ML20211L915
| ML20211L915 | |
| Person / Time | |
|---|---|
| Site: | North Anna  |
| Issue date: | 09/01/1999 |
| From: | Hartz L VIRGINIA POWER (VIRGINIA ELECTRIC & POWER CO.) |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| References | |
| 99-361, GL-92-01, NUDOCS 9909090001 | |
| Download: ML20211L915 (10) | |
Text
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4 Visu;INI A Euccruic AND POWER Cm11%NY
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RicustoNo, VnunNia 232r,i September 1, 1999 l
United States Nuclear Regulatory Commission Serial No.99-361 Attention: Document Control Desk NL&OS/GDM R0 4
Washington, D. C. 20555-0001 Docket Nos.
50-338,339 License Nos. NPF 4,7 Gentlemen:
VIRGINIA ELECTRIC AND POWER COMPANY NORTH ANNA POWER STATION UNITS 1 AND 2 i
RESPONSE TO NRC REQUEST FOR COMMENTS GENERIC LETTER 92-01, REVISION 1, SUPPLEMENT 1 Generic Letter (GL) 92-01 Revision 1, Supplement 1, " Reactor Vessel Structural integrity,"
was issued to all nuclear power plant licensees by letter dated May 19,1995. Virginia Electric and Power Company (Virginia Power) provided responses to GL 92-01 Revision 1, Supplement 1, for North Anna Units 1 and 2 by letters dated August 10,1995 (Serial No.95-270) and November 20,1995 (Serial No. 95-270A). The staff completed its review of the two submittals and documented its findings in the NRC's Reactor Vessel Integrity Database (RVID) and in a letter dated June 23,1999. Several discrepancies between the information provided in our November 5,1995, submittal and the staffs analysis were identified.
The staff requested that comments on the identified discrepancies be provided no later than September 1,1999. Consequently, we have evaluated the discrepancies and provided our comments and recommendations for their resolution in the attachment.
Please contact us if you have any questions or require additional information.
Very truly yours, Leslie N. Hartz Vice President - Nuclear Engineering and Services
\\ l' Attachment c-
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~ (f,h' 9909090001 990901 PDR ADOCK 05000338 P
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US Nuclear Regulatory Commission Nuclear Regulatory Commission Region II Atlanta Federal Center 61 Forsyth Street, S.W., Suite 23T85 Atlanta, Georgia 30303 4
1 Mr. M. J. Morgan NRC Senior Resident inspector North Anna Power Station Commitments made in this letter:
1.
In Fall 1999, Virginia Power will be transmitting a surveillance capsule analysis report for North Anna Unit 1 Capsule W.
Subsequent to the provision of this analysis report, Virginia Power will provide an evaluation of the newly acquired data in the form of updated RVID data tables. In addition, these data tables will include
]
l revised reactor vessel fluence values based on the recentiy approved Virginia j
Power fluence analysis methodology topical report.
2.
North Anna Unit 2 Capsule W is scheduled to be withdrawn in Fall 1999. An analysis report and an evaluation of available surveillance data will be provided for North Anna Unit 2 in Fall 2000.
E,-,
COMMONWEALTH OF VIRGINIA
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COUNTY OF HENRICO.
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The foregoing document was acknowledged before me, in and for the~ County and Commonwealth aforesaid, today by Leslie N. Hartz, who is Vice President -
Nuclear Engineering &' Services, of Virginia Electric and Power Company. She has affirmed before me that she is duly authorized to execute and file the foregoing document in behalf of that Company, and that the statements in the document are true to the best of her knowledge an belief.
Acknowledged before me this day of
.1E 33/!OMO My Commission Expires:
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[0LU Notary Public JJ z
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, (SEAL)
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a RESPONSE TO NRC REQUEST FOR COMMENTS CLOSURE OF THE REVIEW OF THE RESPONSE TO GENERIC LETTER 92-01,
. REVISION 1, SUPPLEMENT 1 " REACTOR VESSEL STRUCTURAL INTEGRITY,"
NORTH ANNA POWER STATION UNITS 1 AND 2 BACKGROUND Generic Letter (GL) 92-01 Revision 1 Supplement 1 was issued to all nuclear power plant licensees by letter dated May 19,1995 (2). Virginia Power provided responses to GL 92-01 Revision 1 Supplement 1 by letters dated August 10,1995 (3) and November 20,1995 (4).
The staff completed its review of the Reference (3) and (4) submittals, and documented its findings in the NRC's Reactor Vessel integrity Database (RVID) and in Reference (1). Several discrepancies between the Virginia Power submittal documented in Reference (4) and the staffs analysis were identified.
