ML20086R183
| ML20086R183 | |
| Person / Time | |
|---|---|
| Site: | Calvert Cliffs  |
| Issue date: | 07/24/1995 |
| From: | Denton R BALTIMORE GAS & ELECTRIC CO. |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| References | |
| GL-92-01, GL-92-1, NUDOCS 9507310048 | |
| Download: ML20086R183 (7) | |
Text
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Rostar E. Drxrom Baltimore Gas and Electric Company Vice President Calvert Oiffs Nuclear Power Plant Nelear Energy 1650 Calvert Cliffs Parkway Lusby, Maryland 20657 410 586-2200 Ext.4455 lual 410 260-4453 Baltimore July 24,1995 U. S. Nuclear Regulatory Commission Washington, DC 20555 ATTENTION:
Document Control Desk
SUBJECT:
Calvert Cliffs Nuclear Power Plant Unit Nos.1 & 2; Docket Nos. 50-317 & 50-318 Response to Generic Letter 92-01, Revision 1, Supplement 1: Reactor Vessel Intenrity
REFERENCES:
(a)
NRC Generic Letter 92-01, Revision 1,
Supplement 1,
from Mr. R. P.Zimmerman (NRC) to All Holders of Operating Licenses (except those licenses that have been amended to possession-only status) or Construction Permits for Nuclear Power Reactors, dated May 19,1995, " Reactor Vessel Structural Integrity" He Nuclear Regt.htery Commission issued Supplement 1 to Generic Letter 92-01, Revision 1 (Reference a) 'to require : hat all addressees identify, collect and report any new data pertinent to analysis of structural integrity of th:ir reactor pressure vessels and to assess the impact of that data on their reactor pressure vessel integrity 'malyses
. " The generic letter requests all addressees to submit a written response provi&g the ;equired information as follows:
1.
Within 90 days from the date of the generic letter, a written response to Part (1) of the information requirement specified in the generic letter; and 2.
Within six months from the date of the generic letter, a written response to Parts (2), (3), and (4) of the information requirement in the generic letter.
Prior to the issuance of the supplement to the generic letter, Baltimore Gas and Electric Company (BGE) had been actively engaged in an extensive search of all relevant data for Calver: CEffs reactor pressure vessel integrity analysis. We believe we have already identified, located and reported to the NRC all currently available information affecting the structural integrity of the Cahrert Cliffs reactor vessels. New information will cor>tinue to become available over the coming years, especially from reactor vessel surveillance capsule analyses. Ilowever, our current best-estimate calculations are based on a broad base 9507310048 950724
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. of data, and we do not believe that any one new data point will significantly change our current projections.
nerefore, the attachment to this letter contains BGE's response to all four parts of the ' Required Information "
No commitment resulted from BGE's response to Supplement I to Generic Letter 92.01, Revision 1.
Should you have questions regarding this matter, we will be pleased to discuss them with you.
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j Attachment BGE's Response to NRC Generic Letter 92.01, Revision 1, Supplement 1: Reactor Vessel -
Integrity cc:
D. A. Brune, Esquire l
J. E. Silberg, Esquire L. B. Marsh, NRC D. G. Mcdonald, Jr., NRC T. T. Martin, NRC i
l P. R. Wilson, NRC R. I. McLean, DNR J. H. Walter, PSC l
J l
4 '
ATTACHMENT t
BGE's Response to NRC Generic Letter 92-01, Revision 1, Supplement 1:
Reactor Vessel Integrity Baltimore Gas & Electric Company Docket Nos. 50-317 and 50-318 July 24,1995
ATTACIIMENT NGE's Response to NRC Generic Letter 92-01, Revision 1, Supplement 1:
Reactor Vessel Integrity Reauired Information Part (1):
Provide a description of those actions taken or planned to locate all data relevant to the determination of reactor pressure vessels integrity, or an explanation of why the existing data base is considered complete as previously submitted.
