ML061220595
| ML061220595 | |
| Person / Time | |
|---|---|
| Site: | Nine Mile Point  |
| Issue date: | 04/21/2006 |
| From: | O'Connor T J Constellation Energy Group |
| To: | Document Control Desk, Office of Nuclear Reactor Regulation |
| References | |
| TAC MC3272, TAC MC3273 | |
| Download: ML061220595 (12) | |
Text
., Constellation Energy Nine Mile Point Nuclear Station P.O. Box 63 Lycoming, NY 13093 April 21, 2006 U. S. Nuclear Regulatory Commission Washington, DC 20555-0001 ATTENTION:
Document Control Desk
SUBJECT:
Nine Mile Point Nuclear Station Unit Nos. 1 & 2; Docket Nos. 50-220 & 50-410 Amended License Renewal Application
-NRC Request for Additional Information (RAI) 4.7.5A-1 (TAC Nos. MC3272 and MC3273)By letter dated July 14, 2005, Nine Mile Point Nuclear Station, LLC (NMPNS) submitted an Amended License Renewal Application (ALRA) for the operating licenses of Nine Mile Point Units 1 and 2.In a letter dated April 19, 2006, the NRC requested additional information regarding new ALRA Section 4.7.5 that was sent to the NRC in the NMPNS Annual Update Letter, NMP1L 2009, on December 20, 2005. The NMPNS response to RAI 4.7.5A-1 on the NMP1 RWCU System weld overlay repairs is provided in Attachment
- 1. This letter contains no new regulatory commitments.
Should you have questions regarding the information in this submittal, please contact P. A.Mazzaferro, NMPNS License Renewal Project Manager, at (315) 349-1019.Very Nine Mile Point)Ic1X1 Document Control Desk April 21, 2006 Page 2 STATE OF NEW YORK: TO WIT: COUNTY OF OSWEGO I, Timothy J. O'Connor, begin duly sworn, state that I am Vice President Nine Mile Point, and that I am duly authorized to execute and file this submittal on behalf of Nine Mile Point Nuclear Station, LLC. To the best of my knowledge and belief, the statements contained in this document are e and correct. T'o the extent that these statements are not based on my personal knowledge, they are b sed upon information provided by other Nine Mile Point employees and/or consultants./uch informati has been reviewed in accordance with company practice and I believe it to be reliabl Subscribed and sw~-p before me a Notary Public in and for the State of New York and County of Oswego, this ' day of ,4 , 2006.WITNESS my Hand and Notarial Seal: _____ __ __ _Q u a Notary Public My Commission Expires:/ /Date SANDRA A. OSWALD Notary Public, State of New York No. 010S6032276 Qualified in Oswego County Commission Expires t6= 9-TJO/MRF/sac Attachments:
(1) Response to NRC RAI 4.7.5A-1 on the NMP1 RWCU System Weld Overlay Repairs cc: S. J. Collins, NRC T. G. Colburn, NRC N. B. Lee, NRC Resident Inspector, NRC J. P. Spath, NYSERDA Document Control Desk April 21, 2006 Page 3 bcc: L. S. Larragoite C. W. Fleming, Esquire T. J. O'Connor J. A. Hutton'M. H. Miller/T.
F. Syrell M. A. Schimmel.J. L. Lyon'P. A. Mazzaferro
'D. J. Dellario M\4. R. Fallin NMP1L 2041 COMMITMENTS IDENTIFIED IN THiS CORRESPONDENCE:
- None Posting Requirements for Responses
-NOV/Order No ATTACHMENT (1)RESPONSE TO NRC RAI 4.7.5A-1 ON THE NMP1 RWCU SYSTEM WELD OVERLAY REPAIRS Nine Mile Point Nuclear Station, LLC April 21, 2006 ATTACHMENT (1)RESPONSE TO NRC RAI 4.7.5A-1 ON THlE NMP1 RWCU SYSTEM WELD OVERLAY REPAIRS This attachment provides the Nine Mile Point Nuclear Station, LLC (NMPNS) response to the RAI contained in the NRC letter dated April 19, 2006. The NRC RAI is repeated, followed by the NMPNS response.RA 14.7. 5A-1 On January 23, 2006, the staff held a conference call (ADAMSAccession No.ML060890579) with Constellation Energy Group (CEG, the applicant) to discuss the basis for approving Time-Limited Aging Analysis (TLAA) 4.7.5, "Reactor [Water Cleanup Weld Overlay Fatigue Flaw Growth Evaluations (NMP1 Only). " Consistent with the discussion, the staff has stated that the most appropriate basis for approving TLAA 4.7.5 would be to credit an acceptable inspection-based aging management program (AMP)for the management of intergranular stress corrosion cracking (IGSCC) in the reactor waler cleanup (RWCU) system welds 33-FW-22 and 33-FW-23A and their repair overlays.