These discrepancies are described below.
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NRC IDENTIFIED DISCREPANCIES 4
North Anna Unit 1 f
Discrepancy #1 (From Reference (1)): "In your submittals of August 10 and November i
29,1995, for North Anna Unit 1, you considered the surveillance data for lower shell forging 03 to be credible and calculated a chemistry factor (CF) from the surveillance data.
The staff determined that two of the four surveillance data points are not credible; however, all are within the 2-sigma limits using Regulatory Guide Position 1.1. Since two j
4 of the data points are not credible, the staff used the surveillance data to calculate the CF with a full margin value of 34 F to calculate the RTpTs (a second option would have been to use the RG Tables to calculate the CF). Since lower shell forging 03 is not the limiting material, the reactor vessel integrity evaluations are not affected."
Discrepancy #2 (From the RVID PTS Summary Report for North Anna Unit 1): "In the response to GL 92-01, Revision 1, Supplement 1, the licensee indicated that the lower shell forging 03 was the limiting material for North Anna Unit 1. However the staff found that the limiting material is the nozzle to intermediate shell weld 05A. The method of determining RTndt(u) for weld 05A is generic as indicated in the licensee's submittal dated November 20,1995. Therefore, a sigma i value of 20 degrees F and a sigma delta value of 28 degrees F should have been used to calculate a margin of 68.8 degrees F. Using 68.8 as the margin, the staff calculated an RTpts value of 174.6 degrees F. If the staff does not receive comments by September 1,1999, we will assume that the data entered into the RVID are acceptable for North Anna 1."
Discrepancy #3 (From the RVID PTS Summary Report for North Anna Unit 1):
" Based on the docketed information (November 20,1995 letter) for circumferential weld 04 (heat number 25531), the staff calculated a chemistry factor (CF) of 95.2 degrees F using surveillance data and the ratio procedure in Regulatory Guide (RG) 1.99, Revision 2.
The resulting RTpts value is 175.9. The licensee reported a CF value of 93.1 calculated from surveillance data and the ratio procedure. The Ibensee's RT,nts value of 172.9 Page 1 of 7
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degrees F is less conservative than the staff's value. The staff was not able to determine how the licensee calculated this data based on the docketed information. Therefore, if the staff does not receive comments by September 1,1999, we will assume that the data entered into the RVID are acceptable for North Anna 1."
North Anna Unit 2 Discrepancy #4 (From Reference (1)): "In your submittals of August 10 and November 29,1995, for North Anna Unit 2, you reported a CF value of 47.9 F for forging 04 in BAW-2224. This value was based on data from WCAP-12497 (Capsule U data). The staff entered the licensee's CF value as an override to the RVID because this value is conservative. However, if the other available surveillance data are used (Capsule V data),
the resulting CF and RTPTs values are 35.1 F and 157.5 F, respectively. It should be noted that this RTpTs alue results from using the full margin value of 34 F. The full margin value v
is applicable since one out of the four surveillance data points for forging 04 is not credible, but all are within the 2-sigma limits using RG Position 1.1. (As stated above for North Anna Unit 1, a second option would have been to use the RG Tables to calculate the CF.)
Since forging 04 is not the limiting material, the reactor vessel integrity evaluations are not affected."
VIRGINIA POWER COMMENTS ON IDENTIFIED DISCREPANCIES Virginia Power has evaluated the staff's comments on the Reference (4) submittal, as documented in RVID and in Reference (i). The results of our evaluation are presented below.
Discrepancy #1: In Reference (1), the staff indicates that two of the four data points for North Anna Unit 1 lower shell forging 03 are not credible, but that all four data points are within the 2-sigma limits using Regulatory Guide 1.99 Revision 2 Position 1.1. The staff provides two acceptable methods for assessing the condition of the North Anna Unit 1 lower shell forging 03. The first method is to use the surveillance data for forging 03 to calculate the CF, but to apply a full margin term of 34 F to compensate for data sedter in excess of 1-sigma about a best-fit line. (The staff calculated a CF value of 73.51 F.) Using j
this method, the staff determined that the lower shell forging 03 is not the limiting material I
in terms of calculated RTers, and concluded that the reactor vessel integrity evaluations are not affected by the identified discrepancy. The second method proposed by the staff is l
to use the Regulatory Guide 1.99 Revision 2 Position 1.1 CF tables to determine the CF j
on the basis of the best-estimate copper and nickel concentration of the material in question.
