ML20216C373
| ML20216C373 | |
| Person / Time | |
|---|---|
| Site: | Callaway  |
| Issue date: | 04/09/1998 |
| From: | Westreich B NRC (Affiliation Not Assigned) |
| To: | Randolph G UNION ELECTRIC CO. |
| References | |
| GL-92-01, GL-92-1, TAC-MA0531, TAC-MA531, NUDOCS 9804140403 | |
| Download: ML20216C373 (9) | |
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k UNITED STATES g
.j NUCLEAR REGULATORY COMMISSION WASHINGTON, D.C. 30006-0001 g
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April 9, 1998 g%.. j Mr. Garry L. Randolph Vice President and Chief Nuclear Officer i
Union Electric Company Post Office Box 620 J
Fulton, Missouri 65251
SUBJECT:
REQUEST FOR ADDITIONAL INFORMATION REGARDING REACTOR PRESSURE VESSEL INTEGRITY AT CALLAWAY PLANT (TAC NO. MA0531)
I
Dear Mr. Randolph:
Generic Letter (GL) 92-01, Revision 1 Supplement 1 (GL 92-01, Rev.1, Supp.1), " Reactor Vessel Structural Integrity" was issued in May 1995. This GL requested licensees to perform a review of their reactor pressure vessel (RPV) structural integrity assessments in order to identify, collect, and report any new data pertinent to the analysis of the structural integrity of their RPVs smd to assess the impact of those data on their RPV integrity analyses relative to the requirements of Section 50.60 of Title 10 of the Code of Federal Regulations (10 CFR Part 50.60),'10 CFR 50.61, Appendices G and H to 10 CFR Part 50 (which encompass pressurized j
thermal sho::k (PTS) and upper shelf energy (USE) evaluations), and any potential impact on low temperature overpressure (LTOP) limits or pressure-temperature (PT) limits.
After reviewing your response, the NRC issued you a letter dated August 2,1996. In this letter we acknowledged receipt of your response, noted that additional RPV information may become j
available as a result of Owners Group efforts, and requested that you provide us with the results of the Owners Groups' programs relative to your plant. We further indicated that a i
plant-specific TAC Number may be opened to review this material. In July 1997, the j
Combustion Engineering Owners Group (CEOG) provided a report with additional RPV weld chemistry data for RPVs fabricated by CE. This additional RPV weld chemistry data may affect previous RPV integrity analyses supplied.by licensees with CE fabricated RPVs. As a follow-up to the letter and the CEOG report, and in order to provide a complete response to items 2,3 -
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i and 4 c.f the GL, the NRC requests that you provide a response to the enclosed request for
/ I additionalinformation within 90 days of receipt of this letter, if a question does not apply to your situation, please indicate this in your RAI response along with your technical basis and, per GL 92-01, Rev.1, Supp.1, provide a certification that previously submitted evaluations remain valid.
The information provided will be used in updating the Reactor Vessel integrity Database
_ (RVID). Also, phase note that RPV integrity analyses utilizing newly identified data could result in the need for license amendments in order to maintain compliance with 10 CFR Part 50.60,10 CFR 50.61 (pressurized thermal shock, PTS), and Appendices G and H to 10 CFR Part 50, and to address any potential impact on low temperature overpretsure (LTOP) limits or pressure-temperature (PT) limits. If additionallicense amendments or assessments are necessary, the enclosure requests that you provide a schedule for such submittals.
k 9804140403 980409 PDR ADOCK 05000483 P
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1' Mr. Garry L. Randolph Apri1 9,1998
~ If you should have any questions regarding this request, please contact me at (301) 415-3456.
Sincerely, Original Signed By Barry C. Westreich, Project Manager Project Directorate IV-2 Division of Reactor Projects Ill/IV Office of Nuclear Reactor Regulation Docket No. 50-483 DISTRIBUTION:
Docket
Enclosure:
Request for Additional Information PUBLIC PDIV-2 Reading cc w/enci: See next page EAdensam WBateman BWestreich DLoveless
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EPeyton j
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ACRS PGwynn, Region IV
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i Document Name: vessel. cal OFC PDIV-A /f PDIV EDIV-2 NAME DLoveYsh EPe"yh BMVeich DATE 4 /l /98 4 F? /98 4 / 9 /98 f
OFFICIAL RECORD COPY l
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Mr. Garry L. Randolph April 9,1998 cc w/ encl:
Professional Nuclear Mr. Otto L. Maynard
. Consulting. Inc.
President and Chief Executive Officer 19041 Raines Drive Wolf Creek Nuclear Operating Corporation Derwood, Maryland 20855 P.O. Box 411 Burlington, Kansas 66639 Gerald Chamoff, Esq.
Thomas A. Baxter, Esq.
Mr. Dan 1. Bolef, President i
Shaw, Pittman, Potts & Trowbridge Kay Drey, Representative 2300 N. Street, N.W.
