ML20086K631
| ML20086K631 | |
| Person / Time | |
|---|---|
| Site: | Crane  |
| Issue date: | 10/27/1983 |
| From: | Dircks W NRC OFFICE OF THE EXECUTIVE DIRECTOR FOR OPERATIONS (EDO) |
| To: | Doroshow J THREE MILE ISLAND ALERT |
| Shared Package | |
| ML20079G498 | List:
|
| References | |
| FOIA-83-243, FOIA-83-A-18, RTR-NUREG-CR-0718, RTR-NUREG-CR-718 SECY-82-502, NUDOCS 8402060028 | |
| Download: ML20086K631 (7) | |
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UNITED STATES N blb
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NUCLEAR REGULATORY COMMISSION n
l WASHINGTON, D. C. 20555 k.....,/
Ol!T E 7 23 Docket No. 50-289 Ms. Joanne Doroshot Three Mile Island Alert, Inc.
IN RESPONSE REFER 315 Peffer Street TO F0!A-83-A-18 Harrisburg, PA 17102 (F01A-83-243)
Dear Ms. Doroshow:
This is a further response to your letters dated July 30 and August 4, 1983, appealing Mr. J. M. Felton's letter of June 29, 1983 which denied-in-part your Freedom of Information Act (F0IA) request for documents which discuss, evaluate, analyze, or explain the causes or repair of steam generator problems at TMI-1.
You specifically appealed the withholding of five documents identified in Mr. Felton's June 29, 1983 letter; the withholding of documents characterized as proprietary for which only transinittal letters can be located in the Local Public Document Room (LPDR) and which were not specifically identified or denied under the Freedom of Information Act; and the fact that all documents subject to your request were not identified although certain documents could be located in the LPDR.
The first and third part of your appeal was handled in my letter to you dated October 3, 1983.
In that letter, I stated that approximately 60 documents were being located and reviewed to determine if they were subject to your request and whether or not they could be released. The search and review process has now been completed and we have determined that 52 documents are subject to your request. The 45 documents listed on Appendix A to this letter are enclosed.
Portions of the 7 documents listed on Appendix B are being withheld from public disclosure pursuant to exemption (4) of the Freedom of Information Act (5 U.S.C. 552(b)(4)) and 10 CFR 9.5(a)(4) of the Comission's
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regulations. The nonexempt portions are enclosed.
Babcock and Wilcox considers the withheld information to be company confidential (proprietary) infonnation the release of which would cause substantial harm to their competitive position.
Babcock and Wilcox has submitted affidavits to substantiate this position.
The 7 documents and the affidavits have been reviewed by the NRC staff and it has been determined that the denied portions of these documents clearly fall within exemption (4) of the F0IA.
e40206o020 831027 PDR FOIA DDROSHB3-A-18 PDR
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Ms. Joanne Doroshow Since I have made the above determinations, this letter represents the final agency action on your FOIA request. Judicial review of this decision is available in a district court of the United States in either the district in which you reside, have your principal place of business or in the District of Columbia.
Sincerely, l
W liam'J. Dircks i
Executive Director for Operations
Enclosures:
As scated i
Re:
FOIA-83-A-18 APPENDIX A 1.
12/29/82 POLICY ISSUE - STATUS OF CERTAIN NON-HEARING ISSUES ON TMI-l - SECY-82-502 (3 pages) 2.
8/6/82 Letter to D. D. Macdonald, Ph.D from V. Benaroya re: SULFUR REMOVAL FROM REACTOR COOLANT SYSTEM SURFACES AT TMI-l (2 pages) 3.
7/6/82 Letter to Conrad McCracken from M. J. Graham re: OTSGs (1 page) 4.
3/24/83 Letter to B. Turovlin from C. Auerbach re: DRAFT TECHNICAL EVALUATION REPORT w/ enclosure (16 pages) 5.
