ML20249C462
| ML20249C462 | |
| Person / Time | |
|---|---|
| Site: | Seabrook  |
| Issue date: | 06/24/1998 |
| From: | Feigenbaum T NORTH ATLANTIC ENERGY SERVICE CORP. (NAESCO) |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| References | |
| AR#98007102, GL-92-01, GL-92-1, NYN-98085, TAC-MA0571, TAC-MA571, NUDOCS 9806300059 | |
| Download: ML20249C462 (9) | |
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North Atlantic Energy Service Corporation
'$N Atlantic seahroot, un 03874 P.O. Box 300 0
(603) 474-9521 The Northeast Utilities System June 24,1998
. Docket No. 50-443 NYN-98085 AR#98007102 United States Nuclear Regulatory Commission Attention: Document ControlDesk Washington, D.C. 20555 Seabrook Station
' Response to Information Request Reoardino peactor Veccel Inteority (TAC NO. MA 05711 Nonh -Atlantic Energy Service Corporation (North 'Atlantit) provides in the Enclosure additional information regarding reactor pressure vessel integrity at Seabrook Station, Unit No.1. The information is provided in response to a March 31,1998 information request. The enclosure
- provides validation of previously submittec' responses to Generic Letter 92-01, " Reactor Vessel Structural Integrity" revisions and supplements.- North Atlantic submitted the Analysis of Seabrook Station Unit 1 Reactor Vessel Surveillance Capsules U and Y tmder separate cover dated June 5, 1998. Relevant information from the Surveillance Capsules U and Y report has been duplicated in this response as appropriate for completeness.
'Ihe June 1997 Combustion Engineering Owners Group report, "CE NPSD-1039, Revision 02, "Best Estimate Copper and Nickel Values in CE Fabricated Reactor Vessel Welds" was prepared prior to evaluation of Seabrook Station's second surveillance capsule. Consequently, the CE report does not contain the latest Seabrook Station specific information.
I orth Atlantic will submit changes as needed to the reactor coolant system heatup, cooldown and N
cold overpressure protection setpoints included in the Technical Specifications prior to our eleventh j
effective full power year of operation. The station is currently in its sixth effective full power year.
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-NYN-98085 / Page 2 g,
I i-Should you $have any; questions, please contact Mr. Terry Harpster, Director of Licensing Services, at (603) 773-7765.
Very truly yours, NORTH ATLANTIC ENERGY SERVICE CORP.
N Ted C. Feigenbaum
/
l Executive Vice President and ChiefNuclear Officer cc:
H. J. Miller, NRC Regional Administrator p
J. T. Harrison, NRC Project Manager, Project Directorate 1-3
. R. K. Lorson, NRC Senior Resident Inspector t-Rockinghaun, ss.
DATE 4
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l Then personally appeared before me, the above-named Ted C. Feigenbaum, being duly sworn, l-
' did state that he is Senior Vice President and Chief Nuclear Officer of the North Atlantic Energy 1
' Service Corporation that he is duly authorized to execute and file the foregoing information in
' the name and on the behalf of North Atlantic Energy Service Corporation and that the statements L
therein are true, to the best of his knowledge and belief.
AH1 dbeNM Marilyn R. Sullivan, Noth Public My Commission Expires: March 19,2002
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ENCLOSURE TO NYN-98085 1
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Enclosure Seabrook Station Response to Request for Additional Information Regarding Reactor Pressure Vessel Structural Integrity
Background
' On March 31,1998 the NRC issued a Request for Additional Information (RAI), Reference (a),
regarding the impact, if any, of the additional weld chemistry data presented in the Combustion Engineering Owners' Group (CEOG) summary report, Reference (b), on previous structural l
integrity assessments of the Seabrook Station Reactor Pressure Vessel (RPV). North Atlantic I
has also evaluated the potential impact of the CEOG report relative to our response to Generic
)
Letter 92-01, Revision 1, Supplement 1 (hereafter Supplement 1), Reference (c). Supplement I
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requested that licensees identify, collect and report any new data pertinent to the analysis of the structural integrity of their RPVs and to assess the impact of that data on their RPV integrity j
analyses relative to the requirements of 10 CFR 50.60,10 CFR 50.61, Appendices G and H to 10 CFR 50 (which encompass pressurized thermal shock (PTS) and upper shelf energy (USE) evaluations) and any potential impact on low temperature overpressure (LTOP) limits or pressure-temperature (P-T) limits. North Atlantic has reviewed the information provided in the
. CEOG report and its relevance to Seabrook Station's RPV structural integrity evaluations and documents the results of this re view herein.
