Q63 — Steam Dump P-12 / Bypass Tavg
041 A1.01 (2.9)
Given:
• Unit 2 reactor was tripped and is cooling down for a planned refueling outage.
• Steam Dumps are in MANUAL MS PRESSURE Control Mode.
• RCS cooldown rate is 70°F per hour.
Which ONE of the following completes the following statement concerning the expected operation of the steam dump system during the cooldown?
1. The RCS cooldown will stop when Tavg is less than the MAXIMUM setpoint of _(1)_.
2. In order to re-establish RCS cooldown, the operator will depress TRAIN _(2)_ BYPASS ON pushbutton(s).
• Unit 2 reactor was tripped and is cooling down for a planned refueling outage.
• Steam Dumps are in MANUAL MS PRESSURE Control Mode.
• RCS cooldown rate is 70°F per hour.
Which ONE of the following completes the following statement concerning the expected operation of the steam dump system during the cooldown?
1. The RCS cooldown will stop when Tavg is less than the MAXIMUM setpoint of _(1)_.
2. In order to re-establish RCS cooldown, the operator will depress TRAIN _(2)_ BYPASS ON pushbutton(s).
A. 1) 543°F
2) A OR B
2) A OR B
B. 1) 543°F
2) A AND B
2) A AND B
C. 1) 547°F
2) A AND B
2) A AND B
D. 1) 547°F
2) A OR B
2) A OR B
▶ Show Answer & Explanation
✓ B. Correct. When Tavg drops below 543°F (low-low Tavg 2/4 < 543°F, P-12), then all of the steam dump valves will close and the cooldown will stop and Tavg will eventually start to rise again. In order to reopen the steam dump valves following low-low Tavg, the operator is required to depress both Train A and Train B Bypass ON pushbuttons. This will allow only the Group 1 cooldown valves to be opened when Tavg Bypass is depressed.
✗ A. Incorrect. First part is correct. Second part is incorrect. Plausible because the applicant may incorrectly believe that when the BYPASS TAVG are depressed, then all group dump valves can be reopened and forget that only the cooldown (Group 1) valves can only be opened.
✗ C. Incorrect. First part is incorrect. Second part is correct. Plausible because 547°F is the setpoint for maintaining Tavg when the steam dumps are operating in Tavg Plant Trip Mode.
✗ D. Incorrect. First part is incorrect. Second part is incorrect. Plausible because 547°F is the setpoint for maintaining Tavg when the steam dumps are operating in Tavg Plant Trip Mode. Plausible because the applicant may incorrectly believe that when the BYPASS TAVG are depressed, then all group dump valves can be reopened and forget that only the cooldown (Group 1) valves can only be opened.
Ref: NOS05STDUMP-13 | LO: NOS05STDUMP-13, Obj 8.d — Describe the function of the following components and how their normal and abnormal operation affects the Steam Dump System: Low-Low Tavg | Source: New | Cognitive: Fundamental/Memory
Connections
- Related systems: Steam Dumps, RPS/SSPS
- Related exam: 2022 NRC Written Exam