ML20205N745
| ML20205N745 | |
| Person / Time | |
|---|---|
| Issue date: | 04/13/1999 |
| From: | Tim Reed NRC (Affiliation Not Assigned) |
| To: | Bateman W NRC (Affiliation Not Assigned) |
| References | |
| NUDOCS 9904190119 | |
| Download: ML20205N745 (18) | |
Text
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NUCLEAR REGULATORY COMMISSION 2
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%'.....p April 13, 1999 MEMORANDUM TO: William H. Bateman, Chief Materials and Chemical Engineering Branch Division of Engineering Office of Nuclear Rcactor Regulation THRU:
Edmund J. Sullivan, Chief NDE & Metallurgy Section Materials and Chemical En,Weering Br nch Division of Engineering Office of Nuclear Reactor Reg ' tion FROM:
Timothy A. Reed, Senior Project Man er 1 NDE & Metallurgy Section Materials and Chemical Enginearir.g Br Division of Engineering Offics of Nuclear Reactor Regulation
SUBJECT:
SUMMARY
OF THE APRIL 1,1999, TECHNICAL MEETING WITH NEl/EPRl/lNDUSTRY TO DISCUSS ISSUES INVOLVING IMPLEMENTATION OF NEl 97-06 On April 1,1999, the NRC staff met with representatives of Nuclear Energy Institute (NEI).
Electric Power Research Institute (EPRI) and industry to di.= cuss technical issues involving the implementation of NEl 97-06 " Steam Generator Program Guidelines." Meeting attendees are identified in Attachment 1. The meeting handouts are provided as Attachment 2.
The meeting discussion focused on three principle technical issues: 1) the appropriate value for normal operating AP to use in the 3 times AP criterion,2) the definition of tube burst, and 3) a draft steam generator technical specification that incorporates the "first-of-a kind" NRC review / approval concept.
Regarding each of these technical areas, the following key points were made during the meeting :
- 1. NormalOperating AP:
Industry agrees with the NRC staff that a safety facter of three against tube burst needs to be maintained for the entire planned operating cycle. The technicalissue is what AP should be used in the three times normal, operating AP calculatien. Industry indicated that the normal industry practice in support of sleeving amendments, repair criteria submittals, and in the original tube design has been to utilize the nominal full power differential pessure u
across the tube wall. Industry indicated that upset transients were considered to ensure p V) that a stress in the tube in excess of yield stress was not produced, but such transients were not utilizt.d to identify a bounding AP for the 3 times AP criterion.
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The. industry indicated that their research into this issues has not identified any instances where the staff took exception to this industry practice.' It is the industry's, position that this -
J practice should continue for the implementation of NEl 97-06 and the response on this issue :
provided in the December 17,1998, NEl letter to ttie staff remains unchanged. The staff indicated that it would reconsidor the issue in light of the additional arguments presented by industry during the meeting.
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-2.
Definition of Tube Burst:
Industn; expressed a concern that the NRC staff's definition of tube burst in DG-1074 did ~
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not appear to account for ligament pop-through (where a crack ligament fails without a gross structural failure of the tube). The NRC staff indicated that it was not the intention to" have pop-through constitute tube burst and that it is would_ be willing to consider an industry pioposal to clarify this issue. Industry also commented that it prefers to have a definition that relates tube burst to a flow rate, (rather than the incipient tube burst as proposed by the NRC staff). The staff noted that defining tube rupture as being less than makeup capacity as suggested in NEl 97-0G does not make sense since makeup capacities vary significantly from plant to plant with some plants having very large makeup capacities that would virtually ensure that such a definition of tube burst would never be met. There was considerable discussion on how to construct a definition of tube burst that can account for the various situations encountered in the field (e.g., situations where a bladder can not ba used to in situ pressure test) without being overly complex. The staff suggested that industry should take an action to develop an alternative definition that utilizes the staff's definition as a starting point.
- 3. Steam Generator Technical Specification:
The staff discussed a draft version of a steam generator technical specification that would replace the current steam generator technical specification. The draft steam generator technical specification incorporates a pedormance-based structure and the first-of-a-kind staff review / approval concept for changes to performance criteria, repair criteria, and repair methods. An issue sual under censideration by industry and the staff is how to treat, from a licensing perspective, submittals for "first-of-a-kind" approvals (i.e., are they license amendments or simply submittals for which *he staff generates a safety evaluation in a manner similar to topical repurts).
