Nuclear Safety and Emergency Procedures
Domain 4 covers accident recognition, protective actions, and emergency classification. The exam tests whether you can connect indications to a procedure and an emergency action level (EAL), not whether you can memorize a slogan.
Core rules
- Defense in depth uses multiple independent barriers: fuel matrix, cladding, RCS pressure boundary, and containment. Procedures should protect the barrier that is still intact.
- A reactor trip (scram) inserts negative reactivity; ECCS provides makeup and boron when RCS inventory or pressure is lost. Containment isolation and spray limit release.
- A LOCA proceeds from blowdown to refill to long-term cooling. Key symptoms are falling pressurizer level and pressure, rising containment pressure and radiation, and safety injection actuation.
- Emergency classification escalates: Notification of Unusual Event, Alert, Site Area Emergency, General Emergency. Classify on actual or projected dose and plant damage, then notify within the required time.
Worked example
A small RCS leak requires makeup above the normal charging capacity, but containment radiation is stable and ECCS has not actuated. That is an Alert-level condition, not a NOUE. If safety injection later actuates and containment integrity is challenged, escalate to Site Area Emergency. If projected site-boundary dose exceeds the GE EAL, declare General Emergency and recommend protective actions. The action follows the EAL and dose projection, not the loudest alarm.
Traps
Waiting for a confirmed release before classifying. Using one indicator as proof of a LOCA when level, pressure, and radiation disagree. Delaying offsite notification; emergency notification has a 15-minute expectation after declaration. Confusing a reactor trip with an emergency declaration.