ML20248B038
| ML20248B038 | |
| Person / Time | |
|---|---|
| Site: | Callaway  |
| Issue date: | 05/20/1998 |
| From: | Collins S NRC (Affiliation Not Assigned) |
| To: | Randolph G UNION ELECTRIC CO. |
| References | |
| TAC-M95204, NUDOCS 9806010153 | |
| Download: ML20248B038 (22) | |
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e p ast p k_ UNITED STATES e s* j 2,
NUCLEAR REGULATORY COMMISSION WAGHINGToN, D.C. 20eeH001
%,*****[ May 20,1998 f//63 1 Mr. Garry L. Randolph Vice President and Chief Nuclear Officer i Union Electric Company Post Office Box 620 Fulton, Missouri 65251
SUBJECT:
CONCERNS REGARDING UNION ELECTRIC COMPANY'S RESPONSIVENESS TO NRC REQUESTS FOR INFORMATION PERTAINING TO THE REVIEW OF THE PROPOSED AMENDMENT TO ALLOW USE OF THE FRAMATOME ELECTROSLEEVING PROCESS IN THE CALLAWAY PLANT STEAM GENERATORS (TAC NO. M95204)
Dear Mr. Randolph:
By application dated April 12,1996, Union Electric (UE) Company requested approval of an 1 amendment to Facility Operating License No. NPF-30 for the Callaway Plant, Unit 1. This amendment would revise Technical Specification 3/4.4, " Reactor Coolant System," and its .
associated Bases to address the installation of electrosleeves in the Callaway steam generators. The purpose of this letter is to apprise you of the status of your request for approval of electrosleeving steam generator tubes in the Callaway Plant.
The electrosleeving technology, developed by Framatome Technologies Inc., holds the potential to be a safe, cost effective repair method for degraded steam generator tubes.
Union Electric Company is the first licensee to request NRC approval of this technology.
Electrosleeving is a previously unreviewed repair method and NRC staff review of the April 12, 1996, application and supplements provided to date has taken considerable time and resources. Enclosure 1 provides a chronology of UE submittals, NRC staff requests for additional information (RAls), and meetings between the NRC, UE and Framatome Technologies, Inc.
While UE has provided a number of supplements to its April 12,1996, application, the staff has determined that UE, to date, has not provided the technich! basis required to approve the use of [e electrosleeving technology at the Callaway Plant. The main reason that approval has been j l
withheld is that NRC requirements for inspectability of the reactor coolant pressure boundary have not been met in that the ultrasonic testing (UT) technique UE developed does not ensure that ASME Code safety factors are maintained. NRC requirements in this regwd and our l concems with the information provided by UE have been discussed with your staff on a number of occasions during the review process and have been documented in NRC RAls. UE's
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Mr. Garry L. Randolph May 20, 1998 responses to the RAls, the most recent dated February 24,1998, have not adequately addressed these concems. A discussion of the staffs concems regarding the February 24, 1998, response is included in Enclosure 2.
As discussed with you in a telephone conversation on April 29,1998, the staff would be receptive to certain altematives that could lead to the installation of electrosleeves at Callaway Plant while the UT issues are being resolved. One altemative discussed would be based on the current submittais and would be limited for a period of a two cycle amendment. This altemative would involve supplementing your current application to include a request to authorize, for example, the inspection criteria and plugging criteria in the proposed TSs on an interim basis (for two cycles only). Certain aspects of the concems addressed in Enclosure 2 of this letter still would have to be provided, such as the information on question 2 related to quality assurance. We believe that this approach could be supported for two cycles, despite open issues in the UT area, based on the expected corrosion resistance of the electrosleevus relative to inconel 600. At the end of two cycles, the staff would authorize the changes without
- limitation provided all the issues in Enclosure 2 are resolved. The second altemative discussed would be an amendment that would involve either revising your proposed plugging criteria to ,
demonstrate deterministically that ASME Code safety factors will be maintained given your ,
limiting UT measurement uncertainty, or revising your plugging criteria to demonstrate that the. '
probability of tube failure would be acceptably low. This altemative would require a periodic tube pull program more robust than that proposed in your February 24,1998, RAI response. In addition, we would request that a risk assessment be included with the technical specification amendment request for either of the altematives discussed above.
Based on our review of various submittals associated with this technical specification amendment request, the sta'f has some concems with the completeness, technical adequacy and accuracy of these submittals. Several of your submittals were incomplete in that they either neglected to answer questions raised in a RAI, or they indicated that information was not yet developed and therefore was not submitted. Yet in both cases, the questions raised and information requested were not provided to the staff at a later time, until formally requested a second time by the staff. In addition, some of the technical responses to issues raised in RAls !
were technically inadequate, mainly with respect to nondestructive examination issues, in some cases, regulatory requirements were not addressed (e.g., the need to inspect the sleeve for all types of degradation) and in other cases the technical basis provided to address technical issues (e.g., see Question #1 in Enclosure 2 to this letter) was inadequate. Lastly, questions !
have been raised by the staff regarding the quality of the electrosleeve vendor's and your quality assurance review of submittals made to the staff. The staff has identified several examples, two of which were documented in the staffs December 18,1997, RAI, of inaccurate data being supplied to the staff in electrosleeve submittals. Union Electric's performance in this regard must be improved, or the staff will not be able to continue its review of the electrosleeving application.