1 The industry and staff agreed tentatively to hold the next technical meeting on May 6,1999.
Attachments:. As stated DISTRIBUTION:
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The industry indicated that their research into this issues has not identified any instances where the staff took exception to this industry practice it is the industry's position that this practice should continue for the impismentation of NEl 97-06 and the response on this issue provided in tha December 17,1998, NEl letter to the staff remains unchanged. The staff indicated that it would reconsider the issue in light of the additional arguments presented by industry during the meeting.
- 2. Definition of Tube Burst:
Industry expressed a concern that the NRC staff's definition of tube burst in DG-1074 did not appear to account for ligament pop-through (where a crack ligament fails without a gross structural failure of the tube). The NRC staff indicated that it was not the intention to have pop-through constitute tube burst and that it is would be willing to consider an industry proposal to clarify this issue. Industry also commented that it prefers to have a definition that relates tube burst to a flow rate, (rather than the incipient tube burst as proposed by the NRC staff). The staff noted that defining tube rupture as being isss than makeup capacity as suggested in NEl 97-06 does not make sense since makeup capacities vary significantly from plant to plant with some plants having very large makeup capacities that would virtua!!y ensure that such a definition of tube burst would never be met. There was considerable discussion on how to construct a definition of tube burst that can account for the various situations encountered in the field (e.g., situations where a bladder can not be used to in situ pressure test) without being overly complex. The staff suggested that industry should take an action to develcp an alternative definition that utilizes the staff's definition as a starting point.
- 3. Steam Generator Technical Specification:
The staff discussed a draft version of a steam generator technical specification that would replace the current steam generator technical specification. The draft steam generator technical specification incorporates a performance-based structure and the first-of a-kind staff review / approval concept for changes to performance criteria, repair criteria, and repair methods. An issue still under consideration by industry and the staff is how to usat, from a licensing perspective, submittals for "first-of-a kind" approvals (i.e., are they license amendments or simply submittals for which the staff generates a safety evaluation !n a manner similar to topical reports).
The industry and staff agreed tentatively to hold the next technical meeting on May 6,1999.
Attachments: As stated s
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NEl/EPRl/ INDUSTRY TECHNICAL MEETING NEl 97-06 IMPLEMENTATION ISSUES APRIL 1,1999 LIST OF ATTENDEES NAME ORG/ POSITION
- 1. Tim Reed NRC/NRR/DE/EMCB
- 2. Jim Riley NEl
- 3. Michael Short Southem Califomia Edison
- 4. Don Streinz ABB
- 5. Emmett Murphy NRC/NRR/DE/EMCB
- 6. Steve Long NRC/NRR/DSSA/SPSB
- 7. Bill Bateman NRC/NRR/DRPW/PO4-2
- 8. Phil Rush NRC/NRR/DE/EMCB
- 9. Greg Kammerdeiner Dusquesne Light
- 10. Fred Anderson Tetra Engineering
- 11. Dan Mayes Duke Power
- 12. Rick Mullins Southem Co.
- 13. Davis Stellfox McGraw-Hill
- 14. Gary Boyers FPL
- 15. Richard Pearson NSP
- 16. Bob Tjader NRR/TSB
- 17. Edmund Sullivan NRC/NRR/DE/EMCB
- 18. Mike Schoppman FPL
- 19. Mohammad Behravesh EPRI i
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e espegesgtStggangn@eik Steam Generator Integrity Tec1nical Meeting NRC Staff XEI Steam Generator Task Force April 1,1999 Rockville, MD
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Agenda a Technicalpositions 3 NO delta P Tube burst / tube rupture
= Regulatory Framework l
Technical Specifications ARC / tube repair methods NRC approval
= EPRI Guic elines a License Package Schecu e l
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ye Technical Positions
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3 NO delta P Statement of Facts
+ 12/17/98 NEI letter to NRC indicates that industry has accepted 3NODP and 1.4 MSLB
" Measurable" performance criteria
+
Applied during condition monitoring
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process No regulatory concern on operational a
assessments unless failure to meet CM
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Action statements need development
=
For RCS pressure boundary
+
Code of Federal Regulations requires
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RCSPB to comply witli ASME Section III and XI Licensing basis for several surveyed plants
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meet ASME Code / Safety factor of 3 DG 1074 interprets ASME Code to require
+
Safety Factors of 3 and 1.4
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Normal plant operation including startup,
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operation in power range, hot standby, Ek I cooldown and all anticipated transients g
