Q13 — FW Line Break vs Steam Break
APE 54 AK1.01 (4.1)
Given:
• Unit 2 is at 100% Power.
• A Main Feedwater Line Break inside containment occurs on 21 Steam Generator.
Which ONE of the following completes both statements?
1. On a Main Feedwater Line Break, Narrow Range levels in the 21 SG will lower __(1)__ when compared to a Steam Line Break.
2. Immediately following the reactor trip, the RCS cooldown rate will be __(2)__ when compared to an equivalent size Steam Line Break.
• Unit 2 is at 100% Power.
• A Main Feedwater Line Break inside containment occurs on 21 Steam Generator.
Which ONE of the following completes both statements?
1. On a Main Feedwater Line Break, Narrow Range levels in the 21 SG will lower __(1)__ when compared to a Steam Line Break.
2. Immediately following the reactor trip, the RCS cooldown rate will be __(2)__ when compared to an equivalent size Steam Line Break.
A. 1) slower
2) less
2) less
B. 1) slower
2) more
2) more
C. 1) faster
2) more
2) more
D. 1) faster
2) less
2) less
▶ Show Answer & Explanation
✓ D. Correct. A Main Feedwater Line Break is expected to generate a Low-Low SG Level reactor trip due to the loss of feedwater at 100% power. Post Trip, RCS Tavg will rise due to lowering feed flow to the affected SG causing a decrease in heat transfer in that SG. A FW line break creates less cooling on the RCS because the loss of FW from the SG and out the break does not involve the removal of latent heat as occurs in a steam break.
✗ A. First part is incorrect. SG levels will lower faster during a feedwater line break. Second part is correct. Plausible because the operator may incorrectly determine that on a feed line break SG levels will lower slower compared to a steam line break.
✗ B. First part is incorrect. SG levels will lower faster during a feedwater line break. Second part is incorrect. Feedwater line break will have a lesser effect on RCS cooling. Plausible because the operator may incorrectly determine that on a feed line break SG levels will lower slower compared to a steam line break.
✗ C. First part is correct. Second part is incorrect. Feedwater line break will have a lesser effect on RCS cooling. Plausible because the operator may incorrectly determine how feed line break will effect RCS cooldown.
Ref: NOS05LOSC01 | LO: NOS05LOSC01, Objective 6 — For the following FSAR transients stated as items 6.1, 6.2, and 6.3 perform the tasks specified in the below requirements A, B, C, and D: Main Feed piping break | Source: New | Cognitive: Comprehension/Analysis
Connections
- Related systems: Feed & Condensate, Main Steam
- Related exam: 2022 NRC Written Exam