ML24317A223
| ML24317A223 | |
| Person / Time | |
|---|---|
| Site: | Vogtle  |
| Issue date: | 11/12/2024 |
| From: | Southern Nuclear Operating Co |
| To: | John Lamb NRC/NRR/DORL/LPL2-1 |
| References | |
| EPID L-2024-LRM-0128 | |
| Download: ML24317A223 (1) | |
Text
Proposed Vogtle Electric Generating Plant Units 3 & 4 License Amendment Request Revise Various Technical Specifications Shutdown Actions Mode Change Restrictions November 19, 2024
Agenda Description Reason for Request with Examples Technical Evaluation Markup Examples Schedule
Shutdown Actions Mode Change Restrictions DESCRIPTION
- Types of Technical Specification MODE 5 & 6 Required Actions that Can Present Conflicts or Restrictions in Moving between MODES 5 & 6 Initiate action to establish 20% pressurizer level with the RCS pressure boundary intact.
Initiate action to establish RCS VENTED.
Initiate action to establish RCS VENTED and establish 20% pressurizer level.
Initiate action to open RCS pressure boundary and establish 20% pressurizer level.
Initiate action to open the RCS pressure boundary.
Initiate action to establish water level 23 feet above the top of the reactor vessel flange -
OR - Initiate action to establish a pressurizer level above the P-12 interlock Initiate action to remove the upper internals.
Open a containment air flow path 6 inches in diameter.
Open containment equipment hatch or containment airlock.
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Shutdown Actions Mode Change Restrictions DESCRIPTION (Impacted Actions)
TS 3.3.8 Functions 1, 7, 14, 15, 16 & 18, Actions J, K, L, M, N & P TS 3.3.9 Functions 2, 6, 7, 8, 9 & 15, Actions G, H, I, J, K, & L TS 3.3.10 Functions 1 and 2, Actions C, D, & E TS 3.3.16, Action B & C TS 3.4.12, Action D TS 3.4.13, Actions C & D TS 3.5.3, Action E TS 3.5.5, Action E TS 3.5.7, Action F TS 3.5.8, Action F TS 3.6.4, Action C TS 3.6.5, Action C TS 3.6.6, Actions E & F TS 3.6.7, Action B TS 3.6.9, Action G 4
Shutdown Actions Mode Change Restrictions REASON FOR REQUEST
- Operators should not be presented with conflicting requirements.
- Excessively prescriptive actions during MODE 5 and MODE 6 can create substantial outage impacts such as adding to the critical path activities and prevention of resumption of operation without commensurate safety benefit.
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Shutdown Actions Mode Change Restrictions Example 1: TS 3.5.3, CMT & TS 3.5.7, IRWST TS 3.5.3 Applicability of Mode 5 With the RCS not VENTED Default Required Action E.1 - Initiate action to be in MODE 5 with the RCS VENTED TS 3.5.7 Applicability of Mode 5 Default Required Action F.1 - Initiate action to establish 20% pressurizer level with the RCS pressure boundary intact Potential for conflicting requirements when both CMT and IRWST are inoperable:
RCS VENTED and RCS intact cannot be concurrently met Unit 3 has experienced two occurrences with recent plant trips where both CMT and IRWST were concurrently inoperable (one or both LCOs met prior to entering default Actions)
The establish 20% pressurizer level also prevents proceeding to MODE 6 which exits the Applicability Proposed changes provide the operator with the ability to choose safe operation consistent with revised TS and the ability to exit Applicability (which is generally always a safe option) 6
Shutdown Actions Mode Change Restrictions Example 2: TS 3.3.8, Table 3.3.8-1, Function 14, RCS Wide Range Pressure -
Low and Function 18, IRWST Lower Narrow Range Level - Low 3 Both have Applicability of MODE 5 and MODE 6 With upper internals in place F14 in M5 > Required Action K.2 - Immediately Initiate action to open RCS pressure boundary and establish 20% pressurizer level.
- Potential conflict with inoperable Function 18 leading to Action M F18 in M5 > Required Action M.3 - Within 12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br /> Initiate action to establish a pressurizer level 20% with the RCS pressure boundary intact.