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= 3 NO de..ta P DG 1074 definition requires testing at pressures which are significantly higher than current practice and design Historical precedence indicates that normal full power definition is reasonable
+ James Knight position and testimony (1975)
= Tubes with defects will not be stressed during full range of reactor operation beyond yield Interpretation - full primary pressure with depressurized secondary (safety factor provided by yield strength limit)
= A factor of safety against burst under normal operating conditions Interpretation - normal operating conditions differs from full range of normal reactor operation providing factor of safety of 3 QEI
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Technical Positions 3 NO delta P 3
+ Draft RG 1.121 supports same definition Section 2.a.1 states I
Tubes with part thru wall cracks should not be stressed during full range of normal reactor operation beyond the elastic range of tube i
material Section 2.a.2 and.4 state Margin of safety against tube rupture under normal operating conditions j
should not be less than 3 Section 3.a.1 states Loadings associated with normal plant conditions including startup, operation in the power range, hot standby cooldown and all anticipated transients should not produce a primary member stress in excess of the yield stress l
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Technical Positions
=
3 NO delta P Basically SF of 3 has been applied in surveyed documents (sleeving topicals, NRC submittals) in the mia wall calc
+ From NB 3324.1
+tmin = AP*Ri/Pm -0.5(Pi+Po)
(Westinghouse) where Pm = primary stress limit
=
Pm normal <Su/3
=
Pm upset <Sy
=
Pm faulted <0.7Su
=
Usually ASME Code minimum properties
=
+tmin =3AP*Ri/Su - 0.5(Pl+P2) (CE )
+ So for code compliance wall should be
>tmin
+ Plugging limit per RG 1.121 1-(tmin+ Growth +NDE)
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+ All submittals surveyed used normal full power AP QEI
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Technical Positions
=
Tube burst / tube rupture Concern with NRC definition defect specific
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no allowance for pop-through
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Concern with industry definition burst linked to rupture definition
+
burst would be equal to flow area
+
associated with guillotine break
+
Proposed solution:
Eliminate defect specific wording at
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3NOdP Provide burst definition with flow
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component for burst at or near MSLB Supports accident induced leakage
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definition Supports pop-through
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Regulatory Framework
= Tec1nica Specifications LCO, Actions, and compliance requirements difficult to develop in a performance based environment Revised operational leakage LCO (150 gpd ) should not become the default input fbr Chapter 15 accident analysis
+ Conflicts with current SRP Should retain the deterministic basis for current default input assumptions to Chapter 15 QEI
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Regulatory Framework
= ARC / Tube repair Methods
. NRC prior approval for first time use
+Xeec. to c efine review elements
. Subsequent use by 50.59 v
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EPRI Guideline Status
= In Situ Pressure Scheduled for release 4/30 m SGIntegriy Assessmen:
Scheduled for release 6/30 j
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License Package Schedule Schedule
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. Target c ate 7/31
. Mee:ings Tec3 Meeting 5/6
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Senior Management ~5/20
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gEI
opgr Steam Generator Tube Inieority Proaram
- 1. GeneralRequirements A program consisting of preservice and inservice tube inspections, tube repair criteria, condition monitoring, and operational assessments shall be implemented to ensure that the tube integrity performance criteria in 2. are maintained throughout the period between scheduled tube inspections. The SG program shall be documented in plant procedures, be auditable, and conform to Appendix B of 10 CFR Part 50,
- 2. Tube Integrity Performance Criteria
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A Tuba integrity performance criteria shall be as given below or, attematively, shall comply with the provisions of 2.B.
(i) Structural criteria: All tubes shall retain a margin of 3.0 against burst under normal operating conditions and a margin of 1.4 against burst under postulated accidents concurrent with a safe shutdown earthquaks, (il Operational leakage criterion; Operational primary-to-secondary leakage rate in each steam generator shall not exceed [the primary-to-secondary leakage in TS 3.4.13 [or insert applicable TS).
(il Accident leakage criteria: The calculated primary to secondary accident leakage rate for the most limiting pot.tulated accident shall not exceed the LCO operational leakage rate limits (TS 3.4.13 [or applicable TS]) in terms of total leakage rate for all steam generators and for leakage rate for an individual steam generator.
