ML20236V844
| ML20236V844 | |
| Person / Time | |
|---|---|
| Site: | Hope Creek  |
| Issue date: | 07/28/1998 |
| From: | Eric Simpson Public Service Enterprise Group |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| References | |
| LR-N980231, NUDOCS 9808040238 | |
| Download: ML20236V844 (12) | |
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Pude Servce Electre and Gas Cornpany E. C. simpson Pubhc Service Electnc and Gas Company PO Box 236. Hancocks Bndge. NJ 08038 609-339-1700 Seraor Vce P<ewdent Nudoar Engmeenr" ryj(g81998 LR-N980231 United States Nuclear Regulatory Commission Document Control Desk Washington, DC 20555 Gentlemen:
RELIEF REQUESTS ASSOCIATED WITH CORE SPRAY NOZZLE WELD REPAlR HOPE CREEK GENERATING STATION FACILITY OPERATING LICENSE NPF-57 DOCKET NO. 50-354 This letter forwards relief requests associated with changes made to the repair plan for the Core Spray Nozzle Weld NSB as well as the information requested by the NRC in an April 15,1998 teleconference.
In Letter LR-N970667, dated October 9,1997, and Letter LR-N970686, dated October 15,1997, PSE&G submitted plans related to the repair of Core Spray Nozzle Weld NSB that proposed an alternative to the ASViE Code requirements. The PSE&G repair plan provided justification for the proposed alternatives and was approved by the NRC in a letter dated October 17,1997 (TAC Number M99755). Subsequently, two changes to the repair plan were submitted; however, the changes were submitted as commitment changes rather than as relief requests. The first involved redefining the maximum interpass temperature during the holding period following post-weld heat treatment (PWHT) from ambient temperature +50 F to ambient temperature +100 F. The basis for this change was submitted to the NRC in LR-N970709-, dated November 12,1997. The second involved a change to the acceptance criteria for the post-repair examinations.
The basis for this second change was submitted in LR-N970762, dated November 21, 1997. Both changes were discussed with the NRC.
Information associated with each of the additional relief requests is provided in Attachment 1 to this letter. The information provides a description of each change and g the basis for relief. The discussion for the interpass temperature change also 1 incorporates the information requested in the April 15,1998 teleconference. Attachment '
l 2 includes a revision to the original repair plan that was submitted in support of the repair.
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9808040238 98072 [
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i M 281998 Document Control Desk '
LR-N980231 .
Should you have any queMions regarding this information, please contact C. Manges at (609) 339-3234.
Sincerely, Attachments (2)
{M C Mr. H. Miller, Administrator - Region l U. S. Nuclear Regulatory Commissbo 475 Allendale Road King of Prussia, PA 19406 Mr. R. Ennis, Licensing Project Manager - HC U. S. Nuclear Regulatory Commission One White Flint North 11555 Rockville f .ke Mail Stop 14E21 Rockville, MD 20852 Mr. S. Pindale (X24)
USNRC Resident inspector - HC Mr. K. Tosch, Manager IV Bureau of Nuclear Engineering P. O. Box 415 Trenton, NJ 08625 i
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l ATTACHMENT 1 HOPE CREEK GENERATING STATION FACILITY OPERATING LICENSE NPF-57 DOCKET NO. 50-354 ADDITIONAL RELIEF REQUESTS This attachment dercribes relief requests associated with the through-wall leak on Core Spray Nozzle NSB that was repaired during the seventh refueling outage at Hope Creek. The information that was requested in the April 15,1998 teleconference is included in the discussion of the interpass temperature change.
BACKGROUND At the time of the repair, the applicable ASME Code for Hope Creek was the 1983 (
Edition with Summer 1983 Addenda. As a result,Section XI, Article IWB-4000 of j that edition of the ASME Code provided the governing requirements for repair of the pressure-retaining boundary for Class 1 components and their supports at l Hope Creek. j l
In Letter LR-N970667, dated October 9,1997, and Letter LR-N970686, dated i October 15,1997, PSE&G submitted plans related to the repair of Core Spray Nozzle Weld NSB that proposed an alternative to the subject ASME Code requirements. The PSE&G repair plan provided the basis for the proposed alternatives and was approved by the NRC in a letter dated October 17,1997 (TAC Number M99755).
