ML100260702

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LGS RHRSW Allowed Outage Time Extension LAR Pre-Submittal Meeting Hand-outs
ML100260702
Person / Time
Site: Limerick  Constellation icon.png
Issue date: 01/26/2010
From:
Exelon Nuclear
To:
Office of Nuclear Reactor Regulation
Bamford, Peter J., NRR/DORL 415-2833
Shared Package
ml100260581 List:
References
Download: ML100260702 (16)
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Text

Exelon@

Nuclear EXELON/NRC MEETING LGS RHRSW PIPING REPAIRS/LAR u.s. Nuclear Regulatory Commission Tuesday, January 26, 2010

Exelon Nuclear Exelon/NRC Meeting RHRSW Piping Repairs/LAR

~ Introductions

~ RHRSW Piping Repairs

~ RH RSW AOT Extension LAR

~ Conclusion

Exelon ~

Nuclear

Introductions

v' Exelon Attendees

  • E. Hosterman - Limerick Design Engineering
  • G. Weiss - Plant Systems Engineering
  • D. Vanover - PRA (ERIN Engineering)
  • J. Quinn - Manager, Plant Engineering
  • D. Helker - Manager, Corporate Licensing
  • G. Stewart - Corporate Licensing

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Exelon Nuclear RHRSW System Piping Repairs

./ Background

  • Limerick has two independent RHRSW return lines common to both units
  • Existing common return piping is 30 inch diameter carbon steel pipe with some 20 inch diameter piping connecting to each unit
  • Existing piping contains weld overlay temporary repairs for minimum wall conditions (localized 10 corrosion)
  • Current LCO requires shutdown after 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br />
  • Work required for proactive pipe replacement cannot be completed in 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br />.

Exelon Nuclear RHRSW System Piping Repairs v' Scope of Repairs

  • The scope of repairs is to replace the degraded portions of accessible RHRSW return piping common to both units
  • "8" loop piping will be replaced during Unit 2 outages
  • "A" loop piping will be replaced during Unit 1 outages
  • Total replacement will require 2 - 3 outages per loop
  • Each outage scope will be based on the amount of work that can be completed within the proposed 7 day LCD.

Exelon ~

Nuclear RHRSW System Piping Repairs

./ Plant Configuration

  • Normal Configuration

- Each RHRSW return loop carries the total return flow of one RHRSW loop and one ESW loop .

- Both ESW loops have open connections to both RHRSW return loops

  • Planned configuration during repairs

- One unit in an outage; one unit operating

- One RHRSW return loop operable

- One RHRSW loop drained for repairs

- Both ESW loops aligned to return through operable RHRSW return loop o Valves to the operable loop will be locked open and de-energized o Valves to the drained loop will be locked closed and de-energized

Exelon Nuclear RHRSW AOT Extension LAR

~ Proposed Technical Specification Changes

~ Plant System Impact

~ Risk Impact

~ Potential Compensatory Measures

Exelon Nuclear RHRSW AOT Extension LAR

./ Proposed Technical Specification Changes

- 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> to 72 hour8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br />s**

- ** may be extended for a one-time period up to 7 days per calendar year for repairs of one RHRSW subsystem piping with opposite unit not in OPCONs 1, 2, or 3.

- 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> to 72 hour8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br />s**

- ** may be extended for a one-time period up to 7 days per calendar year for repairs of one RHRSW subsystem piping with opposite unit not in OPCONs 1, 2, or 3.

Exelon Nuclear RHRSW AOT Extension LAR V" Plant System Impact

- One loop drained and out of service

- Both units share the operable RHRSW return loop (2 RHRSW pumps and 4 ESW pumps)

- Both loops return to operable RHRSW loop

- Expected to meet required flows for all required components o Will be demonstrated by flow balance prior to initial alignment for each loop

- Single failure criteria

- Loss of backup to TECW on the outage unit (non-safety function) o TECW backup loop returns to RHRSW

Exelon Nuclear RHRSW AOT Extension LAR

../ Plant System Impact (continued)

- Reactor Water Cleanup and Fuel Pool Cooling will be able to handle outage unit decay heat

- One operable RHR heat exchanger per unit

- Fire protection compensatory measures may be required

Exelon Nuclear RHRSW LAR Risk Impact

~ CDF impact measured from internal events, internal floods, and internal fires

~ Bounding assessment performed for seismic impacts

~ Other external events screened based on likelihood of threat or limited role of RHRSW

~ LERF impact only measured from internal events and internal floods, but due to nature of RHRSW function, LERF acceptance guidelines not seriously challenged

Exelon Nuclear Preliminary Risk Results Figure of Merit Unit 1 Risk Unit 2 Risk Assessment Result Assessment Result

~CDF 1.0E-6/yr 9.9E-7/yr ICCDP 5.9E-7 6.7E-7 (RHRSW Loop A)

ICCDP 1.4E-6

1.2E-6 (RHRSW Loop B)

~ Results do not significantly exceed current acceptance guidelines for permanent changes

~ Results well within NUMARC 93-01 acceptance guidelines for voluntary maintenance activities requiring risk management actions

~ Compensatory measures ensure sources of risk are reduced

Exelon Nuclear Potential Compensatory Measur

../ Additional onsite staffing

../ ESW return valves administratively controlled

../ Opposite RHRSW train equipment protected

../ Elective maintenance on important risk contributors avoided

../ Adverse work in electrical switchyards prohibited

../ Operational risk activities restricted

../ Briefing with crew operators to reinforce potentially important operator actions .

../ Heightened awareness of key fire areas and pre-job walkdowns to reduce and manage transient combustibles in those areas

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