- Potential for conflicting requirements when both Functions are inoperable:
RCS pressure boundary cannot be concurrently open and intact
- The establish 20% pressurizer level also prevents proceeding to MODE 6
- Proposal gives operator ability to choose safe operation without conflicting TS and the ability to proceed with outage activities in MODE 6 7
Shutdown Actions Mode Change Restrictions TECHNICAL EVALUATION - Background
- NUREG-1449 (ML063470582), Shutdown and Low-Power Operation at Commercial Nuclear Power Plants in the United States (1993)
- NRC Staff evaluations & insights regarding shutdown and low-power operation
- Insights were being factored into light water reactor design reviews
- Additional requirements likely forthcoming in rulemaking
- Concluded current (1997) controls were sufficient
- Evolved through NRC and Industry actions & provided acceptable level of risk
- SRM withheld authorization for rulemaking
- NRC Report Adequacy of Implementation of Voluntary Industry Initiative on Shutdown Risk Rev. 1 (ML18113A300)
- Concluded additional regulatory actions are unnecessary to ensure adequate implementation of the risk-significant voluntary industry initiatives 8
Shutdown Actions Mode Change Restrictions TECHNICAL EVALUATION - VEGP Overview NUREG-1449 Insights factored into AP600 (reviewed 1992-1998)
AP1000 developed directly from AP600 (submitted 2002)
- AP1000 reviews did not revisit decisions to include shutdown TS STS NUREG-1431 developed during approximately same time period
- STS NUREG-1431 did not add additional shutdown TS (opted to wait for requirements)
- NUREG-1431 ESFAS Instrumentation (3.3.2) contains no MODE 5 or 6 applicability
- NUREG-1431 ECCS (3.5) contains no MODE 5 or 6 applicability
- NUREG-1431 Containment Systems (3.6) contains no MODE 5 or 6 applicability
- However, NUREG-1431 (Revs. 3, 4, 5) STS Bases (e.g., STS 3.8.5 Bases) and the VEGP Units 3&4 TS 3.8.2 Bases (DC Sources - Shutdown) recognize:
As a result, in addition to the requirements established in the Technical Specifications, the industry has adopted NUMARC 91-06, "Guidelines for Industry Actions to Assess Shutdown Management," as an Industry initiative to manage shutdown tasks and associated electrical support to maintain risk at an acceptable low level. This may require the availability of additional equipment beyond that required by the shutdown Technical Specifications.
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Shutdown Actions Mode Change Restrictions TECHNICAL EVALUATION - VEGP Overview NUMARC 91-06 included in VEGP 3&4 licensing basis UFSAR Section 19.7, Shutdown Defense-In-Depth The Shutdown Defense-In-Depth (DID) model was developed following NUMARC 91-06 (Reference 13), EPRI TR-1013501 (Reference 14) and EPRI TR-1016231 (Reference 15) methodology. This qualitative shutdown DID risk assessment is intended to support the requirements of Article (a)(4) of 10CFR50.65. This model includes evaluations of key safety functions applicable to low power and shutdown conditions to support the development of shutdown critical safety function status tree for the identified plant operating states.
References:
- 13. NUMARC 91-06, Guidelines for Industry Actions to Assess Shutdown Management, December 1991.
- 14. EPRI TR-1013501, Qualitative Risk Assessment Methods for Shutdown Risk Management, Electric Power Research Institute, Palo Alto, CA: November 2006.
- 15. EPRI TR-1016231, Development of a Shutdown Qualitative Risk Assessment Standard, Electric Power Research Institute, Palo Alto, CA: January 2008.
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Shutdown Actions Mode Change Restrictions TECHNICAL EVALUATION - VEGP Overview NUMARC 93-01 also included in VEGP 3&4 licensing basis UFSAR Section 17.6.1.5, Risk Assessment and Risk Management per 10 CFR 50.65(a)(4)
The MR program includes procedures for maintenance risk assessment and management in accordance with 10 CFR 50.65(a)(4), employing the methods described in NUMARC 93-01, Section 11 (Reference 206). The risk from maintenance activities is both assessed (i.e., using a activities) risk-informed process to evaluate the overall contribution to risk of the planned maintenance and managed (i.e., providing plant personnel with proper awareness of the risk, and taking actions as appropriate to control the risk).
References:
206. Nuclear Management and Resources Council, Inc., Assessment of Risk Resulting from Performance of Maintenance Activities, NUMARC 93-01, Section 11, February 22, 2000.
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Shutdown Actions Mode Change Restrictions Example 1: Proposed Change to TS 3.5.3, CMT & TS 3.5.7, IRWST
[E] Required Action and associated Completion Time of Condition A, B, or D not met.
- E.1 Initiate action to be in MODE 5. with the RCS VENTED.
[Immediately]
AND E.2 Initiate action to restore required CMT to OPERABLE status.
[Immediately]
- TS 3.5.7 Applicability at all times in MODE 5
[F] Required Action and associated Completion Time of Condition A, B, C, D, or E not met.
OR LCO not met for reasons other than Condition A, B, C, D, or E.
- F.1 Initiate action to restore IRWST to OPERABLE status.
[Immediately]
establish 20% pressurizer level with the RCS pressure boundary intact.
AND F.2 Suspend positive reactivity additions.
[Immediately]
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Shutdown Actions Mode Change Restrictions Related Bases Changes to TS 3.5.3, ACTION E E.1 and E.2 If the Required Action or associated Completion Time of Conditions A, B, or D are not met action must be initiated, immediately, to place the plant in a MODE where this LCO does not apply. Action must be initiated, immediately, to place the plant in MODE 5 which minimizes the likelihood and consequences of an event. with RCS VENTED. In this condition, core cooling and RCS makeup are provided by IRWST injection and sump recirculation. With the RCS VENTED, actuation of ADS stage 4 sufficiently depressurizes the RCS to enable IRWST injection. In addition, action must be immediately initiated to restore the required CMT to OPERABLE status and to continue this action until restoration is accomplished in order to provide the CMT for the mitigation of postulated events.