Response
Prior to the issuance of the supplement to the generic letter, BGE had searched extensively for any data relevant to Calvert Clifts reactor vessel structural integrity evaluations. Initially, these searches were conducted unilaterally by BGE with the cooperation of ABB/ Combustion Engineering (ABB/CE). In the 1980s, BGE discovered that the limiting weld material for its Calvert Cliffs Unit 1 (CC-1) reactor vessel is contained in the Duke Power Company's McGuire Unit I surveillance program. In 1988, BGE established a supplemental reactor vessel surveillance program by obtaining archive weld material from the McGuire Unit I surveillance program (Reference 1). In 1993, BGE provided justification and received approval from the NRC to use the McGuire irradiated surveillance data for CC-1 reactor vessel fracture toughness analysis (Reference 2).
In 1992, BGE joined the ABB/CE Reactor Vessel Group (RVG), which was formed with the primary objective of helping member organizations identify fabrication records of their CE-fabricated reactor pressure vessels. Through the RVG effort, BGE has been able to identify several reactor vessel welds that were fabricated from the same heats of weld wire, types of weld flux, and by using the same welding processes as Calvert Cliffs' reactor vessels. The RVG mission is now complete and a final report on its findings has been published. Baltimore Gas and Electric Company also participated in an ABB/CE Owners Group (CEOG) task (CEOG Task 781) that performed a quantitative evaluation of reactor vessel i
weld chemistry variability for reactor vessels fabricated by CE at its Chattanooga, Tennessee shop. This task is also completed and a report has been issued. Baltimore Gas and Electric Company hr.s incorporated all new pertinent data from both the CEOG task and the RVG reports into the Calvert Cliffs reactor vessel integrity evaluations.
In addition, BGE has obtained information directly from other utilities with reactor vessels that were identified by the RVG as having welds similar to Calvert Cliffs' reactor vessel welds. General Electric Company has provided BGE with a small sample of archive surveillance test block from Boston Edison's Pilgrim Nuclear Station. Baltimore Gas and Electric Company also purchased several large segments of the now decommissioned Shoreham reactor vessel from Long Island Lighting Company, while the reactor vessel was being disassembled for removal. The Shoreham material in particular provided valuable weld samples for four of the five unique beltline welds at Calvert Cliffs. In response to an NRC request for additional information regarding BGE's response to the original Generic Letter 92-01, the weld obtained from the Shoreham reactor vessel was used to establish an unirradiated upper shelf energy value for CC-1 Weld Scams 3-203-A,B,C (Reference 3). Finally, BGE has also obtained surveillance data from Farley Unit 1, which shares a common weld with both Cah ert Cliffs' reactor vessels.
The actual weldments which were obtained from Pilgrim and Shoreham were thoroughly analyzed to determine their chemical composition. The analysis included taking a wide range of samples to determine the chemical content and variability, and to perform several staticical tests on the resulting data. The chemical analysis results were combined with existing chemistry information from Calvert Cliffs own 1
1 1
ATTACHMENT 3
i BGE's Response to NRC Generic Letter 92-01, Revision 1, Supplesment 1:.
Resetor Vessel Integrity reactor vessel surveillance program, and with the chemical analyses reported by the RVG and CEOG i
Task 781 to compute best-estimate chemistry values for all Calvert Cliffs reactor vessel welds. De chenucal analysis of the Shoreham and Pilgrim welds and the Calvert Cliffs updated best-estunate i
chemistry values were recently reported to the NRC as past of a pressurized thermal shock (PTS) update required by 10 CFR 50.61 (Reference 4).
Baltimore Gas and Electric Company's participation in owners group activities, such as the ABB/CE RVG described above, has enabled BGE to retrieve all currently availabic information pertment to Calvert Cliffs l
reactor vessel integrity evaluation. Baltimore Gas and Electric Company continues to participate in all relevant reactor vessel-related industry activities. Currently, we are participating in the newly-formed CEOG Reactor Vessel Working Group (RVWG). The RVWG was formed to coordinate the resolution of reactor vessel integrity issues affecting CE-fabricated reactor vessels. We understand that this group has I
proposed a task to address portions of Supplement I to Generic Letter 92-01. In the proposed task,.
