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Abnormals > AB.PZR-0001 — Pressurizer Pressure Control Malfunction

AB.PZR-0001 — Pressurizer Pressure Control Malfunction

⚠️ DRAFT

AB.PZR-0001 — Pressurizer Pressure Control Malfunction

Purpose

Provides operator actions for responding to malfunctions in the pressurizer pressure control system, including instrument failures and their effects on reactor protection.

Key Actions / Information

Exam — 2023 Q5
When a PZR pressure channel fails high, actual RCS pressure lowers. This causes the OT Delta-T setpoint to lower. The OT Delta-T trip actuates first (before the low PZR pressure trip) because the OT Delta-T setpoint is moving toward the actual Delta-T value.
Exam — 2022 Q9
With PZR spray valve failed open and heaters energized but unable to maintain pressure: manual reactor trip directed at RCS pressure 2000 psig and lowering. Basis: prevent challenging automatic reactor trip on OTΔT — not the low PZR pressure trip at 1865 psig rate-compensated.
Scenario — 2022 #4
2PR2 PZR PORV seat leakage. Entry cue: OHA E-28 PZR HTR ON PRESS LO with rising PORV tailpipe temperature. Diagnostic method: close both block valves (2PR6, 2PR7), stabilize RCS pressure, then open each block valve individually — the one causing tailpipe temp to rise identifies the leaking PORV (2PR2 via 2PR7). CRS enters TS 3.4.5 action a (1 hour to close PORV block valve with power maintained) and evaluates TS 3.2.5.b if RCS pressure below 2200 psia [2185 psig].
Exam — 2020 Q7
PORV fails open, cannot close in manual: next required action is CLOSE the associated block valve. Opening the control power breaker is only done if the block valve FAILS to close. CAS: if RCS pressure drops to 2000 psig and continues to drop, TRIP the reactor. Basis: simulator scenarios showed reactor tripped at 1950 psig on OTΔT, so 2000 psig value was chosen to prevent automatic trip. 1900 psig distractor: low pressure reactor trip setpoint is 1865 psig (rate-compensated) — 1900 psig is plausible but not the procedure value.
JPM — 2020 Sim-a
PZR pressure channel 1 fails high → MPC drives both spray valves fully open. Operator takes MPC to manual and lowers demand. Alternate path: 2PS1 fails to close when MPC demand zeroed. Procedure path: Step 3.3 YES (controlling channel failed) → 3.5 MPC to MANUAL → 3.6 adjust per Attachment 2 → 3.17 spray valve(s) failed YES → 3.18 place 2PS1 in MANUAL → 3.19 close 2PS1. CAS: if RCS pressure drops to 2000 psig and continues to drop → trip reactor and stop 21 and 23 RCPs.
Scenario — 2019 #1
PZR Pressure Channel I fails high at 4% power (Event 2). RO places MPC in Manual, restores pressure by selecting Channel III, returns MPC to Auto. CRS enters TSAS for 3.3.3.1 Action 6, 3.3.2.1 Action b.19, 3.4.5 Action b (1 hour), and 3.2.5.b (2 hour if RCS < 2200 psia). RO places 2PR1 in Manual and closes 2PR6 Block Valve. WCC removes control power to 2PR6.
Scenario — 2019 #4
2PR2 PORV leaks at 88% power (Event 1). Crew recognizes from elevated PORV tailpipe temperatures. Isolates by opening both block valves sequentially: 2PR6 tailpipe temps stable, 2PR7 tailpipe temps rising → close 2PR7 to isolate 2PR2. CRS enters TSAS 3.4.5 Action a (1 hour LCO).
Scenario — 2018 #1
PZR Pressure Channel I fails high during startup at ~6% power. Both spray valves fully open, PZR heaters de-energize. RO places MPC in manual, lowers demand to close spray valves. Selects Channel III for control, returns MPC to Auto. Closes 2PR6, places 2PR1 in Manual. WCC removes control power from 2PR6. PO removes failed channel IAW S2.OP-SO.RPS-0003. Tech Specs: 3.3.1.1 Action 6, 3.3.2.1.b Action 19, 3.4.5 Action b (1 hr LCO), 3.2.5 DNB (2 hr LCO).

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