B. Alternatives to criteria (i) and (iii) in Section 2.A abeve may be implemented for specific defect types,'but only if the performance criteria reviewed and approved by the NRC prior to use at the licensee's facility. However, such NRC review and approval is not necessary if the licensee uses performance criteria reviewed and approved by the NRC for another facility (or generically), but only if the licensee demonstrates that the performance 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 methods will be met by the licensee. The licensee's demonstration must be documented in a written report available on-site for NRC inspection, and the alternative criteria must be described in [ DOCUMENT).
- 3. Condition Monitoring Assessmeni Condition monitoring assessments shall be conducted during each outage (scheduled or unscheduled) during which the SG tubes are inservice irispected, plugged, or repaired to confirm that the performance criteria are being successfully maintained.
Should a tube or tubos be found which fall to satisfy these criteria, the licensee shall:
(1} report the failure to ttie NRC within 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br />, (ii) take corrective action, and
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' hM (iii) submit a written report [30 days) prior to plant startup which describes the reasons for the failure to meet the performance criteria, and the corrective actions taken to prevent recurrence.
- 4. Tube Repair CrNoria A. All tubes found to be defective during preservice orinservice inspection shall be removed from service by plugging or shall be repaired in accordance with 5. prior to plant startup from the inspection outage. Tubes are defective when they contain indications which fall to meet the applicable tube repair criteria. Tube repair criteria shall be described in the steam generator program and in the updated final safety analysis report.
B. Prior to use, the repair criteria must be reviewed ano approved by the NRC for use at !bs licensee's facility. However, such NRC review and approval is not necessary if the licensee uses repair criteria reviewed and approved by the NRC for another facility (or generica!!y), but only 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 will be met by the licensee. The licenseu's demonstration must be documented in a written report available on-site for NRC inspection.
- 5. Tube Repair Methods q
Steam generator tubes must be repaired using repair methods described in the steam generator program and in the updated final safety analysis report. Prior to use, the repair methods must be reviewed and approved by the NRC for use at the licensee's facility.
However, such NRC review and approval is not necessary if the licensee sises repair methods reviewed and approved by the NRC for another facility (or generically), but only if the licensee demonstrates that the repair methods are applicable to the licensee's facility and any limitations and conditions set forth in the NRC's safety evaluation of the methods will be met by the licensee. The licensee's demonstration must be documented in a written report available on-site for NRC inspection.
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- 6. Steam Generator inspection Report The licensee shall submit to the NRC a steam generator inspection report within12 months following completion of the inservice inspection required by item.2 above. The report shall address:
(i) the number and extent (e.g., full length, hot leg only) of tubes subjected to inservice j
inspection and to any supplemental testing (e.g., in-situ pressure testing) as part of the condition monitoring assessment, (ii) the type of NDE test probe used (e.g., eddy current bobbin coil, eddy current rotating pancake coll),
(iii) the location, orientation (of linear type indications), and measured size of each I
indication found by inservice inspection, 4
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(iv) the results of any supplemental testing (e.g., in-situ pressure testing), and (v) identification of tubes plugged and repaired.
(vi) identification of performance criteria, repair criteria, and repair methods uti!Med during the SG inspection outage.
- 7. Definitions accident 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 leakage induced during the accident.
burst means gross structural failure of the tube wall. Analytically this corresponds to a condition in which a critical parameter for unstable crack propagation e.g., limit load, is exceeded.
Experimentally, it corresponds to unstable crack propagation limited only by testing considerations e.g., loss of bladder or depletion of the pressure reservoir.
condition monitoring means an assessment of the *as found" condition of the tubing with rt spect 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.
defective tube (or tube which is defective) means that the tube exhibits an indication exceeding the applicable tube repair criteria.
defect type refers to a degradation mechanism (e.g., wastage, stress corrosion cracking) and an associated set of general circumstances which affect determination of appropriate NDE techniques for flaw detection and sizing, flaw growth rates, and calculational models for determining structural and leakage performance. General circumstances may include tube size, tube material, defect orientation, whether the defect initiates from the tube primary side or secordary side, and defe location within the tube (e.g., in straight freespan, in u-bend, at tube support plate, at expansion transition).
Indication means the NDE signal response to a defect or condition which is present in the tube.
operational assessment means an assessment to ensure that the tubes wl!! continue to satisfy the performance criteria until the next scheduled inspection.
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