Q7 — PZR PORV Fails Open
000027AK3.03 (3.7)
Given:
• Unit 2 is at 100% Power.
• 2PR1, Pressurizer PORV, fails opens while in Automatic and cannot be closed in Manual from the control console in accordance with S2.OP-AB.PZR-0001, Pressurizer Pressure Malfunction.
In accordance with S2.OP-AB.PZR-0001, which ONE of the following identifies the NEXT required action, and if pressure continues to lower, what subsequent action is taken and why?
• Unit 2 is at 100% Power.
• 2PR1, Pressurizer PORV, fails opens while in Automatic and cannot be closed in Manual from the control console in accordance with S2.OP-AB.PZR-0001, Pressurizer Pressure Malfunction.
In accordance with S2.OP-AB.PZR-0001, which ONE of the following identifies the NEXT required action, and if pressure continues to lower, what subsequent action is taken and why?
A. OPEN the associated control power breaker. IF AT ANY TIME RCS pressure drops to 2000 psig and continues to drop, THEN: TRIP the Reactor. Manually tripping the reactor at 2000 psig and decreasing, to prevent an automatic trip from OTΔT.
B. CLOSE the associated block valve. IF AT ANY TIME RCS pressure drops to 2000 psig and continues to drop, THEN: TRIP the Reactor. Manually tripping the reactor at 2000 psig and decreasing, to prevent an automatic trip from OTΔT.
C. CLOSE the associated block valve. IF AT ANY TIME RCS pressure drops to 1900 psig and continues to drop, THEN: TRIP the Reactor. Manually tripping the reactor at 1900 psig and decreasing, to prevent an automatic trip from Low RCS Pressure.
D. OPEN the associated control power breaker. IF AT ANY TIME RCS pressure drops to 1900 psig and continues to drop, THEN: TRIP the Reactor. Manually tripping the reactor at 1900 psig and decreasing, to prevent an automatic trip from Low RCS Pressure.
▶ Show Answer & Explanation
✓ B. Correct. The next required step per the procedure is to close the associated block valve. The second part of the answer is also correct as the CAS requires tripping the reactor if pressure drops to 2000 psig and continues to drop. The procedure bases states that simulator scenarios were run and based on a failed open PORV, the reactor tripped at 1950 psig on OTΔT. It then states that this is why the 2000 psig value was chosen.
✗ A. Plausible because the procedure does have the operator open the associated control power breaker, but only if the PORV Block Valve fails to close. The second part of the answer is correct as the CAS requires tripping the reactor if pressure drops to 2000 psig and continues to drop. The procedure bases states that simulator scenarios were run and based on a failed open PORV, the reactor tripped at 1950 psig on OTΔT. It then states that this is why the 2000 psig value was chosen.
✗ C. The first part of the answer is correct as the next required step per the procedure is to close the associated block valve. The second part is plausible as 1900 psig is before the low pressure reactor trip setpoint of 1865 psig.
✗ D. Plausible because the procedure does have the operator open the associated control power breaker, but only if the PORV Block Valve fails to close. The second part is plausible as 1900 psig is before the low pressure reactor trip setpoint of 1865 psig.
Ref: S2.OP-AB.PZR-0001(Q), Pressurizer Pressure Malfunction | LO: N/A | Source: New | Cognitive: Fundamental
Connections
- Related systems: Pressurizer & PRT, Pressurizer Level & Press Control, RPS/SSPS
- Related procedures: AB.PZR-0001 — Pressurizer Pressure Control Malfunction
- Related exam: 2020 NRC Written Exam