ML20207L316

Summary of 990224 Meeting with NEI & EPRI Re Mgt & Regulation of SG Degradation.List of Meeting Attendees, Agenda & Slides Presented During Meeting Encl

ML20207L316
Person / Time
Issue date:	03/15/1999
From:	Tim Reed NRC (Affiliation Not Assigned)
To:	Sullivan E NRC (Affiliation Not Assigned)
References
NUDOCS 9903180076
Download: ML20207L316 (16)

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WASHINGTON, D.C. 30086 0001 Mar'ch 15, 1999 j

MEMORANDUM TO: Edmund Sullivan, Acting Chief Materials and Chemical Engineering Branch Division of Engineering THRU:

Emmett Murphy, Acting Section Chief

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Section B Materials and Chemical Engineering Bran Division of Engineering FROM:

Timothy A. Reed, Senior Project Managh Materials and Chemical Engineering Bra Division of Engineering Office of Nuclear Reactor Regulation i

SUMMARY

OF THE FEBRUARY 24,1999 SENIOR MANAGEMENT MEETING WITH NUCLEAR INSTITUTE AND INDUSTRY TO DISCUSS STEAM GENERATOR ISSUES On February 24,1999, the NRC staff met with representatives of Nuclear Energy institute (NEl), Electric Power Research Institute (EPRI), and industry to discuss i.ssues regarding the management and regulation of steam generator (SG) degradation. Meeting attendees are identified in Attachment 1. The agenda and slides presented during the meeting are provided i

as Attachment 2.

- Brian Sheron (NRC) opened the meeting by discussing the objective of the staff's effort to resolve issues associated with the implementation of NEl 97-06 and revise the regulatory framework that govems SG tube integrity. Jack Strosnider (NRC) provided an overview of the February 10,1999 technical meeting with industry and characterized the progress that has been made since the previous senior level management meeting on this subject in November 1998. Mike Tuckman (Duke Power Company) led the discussion of the status of the key technical and regulatory framework issues (see slides in attachment 2). The NRC staff and Industry representatives agreed that there has been progress in resolving technical issues and that both sides have gained a substantially better understanding of each other's positions on the issues. In most cases, where the staff and industry are still not in agreement, the differences are minor. On a few issues, there is conceptual agreement, but neither the staff nor industry have yet to identify a practical regulatory instrument to implement the resolution (specifically this refers to removal of repair criteria and repair methods from the TS while still ensuring that first-of-a-kind proposals are reviewed and approved by the staff). Two issues (discussed below) where the staff and industry need additional interaction to resolve significant CONTACT: T. Reed, EMCB/DE 415-1462 9903190076 990315 PDR REV0P ERONUNRC PDR

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differences are the probabilistic structural criteria lasue (both the use of the criteria without prior NRC review and the criteria values) and the induced accident leakage issue (regarding

. proposed increases that satisfy licensing basis criteria but may increase risk).

The following key points were made during the meeting regarding the status of the technical and regulatory framework issues:

1. NEl's suggested use of " full power" in NEl 97-06: Industry noted that if the worst differential pressure (AP) condition (across the SG tube wall) that could exist during any normal or off-normal plant condition is used (in the 3 times normal operational AP calculation) instead of the normal operational AP, the resulting AP could be several hundred psid larger. This could create difficulties for some licensees. Industry indicated that they would develop a risk-informed justification for not util Hng such a worse case AP. The justification will address factors such as the power conditions that exist during such off-normal conditions (ex., reactor shutdown) and the short duration of the off-normal conditions. The staff indicated that it would review the justification for utilizing a reduced AP. The staff suggested an alternative approach the industry might wish to pursue. The staff noted that the definition of normal operating conditions in Regulatory Guide 1.121 and DG-1074 includes loads in service levels A und B as defined by the ASME Code and conservatively treats all these loads as service level A for purposes of determining the appropriate factors of safety. This is consistent with flaw evaluation methods in Section XI of the Code for austenitic stainless steel piping. The staff noted that it is entirely consistent with the Code to apply reducert safety f7 tors (as specified in the Code) to loads which can be properly categorized as servics leven C C.