8/30/82 Letter to V. Benaroya from D. D. Macdonald re: REVIEW 0F B&W DOCUMENT NO. 77-1135317, " EVALUATION OF TUBE SAMPLES FROM TMI-1" (4 pages) 6.
10/5/82 Letter to J. Lee from H. R. Denton re: CORROSION PROBLEMS IN THE TMI-l STEAM GENERATORS (3 pages) 7.
8/3/82 Memo for H. McVeagh from V. Benaroya re: PRINTING COSTS FOR TMI-l STEAM GENERATOP TUBES DESTRUCTIVE EXAMINATION REPORT (1 page) 8.
9/10/82 Memo for V. Benaroya from C. McCracken re: STATUS UPDATE FOR TMI-1 STEAM GENERATOR REPAIRS W/ Attachments (11 pages) 9.
9/17/82 Memo for D. Eisenhut frun R. Vollmer re: REPAIR OF TMI-l STEAM GENERATOR TUBES (1 page) 10.
10/26/82 Memo for R. H. Vollmer from P. Wu re: EXTENSION OF PNL TECHNICAL ASSISTANCE TO THE DIVISION OF ENGINEERING
" EVALUATION OF TMI-1 STEAM GENERATOR CORROSION" (1 page) 11.
10/27/82 Memo for V. Benaroya from C. McCracken re: TMI-1 S.G.
CORROSION / REPAIR EXAMINATION OF REMOVED TUBES (1 page) 12.
5/20/82 Memo to J E. ibtheson from W. A. McInteer et. al. re:
TMI-l REC 0VERY - RNS RETAINER EXAMINATION (22 pages)
- 13. 6/30/82 FINAL REPORT ON FAILURE ANALYSIS OF INCONEL 600 TUBES FROM OTSG A AND B 0F THREE MILE ISLAND UNIT-1 by A. K. Agrawal, et. al. (136 pages) 14.
11/18/82 Note to V. Benaroya from C. McCracken re: TMI-l 0TSG STATUS UPDATE w/ enclosure (63 pages)
- 15. 1/24/83 Memo for D. G. Eisenhut from R. H. Vollmer re: SIGNIFICANT HAZARDS DETERMINATION PERTAINING TO RESTART OF TMI-l SUBSEQUENT TO OTSG REPAIRS w/ enclosure (13 pages)
Re:
F01A A-18 APPENDIX A 16.
1/25/83 Memo for D. Vassallo from F. J. Congel re: QUESTIONS PERTAINING TO RETURN TO SERVICE OF 1MI-l STEAM GENERATORS w/ attachment (3 pages) 17.
3/8/83 Memo for L. Frank et. al. from C. McCracken re: PREPARATION OF TMI-l SER FOR RESTART SUBSEQUENT TO THE OISG REPAIRS w/ attachments (25 pages) 18, 3/25/83 Memo for R. H. Vollmer from P. Wu re: EXTENSION OF PNL TECHNICAL ASSISTANCE TO THE DIVISION OF ENGINEERING " EVALUATION OF THREE MILE ISLAND UNIT NO. 1 STEAM GENERATOR CORROSION" w/ attached memo (2 pages) 19.
4/4/83 Memo for D. Eisenhut from R. Vollmer re: SCHEDULE FOR SER SUBMITTAL ON TMI-l STEAM GENERATOR (2 pages)
- 20. 4/20/83 Meno for V. Benaroya from B. D. Liaw re: TMI-l - SER FOR RESTART SUBSEQUENT TO ONCE-THROUGH-STEAM GENERATOR REPAIRS w/attachaent (7 pages)
- 21. 4/21/83 Note to L. Frank et. al. from C. McCracken re: SCHEDULE FOR TMI-l RESTART SER (1 page)
- 22. 5/19/83 Memo for D. G. Eisenhut from H. L. Thompson, Jr., re: THI-l STEAM GENERATOR REPAIR REVIEW STATUS (1 page) 23.
