SALEM
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Systems > RPS/SSPS

RPS/SSPS

⚠️ DRAFT

RPS/SSPS

Function

Instrumentation and Control Systems provide the reactor operator with information and control capability to operate the station safely and efficiently. Safety-related logic circuitry and actuators execute equipment actions without operator action when safety functions are involved. Salem’s Protection and ESF Actuation Systems are functionally identical to those in the D.C. Cook Plant. (UFSAR 7.1)

Reactor Trip Functions

#Trip FunctionTrip SetpointCoincidenceInterlocksSource
1ManualN/A1/2NoneUFSAR T7.2-1
2High Neutron Flux (Power Range — High)≤109% RTP2/4NoneTS T2.2-1
2High Neutron Flux (Power Range — Low)≤25% RTP2/4Interlocked with P-10TS T2.2-1
3Overtemperature Delta-TVariable (f(Tavg, P, Delta-I))2/4NoneTS T2.2-1
4Overpower Delta-TVariable (f(Tavg))2/4NoneTS T2.2-1
5Low Pressurizer Pressure≥1865 psig2/4Interlocked with P-7TS T2.2-1
6High Pressurizer Pressure≤2385 psig2/4NoneTS T2.2-1
7High Pressurizer Water Level≤92% span2/3Interlocked with P-7TS T2.2-1
8Low Reactor Coolant Flow≥90% design flow/loop2/3 per loopInterlocked with P-7 and P-8TS T2.2-1
9ARCP Undervoltage≥2900 V each bus1/2 taken twiceInterlocked with P-7TS T2.2-1
9BRCP Underfrequency≥56.5 Hz each bus1/2 taken twiceInterlocked with P-7TS T2.2-1
9CRCP Breaker OpenN/A—Interlocked with P-7UFSAR T7.2-1
10Safety Injection SignalSee SI actuationSee SI actuation—UFSAR T7.2-1
11Turbine-Generator Trip — Auto Stop Oil≥45 psig2/3Interlocked with P-9TS T2.2-1
11Turbine-Generator Trip — Stop Valve Closure≤15% off full open—Interlocked with P-9TS T2.2-1
14Source Range Neutron Flux≤10⁵ cps1/2Manual block by P-6, interlocked with P-10TS T2.2-1
15High Positive Flux Rate≤5% RTP (τ ≥ 2 sec)2/4NoneTS T2.2-1
13SG Water Level — Low-Low≥14.0% NR span2/3 per SGNoneTS T2.2-1
5Intermediate Range Neutron Flux≤25% RTP1/2Interlocked with P-6 and P-10TS T2.2-1

Note: Negative Flux Rate Trip has been removed per NRC License Amendment 278-261. (UFSAR T7.2-1)