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Shutdown Actions Mode Change Restrictions Related Bases Changes to TS 3.5.7, ACTION F F.1 and F.2 If the IRWST cannot be returned to OPERABLE status within the associated Completion Times of Condition A, B, C, D, or E, or the LCO is not met for reasons other than Conditions A, B, C, D, or E, action must be immediately initiated to restore the IRWST to OPERABLE status and to continue this action until restoration is accomplished in order to provide the IRWST for the mitigation of postulated events. In addition, the plant must be placed in a condition in which the probability and consequences of an event are minimized to the extent possible. This is done by immediately initiating action to place the plant in MODE 5 with the RCS intact with 20% pressurizer level. The time to RCS boiling is maximized by maintaining RCS inventory at 20% pressurizer level and maintaining RCS temperature as low as practical. With the RCS intact, the availability of the PRHR HX is maintained. Additionally, action to suspending positive reactivity additions is required to ensure that the SDM is maintained. Sources of positive reactivity addition include boron dilution, withdrawal of control rods, and excessive cooling of the RCS.
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Shutdown Actions Mode Change Restrictions Proposed Change to TS 3.3.8, ACTIONS, Conditions K (F14) & M (F18)
K[M]. As required by Required Action C.1 and referenced in Table 3.3.8-1.
K.1 - Suspend positive reactivity additions
[Immediately]
AND K.2 - Initiate action to restore channel(s) to OPERABLE status. open RCS pressure boundary and establish 20% pressurizer level.
[Immediately]
M.1 - Suspend positive reactivity additions
[Immediately]
AND M.2 - Be in MODE 5
[in 12 hour1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br />s]
AND M.3 - Initiate action to restore channel(s) to OPERABLE status. Establish a pressurizer level 20% with the RCS pressure boundary intact.
[in 12 hour1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br />s]
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Shutdown Actions Mode Change Restrictions Related Bases Changes to TS 3.3.8, ACTION K K.1 and K.2 If the Required Action and associated Completion Time of Condition A or B is not met or if three or more channels are inoperable, the plant must be placed in a condition in which likelihood and consequences of an event are the potential for a criticality event is minimized. This is accomplished by immediately suspending positive reactivity additions. Initiating action to open the RCS pressure boundary and establish 20% pressurizer level. Additionally, action is required to immediately initiate to restore the channel(s) to OPERABLE status to and to continue this action until restoration is accomplished in order to provide the necessary channels for the Function. suspend positive reactivity additions. These requirements minimize the consequences of the loss of decay heat removal by maximizing RCS inventory and maintaining RCS temperature as low as practical. Additionally, the potential for a criticality event is minimized by suspension of positive reactivity additions.
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Shutdown Actions Mode Change Restrictions Related Bases Changes to TS 3.3.8, ACTION M M.1, M.2, and M.3 If the Required Action and associated Completion Time of Condition A or B is not met or if three or more channels are inoperable, the plant must be placed in a condition in which the potential for a criticality event is minimized. This is accomplished by immediately suspending positive reactivity additions (Required Action M.1).
tThe plant must also be placed in a MODE in which the likelihood and consequences of an event are minimized. This is accomplished by placing the plant in MODE 5 within 12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br /> per Required Action M.2. The 12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br /> is a reasonable time to reach MODE 5 from MODE 4 with RCS cooling provided by the RNS (approximately 350°F) in an orderly manner without challenging plant systems.
Required Action M.3 requires initiation of action within 12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br /> to restore the channel(s) to OPERABLE status and to continue this action until restoration is accomplished in order to provide the necessary channels for the Function. close the RCS pressure boundary and establish 20% pressurizer level. The 12 hour1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br /> Completion Time is consistent with the allows transition to MODE 5 in accordance with Required Action M.2, if needed, while maintaining the RCS pressure boundary intact.
Required Action M.1 minimizes the potential for a criticality event by suspension of positive reactivity additions. Required Actions M.2 and M.3 minimize the consequences of a loss of decay heat removal event by optimizing conditions for RCS cooling in MODE 5 using the PRHR HX. Additionally, maximizing RCS inventory and maintaining RCS temperature as low as practical further minimize the consequences of a loss of decay heat removal event. Maintaining the RCS pressure boundary intact in MODE 5 assures that PRHR HX cooling is available.
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Shutdown Actions Mode Change Restrictions Schedule
- Target submittal 4th Qtr 2024
- Outage related Operational Improvement for 4R01, late 3rd Qtr 2025 18
Shutdown Actions Mode Change Restrictions Discussion / Feedback 19