We are interested in having a meeting to discuss in more detail the status of our review, the attematives outlined above, and your plans relative to the electrosleeving application.
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l Mr. Garry L. Rancolph May 20, 1998 1
l If you have any questions on these matters, please contact Kris Thomas at (301) 415-1362. )
i Sincerely, Original Signed By Samuel J. Collins, Director Office of Nuclear Reactor Regulation Docket No. 50-483 RETRIBUTION:
Docket l
Enclosures:
- 1. Chronology PUBLIC l
- 2. Staff Concems PDIV-2 Reading SCollins/FMiraglia cc w/encis: See next page BBoger BSheron EAdensam WBateman KThomas EPeyton OGC ACRS PGwynn, Region IV CBeardslee TSullivan WJohnson, Region O' MGray
- For previous concurrences see attached ORC Document Name: Electro 2.dra V g- .
OFC PDIV-2 PDIV-2 PDIV-2 PDIV 2* EMCB*
NAME f..NM KThoMI tis WBateman TSullivan l DATE 5 / h / 98 5/9/98 5/ 8 /98 5/k / 98 5/ 6/98 n i n t,,s i.wl. m . - ) iu . e A ,.
OFC hh:h(A) DhhA) $DP(A) T M / brit:D NAME has EAdlnsam BBoger BS hk '
SColl_irV DATE 5 /lY/98 OFFICIAL RECORD COPY 5//3 /98 5 //[/ 98 5//I/98 5 / \'\ / 98
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Mr. Garry L. Randolph May 20, 1998 cc w/encis:
Professional Nuclear Mr. Otto L. Maynard Consulting, Inc. President and Chief Executive Officer 19041 Raines Drive Wolf Creek Nuclear Operating Corporation Derwood, Maryland 20855 P.O. Box 411
, Burlington, Kansas 66839 l Gerald Chamoff, Esq.
l Thomas A. Baxter, Esq. Mr. Dan I. Bolef, President Shaw, Pittman, Potts & Trowbridge Kay Drey, Representative 2300 N. Street, N.W. ~ Board of Directors Coalition t- Washington, D.C. 20037 for the Environment 6267 Delmar Boulevard Mr. H. D. Bono University City, Missouri 63130 l Supervising Engineer i Quality Assurance Regulatory Support Mr. Lee Fritz Union Electric Company Presiding Commissioner Post Office Box 620 Callaway County Court House Fulton, Missouri 65251 10 East Fifth Street Fulton, Missouri 65151 U.S. Nuclear Regulatory Commission Resident inspector Office Mr. Alan C. Passwater, Manager '
8201 NRC Road Licensing and Fuels
, Steedman, Missouri 65077-1302 Union Electric Company l
Post Office Box 66149 Mr. J. V. Laux, Manager St. Louis, Missouri 63166-6149 Quality Assurance Union Electric Company Post Office Box 620 Fulton, Missouri 65251 Manager- Electric Department Missouri Public Service Commission ,
301 W. High l Post Office Box 360 l Jefferson City, Missouri 65102 Regional Administrator, Region IV U.S. Nuclear Regulatory Commission
' Harris Tower & Pavilion 611 Ryan Plaza Drive, Suite 400 Arlington, Texas 76011-8064 i
Mr. Ronald A. Kucera, Deputy Director l Department of Natural Resources ;
P.O. Box 176 Jefferson City, Missouri 65102
I e
ENCLOSURE 1 ,
i j CHRONOLOGY OF UNION ELECTRIC SUBMITTALS AND NRC STAFF REVIEW OF PROPOSED LICENSE AMENDMENT TO ALLOW USE OF ELECTROSLEEVE REPAIR OF i
STEAM GENERATOR TUBES I DATE ITEM April 12,1996 Union Electric submittal requests approval of an amendment to Callaway Facility Operating License NPF-30. This amendment would revise Callaway Technical Specification 3/4.4, " Reactor Coolant System" and its associated Bases to address a the installation of electrosleeves in the Callaway steam generators.
May 28,1996 Framatome Technologies, Inc. and Union Electric personnel meet with NRC staff at the NRC headquarters in Rockville, Maryland to discuss topical report BAW-1021P, "Electrosleeving Qualification for PWR Recirculating Steam Generator Tube Repair," Rev.1. Framatome Technologies Inc. personnel present an overview of the Electrosleeve Program and discuss plating material properties, analyses, performance tests and non-destructive examination (NDE) i I
ultrasonic testing (UT) qualification.
