ML23206A041
| ML23206A041 | |
| Person / Time | |
|---|---|
| Site: | Hatch  |
| Issue date: | 08/02/2023 |
| From: | Southern Nuclear Operating Co |
| To: | Dawnmathews Kalathiveettil NRC/NRR/DORL/LPL2-1 |
| Kalathiveettil, D | |
| References | |
| EPID L-2023-LRM-0046 | |
| Download: ML23206A041 (1) | |
Text
Edwin I. Hatch Nuclear Plant Request for Limited Extension of Risk Informed Completion Time (RICT) Program Backstop
Agenda 2
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Agenda
Purpose:
Engage NRC Staff on Southern Nuclears proposed change to extend the Risk Informed Completion Time (RICT) backstop for select residual heat removal service water (RHRSW) and plant service water (PSW) Technical Specification (TS)
Required Actions (A.1 - one pump inoperable)
- System Design
- Current TS Requirements
- Brief History
- Requested Changes
- Approach
- Questions 3
System Design
4
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System Design - RHRSW
- Two independent subsystems
- Each subsystem has a suction source (river), two 50% (i.e., 4000 gpm) capacity pumps, header, valves, piping, and heat exchanger
- Pump approximately 12,000 lbs / 61 ft long; Motor approximately 7,600 lbs / 6 ft long
- Safety analyses assume RHRSW supports cooling of the suppression pool following a loss of coolant accident (LOCA)
- Safety analyses assume that, with one subsystem with two pumps operating at 3750 gpm each and up to 5% of tubes plugged in RHR heat exchanger, the suppression pool temperature and primary containment pressure are limited 211.6°F (design 281°F) and 27.8 psig (maximum allowable 62 psig), respectively
- PRA Success Criteria is one pump at 4000 gpm and one heat exchanger
[ML21300A153]
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System Design - PSW
- Two independent subsystems
- Each subsystem has a suction source (river), two 8500 gpm capacity pumps, header, valves, piping, and heat exchanger
- Three pumps required for normal operation; one pump required for safety analysis
- Pump approximately 12,000 lbs / 61 ft long; Motor approximately 7,600 lbs / 6 ft long
- Safety analyses assume system supplies cooling to safety equipment during emergency conditions
- The diesel generators and the longterm cooling capability of the RHR, core spray, and RHR service water pumps depend on the cooling provided by the PSW system. Either subsystem can provide adequate cooling with only one pump providing flow.
- PRA Success Criteria: one pump at 2400 gpm and ultimate heat sink
[ML21300A153]
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Plant service water pump 7
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RHRSW 8
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PSW 9
Current TS Requirements 10
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Current TS Requirements 11
Reason for Change 12
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Reason for Change
- Pump replacement typically 710 days but:
- Replacement pump fails preservice test
- Need divers to inspect suction area [+1 day]
- Replace with 2nd replacement pump [+7 to 10 days]
- Additional discoveries made during pump replacement [+11 days]
- Problem during postmaintenance test requiring offsite motor refurbish [+7 to 10 days]
- Preventive maintenance (PM) to replace a pump motor is 45 days but:
- Motor / pump alignment issue [+1 day]
- Replacement pump motor requires offsite services and reinstall [+16 days]
- Difficulties aligning discharge head with discharge check valve flange [+10 days]
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Reason for Change November 2019 Unit 1 RHRSW pump B was replaced and then failed during pre-service testing. SNC replaced that pump with another new pump, which also failed during pre-service testing. SNC submitted an emergency license amendment request a to allow a one-time extension to the TS 3.7.1 Required Action A.1 Completion Time from 30 days to 45 days. The license amendment request was withdrawn b after the pump was restored to operable status less than 3 days prior to the original 30-day Completion Time.
