ML20207C605

Summary of 990506 Meeting with Nei,Epri & Industry Re Technical Issues Involving Implementation of NEI-97-06 Steam Generator Program Guidelines. List of Attendees & Meeting Handouts & Agenda Encl

ML20207C605
Person / Time
Issue date:	05/25/1999
From:	Tim Reed NRC (Affiliation Not Assigned)
To:	Bateman W NRC (Affiliation Not Assigned)
References
NUDOCS 9906030071
Download: ML20207C605 (44)

Text

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UNITED STATES j

g NUCLEAR REGULATORY COMMISSION WASHINGTON, D.C. 30006 4 001 May 25, 1999 1

l-L MEMORANDUM TO: William H. Bateman, Chief L

Materials and Chemical Engineering Branch -

L Division of Engineering THRU:

Edmund J. Sullivan, Chief p

NDE & Metallurgy Section L)

Materials and Chemical Engineering Branch Division of Engineering

. FROM:

Timothy A. Reed, Senior Project Manager NDE & Metallurgy Section

. Materials and Chemics L1gineering Branc j

Division of Engineering

SUMMARY

OF THE MAY 6,1999, TECHNICAL MEETING WITH l

NEl/EPRl/ INDUSTRY TO DISCUSS ISSUES INVOLVING IMPLEMENTATION OF NEl 97-06 On May 6,1999, the NRC staff met with representatives of Nuclear Energy Institute (NEI),

Electric Power Research Institute (EPRI), and industry to discuss technical issues involving the implementation of NEl 97-06 " Steam Generator Program Guidelines." Meeting attendees are identified in Attachment 1. The meeting handouts and agenda are provided as Attachment 2.

< The meeting discussion focused on three principle technical areas: 1) regulatory framework issues,2) technical issues, and 3) risk issues.

- Regarding each of these topics, the following key points were made during the meeting:

1. Steam Generator (SG) Technical Specifications (TS)

Industry provided a revised SG TS that was based on the staff's version provided to industry at the April 1,1999 technical meetin' The revised SG TS moves the performance criteria i

from the TS to a technical requireme is manual (TRM) which is maintained as part of the updated final safety analysis sport (, FSAR). The industry proposal incorporates a set of contingency measures and definitiono into the TRM. A key point of discussion involved

' whether proposed changes to the performance criteria would be govemed by 10 CFR

. 50.59. Both industry and the staff agreed that such proposed changes would require prior staff review and approval under either the current 10 CFR 50.59 or the proposed 50.59, and in addition, the staff commented that there needs to be a commitment on the part of licensees to maintain the TRM as part of the UFSAR. The industry proposed SG TS revised the reporting requirements from that previously proposed by the staff. The staff j

commented that the SG TS reporting requirements should be more consistent with the guidance contained in NEl 97-06. The staff also suggested that NEl 97-06 should be revised to incorporate guidance on the content of the special report which the the industry j

SG TS proposal would require to be provided to the staff following failure to maintain burst

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2. First Time Approval t

The staff discussed a list of constraints that the staff would be consider for incorporation into the safety evaluation (SE) approving first-of-a-kind proposals, and which thereby limit the applicability of approved approaches (i.e., new repair criteria, new repair methods, and altamative performance criteria) to other licensees. The staff indicated that the challenge would be to ensure the staff's SE contains only the necessary limitations for application of -

approved approaches at other facilities. The staff indicated that the best available example of this type of approach is GL 95-05 which provides a list of constraints on application of the voltage-based repair criteria (e.g., Westinghouse SGs with drilled-hole tube support plates, l

axially-oriented, outside diameter _ stress corrosion cracking, etc). An additional challenge would be to identify constraints that stem from risk considerations. The staff indicated that it i

would review first time approvals with a focus on whether the proposal presents potential I

risk issues. The staff encouraged the industry to submit risk-informed submittals to help facilitate this type of review rather than have the staff generate the information independently.

3. Grandfathering of Currently Approved Approaches l.

The staff indicated that the objective for grandfathering previously approved repair criteria and repair methods is to transition from the current SG TSs to the new framework with as little impact as possible. On a plant-specific basis, the process shoulo simply be a relocation of approved repair criteria and repair methods from the TS to the TRM. The staff would not re-open previous approvals with questions regarding risk or other technical areas even for situations where there has been inconsistency in previous approvals between licensees. A more difficult issue is developing an approach for enabling licensees to adopt

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previously approved repair criteria and repair methods (e.g., F* or laser welded sleeves).

The problem stems from the fact that these previous approvals were not written (i.e., SE l

was plant specific) with the "first time" approval objective in mind, and as such, the supporting SE does not contain a list of constraints limiting application of the approved approach to other facilities. The staff commented that it is the objective to make these previous approvals available to other licensees, and that this may require the staff to establish the constraints for some previously approved approaches in its SE on the I

industry's generic TS proposal.

