JPM RO-A1 — Determine Maximum Reactor Vessel Vent Time
Admin | RO/SRO | G2.1.25 (3.9)
Location: Classroom
Time-Critical: No
Alternate Path: No
Estimated Time: 10 minutes
Initial Conditions:
- Unit 2 has experienced a small break LOCA.
- The crew has performed an RCS cooldown and depressurization in EOP-LOCA-2.
- During the depressurization the crew experienced some complications and indications of upper head voiding are now present.
- STA reports a valid CFST YELLOW path exists on Coolant Inventory.
- The TSC recommends initiating EOP-FRCI-3, Response to Void in Reactor Vessel.
Initiating Cue:
- You are the extra NCO.
- The crew has completed actions in EOP-FRCI-3 up to step 17.3 and has directed you to PERFORM Attachment 1 of EOP-FRCI-3 to determine the maximum venting time.
- The following conditions exist in Unit 2 containment:
- Containment temperature is 140 F
- Containment hydrogen concentration is 2.3%
- RCS pressure is 1600 psig
- During your calculations, ONLY perform "rounding" when determining the vent time to the nearest tenths.
Time-Critical: No
Alternate Path: No
Estimated Time: 10 minutes
Initial Conditions:
- Unit 2 has experienced a small break LOCA.
- The crew has performed an RCS cooldown and depressurization in EOP-LOCA-2.
- During the depressurization the crew experienced some complications and indications of upper head voiding are now present.
- STA reports a valid CFST YELLOW path exists on Coolant Inventory.
- The TSC recommends initiating EOP-FRCI-3, Response to Void in Reactor Vessel.
Initiating Cue:
- You are the extra NCO.
- The crew has completed actions in EOP-FRCI-3 up to step 17.3 and has directed you to PERFORM Attachment 1 of EOP-FRCI-3 to determine the maximum venting time.
- The following conditions exist in Unit 2 containment:
- Containment temperature is 140 F
- Containment hydrogen concentration is 2.3%
- RCS pressure is 1600 psig
- During your calculations, ONLY perform "rounding" when determining the vent time to the nearest tenths.
Task Standard:
Calculates Maximum Venting Time of 4.5 mins (4.2 - 4.7 mins acceptable band).
Calculates Maximum Venting Time of 4.5 mins (4.2 - 4.7 mins acceptable band).
▶ Show Critical Steps & Key Actions
| Step | Critical Element | Standard |
|---|---|---|
| 1 | Record data from initial conditions (containment temp, H2 concentration, RCS pressure) | Records provided data in steps 1.1 through 1.3 |
| 2.1 * | Calculate containment absolute temperature (Tabs) | Tabs = 140 + 460 = 600 R |
| 2.2 * | Calculate containment temperature standardization factor (Tfact) | Tfact = 492/600 = 0.82 |
| 2.3 * | Calculate containment air volume (V) at STP | V = 2.62E06 x 0.82 = 2148400 ft3 |
| 3.3 * | Calculate maximum vent volume (M) | M = (3.0% - 2.3%) x 2148400 / 100% = 15038.8 ft3 |
| 4.3 * | Determine hydrogen vent flow rate from Figure 1 at 1600 psig | Using Figure 1, determines Hydrogen Flow Rate of 3333 cfm (+/- 100 cfm readability allowance) |
| 4.4 * | Calculate maximum vent time (Tv) | Tv = 15038.8 / 3333 = 4.5 mins (4.2 - 4.7 mins acceptable) |
Key Decision Point:
Step 4.3 is the discriminating step -- the applicant must correctly read the Hydrogen Flow Rate from Figure 1 at 1600 psig RCS pressure (3333 cfm). The graph has readability challenges, so a +/- 100 cfm allowance is factored into the acceptable vent time band. The final calculation in step 4.4 (Tv = M/F) is straightforward, but depends entirely on the correct flow rate from the graph. Rounding should only be applied at the final vent time calculation (to nearest tenths).
Step 4.3 is the discriminating step -- the applicant must correctly read the Hydrogen Flow Rate from Figure 1 at 1600 psig RCS pressure (3333 cfm). The graph has readability challenges, so a +/- 100 cfm allowance is factored into the acceptable vent time band. The final calculation in step 4.4 (Tv = M/F) is straightforward, but depends entirely on the correct flow rate from the graph. Rounding should only be applied at the final vent time calculation (to nearest tenths).
Ref: 2-EOP-FRCI-3 (Rev 40) | Task: N1150410501 | K/A: G2.1.25 — Ability to interpret reference materials, such as graphs, curves, tables | Source: Bank (Rev 02) | View JPM PDF
Connections
- Related systems: RCS, Containment
- Related EOPs: EOP-FRCI-3 — Response to Void in Reactor Vessel
- Related exam: 2022 NRC Operating Exam