Board of Directors Coalition Washington, D.C. 20037 for the Environment j
6267 Delmar Boulevard Mr. H. D. Bono University City, Missouri 63130 l
Supervising Engineer Quality Assurance Regulatory Support Mr. Lee Fritz Union Electric Company
. Presiding Commissioner Post Office Box 620 Callaway County Court House Fulton, Missouri 65251 10 East Fifth Street Fulton, Missouri 65151 l
U.S. Nuclear Regulatory Commission j
l Resident inspector Office Mr. Alan C. Passwater, Manager
. 8201 NRC Road Licensing and Fuels
[
Steedman, Missouri 65077-1302 Union Electric Company i
Post Office Box 66149 Mr. J. V. Laux, Manager -
St. Louis, Missouri 63166-6149 l
Quality Assurance j
Union Electric Company Post Office Box 620 Fulton, Missouri 65251 Manager - Electric Department j
l Missouri Pubhc Service Commission 301 W. High Post Office Box 360 Jefferson Cit /, Missouri 65102 l-
. Regional Administrator, Region IV L
U.S. Nuclear Regulatory Commission l
Harris Tower & Pavilion R
611 Ryan Plaza Drive, Suite 400 Arlington, Texas 76011-8064 Mr. Ronald A. Kucera, Deputy Director Department of Natural Resources P.O. Box 176 Jefferson City, Missouri 65102
v REQUEST FOR ADDITIONAL INFORMATION REACTOR PRESSURE VESSEL INTEGRITY UNION ELECTRIC COMPANY CALLAWAY Pl. ANT. LINIT 1 DOCKET NO. 50-483 Sechon 1.0 - Assessment of Best-Estimata Chemistry
- The staff recently received addihonalinformation that may affect the determination of the best-estimate chsmistry composition for your RPV welds or your surveillance weld material. This
- information was provided to the NRC by the Combustion Engineering Owners' Group in report CE NPSD-1039, Revision 02, "Best Estimate Copper and Nickel Values in CE Fabricated Reactor Vessel Welds," dated June 1997.
Based on this information, in accordance with the provisions of Generic Letter 92-01, Revision 1, Supplement 1, the NRC requests the following:
1, An evaluation of the information in the reference above and an assessment of its applicability to the determination of the best-estimate chemistry for all of your RPV beltline welds. Based upon this reevaluation, supply the information necessary to completely fill out the data requested in Table 1 for each RPV beltline weld material.
Also provida a discussion for the copper and nickel values chosen for each weld wire heat noting what heat-specific data were included and excluded from the analysis and the analysis method chosen for determining the best-estimate if the limiting material for your vessel's PTS /PT limits evaluation is not a weld, include the information requested in Table 1 for the limiting material also. Furthermore, you should consider the -
I information provided in Section 2.0 of this RAI on the use of surveillance data when responding.
With respect to your response to this question, the staff notes that some issues regarding te evaluation of the data were discussed in a public meeting between the staff, NEl, and industry representatives on November 12,1997. A summary of % meeting is documented in a meeting summary dated November 19,1997, " Meeting tiummary for November 12,1997 l
Meeting with Owners Group Representatives and NEl Regarding Review of Responses to Generic Letter 92-01, Revision 1, Supplement 1 Responses" (Reference 1). The information in Reference 1 may be useful in helping you to prepare your response.
In addition to the issues discussed in the referenced meeting, you should also consider what l
method should be used for grouping sets of chemistry data (in particular, those from weld qualification tests) as being from "one weld" or from multiple welds. This is an important consideration when a mean-of-the-means or coll weighted average approach is determined to be the appropnate method for determining the best-estimate clamistry. If a weld (or welds) were fabricated as weld qualification specimens by the same manufacturer, within a short time
2-span, using similar welding input parameters, and using the same coil (or coils in the case of tandem arc welds) of wold consumables, it may be appropriate to consider all chemistry samples from that weld (or wolds) as samples from "one weld" for the purposes of best-estimate chemistry determination. If information is not available to mofkm the aforementioned details, but sufficient evidence exists to reasonably assume the details are the same, the best-estimate chemistry should be evaluated both by assuming the data came from "one weld" and by assuming that the data come from an appropriate number of " multiple welds". A Justification should then be provided for which assumption was chosen when the best-estimate chemistry was determined.-
Section 2.0 - Evaluation and Une of Surveillance Data The chemical composition report referenced in Section 1.0 includes updated chemistry estimates for heats of weld metal. These reports provide information regarding a best estimate value and the source of the data used in estimating the chemical composition of the heat of material. This permits the determination of the best estimate chemical composition for the various sources of data including surveillance welds. Since the evaluation of surveillance data rely on both the best estimate chemical composition of the RPV weld and the surveillance weld, the information in these reports may result in the need to revise previous evaluations of RPV integrity (hcluding LTOP setpoints and PT limits) per the requirements of 10 CFR 50.60, 10 CFR 50.61, and Appendices G and H to 10 CFR Part 50.
Based on this information and consistent with the provisions of Generic Letter 92-01, Revision 1, Supplement 1, the NRC requests the following:
2.
that (1) the information listed in Table 2 Table 3, and the chemistry factor from the surveillance data be provided for each heat of material for which surveillance weld data are available and a revision in the RPV integrity analyses (i.e., current licensing basis) is needed or (2) a certification that previously submitted evaluations remain valid.
