Scenario 1 — Power Ascension / Station Blackout
Simulator | 6 Events | 2 Critical Tasks
Initial Conditions: IC-201: 90% power, MOL; 23 Charging Pump is in service. The following equipment is out of service: 2C EDG C/T for governor oil replacement and fuel rack lube.
Turnover: The crew is directed to continue power ascension to 100% power at 10% per hour IAW S2.OP-IO.ZZ-0004 using dilution, control rods and turbine load control.
Turnover: The crew is directed to continue power ascension to 100% power at 10% per hour IAW S2.OP-IO.ZZ-0004 using dilution, control rods and turbine load control.
Major Events:
- Power Ascension to 100% at 10%/hour
- RCS Wide Range Pressure Channel (2PT-405) fails low (TS only)
- PZR Level Channel 1 fails low (TS)
- Loss of #4 SPT and Loss of 23 CW Bus (power reduction) (TS)
- Loss of Offsite Power
- Loss of 2A Vital Bus and 2B EDG trips on overspeed
▶ Show Event Sequence & Expected Responses
| # | Event | Expected Crew Response |
|---|---|---|
| 1 | Power Ascension to 100% | CRS holds crew brief to discuss Rx Plan for power ascension IAW S2.OP-IO.ZZ-0004. RO commences dilution IAW S2.OP-SO.CVC-0006. PO raises main generator loading IAW S2.OP-SO.TRB-0001. |
| 2 | RCS Wide Range Pressure Channel 2PT-405 fails low | RO reports OHA D-40 SUBCLG CH A MARGIN LO. RO reports Subcooling Channel A lost on 2RP4 and recorder on 2CC2. Crew refers to ARP, determines invalid indication. CRS enters TS 3.3.3.7 Action a.1 (30 days). |
| 3 | PZR Level Channel 1 fails low | RO reports OHA E-36, PZR HTR OFF LVL LO. Letdown isolates. CRS enters AB.CVC-0001, Loss of Charging. RO takes manual control of charging flow, selects operable channel for Control/Alarm/Recorder, energizes PZR heaters to normal alignment. Restores letdown: opens 2CV7, 2CV18 in Manual, opens 2CV2 and 2CV277 in Auto, ensures charging flow ~85-90 gpm, opens one letdown orifice. CRS enters TS 3.3.1.1 Action 6 (6 hours). |
| 4 | Loss of #4 SPT and Loss of 23 CW Bus | PO reports 500 KV Bus Section 1 de-energized, loss of #4 SPT, all Vital Buses energized from 24 SPT. 21A-23A CW pumps trip. Crew enters AB.CW-0001. PO reports condenser DTs exceed 27 F — turbine load reduction to less than 80% required. Crew briefs reactivity plan, initiates load reduction IAW AB.LOAD-0001. Crew enters AB.LOOP-0003, Partial Loss of Offsite Power. PO re-energizes 23 CW Bus from Bus Section 24 via cross-tie breaker IAW Attachment 4. CRS enters TS 3.8.1.1 Action C (1 hour and 12 hours) for one offsite source and one EDG inoperable. |
| 5 | Loss of Offsite Power | Reactor automatically trips. RO performs TRIP-1 immediate actions: trips reactor, confirms trip, trips main turbine. All 4KV Vital Buses de-energize (2A Vital Bus lost on Bus Differential protection, 2B EDG trips on overspeed 30 seconds after trip). Crew transitions to EOP-LOPA-1, Loss of All AC Power. |
| 6 | Loss of all AC — EDG recovery | RO performs LOPA-1 immediate actions. Closes 2CV2 and 2CV277. CRS dispatches operator to de-energize all SECs. PO stops 2A EDG (no SW pumps running). Crew identifies 2C EDG as recovery path (2B EDG overspeed with bent fuel rack, 2A Vital Bus lost on Bus Differential). After SI Reset, maintenance returns 2C EDG. PO starts 2C EDG, closes output breaker to energize 2C 4KV Vital Bus [CT#1]. PO starts 25 or 26 SW pump for EDG cooling [CT#2]. |
Critical Tasks:
CT#1 (CT-24): Energize at least one AC emergency bus before transition out of EOP-LOPA-1. Safety significance: failure to energize an emergency bus results in loss of all pumped ECCS capability and station blackout conditions with no forced cooling or RCP seal injection. The crew must identify that 2C EDG (returned from maintenance) is the only available path after 2A Bus Differential and 2B EDG overspeed trip.
CT#2 (CT-25): Manually start one SW pump for EDG cooling before transition out of EOP-LOPA-1. Safety significance: without SW cooling, the running EDG will overheat and trip, returning the plant to station blackout. The crew must recognize that no SW pumps are running and start one immediately after energizing the bus.
CT#1 (CT-24): Energize at least one AC emergency bus before transition out of EOP-LOPA-1. Safety significance: failure to energize an emergency bus results in loss of all pumped ECCS capability and station blackout conditions with no forced cooling or RCP seal injection. The crew must identify that 2C EDG (returned from maintenance) is the only available path after 2A Bus Differential and 2B EDG overspeed trip.
CT#2 (CT-25): Manually start one SW pump for EDG cooling before transition out of EOP-LOPA-1. Safety significance: without SW cooling, the running EDG will overheat and trip, returning the plant to station blackout. The crew must recognize that no SW pumps are running and start one immediately after energizing the bus.
EOP Pathway:
S2.OP-AB.CVC-0001 (PZR level channel fail) → S2.OP-AB.CW-0001 (CW pump trips) → S2.OP-AB.LOOP-0003 (partial LOOP) → S2.OP-AB.LOAD-0001 (load reduction for DTs) → EOP-TRIP-1 (reactor trip on LOOP) → EOP-LOPA-1 (all three 4KV Vital Buses de-energized) → Scenario terminated after 2C 4KV Vital Bus energized and SW pump started for EDG cooling
S2.OP-AB.CVC-0001 (PZR level channel fail) → S2.OP-AB.CW-0001 (CW pump trips) → S2.OP-AB.LOOP-0003 (partial LOOP) → S2.OP-AB.LOAD-0001 (load reduction for DTs) → EOP-TRIP-1 (reactor trip on LOOP) → EOP-LOPA-1 (all three 4KV Vital Buses de-energized) → Scenario terminated after 2C 4KV Vital Bus energized and SW pump started for EDG cooling
Source: 19-01 NRC ESG-1 | View Scenario PDF
Connections
- Related systems: 4KV, EDGs, Service Water, CVCS, Pressurizer & PRT, Circ Water, 500KV, SECs
- Related EOPs: EOP-TRIP-1 — Reactor Trip or Safety Injection, EOP-LOPA-1 — Loss of All AC Power
- Related procedures: AB.CVC-0001 — Loss of Charging, AB.CW-0001 — Circulating Water Malfunction, AB.LOOP-0003 — Partial Loss of Offsite Power, AB.LOAD-0001 — Rapid Load Reduction, AB.LOOP-0001 — Loss of All Offsite Power
- Related exam: 2020 NRC Operating Exam