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O July 2,1996 Framatome Technologies, Inc. and Union Electric personnel meet with NRC staff at the Framatone facilities in Lynchburg, Virginia to witness a demonstration of the electrosleeving process. Discussion follows on these topics: (1) material temperature limits and effects, (2) creep curve data and microstructure photographs,(3) details regarding CANDU experience with electrosleeving, (4) experience with installation defect detection and ccrrective measures, (5) types and character of flaws used to verify NDE method, and (6) electrosleeyed tube material response to severe accident conditions.
July 18,1996 Framatome Technologies Inc. provides information to supplement topics of discussion during the July 2,1996 meeting.
July 25,1996 NRC staff issues request for additional information. Information requested in regard to (1) demonstrating detection threshold for stress corrosion cracking (SCC) tube flaws in electrosleeved tubes, (2) potential masking of outside diameter parent tube defects caused by asymmetric variations in sleeve thickness at entrance and exit, (3) criteria and basis for plugging tubes with measurable change in non-destructive examination (NDE) signal response for indications located below electrosleeve, (4) qualification of ability to depth size flaws, (5) influence of electrosleeve wall thickness variation on flaw depth measurement, (6) use of diverse NDE methods following electrosleeving, (7) measurable tolerance level of sleeve thickness following installation, (8) the potential for unbonded regions of an ,
electrosleeved tube to expand over the next operating cycle, (9) ability to remove tube i deposits on tube surface selected for electrosleeving, (10) third party review of ,
overall plating process, (11) controls on parent surface cleanliness and current flow during plating process, (12) quality assurance and control measures on -l dedication of nickel plating material and other consumables used in plating process, (13) l specifications and controls on tube cleaning )
process, and (14) engineering evaluations j and independent confirmatory tests, ,
completed and ongoing, performed by UE.
September 24,1996 UE submits the information in response to l NRC RAI of July 25,1996. With regard to demonstrating detection threshold for stress corrosion cracking (SCC) tube flaws under installed electrosleeves, UE states tests were recently completed and evaluation of results is in progress. Qualification of eddy current testing is also in progress.
I l November 18,1996 Framatome Technologies, Inc. submits letter to senior NRC management stating their view that there were no "show stoppers" l identified to date regarding approval of Electrosleeving technology. Letter requests NRC management to increase priority of in progress review of request.
December 17,1996 The NRC issues meeting notice between NRC staff and UE in regard to electrosleeve amendment request.
Meeting notice includes status of NRC staff review of amendment request. Status identifies that UE has presented metallurgical argument that parent tube indications would not be expected to propagate into nickel tube sleeve. Staff position is that metallurgy alone cannot be used to assure future tube integrity. NDE must also be utilized to determine post-installation quality and continued sleeve integrity. Therefore NDE qualification must be completed to allow the review to continue. The meeting notice provides detail as to incomplete responses in this regard in the UE response dated September 24,1996 to the NRC RAI dated July 25,1996.
December 20,1996 NRC issues letter to Framatome Technologies in response to Framatome letter dated November 18,1996. The letter states that the NRC review is progressing at a reasonable rate considering complexity of issue. Letter reiterates staff questions regarding development of UT crack sizing procedures and eddy current testing qualification. This information is required to continue the staff review of the amendment request.
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l January 15,1997 Union Electric personnel meet with NRC staff I at the NRC headquarters in Rockville, Maryland to discuss the NDE qualification efforts in support of electrosleeving amendment request. UE presents information on NDE qualification approach, l
specifically UT qualification, l
February 5,1997 Framatome Technologies Inc. provides additional information supplemental to the l
information presented during the January 15, 1997, meeting with the NRC staff. The l submittal responds to the specific issues l described in the NRC staff review status summary included in the December 17.,
1996, meeting notice. With regard to demonstrating detection threshold for stress corrosion cracking (SCC) tube flaws under installed electrosleeves, Framatome l Technologies states that tests have been
! completed and results evaluated. Submittal provides evaluation. Submittal also states UT will be used for NDE inspection; therefore i eddy current NDE will not be qualified.
April 28,1997 Subsequent to teleconference with UE and Framatome Technologies personnel on April 14,1997, the NRC staff issues RAI in regard to, in part, (1) assumptions of crack propagation into electrosleeve material and non-destructive examination (NDE) capability to detect and size postulated cracks in the electrosleeve itself, and (2) through wall crack size acceptance limit for crack I propagating into electrosleeve material. 1 l
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May 6-7,1997 Framatome Technologies, Inc. and Union Electric personnel meet with NRC staff at the Ontario Hydro Technologies (OHT) facilities.
