ML20216D967

Provides Response to RAI to Support Proposed TS Change 460 Re Containment Isolation Valve Completion Time for SONGS, Units 2 & 3.Rev 3 to Abnormal Operating Instruction SO23-13-14, Reactor Coolant Leak, Encl

ML20216D967
Person / Time
Site:	San Onofre
Issue date:	07/29/1999
From:	Nunn D SOUTHERN CALIFORNIA EDISON CO.
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
Shared Package
ML20216D971	List: ML20216D967 ML20216D974
References
TAC-MA1549, TAC-MA1550, NUDOCS 9907300211
Download: ML20216D967 (12)

Text

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! SOUTHERN CAllIORNia l e[ EDISON ""*"=""

Vice President An LDISON INTERNATIONAL" Company l

July 29, 1999 l

l U. S. Nuclear Regulatory Commission Attention: Document Control Desk Washington D.C. 20555

Subject:

Docket Nos. 50-361 and 50-362 Response to Request for Additional Information to Support Proposed Technical Specification Number NPF-10/15-460, Containment isolation Valve Completion Time (TAC Nos. MA1549 and MA1550) San Onofre Nuclear Generating Station Units 2 and 3 l

References:

1) Letter from L. Raghavan (NRC) to Harold B. Ray (SCE), dated June 14,1999,

Subject:

Request for Additional Information Containment isolation Valve Completion Time Technical l Specification (TAC Nos. MA1549/1550), San Onofre Nuclear Generating Station, Units 2 and 3 l

2) Letter from Dwight E. Nunn (SCE) to the Document Control Desk (NRC), dated April 6,1998,

Subject:

Supplement 1 to Amendment Application Nos.158 and 142, Containment Isolation Valve

Completion Time, Se Onofre Nuclear Generating Station, Units 2 and 3 .

Gentlemen: l This letter provides additional information as requested by the NRC in Reference 1 to support the review of Southern California Edison's (SCE's) Amendment Application Nos.158 and 142', (Proposed Change Number 460), for San Onofre Units 2 and 3, respectively (Reference 2). The enclosure to this letter contains the requested i

information.

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3000_S5 ,

9907300211 990729 ( g DR ADOCK O gi P.O,Ikn 128 San Clemente. CA 92674 0128 949-368-l 480 Fax 949-368-1490 t

r if you have any questions or need additional information regarding this matter, please contact me or Mr. Jack Rainsberry at (949) 368-7420.

Sincerely,

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Enclosure cc: E. W. Merschoff, Regional Administrator, NRC Region IV J. A. Sloan, NRC Senior Resident inspector, San Onofre Units 2 and 3 L. Raghavan, NRC Project Manager, San Onofre Units 2 and 3 S. Y. Hsu, Department of Health Services, Radiological Health Branch State of California County of Sa Diego O h 1 / /1 0I '7 #1 - before me,

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personally appeared MC Ltd E- fj p p q , personally known to me to be the person whose name is subscribed to the within instrument and acknowledged to me that he executed the same in his authorized capacity, and that by his signature on the instrument the person, or the entity upon behalf of which the person acted, executed the instrument.

5 MARIANE SANCHEZ h

3 Commission #1196482 i WITNESS my hand and official seal. Notaryevore-camaw f

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Enclosure Responses to NRC's Request for Additional Information on Containment Isolation Valve Completion Time Technical Specification, Dated June 14,1999 l

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i NRC Question 1.

l Section C.2 of Regulatory Guide (RG) 1.177,"An Approach for Plant-Specific, Risk-Informed Decisionmaking: Technical Specifications," describes the specific aspects of the engineering evaluation to be conducted in support of a proposed change to a plant's TSs. In particular, the engineering evaluation under RG 1.177 includes compliance with current regulations (Section 2.1), traditional engineering considerations (Section 2.2), and evaluation of risk impact (Section 2.3). The traditional engineering considerations in Section 2.2 include a determin tion of whether the impact of the proposed TS change is consistent with the defense-in-depth philosophy. RG 1.177 summarizes specific elements as guidance for assessing defense in depth. Your submittal does not address the impact on the defense-in-depth philosophy of the proposed TS change, e g.,

(a) overall availability and reliability of the various alTected safety systems with the removal of numerous valves from service over the operating cycle, (h) maintenance of defenses against potential common-cause failures and its assessment of the potential for introduction of new cosamon-cause failure mechanisms, (c) potential degradation of the independence of physical barriers by the proposed TS change, and (d) maintenance of defenses against human errors such as those resulting from use of different personnel or performanie# constraints during plant operation.

