Q76 — EOP-FRSM-1 RCP Trip During ATWS
EPE 29 G2.4.18 (4.0)
Given:
At time 1000;
• A Reactor Trip First Out annunciator is in alarm with the reactor at power.
• The reactor did NOT trip.
• The crew entered 1-EOP-FRSM-1, Response to Nuclear Power Generation - ATWS.
At time 1010;
• Power Range NIS are indicating 5.2%.
• Intermediate Range Startup Rate is -0.19 DPM.
• OHA D-36, RCP VIB HI, is LIT.
• PO reports 11 RCP motor flange vibration is at 6 mils and stable.
Which ONE of the following completes both statements in accordance with 1-EOP-FRSM-1?
Based on the above conditions, 11 RCP _(1)_ be stopped because _(2)_.
At time 1000;
• A Reactor Trip First Out annunciator is in alarm with the reactor at power.
• The reactor did NOT trip.
• The crew entered 1-EOP-FRSM-1, Response to Nuclear Power Generation - ATWS.
At time 1010;
• Power Range NIS are indicating 5.2%.
• Intermediate Range Startup Rate is -0.19 DPM.
• OHA D-36, RCP VIB HI, is LIT.
• PO reports 11 RCP motor flange vibration is at 6 mils and stable.
Which ONE of the following completes both statements in accordance with 1-EOP-FRSM-1?
Based on the above conditions, 11 RCP _(1)_ be stopped because _(2)_.
A. 1. should NOT
2. RCP operation will ensure thorough mixing of boron in the core
2. RCP operation will ensure thorough mixing of boron in the core
B. 1. should NOT
2. RCP operation can provide temporary core cooling during voided RCS conditions
2. RCP operation can provide temporary core cooling during voided RCS conditions
C. 1. should
2. RCP trip criteria have been met
2. RCP trip criteria have been met
D. 1. should
2. the remaining RCPs would provide adequate heat removal
2. the remaining RCPs would provide adequate heat removal
▶ Show Answer & Explanation
✓ B. Correct. Per 1-EOP-FRSM-1 Caution C1-1, RCPs should not be tripped with reactor power greater than 5%. During an ATWS, RCP operation could be beneficial by temporarily cooling the core under voided RCS conditions. If reactor power is > 5%, the RCP should not be tripped even if all normal running conditions are not satisfied. Manually tripping the RCP during some ATWS events could result in reduced heat removal and a challenge to fuel integrity. Based on the stem, 11 RCP trip criteria is met due to exceeding abnormal parameter for motor flange vibration > 5 mils and therefore, should not be stopped since reactor power is still greater than 5%.
✗ A. Incorrect. Part 1 is correct. Part 2 is incorrect. Plausible because stopping an RCP could result in boron stratification in the inactive RC loop which could cause lower boron RCS to backflow into the core and adding positive reactivity.
✗ C. Incorrect. Part 1 is incorrect. Part 2 is incorrect. Plausible because the motor flange vibration does exceed the RCP trip criteria of > 5 mils motor flange vibration and the SRO could believe the RCP should be tripped to prevent excessive motor and shaft vibration to damage the seals and potential loss of inventory.
✗ D. Incorrect. Part 1 is incorrect. Part 2 is incorrect. Plausible because the motor flange vibration does exceed the RCP trip criteria of > 5 mils motor flange vibration and the SRO could believe the RCP can be tripped with the remaining RCPs running will provide sufficient RC flow with the reactor subcritical (negative SUR).
Ref: 1-EOP-FRSM-1 (R40) | LO: NOS05FRSM00-05, Objective 5 | Source: New | Cognitive: Comprehension/Analysis
Connections
- Related systems: RCPs, Excore NIs
- Related EOPs: EOP-FRSM-1 — Response to Nuclear Power Generation
- Related exam: 2022 NRC Written Exam