Reactor Power Cutback System (RPCS)

Question 1

If the TEST/RESET button is depressed (backlit) and a RPCB occurs, what will happen?

Answer 1

Nothing. TEST/RESET inhibits all RPCB functionality.

Question 2

What happens if a selected subgroup of RPCS is on the Hold Bus on a RPCB?

Answer 2

That subgroup will not fall into the core. CPCs will then trip the reactor for CEAs being out of sequence because it expected those CEAs to drop.

Question 3

What does the AUTO ACTUATE OOS button do in the RPCB System?

Answer 3

Defeats automatic only RPCB operation.

Question 4

What specific parameter on a Main Feed Pump will initiate a RPCB when you lose it?

Answer 4

Main Feed Pump oil pressure <75 psig from both of 2 pressure switches (2/2 logic)

Question 5

What happens on a Turbine Setback?

Answer 5

MT Control Valves go to 60% at 480%/minute

Question 6

What happens to the RPCB System if NNN-D11 is lost?

Answer 6

RPCB is totally disabled (no CEAs or turbine actions)

Question 7

What happens to the RPCB System if NNN-D12 is lost?

Answer 7

Turbine Runback is disabled.
- On a cutback, the Main Turbine will only setback to 60% which will result in a Reactor Trip due to Secondary Power > Primary Power

Question 8

What is Turbine Increase Inhibit and when does it occur?

Answer 8

• Prevents the INCREASE LOAD button from raising Main Turbine Load until the RPCB is manually reset.
• Occurs on any RPCB

Question 9

What two signals are sent to CEDMCS to drop rods for a Cutback? How long?

Answer 9

ARM and DROP
10 seconds

Question 10

How fast is a Main Turbine Runback?

Answer 10

Lowers load reference 130%/min due to Load Set Motor limitations.

Question 11

Will a locked up microprocessor in the RPCS cause an inadvertent cutback?

Answer 11

No

• Microprocessor:
  o Drives indication lights on control panel. Monitoring and alarm functions.
  o If locked up / faulted, lights may be inaccurate and not respond to a lamp test.
  o Does NOT cause or prevent a cutback (this is based on Test/Reset and Auto Actuate OOS buttons)
  o Affects CEA selection. Could affect proper CEA drop during a cutback.

Question 12

What will be the status of RPCS if an Operator pushes the Test/Reset button twice?

Answer 12

RPCS will be in service, but no CEA’s will be selected.

Question 13

How does RPCS detect a Large Load Reject event has occurred?

Answer 13

• Large Load Reject (LLR)
  o Signal sent from SBCS. SBCS sees load reject by comparing:
  -SG 1 Steam Flow ↓ with Pressuirzer Pressure↑ (X1/Y1) - RPCB Demand #1 (PT-100X)
  -TLI↓ with PPZR↑ (X2/Y2) - RPCB Demand #2 (PT-100Y)
  o Both demand signals are required for a RPCB