Please provide your assessment and discussion how the proposed TS change meets the defense-in-depth principle, including your plans for implementing the proposed TS change.

Southern California Edison (SCE) Response Defense-in-Depth Principle The impact of the proposed Technical Specification (TS) change on defense-in-depth is addressed below. The discussion covers those topics specifically requested by the NRC as well as other topics discussed in Regulatory Guide (RG) 1.177 under defense-in-depth. Based on the following discussion, it is concluded that the proposed TS change meets the defense-in-depth principle.

(a) Overall availability and reliability of the various affected safety systems with the removal of numerous valves from service over the operating cycle:

1 This information was provided in the response to Question 2 of SCE's submittal dated March 22, l 1999 (Reference 1).  !

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In addition, a separate discussion topic related to defense-in-depth and availability / reliability of safety systems from RG 1.177 is addressed as follows:

System redwidancy, independence, and diversity are preserved commensurate with the expectedfrequency and consequences of challenges to the system (e.g., no risk outliers).

The proposed TS change does not affect system design redundancy, independence, or diversity. All the subject D.1 or D.2 containment isolation valves (with the exception of charging valve HV-9200) belong in systems with a high degree of redundancy and diversity. For example, the High Pressure Safety Injection (HPSI) and Low Pressure Safety Injection (LPSI) valves constitute eight and four redundant injection flow paths, respectively. Additionally, difTerent systems are designed to fulfill a safety function. For example, both the Containment Spray (CS) system and the Containment Emergency Cooling system provide containment cooling, and the CS system in the Reactor Coolant System (RCS) cold leg injection mode and the HPSI system provide high pressure RCS makeup during a Loss of Coolant Accident (LOCA). Hence, failure of a single D.1 or D.2 valve (i.e., secured closed) does not lead to the failure of the system in which the valve is installed. Failure of charging valve HV-9200 will result in failure of the charging system.

However, the plant can not operate long term with this valve closed and an alternate charging path not being established. Upon closure of the charging valve HV-9200, an alternate charging path will be established by the operators following Abnormal Operating Instruction (AOI) SO23-13-14 (see response to Question 2 below).

(b) Maintenance of defenses against potential common-cause failures and its assessment of the potential for introduction of new common-cause failure mechanisms.

l The proposed change does not affect the design of the plant, the type of planned  !

maintenance / testing, or the frequency of planned maintenance / testing on the subject containment isolation valves. The change does permit the required Motor Operated Valve Actuation Testing (MOVAT) of the valves to be performed on-line versus during shutdown. There is no data or basis to conclude that performing on-line maintenance on the subject containment isolation valves will introduce any new common cause failure mechanisms. Therefore, defenses against potential common-cause failures are preserved and the potential for introduction of new common-cause failure mechanisms has been assessed.

(c) Potential degradation of the independence of physical barriers by the proposed TS change.

The proposed change does not affect the design of the plant or the independence of fission product barriers. The change has no impact on the containment isolation barrier since both the current and proposed TS permit the subject containment isolation valves to be secured open when inoperable. Therefore, the independence of the barriers is not degraded.  !

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(b) Maintenance of defenses against human errors such as those resulting from use of l different personnel or performance constraints dur ng plant operation.

i As stated in our April 6,1998 submittal (Reference 2), performing on-line maintenance and MOVAT during non-outage petiods can be effectively scheduled using in-house personnel with no interference with usually very busy outage activities. This would reduce the potential for human errors. There is no data or basis to conclude that performing on-line maintenance on the subject containment isolation valves will increase the likelihood of human errors. Therefore, defenses against human errors are maintained.