Subsequent to the approval of the original relief request, two changes to the repair plan were made. These changes are revisions to the original repair plan and are considered to be additional relief requests. Each of the subject changes is discussed below.
DESCRIPTION OF ADDITIONAL RELIEF REQUESTS Maximum Interpass Temperature The first change involved redefining the maximum interpass temperature during the holding period following post-weld heat treatment (PWHT) from ambient temperature +50 F to ambient temperature +100 F.
Acceptance Criteria for Post-Repair Examinations l
The second revision involved eliminating the need for the post-repair examinations to meet ASME Section lli acceptance criteria. The original repair Page 1 of 4
, Attachm:nt i LR-N980231 Additlanti Rrlitf R: quests plan specified that the weld overlay would be ultrasonically examined in accordance with Code Case N-504-1, " Alternative Rules for Repair of Class 1,2, l and 3 Austenitic Stainless Steel Piping Section XI, Division 1." Paragraph (1) of this Code Case specifies that pre-service examination of the overlay shall be performed in accordance with IWB-2200 and employ the acceptance standards of Table IWB-3415-2. Paragraph (h) of the Code Case further specifies that a post repair system hydrostatic test is to be performed, if the original flaws are through wall. The Hope Creek NSB Core Spray flaw (s) was a through wall condition at the time of discovery.
The Repair Plan also specified that Code Case N-416-1, " Alternative Pressure Test Requirement for Welded Repairs or Installation of Replacement items by Welding, Class 1,2 and 3 Section XI, Division 1", would be employed during the repair. This Code Case was chosen to provide an alternative to the hydrostatic test. Code Case N-416-1 provides for a post weld repair system leakage test at nominal operating pressure and temperature in lieu of the hydrostatic test, but is supplemented by required volumetric and surface examinations in accordance with ASME lil,1992 Ed; tion, no Addenda.
As a further clarification, the Repair Plan specified that the volumetric examination that would be performed would be ultrasonic (UT), in lieu of '
radiography. UT was selected because radiography wo' hl have been impractical and meaningful results would have been dao 9 cchieve due to the geometry of the repair area. The UT acceptance c. % was ASME Ill, Section NB-5330.
During the performance of the ulti, onic examination, a circumferentially oriented laminar type flaw was detected in the weld overlay, using 0 straight beam ultrasonic examination. This condition was documented in a non-conformance report (NCR). This reported !:minar flaw was identified by GE using the automated (Smart 2000 UT system), but could not be confirmed as being present, when using 0 degree manual scanning equipment. In addition, there is no discernible loss of UT back reflection signalin the location of the laminar indication, and the indication is not located where masking of the original flaws, prior to repair, would occur.
Since the overlay repair was made using a machine GTAW welding process, a !
worst case flaw assessment was postulated for conservatism, in developing the disposition to the NCR. It was assumed that the indication was due to a lack of fusion. The existence of an area of lack of fusion would not be in conformance with ASME Ill acceptance criteria.
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, Attachm:nt 1 LR-N980231 Additisnri R:li:f R:qunts l
BASIS FOR RELIEF {
Maximum Interpass Temperature ;
l PSE&G discussed the change regarding the maximum interpass temperature with the NRC on October 28,1997. During the teleconference, the NRC staff did not identify any concerns with the change, and the change to the repair plan was subsequently submitted in writing to the NRC in LR-N970709, dated November 12,1997 The following clarifies the basis for the change that was submitted in LR-N970709 and incorporates the information requested in the April 15,1998 teleconference.
Due to the potential outage impact and the emergent nature of the required repair, there was insufficient time to develop a unique welding procedure specification. Consequently, a pre-existing procedure t.',at had been developed for a dissimilar temperbead weld repair of an excavated cavity was submitted to the NRC for approval and used for the repair. The conditions for which the weld procedure was originally developed would inv'.!ve a dissimilar weld condition for the entire weld thickness, and the procedure therefore required that the temperbead welding preheat and postheat parameters be maintained during the deposit of the full section of the of the weld deposit.
