Markov Model of Accident Progression at Fukushima Daiichi
On March 11, 2011, a magnitude 9.0 earthquake followed by a tsunami caused loss of offsite power and disabled the emergency diesel generators, leading to a prolonged station blackout at the Fukushima Daiichi site. After successful reactor trip for all operating reactors, the inability to remove decay heat over an extended period led to boil-off of the water inventory and fuel uncovery in Units 1-3. A significant amount of metal-water reaction occurred, as evidenced by the quantities of hydrogen generated that led to hydrogen explosions in the auxiliary buildings of the Units 1 & 3, and in the de-fuelled Unit 4. Although it was assumed that extensive fuel damage, including fuel melting, slumping, and relocation was likely to have occurred in the core of the affected reactors, the status of the fuel, vessel, and drywell was uncertain. To understand the possible evolution of the accident conditions at Fukushima Daiichi, a Markov model of the likely state of one of the reactors was constructed and executed under different assumptions regarding system performance and reliability. The Markov approach was selected for several reasons: It is a probabilistic model that provides flexibility in scenario construction and incorporates time dependence of different model states. It also readily allows for sensitivity and uncertainty analyses of different failure and repair rates of cooling systems. While the analysis was motivated by a need to gain insight on the course of events for the damaged units at Fukushima Daiichi, the work reported here provides a more general analytical basis for studying and evaluating severe accident evolution over extended periods of time. This work was performed at the request of the U.S. Department of Energy to explore 'what-if' scenarios in the immediate aftermath of the accidents.
- Research Organization:
- Brookhaven National Laboratory (BNL), Upton, NY (United States)
- Sponsoring Organization:
- AMERICAN NUCLEAR SOCIETY
- DOE Contract Number:
- DE-AC02-98CH10886
- OSTI ID:
- 1049233
- Report Number(s):
- BNL-98130-2012-CP; TRN: US1204421
- Resource Relation:
- Conference: 2012 ANS Winter Meeting & Nuclear Technology Expo; San Diego, CA; 20121111 through 20111115
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
21 SPECIFIC NUCLEAR REACTORS AND ASSOCIATED PLANTS
98 NUCLEAR DISARMAMENT, SAFEGUARDS, AND PHYSICAL PROTECTION
ACCIDENTS
CONSTRUCTION
COOLING SYSTEMS
EARTHQUAKES
EXPLOSIONS
FLEXIBILITY
HYDROGEN
MELTING
MOLTEN METAL-WATER REACTIONS
OUTAGES
PERFORMANCE
RELIABILITY
REPAIR
SENSITIVITY
TIME DEPENDENCE
TSUNAMIS
EMERGENCY PLANS
Fukushima Daiichi
earthquake
Markov Model
reactor vessel