ML20046A118
| ML20046A118 | |
| Person / Time | |
|---|---|
| Issue date: | 06/18/1993 |
| From: | Conrad H Office of Nuclear Reactor Regulation |
| To: | Strosnider Office of Nuclear Reactor Regulation |
| References | |
| NUDOCS 9307260217 | |
| Download: ML20046A118 (7) | |
Text
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M 181993 4
MEMORANDUM FOR:
Jack R. Strosnider, Chief Materials and Chemical Engineering Branch THRU:
George Johnson, Chief Inservice Inspection Section Materials and Chemical Engineering Branch FROM:
Herbert F. Conrad,- Sr. Materials Engineer Materials and Chemical Engineering. Branch Division of Engineering
SUBJECT:
FORTHCOMING MEETING WITH WESTINGHOUSE CONCERNING LASER WELD DIRLCT TUBE REPAIR OF STEAM GENERATOR DEGRADATION-DATE & TIME:
Tuesday, June 29, 1993 - 8:30'AM to 12:00 Noon LOCATION:
One White Flint North 11555 Rockville Pike, Room IF19 Rockville, Maryland PURPOSE:
_This meeting is to discuss the status of the Westinghouse process to repair steam generator tubes by the controllr.d melting if the tube wall from the inside surface using the-focused energy of a. laser beam. Topics to be discussed are a description of the process, licensing issues and schedule.
PARTICIPANTS *:
NRC WESTINGHOUSE' B. D. Liaw J. Strosnider W. Cullen, et.al.
G. Johnson H. Conrad E. Murphy K. Karwoski R. Hermann C. Serpan T. Reed G. Edison C. Shiraki J. Hornseth Herbert lnf F. Conrad, Sr. Materials Engineer Materials and Chemical Engineering Branch Division of Engineering
- A portion of the meeting will involve discussions-pertaining to proprietary information, and therefore, will be closed to the public.
The nonproprietary portion of the meeting will be open for interested members of the' public, petitioners, intervenors, or other parties to attend as observers pursuant to "Open Meeting Statement of NRC Staff Policy," 43 Federal Reaister 28058, 6/28/78.
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June 16, 1993 MEMORANDUM FOR:
Jack R. Strosnider, Chief Materials and Chemical Engineering Branch Division of Engineering THRU:
George Johnson, Chief Inservice Inspection Section Materials and Chemical Engineering Branch FROM:
Herbert F. Conrad, Sr. Materials Engineer Materials and Chemical Engineering Branch Division of Engineering
SUBJECT:
FORTHCOMING MEETING WITH WESTINGHOUSE CONCERNING LASER WELD DIRECT TUBE REPAIR OF STEAM GENERATOR DEGRADATION DATE & TIME:
Tuesday, June 29, 1993 - 8:30 AM to 12:00 Noon LOCATION:
One White Flint North 11555 Rockville Pike, Room IF19 Rockville, Maryland-PURPOSE:
This meeting is to discuss the status of the Westinghouse process to repair steam generator tubes by the controlled melting if the tube wall from the inside surface using the focused energy of a laser beam. Topics to be discussed are a description of the process, licensing issues and schedule.
PARTICIPANTS *:
NRC WESTINGHOUSE B. D. Liaw J. Strosnider W. Cullen, et.al.
G. Johnson H. Conrad E. Murphy K. Karwoski R. Hermann C. Serpan T. Reed G. Edison C. Shiraki J. Hornseth N
Herbert F. Conr d, Sr. Materials Engineer Materials and Chemical Engineering Branch Division of Engineering j
- A portion of the meeting will involve discussions pertaining to proprietary information, and therefore, will be closed to the public. The nonproprietary portion of the meeting will be open for interested members of the public, petitioners, intervenors, or other parties to attend as observers pursuant to "Open Meeting Statement of NRC Staff Policy," 43 Federal Reaister 28058, 6/28/78.
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MEETING NOTICE DATED:
June 16.1993 DISTRIBtf' ION:
"$ Central Wile M NRC & Local PDRs EMCB Reading T. Murley/F. Miraglia,12G18 J. Partlow, 12G18 SVarga Glainas DMatthews Treed 0GC, 15818 E. Jordan, MNBB3701 ACRS (10), P-135 PA, 2G5 E. Rossi, 9A2 NRR Mailroom, PMAS,12G18 EMerschoff, RII KClark, RII WRussell, 12G18 BDLiaw, 7026 GJohnson, 704 CSerpan, NLS217C MHayfield, NLS217C EHackett, NLS317C KKarwoski, 7D4 JRichardson, 7D26 JStrosnider, 7D4 HCor. rad, 7D4 EMurphy, 7D4 GBurdick, NLS314 RHerman, 704 GEdison Treed CShiraki Mr. William Cullen Westinghouse Electric Corp.