This is permissible under the acceptance criterion of 10 CFR 54.21(c)(1)(iii).
The applicant stated that it will consider revising the information to its letter dated December 20, 2005, and will amend the letter, per information provided by the staff during the January 23, 2006, phone call, to credit inspections as an AMPfor accepting TLAA 4.7.5 under 10 CFR 54.21(c)(1)(iii):
This RAI requests that CEG address the following staff concerns in its upcoming amended letter, if ultrasonic test (UT) examination work is credited as an AMP for accepting TLAA 4.7.5 under 10 CFR 54.21(c)(1)(iii):
A. Ciarify that, pursuant to 10 CFR 54.21(c)(1)(iii), CEG is creditingAMPB2.1.6,"BWR Stress Corrosion Cracking Program" and the augmented ultrasonic (UT)examination program, as specified in Topical Report BWRVIP-75-A, "Technical Basis for Revisions to Generic Letter 88-01 Inspection Schedules
[April 2002j, "for Category E austenitic stainless steel welds as the basis for managing IGSCC in RWCUwelds 33-FW-22 and 33-FW-23A and their corresponding overlay repairs.Note that those austenitic steel pipe welds have been repaired with austenitic steel weld overlays.B. Revise the NMP1 specific version ofAMP B2.1.6, "BWR Stress Corrosion Cracking Program " to include the following enhancements to program attributes:'
(1) [Scope ofProgram]:
Enhancement to include the overlay repairs on RWCU welds 33-FW-22 and 33-FW-23A within the scope of the AMP.(2) [Detection ofAging Effects]:
Enhancement to specify that site-qualified ultrasonic testing (UT) techniques will be used to monitor R WCU welds 33-FW-22 and 33-FW-23A for further evidence of cracking andforflaw growth into weld metal deposits for the overlays.
The staff recommends that the enhancement of the program attribute be consistent with CEG's commitments made in response to GL 88-01, "NRC Position on IGCSS in BWR Austenitic Piping [January 15,'CEG has identified that AMP B2. 1.6, "BWR Stress Corrosion Cracking Program, " is an AMP that is consistent with the program attributes in AMP XI.M7, BJVR Stress Corrosion Cracking" with an exception.
1 of 8 1988], " and commitments made to implement the recommended guidelines of Topical Report BWRVIP-75-A.
(3) [Monitoring and Trending]:
Enhancement to establish a conservative applicant-based re-inspection frequency for performing the UT examinations of the overlays ofRJVCU Welds 33-F W'-22 and 33-FW-23A.
The staffrecommends that enhancement of the program attribute be consistent with CEG's commitments that were made in response to GL 88-01 and commitments made to implement the recommended guidelines of Topical Report B JR VIP-75-A.(4) [Operating Experience]:
Enhancement of the program attribute to specify that CEG performed the most recent UTexaminations of the RWCU welds 33-F V-22 and 33-FW-23A in 2003 and to summarize the results of the 2003 UT inspections.
Response On December 20, 2005, NMPNS submitted, in its LRA Annual Update letter (NMP1 L 2009), a new TLAA on the fatigue of weld overlay repairs that were made at two inter-granular stress corrosion cracking (IGSCC) induced flaw locations on the non-safety-related (NSR), regenerative heat exchanger (RHX) in the Reactor Water Cleanup (RWICU) System. New ALRA Section 4.7.5 provided the information for this new TLAA.The IGSCC induced flaws manifested themselves as leaks in the RHX inlet nozzle and in the transition pipe between the two RHX shells. Although the welds do not fall under the jurisdiction of ASME Section XI, the weld overlay designs used Code Cases N-504 (Weld 33-FW-22) and N-504-2 (Weld 33-FW-23A) as guidance.
Further, the weld overlay repair used an IGSCC resistant material since the weld material in which the flaws occurred is not IGSCC resistant.
The weld flaws were not excavated prior to the application of the circumferential weld overlays.The TLAA addressed cracking due to fatigue of these repairs over the balance of the life of the plant including the period of extended operation (PEO). Analyses were performed to show that the number of postulated startup/shutdown cycles (using >50% safety margin) would not result in fatigue concerns for these repairs. The assumption was made that in the transition zone of each weld between the original material and the IGSCC resistant weld material, there was a 1/16" circumferential IGSCC induced crack due to weld dilution.