The electrosleeve process has been utilized to repair steam generators at the OHT Pickering Nuclear Power Station, Unit 5. The focus of the meeting is the NDE techniques used by OHT to examine electrosleeved tubes following installation.
May 13-14,1997 Framatome Technologies, Inc. and Union Electric personnel meet with NRC staff at the Framatone facilities in Lynchburg Virginia to ;
discuss UT system used to inspect the electrosleeves, observe UT data collection, develop an understanding of the UT analysis process, and review UT data collected from electrosleeve samples used in the qualification of UT data.
June 9,1997 As a follow-up to May 13-14 meeting, UE submits on the docket, information presented to the NRC staff during the subject meeting.
June 9,1997 UE submits additional information in response to the NRC RAI dated April 28, 1997.
August 8,1997 As a result of teleconference with NRC staff on July 29,1997, UE submits additional documents to the NRC staff in regard to electrosleeve burst margins, model for burst pressure versus asial flaw length and depth, and electrosleeve inspection method and results. This information supports responses to the information requested in NRC RAls dated April 28,1997 and June 9,1997.
9 August 13,1997 Framatome Technologies, Inc. and Union Electric personnel meet with NRC staff at the NRC headquarters in Rockville, Maryland.
During the meeting the NRC staff presents .
the following technical issues that require satisfactory resolution to approve the amendment request. Technicalissues presented are (1) UT qualification for depth size cracking, (2) basis for flaw specific structural limits, (3) UT qualification for depth sizing pits, (4) identification of structurally significant flaws in parent tube, and (5) applicability of expansion / transition data set to other regions in the steam generator tube.
September 10,1997 in response to the NRC staff presentation of August 13,1997, UE submits additional information in regard to the five technical issues. A sixth issue, NDE peer review, is also discussed.
November 20,1997 Framatome Technologies, Inc. and Union Electric personnel meet with NRC staff at the NRC headquarters in Rockville, Maryland to review in detail previous submittals related to the amendment request. Questions regarding the structural analysis and the NDE analysis are reviewed. The schedule for the continuing NRC staff review of the amendment request is also discussed.
December 9,1997 Framatome Technologies, Inc. and Union Electric personnel meet with NRC staff at the NRC headquarters in Rockville, Maryland to continue to review previous submittals.
Meeting topics focused on methodology used to perform UT examination of tubes and the disposition of tubes which had significant defect size undercalls using these UT j techniques. The schedule for the continuing )
NRC staff review of the amendment request is also discussed.
December 18,1997 NRC staff issues request for additional information in regard to previous UE submittals, technical reports and meetings. l Information requested regarding (1) technical )
basis for flaw sizing differences between two j datasets, (2) basis, reference and revisions i to various technical supporting data, (3) proposed technical specification changes goveming the future electrosfeeve tube pull program, and (4) various recent UT techniques that better size and detect deep lab grown flaws.
January 9,1998 The NRC staff issues a letter modifying one question from their RAI dated December 18, 1997. The question is in regard to UE's .
intentions to electrosleeve tubes subject to IGA, and supporting information necessary for approval of this application. I February 24,1998 UE sJbmits additional information in response to the NRC RAls dated December 18,1997 and January 9,1998.
e ENCLOSURE 2 STAFF CONCERNS REGARDING UNION ELECTRIC'S RESPONSE DATED FEBRUARY 24,1998, TO THE NRC REQUEST FOR ADDITIONAL INFORMATION BACKGROUND An Electrosleeve is nickel plating,4 - 8 inches long, applied to the inside of a degraded steam generator tube to form a tube sleeve. This type of sleeve is a structural repair, meaning the tube could completely degrade behind the sleeve (e.g.,100% through wall,360' circumferential crack) and the tube could still remain in-service. An Electrosleeve* is different than conventional steam generator tube sleeves. A conventional sleeve is a pre-formed piece of tubing which is inserted into a degraded tube, positioned to bridge the degraded area, and is held in place by expanding a small section of the sleeve diameter or welding the tube and sleeve together. The Electrosleeve* is not pre-formed. it is created inside the tube and directly bonds, along the entire length of the sleeve, to the original tube material through a process called electrochemical deposition.
I The licensee has chosen ultrasonic testing (UT) as the non-destructive examination (NDE) technique to perform post-installation inspections and future in-service inspections. Because the Electrosleeve bonds tightly to the tube along the entire length of the sleeve, UT " sees" both the tube and the sleeve and cannot differentiate between the two. The post-installation UT inspection will detect the original tube flaw. However, that flaw can be dispositioned as acceptable, because it is known to reside entirely in the tube and does not affect overall structural integrity. It is reasonable to assume an extemally initiated tube flaw continues to degrade (i.e., propagate deeper) as the plant operates, because the sleeve does not affect the driving mechanism causing degradation. In a subsequent UT in-service inspection, the original tube flaw will, again, be detected, but wiil appear deeper. This raises the question of whether the original tube flaw has grown into the sleeve, which, obviously, would be of concem, because it would affect the structural integdty of the Electrosleeve .
