ML16342E045
| ML16342E045 | |
| Person / Time | |
|---|---|
| Site: | Diablo Canyon  |
| Issue date: | 04/06/1998 |
| From: | Steven Bloom NRC (Affiliation Not Assigned) |
| To: | Rueger G PACIFIC GAS & ELECTRIC CO. |
| References | |
| GL-92-01, GL-92-1, TAC-MA0541, TAC-MA0542, TAC-MA541, TAC-MA542, NUDOCS 9804070395 | |
| Download: ML16342E045 (20) | |
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UNITED STATES NUCLEAR REGULATORY COMMISSION WASHINGTON> D.C. 205554001 April 6, 1998
'gp-77+~Z3 Mr. Gregory M. Rueger, Senior Vice President and General Manager Pacific Gas and Electric Company Nuclear Power Generation N9B P. O. Box 770000 San Francisco, California 94177
SUBJECT:
REQUEST FOR ADDITIONALINFORMATIONREGARDING REACTOR PRESSURE VESSEL INTEGRITYAT DIABLOCANYON POWER PLANT, UNITS 1 AND 2 (TAC NOS. MA0541 AND MA0542)
Dear Mr. Rueger:
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 and 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 F
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(10 CFR Part 50.60), 10 CFR 50.61, Appendices G and H to 10 CFR Part 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 (PT) limits.
After reviewing your response, the NRC issued you a letter dated August 7, 1996.
In this letter we indicated that you had submitted the requested information and that you indicated that the previously submitted evaluations remained valid. As a result, the NRC concluded that no additional information regarding the structural integrity of your RPV was available at that time.
In July 1997, the Combustion Engineering Owners Group (GEOG) 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.
In consideration of the data presented in the June 1997 GEOG report, the NRC requests that you confirm that your original response is still correct. The comments in the enclosed request for additional information (RAI) should be considered in the assessment of your original submittal.
Ifthe report does include data that would alter your original evaluation and in order to provide a complete response to items 2, 3 and 4 of the GL, the NRC requests that you provide a response to the enclosed request for additional information within 90 days of receipt of this letter. Ifa 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 willbe used in updating the Reactor Vessel Integrity Database (RVID). Also, please 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 9804070395 980406 PDR ADQCK05000275 a@~i CIHIItl'&lCSPIF l)W(
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Mr. Gregory M. Rueger April 6, 1998 to address any potential impact on low temperature overpressure (LTOP) limits or pressure-temperature (PT) limits. Ifadditional license amendments or assessments are necessary, the enclosure requests that you provide a schedule for such submittais.
Ifyou should have any questions regarding this request, please contact me at (301) 415-1313.
Sincerely, ORIGINAL SIGNED BY'teven D. Bloom, Project Manager Project Directorate IV-2 Division of Reactor Projects III/IV Office of Nuclear Reactor Regulation Docket Nos. 50-275 and 50-323
Enclosure:
Request for Additional Information cc w/encl: See next page
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. Docket PUBLIC PDIV-2 Reading EAdensam WBateman SBloom DLoveless EPeyton OGC ACRS KPerkins, RIVWCFO PGwynn, RIV AHiser, EMCB GVissing Document Name: Vessel.dc OFC PDIV PDIV-2 PDIV-2 NAME DLove s
- eyon, SBloo DATE 4/ 0 /98 4/B/98 4/0 /98 OFFICIAL RECORD COPY
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Mr. Gregory M. Rueger to address any potential impact on low temperature overpressure (LTOP) limits or pressure-temperature (PT) limits. Ifadditional license amendments or assessments are necessary, the enclosure requests that you provide a schedule for such submittals.
Ifyou should have any questions regarding this request, please contact me at (301) 415-1313.
Sincerely, Steven D. Bloom, Project Manager Project Directorate IV-2 Division of Reactor Projects III/IV Office of Nuclear Reactor Regulation Docket Nos. 50-275 and 50-323
Enclosure:
Request for Additional Information cc w/encl: See next page
Mr. Gregory M. Rueger cc w/encl:
NRC Resident Inspector Diablo Canyon Nuclear Power Plant do U.S. Nuclear Regulatory Commission P. O. Box 369 Avila Beach, California 93424 Regional Administrator, Region IV U.S. Nuclear Regulatory Commission Harris Tower 8 Pavillion 611 Ryan Plaza Drive, Suite 400 Arlington, Texas 76011-8064 Dr. Richard Ferguson, Energy Chair Sierra Club California 1100 11th Street, Suite 311 Sacramento, California 95814 Christopher J. Warner, Esq.