Discussion Subsequent to North Atlantic's submittal of its response to Supplement 1, Reference (c), our second RPV surveillance program capsule has been retrieved and evaluated. The summary
- technical report pursuant to the requirements of 10 CFR 50 Appendix H for the second i
surveillance capsule has been submitted to the NRC via Reference (d). The CEOG report was prepared prior to the evaluation of Seabrook Station's second surveillance capsule and hence, does not furnish the latest Seabrook Station specific information The CEOG report summarizes i
the best estimate copper and nickel content in reactor pressure vessel welds fabricated by CE.
Seabrook's RPV beltline region welds were made using Weld Wire Heat No. 4P6052. A review of the best estimate weld chemistries for the subject heat number suggested by the CEOG report
- and those submitted by North Atlantic in References (c) and (d) indicates an insignificant level of variability. Correspondingly, the resultant Chemistry Factors (CF) used in the assessment of Seabrook Station's RPV structural integrity and as determined by Table 1 of Regulatory Guide (RG) 1.99 Revision 2 also exhibit insignificant variability, approximately 3.5 percent. This effect is attributed to the very low copper and nickel content in Seabrook Station's RPV beltline weldments. Also, nr allowed by RG 1.99 Rev. 2 and reported in Reference (d), the ARta curve
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for the weldment was developed (fitted) based on the fact that North Atlantic now, has available, Pane 1 of 6 r
two " credible" surveillance data points. Based on that curve fit, the corresponding fitted CF is considerably less than half that which would result if calculated using Table 1 of RG 1.99 Rev. 2 for the weld chemistries reported in References (b) and (c). Therefore, it is concluded that the best estimate copper and nickel content for Weld Wire I-leat No. 4P6052 as suggested by the CEOG report will have no discernible impact on the fracture toughness evaluation of the Seabrook Station's RPV.
l it is also noted herein that the limiting material in the Seabrook Station RPV behline region is the lower shell plate designated as R1808-3, not the weld material as discussed above. As indicated in Reference (d), the fitted art a, curve for the subject plate material is also within the n
bounds predicted by Equation 2 of RG 1.99 Rev. 2.
This further corroborates the good correlation between the surveil!ance material chemistries and the RPV beltline material 1
chemistries reported in References (c) and (d).
In response to Reference (a), North Atlantic is submitting via enclosure to this letter the requested information relative to Seabrook Station's RPV structural integrity evaluation parameters. As previously stated, the limiting material in the Seabrook RPV beltline region is the lower shell plate R1808-3 not the welds. Accordingly, the requested in'brmation for the plate R1808-3 is also being provided. In addition, the enclosed tables not only include the art a, n
based on the material CFs generated by the surveillance capsule report, Reference (d), but also the art a, based on the material CFs prescribed by Tables I and 2 of RG 1.99 Rev. 2. This was n
done for comparative purposes and to illustrate that the surveillance data is well within the bounds of RG 1.99 Rev. 2 predictions.
Conclusion In summary, North Atlantic concludes that the chemistry and material property data currently utilized to confirm the structural integrity of the Seabrook Station RPV remains valid and conservative. The data provided in the attached enclosure demonstrates continued compliance with the requirements of 10 CFR 50.60,10 CFR 50.61 and Appendices G and 11 to 10 CFR 50.
In North Atlantic's response to Supplement 1, Reference (c), it was stated that the application of j
l the conservative calculational methodologies of RG 1.99 Rev. 2 to the new (i.e., averaged with sisterplants) results in the reduction of applicability of the Pfr limit curves and the RCS cold overpressure protection setpoint curve to 7.3 EFPY (from 11.1 EFPF). Ilowever with the current availability of the sumtrary technical report for the second surveillance capsule, Reference (d),
l and employing calculational methodologies afforded by RG 1.99 Rev. 2 when two or more
" credible" data points exits, it has been determined the applicability of the subject curves will be a minimum of 11.1 EFPY.
Therefore, the existing Technical Specification RPV pressure / temperature limit curves continue to maintain operational conservatism.
Page 2 of 6
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l References.
l (a) NRC Letter dated March 31, 1998, C. W. Smith to T. C. Feigenbaum, " Request for L
Additional Information Regarding Reactor Pressure Vessel Integrity at Seabrook Station (TAC No, MA0571)"
(b) Combustion Engineering Owners Group (CEOG) Report dated June 1997, CE NPSD-1039, Revision 02, Final Report, "Best Estimate Copper and Nickel Values in CE Fabricated Reactor Vessel Welds" (c) NYN-95094 dated November 20, 1995, B.L. Drawbridge to U.S. NRC, " Response to Generic Letter 92-01, Revision 1, Supplement 1, Reactor Vessel Structural Integrity (TAC M83512)"
(d) NYN-98078 dated June 5,1998, T. C. Feigenbaum to U. S. NRC," Seabrook Station Reactor Vessel Surveillance Capsule Report" i
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