POSITIONS Union Electric Company 1
The !icensee's initial response to the question of whether the parent tube flaw has grown into the sleeve was that pitting is the only type of degradation expected to occur in the Electrosleeves ; if degradation does in fact occur. The licensee stated that pitting could be "
detected and reliably depth sized by the UT technique to determine whether the Electrosleeve was affected. The licensee's position was that stres'scorrosion cracking (SCC) would not occur in the Electrosleeve*, and therefore, depth sizing of SCC was not necessary. They stated that i SCC in the tube would blunt out at the tube / sleeve interface, and any further degradation would )
occur as pitting of the sleeve (not SCC). This position was based on laboratory corrosion testing and Canadian and Belgian experiences with technology similar to Electrosleeves .
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For reasons discussed below, the NRC staff does not believe the licensee can rely entirely on metallurgical arguments and SCC still needs to be monitored. Therefore, to determine whether the parent tube flaw has grown into the sleeve, the licensee agreed to depth size flaws; including SCC. This requires that the UT inspection technique be qualdied to accurately depth size flaws, including those that may impinge on the sleeve itself.
The licensee has documented their position that they have provided UT data that proves the UT technique is qualified to depth size flaws.
l NR'C Staff I As stated above, the NRC staff does not believe the licensee can rely entirely upon metallurgical arguments to justify that SCC of Electrosleeves will not occur.
p The vendor has performed an extensive number of laboratory corrosion tests on the nanostructured nickel, used to form the sleeve, to demonstrate the resistance of the material to a variety of conditions. The intent of the tests is to mimic, on an acce.'erated scake, conditions l that may be met in field applications. Such tests are valuable tools for screening candidate
! materials, and are reasonable predictors of a material's performance. However, such tests l cannot anticipate all actual conditions. Additionally, although such tests are assumed to duplicate, in an accelerated fashion, with the effects of service conditions, they may inadvertently fail to do so.
The classic example of the failure of such a series of tests to accurately predict the SCC behavior of a material occurred roughly 30 years ago when alloy 600 was studied and eventuaHy selected as the material of choice for steam generator tubes. The material did not crack in the test environments used in the evaluation, it was concluded that the material would be immune to SCC in the anticipated operating environments. After 10 years in service, SCC started to occur in operating steam generators. Now, the materials' performance is well known and alloy 600 laboratory specimens with SCC are routinely produced.
The licensee has pointed to Canadian and Belgian experiences with technology similar to Electrosleeves as support for their amendment request. The staff has determined the Canadian and Belgian applications are sufficiently different than U.S. applications. As such, the operating experience and non-destructive evaluations are not directly applicable to U.S. plants.
A more detailed discussion of the differences between the proposed U.S. applications and foreign applications is presented in Attachment 1.
Nanostructured materials are a new class of materials. The material has never been used as steam generator tube sleeving material in U.S. plants. This material application is still principally a research subject and does not have widespread application or extensive
- performance history. Many of the fundamental properties of this class of materials are !
unknown and thus still the srbject of research resulting in numerous technical papers.
l Consequently, the staff finds that the field application of a new material without concurrent '
application of an effective in-service inspection method would not be a conservative approach with respect to nuclear safety.
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4 As stated above in the " licensee's position," the licensee believes they have submitted data proving they have a UT technique qualified to depth size all flaw types. The staff does not agree the licensee has shown that the UT technique can reliably size stress corrosion cracks.
One aspect of this issue was addressed in the December 18,1997, Request for Additional Information (RAI), Question #1. The staff believes the licensee's documented response to this question does not support the conclusion that the UT technique is qualified to reliably size SCC.
In addition to this fundamental issue, multiple other issues remain open because they were not adequately addressed in the latest RAI response of February 24,1998. All of these issues are discussed below.
ISSUES WITH THE FEBRUARY 24.1998 RAI RESPONSE
, RAI Question #1 The licensee has attempted to qualify UT to depth size all tube / sleeve flaw types (i.e., pitting, i thinning and SCC), but has not proven to the staff that the UT inspection technique is qualified to reliably depth siza SCC. Specifically, the licensee has not proven that a safety significant flaw would not be undersized. The December 18,1997. RAI addressed one aspect of this subject. A discussion of RAI Question #1 and the response are as follows:
The SCC UT qualification data set contains a subset of lab grown SCC. Fourteen of the subset ,
of lab grown SCC samples contained flaws that were essentially 100 percent through the parent i tube. Half of the fourteen samples were undersized significantly more than the proposed NDE I uncertainty value, while the other half were not. During the December 9,1997 meeting, the licensee verbally provided a technical basis for the UT sizing differences. The explanation consisted of a combination of" openness" of the flaw and OD (outside diameter) flaw extent (axial or circumferential). The technical basis provided was that UT error decreased as OD flaw extent increased. Also, as the flaw " openness" increased, the UT error decreased. The licensee verbally stated that parent tube flaws behind Electrosleeves would increase in size (both OD flaw extent and " openness") as the parent tube continued to degrade, and therefore UT errors experienced in the field would decresse as the flaws increased in size. The licensee vertally stated the undersizing errors would not be a safety problem because any safety significant flaws would not be ur' acceptably undersized. The licensee verbally stated the technical basis could be supported with qualification dataset data. The December 18,1997, RAI requested this verbal technical basis be documented along with all supporting data. The licensee's February 24,1998, letter did not support the verbal technical basis detailed above.
