELDED JOINTS