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Exams > 2020 Q32 — EOP-FRTS-1 PTS Mitigation Basis

2020 Q32 — EOP-FRTS-1 PTS Mitigation Basis

⚠️ DRAFT
Q32 — EOP-FRTS-1 PTS Mitigation Basis 006000K5.04 (2.9)
Given:

The Unit 2 crew has entered 2-EOP-FRTS-1, Response to Imminent Pressurized Thermal Shock.

The procedure directs various mitigating actions including termination of SI and the starting of an RCP. What are the basis for these two mitigating actions?
A. The soak required by EOP-FRTS-1 requires SI to be secured. Starting an RCP provides the ability to utilize normal spray to depressurize the RCS.
B. ECCS flow is a contributor to the RCS cooldown and can prevent subsequent reduction in RCS pressure. Starting an RCP provides mixing of cold ECCS and warm RCS.
C. ECCS flow is a contributor to the RCS cooldown and can prevent subsequent reduction in RCS pressure. Starting an RCP minimizes the temperature gradient across the S/G tube sheets.
D. The soak required by EOP-FRTS-1 requires SI to be secured. Starting an RCP is used to equalize boron concentration throughout the RCS to ensure proper shutdown margin as the RCS cools.
▶ Show Answer & Explanation
✓ B. Correct. FRTS-1 bases states; "for an imminent PTS condition, ECCS flow may have contributed to the RCS cooldown or may prevent a subsequent reduction in RCS pressure." Additionally, the bases states; "in order to mix the cold incoming ECCS water and the warm reactor coolant water and thereby decrease the likelihood of a PTS condition, an RCP restart is attempted."
✗ A. Incorrect. Plausible because the candidate may believe that because no pressure changes are to be made during the soak that SI would be required to be terminated. Not correct as there are some SBLOCA conditions that SI flow cannot be terminated. Second part is true, but not relevant to the mitigation strategy in FRTS-1.
✗ C. Incorrect. Plausible because the first part is correct. Also plausible because the candidate may believe that thermal stresses across the S/G tube sheet are of an immediate concern and that starting the RCP would mitigate or lower the temperature gradient. Incorrect because it is not relevant to the mitigation strategy of FRTS-1.
✗ D. Incorrect. Plausible because the candidate may believe that because no pressure changes are to be made during the soak that SI would be required to be terminated. Not correct as there are some SBLOCA conditions that SI flow cannot be terminated. Second part is plausible as forced flow can help equalize boron concentrations, but incorrect as it is not relevant to the mitigation strategy of FRTS-1.
Ref: 2-EOP-FRTS-1, Response to Imminent Pressurized Thermal Shock Conditions and Bases | LO: N/A | Source: Bank – Salem Vision Database | Cognitive: Fundamental

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