ABB/CE would perform additional searches of their manufacturing records, beyond the scope ~of the RVG effort, to ensure that all available data has been located. However, BGE considers that it now has in its possession enough manufacturing records to ensure high confidence in reactor vessel integrity evaluations.
j This includes chemical composition measurements, heat treatment and manufacturing process records, and -
l all available mechanical property and surveillance data.
l New information will continue to become available over the coming years. : For example, the proposed i
CEOG RVWG task discussed above and each new surveillance capsule removed from a reactor vessel may provide data that could impact reactor vessel fracture toughness projections. However, since our current i
best estimate calculations are based on a broad base of data, we do not believe that any one new data point will significantly change our current projections.
Reauired Information Part (2):
Provide an assessment of any change in best-estimate chemistry based on consideration of all relevant data.
.I
Response
f The best-estimate chemistry value for Calvert Cliffs reactor vessel plate material has not been affected by the newly acquired information. Only the best-estimate chemistry values for weld material were affected.
l ne recently updated Calvert Cliffs PTS projections (Reference 4) prosided resised best-estimate chemistry values for all CC-1 and Calvert Cliffs Unit 2 (CC-2) reactor vessel welds. In all cases, the resulting PTS projections were lower than had been previously calculated.
2
ATTACHMENT 8GE's Response' to NRC Gener*e Letter 92-01, Revision 1, Supplement 1:
Reactor Vessel Integrity Reauired Information Part (3):
l Provide a determination of the needfor use of the ratio procedure in accordance with the i
established Position 2.1 of Regulatory Guide 1.99, Revision 2, for those licensees that use surveillance data to provide a basisfor the reactorpressure vesselintegrity evaluation.
Response
Baltimore Gas and Electric Company used surveillance data to calculate RTm values for three weld and two plate materials (Reference 4). Therefore, the ratio procedure of Position 2.1 of Regulatory Guide 1.99, Revision 2, was applied to all surveillance measurements. In all cases, the procedure resulted in minimal changes to the best-fit chemistry factors.
Reauired information Part (4):
Provide a written report providing any newly acquired data as specified above and (1) the results of any necessary revisions to the evaluation of reactor pressure vessel integrity in accordance with the requirements of 10 CFR 50.60,10 CFR S0.61, Appendices G and H to 10 CFR Part 30, and any potential impact on the low temperature overpressure protection or pressure and temperature limits in the technical specifications; or (2) a certipcation that previously submitted evaluations remain valid. Revised evaluations and certifications should include consideration ofPosition 2.1 or Regulatory Guide 1.99, Revision 2, as applicable, and any new data.
Response
As explained in the response to Part (1) above, by Reference (4), BGE has provided a written report to the NRC updating the 10 CFR 50.61 pressurized thermal shock (PTS) projections using the newly acquired data. The updated PTS projections confirmed that both Calvert Cliffs reactor vessels will remain below the 10 CFR 50.61 screening criteria for a period exceeding 20 years beyond the current 40-year operating license. Furthermore, BGE certifies that, subject to those corrections previously docketed, all other previously submitted reactor vessel evaluations remain valid.
3
s ATTACHMENT
- BGE's Response to NRC Genene Letter 92-01, Revision 1, Supplement 1:
Reactor Vessel Integrity
References:
(1) letter from Mr.
R.
E.
Denton (BGE) to Document Control Desk (NRC), dated November 29,1993, Request for Approval to Use Plant-Specific Data for Reactor Vessel Fracture Toughness Analysis (2)
Letter from Mr. M. L. Boyle (NRC) to Mr. R. E. Denton (BGE), dated July 29,1994, Request For Approval To Use Plant Specific Data For Reactor Vessel Fracture Toughness Analysis, Calvert Cliffs Nuclear Power Plant, Unit No.1 (3)
Letter from Mr. R. E. Denton (BGE) to Document Control Desk (NRC), August 30, 1994, Generic Letter 92-01, ' Reactor Vessel Structural Integrity" Close-out Ixtter/ Upper-Shelf Energy for Weld Scams 3-203-A,B,C (TAC No. M83446)
(4)
Letter from Mr. R. E. Denton (BGE) to Document Control Desk (NRC), dated July 21, 1995, Request for Approval of Updated Values of Pressurized Thermal Shock (PTS) Reference Temperature (RTrrs) Values (10 CFR 50.61) 4