The technical basis provided in the February 24,1998, RAI response was not technically adequate. The licensee's arguments were as follows:
e Three (3) out of fourteen (14) flaws were circumferential and the OD flaw extent argument was supported for these. The " openness" argument was not discussed for these three flaws. Eleven (11) out of fourteen (14) flaws were axial and the OD flaw extent argument could not be made because corroborating destructive examination data (i.e., OD extent) was not available. The
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- openness" argument was put forth, but for only eight (8) out of eleven (11) flaws. The remaining three (3) were not discussed.
NRC staff evaluation: Both the " openness" and OD flaw extent arguments need to be made for all flaws. It is not appropriate to pick and choose the argument to be used for each flaw based on the results obtained.
In addition, the licensee was asked to provide descriptive photographs of etched samples of each of the 14 flaws (to help support the " openness" argument).
Photographs were provided in the RAI response, but the staff was unable to correlate the photographs to each of the flaws listed in Table Q1.2 (e.g., Tube TS-2 has 5 axial flaws that were depth sized for the UT qualification database, as seen in Table Q1.2 of the RAI response). The RAI response includes ,
l photographs of flaws at eight different azimuths. I i The staff was not able to determine which of the 5 flaws correlatos with which of i the eight photographs. Therefore, the staff was not able to draw any l independent conclusions on the " openness" argument.
e The eleven axial flaws in the lab grown SCC data subset are 1/6 to 1/4 the structural limit when both flaw depth add length are considered, and even when utilizing worst-case NDE depth errors, the flaws are well below the structural i
, limit.
NRC staff evaluation: Length is not considered when determining whether a tube should be removed from service. This subset of data is the only set containing deeper flaws. Therefore it is the only data available to determine the i capability of UT to accurately depth size deeper flaws. The data cannot be ignored because the flaws are smaller than the structural limit. The flaws, when the worst-case NDE depth errors are added to the depth, must remain below the structural limit without regard to flaw length.
e Pre-sleeving UT errors are much lower than post-sleeving UT errors. For these specific flaws, which were initiated from the inside diameter, the process of Electrosleeving* causes errors to increase. This is because the OD flaw extent is very small, smaller than would be expected in the field.
NRC staff evaluation: There is no evidence to show that deeper, larger flaws with Electrosleeves installed would be sized more accurately.
Based on the explanation abcva, the staff is not confident the licensee has a technical basis for the UT sizing differences. Therefore, the staff cannot conclude the UT technique is qualified to reliably depth size stress corrosion cracks. The licensee has not proven that safety significant flaws would not be undersized.
w 5-RAI Question #2 The NRC staff raised a QA issue, because it appeared inaccurate data was being supplied to the staff in Electrosleeve submittals. The licensee's RAI response admitted data was being inadvertently transposed and initiated a Corrective Action Request (CAR) to address this issue.
However, all the actions required to address this issue and close the CAR were not complete.
The NRC staff cannot complete the license amendment request review until the CAR actions are complete, assurances are provided that all other docketed information is correct,' and steps have been taken to prevent recurrence. in addition, the CAR discusses preparation of an unknown action called an LDA. The licensee needs to explain what the acronym "LDA" stands for and what an LDA is.
RAI Question N The licensee verbally stated the UT examinations are only performed from one direction and UT inspection results would not improve if UT examinations were performed from two directions.
The NRC staff requested the licensee to submit a table containing data from the seven flaws that were significantly undersized (as discussed in Question #1 above). The staff indicated that the table should contain UT examination results, scanned from two directions, and destructive examination results. This information was requested because it would support the assertion that two-directional scanning would not improve UT examination results. 3 The licensee's RAI response indicated the seven flaws were scanned only from one direction, 4 because the tube samples contained roll geometry which prohibits acquiring meaningful data )
_ from two directions. Instead, the licensee provided a two-directional evaluation of three Salem !