Additional Defense-In-Depth discussion points:

Regulatory Guide 1.177 also addresses the following topics related to defense-in-depth:

A reasonable balance amongprevention oj core damage, prevesdion ofcontainmentfailure, and consequence mitigation ispreserved.

The proposed TS change preserves the existing balance between prevention of core damage, prevention of containment failure, and consequence mitigation by having a minimal impact on the likelihood ofcore damage, and having no impact on containment isolation failure. The change has no impact on containment isolation failure since both the current and proposed TS permit the subject containment isolation valves to be secured open when inoperable. The calculated increases in core damage frequency associated with the proposed TS change were shown to be small and within the acceptance criteria in Regulatory Guides 1.174 and 1.177. The proposed Allowed Outage Times (AOTs) for the D.1 and D.2 containment isolation valves are consistent with the AOTs for the systems in which the containment isolation valves are installed. Therefore, the impact of the proposed change in prevention of core damage is bounded by the current system AOTs.

Over-reliance on programmatic activities to compensatefor weaknesses in plant design is avoided.

The proposed TS change does not introduce or mitigate any weaknesses in plant design. The f purpose of the proposed TS change is to provide the capability to perform on-line MOVAT of the J subject containment isolation valves. There are no design weaknesses in the subject containment isolation valves or the systems in which they are installed. J The change does affect the likelihood that flow path redundancy is available by permitting the associated valves to be in a closed position longer than the current AOT. However, the proposed

- AOTs for the subject containment isolation valves are consistent with the AOTs for the )

4 Emergency Core Cooling System (ECCS) systems in which they are installed. Therefore, system redundancy is unaffected by the change.

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7he intent of the General Design Criteria in 10 CFR Part 50, Ajpendix A is maintained.

l The intent of the General Design Criteria (GDC) in 10CFR50, Appendix A is maintained because no change is proposed to the plant design and the Safety Analysis Report is not affected. The f

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proposed completion time allowance provides suflicient time to methodically perform on-line i maintenance (preventive and corrective) and surveillance activities (e.g., MOVAT). This enhances the quality ofmaintenance and MOVAT work and ultimately the reliability of the motor operated valves.

Implementation Plans The proposed risk-informed TS change will be implemented consistent with the San Onofre Umts 2 and 3 TS requirements and will be subject to the Configuration Risk Management Program (CRMP) as documented in plant procedure SO23-XV-50 NRC Question 2.

Your March 22,1999 letter (Table 2) indicates that removal of charging valve HV-9200 from service would result in the unavailability of the charging system. Please describe your proposed use of an abnormal operating instruction to establish an alternate charging path and acceptability of that approach with respect to current TS and license commitments. I SCE Response Charging valve HV-9200 is not removed from service for MOVAT or other testing during MODES 1 through 4. Because removal of charging valve HV-9200 from service renders both RCS baron injection flow paths required to be OPERABLE in accordance with TS 3.1.9 unavailable, entry into TS 3.0.3 is required. However, as stated in the Bases to TS 3.1.9, should the charging line inside containment become unavailable, the line may be isolated outside containment and flow redirected through the HPSI headers.

The method for aligning this alternate charging flow path is described in Abnormal Operating Instruction (AOI) SO23-13-14, " Reactor Coolant Leak," sections 3.3.2.1 and 3.3.2.3. A copy of the AOI is attached. As stated in the AOI, this method still requires entry into TS 3.0.3 due to l

" isolation of ECCS and Charging flow paths." Therefare, this alternate flowpath is only used during Abnormal conditions (i.e., a reactor coolant leak), not for routine maintenance or testing of valve HV-9200.

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NRC Question 3.

Please discuss how often you plan to use the proposed CIV completion time. To provide confidence in your risk evaluations and to provide for the possibility that you may use the proposed completion time more than once every six years, please provide a sensitivity calculation to determine the change in the core damage frequency for each of the CIVs using your proposed completion time once a year, not just once every six years.

SCE Response The D.1 and D.2 valve overhauls, including MOVAT, are performed once every 6 years (or not to exceed three refueling outages). The corrective maintenance activities are performed as needed.