The analyses showed that the assumed crack would not propagate in a maimer that would violate ASME Code requirements.
Because the analyses showed that cracking due to fatigue would not be an issue, the TLAA was dispositioned for license renewal as being consistent with 10 CFR 54.21(c)(1)(i);
i.e., the analyses remained valid for -the PEO.Subsequent to the performance of the evaluation of this TLAA for LR and its inclusion in NMIP1L 2009, it was determined that because the flaws in the original welds occurred due to IGSCC, NMPNS had already addressed them under the requirements of Generic Lett er 88-01. They had been identified as Category E welds and were, therefore, subject to an augmented inspection under the BWR SCC Program that performs ultrasonic testing (UT) in accordance with the guidelines in BWRVIP-75-A for normal water chemistry.
This provides for a 25% sample inspection every ten years with 50% of those 2 of 8 examinations to be completed within the first 6 years of the interval.
The last inspection for 33-FW-22 was performed in 2003. No cracks were found during that inspection.
The first re-inspection for 33-FW-23A is to be performed during the 2007 refueling outage.Since the repairs are periodically being checked for cracking, this includes any cracking of the repairs that may occur due to fatigue. The disposition of the TLAA will, therefore, be changed to be consistent with 10 CFR 54.21(c)(1)(iii).
The aging effect of cracking (du- to fatigue in this case) will be adequately managed by the BWR SCC Program for the PEO.ALRA Revisions Sinze the potential for cracking due to fatigue of these weld overlay repairs is now to be managed for aging by the BWR SCC Program, changes to the ALRA are required.ALRA Table 3.3.2.A-17 and the Section 3.3 Plant Specific Notes from the ALRA;Section 4.7.5 and Appendix Al .2.5.2 that were transmitted via NMP1L 2009; and Appendices B2.1.6 and B2.1.15 from the ALRA all require revision as shown below.Revisions to existing ALRA text are shown with italics for text additions and stfikethfoughs for text deletions.
Revision bars in the right margin indicate where ALRA texi revisions are indicated.
Table 3.3.2.A-17 The changes to Table 3.3.2.A-17 (ALRA p. 3.3-174) are shown on the next page (p. 4) of this attachment.
Section 3.3 Plant Specific Notes Plant Specific Note 32 is added to ALRA p. 3.3-310 as follows: 32. See ALRA Section 4.7.5, Reactor Water Cleanup System Weld Overlay Fatigue Flaw Growth Evaluations (NMPI Only), and the Program Description in Appendix B2.1.6, B WR Stress Corrosion Cracking Program.3 of 8 Table 3.3.2.A-17 Auxiliary Systems NMP ReD1 1 1 .lt. r'I..... CS.t,-_..
-,nnrf At A -,nn4omannt V1vqinftinn Intended Agn fet Aging Management NUE-81 Table 1 Component Type Function Material Environment Requiring Program Volume 2 Item Notes__________Management Item Heat Exchangers PB Copper Alloys Lubricating None None None (cont'd) LBS (Zinc < 15%) Oil (cont'd) (cont'd) _Wrought Austenitic Demineralized Loss of Material Closed Cycle H Stainless Steel Untreated Cooling Water Water System Progam Treated Water Cracking One-Time Inspection VII.E3.4-a 3.3.1.A-04 B or Steam, ProMram temperature
>140 0 F, but Water Chemistry<212 0 F Control Program LBS WroughtAustenitic Treated Water Cracking TLAA. evaluated in H. 32 Stainless Steel or Steam, accordance with 10 temperature CFR 54.21(c)>212TF. but<482 0 F Piping and PB Carbon or Low Treated Water Cumulative Fatigue TLAA, evaluated in IV.Cl.1-h 3.1.1.A-01 A Fittings Alloy Steel or Steam, Damage accordance with 10 (Yield Strength temperature CFR 54.21(c)< 100 Ksi) >212°F, but<482°F Loss of Material Flow-Accelerated IV.C1.l-c 3.1.1.A-25 C Corrosion Program One-Time Inspection H Program Water Chemistry Control Program 4 of 8 Section 4.7.5 The revision to Section 4.7.5 (starting on ALRA p. 4.7-8), as presented in NMP1 L 2009, is as follows: 4.7.5 REACTOR WATER CLEANUP SYSTEM WELD OVERLAY FATIGUE FLAW GROWTH EVALUATIONS (NMP1 ONLY)Fatigue crack growth analyses have been performed for two weld overlays in the reactor water cleanup system. Both welds are non-ASME Section Xl welds.Although the welds do not fall under the jurisdiction ofASME Section XI- tThe weld overlay designs is in accordance withused Code Cases N-504 (Weld 33-FW-22) and N-504-2 (Weld 33-FW-23A) as guidance.