The change submitted in LR-N970709 clarified that the temperbead preheat and postheat parameters would only be applied during the first three weld layers (minimum of 1/8 inch). The change, however, did not discuss weld interpass temperature controls beyond the first three temperbead weld layers. The temperbead welding technique was metallurgically essential during the initial weld layers deposited over the SA-508 Class 2 low alloy (P3) nozzle .naterial.
The preheat, interpass, and postheat controls were essential for grain refinement to preserve material toughness, to prevent untempered martinsite, and although unlikely, to assure that any potential hydrogen in solution would migrate away from the temperbead weld layers and heat affected zone. The first three layers were also important in the establishment of a non-diluted base that is comprised solely of F43 filler material, dfter which subsequent weld deposits would consist exclusively of F43 to F43 welding (i.e., no dissimilar welding). TM ,, st three layers were not credited structurally in the design analysis of the overlay.
PSE&G concludes that, for the Hope Creek repair conditions, there is no technical, metallurgical, or safety significance to the welding interpass temperature limitations specified in the Framatome welding procedure following completion of the temperbead deposited layers (i.e., third layer - 1/8 inch minimum thickness). As a result, the change to the repair plan submitted in LR-N970709 is justified.
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. Attachm:nt 1 LR-N980231 Additi nsi R:ll:f R:qu=ts Acceptance Criteria for Post-Repair Examinations The basis for the change to the acceptance criteria for post-repair examinations was originally submitted in LR-N970762, dated November 21,1997. The basis is repeated as follows:
As an alternative, the NCR demonstrated the acceptability of the flaw using the acceptance criteria of ASME XI,1989 Edition, no Addenda, IWB-3500, as originally specified in Code Case N-504-1. The NCR documents that a circumferentially oriented laminar flaw with maximum dimensions of 8.75 long by 0.32 wide is present. This results in a maximum flaw area of 2.8 in 2, which is 2
less than the allowable value of 7.5 in as defined in ASME Section XI Table IWB-3514-3. Therefore the flaw was considered acceptable as is.
The hydrostatic test as specified in Code Case N-504-1 was still deemed as unnecessary, based on the following:
. The weld overlay was examined in accordance with ASME Ill,1992 Edition, no Addenda. The UT examination showed that there were no additional indications in the immediate vicinity. The existence of a laminar flaw, if actually present in the overlay repair, will not interact in any detrimental manner with the original flaws. Therefore the repair of the original flaws met the intent of the original submitted Repair Plan.
. The reported laminar type flaw in the overlay (i.e., mid plane) is oriented such that there would be no verification of its structural integrity by the performance of a Class 1 hydrostatic test. Note: The hydrostatic test condition for tnis nozzle repair would only be required to have been in a range of between 1.02 Po and a maximum of 1.10 Po, depending on test temperature, where Po = the nominal operating pressure corresponding with 100% rated reactor power.
Based on the above, the non-conformance was considered as acceptable with its' "use as is" disposition. Further, this change in the use of ASME Section XI UT acceptance criteria was deemed as being consistent with the intent of the original Repair Plan.
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, Attachm:nt 2 LR-N980231 R:virad Riprir Pirn I
1 SCOPE- l The purpose of this document is to provide the repair plan for the PSE&G Hope Creek NSB core spray nozzle to safe end weld repair.
2 BACKGROUND During routine inservice inspection at the Hope Creek Nuclear Generating Station in Refueling Outage 7, a through-wallleak was identified in the vicinity of f the NSB core spray nozzle. Upon further investigation, it was discovered that the leak was a result of three pin holes in the safe end to nozzle weld. The root cause investigation has concluded the defects are due to intergranular stress corrosion cracking (IGSCC). Flaws, although not through wall, were identified at f similar locations in the past at several plants (Vermont Yankee, Pilgrim, and Brunswick) and were attributed to IGSCC. Of the various options that were considered to disposition the defects, Public Service Electric & Gas Company (PSE&G) elected to repair the defects using a weld overlay. A similar repair was performed on both core spray nozzles at Vermont Yankee in 1986, however, Alloy 82 filler was used for the repair overlay at Vermont Yankee, whereas Alloy 52 filler will be used at Hope Creek.
