Q20 — Misaligned Rods Required Action
APE05AA1.04 (3.9)
Given:
• Unit 2 was initially at 100% Power.
Subsequently, the following sequence of events occurs:
• Automatic Turbine runback occurs due to an issue with the stator water cooling system.
• During the load reduction, the RO reports that two (2) Control Bank D rods have stopped moving at 215 steps.
• The CRS enters S2.OP-AB.ROD-0001, Immovable / Misaligned Control Rods.
• The RO has placed the Rod Bank Selector Switch in MANUAL.
• Control Bank D Group Demand counters are presently at 185 steps.
• The runback terminates with reactor power at 80 %.
• Tavg is being maintained within +/- 1.5 °F of program.
In accordance with S2.OP-AB.ROD-0001, and assuming the two control rods will not be restored to operable status, which ONE of the following describes a required action that the crew will take.
• Unit 2 was initially at 100% Power.
Subsequently, the following sequence of events occurs:
• Automatic Turbine runback occurs due to an issue with the stator water cooling system.
• During the load reduction, the RO reports that two (2) Control Bank D rods have stopped moving at 215 steps.
• The CRS enters S2.OP-AB.ROD-0001, Immovable / Misaligned Control Rods.
• The RO has placed the Rod Bank Selector Switch in MANUAL.
• Control Bank D Group Demand counters are presently at 185 steps.
• The runback terminates with reactor power at 80 %.
• Tavg is being maintained within +/- 1.5 °F of program.
In accordance with S2.OP-AB.ROD-0001, and assuming the two control rods will not be restored to operable status, which ONE of the following describes a required action that the crew will take.
A. Place the Unit in Hot Shutdown.
B. Reduce power to < 50 % rated thermal power.
C. Place the Unit in Hot Standby.
D. Reduce power to < 75 % rated thermal power.
▶ Show Answer & Explanation
✓ C. Correct. S2.OP-AB.ROD-0001(Q), Immovable / Misaligned Control Rods directs placing the unit in Hot Standby if more than one rod is stuck / misaligned.
✗ A. Plausible because the candidate may believe that the procedure directs placing the unit in Hot Shutdown vice the actual directed Hot Standby.
✗ B. Plausible because the procedure, S2.OP-AB.ROD-0001(Q), Immovable / Misaligned Control Rods, directs reviewing QPTR based on the misaligned rod/rods. If QPTR Technical Specification limits were exceeded, Tech Spec 3.2.4 requires reducing power to less than 50% if the QPTR is not returned to within limits after 24 hours. Incorrect as the procedure specifically directs placing the unit in Hot Standby if more than one rod is stuck / misaligned.
✗ D. Plausible because this is true if only one control rod was stuck / misaligned. Incorrect because the stem states two rods are misaligned.
Ref: S2.OP-AB.ROD-0001(Q), Immovable / Misaligned Control Rods and Bases | LO: N/A | Source: New | Cognitive: Comprehension
Connections
- Related systems: Control Rod Drive, Stator Cooling Water
- Related procedures: AB.ROD-0001 — Immovable/Misaligned Control Rods
- Related tech specs: TS 3/4.1.3 — Movable Control Assemblies, TS 3/4.2 — Power Distribution
- Related exam: 2020 NRC Written Exam