ML19143A472

Presentation Material for 6/03/19 Pre-Submittal Meeting Integrated Leak Rate Test Extension License Amendment Request

ML19143A472
Person / Time
Site:	Millstone
Issue date:	06/03/2019
From:	Dominion Energy Nuclear Connecticut
To:	Plant Licensing Branch 1
Guzman R
References
EPID L-2019-LRM-0026
Download: ML19143A472 (15)

Text

Millstone Power Station Unit 3 Pre-Submittal Teleconference for License Amendment Request to Extend Containment Leakage Testing Intervals 1 June 3, 2019

Agenda

• Background and Reason for Amendment

• Proposed Changes

• Technical Justification for Changes

• Conclusions

• Schedule

• Acronyms 2 June 3, 2019

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Background===

• 10 CFR 50, Appendix J was amended after the initial licensing of MPS3 to provide a performancebased approach (Option B) for the containment leakage testing requirements ILRT (Type A) and local leak rate testing.

Performancebased test intervals are based on consideration of the operating history of the component and resulting risk from its failure.

• NEI Topical Report 9401 provided a guideline to the industry for implementing the performancebased Option B.

NRCs SEs for NEI 9401 Revision 2A and 3A concluded that Licensees could implement this optional approach as described in the documents, subject to the limitations and conditions of the SEs.

3 June 3, 2019

Proposed Changes

• DENC proposes a LAR for MPS3, which will revise TS 6.8.4.f, "Containment Leakage Rate Testing Program to:

Replace the reference to RG 1.163 with a reference to NEI 9401, Revision 3A.

Include additional wording to impose the limitations and conditions specified in NEI 9401, Revision 2A.

• These changes would allow DENC to extend the Type A (ILRT) interval from 10 years to 15 years and the Type C local leak rate test interval from 60 months to 75 months for MPS3.

4 June 3, 2019

Technical Justification for Changes Testing History and Inspections

• A review of the last 3 Containment Leak Rate Test program results indicate that measured leak rates meet the applicable TS limits and/or Appendix J criterion with margin.

Only exception was during the 1998 asfound Type A test, when failures resulted from a containment purge supply issue (LER 96 01200)

• Containment inspections performed in accordance with other plant programs serve to provide a high degree of assurance that the containment will not degrade in a manner that would challenge containment integrity.

Based on the latest ASME XI Subsection IWE/IWL containment inspections performed at MPS3, there are no active degradation mechanisms present.

5 June 3, 2019

Technical Justification for Changes MPS3 PRA Background

• DENC prepared a confirmatory risk impact assessment in accordance with the methodology described in EPRI Report No.

1009325, Revision 2 for ILRT Extensions.

• The assessment confirmed the general findings of NUREG1493 (PerformanceBased Containment LeakTest Program) on a plant specific basis, considering severe accidents for MPS3.

Increasing the ILRT interval to fifteen years is considered to be an insignificant change in risk since it represents a small change to the MPS3 risk profile.

6 June 3, 2019

Technical Justification for Changes MPS3 PRA Scope

• The scope of the MPS3 PRA model includes Internal Event and Internal Flood Hazards.

• In this LAR, Fire and Seismic Hazards will be assessed using a bounding analysis, considering IPEEE information.

• Other External Hazards will be assessed qualitatively.

7 June 3, 2019

Technical Justification for Changes MPS3 PRA Quality

• In the SE (ADAMS Accession No. ML081140105) for EPRI Report 1009325 and NEI 9401 Revision 2 the NRC stated, in part:

the NRC staff will expect the licensees supporting Level 1/LERF PRA to address the technical adequacy requirements of RG 1.200, Revision 1. Capability category I of ASME RASa2003 shall be applied as the standard, since approximate values of CDF and LERF and their distribution among release categories are sufficient for use in the EPRI methodology.

8 June 3, 2019

Technical Justification for Changes MPS3 PRA Quality

• DENC recently contracted with Westinghouse to perform a focusedscope peer review of the MPS3 PRA to determine compliance with Addendum A of the ASME/ANS PRA Standard and RG 1.200, Revision 2.

• This review, when combined with a previous focused scope peer review, resulted in a complete review of the MPS3 Internal Event and Internal Flood PRA model against the full scope of ASME/ANS RASa2009/RG 1.200 R2 technical requirements.

9 June 3, 2019

Technical Justification for Changes MPS3 PRA Quality

• The MPS3 PRA model has 106 F&Os of Finding significance.

All findings have been assessed and dispositioned for this application.

The LAR includes a table which discusses the disposition for each finding. The table uses a template from 10 CFR 50.69 riskinformed categorization license amendments.

10 June 3, 2019

Technical Justification for Changes MPS3 PRA Quality

• Each finding was dispositioned using one of the following techniques:

Qualitative assessment Incorporation into a quantitative sensitivity analysis which assessed the cumulative impact of PRA findings, uncertainties and pending changes 11 June 3, 2019

Technical Justification for Changes

• The PRA model (including 106 findings) is acceptable for ILRT surveillance application with the following basis:

The ILRT risk assessment methodology employs a number of simplifying assumptions which apply conservative bias to the evaluation. Per the NRC SE for EPRI Report 1009325:

approximate values of CDF and LERF and their distribution among release categories are sufficient for use in the EPRI methodology.

The subject of the findings do not adversely impact the ability of the MPS3 model to support this application. Per the Westinghouse Peer Review Report:

The findings and suggestions primarily pertain to modeling details and to the clarity and completeness of documentation. Overall, the MPS3 PRA was found to substantially meet the ASME/ANS PRA Standard, RASa2009 at Capability Category II The sensitivity analysis demonstrates that the ILRT risk analysis has very low sensitivity to the cumulative impact of Peer Review findings.

12 June 3, 2019

Conclusions

• DENC is adopting the guidance of NEI 9401, Revision 3A, and the limitations and conditions specified in NEI 9401, Rev. 2A, for use in the MPS3 10 CFR 50, Appendix J testing program.

• Based on the previous ILRT tests conducted at MPS3, DENC concludes that extension of the containment Type A (ILRT) interval from 10 to 15 years and the Type C local leak rate test from 60 months to 75 months represent minimal risks to increased leakage.

• The findings of the MPS3 risk assessment confirm, on a plant specific basis, that extending the Type A (ILRT) interval from 10 to 15 years results in a small change to the MPS3 risk profile.

13 June 3, 2019

Schedule

• NRC PreSubmittal Meeting on 06/03/2019

• Site Facility Safety Review Committee Review targeted for end of June 2019

• LAR Submittal to the NRC expected by end of July 2019

• NRC Approval requested by end of July 2020 14 June 3, 2019

Acronyms ANS American Nuclear Society LERF Large Early Release Frequency ASME American Society of Mechanical MPS3 Millstone Power Station Unit 3 Engineers NEI Nuclear Energy Institute CDF Core Damage Frequency NRC Nuclear Regulatory Commission CFR Code of Federal Regulations PRA Probabilistic Risk Assessment DENC Dominion Energy Nuclear RG Regulatory Guide Connecticut SE Safety Evaluation EPRI Electric Power Research TS Technical Specifications Institute F&O Finding & Observation IPEEE Individual Plant Examination of External Events ILRT Integrated Leak Rate Testing LAR Licensing Amendment Request 15 June 3, 2019