Unit 1 steam generator pulled tubes in Attachment 4 of the February 24,1998, RAI response. I For the staff to complete its review of this response the licensee needs to:
(a) provide the destructive examination flaw depths for each of the flaws provided in the tables, as was requested in the original RAI, (b) correlate each of the Salem Unit 1 flaws in the February 24,1998, tables to the Salem Unit 1 flaws in Table 1.1 of the September 10,1997, submittal, so that the staff can understand how the February 24,1998, data corresponds to previously i submitted data, and (c) explain the headings " Maximum Depth" and " Depth Size" for the tables provided.
RAI Question #6 l- The staff requested that Union Electric propose a tube pull program that is both condition-based l and time-based. The condition-based aspect would require a tube pull if NDE provides an indication that Electrosleeve degradation is occurring. The time-based aspect establishes periodic tube pulls performed over the life of the plant for continued assurance that sleeve degradation is not occurring which is not being detected or correctly sized by NDE.
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i The licensee proposed a condition-based program that would satisfy the staffs requirement, only if it was coupled with an adequate time-based program. However, the proposed time-based program does not meet the staffs intent.
The proposed time-based program would require one tube to be pulled (at any plant) at the end of five effective full power years (EFPY). If one Electrosleeved* tube was pulled, based on degradation, at any other U.S. plant prior to five EFPY, then the time-based program is not required. This is an inadequate number of tube pulls to assure the integrity of the remaining sleeves.
The staffs concems, which prompted the request for a tube pull program, were: (1) some weaknesses in the UT qualification data, and (2) lack of experience with nanocrystalline nickel material in the. steam generator, especially as it remains in-service over a long period of time.
The time-based program, as currently proposed by the licensee, would not address the staffs concems. The proposal for a time-based program should be revised and submitted.
RAI Question #7 The staff requested the licensee to update the Electrosleeve topical report to reflect new data and changes to Revision 1 of the topical report. The licensee proposed multiple subjects be incorporated into the revised topical report, pending NRC staff review of the February 24,1998, RAI response. The general method proposed for the update is acceptable to the staff. The staff had the following comments with respect to the details described:
, e it does not appear that information from the February 24,1998 RAI response will be included in the revision. If this is the case, the February 24,1998, RAI response should be reviewed again because the staff believes that some of the data should be included (e.g., discussion on dent limits and basis for the limits
[RAI Questions #9 and #10), and discussion on the IGA issue [RAI Question
- 11]).
e The staffs understanding is that Electrosleeves* cannot be applied in the U-Bend region because UT has not been qualified for this region, and because the licensee does not have equipment that can install Electrosleeves in that region. This distinction should be stated in the topical report. If the licensee, in fact, intends on applying Electrosleeves to the U-Bend region, the licensee needs to provide a discussion of the technical basis to support this.
RAI Question #8 The staff originally requested the licensee to modify the Callaway technical specifications (TS) to require a 20 percent initial inspection scope of each type of installed sleeve. The licensee responded in the February 24,1998, RAI response that TS Table 4.4-3 already requires a sample size of 20 percent, and Note 1 of that table requires that each repair method be considered a separate population.
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The staff has reviewed Note 1 of TS Table 4.4-3. The note specifically states that "Each repair method is considered a separate population for determination of scone exoansions." The table does not require cach repair method be considered a separate population for the initial inspection scope (i.e.,1" sample inspection), which is what was requested in the original RAl.
The licensee needs to revise Table 4.4-3 accordingly.
RAI Questions #9 and 10 The. staff requested a discussion of the UT technique's ability to inspect dented intersections, limits on the size of dents that can be reliably inspected, and a discussion on the size of the dented Salem Unit 1 samples listed in the response to issue #1 in the September 10,1997, submittal.
The licensee presented information related to these issues in Attachment 5 of the February 24, 1998 RAl response. The staff's review of this attachment raised the following questions:
1 e is the .023" maximum dent depth limit a pre-sleeve or post-sleeve dent depth?
e There appears to be several inconsistencies between the data in the February 24,1998, RAI response and the September 10,1997 submittal. For example:
. Tube 23-59 is listed as having one dented intersection in the September 10,1997 submittal.
Tube 23-59 is not discussed in the February 24,1998 submittal.
- Tube 24-47 is listed as having two dented intersections in the September 10,1997 submittal.
Tube 24-47 is listed as having one dented intersection in the February 24,1998 submittal.
These are just two examples of inconsistencies between the two submittals. The licensee needs to (1) provide a table that correlates the data from the September 10, 1997, submittal with the data from the February 24,1998, submittal, (2) provide a discussion and basis for the inconsistencies between the two submittals, and (3) provide in the table a list of all flaws in each dented region (UT sizing, destructive examination sizing, and errors between the two). This information will enable the staff to understand l how the February 24,1998 data corresponds to previously submitted data.
RAI Question #12 The licensee's response to Question #12 states that " Union Electric will commit to not install an Electrosleeve" in these periphery tubes near wedge supports." It is also stated that I approximately 100 tubes would be excluded from the " candidate list to be Electrosleeved .
