Q11 — EDG Loading Limits for PZR Heaters
000056G2.1.25 (3.9)
Given:
• Unit 2 was at 100% Power when a Loss of Off-Site Power occurred.
• Operators have transitioned to 2-EOP-TRIP-2, Reactor Trip Response.
• All Emergency Diesel Generators are loaded onto their respective 4KV Vital Buses.
The CRS has directed you to energize the 21 PZR Backup Heaters from the 2C Vital Bus in accordance with the station operating procedure.
A procedural caution states the following; "Aligning pressurizer heaters to vital bus adds approximately 210 KW to bus load".
The 2C diesel is currently loaded to the 2000 hour limit. In order to add the PZR heater load of 210 KW and NOT exceed the 2000 hour limit, the current 2C diesel loading must be adjusted to no greater than ______.
• Unit 2 was at 100% Power when a Loss of Off-Site Power occurred.
• Operators have transitioned to 2-EOP-TRIP-2, Reactor Trip Response.
• All Emergency Diesel Generators are loaded onto their respective 4KV Vital Buses.
The CRS has directed you to energize the 21 PZR Backup Heaters from the 2C Vital Bus in accordance with the station operating procedure.
A procedural caution states the following; "Aligning pressurizer heaters to vital bus adds approximately 210 KW to bus load".
The 2C diesel is currently loaded to the 2000 hour limit. In order to add the PZR heater load of 210 KW and NOT exceed the 2000 hour limit, the current 2C diesel loading must be adjusted to no greater than ______.
A. 2890 KW
B. 2650 KW
C. 2390 KW
D. 2540 KW
▶ Show Answer & Explanation
✗ A. Incorrect. Plausible if the candidate believes that the 2000 hour limit is 3100 Kw (actual 30 minute rating).
✗ B. Incorrect. Plausible if the candidate believes that the 2000 hour limit is 2860 Kw (actual 2 hour rating).
✗ C. Incorrect. Plausible if the candidate believes that the 2000 hour limit is 2600 Kw (actual Continuous rating).
✓ D. Correct. The station operating procedure, S2.OP-SO.PZR-0010, Pressurizer Backup Heaters Power Supply Transfer, states; "Maximum diesel generator load is 2750 KW (2000 hr rating)". 2750 - 210 = 2540 KW.
Ref: 2-EOP-TRIP-2 and BASES, S2.OP-SO.PZR-0010, NOS05TRP002-07, ELO 1 | LO: N/A | Source: New | Cognitive: Fundamental/Memory
Connections
- Related systems: EDGs, Pressurizer & PRT
- Related procedures: S2.OP-SO.PZR-0010 — Pressurizer Backup Heaters Power Supply Transfer
- Related EOPs: EOP-TRIP-2 — Reactor Trip Response
- Related exam: 2020 NRC Written Exam