RQ-C-4832 (AOP Review - Shutdown w/ Failed Control Valve, Earthquake, Severe Weather, Loss of 250 VDC)

Question 1

When shutting down with a failed open control valve, why do we reduce power to a point that steam dumps are in service?

Answer 1

• To minimize potential cooldown associated with the failed control valve

Question 2

Why is damage to the road west of the screen house considered criterion for shutting down in the Severe Weather AOP

Answer 2

• Could result in debris in the forebay causing damage to CW and ESW (NRC commitment)

Question 3

During a loss of 250 VDC, what signal will be first to result in a reactor trip

Answer 3

• RCP bus under frequency because DC control power is lost to a train of the relays which are de-energized to actuate

Question 4

What action can be taken during a loss of 250 VDC to avoid a single train SI when a train of 250 VDC is lost

Answer 4

• Transfer the 2 affected CRIDS to CRP 3 prior to tripping the generator (not possible on U2 Train A)