1 Virginia Power calculations performed subsequent to the Reference (4) submittal corroborate the staff's conclusions regarding lower shell forging 03. CF calculations j
performed using combined tangentially and axially oriented Charpy specimen data resulted in a calculated CF of 73.5 F, with two of the four surveillance data points being non-credible. All four data points were within the two-sigma limits using RG 1.99 Revision 2 Position 1.1. When the CF of 73.5 F based on surveillance data and a margin term of i
34 F are applied, an RTpTs value of 171.5 F is calculated. Virginia Power concludes that the lower shell forging 03 is not the limiting material in terms of calculated RT s, and that PT Page 2 of 7
the reactor vessel integrity evaluations remain conservative. Virginia Power recommends no modifications to the data presented in RVID to address the identified discrepancy.
Discrepancy #2:In the RVID PTS Summary Report for North Anna Unit 1 (third footnote),
the staff performed an evaluation of the nozzle-to-intermediate shell weld 05A. The staffs evaluation indicates that, because Virginia Power utilizes a generic unirradiated RTuoT value, a ci value of 20 F and a o.s value of 28 F (i.e., a margin term of 68.8 F) should be used in the reactor vessel integrity evaluation.
Virginia Power calculations performed subsequent to the Reference (4) submittal confirm that the margin term calculated by the staff is appropriate. Virginia Power calculations confirm that, with this margin term, weld 05A is not the limiting material in terms of calculated RT s, and that the reactor vessel integrity evaluations remain conservative.
PT (Note: the subject footnote in RVID indicates that "the staff found that the limiting material is the nozzle to intermediate shell weld 05A." However, the RTPTs values in the RVID table do not support this conclusion. In any case, Virginia Power calculations confirm that, with
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the corrected margin term of 68.8 F for the nozzle-to-intermediate shell weld 05A, the reactor vessel integrity evaluations remain conservative.) Virginia Power recommends no modification to the data presented in RVID to address the identified discrepancy.
th Discrepancy #3:In the RVID PTS Summary Report for North Anna Unit 1 (11 botnoteh the staff performed an evaluation of the CF and resulting RTPTs value for circumferential weld 04 (beat number 25531). The staffs evaluation of this material resulted in a CF of 95.2 F based on surveillance data and the ratio procedure, and resulted in an RTPTs value of 175.9 F. Virginia Power previously reported a CF value of 93.1 F based on surveillance data and the ratio procedure, resulting in an RTPTs value of 172.9 F. Virginia Power calculations performed subsequent to the Reference (4) submittal confirm the previously calculated CF value of 93.1 F. The inputs to this calculation are as follows:
Reactor Vessel Beltline Material Wt% Cu = 0.11 Wt% Ni = 0.13 Capsule V Surveillance Capsule Fluence (x10" n/cm ) = 0.249 2
Measured ARTuoT ( F) = 78 Surveillance Material Wt% Cu = 0.124 Surveillance Material Wt% Ni = 0.152 Capsule U 2
Surveillance Capsule Fluence (x10" n/cm ) = 0.828 Measured ARTuor ( F) = 75 Surveillance Material Wt% Cu = 0.124 Surveillance Material Wt% Ni = 0.152 No irradiation temperature corrections are applied for the credibility determination, since the surveillance materials were all irradiated in the same reactor.
No irradiation temperature corrections are applied for the reactor vessel beltline material evaluation, Page 3 of 7
7 since the surveillance materials were irradiated in the reactor vessel that is being.
evaluated. No chemistry corrections are applied for the credibility determination since surveillance data were obtained from a single source. No chemistry corrections are applied for the reactor vessel beltline material evaluation since the best estimate chemical composition of surveillance materials is not significantly different from the beltline material being evaluated.
(If' chemical composition differences between the surveillance and beltline materials were credited in the reactor vessel beltline material evaluation, the CF would be further reduced below 93.1 F.) Virginia Power calculations confirm that performance of a RG 1.99 Revision 2 Position 2.1 CF calculation (as clarified by the Reference (5) meeting notes) with these analytical inputs results in a CF of 93.1 F.
Virginia Power recommends that the CF for North Anna Unit 1 intermediate to lower shell circumferential weld 04 presented in RVID be changed from 95.23 F to 93.1*F.
However, please note that a forthcoming Fall 1999 update to RVID for both North
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Anna units will further modify the calculated CF value for this material. The update i
will include forthcoming North Anna Unit 1 surveillance capsule W data, and revised reactor vessel fluence values based on the recently approved Virginia Power fluence analysis methodology topical report (6).