5/23/83 Memo for G. Lainas from W. V. Johnston re: SAFETY EVALUATION OF POST ACCIDENT SAMPLING SYSTEM 0F THREE MILE ISLAND UNIT NO. 1 w/ enclosure (11 pages) 24.
5/23/83 Memo for D. G. Eisenhut from R. H. Vollmer re: TMI-l STEAM GENERATOR REPAIR SAFETY EVALUATION (1 page) 25.
5/24/83 Memo for G. C. Lainas from W. V. Johnston re: SAFETY EVALUATION OF THREE MILE ISLAND UNIT NO. 1 FOR RETURN TO SERVICE AFTER REPAIR OF OTSG CORROSION w/ enclosure (61 pages)
- 26. 8/17/82 Memo for V. Benaroya from C. McCracken re: STATUS UPDATE FOR TMI-l S.G. REPAIRS (3 pages)
- 27. 4/21/83 Memo for W. V. Johnston from V. Benaroya re: TMI-l THIRD PARTY REVIEW MEETING
SUMMARY
(2 pages)
- 28. 6/14/82 Letter to S. Pandy from S. S. Bajwa re: TENTATIVE WORK ASSIGNMENT "J" w/ enclosure (4 pages)
- 29. 6/17/82 Letter to S. S. Bajwa from S. Pandey re: PROPOSED PROGRAM, SCHEDULE, AND LEVEL OF TECHNICAL EFFORT REQUIRED FOR ACCOMPLISHING TENTATIVE WORK ASSIGNMENT "J",
EVALUATION OF TP.1-1, STEAM GENERATOR TUBE SEALING PROGRAM (5 pages) l J
Re:
FOIA-83-A-18 9
APPENDIX _A 30.
5/9/83 Memo for J. F. Stolz from H. Brent Clayton re: TMI-l STEAM GENERATOR TUBE RUPTURE GUIDELINES AND PROCEDURE REVIEW (1 page) 31.
6/28/82 Memo for R. Bosnak from J. Rajan re: TMI-1 STEAM GENERATOR TUBE TUBESHEET REPAIR - MEETING
SUMMARY
w/ attachments (7 pages) 32.
7/27/82 Handwritten Letter to H. Denton from J. H. White, III, re:
INFORMATION SENT TO MR. LEWIS (1 page) 33.
5/7/82 Letter to H. Denton from M. I. Lewis re: TMI-l REACTOR TEST PROGRAM (3 pages) 34.
10/25/82 Handwritten Letter to D. G. Eisenhut from A. Rosenberg re:
LETTER TO M. LEWIS w/ enclosure (2 pages)
- 35. 4/1/83 Letter to H. Denton from J. Lee re: LETTER TO COMMISSIONER GILINSKY (1 page) 36.
3/31/83 Letter to V. Gilinsky from J. Lee re: PUBLIC FORUM ON NUCLEAR POWER (2 pages) 37.
4/24/83 Letter to J. E. Stolz from D. E. Hossler re: REGULATORY CONNECTION TO TMI-1 w/ enclosures (8 pages) 38.
5/16/83 Letter to H. Denton from D. E. Hotsler re: LETTER SENT TO JOHN STOLZ (1 page) 39.
7/9/82 Memo for D. Eisenhut from R. Jacobs re: TMI-1 STEAM GENERATOR REPAIR PROGRAM (1 page) 40.
3/25/83 Memo for R. Vollmer from D. Eisenhut re: SCHEDULE FOR SER SUBMITTAL ON TMI-1 STEAM GENERATOR (1 page)
- 41. 4/11/83 Memo for B. H. Clayton from J. F. Stolz re: REQUEST FOR TMI-1 STEAM GENERATOR TUBE RUPTURE PROCEDURES AND GUIDELINES REVIEW w/ enclosure (12 pages) 42.
5/17/83 Memo for R. Vollmer et. al. from D. Eisenhut re: TMI-l STEAM GENERATOR REPAIR REVIEW STATUS (2 pages) 43.
