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Exams > 2018 Q91 — Turbine Runback / Rod Insertion Limit

2018 Q91 — Turbine Runback / Rod Insertion Limit

⚠️ DRAFT
Q91 — Turbine Runback / Rod Insertion Limit 045 MT/G-A2.12 (2.8)
Given:
• A Unit 2 Turbine Runback from 100% Reactor Power has occurred
• Valid ROD INSERT LIMIT LO and ROD INSERT LIMIT LO-LO alarms are present

Which ONE of the following completes the statements below?

LCO 3.1.1.1 (SHUTDOWN MARGIN - TAVG ≥ 200 °F) _(1)_ met.
In accordance with the ROD INSERT LIMIT LO-LO Alarm Response Procedure, the crew will _(2)_ to restore Control Rods above the Rod Insertion Limit.

NOTE:
• LCO NOT met = REQUIRED ACTIONS must be performed
• LCO met = NO REQUIRED ACTIONS must be performed
A. (1) is NOT    (2) raise turbine power to counter the effects of the runback
B. (1) is NOT    (2) perform an Emergency Boration
C. (1) is    (2) raise turbine power to counter the effects of the runback
D. (1) is    (2) perform an Emergency Boration
▶ Show Answer & Explanation
✓ B. Correct. For Part 1, with the ROD INSERT LIMIT LO-LO alarm present, the control rods are actually below the RIL. Consequently, SR 4.1.1.1.b (When in MODE 1 or MODE 2 with Keff greater than or equal to 1.0, in accordance with the Surveillance Frequency Control Program by verifying that control banks are within the limits in the COLR per Specification 3.1.3.5) is not met. With SR 4.1.1.1 not being met, LCO 3.1.1.1 is also NOT met. For Part 2 and in accordance with the ROD INSERT LIMIT LO-LO Alarm Response Procedure, the crew can perform S2.OP-SO.CVC-0008 (Rapid Boration) ONLY to restore Control Rods above the Rod Insertion Limit.
✗ A. Incorrect but plausible. Part 1 is correct. For Part 2, raising turbine power will cause RCS TAVG to lower which would cause Control Rods to automatically withdraw. Consequently, the candidate could incorrectly conclude that the ROD INSERT LIMIT LO-LO Alarm Response Procedure allows the crew to raise turbine power to restore Control Rods above the Rod Insertion Limit.
✗ C. Incorrect but plausible. For Part 1, the candidate could incorrectly conclude that SR 4.1.1.1 only requires a calculation of Shutdown Margin (SDM) and LCO 3.1.1.1 is met until the SDM calculation confirms that SDM is not adequate. For Part 2, raising turbine power will cause RCS TAVG to lower which would cause Control Rods to automatically withdraw. Consequently, the candidate could incorrectly conclude that the ROD INSERT LIMIT LO-LO Alarm Response Procedure allows the crew to raise turbine power to restore Control Rods above the Rod Insertion Limit.
✗ D. Incorrect but plausible. For Part 1, the candidate could incorrectly conclude that SR 4.1.1.1 only requires a calculation of Shutdown Margin (SDM) and LCO 3.1.1.1 is met until the SDM calculation confirms that SDM is not adequate. Part 2 is correct.
Ref: ROD INSERT LIMIT LO-LO Alarm Response Procedure, LCO 3.1.1.1 | LO: NOS05RODS00-12 Obj 13 | Source: Modified Bank | Cognitive: Higher | SRO Only: Analyze plant parameters and determine procedure to implement after rods go below RIL during turbine runback

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