Subsequent ultrasonic examinations were performed which revealed a flaw extending circumferentially from top dead center approximately 4.1 inches,1.6 inches in one direction and 2.5 inches in the opposite direction, on the ID near the fusion line between the safe end replacement weld, ENiCrFe-3 Alloy 182, to original safe end weld, ERNiCr-3 (Alloy 82) root ENiCrFe-3 (Alloy 182) balance which was performed in 1982. Furthermor6 the flaw (s) is located greater than 1 inch outward from the core spray nozzle to buttering fusion line. The flew extends partially to fully through wall (see Attachment A). The replacement in 1982 involved replacing the original TP 304 safe end with a Ni-Cr-Fe SB-166 (Alloy 600) safe end.
The reactor vessel is constructed in accordance with ASME Code Section Ill, Nuclear Vessels,1968 Edition with Addenda to and including Summer 1970 Addenda and Paragraph NB-3338.2 (d)(4) of the Winter 1971 Addenda shall supersede Paragraph l-613 (d) of the 1968 Edition. The core spray nozzle is constructed of SA-508 Class 2 low alloy steel.
The reactor vessel ISI Program is in accordance with ASME XI,1983 Edition including Summer 1983 Addendum.
3 REPAIR DESCRIPTION The flaws in the weld will not be removed. After vessel drain down, the leak openings will be seal welded using the SMAW process using UNS W86152 Page 1 of 6 l
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, Attachmtnt 2 LR-N980231 Rsviasd Rapiir Plan (Code Case 2143) electrodes or manual GTAW using UNS N06052 Alloy 52 filler metal (Code Case 2142). A weld overlay, using UNS N06052 Alloy 52 wire (Code Case 2142), will be then be deposited, which will extend frorn the shoulder of the nozzle outward from the reactor vessel beyond the centerline of the
- E.NiCrFe-3 Alloy 182 replacement safe end attachment weld, on to the safe end l (see Attachments B and C). The overlay will extend around the full circumference of the nozzle h safe end weld for the required design length. The repair on the low alloy steel portion of the nozzle will be performed with the temperbead technique using Machine GTAW and Alloy 52 filler metal.
After the seal welding has been performed and PT examination accepted, the l area will be preheated to 300 F prior to Machine GTAW of the overlay.
Maximum interpass temperature will be 400 F, At least three (3) layers of weld l will be deposited (1/8 inch minimum thickness), which will extend 1/2 inch minimum outward beyond the flaw (s) toward the safe end (see Attachment C).
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This temperbead portion of the overlay will be subjected to postheat at 450 F to l {
550 F and held for 2 hours2.314815e-5 days <br />5.555556e-4 hours <br />3.306878e-6 weeks <br />7.61e-7 months <br /> minimum. After the nozzle is flooded, the balance of I the wcld overlay (i.e., non-temperbead portion) will be deposited with 60*F I minimum temperature and ambient plus 50100 F maximum interpass temperature, to 0.545 inches minimum final thickness, including the temperbead layers.
. The final weld will be PT and UT examined in accordance with ASME lil,1992 Edition, no Addenda (Code Case N-416-1) and Code Case N-432, including preservice UT examination in accordance with ASME XI,1992 Edition, including Addenda through 1993 (including Appendices Vil and Vill) and Code Case N-504-1, modified for examination of Ni-Cr-Fe overlays.
. Prict to initiation of the overlay, the design length will be marked using low stress dies. A second set of marks will be applied approximately 1/2 to 1 inch outside either end of the design overlay length. Punch marks shall be placed at 4 azimuthal locations. The axial distance between each set of marks will be
- measured and recorded. Following weld overlay application these i measurements will be repeated and dimensions recorded to determine the axial shrinkage which occurred during the overlay operation. The thickness after seal welding the flaw (s) and the final weld overlay thickness will be determined using ultrasonics.