5/9/83 REQUEST FOR TECHNICAL SPECIFICATION CHANGE TO PERMIT STEAM GENERATOR REPAIRS w/ attachment (15 pages) 44.
12/29/82 Memo for The Comissioners from W. J. Dircks re: STATUS OF CERTAIN NON-HEARING ISSUES ON TMI-l (3 pages)
1 Re: F01A-83-A-18 APPENDIX A 45.
12/20/82 Memo for D. MacDonald et. al. from C. McCracken re:
REVIEW 0F GPUNC TOPICAL REPORT 008 (RETURN TO SERVICE AFTER STEAM GENERATOR REPAIR) (2 pages)
Re:
F01A-83-A-18 APPENDIX B 1.
1/20/83 Letter to J. F. Stolz from H. D. Hukill re: 0TSG REPAIR KINETIC EXPANSION TECHNICAL REPORT w/ attachment - Three-Mile Island Ur.it 1 ONCE-THROUGH STEAM GENERATOR REPAIR-Kinetic Expansion Technical Report by J. P. Moore, et. al.
(GPUN-TDR-007 - BAW-1760) (104 p. aces) i 2.
3/31/83 Letter to J. F. Stolz from H. D. Hukill re: STEAM GENERATOR REPAIR w/ attachments 1) Topical Report 008, Rev. 2 and
- 2) Affidavit - Transmitting: 3/29/83 ASSESSMENT OF TMI-1 PLANT SAFETY FOR RETURN TO SERVICE AFTER STEAM GENERATOR REPAIR TOPICAL REPORT 008, Rev. 2 by T. M. Moran - Project No. 500 51712 (166 pages) 3.
8/20/82 Letter to D. G. Eisenhut from H. D. Hukill re: 0TSG TUBE REPAIR PROGRAM w/ enclosures 1) Affidavit and 2) TMI-1 Once Through Steam Generator Repair Safety Analysis - Transmitting:
8/20/82 TMI-l ONCE TRHOUGH STEAM GENERATOR REPAIR SAFETY ANALYSIS - ATTACHMENT TO 5211-82-200 (42 pages) 4.
10/5/82 Letter to D. G. Eisenhut from H. D. Hukill re: 0TSG TUBE REPAIR w/ enclosures TMI-l Steam Generator Repair Safety Evaluation, Rev. 1 - Project No. 5000 51712 by M. J. Gt-aham, et. al. dated 9/30/82 (39 pages) 5.
12/10/82 Letter to D. G. Eisenhut from P. R. Clark re: TMI-1 OTSGs -
Transmitting: 12/7/82 Assessment ot THI-l Plant Safety for Return to Service After Steam Generator Repair Topical Report 008, Rev. 1 - Project No. 5000 51712 by T. M. Moran (114 pages) 6.
4/20/83 Letter to J. F. Stolz from H. D. Hukill re: TMI-l Steam Generator Repair Report w/ enclosures - Transmitting: Three-Mile Island Unit 1 Once-Through Steam Generator Repair -
Kinetic Expansion Technical Report (122 pages) 7.
10/25/82 Letter to J. F. Stolz from H. D. Hukill re: TMI-l 0TSG Repair Drawings w/ enclosures (10 pages)
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,#'reco,is December 29. 1982 SECY-82-302 POLICY ISSUE (Information)
For:
The Commissioners From:
William J. Dircks Executive Director for Operations
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Sebject:
Status of Certain Non-Hearing Issues on TMI-l Purcose:
To inform the Commission of the status of staff review for TMI-l on the auxiliary feedwater. header problem and the make-up nozzle cracking problem that occurred on several B&W plants; and the steam generator tube problem on TMI-1 as directed by the Commission in its Order dated July 16, 1982 (CLI-82-12).
Background:
By Order dated June 30, 1982, the Atomic Safety and Licensing Appeal Board for the TMI-l restart proceeding requested authorization from the Commission to hear three issues sua sconte.
