Accident Mitigation Flashcards
What are the Accident Categories per the UFSAR?
- Condition 1 - Normal Ops transients
- Condition 2 - Moderate frequency
- Condition 3 - Infrequent faults
- Condition 4 - Limiting faults(Design Basis Accidents/DBAs)
How often are Condition 2 events likely to occur?
Condition 2 events are of moderate frequency, expected to occur during a calendar year
How often are Condition 3 events likely to occur?
Condition 3 events are infrequent, may occur during the lifetime of the plant
How often are Condition 4 events likely to occur?
Condition 4 events are limiting events, not expected to occur during the lifetime of the plant
What are the general aspects of accident mitigation and recovery?
- Actuation of engineered safety functions
2. Emergency procedures
What are the limiting faults assumed in the accident analysis?
- Large break loss of coolant
- Major steam line break
- Major feedwater line break
- NC pump shaft break or seizure
- Rod control assembly ejection
- Steam generator tube rupture
What are the indications of a Large Break Loss of Coolant?
NC system depressurizes
greater than or equal to 1 square foot breach
What are the large break LOCA protective functions?
- Reactor trip signals
2. Safety injection
What are the indications of a Major Steam Line Break?
- Steam flow rises
- NC temperature and pressure lower
- Positive reactivity
What are the protective functions associated with a Major Steam Line Break?
- Reactor trip signals
- Safety injection
- Redundant isolation of Feedwater
- Main steam isolation
What are the indications of a Major Feedwater Line Break?
- Insufficient water to the Steam Generators
2. NCS heatup or cooldown
What are the protective functions associated with a Major Feedwater Line Break?
- Reactor trip signals
- Safety injection
- Auxiliary Feedwater actuation
What are the indications associated with a Reactor Coolant Pump Shaft Break or Seizure?
- NC flow rapid reduction
- Reduced heat transfer
- Departure from nucleate boiling
- NC pressure rises
What are the protective functions associated with a Reactor Coolant Pump Shaft Break or Seizure?
- Reactor trip signals
2. Pressurizer safeties
What are the indications of a Rod Control Assembly Ejection accident?
- Positive reactivity insertion
2. Adverse core power distribution