2. Accident induced leakage: Industry management wanted a better understanding of the staff's concerns regarding increases in the value of accident-induced leakage assumed in the licensing basis dose assessment analyses. The staff indicated that although a proposed

. leakage increase could be shown to satisfy the applicable dose limits of GDC 19 and Part 100 (typically by reducing the reactor coolant sys,em iodine activity technical specification limit),

licensees could increase such accident leakages to relatively high values (hundreds of gallons per minute) which raises issues regarding the performance of the tube boundary during severe accident sequences (such as high pressure core melt sequences) and whether risk remains acceptable. Hence, the staff has concluded that licensees should utilize a risk-informed approach when considering such increases of accident-induced leakage. The staff indicated that it currently has an effort underway to look at the severe accident sequences in question using realistic assumptions for SG leakage, source terms, and event duration, to calculate realistic consequences and thereby develop a better technical basis for limiting accident-induced SG leakage to a value consistent with maintaining acceptable risk.

3. Definitions of tube burst and tube rupture: Industry management indicated that it did not fully understand the staff's concerns regarding this issue. Staff and ladustry noted that the definitions of burst and rupture have changed through the years, and have differed dependent on the application (ex. accident analyses, risk assessment, emergency operating procedures, abnormal operating procedures, RG 1.121, etc). The staff indicated, and industry agreed, that it is important that the staff and industry reach agreement on a definition for tube failure that both industry and the staff can utilize to determine whether the performance criteria are satisfied. The staff indicated that the definition needs to accommodate the two general types of approaches that can be used to assess degradation against the performance criteria: the analytical approach and the experimental approach (i.e., in situ pressure testing). The staff

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3 also noted that constructing a definition for incipient tube failure is much easier. than developing a definition for tube failure that leads to a defined value of tube leakage. Hence, the staff's suggested definition for tube failure in DG-1074 (which DG-1074 define's as tube " burst") is for incipient failure. Industry commented that we should be careful not to utilize terminology or new definitions that adversely impact other regulatory applications where rupture and burst terminology is utilized.

'4. Technical Specifications (TSs): Industry commented that there appears to be no "value added" to incorporating the structural and accident leakage performance criteria into the TSs, in part due to the view that the TSs are really an operator's document and these two performance criteria are not directly important from an operational control standpoint. Instead, industry believes that these performance criteria can be located in the updated final safety analysis report and that changes to the criteria can be controlled by 10 CFR 50.59. The staff stated its current conclusion that all three performance criteria should be in the TS to satisfy the requirements of 10 CFR 50.36 and thereby ensure that the SG TS adequately describes the lowest functional capability of the SG tubes including the capability of the SG tubes to function under design basis conditions. ' The staff discussed its view that this conclusion is consistent with the current SG TSs since the intent of the 40% depth-based repair criterion is to ensure ASME code structural margins are maintained for the entire operating cycle end to ensure that through-wallleakage does not occur (through the use of a minimum wall requiremont). Industry commented that the TSs incorporate a 1 GPM primary-to-secondary leakage limit that can be interpreted to mean that the TSs anticipated the potential for SG tube through-wall leakage and that therefore it was not the intent of current SG TSs to ensure no through-wall leakage occurs.

5. Tuba repair criteria and tube repair methods in TSs: The staff noted that it conceptually agrees with the industry proposal which calls for staff review and approval of "first-of-a-kind" tube repair criteria and tube repair method proposals. Under this proposal, licensees could thereafter apply approved approaches utiFzing 50.59 provided that such applications are within the constraints of the staff's safety evaluation. The current difficulty with this proposalis identifying a practical and timely regulatory vehicle to implement the approach. The staff indicated that the ASME Code is the best fit for facilitating such a process, but this involves a significant effort to either update the ASME Code or develop a Code case. Additionally, this approach requires that the staff process a regulatory action to either adopt the revised code version (via 10 CFR 50.55a) or to endorse the Code case through a regulatory guide. The result is likely to be a time and resource consuming process. The staff also indicated that to date, it had not identified an alternative approach utilizing TSs (i.e., one that does not involve a TS amendment for each and every licensee application of a previously approved repair criteria or method) that the NRC's Office of General Counsel (OGC) agrees with, but that it would continue to pursue this issue with OGC to identify any viable approaches utilizing TSs. Until a satisfactory alternative is devised, the staff indicated that it would keep repair criteria and repair methods in the TSs.