Exam — 2018 Q10
PZR Pressure LOW Reactor Trip: normal coincidence is 2/4 (PT-455, PT-456, PT-457, PT-474). With 2PT-456 failed low, the failed channel's bistable is already satisfied (reads below trip setpoint). The effective coincidence for the remaining functional channels is 1 out of 3. PT-1648 is for RSP indication ONLY and does NOT feed the PZR Pressure LOW Reactor Trip coincidence logic. Trap: candidates may think PT-1648 is part of the trip logic (making it 2/5 or 1/4), or may think the failed channel is bypassed (giving 2/3 instead of 1/3). A failed-low channel SATISFIES the trip condition — it is not removed from the logic.
Exam — 2019 Q30
PR High Neutron Flux trip with one channel tripped (bistable tripped per S2.OP-SO.RPS-0001): the tripped bistable remains in the coincidence logic as a permanently satisfied input. Normal coincidence is 2/4. With one channel tripped, coincidence becomes 1 out of 3 (the tripped bistable counts as one of the two required trips). Trap: tripping the bistable does NOT remove the channel from the logic (which would give 2/3). It satisfies one leg permanently, making the effective coincidence 1/3 for the remaining functional channels.
Exam — 2020 Q1
Turbine Stop Valve status lights on 2RP4: LIT solid = both SSPS trains see the valve at ≤ 85% open. FLASHING = Trains A and B disagree on valve position. OHA F-36 (TURB TRIP & P-9) confirms either 4/4 Turbine Stop Valves ≤ 85% open OR 2/3 Auto Stop Oil Pressures ≤ 50 psig. Trap: 45 psig is the Tech Spec value for auto stop oil, not the actual setpoint (≤ 50 psig). A flashing light does NOT mean a valve is mid-stroke — it means train disagreement.
Exam — 2023 Q1
Low RC Flow trip: 2/3 coincidence per loop. Trip setpoint ≤90% of design loop flow. Between P-7 (10%) and P-8 (36%): loss of flow in a single loop does NOT cause an automatic trip — P-8 must be exceeded for single-loop low flow trip. However, per S2.OP-AR.ZZ-0004, degraded RCP flow requires manual trip and RCP stop because Tech Specs do not allow 3-loop operation in Mode 1.
Exam — 2023 Q35
PZR Pressure High trip (2/4 channels exceeding 2385 psig) has NO permissive interlock — it is active at ALL power levels regardless of reactor power. At 7% power (below P-7), low PZR pressure, low RCS flow, RCP undervoltage/underfrequency, and high PZR level trips are all blocked by P-7, but PZR Pressure High is not blocked and will directly cause a reactor trip.
Exam — 2023 Q36
RCP underfrequency reactor trip logic: 1/2 on (H or E bus) AND 1/2 on (F or G bus), enabled above P-7 (10% power). Both bus groups must have underfrequency to satisfy coincidence. Individual 4KV RCP breakers trip on undervoltage, NOT underfrequency. If only H and E buses experience low frequency but F and G are normal, the reactor trip logic is NOT satisfied and no RCPs trip (voltage adequate).
Exam — 2018 Q11
RCP Undervoltage Reactor Trip: 4KV Group Busses H and G monitored. Trip signal generated when both are less than a maximum of 70% of normal bus voltage. Coincidence: 1/2 taken twice, interlocked with P-7 (above 10% power). Trap: 90% is the setpoint for the RCP Low Flow Reactor Trip, not undervoltage. The monitored busses are H and G, not H and E.

Key Permissive Interlocks

DesignationSetpointDerivationFunctionSource
P-4N/AReactor tripActuates turbine trip; closes main FW valves on low TavgUFSAR T7.2-2
P-61E-6% RTP (IR)1/2 intermediate range above setpointAllows manual block of source range tripUFSAR T7.2-2
P-710% RTP3/4 power range below P-10 AND 2/2 turbine pressure below P-13Blocks trips on: low flow (>1 loop), UV, UF, low PZR pressure, high PZR levelUFSAR T7.2-2
P-836% RTP3/4 power range below setpointBlocks trip on low flow in a single loopUFSAR T7.2-2
P-950% RTP2/4 power range above setpointPrevents/defeats block of turbine trip reactor tripUFSAR T7.2-2
P-1010% RTP2/4 power range above setpointAllows block of power range low setpoint trip; blocks source range tripUFSAR T7.2-2
P-11≥1925 psig2/3 PZR pressure channelsAllows manual block of SI on low PZR pressureTS T3.3-3
P-12543°F Tavg2/4 Tavg channels (increasing: 3/4)Actuates SI/steamline isolation on high steam flow; blocks steam dumpTS T3.3-3
P-13600 psig2/2 turbine steamline inlet pressure below setpointInput to P-7UFSAR T7.2-2
P-14≤67% NR span2/3 Hi-Hi SG level above setpoint (any SG)Trips all FW pumps, isolates feedwater, trips turbineTS T3.3-4

Rod Control Interlocks (Rod Stops)

DesignationDerivationFunctionSource
C-11/2 intermediate range above setpointBlocks auto and manual rod withdrawalUFSAR T7.2-2
C-21/4 power range above setpointBlocks auto and manual rod withdrawalUFSAR T7.2-2
C-32/4 OT Delta-T above setpointBlocks rod withdrawal; actuates turbine runbackUFSAR T7.2-2
C-42/4 OP Delta-T above setpointBlocks rod withdrawal; starts turbine runbackUFSAR T7.2-2
C-51/1 turbine pressure below setpointBlocks automatic rod withdrawalUFSAR T7.2-2

Note: Automatic rod withdrawal is disabled at Salem. (UFSAR T7.2-2)

