Q85 — CFST Priority / FRTS-1 Thermal Shock
W E08 G2.4.21 (4.6)
Given:
• Unit 2 experienced a reactor trip and safety injection due to a steam line break downstream of the Main Steam Line Isolation Valves (MSIVs).
• ALL MSIVs failed to close.
• The crew is performing SI Termination steps per 2-EOP-LOSC-2, Uncontrolled Depressurization of All Steam Generators.
• Field operator reports that 23MS167 is now closed.
Subsequently, the STA observes the following;
• AFW flow to each SG is 1E+4 lbm/hr.
• All SG NR Levels are off-scale low.
• 21, 22, and 24 SG Pressures are 100 psig.
• 23 SG Pressure is 200 psig and rising.
• RCS Pressure is 1100 psig.
• ALL RCS T-Colds temperatures are < 230 °F.
• Intermediate Range SUR is +0.1 DPM.
Which ONE of the following describes the NEXT CRS action?
• Unit 2 experienced a reactor trip and safety injection due to a steam line break downstream of the Main Steam Line Isolation Valves (MSIVs).
• ALL MSIVs failed to close.
• The crew is performing SI Termination steps per 2-EOP-LOSC-2, Uncontrolled Depressurization of All Steam Generators.
• Field operator reports that 23MS167 is now closed.
Subsequently, the STA observes the following;
• AFW flow to each SG is 1E+4 lbm/hr.
• All SG NR Levels are off-scale low.
• 21, 22, and 24 SG Pressures are 100 psig.
• 23 SG Pressure is 200 psig and rising.
• RCS Pressure is 1100 psig.
• ALL RCS T-Colds temperatures are < 230 °F.
• Intermediate Range SUR is +0.1 DPM.
Which ONE of the following describes the NEXT CRS action?
A. Return to 2-EOP-LOSC-1, Faulted Steam Generator Isolation.
B. Transition to 2-EOP-FRSM-1, Response to Nuclear Generation.
C. Transition to 2-EOP-FRHS-5, Response to Steam Generator Low Level.
D. Transition to 2-EOP-FRTS-1, Response to Thermal Shock.
▶ Show Answer & Explanation
✓ D. Correct. A RED Path in the Thermal Shock Status Tree exists due to all RCS T-Cold cooldown rates not less than 100 °F in the last 60 minutes and all RCS pressure/temperature points are not to the right of Limit A in Figure 4A (T-Colds less than 230 °F and RCS pressure at 1100 psig).
✗ A. Incorrect. Plausible because this is a required transition when a faulted SG is recovered. With 23 SG isolated and pressure rising, the CRS will not return to 2-EOP-LOSC-1 because SI Termination is in progress.
✗ B. Incorrect. Plausible because the SRO may believe this is the higher RED path. SUR of +0.1 DPM is a PURPLE Path in the Shutdown Margin Status Tree, which is not higher than a RED Path in Thermal Shock Status Tree.
✗ C. Incorrect. Plausible because the low level in the SGs are valid but not the highest priority. Low SG levels is a YELLOW Path in the Heat Sink Status Tree and therefore not a priority.
Ref: 2-EOP-CFST-1 (R41) | LO: NOS05FRTS00-03, Objective 1 | Source: New | Cognitive: Comprehension/Analysis
Connections
- Related systems: Main Steam, AFW, RCS, Excore NIs
- Related EOPs: EOP-FRTS-1 — Response to Imminent Pressurized Thermal Shock, EOP-LOSC-2 — Uncontrolled Depressurization of All Steam Generators, EOP-LOSC-1 — Loss of Secondary Coolant, EOP-FRSM-1 — Response to Nuclear Power Generation
- Related exam: 2022 NRC Written Exam