The repaired welds are located at the inlet nozzle of the regenerative heat exchanger and the transition pipe between the upper and lower shells of the regenerative heat exchanger, respectively.
The leak of the first weld was characterized as a pinhole while the second leak was due to a vertical crack. Nondestructive examination of the leaking welds revealed that the leak in 33-FW-22 was due to a through-wall axial crack, while the leak in 33-FW-23A was due to an 8.5 inch circumferential flaw.Both repairs are full structural weld overlays that completely replace the structural capacity of the original weld. The originalflaws were not excavated prior to application of the weld overlay. The weld overlays consist of IGSCC-resistant austenitic stainless steel material and, thus, are not susceptible to continued IGSCC crack propagation.
However, the first 1/16" thick layer of weld metal deposited is not assumed to be IGSCC-resistant due to weld dilution; thus, it is assumed to be cracked. A fatigue crack growth analysis was performed in accordance with ASME Section XI, Appendix C, with the crack propagating into the overlay from the hypothetical 1/16" deep crack. The acceptance criteria for fatigue crack growth analyses are based on the depth to thickness ratios from Tables IWB-3641-5 and IWB-3641-6.
Disposition:
§54.21(c)(1)(iii)
-The effects of aging on the intendedfitnction(s) will be adequately managedfor the period of extended operation.analy~se remain valid for- the period of extended epefatien Both welds are subject to augmented inspection uinder the BWR SCCprogram.
The welds are classified as IGSCC category E as a result of having been repaired by weld overlay. The required scope of examination, in accordance with the guidelines ofB UR VIP-75-A for normal water chemistry, is a 25% sample every ten years, with 50% of these examinations to be completed within the first 6 years of the interval.
Since there are only two welds in this category, the result is that 50% of these welds or one weld is inspected during each ten-year interval.The analysis for weld 33-FW-22, performed in 1997, assumed 154 startup/shutdown cycles. The flaw depth to weld overlay thickness ratio remained acceptable at 0.22 versus an allowable of 0.29. The number of cycles assumed was based on an estimate of 7 cycles/year for 22 years (12 remaining years of the 5 of 8 original license period plus 10 additional years). The last ultrasonic examination of t/e weld overlay was performed in March, 2003, finding no indications.
Therefore, the weld could be assumed to be acceptable for 154 additional startup/shutdown cycles from the date of the latest inspection.Therc havc been 34 startup/shutdown cycles sinee the beginning of 1997; this everlay was installed in May-,1997.
Therefore, the weld overlay could experienec 120 more cycles before cxceeding the assumptions of the analysis.
During the last ten years of operation, NMP1 has been experiencing startups and shutdown cycles at a rate of approximately 4/year. Therefore, during the time period between 2003 and the end of the period of extended operation, the RWCU system will experience an estimated 104 startup/shutdown cycles. Additionally, since one of the two weld overlays will be inspected during each ten year interval, weld 33-FW-22 will be inspected at least once more before the end of the period of extended operation.Therefcr, it is expected that the actual number of startups/shutdowns will remain below 120 eycles in the next 24 years (4 years riginal license plus 20 year period xf extended operatinn).
The.efore, the atigue crack growth analysis fer- the weld 33 FW 22eveo clay is expected to r-emain valid for- the per-iod of extended oper-ation.
The analysis for weld 33-FW-23A was performed in 2005 and assumed 168 startup/shutdown cycles based on 7 cycles/year for 24 years (the 4 remaining years of the original license plus the 20 year period of extended operation).
The final flaw depth to thickness ratio was 0.17 compared to an allowable of 0.42;thus, the weld was acceptable for the cycles analyzed.
Weld 33-FW-23A is scheduledfor its first UTre-examination during the 2007 refueling outage and will be inspected at least once more before the end of the period of extended operation.
Therefore, since the weld overlays undergo UT examinations periodically, per the requirements of B WR VIP- 75-A, to ensure nofatigueflaw growth has occurred, aging of the R WCU weld overlays will be adequately managed in accordance with §54.21(c)(1)(iii).
Therefore, sinee this fnalysis was perfcnned considering the pericd of extended operation, the analysis remains valid for the per-iod ot extended operation.
Ap)endix A1.2.5.2 The revision to Appendix A1.2.5.2 (ALRA p. Al-34), as presented in NMP1L 2009, is as follows: A1.2.5.2 REACTOR WATER CLEANUP SYSTEM WELD OVERLAY FATIGUE FLAW GROWTH EVALUATIONS Fatigue crack growth analyses have been performed for two weld overlays in the reactor water cleanup system. The repaired welds are located at the inlet nozzle of the regenerative heat exchanger and the transition pipe between the upper and lower shells of the regenerative heat exchanger, respectively.
