Q47 — CSF Priority and Monitoring
G2.4.23 (3.6)
Given:
• The crew is monitoring the Critical Safety Functions
• The STA has verified the following Critical Safety Function Status Trees (CFSTs):
[CFST status table provided in exam — based on answer, Heat Sink is Red and Core Cooling is Purple; remaining CSFs are lower priority]
In accordance with OP-AA-101-111-1003 (Use Of Procedures), which ONE of the following completes the statements below?
Based on the Functional Restoration Implementation Priority, the crew is required to FIRST address the challenge to _(1)_.
With verified Red and Purple CFSTs, OP-AA-101-111-1003 states that the CFSTs should be monitored _(2)_.
• The crew is monitoring the Critical Safety Functions
• The STA has verified the following Critical Safety Function Status Trees (CFSTs):
[CFST status table provided in exam — based on answer, Heat Sink is Red and Core Cooling is Purple; remaining CSFs are lower priority]
In accordance with OP-AA-101-111-1003 (Use Of Procedures), which ONE of the following completes the statements below?
Based on the Functional Restoration Implementation Priority, the crew is required to FIRST address the challenge to _(1)_.
With verified Red and Purple CFSTs, OP-AA-101-111-1003 states that the CFSTs should be monitored _(2)_.
A. _(1)_ Core Cooling / _(2)_ every 10-20 minutes
B. _(1)_ Core Cooling / _(2)_ continuously
C. _(1)_ Heat Sink / _(2)_ every 10-20 minutes
D. _(1)_ Heat Sink / _(2)_ continuously
▶ Show Answer & Explanation
✓ D. Correct. For Part 1, IAW OP-AA-101-111-1003, CSF Hierarchy (high to low) is SHUTDOWN MARGIN, CORE COOLING, HEAT SINK, THERMAL SHOCK, CONTAINMENT ENVIRONMENT and COOLANT INVENTORY. Additionally, CFST Color Hierarchy (high to low) is red, purple, yellow, and green. Based on the status of the CFSTs, the crew is required to first address the challenge to Heat Sink. For Part 2, with verified Red and Purple CFSTs, OP-AA-101-111-1003 states that the CFSTs should be monitored continuously.
✗ A. Incorrect but plausible. Since Core Cooling is a higher CSF than Heat Sink, the candidate could incorrectly conclude that based on the status of the CSFTs, the crew is required to first address the challenge to Core Cooling. For Part 2, OP-AA-101-111-1003 does have a provision to monitor CSFTs every 10-20 minutes (if no condition more serious than YELLOW is encountered). Consequently, the candidate could incorrectly conclude that with verified Red and Purple CSFTs, OP-AA-101-111-1003 states that the CFSTs should be monitored every 10-20 minutes.
✗ B. Incorrect but plausible. Since Core Cooling is a higher CSF than Heat Sink, the candidate could incorrectly conclude that based on the status of the CSFTs, the crew is required to first address the challenge to Core Cooling. Part 2 is correct.
✗ C. Incorrect but plausible. Part 1 is correct. For Part 2, OP-AA-101-111-1003 does have a provision to monitor CSFTs every 10-20 minutes (if no condition more serious than YELLOW is encountered). Consequently, the candidate could incorrectly conclude that with verified Red and Purple CSFTs, OP-AA-101-111-1003 states that the CFSTs should be monitored every 10-20 minutes.
Ref: NOS05PROCED-08 (Use and Control of Procedures) | LO: NOS05PROCED-08 LO 5 | Source: New | Cognitive: Higher
Connections
- Related procedures: OP-AA-101-111-1003 — Use of Procedures
- Related EOPs: EOP-CFST-1 — Critical Safety Function Status Trees, EOP-FRHS-1 — Response to Loss of Secondary Heat Sink
- Related exam: 2018 NRC Written Exam