ESF Actuation Signals

SignalDesignationActuationSetpointsActionsSource
Safety Injection”S”Low PZR pressure (2/3), OR Hi containment pressure (2/3), OR Hi steamline DP (2/3), OR Hi steam flow (2/4) AND (Lo-Lo Tavg 2/4 OR Lo steam pressure 2/4), OR Manual (1/2)PZR Lo: ≤1765 psig; CNMT Hi: ≥4.0 psig; Steam DP: ≥100 psi; Tavg Lo-Lo: ≤543°F; Steam Press Lo: ≤600 psigSI, reactor trip, diesel start, Phase A isolationTS T3.3-4
Phase A Containment Isolation”T”Safety Injection signalN/A (auto on SI)Isolates all non-essential process linesUFSAR T7.2-1
Containment Spray / Phase B Isolation”P”2/4 Hi-Hi containment pressure, OR 2/2 manualCNMT Hi-Hi: ≤15.0 psigContainment spray, steamline isolation, remaining isolation valvesTS T3.3-4
Main Steamline Isolation—Hi steam flow (2/4) AND (Lo-Lo Tavg 2/4 OR Lo steam pressure 2/4), OR Hi-Hi containment pressure (2/4), OR manual (1/1 per line)Same as SI steam flow setpoints; CNMT Hi-Hi: ≤15.0 psigCloses MSIVsTS T3.3-4
Exam — 2023 Q21
Containment spray / Phase B actuation logic is normally 2/4 Hi-Hi containment pressure. When one channel is properly removed from service (bypassed), the logic reduces to 2/3. The Hi-Hi containment pressure setpoint is 15 psig. CS pump discharge valves (CS2s) open on the CS actuation signal specifically, not the Phase B signal.
Exam — 2019 Q11
Containment Pressure channel removal from service changes coincidence logic differently for SI/Reactor Trip vs Containment Spray. When Channel II is removed: SI/Reactor Trip (on Hi CTMT Pressure) goes from 2/3 to 1/2; Containment Spray (on Hi-Hi CTMT Pressure) goes from 2/4 to 2/3. SI and Reactor Trip bistables are de-energize to actuate — loss of power to Channel III satisfies the 1/2 logic and actuates SI + Reactor Trip. CS bistables are energize to actuate — loss of power to Channel III does NOT satisfy the 2/3 logic. Key distinction: SI/Rx Trip uses Channels II, III, IV only (Hi CTMT Pressure) while CS uses all four channels I-IV (Hi-Hi CTMT Pressure). Removing Channel II has different effects on each system's coincidence.
Exam — 2020 Q88
Containment Spray Hi-Hi Containment Pressure bistables are energized to actuate (opposite of most ESF bistables which are de-energized to trip). Loss of a Vital Instrument Bus leaves the associated bistable de-energized → logic goes from 2/4 to 2/3 (de-energized channel cannot actuate). Per TS 3.3.2.1, the inoperable Hi-Hi Containment Pressure channel is placed in BYPASS (not tripped) to reduce the possibility of spurious Containment Spray actuation. Trap: most ESF bistables are de-energized to trip and TS requires placing inoperable channels in TRIPPED condition. Containment Spray bistables are the exception — energized to actuate, so inoperable channels are BYPASSED.
Exam — 2023 Q53
Containment Vacuum Relief dampers (VC5 and VC6) automatically close on Safety Injection (SI) signal or Containment Vent Isolation (CVI) signal — NOT on Phase A alone. CVI is also generated by containment atmosphere radiation monitors (2R11A, 2R12A, 2R12B — any one in alarm). Phase A does not actuate a CVI signal.
Exam — 2020 Q59
Manually initiating Phase B and Spray Actuation from the Control Room Console also generates a Containment Ventilation Isolation (CVI) signal. CVI closes ALL purge and pressure/vacuum relief valves: VC1, VC4, VC5, and VC6 (per Safeguards Action Signals Logic Diagram Sheet 8, drawing 221057). Phase A does NOT generate CVI. CVI closes all four valves — not just VC1/VC4 (purge isolation).
Exam — 2020 Q39
SI signal blockability during cooldown (IOP-6): Low PZR Pressure SI and High Steam Flow SI can be blocked when P-11 is active (< 1915 psig). However, Containment High Pressure SI (4 psig, 2/3 channels) CANNOT be blocked — it remains active in all modes. During a Mode 3 cooldown with SI blocks in place, multiple SG depressurizations inside containment will cause Containment High Pressure SI actuation even though Low PZR Pressure SI is blocked. Low PZR Pressure SI logic is 2/3 channels (not 2/4) — the 2/4 logic is for the Low PZR Pressure reactor trip, not the SI signal.