Although the response clarified the licensee's position on the issue of tube locking, the response failed to identify which tubes would be excluded per the above noted commitment and did not provide the technical basis defining the locked tube exclusion zone. The licensee needs to provide these additional details on the exclusion of tubes due to locked tube effects, and propose specific text to incorporate exclusion requirements into the license for the Callaway Plant.
RAI Question #13 At a meeting on December 9,1997, the license indicated that a peer review of the UT process and qualification identified, in part, that additional pit and disbond samples were necessary for
! EPRI Appendix J qualification statistical requirements. The staff requested that the licensec l submit the UT and destructive examination results from the additional samples. This information will provide additional assurances to the staff that the UT errors previously assumed for sizing of pits and areas of disbond are still accurate.
i in the February 24,1998, RAI response, the licensee indicated that " Preliminary results support previously reported capability to depth size pits with UT. The results of this work will be provided when completely documented." The results on depth sizing of pits have not been submitted yet. In addition, results from the additional disbond samples were not discussed or submitted. The licensee needs to submit the results from the pit and disbond samples as originally requested.
RAI Question #14 in the response to Question #14, the licensee indicated that contingency plans existed to permit !
the use of honing to improve the surface finish of the Electrosleeve". The licensee needs to )
provide a detailed process description, description of any inspection of the honing results, and applicable field QA/QC checks.
l The licensee also needs to provide details of metallurgical tests that were conducted on honed samples to determine the effect of the honing on the nickel layer and the effect, if any, upon the corrosion resisting performance of the nickellayer, Speedically, address the questions of whether or not the honing results in a cold worked or othenvise altered surface layer and whether this layer affects the corrosion resistance of the nickel. Have measurements of the residual stress that results from the honing operation been performed?
RAI Question #15 Prior to the December 9,1997, meet % the NRC staff reviewed UT Procedure 54-ISI-168, Rev.
1 dated January 28,1997, and not: : some deficiencies (such as critical UT process l parameters relevant to the UT qualification process which were not clearly defined). These l deficiencies were discussed with the licensee at the December 9,1997, meeting at which time the licensee indicated the procedure was in the process of being updated based on findings i
e O
9 (some of which were similar to the staffs comments) from a peer review. In the December 18,1997, RAI the staff requested that the license submit a copy of the updated procedure and the report containing the peer review findings and/or recommendations.
In the RAI response, the licensee acknowledged that the UT procedure was being revised, but stated that the revision was not complete. The licensee also indicated that Revision 1 of the procedure represents the procedures in place for the UT qualification data presented in previous submittals. The peer review report was not provided, nor was it discussed.
- Although Revision 1 represents the procedures in place for the UT qualification data presented in previous submittals, a copy of the revised procedure was requested because the staff determined that Revision 1 contained some deficiencies which should be addressed prior to implementing the UT process in field applications. The staff would like to independently review the revised procedure. The licensee needs to submit the UT procedure when it has been revised. q e During the December 9,1997, meeting the staff requested that Revision 1 of the procedure be formally submitted on the docket, because it was being reviewed in support of the license amendment request. The licensee needs to submit Revision 1 on the docket.
- A copy of the peer review report was requested, and still is desired, to enable the staff to determine how the licensee rerponded to issues raised by the peer review.
Attachment:
Comparison l
l
o ATTACHMENT COMPARISON OF PROPOSED U.S. APPLICATIONS TO CANADIAN AND BELGIAN APPLICATIONS e The Canadians have electrosleeves applied to a maximum of 14 tubes that are in-service. These tubes have not been in-senrice for a long period of time (< 6 calendar ,
years) and the only type of degradation occurriag on the Monel parent tube is pitting. '
Therefore, the UT technique is only optimized for pitting, not SCC.
e The Belgians have a thin, non-structural, nickel plating applied to a large number of -
tubes. U.S. application will be thicker, structural sleeves.
e The Belgians only applied nickel plating to tubes with primary side cracking and are not experiencing any secondary side degradation in the region the nickel plating was applied. U.S. application will be to tubes with flaws initiating from both the primary and secondary side. This is a significant difference, because primary side cracking which has been nickel plated may not continue to propagate since the flaw is no longer open to the environment which initially caused the cracking. Secondary side flaws remain open to the original environment even after electrosleeving, and therefore, are much more likely to continue to propagate. j e The Belgians only monitor the length of the flaw, because their plugging criteria is length l based, not depth based like U.S. plants. Because of this, through-wall flaws are considered acceptable (as long as leakage is limded), and the actual condition of the l sleeve material is not monitored (except by monitoring for leakage).
- The Belgians discontinued in-service inspections of the nickel plating after a couple l cycles because the lengths of the primary side cracks were not increasing. Therefore, there has been no long-term monitoring of nickel plating material, t
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