Pacific Gas & Electric Company Post Office Box 7442 San Francisco, California 94120 Ms. Nancy Culver San Luis Obispo Mothers for Peace P. O. Box 164 Pismo Beach, California 93448 Mr. Robert P. Powers Vice President and Plant Manager Diablo Canyon Nuclear Power Plant P. O. Box 56 Avila Beach, California 93424 Chairman San Luis Obispo County Board of Supervisors Room 370, County Government Center San Luis Obispo, California 93408 Telegram-Tribune ATTN: Managing Editor 1321 Johnson Avenue P.O. Box 112 San Luis Obispo, California 93406 Mr. Truman Burns Mr. Robert Kinosian California Public Utilities Commission 505 Van Ness, Room 4102 San Francisco, California 94102 Mr. Steve Hsu Radiologic Health Branch State Department of Health Services Post Office Box 942732 Sacramento, California 94232 Diablo Canyon Independent Safety Committee ATTN: Robert R. Wellington, Esq.
Legal Counsel 857 Cass Street, Suite D Monterey, California 93940
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The staff recently received additional information that may affect the determination of the best-estimate chemistry composition for your RPV welds or your surveillance weld material. This information was provided to the NRC by the Combustion Engineering Owners'roup 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 fillout the data requested in Table 1 for each RPV beltline weld material.
Also provide 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.
Ifthe 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 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 the evaluation of the data were discussed in a public meeting between the staff, NEI, and industry representatives on November 12, 1997. A summary of this meeting is documented. in a meeting summary dated November 19, 1997, "Meeting Summary for November 12, 1997 Meeting with Owners Group Representatives and NEI 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 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 coil-weighted average approach is determined to be the appropriate method for determining the best-estimate chemistry.
Ifa weld (or welds) were fabricated as weld qualification specimens by the same manufacturer, within a short time
y span, using similar welding input parameters, and using the same coil (or coils in the case of tandem arc welds) of weld consumables, it may be appropriate to consider all chemistry samples from that weld (or welds) as samples from "one weld" for the purposes of best-estimate chemistry determination.
Ifinformation is not available to ggofjZm 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 came from an appropriate number of "multiple welds". Ajustification should then be provided for which assumption was chosen when the best-estimate chemistry was determined.
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The chemical composition report referenced in Section 1.0 includes updated chemistry estimates for heats of weld metal. These reports not only provide a suggested best estimate value but also include the source 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 (including 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:
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 ~ 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.
Ifthe 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 (ifsurveillance 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.
Allsurveillance 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."). Ifany of the 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.
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C When assessing credibility of surveillance data that come from more 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. Ifthe method for adjusting and/or normalizing the surveillance data when assessing credibility differfrom the methods documented in Reference 1, provide the technical basis for the adjustment and/or the
.normalization procedure.
Ifthe chemical compositions 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 determining 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 RT>> 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 RT>>. Position 1.1 describes the use of the Generic Tables in the Regulatory Guide.
Position 2.1 describes the use of credible surveillance data.
Ifthe 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.
Ifthe evaluation of the surveillance data indicate that the surveillance data set is not credible and the measured values of h,RT>>,
are less than the projected mean from the Tables plus the generic 2o~, the chemistry factor may be calculated using either Position 1.1 or Position 2.1; however, the full margin term must be applied. The method chosen must bound all the surveillance data to be in compliance with 10 CFR 50.61(c)(2).
Based on the information provided in Table 2 along with the best estimate chemical composition of the heat of material and the irradiation temperature of the plant whose vessel is being assessed, the chemistry factor of the RPV weld can be determined.
Note that the adjusted ARTS>> for a particular 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.
Ifthe 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.
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 BRTgpy 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 from the average for the weld wire heat number associated with the vessel weld and the surveillance weld, the ratio procedure must be used.
ti n L'Evl i
3.
Ifthe limiting material for your plant changes or ifthe adjusted reference temperature for the limiting material increases as a result of the above evaluations, provide the revised RT~8 value for the limiting material in accordance with 10 CFR 50.61.
In addition, ifthe adjusted RT>> 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.
H~frerrgg 1.
'emorandum from Keith R. Wichman to Edmund J. Sullivan, "Meeting Summary for November 12, 1997 Meeting with Owners Group Representatives and NEI 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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TABLE 1 Facility:
Vessel Manufacturer:
Information requested on RPV Weld and/or Limiting Materials RPV Best-Weld Wire Estimate Heat <"
Copper Best-Estimate Nickel EOL ID Fluence (x 10")
Assigned Material Chemistry Factor (CF)
Method of Determining CF(')
Initial RT>>
(RT~>><ui) o~
Margin ART or RT~8 at EOL (1) or the material identification of the limiting material as requested in Section 1.0 (1.)
(2) determined from tables or from surveillance data D'onofth An I
i eth dandDataU dforEachW IdWir at W Id Wire He t
~Di c ~lysin Attachment 1
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Table 2: Heat xxxx Capsule ID (including source)
Cu Ni Irradiation Temperature
('F)
Fluence (x10"n/cm')
Measured hRTggr
('F)
Data Used in Assessing Vessel (Yor N)
Table 3: Heat xxxx Capsule ID (induding source)
Cu Ni irradiation Temperature
('F)
Fluence Factor Measured hRT~)r
('F)
Adjusted hRT~r
('F)
Predicted b RT~)r
('F)
(Adjusted-Predicted) AT~,
('F)
'1 i