Auxiliary Feedwater Actuation

PumpActuation SignalsSetpointsSource
Turbine-Driven2/3 Lo-Lo level in any 2 SGs; OR RCP bus undervoltage (1/2 twice); OR manualSG Lo-Lo: ≥14.0% NR; RCP UV: ≥70% bus voltageTS T3.3-4
Motor-Driven2/3 Lo-Lo level in any SG; OR trip of both main FW pumps; OR safeguards sequence; OR blackout sequence; OR manualSG Lo-Lo: ≥14.0% NRTS T3.3-4

Main Feedwater Isolation

Actuated by: SI signal, OR 2/3 Hi-Hi SG level (≤67% NR span), OR low auctioneered Tavg AND reactor trip. Closes main FW control valves (fast closure), bypass valves, and inlet stop valves. (UFSAR T7.2-1, TS T3.3-4)

Overtemperature Delta-T Trip

Protects the core against DNB. Continuously calculated setpoint per loop (2/4 coincidence):

Delta-T setpoint = K1 - K2*(Tavg) + K3*(P) - f(delta-phi)

Where K1 = setpoint bias, K2 = temperature effect on DNB, K3 = pressure effect on DNB, f(delta-phi) = axial flux difference penalty. Changes in f(delta-phi) can only decrease the setpoint. (UFSAR 7.2.2.5)

Exam — 2023 Q5
OT Delta-T has a PRESSURE input (+K3*P). As RCS pressure LOWERS, the OT Delta-T setpoint LOWERS (becomes more restrictive). OP Delta-T does NOT have a pressure input. If PZR pressure controlling channel fails HIGH, actual pressure drops → OT Delta-T setpoint lowers → OT Delta-T trips reactor before low PZR pressure trip.
Exam — 2020 Q37
OT Delta-T operational inputs: Tavg, Pressurizer Pressure, and Delta-I (axial flux difference). OT Delta-T is a DNB protection trip. OP Delta-T does NOT use pressure or delta flux (f2(delta-I) = 0) — only Tavg and rate of change of Tavg. Candidates commonly confuse OP Delta-T inputs with OT Delta-T inputs.

Overpower Delta-T Trip

Protects against excessive power (fuel rod rating). Continuously calculated per loop (2/4 coincidence):

Delta-T setpoint = K4 - K5*(rate of change of Tavg) + K6*(Tavg - Tavg-setpoint) - f(delta-phi)

OP Delta-T does NOT have a pressure input. (UFSAR 7.2.2.5)

AMSAC (ATWS Mitigation System Actuation Circuitry)

Diverse from the Reactor Protection System. Provides backup trip of turbine and actuation of AFW in the event the RPS fails to trip the reactor. Armed by P-20 (turbine steamline inlet pressure above setpoint). Actuates on low SG water level. Not safety-related but important for ATWS mitigation per 10CFR50.62. (UFSAR 7.8)

Exam — 2023 Q80
ATWS turbine trip verification per EOP-FRSM-1 Step 6: confirm turbine trip by checking that ALL turbine stop valve closed bi-stables are LIT on 2RP4. 2/3 Auto Stop Oil low pressure bi-stables LIT is a demand for a turbine trip, not confirmation that the turbine actually tripped. If turbine trip is not confirmed, dispatch operator to locally trip the turbine at the front standard.
Exam -- 2023 Q92
PZR pressure channel failure and NRC reportability: with Channel I already in tripped condition and Channel III failing LOW, a reactor trip and SI actuate on low PZR pressure (2/4 coincidence met with 2 channels tripped). Since actual RCS pressure was NOT low, the SI is NOT valid and NOT reportable. However, the RPS actuation IS valid and reportable under RAL 11.3.2 as a 4-hour report. Trap: RAL 11.3.1 (also 4-hour) is for valid ECCS actuations -- the SI here is NOT valid. RAL 11.3.3 (8-hour) does not apply because the event is already captured under RAL 11.3.2.