Discrepancy #4: In Reference (1), the staff confirms that Virginia Power reported a CF value of 47.9 F for North Anna Unit 2 intermediate shell forging 04. The staff used this CF in their calculations as an " override", since staff considered the value to be conservative.
An RTpTs alue of 175.1 F was calculated for this material assuming a margin term of v
34 F. Reference (1) suggests that a CF of 35.1 F and an RTpTs alue as low as 157.5 F v
are justified. However, a margin term of 34 F is required, since one of the four surveillance data points for forging 04 is not credible, but all four data points are within the 2-sigma limits using Regulatory Guide 1.99 Revision 2 Position 1.1.
Virginia Power calculations performed subsequent to the Reference (4) submittal confirm that the staffs assessment is accurate, in Reference (1), the staff provides two acceptable methods for assessing the condition of the North Anna Unit 2 intermediate shell forging 04.
The first method is to use the surveillance data for forging 04 to calculate the CF, but to apply a full margin term of 34 F to compensate for data scatter in excess of 1-sigma about a best-fit line. Using this method, the staff determined that the intermediate shell forging 04 is not the limiting material in terms of calculated RTpTs, and concluded that the reactor vessel integrity evaluations are not affected by the identified discrepancy. The second method proposed by the staff is to use the Regulatory Guide 1.99 Revision 2 Position 1.1 CF tables to determine the CF on the basis of the best-estimate copper and nickel concentration of the materialin question.
Virginia Power calculations performed subsequent to the Reference (4) submittal using this second alternative method corroborate the staffs conclusions regarding intermediate shell forging 04. Specifically, Virginia. Power has determined that the intermediate shell forging 04 is not the limiting material in terms of calculated RTpTs, and has concluded that the reactor vessel integrity evaluations remain conservative. Virginia Power recommends no modification to the data presented in RVID to address the identified discrepancy.
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~ ADDITIONAL DISCREPANCIES Several, additional discrepancies between the information presented in RVID and Virginia Power analyses performed for North Anna Units 1 and 2 subsequent to the Reference (4) submittal have' been' identified.~ -These discrepancies and: proposed resolutions are presented below.
Discrepancy #5 (From the RVID PTS Summary Report for North Anna Unit 1): The North Anna Unit 1 RVID PTS Summary Report presents a margin term of 34 F for nozzle belt forging 05 (heat ID 990286/295213). This margin term implies a ci value of 0 F, and a a3 value of 17 F for forging 05.' Virginia Power analyses of this material performed
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subsequerit to the Reference (4) submittal have utilized a ai value of 30 F based on a
. generic assessment of SA-508 Class 2 materials (7). When combined with a a3 value of 17 F, a margin term of 69.0 F is calculated for nozzle belt forging 05. Virginia Power has determined that nozzle belt forging 05 is not the limiting material in terms of calculated RTers, and has concluded that the reactor vessel integrity evaluations remain conservative. Virginia Power recommends modification of the margin term in RVID to reflect a ei value of 30 F for nozzle belt forging 05 (heat ID 990286/295213).
Discrepancy #6 (From the RVID PTS Summary Report for North Anna Unit 2): The North Anna Unit 2 RVID PTS Summary Report presents a margin term of 34 F for nozzle
~
belt forging 05 (heat ID 990598/291396). This margin term implies a ci value of 0 F, and a c3 value.of 17 F for forging 05. Virginia Power analyses of this material performed
. subsequent to the Reference (4) submittal have utilized a ei value of 30 F based on a generic assessment of SA-508 Class 2 materials (7). When combined with a o3 value of 12.7'F (i.e., half of the predicted shift in RTwoT), a margin term of 65.2 F is calculated for nozzle belt forging 05. Virginia Power has determined that nozzle belt forging 05 is not the limiting material in terms of calculated RTPTs, and has concluded that the reactor vessel integrity evaluations remain conservative. Virginia Power recommends modification of
. the margin term in RVID to reflect a ai value of 30 F for nozzle belt forging 05 (heat ID 990598/291396).
Discrepancy #7 (From the RVID PTS Summary Report for North Anna Unit 2): The North Anna Unit 2 RVID PTS Summary Report presents copper and nickel concentrations of 0.09 wt% Cu and 0.83 wt% Ni for intermediate shell forging 04 (heat ID 990496/292424).