t 4 REPAIR JUSTIFICATION l
The repair overlay has been designed in accordanco with NUREG-0313, Rev 2 and Code Case N-504-1 modified for use on the vessel nozzle and Ni-Cr-Fe safe end and attachment welds. The analytical bases for the design are in accordance with the ASME Code Section XI,1989 Edition, no Addenda, lWS- 1 3641 as specified in NUREG-0313 Revision 2. The design basis for the repair is ;
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, Attachm:nt 2 LR-N980231 R::v12:d Rrprir Pl:n a circu 71ferentially oriented flaw which extends 360 around the component and through wall l In addition, potential concerns about the toughness of the original safe end attachment weld material are not applicable since no credit is taken, in the design, for the load carrying capability of the remaining component wall ligament. The weld overlay thickness and length will restore the design margins inherent in IWB-3641, including consideration of the flaw. Furthermore, since it has been shown that the weld overlay arrests IGSCC crack growth, degradation of the repaired location design margins due to further crack growth into the weld overlay is not a concern. The repair is considered a permanent repair subject to the periodic inspection requirements specified in NUREG-0313 Revision 2.
5 APPLICABLE ASME BOILER AND PRESSURE VESSEL CODES AND CODE CASES FOR THE REPAIR The rules for Class 1 vessels shall apply in accordance with and as modified by the applicable documents listed in this section.
5.1 Section XI,1989 Edition, no Addenda shall be applicable for the repair.
5.2 Code Case N-389-1 shall be applicable.
5.3 Code Case N-432 shall be applicable, with modifications as described herein.
5.3.1 Paragraph 2.1(a)- The POR test plate was constructed of SA-533 Grade B Class 1 plate and not SA-508 Class 2 forging. The PQR weld filler was ERNiCr-3 Alloy 82 instead of Alloy 52. ASME XI,1992 Edition, no Addenda allows the use of the same P-Number Group Number and F-Number for Machine GTAW Temperbead Welding Procedure Qualification (POR), rather than the same material specification, grade and class.
5.3.2 Paragraph 2.1 (g)- welding consumables will be in accordance with NB-2000, ASME Ill,1989 Edition, no Addenda and Code Case 2142.
5.3.3 Paragrap;i 2.1(h)- Dropweight and impact tests of the weld deposit were not performed since the weid deposit is F-Number 43. NB-2000 does not require impact testing of th9 nickel alloy weld deposits.
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, Attachm:nt 2 LR-N980231 R:vi:cd R;prir PI:n 5.3.4 Paragraph 3.0(a)- Preheat will be maintained for the first three (3) layers
'or 1/8' inch temperbead deposit thickness, whichever is greater, rather than completion of welding. Three (3) layers of temperbead welding will provide the grain refinement and tempering to reduce the possibility of hydrogen embrittlement in the low alloy steel heat affected zone (HAZ).
The POR was performed with preheat until six (6) layers of weld was deposited.
5.3.5 Paragraph 3.0(d)(4)-The postheat will be performed after three (3) layers or 1/8 inch temperbead deposit thickness, whichever is greater, has been deposited rather than after completion of the final weld overlay. The postheat will provide for hydrogen migration from the temperbead layers.
The POR was performed with preheat until six (6) layers of weld was k deposited and then postheat was performed. The balance of welding, for this repair, over the low alloy steel nozzle area, will be performed in accordance with the PQR except without preheat or postheat.
5.3.6 The balance of welding over the balance of the safe end and safe end attachment welds will be performed using machine GTAW in accordance with P-Number 43 to P-Number 43 base materials welding procedure requirements in accordance with Section lil,1989 Edition, no Addenda.
5.3.7 The manual welders and welding procedures shall be qualified in accordance with ASME Ill,1989 Edition, no Addenda, where temperbead welding is not applicable. SMAW repairs in the temperbead portion of the weld, if required, may be performed in accordance with ASME XI,1989 Edition, no Addenda, using the half bead welding process for dissimilar welding. Other repairs,if required, may be performed using manual GTAW or SMAW using procedures qualified in accordance with ASME 111, 1989 Edition, no Addenda.
5.4 Section ill,1989 Edition, no Addenda shall he applicable for the welding materials, as modified by Code Cases 2142 and 2143.