Monroeville Energy Center P. O. B0X 355 Pittsburgh, PA 15230 J
O tO Attachment to NSD-SGO-ATD-92-197 LASER WELDED DIRECT TUBE REPAIR PROCESS FOR STEAM GENERATORS The Direct Tube Repair (DTR) process is based on the restoration of degraded tubes in steam generators by the controlled melting of the tube wall from the inside surface using the focused energy of a laser beam. The process is autogeneous, i.e., does not require a filler metal. The objective is to either heal the cracks completely by melting or restore up to 80 percent of the tube wall thickness.
The process can be used to repair axial or circumferential cracks initiated from either the inside or outside surface of the tube.
Post-weld stress relief is expected to provide corros' ion margins comparable with welded sleeve joints.
Integrity of the repair can be verified using conventional j
Non-Destructive Examination (NDE) methods such as eddy current or ultrasonic testing.
The driving force for the development of the DTR process is that current mechanical methods for addressing steam generator tube degradation, such as plugging and sleeving, have inherent drawbacks.
Both those approaches reduce flow through the generator and, beyond a certain point, adversely affect plant performance. The DTR process has an insignificant effect on the i
thermal-hydraulic performance of the steam generator.
It can be applied to I
address degradxtio7 in tubes that are currently plugged (after deplugging),
above existing sleeved sections of tubing, above dented tubes, and in the peripheral regions of the generator that are currently inaccessible for repair. The DTR process using autogeneous laser welding, therefore, offers a potential means of steam generator life enhancement beyond that achievable with current technologies.
Development work on the DTR process was initiated by Westinghouse at their Corporate Science & Technolooy Center in 1990. A limited amount of testing on the autogeneous nld repair approach yielded encouraging results. Testing performed in 1992 at the Weltz Mill Site included making welds in tubes with simulated axial and circusJerential indications, with secondary side moisture,
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and with oxidized tubes. The effects of stress relief by heat treatment were investigated. The inspectability of the DTR welds.using eddy current and ultrasonic techniques was studied. Mechanical (burst and tensile) and accelerated corrosion tests were also performed on selected weld samples. The results from the testing were positive. The chosen welding process parameters were able to deliver good quality welds. Stress relief was found to provide corrosion margins comparable to sleeved joints. The welds _were inspectable using either eddy current or ultrasonics. Mechanical strength data showed a slight reduction for deep weld repairs, but still within ASME Code limits.
Ongoing work is focused on optimizing weld
) cess parameters prior to developing a comprehensive data base on mechanical properties, corrosion life, residual crack propagation, etc., using welds made on degraded samples.
Both PWSCC and OSDCC degradation mechanisms are being addressed.
An ASME BPVC Code Case Inquiry seeking approval of the DTR process for steam generator tube repair under Section XI rules has also been prepared and issued. The supporting data for securing ASME approval will be the same as the NRC licensing data base.
tic evaluation team inspection, and to c Salem since it Oskarshamn 2. Permanent repair work is already under way is among several plants which had not received an Appen-at Oskarshamn 1, which remains down h-of cracking dix k re-inspection since NRC issued genenc letter 8610 in the piping of the reactor water cleanup system.
on implernentation of Appendix R. Sosne of the others-
-Ariane Saim, Stoc&lm including Nordeast Utilities' Millstone and Connecticut Yankee; Duquesne Light Co.'s Beaver Valley; GPU Nucle-ar Corp.'s Oyster Creek and nree Mile Island-1; Baltimcre RINGHALS MANAGEMENT DEVELOPING Gas & Electric Co.'s Calvert Cliffs; and Rochester Gas &
PLAN TO CUT O&M COSTS BY 10%
Electric Co.'s Ginna-may also be inspected, Hodges said.
Hodges said concerns raised included the applicability A Gnal plan for cuuing costs by 10% through 1995 at of the products' test data to installed ccMigurations and Sweden s Ringhals nuclear station is expected to be ready questions about the scale and verificuion of the tests.
by the end of June, says plant manager Haakan Johansson t
Richard Licht, a 3M Co. spokesman, said the Interam It is likely to include steps for saving about 100-million kronor (U.S.514-million) in mamtenance costs.
system meets current standards and is independently tested.