6. Risk issues associated with Probabilistic Structural Criteria: The staff discussed its risk concerns with the use of the probabilistic criteria. It was indicated that the probabilistic criteria relaxes the deterministic structural acceptance criteria from 3 AP (i.e., differential pressure between 3600 to 4200 psid) and/or 1.4 times the maximum differential pressure during accident conditions (i.e., differential pressure of approximately 3600 psid) to a AP of 2600 psid with a probability of meeting the criterion of 95% The impact of this relaxation on plant risk is an increased potential for tube wall failure under severe accident sequences, and hence a i

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~ potential increase in risk which should be considered to support the proposed use of the probabilistic structural criteria. Additionally, use of the probabilistic structural criteria can result in more severe degradation being left in service when compared to the use of the deterministic structural criteria, with the increased potential that such degradation can grow through-wall creating additional potential risk issues associated with leakage under severe accident conditions. The staff stated its conclusion that the probabilistic criteria is not in the licensing basis and that regardless of whether the probaollistic criteria is satisfied or not, the licensing basis is to maintain ASME section lit structural margins.

7. General risk issues: The NRC staff discussed the risk implications of managing SG tube degradation within the proposed performance-barsd framework, and emphasized the need for licensees to take effective corrective actions when performance criteria ars not met to avoid recurrence of such conditions. The staff indicated that risk is controlled adequately by limiting the time period when SG tube structural margins are degraded. The staff indicated that due to the relatively low frequency for the events of concern, the issue is not short, inadvertent periods of reduced margin, but rather continuous or continually recurring periods of reduced structural margins where risk becomes a concem (due to the increased time window when degraded conditions exist).

Industry senior management indicated, that given the current status of the efforts to gain agreement on a revised SG TS, and the fact that little additional flexibility is gained given the current need to continue to incorporate repair criteria and repair methods in the TSs, they were reconsidering whether the best option may not be to keep the current SG TSs rather than expand additional resources on the generic effort to revise SG TSs.

Industry and staff senior management tentatively agreed to meet again in May 1999.

Attachments: As stated DISTRIBUTION:

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PDR-I SCollins RZimmerman h3 OGC SMagruder EMCB RF File Center Document Name: G:\\REEDFEB2499.WPD To receive a copy of this documort, indicate in the box C= Copy w/o attachment / enclosure E= Copy with attachmenvenclosure N = No copy OFFICE DE:EMQ48 5

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potential increase in risk which should be considered to support the proposed use of the probabilistic structural criteria. Additionally, use of the probabilistic structural criteria can result in more severe degradation being left in service when compared to the use of the deterministic structural criteria, with the increased potential that such degradation can grow through-wall creating additional potential risk issues associated with leakage under severe accident conditions. The staff stated its conclusion that the probabilistic criteria is not in the licensing basis and that regardless of whether the probabilistic criteria is satisfied or not, the licensing basis is to maintain ASME section lli structural margins.

7. General risk issues: The NRC staff discussed the risk implications of managhg SG tube degradation within the proposed performance-based framework, and emphasized the need for licensees to take effective corrective actions when performance criteria are not met to avoid recurrence of such conditions. The staff indicated that risk is contro!!ed adequately by limiting the time period when SG tube structural margins are degraded. The staff indicated that due to the relatively low frequency for the events of concern, the issue is not short, inadvertent periods of reduced margin, but rather continuous or continually recurring periods of reduced structural margins where risk becomes a concern (due to the increased time window when degraded conditions exist).

Industry senior management indicated, that given the current status of the efforts to gain agreement on a revised SG TS, and the fact that little additional flexibility is gained given the current need to continue to incorporate repair criteria and repair methods in the TSs, they were reconsidering whether the best option may not be to keep the current SG TSs rather than expend additional resources on the generic effort to revise SG TSs.

