Circuit breaker operation and potential failure modes during an earthquake

Conference · Thu Jan 01 04:00:00 EST 1987

OSTI ID:5855565

Lambert, H E; Budnitz, R J

This study addresses the effect of a strong-motion earthquake on circuit breaker operation. It focuses on the loss of offsite power (LOSP) transient caused by a strong-motion earthquake at the Zion Nuclear Power Plant. This paper also describes the operator action necessary to prevent core melt if the above circuit breaker failure modes occur simultaneously on three 4.16 KV buses. Numerous circuit breakers important to plant safety, such as circuit breakers to diesel generators and engineered safety systems (ESS), must open and/or close during this transient while strong motion is occurring. Potential seismically-induced circuit-breaker failures modes were uncovered while the study was conducted. These failure modes include: circuit breaker fails to close; circuit breaker trips inadvertently; circuit breaker fails to reclose after trip. The causes of these failure modes include: Relay chatter causes the circuit breaker to trip; Relay chatter causes anti-pumping relays to seal-in which prevents automatic closure of circuit breakers; Load sequencer failures. The incorporation of these failure modes as well as other instrumentation and control failures into a limited scope seismic probabilistic risk assessment is also discussed in this paper.

• OSTI ID: 5855565
• Report Number(s): CONF-861211-
• Country of Publication: United States
• Language: English

Related Subjects

21 SPECIFIC NUCLEAR REACTORS AND ASSOCIATED PLANTS
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22 GENERAL STUDIES OF NUCLEAR REACTORS
220900* -- Nuclear Reactor Technology-- Reactor Safety
ACCIDENTS
CIRCUIT BREAKERS
EARTHQUAKES
ELECTRICAL EQUIPMENT
ENRICHED URANIUM REACTORS
EQUIPMENT
EQUIPMENT PROTECTION DEVICES
FAILURE MODE ANALYSIS
GROUND MOTION
MELTDOWN
MOTION
OPERATION
POWER REACTORS
PROBABILITY
PWR TYPE REACTORS
REACTOR ACCIDENTS
REACTOR INSTRUMENTATION
REACTORS
RELAYS
SEISMIC EFFECTS
SEISMIC EVENTS
SYSTEM FAILURE ANALYSIS
SYSTEMS ANALYSIS
THERMAL REACTORS
TRANSIENTS
WATER COOLED REACTORS
WATER MODERATED REACTORS
ZION-1 REACTOR
ZION-2 REACTOR