He said it was tested by Underwriters Laboratory, by the Johansson sold Nucleomes Week that, so far, the plan Southwest Research Institute, and at a testing laboratory in does not can fw reddes omnghals' l.204penu France, in addition to company testing. "1 could go out and w rkforce. A pelimmary cost. cutting plan, obtamed by Nucleonics Week last November, said that the workforce find a situanon where it's not covered by tests," Licht said.
"Any system in the world, you can find a case where it isn't shald be decreased by 50 employees, but did in specify whether that should be through attrition or layoffs. Penon-tested," he said, adding that the vendor can't test every possible field applicanon, but performs bounding tests and nel could also be shifted within the plant. "Maybe we have then uses engineermg judgment.
tm many people in une areas and not craigh in osen "
Johanssa said.
Other companies whose products are expected to under-
' go NRC scrutiny for compliance with Appendix R stan-Each deperment head has been asked to subenit sugges-tims abat where cons can be cut. Johansson said sat no dards include Etemit Inc., Promatec Inc., and Darchem Engineertng Ltd., West said.-David Stel(ox, Washingte single deparment wmld face major cias, bm anoser sarce suggested that substantial savings could come m the mainte-nance department.
Beril Dthne, Ringhals manager for maintenance and COSTS OF SWEDISH ECCS OUTAGE projects, said "it would not be impossible" to save 100-NEARING $100-MILLION, OWNERS SAY million kronor by mid 1995 from Ringhals maintenance Costs resulting from the shutdown of five older genera-staff, utside contractors and materials. He said savings cald be ach,eved through more efficient purchasing and i
tion BWRs in Sweden last year could reach 720-million kronor (U.S.599-million), according to information sup.
uSe of manpower. Safety-related maintenance would not be reduced, he said, nor would the number of maintenance plied by nuclear plant owners.
ne Swedish Nuclear Power Inspectorate (SYJ) ordend employee 8-the reactors kept down in September 1992 after a generic MaJw changes wiH have to be negodated wis de fmr flaw was discovered in the emergency core cooling system trade unims represented at the plant. Ringhals representa-(ECCS). Four of the reactors were down for several tives also discussed the plan with the Swedish Nuclear months, and one is still off line.
Power Inspectorate (SKI) on May 19. He three Ringhals Sydkraft AB, which owns the two Barsebacek BWRs BWRs and one PWR are owned by state utility Vanenfall.
and has a majority interest in the three at Oskarshamn, will Johanssa tmdated be costating drive when he be.
bear the brunt of the cosL Spokesman Stieg Claesson said came Ringhals manager m 1988, and it has mtenstfied since estimates are betwe.en 150- and 200-million kronor for both Vattenfall became a limited liability company in January temporary and permanent modifications to Barsebacek and
-1992 and mcreased its emphasis on profit-makmg.
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Oskarshamn-1 and 2. Modificanons were not required at
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Oskarshamn 3, which is of a more recent design. Genera-sses will cost Sydkraft another 450- to 500-million THREE U.S. UTILITIES TESTING LASER STEANI GENERATOR REPAIR Pennanent repairs at Vattenfall's Ringhals-1 cost about 20-million kronor, according to Ringhals spokesman Goes-At least three U.S. utilities are trying out a Westing-ta 1.arsen Larsen said Ringhals staff had not estimated house laser heating technique which repairs cracked steam generating losses attributable to the ECCS problem because i generator tubes by melting and resolidifying the metal con-the ECCS-related downtime came during a long outage to )
taining the cracks.
repair cracks in the reactor's feedwater pipe linings. nat's ne laser repair technique-the first in situ steam gener-also why Ringhals management chose to make permanent ator repair technique which does not employ other materials rather than temporary repairs.
such as a weld overlay-was tested at Duquesne Light Permanent ECCS repairs will be made at Barsebeeck, Co.'s Beaver Valley 1 last month for the first time. A Du-during this summer's annual maintenance outages, and at quesne spokesman said the utility volunteered its plant to 4
NUCt.EONICS WEEK - May 27,1993 eimm.o asac,*.n mim..m p.-.d
Westinghouse for the demons but he declined to KANSAl SE JULY START FCR comment on whether the utility ously considering MlH AMA M GENERATOR JOB the opuon or discuss what the tration revealed.
Kansai Electnc Power Ca. will begin its first steam Westinghouse officials were unavailable for comment.
L thi W W W m Sobthern Nuclear Operating Co.'s Farley plant is als a schedule recently published by the Osaka-based utility, considering a test of the techmque during an outage this fall The 500-MW PWR has been kept offline since one of and Northeast Utilities, which has put some money mto g
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development of the technology,is considering using the 1991. The replacement is scheduled to be finished in Au-
"dirtet tube repair" on its Connecucut Yankee steam gener-Eust 1994 (NW,14 Feb. '91,1).
ators tubes, according to NRC information.