September 2021 Challenges encountered during repair and replacement activities to restore operability to Unit 1 PSW pump C led to the need for an emergency license amendment request c (and RAI response d). The approved emergency license amendment e allowed, with compensatory measures established, a one-time extension of the TS 3.7.2 Required Action A.1 Completion Time from 30 days to 45 days.
April 2022 Challenges encountered during repair and replacement activities to restore operability to Unit 1 PSW pump A led to SNC submitting an emergency license amendment request f to, with compensatory measures established, extend the TS 3.7.2 Required Action A.1 Completion Time from 30 days to 45 days. The license amendment request was withdrawn g after HNP personnel restored the pump to operable condition less than 48 hours5.555556e-4 days <br />0.0133 hours <br />7.936508e-5 weeks <br />1.8264e-5 months <br /> prior to the 30-day Completion Time.
- a. ML19333B967 b. ML19336B596 c. ML21264A003 d. ML21266A004 e. ML21264A644 f. ML22120A087 g. ML22123A159 14
Requested Changes 15
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Requested Changes 16
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Requested Changes 17
Approach 18
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Approach - Justification (Technical / Risk Basis)
- The current 30day RICT backstop is administrative limit
>> Proposed extension is limited to CTs where need has been demonstrated (TS 3.7.1 and TS 3.7.2 RA A.1)
- The RICT program provides assurance that the plant is maintained at an acceptable risk level:
>> Configurationspecific Completion Times (will not automatically get 45 days)
>> Risk Management Actions
>> RICT Budget and SNC procedures encourage staying within the front stop when possible
- Safety analysis requires:
>> One PSW pump required to supply for safe shutdown, including RHR shutdown cooling system requirements
>> Two RHRSW pumps required to provide adequate heat removal capacity following a design basis LOCA.
- Would preclude need for an emergency amendment maintain plant focus on restoring operability
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Approach - Justification (Precedence)
- Completion Times greater than 30 days are not uncommon
>> Some Plant Technical Specifications Examples:
- Hatch Unit 1 and Unit 2 TS 3.7.4 Main Control Room Environmental Control (MCREC) System Required Action B.3 has a 90day completion time.
- Limerick Unit 1 and Unit 2 TS 3.7.1.2 Emergency Service Water System - Common System Action a.1 allows 45 days to restore operability when one pump is inoperable.
- Vogtle Units 1 and 2 TS 3.7.9 Ultimate Heat Sink (UHS) Required Action D.2 (restore operability to transfer pump) has a 46day Completion Time.
- LaSalle Units 1 and 2 TS 3.7.3 Ultimate Heat Sink (UHS) Required Action A.1 (restore operability to core standby cooling system pond) has a 90day Completion Time.
- Consistent with NUREG1433, Current Hatch TS 3.7.1 and TS 3.7.2 allow calculation of a RICT for one pump inoperable in each subsystem
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Approach Format
- Submittal will follow postTSTF505 Adoption [ML20324A070] and NEI 0602
- Attachments to be provided:
- 1. Description and Assessment
- 2. Proposed Technical Specification Changes (MarkUp)
- 3. Proposed Technical Specification Changes (CleanTyped)
- 4. Proposed Technical Specification Bases Changes (MarkUp) - For Information Only
- Enclosures intended to be provided:
- 1. List of Required Actions to Corresponding PRA Functions
- 2. Information Supporting Consistency with Regulatory Guide 1.200, Revision 2
- 4. Information Supporting Justification of Excluding Sources of Risk Not Addressed by the PRA Models
- 9. Key Assumptions and Sources of Uncertainty
- 12. Risk Management Action Examples
- Enclosures not intended to be provided:
- 3. Information Supporting Technical Adequacy of PRA Models Without PRA Standards Endorsed by Regulatory Guide 1.200, Revision 2
- 6. Justification of Application of AtPower PRA Modes to Shutdown Modes
- 7. PRA Model Update Process
- 8. Attributes of the RealTime Model
- 10. Program Implementation
- 11. Monitoring Program
Questions 22