5.5 Section Ill,1992 Edition, no Addenda, shall be applicable for NDE (Code Case N-416-1) for the repair overlay, except ultrasonic examination instead of radiographic examination will be performed. PT and UT examination shall be over the areas specified by Code Case N-432 as well as the full weld overlay over the Ni-Cr-Fe portions of the safe end and welds. ASME Xi,1992 Edition, including Addenda through 1993, including Appendices Vil and Vi!i, shall be applicable for the preservice UT examination.
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, Attachm:nt 2 LR-N980231 l Rivind rip:1r Pirn 1 5.6 Section XI,1992 Edition shall be applicable for the visual examination
'(\/T-2) (Code Case N-416-1) for the post repair leakage testing. l 5.7 Code Case N-504-1, as modified by Code Case N-432 for use of UNS N06052 Alloy 52 weld filler being deposited on the vessel nozzle and Ni-Cr-Fe safe end and attachment welds shall be applicable.
6 SPECIFIC REQUIREMENTS 6.1 Seal welding shall be performed using the manual GTAW process using UNS N06052 Alloy 52 (Code Case 2142) filler metal or SMAW using UNS W86152 Alloy 152 electrode (Code Case 2143). The welders and welding procedures shall be in accordance with ASME lil,1989 Edition, no Addenda.
6.2 The seal weld (s) shall be PT examined in accordance with NB-5000, ASME Ill,1992 Edition, no Addenda, as required by Code Case N-416-1.
l 6.3 The welding consumables shall be in accordance with NB-2400 and NB-2600, ASME Ill,1989 Edition, no Addenda as modified by Code Cases 2142 and 2143..
6.4 The overlay shall be in accordance with Attachments B and C.
6.5 The overlay weld surfaces aid contours shall be prepared suitable for liquid penetrant examination (PT), ultrasonic examination (UT), including preservice ultrasonic examination.
6.6 The temperbead overlay welding operators and welding procedures shall !
be qualified in accordance with Code Case N-432 (see 5.3). The manual welders and welding procedures shall be qualified in accordance with ASME lil,1989 Edition, no Addenda, where temperbead welding is not applicable.
6.7 For the purposes of repair, when the overlay thickness is within 1/8 inch of the low a!Ioy steel nozzle, Machine GTAW temperbead or SMAW half bead welding shall be performed. SMAW repairs in the temperbead portion of the weld, if required, may be performed in accordance with ASME XI,1989 Edition, no Addenda, using the half bead welding process for dissimilar welding. Other repairs, outside the temperbead area, if required, may be performed using manual GTAW or SMAW using procedures qualified in accordance with ASME lil,1989 Edition, no Addenda.
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. Attachm:nt 2 LR-N980231 R ,vi2:d R prir Pirn 6.8 The weld overlay shall be PT examined in accordance with NB-5000,
'ASME lil,1992 Edition, no Addenda.
6.9 The weld overlay shall be UT examined in accordance with NB-5000, ASME 111,1992 Edition, no Addenda per Code Case N-416-1 except that flaw evaluation, if necessary, shall utilize the acceptance criteria of ASME XI,1989 Edition, no Addenda, IWB-3500, as originally specified in Code Case N-504-1. The preservice UT examination shall be performec sing personnel and procedures qualified in accordance with Appendices Vil and Vill, ASME XI,1992 Edition including 1993 Addenda and Code Case N-504-1, modifiec lor UT examination of Ni-Cr-Fe weld overlays to the extent practical.
6.10 A system leakage test at operating pressure and temperature shall be performed prior to or immediately after going into service in accordance with ASME XI,1992 Edition, no Addenda, per Code Case N-416-1.
6.11 The repair will be performed in accordance with a Traveler Core Spray Nozzle Repair Package. The Traveler will specify each operation by sequence with sign-off required when each sequence is completed. FTl QC, PSE&G and ANil review and witness points will be included therein also. All repair procedures used will be included in the final upgraded Traveler package.
6.12 Repair activities by FTl shall be in accordance with FTl ASME XI QA Program. Design activities will be performed by Structural Integrity Associates (SIA) in accordance with their QA program.
6.13 An NR-1 form shall be completed for the repair in lieu of the ASME XI NIS 2 form. NR stamping shall not be required.
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