POPS (Pressurizer Overpressure Protection System)

Provides low-temperature overpressure protection by enabling PORVs to open at a reduced setpoint when RCS temperature is low. Prevents exceeding Appendix G pressure-temperature limits during heatup, cooldown, and cold shutdown. (UFSAR 7.6.3)

Exam — 2022 Q91
TS 3.4.10.3 action "e": LCO 3.0.4.b is NOT applicable when entering MODE 4 from MODE 5 with an inoperable POPS/LTOP channel. Mode change from Mode 5 to Mode 4 may NOT be performed until the channel is restored to OPERABLE status. Risk assessment per 3.0.4.b is explicitly prohibited by the TS bases due to increased risk associated with entering Mode 4 with inoperable LTOP.
Exam — 2022 Q85
CFST priority for Thermal Shock (EOP-FRTS-1): a RED path exists when RCS T-Cold cooldown rate exceeds 100F in the last 60 minutes AND the RCS pressure/temperature point is NOT to the right of Limit A in Figure 4A. With all T-Colds <230F and RCS pressure at 1100 psig (well into the unacceptable region), EOP-FRTS-1 is the highest priority FRP. RED Thermal Shock takes priority over PURPLE Shutdown Margin (+0.1 DPM SUR) and YELLOW Heat Sink (low SG levels).
Exam — 2023 Q34
Master Pressure Controller (MPC) controls PZR spray valves and backup heaters. If MPC fails low (0% output): spray valves close, both backup heater groups energize, and RCS pressure rises. PORVs are interlocked directly from PZR pressure channels, NOT from MPC. PORVs open independently at 2335 psig regardless of MPC status. MPC failure does not prevent PORV actuation.

Reactor Trip Breakers

Two reactor trip breakers (52/RTA and 52/RTB) in series, each with a bypass breaker (52/BYA and 52/BYB). Trip signal deenergizes undervoltage coils and actuates shunt trip. If a bypass breaker is closed for testing and the other train’s bypass breaker is also closed, both trip breakers and bypass breakers are automatically tripped by the General Warning Alarm. (UFSAR 7.2.2)