As a sensitivity analysis, the frequency of entry into each of the Containment Isolation Valves (CIVs) extended AOT was assumed to be once a year, rather than once every six years. The out of service time was assun;ed to be either 3 days or 7 days consistent with the proposed TS change. The impact of this assumption on plant risk [i.e., change in Core Damage Frequency (ACDF), change in Large Early Release Frequency (ALERF), incremental Conditional Core Damage Probability (ICCDP) and Incremental Conditional Large Early Release Probability (ICLERP)] is summarized in Table 1 below. It is observed that the change in risk (i.e., ICCDP and ICLERP) for all the configurations are well below the Regulatory Guide 1.177 acceptance criteria of 5.0E-7 for ICCDP and 5.0E-8 for ICLERP, with the assumption of once a year entry into each of the CIVs extended AOT.

These calculations are made by using the latest San Onofre Nuclear Generating Station (SONGS) living Probabilistic Risk Analysis (PRA) model as implemented by the plant Safety Monitor.

These values represent risks stemming from both internal and external events (i.e., seismic and fire) when the plant is at full power. These values do not include shutdown risk since the affected TS 3.6.3 does not apply during MODES 5 and 6.  ;

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The risk increase due to once a year entry into the proposed AOT extension (i.e., once a year for every D.1 and D.2 valve) are calculated as follows using the ICCDP and ICLERP estimates for single valves in Table 1:

Annual cumulative ICCDP = (8 x 1.9E-8) + (2 x 8.2E-10) + 8.2E-10 + (8 x 8.2E-10) +

(4 x 1.1E-8) = 2.lE-7 Annual cumulative ICLERP = (8 x 2.0E-11) + (2 x 8.0E-12) + 8.2E-12 + (8 x 8.0E-12) +

(4 x 8.0E-12) = 2.8E-10  ;

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Table 1 impact of Proposed TS Change on Plant Risk, ACDF, ALERF,ICCDP and ICLERP (Sensitivity Analysis: Using Extended AOT Once a Year for Each CIV)

Valve ID Change Change Proposed incremental Incremental in CDF in L.ERF AOT(or CT) Conditional Conditional (ACDF (ALERF (Based on CD LER

/yr) /yr) Current Probability Probability System (ICCDP) (ICLERP)

AOT)

Containment Air Cooler Cooling Water 1.0E-6 < l .0E-9 7 days 1.9E-8 <2E-11 Valves (8)(HV-6367 (cutoff through HV-6373) value)

Containment Spray Valves (2)(liv-9367 1.0E-7 < l.0E-9 3 days 8.2E-10 <8E-12 and HV-9368)

Containment Pressure Detector Valves (4) Negligible Negligible No system Negligible Negligible (HV-0352A through AOT HV-0352D) proposed (a)

Charging Valve (1) 1.0E-7 1.0E-9 3 days 8.2E 10 8.2E-12 (HV-9200)

High Pressure Safety injection Valves (8) 1.0E-7 < l.0E-9 3 days 8.2E-10 <8E-12 (HV-9323 HV-9324, HV-9326. HV-9327, HV-9329, HV-9330, HV-9332, and HV-9333 Low Pressure Safety Injection Valves (4) 1.3E-6 < l.0E-9 3 days 1. lE-8 <8E-12 (HV 9322, HV-9325,

! HV-9328, and HV-9331) l 1

(a) No current system AOT cxists.

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The sensitivity analysis results show that the annual cumulative increase in risk due to multiple applications of the proposed AOT extension (i.e., once a year for every D.1 and D.2 valve)is very small and meets the acceptance criteria set forth in Regulatory Guide 1.177.

NRC Question 4.

Please state whether the CIVs in your proposal are covered by your Maintenance Rule program? What are the performance criteria for each of these salves? Please describe the appropriateness of these criteria.

SCE Response All of the CIVs in the scope of the proposal are covered by the SONGS Maintenance Rule Program as part of the Containment Isolation System. Specifically, all of the valves are included under function MR-CIS-01:

" Isolate all the containment penetrations not required for accident mitigation and not to leak more than is set forth in the Technical Specifications or Appendix J."