At that time, the second of seven steam generator re-The demonstration testing at Beaver Valley 1 was placements planned by Kansai should already be underway:
used on outer diameter stress corrosion cracking (ODSCC)
Takahnmn 2 is currently scheduled to start in Janc.ry 1994 at tube suppon plates. The demonstration planned for Far-and finish at the same time as the %hama-2 job.
ley would also be on ODSCC at tube support plates, accord-In September 1994, crews of Kansai and manufacturer ing to Jack Woodard, Southem Nuclear vice president for Mitsubishi Heavy Industries (MHI) are to tackle replace-Farley. ODSCC is the major tube degradation mechanism ment of the steam generators at Ohi 1, a job projected to currently plaguing the industry and prompting requests to take nine months and fmish in June 1995 Whama l's NRC for new eddy current-based acceptance criteria in lieu steam generators would be exchanged between November of the 40% throughwall threshold for sleeving or plugging 1995 and July 1996 Takahama-l's between Dccember cracked tubes (NW,11 March,1).
1995 and August 1996, Mihama 3's between August 1996 William Russell NRC's associate director forinspec-and April 1997, and Ohi-2's in the first 10 months of 1997.
tion and technical assessment, has said the NRC would put ne change-out at Whama 2, the first and longest on its resources into approving generic, degradation-specific the schedule, requires installation of temporary opemngs in acceptance criteria-including eddy current-based criteria the crane wall, reactor outer shielding, and containment for ODSCC-being developed by the Electric Power Re-sauctures. Cutting of main coolant piping and feedwater search Institute (EPRI). He said the agency will not approve and steam piping will get underway this July, as will instal-utility requests for interim criteria that differ from what has lation of the temporary crane wall opening. Actual steam already been approved (NW,13 May,14).
generator carry-out will be acmmplished in January 1994, Woodard said that successful application of the West-w th installation of the new units (now under fabrication) in inghouse direct tube repair technique would not obviate the FebruaryA MacLach PMs need for the eddy current-based alternate criteria, panicular-ly for cracks extending beyond the tube sheet support plates and for other degradation mechanisms.
DAVIS-BESSE'S 61-DAY OUTAGE He said plans for demonstration of the direct tube repair at Farley had not been made firm, but "we're looking at it IS SHORTESTIN UNIT'S HISTORY very favorably." He said Farley would probably test the Toledo Edison's latest refueling outage at Davis-Besse technique on a throughwall crack from ODSCC at the tube was the shortest in the unit's 16-year operating history, suppon plates, but added that he "certamly hoped" the pro-coming in at 61 days. Beginning March I and ending May cess could be used for cracks created by other degadanon 3,it was the Babcock & Wilcox (B&W) PWR's eighth j
mechanisms.
refueling.
Nucleonics Week reported (NW,27 Aug. '92,8) that in addition to refueling, about 3,000 routine mainte-Westinghouse had developed the technique to repair cracks nance activities were performed, including inspection of up to 80% throughwall penetration and was shooting to 100% of the steam generator tubes and some minor plant achieve 100%. De laser works from inside the tubes.
modifications.
According to Woodard, Wutinghouse hopes to sub-Cutting outage time has become a key concem for U.S.
mit a topical repon on the repair te:hnique for NRC review nuclear plants as they struggle to control operating and by the end of the year and at the same time to submit the maintenance (O&M) and capital costs.
technique to the American Society of Mechanical Engineers Jim Michaelif, supervisor of outage management for (ASME) for incorporation into ASME codes. De NRC Davis-Besse, cites detailed outage schedule planning as a review is expected to take six to 12 months.
central reason for the relatively shon refueling.
Westinghouse is not alone in developing the direct tube All of the outage work was scheduled for a 60-hour repair technique. Another company, Wachs Technical Ser-work week, Michaelif explained. That gave workers added vices Inc., has developed a similar technique and Westing-flexibility to deal with the unforeseen problems that almost house and Wachs Technical Services are engaged in a legal always come up during outages. By providing staff and dispute over patents for the technology (NW,1 April,7).
B&W contract workers with detailed descriptions of what Woodard said other utilities are interested in a similar repair each work item involved, individual items could be shifted technique being developed by EPRI which involves a weld within the outage schedule.
overlaye--David Stellfox, Washington To ward against the accident risks that are unique to the 5
NUCLEONICS WEEK - May 27,1993 emntee.atn 4 - - p,w s.a p.
.