Exam — 2020 Q38
"LOSS OF TRIPPING CAPABILITY" alarm on an RTB indicates loss of power to the shunt trip coil. The shunt coil is energized to trip — without power it cannot initiate a trip. The UV (undervoltage) coil is de-energized to trip — it remains functional. The 2CC2 RTB pushbuttons ONLY energize the shunt trip coil — with shunt coil power lost, the 2CC2 pushbuttons cannot trip the RTB. Only reactor trip signals that de-energize the UV trip coil will open the affected RTB.
Exam — 2022 Q38
When only RTB B opens (RTB A fails closed): the 20-ET (Emergency Trip Fluid Solenoid) trips the turbine by dumping EH fluid directly to the reservoir, closing all turbine steam valves. 20-AST and 20-2AST energize from RTB A — with RTB A failed closed, neither energizes. 2EH61 (Interface Valve) opens only when 20-AST or 20-2AST energizes. The auto turbine trip via SSPS comes from the reactor trip signal through the 20-ET solenoid on RTB B opening — NOT through the generator lockout relay or 2EH61.
Exam — 2022 Q39
Containment pressure channel logic: SI uses channels II, III, IV only (2/3 coincidence). CS/Phase B uses channels I-IV (2/4 coincidence). With Channel I properly removed from service (tripped): CS/Phase B logic reduces to 2/3; SI logic remains 2/3 (Channel I not an input). If Channel IV then fails high: SI = 1/3 tripped (NOT met). CS/Phase B = 1/3 tripped (NOT met). Neither SI nor Phase B actuates. Channel I removed from service removes its input from both SI and CS/Phase B — it does NOT count as a "tripped" channel for actuation purposes.
Exam — 2022 Q40
SSPS auctioneered power supply design: 48V and 15V DC power supplies are redundant within each SSPS train. Loss of one 48 VDC power supply to Train B has no adverse effect on SSPS Train B function — all components will still automatically actuate when required. Only loss of BOTH 48V power supplies (or loss of 115 VAC to the slave relays) would prevent SSPS train actuation. A single power supply loss only eliminates redundancy.
Exam — 2022 Q1
SSPS Train A de-energizes UV coils for RTB 'A' and BYB 'B', energizes shunt coil for RTB 'A' only. SSPS Train B de-energizes UV coils for RTB 'B' and BYB 'A', energizes shunt coil for RTB 'B' only. Shunt coils also energize from: Manual SI, Pistol Grip switches, or RTB PB bezels on CC2 — these are separate from SSPS train outputs.
Exam — 2022 Q3
Phase A (ØA) indication on 2CC1 SAFEGUARDS ACTUATION Bezels: Red light LIT = train actuated. Red light OUT = train failed to actuate. On 2RP4, status lights LIT = component repositioned to safeguard position. Per EOP-TRIP-1 step 12, if any safeguards valve not in required position, place valves in safeguards position manually.
Exam — 2023 Q65
SSPS Train Disagreement: "SI & FW ISOL" Red lamp on 2RP4 FLASHES when one Train of SI has actuated and the other has not (train disagreement). Lamp is LIT solid when both trains actuate. The "SI RESET" Green bezel light on the failed train's Safeguards panel will be LIT (indicating that train did not actuate).
Exam — 2023 Q56
Rod Position Indication: Only Group 1 Demand Steps input into the Plant Computer. Per S2.OP-DL.ZZ-0003, either the Group Demand Counter or Plant Computer will satisfy the TS 3.1.3.2.1 surveillance for Group 1 only.
JPM — 2018 IP-j
Control Room Evacuation (Unit 1) — locally open reactor trip breakers and control charging flow per S1.OP-AB.CR-0001 Attachment 5: proceed to Rod Drive MG Set Control Panel (460V Vital Bus Room, El 84) and open Reactor Trip Breaker A and Reactor Trip Breaker B (Bypass Trip Breakers typically racked out/N/A). Trip #13 Charging Pump breaker (1AX1AX7X) at 1A 460V MCC. Open 1CV175 Rapid Borate Stop Valve breaker (1CY2AX41) at 1C West 230V Control Center. At Panel 216-1 (Charging Valve Alley): record charging flow from 1FI-128A, place E/P Bypass to Manual, and control 1CV55 (fail-open, air-to-close) — lower air pressure (counterclockwise) to OPEN valve and RAISE flow.
JPM — 2022 IP-j
Control Room Evacuation (Unit 1) — locally open reactor trip breakers per S1.OP-AB.CR-0001 Attachment 5: proceed to Rod Drive MG Set Control Panel (460V Vital Bus Room - El 84 ft.) and open all four breakers — Reactor Trip Breaker A, Reactor Trip Breaker B, Reactor Trip Bypass Breaker A, Reactor Trip Bypass Breaker B. Also trip #13 Charging Pump breaker (1AX1AX7X) and open 1CV175 Rapid Borate Stop Valve breaker (1CY2AX4I).

Tech Spec LCOs

  • TS 3/4.3 — Instrumentation — Trip setpoints, response times, channel operability
  • TS 3/4.3 — Instrumentation|TS 3/4.3.1 — Reactor Trip System Instrumentation
  • TS 3/4.3 — Instrumentation|TS 3/4.3.2 — ESF Actuation System Instrumentation