The Maintenance Rule performance criteria for the Containment Isolation system were previously submitted to the NRC on January 2,1998 (Reference 3) in the response to the NRC

" Maintenance Rule Inspection Supplemental Information." The NRC Maintenance Rule Baseline inspection team reviewed the current performance criteria and determined that they were appropriate in letter EA 98-035 from A. Howell,11I to H.13. Ray, dated March 2,1998, "NRC I Inspection Report 50-361/97-22; 50-362/97-22 and Notice of Violation"(Reference 4). The ,

pe:formance criteria have not changed from those previously submitted. However, both the type and numeric value of the performance criteria are subject to change under the provisions of the Maintenance Rule Program.

The current criteria are appropriate as they address several aspects of the containment isolation function including total leakage, Appendix J valve leakage test failures, cumulative unavailability of ali Cl valves, random valve closure failures, and repetitive failures. Failing to meet any of the criteria will cause the Containment Isolation system to be placed in paragraph (a)(1) goal setting. i l

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NRC Question 5.

With respect to your proposed on-line maintenance and testing of multiple components during power operation, please describe the methodology for taking out components from various ECCS such that the ECCS requirements for design basis accidents will be unalTected.

SCE Response i

The San Onofre Units 2 and 3 ECCS TSs (i.e., TS 3.5.2) will ensure that the ECCS requirements for design basis accidents are unafrected when components from various ECCS trains are taken out of service.

The subject D.1 and D.2 valves in TS 3.6.3," Containment Isolation Valves," proside both containment isolation and Engineered Safety Feature Actuation Signal (ESFAS) functions. These valves are opened for their ESFAS function and closed for their containment isolation function.

Because of this dual function, the appropriate TSs for each function are entered simultaneously when a valve becomes inoperable. ECCS TS 3.5.2 permits a 3-day AOT (7 days for LPSI) for inoperable D.1 and D.2 valves. TS 3.6.3 currently requires that these valves be secured in their ESFAS actuated position (i.e., secured open) within 4 hours4.62963e-5 days <br />0.00111 hours <br />6.613757e-6 weeks <br />1.522e-6 months <br /> afler becoming inoperable. In such a case where more than one TS action simultaneously applies, the more restrictive action is followed, i.e., the 4-hour AOT. Once the valve is secured in its ESFAS position, the ECCS TS 3.5.2 Action Statement is exited. The April 6,1998 submittal requests an extension of the 4 hours4.62963e-5 days <br />0.00111 hours <br />6.613757e-6 weeks <br />1.522e-6 months <br /> AOT to 3 days or 7 days for the ECCS D.1 and D.2 valves consistent with the ECCS TS.

Hence, by entering TS 3.5.2 the ECCS requirements for design basis accidents will be met.

References:

1) Letter from A. E. Scherer (SCE) to Document Control Desk (NRC), dated March 22,1999,

Subject:

Response to the NRC Request for Additional Information to Suppon Proposed Techr."al Specification Number NPF-10/15-460, Containment Isolation Valve Completion Time (TAC Nos.

MA1549 and MA1550), San Onofre Nuclear Generating Station, Units 2 and 3.

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2) Letter from D. E. Nunn (SCE) to Document Control Desk (NRC) dated April 6,1998,

Subject:

Docket Nos. 50-361 and 50-362, Supplement I to Amendment Application Numbers 158 and 142, Containment Isolation Valves Completion Time, San Onofre Nuclear Generating Station, Units 2 and 3.

3) Letter from D. E. Nunn (SCE) to Document Control Desk (NRC) dated January 2,1998,

Subject:

Docket Nos. 50-361 and 50-362, Maintenance Rule Inspection Supplemental Information, San Onofre Nuclear Generating Station, Units 2 and 3.

4) Letter from A. T. Howell III (NRC) to H. B. Ray (SCE), dated March 2, 1998,

Subject:

NRC Inspection Report 50-361/97-22; 50-362/97-22, and Notice of Violation.

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