4. Three T:mes Normal Operational AP The NRC staff discussed its conclusions regarding the issue of what differential pressure (AP) should be used in the three times normal operation AP calculation. The staff concluded that the industry proposal to utilize the nominal full power AP appears to be acceptable, but requested that industry provide additional information (discussed in slides 7 and 8 of staff slides entitled " Structural Performance Criteria") to support the staff's review l

of the issue and its subsequent discussions with CRGR. The staff also suggested that L

industry should revise the NEl 97-06 document to cordain additional guidance with regard to the issue of secondary stresses (see slide 10).-

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3. Definition of Burst and Rupture industry provided a revised definition of tube burst in which " burst" is defined as a gross

- structural failure of the tube wall.: Industry believes this revised definition is consistent with the ASME Code, consistent with laboratory data, measurable, and consistent with the staff's definition in DG-1074. The staff indicated that it would consider the industry's proposed I

definition.

5. Nondestructive Examination (NDE) Uncertainties Industry considers the issue of NDE qualification and uncertainty to be closed based on the information provided in the handout (see attached slides). The staff indicated that it was not aware of any obstacles involving the NDE issue that would preclude the staff from reviewing and potentially approving a generic industry SG TS submittal. However, the staff also indicated that there is fixely to be continued discussions on this issue in the future, either in response to he staff's review of new repair criteria proposals, or as a result of a licensee failing to meet performance criteria.

6. Risk issues The staff discussed the status of the policy regarding the consideration of risk for new SG proposals. The staff encouraged the industry to submit risk-informed proposals consistent with the guidance of RG 1.174 since the licensee is in the best position in terms of available information and PRA models to address the risk considerations of a SG proposal for their facility. Regarding the extent to which the staff can consider risk, and potentially impose I

rastrictions that stem from risk considerations, on licensee submittals that are not risk-informed, the staff indicated that the policy is still not defined.

Three generalissues were identified for discussion at the upcoming SG senior management meeting: status of the SG TS, consideration of risk / severe accidents, and grandfathering of previously approved repair criteria and repair methods. The industry and staff tentatively agreed to hold the next technical meeting on June 17,1999.

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_ di Definition of Burst and Rupture l.

i Industry provided a revised definition of tube burst in which " burst"is defined as a gross

. structural failure of the tube wall industry believes this revised definition is consistent with

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' the ASME Code, consistent with laboratory data, measurable, and consistent with the staff's definition in DG-1074. The staff indicated that it would consider the industry's proposed definition.

l

5. Nondestructive Examination (NDE) Uncertainties industry considers the issue of NDE qualification and uncertainty to be closed based on the information provided in the handout (see attached slides). The staff indicated that it was not aware of any obstacles invoMng the NDE issue that would preclude the staff from reviewing 1

. and potentially approving a generic industry SG TS submittal. However, the staff also indicated that there is likely to be continued discussions on this issue in the future, either in response to the staff's review of new repair criteria proposals, or as a result of a licensee failing to meet performance criteria.

6. Risk issues The staff discussed the status of the policy regarding the consideration of risk for new SG proposals. The staff encouraged the industry to submit risk-informed proposals consistent with the guidance of RG 1.174 since the licensee is in the best position in terms of available

'information and PRA models to address the risk considerations of a SG proposal for their facility. Regarding the extent to which the staff can consider risk, and potentially impose restrictions that stem from risk considerations, on licensee submittals that are not risk-i l

informed, the staff indicated that the policy is still not defined.

Three general issues were identiiled for discussion at the upcoming SG senior management meeting: status of the SG TS, consideration of risk / severe accidents, and grandfathering of previously approved repair criteria and repair methods. The industry and staff tentatively agreed to hold the next technical meeting on June 17,1999.

i t

l NEl/EPRl/ INDUSTRY TECHNICAL MEETING NEl 97-06 IMPLEMENTATION ISSUES MAY 6,1999 LIST OF ATTENDEES NAME ORG/ POSITION

1. Tim Reed NRC/NRR/DE/EMCB

2. Jim Riley NEl

3. Gary Henry EPRI

4. Don Streinz ABB

5. Emmett Murphy NRC/NRR/DE/EMCB

6. Steve Long NRC/NRR/DSSA/SPSB

7. Bill Bateman NRC/NRR/DE/EMCB

8. Phil Rush NRC/NRR/DE/EMCB

9. Ken Balkey Westinghouse

10. Peter Jackson Tetra Engineering

11. Dan Mayes Duke Power

12. Rick Mullins Southern Co.

13. David Stellfox McGraw-Hill

14. Gary Boyers FPL e

15. Bob Keating Westinghouse

16. Bob Tjader NRR/TSB

17. Edmund Sullivan NRC/NRR/DE/EMCB

18. Mike Schoppman FPL

19. Mohammad Behravesh EPRI

20. Kevin Sweeney Arizona Public Service

21. Mati Merilo EPRI

22. Jack Strosnider NRC/NRR/DE

23. Tom Bergman NRC/NRR/ DRIP

24. Edward Throm NRC/DSSA/SPSB

25. Getachew Tesfaye BGE

26. Stephanie Coffin NRR/DE/EMCB

27. Richard Coe Southern California Edison ATTACHMENT 1

NRC/NEl/ Industry May 6,1999 Technical Meeting implementation of NEl 97-06 Introduction 9:00-9:15 am Discussion of Technical and Regulatory issues 9:15 a.m.-2:30 p.m.

