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Exams > 2022 Q58 — ADFCS Steam Pressure Channel Failure

2022 Q58 — ADFCS Steam Pressure Channel Failure

⚠️ DRAFT
Q58 — ADFCS Steam Pressure Channel Failure 016 K3.12 (3.4)
Given:

• Unit 2 is at 100% Power.
• ALL systems are in normal alignment and in AUTO.
• The steam pressure channel associated with the Ovation Digital Feedwater Control System fails HIGH on 21 Steam Generator.

Which ONE of the following describes how the Ovation Digital Feedwater Control System will respond to this failure?

Note: MS10 — Atmospheric Steam Dump Relief Valve
A. 21MS10 will switch to MANUAL.
B. 21MS10 will OPEN.
C. ALL MS10's will remain in AUTO.
D. ALL MS10s will switch to MANUAL.
▶ Show Answer & Explanation
✓ A. Correct. A failure of one channel of steam pressure will result in the associated MS-10 loop switching to Manual control, and OHAs G-7 ADFCS Alternate Action and G-15 ADFCS TRBL. Ovation uses one pressure channel from each SG (4 total) into a Medium Signal Select (MSS) algorithm and with a failure, will select another good input and the other remaining MS10's will remain in auto.
✗ B. One steam pressure channel failure will not cause the associated MS-10 to open. Plausible because since only one pressure channel from each SG is used into Ovation system that the operator may incorrectly believe that only one pressure channel failing will cause the MS10 to open on the affected SG pressure channel.
✗ C. Plausible because the Ovation system is redundant and fault tolerant to loss of inputs. However, in this case, a loss of one SG pressure channel will cause the associated MS10 to swap to Manual.
✗ D. Plausible because since only one pressure channel from each SG is used into Ovation system that the operator may incorrectly believe that the Medium Signal Select (MSS) algorithm is not used and therefore with only one pressure channel failing will cause Ovation to select all the MS10s to swap to Manual.
Ref: NOS05ODFWCS-03 | LO: NOS05ODFWCS-03, Obj 8.g — Describe the function and operating characteristics for ADFCS components: Steam Pressure | Source: Bank — Salem | Cognitive: Comprehension/Analysis

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