Connections

  • Related systems: Excore NIs, Control Rod Drive, Radiation Monitoring, Incores, AMSAC
  • Related concepts: Rx Vessel & Internals
  • Related procedures: AB.NIS-0001 — Nuclear Instrumentation System Malfunction, AB.ROD-0003 — Continuous Rod Motion, S1.OP-SO.RCS-0001 — Rod Control System Operation, AB.CR-0001 — Control Room Evacuation
  • Related JPMs: 2018 JPM IP-j, 2023 JPM Sim-a, 2023 JPM Sim-g, 2023 JPM IP-j, 2022 JPM IP-j
  • Related scenarios: 2018 Scenario 1, 2018 Scenario 2
  • Related exams: 2018 NRC Written Exam, 2018 NRC Operating Exam, 2019 NRC Written Exam, 2023 NRC Written Exam, 2023 NRC Operating Exam, 2022 NRC Written Exam, 2022 NRC Operating Exam, 2020 NRC Written Exam
    • 2018 Q1 — RCP shaft shear at 25% power: below P-8, single-loop low flow trip blocked
    • 2018 Q10 — PZR Pressure Channel fails low: 2/4 becomes 1/3 coincidence; PT-1648 is RSP only
    • 2018 Q49 — TRIP-1 immediate actions when RTBs fail: Trip Switches → Bezels → MG set breakers (E 6D, G 6D) → Turbine Trip
    • 2019 Q30 — PR NI tripped bistable: 2/4 becomes 1/3 coincidence (not 2/3)
    • 2020 Q1 — 2RP4 turbine stop valve status lights flashing = SSPS train disagreement
    • 2020 Q7 — PORV failed open: manual trip at 2000 psig to prevent auto trip on OT Delta-T (trips at ~1950 psig) / low PZR pressure trip at 1865 psig
    • 2020 Q37 — OT Delta-T inputs: Tavg, PZR Pressure, Delta-I / OP Delta-T has no pressure or delta flux input
    • 2020 Q38 — Loss of Tripping Capability alarm = loss of shunt coil power / UV coil still functional
    • 2020 Q39 — Containment High Pressure SI (2/3, 4 psig) cannot be blocked / Low PZR Pressure SI blocked via P-11
    • 2020 Q59 — Phase B/Spray Actuation generates CVI (VC1, 4, 5, 6); Phase A does NOT
    • 2020 Q88 — CS Hi-Hi bistables energized to actuate; loss of VIB → 2/4 becomes 2/3; TS requires BYPASS not trip
    • 2023 Q1 — Low RC flow 2/3 coincidence / P-7 vs P-8 permissive logic
    • 2023 Q5 — OT Delta-T pressure input / OP Delta-T has no pressure input
    • 2023 Q21 — Containment Spray Logic / Channel Removed from Service|2023 Q21 — Containment spray 2/4 logic reduces to 2/3 with channel bypassed
    • 2023 Q34 — MPC Fails Low / PZR Pressure Response|2023 Q34 — MPC fails low / PORVs interlock from PZR pressure not MPC
    • 2023 Q35 — Reactor Trip Logic at 7% Power / Which Trip Active|2023 Q35 — PZR pressure high trip active at all power levels (no permissive)
    • 2023 Q36 — RCP Underfrequency Logic / 1/2 Taken Twice|2023 Q36 — RCP underfrequency 1/2 taken twice logic / individual breakers trip on UV not UF
    • 2023 Q53 — Containment Vacuum Relief Isolation Signals|2023 Q53 — Vacuum relief isolates on SI or CVI, not Phase A
    • 2023 Q56 — Rod Position Indication / Group Demand Step Counter / Plant Computer Group 1 only
    • 2023 Q65 — SSPS train disagreement / SI & FW ISOL lamp flashing / SI RESET green light
    • 2023 Q80 — ATWS FRSM-1 turbine trip verification via stop valve bi-stables on 2RP4
    • 2023 Q92 — PZR pressure channel failure / spurious trip+SI / RAL 11.3.2 reportability
    • 2022 Q1 — SSPS Train A/B UV coil and shunt coil assignments to RTBs/BYBs
    • 2022 Q3 — Phase A (ØA) safeguards actuation indication on 2CC1/2RP4
    • 2022 Q38 — RTB B opens / RTB A fails closed / 20-ET trips turbine
    • 2022 Q39 — Containment pressure channel logic / SI vs Phase B coincidence
    • 2022 Q40 — SSPS auctioneered 48VDC power supply / single loss no impact
    • 2022 Q63 — Steam dump P-12 (Lo-Lo Tavg) / Bypass Tavg requires both Train A AND B
    • 2022 Q85 — CFST Thermal Shock RED path priority over PURPLE SM and YELLOW HS
    • 2022 Q91 — TS 3.4.10.3 POPS / Mode 5 to Mode 4 entry prohibited with inoperable LTOP
    • 2019 Q11 — Containment Pressure channel loss: SI/Rx Trip 2/3→1/2 (deenergize to actuate) vs CS 2/4→2/3 (energize to actuate)
    • 2019 Q49 — EOP-TRIP-1 Step 1 manual trip sequence: Pistol Grips FIRST, then Bezels, then open E 6D and G 6D breakers
    • 2019 Q50 — OT Delta-T variable setpoint lowers as RCS pressure lowers (K3 pressure input); OP Delta-T varies with AFD not pressure
    • 2018 Q11 — RCP Undervoltage trip: 4KV Group Busses H and G at <70% normal voltage / 1/2 taken twice / interlocked with P-7