Regulatory Framework issues 9:15-11:30am

- Tech Spec Action Statements

-- NEl

-- Tech spec Reporting Requirements

-- NEl

- Revision to Accident Leakage PC

-- NEl

- First time approval SER constraints

--NRC

-Grandfathering Approved ARCS

-- N R C

- Conceptual UFSAR Changes

--NEl Technical issues 12:30-1:30 pm

- Normal Operational DP issue

--NRC

- Definition of Burst and Rupture

-- NEl

-- NDE Uncertainties

-- NEl Risk issues 1:30-2:30

- Do Severe Accidents need to be considered

-NRC

- Probabilistic limit for structural integrity

-NEl Issues for Discussion at Management Meeting 2:30-3:30 p.m.

-Issues where there remains disagreement and should be considered for elevation to management:

-- Probabilistic criteria (use w/o risk and limit)

- Accident leakage increases

- NDE qualification (total system qualification)

-- Definition of burst / rupture (dependent on above)

-- Normal DP for 3XNOP (dependent on above)

- Tech Spec requirements Schedule:- NRC/NEl 3:30 p.m - 3:45p.m.

- Status of Industry generic TS submittal (due July)

- Next Tech Meeting ATTACHMENT 2

E!EJEIRIREENf!N5!iBE Steam Generator Integrity Technical Meeting NRC Staff NEI Steam Generator Task Force May 6,1999 RockviEe, MD

U$$$bh$$$$$ s$$Yh?hhhklhhkl$$l Agenda (continued)

= Senior Management Meeting topics

. Definition ofburst/ rupture

. 3 NO dP

. Tech Specs

. Severe accident considerations a Schedule

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VdlHHHilMlRR%fRGHHHMWER Regulatory Framework a Technical Requirements Manual contains:

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. Deterministic performance criteria consistent with DG 1074

. Contingency measures, reporting requirements, and restoration times

. Verification measures and frequencies

. Defmitions

. Burst

+ Repairmethods/ criteria

+ Normal full power operation

. See draft

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E M il B HR M W i M 0!iki fir M M

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Regulatory Framework

= Reporting requirements in TRM and Tech Specs

. TRM report requirement for margins

<1.0*MSLB dictated by SG inoperability and governed by 10CFR50.72

. TRM requirement for root cause analysis upon failure to meet performance criteria governed by the maintenance rule

. Tech Spec requires twelve-month inspection report

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Regulatory Framework

= SER constraints on first time generic approval of repair methoc.s and repair criteria - NRC c. raft

= SER grancfathering approved repair criteria and repairmethods - XRC draft l

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$$I$$$$?$$1$$$kihklfbb Technical Positions

= Tube burst / tube rupture Burst is defined as the gross structural failure

=

of the tube wall. The condition typically corresponds to an unstable opening displacement (e.g., opening area increased in response to constant pressure) accompanied by ductile (plastic) tearing of the tube material at the ends of the degradation.

=

Basis

. Consistent with ASME Code

+ Gross Structural Failure

. Consistent with laboratory data

+ Burst vs " pop-through"

. Measurable via condition monitoring

+ Eliminates " false positives"

. White paper with detailed discussion 0

pyGfffGfGgQjg((JifffffigfGlllllyigjfJlll Risk issues a Shou.d severe accidents be considered?

= Burden ofproof on NRC to

. justify undue risk.

. NRC Schedule

. Industry Involvement?

= Discussion i

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Schedule 1

= License Package scaedule l

= Xext Meetmgs

+ Senior Management 5/18/99

+ Next technical meeting?

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I NRC/NEl/ Industry Technical Meeting on SG issues Implementation of NEl 97-06 May 6,1999

e FIRST-OF-A-KIND REVIEW / APPROVAL 9

STAFF SUPPORTS INDUSTRY PROPOSAL FOR STAFF REVIEW AND APPROVAL OF NEW REPAIR CRITERIA, NEW REPAIR METHODS, AND ALTERNATIVE PERFORMANCE CRITERIA ON A FIRST TIME BASIS S

TO IMPLEMENT THIS "FIRST-OF-A KIND

• REVIEW AND APPROVAL STRATEGY REQUIRES:

SG TSs BE DEVELOPED THAT ENABLE SUCH CHANGES WITHOUT NEED FOR PLANT SPECIFIC TS AMENDMENTS PER 50.90 NRC STAFF GENERATE AN SER FOR FIRST TIME APPROVALS THAT ADEQUATELY DETAILS THE CONSTRAINTS FOR APPLICATION OF APPROVED APPROACHES AT OTHER FAOILITIES 9

IN IDENTIFYING CONSTRAINTS, THE STAFF MUST BE MINDFUL NOT TO UNNECESSARILY RESTRICT USAGE OF APPROVED REPAIR CRITERIA, METHODS, AND ALTERNATIVE PERFORMANCE CRITERIA BY ESTABLISHING OVERLY RESTRICTIVE CONSTRAINTS-DEFEATS PURPOSE OF THE APPROACH S

TYPES OF CONSTRAINTS THE STAFF WOULD CONSIDER (NOT NECESSARlLY THE COMPLETE LIST) FOR LIMITING APPLICABILITY OF AN APPROVED REPAIR CRITERIA, METHOD, OR PERFORMANCE CRITERIA ARE:

FACILITY TYPE (e.g., IS IT APPLICABLE ONLY TO R, CE OR B&W PLANTS)

SG MODEL (e.g., IS IT APPLICABLE ONLY TO SPECIFIC SG MODELS)