The best estimate chemical composition of North Anna Unit 2 intermediate shell forging 04 was updated by Reference (4). (See pages 2-5,2-11, and A-6 of BAW-2260, which was transmitted by Reference (4).) The revised copper and nickel concentrations are 0.10 wt% Cu and 0.85 wt% Ni. Virginia Power has determined that intermediate shell forging 04 is not the limiting material in terms of calculated RTpTs, and has concluded that the reactor vessel integrity evaluations remain conservative. Virginia Power recommends modification of the copper and nickel concentrations for intermediate shell forging 04 (heat ID 990496/292424) in RVID to be 0.10 wt% Cu and 0.85 wt% Ni.
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1 CONCLUSIONS-Virginia Power has evaluated the NRC Generic Letter 92-01 Revision 1 Supplement.1
" closure letter" (1) and the Reactor Vessel Integrity Database (RVID) PTS Summary L
Report. footnotes for North Anna Units 1 and 2. Virginia Power concurs with the staff's j
conclusion that the discrepancies identified in the Reference (1) letter and in the RVID f
footnotes do not affect the conclusion that the reactor vessel integrity analyses remain
. valid and conservative. However, as a result of our evaluation of the discrepancies
. identified aboveiwe make the following recommendations:
l Virginia Power recommends that the CF for North Anna Unit 1 intermediate to lower l
shell circumferential weld 04 presented in RVID be changed from 95.23 F to 93.1 F.
' Virginia Power recommends modification of the margin term in RVID to reflect a ei value ~of 30 F for the North Anna Unit 1 nozzle belt forging 05' (heat ID i
990286/295213).
Virginia Power recommends modification of the margin term in RVID to reflect a ci value of 30 F for the North Anna Unit 2 nozzle belt forging 05 (heat ID l.
990598/291396).
Virginia Power recommends modification of the copper and nickel concentrations for l
North Anna Unit 2 intermediate shell forging 04 (heat ID 990496/292424) in RVID to be i
0.10 wt% Cu and 0.85 wt% Ni.
In Fall 1999, Virginia Power will be transmitting a surveillance capsule analysis report for North Anna Unit 1 Capsule W. Following our receipt of the analysis report from the 1
analysis vendor, Virginia Power will prepare and transmit an evaluation of the newly acquired data in the form of updated RVID data tables. In addition, these data tables will include revised reactor vessel fluence values based on the recently approved Virginia Power fluence analysis methodology topical report (6). Similarly, North Anna Unit 2 Capsule W is scheduled to be withdrawn in Fall 1999. An analysis report and an i
evaluation of available surveillance data will also be provided for North Anna Unit 2 in Fall 2000.
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m j
REFERENCES-
- (1);
L Letter from N; Kalyanam (USNRC) to J. P. O'Hanlon (Virginia Power), " Closure of the Review of the Response to Generic Letter 92-01 Revision 1, Supplement 1,
Reactor Vessel Structural Integrity,' The North Anna Nuclear Power Plant, Units L1 and 2 (TAC Nos. MA0555 and MA0556)," Serial No.99-361, dated June 23, 1999.
(2).
Letter from USNRC to all Nuclear Power Plant Licensees, "NRC Generic Letter 92-01, Revision 1, Supplement 1: Reactor Vessel Structural Integrity," Serial No.95-270, dated May 19,1995.
'(3)
Letter from J. P. O'Hanlon (Virginia Power) to OSNRC, " Virginia Electric and Power Company, North Anna Power Station' Units 1 and 2, Surry Power Station Units 1 and 2,90-Day Response to Generic Letter 92-01 Rev.1 Supp.1, Reactor Vessel Structural integrity," Serial No.95-270, dated August 10,1995.
(4)-
' Letter from J.'P. O'Hanlon (Virginia Power) to USNRC, " Virginia Electric and Power Company,'Surry Power Station Units 1 and 2, North Anna Power Stat;on Units 1 and 2, Six Month Response to Generic Letter 92-01 Rev.1 Suppl.1, Reactor Vessel Structural Integrity," Serial No. 95-270A, dated November 20, 1995.
(5)
Memorandum from K. R. Wichman to E. J. Sullivan, " Meting 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.
(6)
Virginia Power Topical Report VEP-NAF-3, " Reactor Vessel Fluence Analysis Methodology," dated November,1997.
(7)
- BAW-10046, " Methods of Compliance with Fracture Toughness and Operational Requirements of 10 CFR 50 Appendix G," dated March 1976. (See also BAW-1911 Revision'1, " Reactor Pressure Vessel and Surveillance Program Materials Licensing Information for North Anna Units 1 and 2," dated August 1986.)
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