Industry and staff senior management tentatively agreed to meet again in May 1999.

Attachments: As stated DISTRIBUTION:

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PUBLIC PDR 7

SCollins RZimmerman 3

OGC SMagruder EMCB RF File Center Document Name: G:\\ REED \\FEB2499.WPD To receive a copy of this document, indicate in the box C= Copy w/o attachment / enclosure E= Copy with attachment / enclosure N = No copy OFFICE DE:EMQd

!)E1@$8:(A)SC NAME Tree [ b hbhy DATE 3/k99 3/d99 OFFICIAL RECORD COPY 1C~3,990 y y!

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potentialincrease in risk which should be considered to support the proposed use of the probabilistic structural criteria. Additionally, use of the probabilistic structural criteria can result in more severe degradation being left in service when compared to the use of the deterministic structural criteria, with the increased potential that such degradation can grow through-wall creating additional potential risk issues associated with leakage under severe accident conditions. The staff stated its conclusion that the probabilistic criteria is not in the licensing basis and that regardless of whether the probabilistic criteria is satisfied or not, the licensing basis is to maintain ASME section lil structural margins.

7. General risk issues: The NRC staff discussed the risk implications of managing SG tube degradation within the proposed performance-based framework, and emphasized the need for licensees to take effective corrective actions when performance criteria are not met to avoid recurrence of such conditions. The staff indicated that risk is controlled adequately by limiting the time period when SG tube structural margins are degraded. The staff indicated that due to the relatively low frequency for the events of concem, the issue is not short, inadvertent periods of reduced margin, but rather continuous or continually recurring periods of reduced structural margins where risk becomes a concem (due to the increased time window when degraded conditions exist).

Industry senior management indicated, that given the current status of the efforts to gain agreement on a revised SG TS, and the fact that little additional flexibility is gained given the current need to continue to incorporate repair criteria and repair methods in the TSs, they were i sconsidering whether the best option may not be to keep the current SG TSs rather than expend additional resources on the generic effort to revise SG TSs.

Industry and staff senior management tentatively agreed to meet again in May 1999.

Attachments: As stated l

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NEl/EPRl/ INDUSTRY STEAM GENERATOR ISSUES SENIOR MANAGEMENT MEETING FEBRUARY 24,1999 LIST OF ATTENDEES NAME ORG/ POSITION

1. Tim Reed NRC/NRR/DE/EMCB

2. Jim Riley NEn

3. Jack Woodard Southern Nuclear

4. Mike Tuckman Duke Power

5. Dave Modeen NEl

6. Gary Holahan NRC/NRR/DSSA

7. Bill Bateman NRC/NRR

8. Brian Sheron NRC/NRR/ADT

9. Emmett Murphy NRC/NRR/DE/EMCB

10. Steve Long NRC/NRR/DSSA/SPSB

11. Greg Kammerdeiner Dusquesne Light

12. Rick Mullins Southern Nuclear

13. Ted Sullivan NRC/NRR/DE/EMCB

14. Noel Dudley ACRS

15. Phil Rush NRR/DE/EMCB

16. Michael Short Southern California Edison

17. David Stel! fox McGraw-Hill

18. Theresa Sutter Bechtel

19. Richard Pearson NSP

20. Ed Forest NUSIS

21. Jack Strosnider NRC/NRR/DE

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NRC/NEl/ industry February 24,1999 Management Meeting 4

j Implementation of NEl 97-06 e

introductory Remarks - S. Collins and M. Tuckman 1:00-1:15 pm l

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Progress on Technical issues - NRC/NEl 1:15-2:45 pm l

- Remaining open technicalissues

- Sub-group approach to issue resolution

- Regulatory framework issues i

- Application of risk e

Schedule for Future Interactions - NRC/NEl 2:45-3:00 pm ATTACHMENT 2

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= Operating assumptions used for 3-l delta P calculations

= Technicaljustification for accident induced leakage limit (1 gpm or 10CFR100/GDC 19}

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