LOCATION WITHIN SG (e.g., FREE SPAN, U BEND, TSPs, TUBESHEET etc)

MATERIAL TYPE (e.g., ALLOY 600,690,800)

DEGRADATION TYPE (e.g., IGSCC, IGA, FATIQUE, THINNING, WEAR etc)

SPECIFIC NDE AND INSPECTION REQUIREMENTS SPECIFIC DATA REQUIREMENTS NEED FOR COMPENSATORY ACTIONS RISK CONSTRAINTS (SEE BELOW) e 0

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FIRST-OF-A-KIND REVIEW / APPROVAL CONT' S

AN EXAMPLE OF ABOVE CONSTRAINTS FOR A REPAIR CRITERIA IS GL 95-05 GL 95-05 LISTS CONSTRAINTS-E SG, DRILLED HOLE TSP, AXIAL, IGSCC, CONFINED WITHIN TSP INTERSECTION ETC j

e MOST DIFFICULT AREA TO IDENTIFY CONSTRAINTS IS RISK AREA:

STAFF WOULD REVIEW INITIAL SUBMITTAL FROM A RISK-INFORMED PERSPECTIVE WITH A FOCUS ON IDENTIFYING WHETHER THE APPROACH i

L HAS A RISK IMPACT AND lF SO WHAT ARE THE IMPORTANT PARAMETERS THAT NEED TO BE CONSIDERED BY OTHER LICENSEES MOST DIFFICULT SITUATIONS ARE PROPOSALS INVOLVING FREE SPAN DEGRADATION - RAISES THE ISSUE OF PERFOhMANCE OF CRACKS UNDER SEVERE ACCIDENT CONDITIONS 1

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I "GRANDFATHERING" APPROVED REPAlR CRITERIA AND METHODS S

PREVIOUSLY APPROVED REPAIR CRITERIA AND REPAIR METHODS WILL CONTINUE TO BE APPROVED 9

THE STAFF WILL NOT RE-OPEN THESE APPROVALS -1.e., WILL NOT REVISIT THESE APPROVALS WITH RISK QUESTIONS ETC-THE OBJECTIVE IS FOR A )

SMOOTH TRANSITION OF APPROVED METHODS TO NEW REGIME 9

EACH PLANT WILL NEED TO REVISE THE SG TSs ON A ONE-TIME BASIS TO IMPLEMENT THE NEW SG TS-THE SER THAT ACCOMPANIES THE TS AMENDMENT WILL INDICATE (AND LIST THE CRITERIA AND METHODS

' ALL PREVIOUS REPAIR CRITERIA AND REPAIR METHODS CONTINUE AS

" APPROVED" APPROACHES PER THE NEW SG TS 3

4 THE LIST OF APPROVED REPAIR CRITERIA AND METHODS WILL BE RELOCA TO THE UFSAR-ASSURES THAT CHANGES TO THESE APPROACHES ARE i

GOVERNED BY 50.59 AT A MINIMUM (i.e. NEW APPROACHES REQUIRE A FIR TIME STAFF APPROVAL) i

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Proposed SG Tech Spse Chengos i

5.5.9 Stearp Generator Prorram

'5.5.9.1.

General Requirements A program shall be implemented through the licensee's procedures to ensure that the SG tube integrity performance criteria are maintained. The SG performance criteria are de5ned in the [ Technical Requirements Manual).

5.5.9.2 Condition Monitoring Assessment Condition Monitoring Assessment means an evaluation of the "as found" cuadition of

' the tubing with respect to the performance criteria. The "as found" condition refers to the condition of the tubing during an SG inspection outage, as determined from the inservice inspection results or by other means, prior to the plugging or repair of tubes. Condition Monitoring Assessments shall be conducted during er-ch outag;e (scheduled or unscheduled) during which the SG tubes are inservice inspected,

-l plugged, or repaired to confirm that the performance criteria are being successfully maintained.

5.5.9.3 Tube Repair Criteria Tube repair criteria shall be described in and implemented by the steam generator program. Prior to use, the repair criteria must be reviewed and approved by the NRC. The licensee may use repair criteria reviewed and approved by the NRC for another facility (or generically)if the licensee demonstrates that the repair criteria are applicable to the licensee's facility for specific defect types and any limitations and conditions set forth in the NRC's safety evaluation of the criteria are met by the licensee. The licensee's demonstration must be documented in a written report available on site for NRC inspection.

5.G.9.4 Tube Repair Methods Steam generator tubes must be repaired using repair methods described in and implemented by the steam generator program. Prior to use, the repair methods must -

be reviewed and approved by the NRC. The licensee may use repair methods reviewed and approved by the NRC for another facility (or generically) if the licensee demonstrates that the repair methods are applicable to the licensee's facility for specific defect types and any limitations and conditions set forth in the NRC's safety evaluation of the methods are met by the licensee. The licensee's demonstration must be documented in a written report available on site for NRC inspection.

As of 05/05/99,4:28 PM Page 1of3

Preposed SG Tech Spec Changos

~

5.6.10 Steam Generator Tube Insnection Renort l

Steam generator tube integrity shall be documented in a post inspection steam generator tube integrity report, submitted within 12 months after completion of the inservice inspection. The report shall address the scope ofinspections performed, existing defect types, NDE technique applicability; and number and location of tubes plugged or repaired during the inservice inspection for each defect type.

