2023 Q31 — SBLOCA Break Location / Highest Peak Clad Temperature

✓ A. Correct. A cold leg break results in the highest peak clad temperature during a SBLOCA. This is due to thermodynamics and the fact that ECCS pumps inject into the cold legs. With a cold leg break, injected ECCS water can be lost directly out the break before reaching the core, reducing the effectiveness of core cooling and resulting in the highest PCT.

✗ B. Incorrect. A hot leg break results in the highest loss of flow but does not produce the highest peak clad temperature. ECCS injection into cold legs is more effective at reaching the core with a hot leg break since the break is downstream of the core.

✗ C. Incorrect. A CRDM housing break on the reactor head is an analyzed SBLOCA scenario but does not produce the worst PCT. The break size is limited and flow paths still allow effective ECCS delivery to the core.

✗ D. Incorrect. A pressurizer steam space break is an analyzed SBLOCA scenario but does not produce the worst PCT. The steam space break depressurizes the PZR but ECCS can still effectively deliver coolant to the core.

Ref: NOS05ECCS00-18 | Source: Bank - Braidwood 2018 RO41 | Cognitive: Comprehension/Analysis