Separate tables should be used for each heat of material addressed. If the limiting material for your vessel's PTS /PT limits evaluation is not a weld, include the information requested in the tables for the limiting material (if surveillance data are available for this material).
The information discussed in Section 1.0 of this RAI regarding the chemistry reports should be considered in this response along with the following questions and comments.
All surveillance program results for the heats of material in a RPV should be considered in evaluating its integrity regardless of source per 10 CFR 50.61 (" Surveillance program results means any data that demonstrates the embrittlement trends for the limiting beltline material, including but not limited to data from test reactors or from surveillance programs at other plants with or without surveillance program integrated per 10 CFR 50, Appendix H."). If any of the
e.
. data provided in Table 2 are not used in the calculation of the embrittlement trend for a particular RPV weld, the technical basis for not including /using the data should be provided.
When assessing credibility of surveillance data that come from rnore than one source, adjustments to the surveillance data may be needed to account for differences in the chemical composition and irradiation environment of the different sources consistent with the requirements in 10 CFR 50.61. A method for accounting for these differences is discussed in Reference 1.
Based on the information provided in Table 2, the credibility of the surveillance data can be evaluated. The results of these analyses including the slope of the best fit line through the surveillance data can be provided in a format similar to that of Table 3. If the method for adjusting and/or normalizing the surveillance data when assessing credibility differ from the
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methods documented in Reference 1, provide the technical basis for the adjustment and/or the normalization procedure. If the chemical cc,Tvesition of the surveillance weld is not determined in accordance with Reference 1 (i.e., the mean of all chemistry analyses performed on the surveillance weld), provide the technical basis for the estimate.
When detemiining the chemistry factor for a RPV weld from surveillance data, adjustments to the surveillance data may be needed to account for differences in the chemical composition and irradiation environment between the surveillance specimens and the vessel being assessed consistent with the requirements in 10 CFR 50.61. A method to account for these differences is provided in Reference 1.
In addition,10 CFR 50.61(c)(2) specifies that licensees shall consider plant-specific information -
(e.g., operating temperature and surveillance data) to verify that the RTum for each vessel beltline material is a bounding value. Regulatory Guide 1.99, Revision 2 describes two methods for determining the amount of margin and the chemistry factor used in determining RTum. Position 1.1 describes the use of the Generic Tables in the Regulatory Guide.' Position 2.1 describes the use of credible surveillance data.. If the surveillance data are credible, the o, may be reduced in half to calculate the margin term and the chemistry factor is to be determined from the best-fit line of the surveillance data, if the evaluation of the surveillance data indicate that the surveillance data set is not credible and the measured values of ARTum are less than the projected mean from the Tables plus the generic 20, the chemistry factor 3
may be calculated using either Position 1.1 or Position 2.1; however, the full margin term must i
be applied. The method chosen must bound all the surveillance data to be in compliance with 10 CFR 50.61(c)(2).
i Based on the information provided in Table 2 along with the best estimate chemical compositen of the heat of material and the irradiation temperature of the plant whose vesselis being assessed, the chemistry factor of the RPV weld can be determined. Note that the adjusted ARTum for a porticular surveillance data point may be one value when determining credibility and another value when determining the chemistry factor as a result of the different normalization procedures, if the method for adjusting and/or normalizing the surveillance data when determining the chemistry factor differs from the methods documented in Reference 1, provide the technical basis for the adjustment and/or the normalization procedure.
a
.. i in a meeting between the staff and industry representatives at the NRC on February 12,1998, an industry representative requested a clarification as to when the ratio procedure should be used to evaluate surveillance data. The ratio procedure is described in the PTS rule and RG 1.99, Revision 2. The ratio procedure is used to adjust the measured value of ART to account for differences in the chemical composition between the surveillance weld and the vessel beltline weld. The PTS rule and RG 1.99, Revision 2 indicate that when there is clear evidence that the copper and nickel content of the surveillance weld differs from the vessel weld, i.e. differs fron 'ha average for the weld wire heat number associated with the vessel weld and the surveillboca weld, the ratio procedure must be used.
Ser* inn 3.0 - PTS /PT Limit Evalum*ian 3.
If the limiting material for your plant changes or if the adjusted reference temperature for the limiting material increases as a result of the above evaluations, provide the revised RTns value for the limiting material in accordance with 10 CFR 50.61, in additen, if the adjusted RTc value increased, provide a schedule for revising the PT and LTOP limits.
The schedule should ensure that compliance with 10 CFR 50 Appendix G is maintained.
Reference 1.
Memorandum from Keith R. Wichman to Edmund J. Sullivan, " Meeting Summary for November 12,1997 Meeting with Owners Group Representatives and NEl Regarding Review of Responses to Generic Letter 92-01, Revision 1, Supplement 1 Responses",
dated November 19,1997.
Attachments: 1. Table 1
- 2. Table 2 and Table 3
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