B LCO 3.4.18 RCS Onerational LFAKAGE APPLICABLE SAFETY ANALYSIS:

The Technical Specification requirement to limit primary to secondary leakage through any one steam generator to less than 150 gallons per day is significantly less than the initial condition of the safety analysis.

A limit of 150 gallons per day is based on operating experience as an indication of one or more propagating tube leak mechanisms. This leakage rate provides additional assurance against tube rupture at normal and faulted conditions and provides additional assurance that cracks will not propagate to burst prior to detection by leakage monitoring methods and commenecment ofplant shutdown.

1 l

l l

1 i

As of 05/05/99,4:28 PM Page 2 of 3

Proposed Technical Requirements Manuel Changes for Steam Generator Integrity T R E x.y Steam Generators NORMAL TNC x.y Each steam generator shall be operable with no tubes CONDITION exceeding approved repair criteria and with primary to secondary pressure boundary integrity performance criteria as given below.

Performance Criteria (i) Structuralcriteria:

Steam generator tubing shall be demonstrated to retain a margin of 3.0 against burst under normal full power operation and a margin of 1.4 against burst under postulated accidents concurrent with a safe shutdown earthquake.

(ii) Accident induced leakare criteria.

The calculated primary to secondary accident induced leakage rate for the most limiting postulated accident shall not exceed the leakage rate assumed in the accident analysis in terms of totalleakage rate for all steam generators and for leakage rate for an individual steam generator.

-(iii) Ooerational leakare criterion:

Requirements related to the Operational Leakage criterion are delineated in Technical Specification 3.4.13 (RCS Operational LEAKAGE).

APPLICABILITY: MODES 1,2,3, and 4 CONTINGENCY MEASURES:

NONCONFORMANCE CONTINGENCY MEASURES RESTORATION TIME Exceeds repair criteria Plug or repair the affected tubes Prior to entering in accordance with repair MODE 4 methods

~

Margin ofless than 3.0 Report the failure to NRC Prior to entering against burst under MODE 4 normal full power M

operation or a margin of Plug or repair the affected tubes Prior to entering less than 1.4 against burst in accordance with repair MODE 4 under postulated accidents, methods M

M Margin of greater than 1.0 Investigate to determine causal Prior to entering against burst under main factors and perform corrective MODE 4 stesen ?ine break conditions measures M

Provide a special report to the 90 days after entering NRC including a root cause MODE 4 As of 05/05/99,4:28 PM Page1of3

Proposed Technical Requirements Manual Changes for Steam Generator Int,egrity i

NONCONFORMANCE CONTINGENCY MEASURES RESTORATION TIME l

evaluation to determine the reason for the failure and corrective actions taken.

Margin ofless than 1.0 Declare the SG inoperable Immediately against burst under main M

steam line break conditions Report the failure to NRC Per 10 CFR

_QB 50.72(b)(2)(i)

Nominal accident M

induced leakage is Plug or repair the affected tubes Prior to entering greater than [1 gpm],

in accordance with repair MODE 4 methods M

Investigate to determine causal Prior to entering factors and perform corrective MODE 4 measures M

Provide a special report to the 30 days after entering NRC including a root cause MODE 4 evaluation to determine the reason for the failure and corrective actions taken VERIFICATION REQUIREMENTS VERIFICATION FREQUENCY SR x.y Verify steam generator tube In accordance with the steam generator integrity is in accordance with program the performance criteria TRM x.z Definitions The following definitions are applicable to Technical Requirement x.y only.

Accident induced leakage rate means the primary to secondary leakage rate occurring during postulated accidents other than a steam generator tube rupture. This includes the primary to-secondary leakage rate existing immediately prior to the accident plus additional primary to secondary leakinge induced during the accident.

Burst is defined as the gross structural failure of the tube wall. The condition typically corresponds to an unstable opening displacement (e.g., opening area increased in response to As of 05/05/99,4:28 PM Page 2 of 3

Propossd Technical Requirements Manual Changes for Steam Generator Integrity constant pressure) accompanied by ductile (plastic) tearing of the tube material at the ends of the degradation.

Normal full power operation is defined as th[ conditions existing during MODE 1 operation at the maximum steady state reactor power allowed by the plant design as defined in the SG equipment or design specification.

Repair Criteria are those NDE measured parameters at or beyond which the tube must be repaired or removed from service by plugging. The repair criteria approved for use are:

40% nominal tube wall thickness i

[..........]

e Repair Methods are those means used to reestablish the RCS pressure boundary integrity of SG tubes without removing the tube from service. The repair methods approved for use are:

[........]

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As of 05/05/99,4:28 PM Page 3 of 3

May 1999 Resolution NRC Staffissues identified 10/7/1998.

1. NRCStaffComments (10/7M8h StructuralPerformance Criteria ne structural integrity criteria should be revised consistent with DG-1074.

Specupcally, factor of 3 criterion for NOP and 1.4 criterion for accident conditions should be specipcally spelled out to ensure consistency of interpretation.

