2022 Q11 — SGTR Natural Circulation

✓ A. Correct. In EOP-SGTR-1 step 38.1, Monitor for Natural Circulation, one of the indications for verifying natural circulation is determining if the RCS T-Colds are at saturation temperature for SGs. The unaffected loop SG pressure should be around the setpoint of the MS10s which are normally set at 1015 psig (or 1030 psia). The affected loop SG pressure with the SGTR will have its MS10 set to 1045 psig (1060 psia) per step 3 of EOP-SGTR-1. Using steam tables, the saturation temperature at 1030 psia is approximately 548 °F and for 1060 psia is approximately 552 °F. Therefore the saturation temperature expected for the unaffected loops (intact SG) would be 548 °F. Per step 38.1 of EOP-SGTR-1, if natural circulations is not occurring, then raise the steam flow. In this case with a loss of offsite power, the PO would adjust (open) the MS10s on the unaffected loops to raise the steam flow.

✗ B. First part is correct. Second part is incorrect. With a loss of offsite power steam dumps are not available and only MS10s can be used. Plausible because the operator may believe that steam dumps are still available. Incorrect in that with the Loss of all Offsite Power (LOOP) all of the circulators are without power and be out of service. At least one circulator must be in service in a condenser section in order for that condenser section steam dump valves to operate. So in this case, when the LOOP occurs and all circulators trip, the steam dumps will receive a blocking signal and all steam dumps will close.

✗ C. First part is incorrect. This is the saturation temperature using the SG pressure on the ruptured SG (1045 psig or 1060 psia). Second part is correct. Plausible because the operator may incorrectly use the SG pressure on the ruptured SG instead of the intact SGs.

✗ D. First part is incorrect. This is the saturation temperature using the SG pressure on the ruptured SG (1060 psia). Second part is incorrect. With a loss of offsite power steam dumps are not available and only MS10s can be used. Incorrect in that with the Loss of all Offsite Power (LOOP) all of the circulators are without power and be out of service. At least one circulator must be in service in a condenser section in order for that condenser section steam dump valves to operate. So in this case, when the LOOP occurs and all circulators trip, the steam dumps will receive a blocking signal and all steam dumps will close. Plausible because the operator may incorrectly use the SG pressure on the ruptured SG instead of the intact SGs.

Ref: 2-EOP-SGTR-1 Rev 40 | LO: NOS05SGTR01-06, Objective 6 — Determine the indications that are monitored to ensure proper system/component operation for each step in 2-EOP-SGTR-1 | Source: New | Cognitive: Comprehension/Analysis