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Exams > 2019 Q10 — PORV Constant Enthalpy Expansion

2019 Q10 — PORV Constant Enthalpy Expansion

⚠️ DRAFT
Q10 — PORV Constant Enthalpy Expansion 010 PZR PCS-K5.02 (2.6)
Given:
- A Unit 2 shutdown is in progress
- Pressurizer pressure is 415 psig and slowly lowering
- There is a suspected leak by of 2PR1 (PZR PORV)
- PRT pressure is 0 psig

Which ONE of the following completes the statements below?

If 2PR1 is leaking by, then the expected PORV tailpipe temperature will be approximately ___ °F.
A. 212
B. 280
C. 330
D. 450
▶ Show Answer & Explanation
✓ C. Correct. Leak by of 2PR1 is a constant enthalpy expansion process through a valve. Using steam tables and with PZR pressure at 415 psig (430 psia), the hg is approximately 1205 BTU/lbm. Using the Mollier diagram, the throttling process will go from 415 psig to 0 psig with hg (1205 BTU/lbm) remaining constant. This will correspond to a tailpipe temperature of approximately 330°F.
✗ A. Incorrect but plausible. Since the Mollier Diagram is very complex to read and interpret then any temperature between 212 and 450°F is plausible. 212°F is the boiling point for water/steam at 0 psig and 450°F is boiling point for water/steam at 515 psig.
✗ B. Incorrect but plausible. Since the Mollier Diagram is very complex to read and interpret then any temperature between 212 and 450°F is plausible. 212°F is the boiling point for water/steam at 0 psig and 450°F is boiling point for water/steam at 515 psig.
✗ D. Incorrect but plausible. Since the Mollier Diagram is very complex to read and interpret then any temperature between 212 and 450°F is plausible. 212°F is the boiling point for water/steam at 0 psig and 450°F is boiling point for water/steam at 515 psig.
Ref: GFES Bank | LO: NOS05PZRPRT-046 | Source: Bank (GFES Bank - Thermodynamic Processes P677) | Cognitive: Higher

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