Industry Resnonse (12/17/98):

The performance criteria of Section 2.1 will be revised as follows:

1 Satisfying the detenninistic performance criteria means that all tubes have been 4

detennined to retain a margin of 3.0 against gross failure or rupture under normal full power conditions.....

i NRC Response (2/10/99)

We do not agree with the substitution of"fullpower"for "normalplant operating conditions, including startup, operation in the power range, hot standby, and cooldown, and all anticipated transients that are included in the plant design specspcation. " Tube integrity is important to safety in more thanjust "fullpower" modes ofoperation NEI nronosed resdution (5/6/99):

NEI position per 12/17/98 is unchanged. The basis for this position has been funher defined in the attached white paper " Deterministic Structural Perfonnance Criteria Pressure Loading Definition."

NEI considers this item closed.

2. NRCStafYComments (10/7M8h Depnition oftube rupture and burst should be revised consistent with DG 1074.

Industry resnonse (12/17/98):

None provided NRC Response (2/10/99):

Industry did not propose an alternative depnitions. The Staf believes the proposed depnitions in DG 1074 are appropriate, but is willing to discuss alternatives that the industry maypopose.

NEI nroposed resolution (5/6/99):

The industry has developed a deildtion on burst as described in the attached white paper, " Definition of Burst."

This definition is consistent with the 1

e For example, NElguidelines could address the definition and objectives ofNDE validation. The EPRI guidelines could provide guidelines for validating NDE systems.

Approach being developed by TVA/PG&E to quantify NDE detection and sizing performancefor PWSCC at TSPs appearspromising.

Industry Resnonse (12/17/98h Validation of NDE techniques is adequately addressed in the EPRI PWR SG Examination Guidelines Section 6, Appendix G and Appendix H. These sections of the NDE Guidelines identify the process by which an eddy current technique is developed and the analyst perfonnance facton associated with the NDE techniques. Taken as a whole, the process addresses:

)

technique performance e

i analysis performance e

process controls e

human performance factors e

field analysis feedback e

' Appendix H addresses eddy current technique capabilities measured against metallurgically determined flaw depths.

Appendix G addresses analyst qualification and analyst flaw measurement variations. Section 6 combines the requirements of both appendices with protocols that maximize inspection effectiveness. The process accomplishes this through the elements identified below.

. Adequate eddy current technique detection performance is accomplished through Appendix H compliance, which provides:

a statistically adequate number of flaws in the technique qualification

=

data set (H2.2.2a) data sets consisting ofpulled tubes or lab flaws that are representative

=

of actual flaws (H2.2.1cae) specific details on hardware and set-up essential variables for eddy

=

i current data acquisition (H.1) assessmrnt ofextraneous test variables associated with each' damage

=

mechanism (H2.2.ld) a technique POD (80% at a 90% confidence le. vel) applicable to the

=

range of flaws in the data set (H2.3.1, H2.2.2c) review ofresults by qualified personnel (section 6.2.1, H3.5.1)

=

Techniques are verified applicable to each implementing site v:a the site-e qualification process. This process verifies that the technique to be used for each degradation mechanism is appropriate by comparing the technique data set and plant data in the following areas (section 6.2.4, H2.2.1d):

3

the flaw specimen data set shall cover the range of flaw depths of

=

interest (H2.2.3d) the additional sample set and eddy current technique must provide

=

enough data to quantify measurement uncertainty to the degree required by the Condition Monitoring and Operational Assessments.

(H2.2.3d) the total NDE System measurement uncertainty is used in the

=

Condition Monitoring and Operational Assessments. This accounts for eddy current technique and analyst variability. (sections 5.2,6.1)

In support ofits CM & OA, qualification of NDE uncertainty beyond those supplied by the PWR Examination Guidelines, Rev. 5 and how the uncertainties are integrated will be determined on a plant-specific basis.

NRCResolution (MOM 9h Stqf agrees EPRI Guidelines (Appendix G & H, Section 6) ensure NDE tech.tiques and personnelfor given application have adequate capability such that when implemented in conjunction with other elements of the SG program,

\\

reasonable assurance oftube integrity can beprovided.

\\

Staf agrees that licensees may disposition tubes on the basis offlaw depth measurements when NDE techniques andpersonnel are qualified on accordance with theEPRIguidelines.

As acknowledged by the industry in response to this item and item 15, qualification per the EPRI guidelines dose not provide guidancefor quantifying the flaw detection and string performance on the integrated NDE system (technique, personnel, datu analysis procedures, process controls) as needed to support condition monitcring and operational assessments. The issue is addressedfurther under item 15 below, NEI cronosed re10lutiDJLf5ffi5th The industry agrees with the NRC on the first two paragraphs.

The industry believes that adequate guidance for sizing and detection performance is provided for condition' monitoring and operational assesunents. The guidance can be found in a white paper that describes where to get the RMSE for sizing performance and POD for probability of detection.

Additionally, this paper provides examples of combining analyst and technique uncertainties.

The SG Integrity Assessment Guidelines will describe how to use uncertainties.

Industry considers this item closed.

5

This broad, regulatory definition of active degradation mechanism is used primarily in Section C.1.1.4, Expanded Inspection Sample, to require the sample expansion for each active defect type identified in the initial inspection.

Consequently, there are two different definitions for an active degradation mechanism which are used in two different approaches for inspection of the steam generators that arrive at essentially the same results.