The I 6 of 8 weld overlays consist of IGSCC-resistant austenitic stainless steel material and, thus, are not susceptible to continued IGSCC crack propagation.
However, the first 1/16" thick layer of weld metal deposited is not assumed to be IGSCC-resistant due to weld dilution; thus, it is assumed to be cracked. A fatigue crack growth analysisfor each weld overlay was performed in accordance with ASME Section XI, Appendix C, with the crack propagating into the overlay from the hypothetical 1/16" deep crack. The results of those analyses showed that the welds were acceptable per the code criteria through the end of the period of extended operation.
Additionally, however, the overlaid welds are UT examined periodically under the B WR Stress Corrosion Cracking Program, thus ensuring there is no fatigue crack propagation into the overlays.
The maximum interval between inspections is defined by the requirements of B WIR VIP-75-A.
Therefore, the aging of the R WVCU weld overlays will be adequately managed through The fatigue crack growth anlyscs for the weld overlays arc expected to remain valid for the balance of the initial 40 year licensing term and the period of extended operation.
Appendix B2.1.6 At ihe end of the Program Description for Appendix B2.1.6 (ALRA p. B2-14) in the ALRA, add the following new paragraph:
Additionally, UTexaminations are being performed as augmented inspections under this program forR WCUSystem weld overlay repairs to NSR, non-code, welds 33-F W-22 and 33-,FW-23A.
This testing has been and will continue being performed to meet GL 88-01 andBWRVIP-75-A requirements, as applicable to each weld repair, per the guidance of this program, to manage cracking due to fatigue of those repairs. See Section 4.7.5 of this application for details relative to the fulfillment of the program elements from this program.Under the "NUREG-1 801 Consistency" and "Exceptions to NUREG-1 801" headings, since the application of this program for these augmented inspections is outside the scope described in NUREG-1 801, Revision 1, there are no NUREG-1 801 consistency concerns.Program "enhancements" are those revisions of an NMP AMP that are required to be consistent with NUREG-1801 Section XI guidelines.
There are no NUREG-1801 driven enhancements required to provide for the performance of the credited UT inspections; therefore, further discussion addressing "enhancements" to the BWR SCC Program is not warranted.
Relative to the Scope of Program, Detection of Aging Effects, Monitoring and Trending, and Acceptance Criteria program elements of the BWR SCC Program, as applicable to the RWCU weld overlays, since the paragraph added above under the "Program Description" refers the reader to ALRA Section 4.7.5, where the specifics of the fulfillment of these program elements are addressed, no further discussion is needed under these program elements in ALRA Appendix B2.1.6.7 of 8 At the end of the "Operating Experience" program element (ALRA p. B2-15), the following paragraph is added: Adaditionally, review ofplant-speciJ c operating experiencefor NMPJ identified that leaks were experienced in two welds outboard of the second isolation valve in the Reactor JMater Cleanup System. Weld 33-FW-22 had undergone a localized repair during its original construction and consequently, became more sensitized.
JMeld 33-FW-23A is a one of a kind design configuration that is subject to very high stresses due to the fact that it connects two very large heat exchanger shells that are subject to different thermal movement that cannot be accommodated by the short and stiffpipe.
In addition, the pipe is subject to thermal cycling. Both welds were repaired by full structural weld overlays that are being ultrasonically tested as augmented inspections under this program. See ALRA Section 4.7.5 for details.AM)endix B2.1.15 The "Operating Experience" program element (ALRA p. B2-39) discussion is revised as follows: NMPNS has reviewed both industry and plant-specific operating experience relating to cracking in the Reactor Water Cleanup System. This review found that there have been nojailures that are applicable to the scope or conduct of this program. As industry and plant operating experience is obtained relative to this program, lessons learned will be used to adjust the program as applicable.
Rcview of plant spceific operating expericxcc
&fei[:MPI identified that leaks were expefieneed in two welds eutbo othe r e CA ND is4ation ;alve. eAld 3 3 FW 22 had undergone a lealized repair dufing its Original eentrmction and consequently, became more sensitized.
Weld 33 FW 23A is a one of a kind design configuration that promotes very high stresses due to the fact that it connects veiy large shells that have different thermal movement that connnot be accommedated by the-sheot-and stiff-pipe.
In addition the pipe is subject to thermal cycling. Both welds w-eaked by raefullssfue al weld everla.8 of 8