For the above reasons, from the industry perspective, there is no benefit to redefining active degradation mechanism. In addition, a redefinition would require a re-write of the PWR Steam Ge.nerator Examination Guidelines with a newlogic path.

i It should be noted that active degradation mechanism is not used in Section 4 of the PWR Steam Generator Examination Guidelines. Section 4 is the performance based inspecion guidelines referenced in question 13 above.

No change to the NEI or EPRI guicdaes is required.

NRCResolution (2/10/99h Industryresponseis acceptable NEI nronosed resolution (5/6/99):

NRC response is acceptable. Industry considers this item closed.

15. NRCStaffComments (10/7/1998h NDE SirInr Performance NElguidelines should state that tube integrity assessments may be based on NDE defect sizing measurements only if the sizingperformance ofthe NDE system has been validatedper definition in DG-1074for the subject defect type.

Industry Response (12/17/99):

Per Steam Generator Tube Integrity and the PWR Examination Guidelines, the technique utilized shall support the requirements of condition monitoring and operational assessment. Section 6 and Appendices G & H of the EPRI PWR Examination Guidelines are capable of supplying data that quantifies detection and sizing capabilities for eddy current techniques and analysts. Quantification of NDE uncertainties beyond those supplied by the PWR Steam Generator Examination Guidelines and how the uncertainties are integrated will be determined on a plant-specific basis in a manner that supports the plant's integrity assessments.

Recent industry NDE and in situ results suggest that this approach is effective in assuring steam generator tube integrity.

Consideration will be given to standardizing treatment of NDE uncertainties as part of the Tube Integrity Guidelines; however, the present approach is considered adequate.

7

'O "Forplants experiencing a damageform or mechanismfor which no depth shing capability exists (per EPRIAppendices G &H, Section 6), tubes identified with such damage are " repaired / plugged-on-detection " and integrity should be assessed."

Industry considers this item closed.

9

Definition of 34 P Deterministic Structural Performance Criteria Pressure Loading Definition i

Definition.

For structural integrity assessments using a factor of safety of three, the loading condition shall be the pressure across the steam generator tube at normal full power operation as defined in the design or equipment specification.

Discussion NEI has endeavored to define the appropriate, historically supported loading definition for the deterministic structural integrity performance criteria. It is NEI's position that the description contained in DG-1074 is not consirtent with past NRC positions and the intent of the ASME Code for original design and evaluation ofinservice components.

ASME Code Review 4

A review of multiple-industry documents, including NSSS design reports, sleeving topical reports, and regulatory submittals, indicates that all NSSS designers and multiple utilities have utilized the same ASME Section III Code equation, from paragraph NB 3324.1 to define minimum allowable tube wall thickness. A typical form from Reference 1is as follows:

APRg i* =

(1)

P,,, - 0.5 AP '

where t.4,, = minimum acceptable tube wall AP = primary to secondary pressure differential Rs = tube radius P. = primary stress limit,i.e.,

P. normal s S /3 4

P. upset s Sy P. faulted s 0.7S.

In Reference 2, the same equation was written as 3APR;

• " Su -0.5(Pg + P,)'

1

Definition of SAP The ASME Section 111 design requirement is therefore, that tube wall thickness should be maintained at greater than t.a. All the submittals surveyed used normal full power AP as the basis for primary-to-secondary pressure differential. It is important to note that these documents received Staff review and approval.

Historical Regulatory Perspective NEI has reviewed historical information regarding Staff positions on this issue. From a review of the testimony of James Knights, Raymond Maccary4, Atomic Safety and Licensing Boards and Regulatory Guide 1.1215, it is clear that the primary requirements for margin of safety for steam generator tubes were:

(1) tubes with detected acceptable defects would not be stressed during the full range of normal reactor operation, beyond the elastic range of the tube material, (2) the factor of safety against failure by bt rsting under normal operating conditions should not be less than three.

Meeting requirement (1) assures that at normal operation, the maximum stress in the degraded tube will never exceed the yield stress for the tube material.

Normal operation, as used here, includes stut-up and operational transients that are included in the design specification for the steam generator. For requirement (2) an explicit description of normal operating conditions that includes the full range of operational transients is not specified. However, Mr. Knight does point out that "... new steam generator tubes are typically manufactured with a wall thickness much greater that the wall thickness required by the design rules of ASME Code,Section III" (see previous

. discussion) and Mr. Knight further indicates that approximately twice the thickness (nominal / minimum) is typical. If in fact minimum wall calculations were based on the full range of operational transients or RCS design pressure safety limits, the typical margin above minimum wall would be on the order of 10-20%, meaning plugging limits would have to be lowered well below most licensees current 40% criteria.

Statements in Regulatory Guide 1.121 provide additional insight for industry's consistent application of this criterion. Section 3.a.1 of the regulatory guide states that i

loadings associated with normal plant conditions, including start-up, operation in the t

power range, hot standby, cooldown and all anticipated transients should not produce a primary member stress in excess of the yield stress. Once again, this statement is explicit, whereas the statements in Section 2.a.2 and 2.a.4 of the RG simply state a margin of safety under normal operating conditions should not be less than three (3).

1 i

2 a

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Definition of SAP i

Conclusion As stated previously, the use of normal full power operating pressure differential has j

time and time again been utilized as the basis for compliance with the three AP criteria.

The Technical Specification plugging limits for the plants surveyed were based on full power differential pressure.

The surveyed design reports for minimum wall calculations for tubing and sleeves and Regulatory Guide 1.121 compliance calculations were based on normal full power differential pressure. Additionally, use of the values listed in the design or equipment specification ensures consistency of application.

As such, NEI believes the interpretation in DG 1074 constitutes a regulatory position that is either new or different from a previously applicable staff position, which represents a backfit per 10CFR 50.109. Additionally, based on the consistent ' application by industry in regulatory submittals and subsequent approvals by the NRC since 1975, compliance exception is not considered applicable, since this exception was intended to address situations "in which the licensee has failed to meet known and established standards of the Commission because of omission or mistake of fact." In unclusion, the current definition as provided by NEI in Reference 7 is supported for inclusion in NEI 97-06.

References:

I

1. WCAP (later)

2. Letter LD-83-058, AB-CE to Mr. Darrell Eisenhut, Director, Division of Licensing USNRC, Rapid Depressurization and Decay Heat Removalfor System 80, dated June 29, 1983.

3. Testimony of James Knight before the Atomic Safety and Licensing Board, January 1975.

i

4. Testimony of Raymond Maccary before the Atomic Safety and Licensing Appeal Board, January 1976.

S. Atomic Safety and Licensing Board, LBP-75-27, May 1,1975

6. Draft Regulatory Guide 1.121, Basesfor Plugging Degraded PWR Steam Generator Tubes, August 1976 3

Definition ofBurst for SG lhbes Definition of Hurst RecommendedDefinition ofBurst-Burst is dermed as the gross structural failure of the tube wall ne condition typically corresponds to an unstable opening displacem ompanied by ductile (plastic) tearing of the tube materia!! at the ends of the degradation Lu,411y.is de--M M gening' area is mereased in response to constant pressurg p

+s 4

Discussion l

Since a burst definition is a required component for ccndition monitoring and operational assessment, a definition which can be analytically defined and is capable of being assessed via in situ and laboratory testing is required. Furthermore, the definition must be consi= tent with ASME Code definitions, and one that applies to most formi. of tube degradation.

Additionally, the definition is intended to demonstrate accord with the testimony of James i

Knight', and compliance with the historical guidance of the Regulatory Guide 1.121. The 8

definition of burst per these documents is with regard to gross failure of the pressure boundary, e.g., "the degree ofloading required to burst or collapse a tube wall is consistent with the safety factor in Section III of the ASME B&PV Code". Burst, or gross failure, according to the Code would be interpreted as a catastrophic failure of the pressure boundary.

The proposed definition must also support the condition monitoring process. Verification of structural integrity during condition monitoring may be accomplished via in situ testing.

Since these tests do not have the capability to provide an unlimited water' supply, nor the capability to maintain pressure under certain leakage scenarios, opening area may be more a function of fluid reservoir rather than tube strength. Additionally, in situ designs with bladders may not be reinforced. In certain cases, the bladder may rupture but tearing or extension of the defect has not occurred. This condition may simply mean the opening of the flanks of the defect was sufficient to permit extrusion of the bladder, and that the actual, or true, burst pressure was not achieved during the test.8 The definition is also intended not to characterize local instability, or for example, " ligament pop-through" as a burst. The onset ofligament tearing need not coincide with the onset of a full burst. As an example of not having a burst, consider an axial crack about 0.5" long with a uniform depth at 98% of the tube wall. Deformation during pressurization would be expected to lead to failure of the remaining ligament, i.e., extension of the crack tip in the radial direction, at a pressure below that required to cause extension at the tips in the axial direction. Thus, this would represent a leakage situation as opposed to a burst situation and a factor of safety of three against crack extension in the radial direction may still be demonstrated. Sirailar conditions have been observed for deep wear indications.

Additional infor:ution found in Reference 4, further supports the proposed definition of burst. It is noted that if tube failure, i.e., burst, is defined "as plastic deformation of the crack

e Defnition ofBurst for SG 1hbes to the extent that the sides of the crack open to a non-parallel elliptical configuration, the tubing can sustain added internal pressure beyond those values before reaching a condition of gross failure.

In conclusion it is industry's position that the proposed definition is consistent with the Staf!'s definition in DG-1074 and with historical regulatory references, while providing necessary clarification to support condition monitoring and operational assessment for most defect forms.

References:

i 1.

Testimony of James Knight Before the Atomic Safety and Licensing Board, Docket Nos.

50-282 and 50-306, January 1975.

{

2.

Regulatory Guide 1.121 (Draft), " Bases for Plugging Degraded PWR Steam Generator Tubes," United States Nuclear Regulatory Commission, August 1976.

3.

EPRI TR-105505, Final. Report, Burst Pressure Correlation for Steam Generator Tubes with Through-Wall Axial Cracks i

4.

NUREG-0491, " Safety Evaluation Report Related to the Preliminary Design of the Standard Reference System RESAR-414," Docket Number S.TN 50-572, United States 1

Nuclear Regulatory Commission, November 1978.

5.

Draft Regulatory Guide DG 1074, Steam Generator Tube Integrity 6.

EPRI TR-107620, April 1999, In Situ Pressure Testing Guidelines l

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