Those is:ues relate to:
(!) the pos-l sible distorting of the auxiliary feedwater header, (2) whether there has been any cracking in high pressure injection or make-up system nozzles or thernai sleeves and (3) the repair of the corroded steam generator tubes.
3y Order dated July 15,198? (CLI-82-12), the Commission denied the Appeal Board's request but directed the staff to thoroughly examine these issues and provide its analyses and findings to the Commission prior to the time the Commis-sion is to make its decision on the restart of TMI-1.
The folicwing is the current status of the three issues.
Tr.e requested staff findings with respect to the first two issues are recorted below.
The staff review and findings regarding repair of steam generator tubes will be completed l
after hot functional testing, now scheduled for late April 1983.
Contact:
R. Jacobs, NRR X27a71 Y' ?
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Discussion: The auxiliary feedwater header problem identified by the Appeal Board refers to distortion of the internal auxiliary feedwater header experienced at Davis-Besse, Oconee 3 and Rancho Seco.
The internal header, which is installed in Davis-Besse, Rancho Seco, Oconee 3, Midland 1 and 2 and TMI-2, is rectangular and encircles the tube bundle. The rest of the B&W plants including TMI-l use an external feedring with seven nozzles penetrating the steam generator shell and shroud.
Hence, this problem is not applicable to TMI-1. The corrective action completed at the affected B&W plants involved stabilizing the internal header and installing an external feedring similar to that used at TMI-1.
The make-up nozzle problem in B&W plants refers to cracking that occurred in the makeup nozzles to the reactor coolant system cold legs of four of the B&'d plants. The Commission was informed of the status of tnis problem in SECY-82-186 dated May 7, 1982 and SECY-82-186A dated July 23, 1982.
The problem appeared to be related to the condition of the nozzle thermal sleeve.
In each instance where nozzle cracks were detected, the associated thermal sleeve had been loose or in the case of Rancho Seco, the sleeve was missing.
All four HPI nozzles were inspected at TMI-1 and no degradation was detected. Additionally, it was confirmed that the thermal sleeves were in place. Hence, no additional short term action is considered necessary for TMI-l prior to restart.
A B&W Owners Group task force is pursuing whether any additional generic action is necessary for the B&W plants.
The task force final report is due to be completed in January 1983.
It is expected to recommend augmented in-service inspection in B&W plants to provide long term assurance against further degradation.
The staff agrees with this recommendation and will be reviewing each licensee's submittal when received.
With respect to the steam generator problem, the staff's review is continuing.
On October 13, 1982, the staff issuad a safety evaluation supporting our finding that GPU may proceed with repairs of the steam generators, but that NRC approval was necessary before any subseauent operation.
GPU is approximately midway through the kinetic expansion program with cleanup of debris, plugging of approximately 800 tubes (354-tubes previously plugged) and steam generator testing required to complete the repairs.
Additionally,
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GPU plans to mill off the top end of the tubes where they protrude through the upper tubesheet since a number of these tube ends have been breaking off from the expansions due to defects in the heat affected zone of the seal weld.
GPU anticipates completing the above repairs and cold testing by mid March 1983.
Following the repairs, GPU may conduct desulfurization of the reactor coolant system, if determined to be necessary, to be followed by hot functional testing which GPU has targeted for completion by late April 1983.
On December 10, 1982, GPU submitted their safety evaluation concluding that TMI-1 can be safely returned to service once the repairs and associated activities have been completed satisf actorily. The staff position as stated in SECY-82-35A
' dated July 19, 1982 is that unreviewed safety questions are.
involved and a license amendment is needed to modify the Technical Specifications before the steam generators can be declared " operable". The staff intends to ccmplete its review and issue its final safety evaluation after completion of steam generator hot testing.
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)s Wilitam J.. Dircks Executive Director for Operations G
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Central File CMEB Reading File CHEB TMI-1 File 42
, [ //f'oC-Digt,y D. Pacdonald Ph.D 1143 Regency Drive Coluabus. Ohio 43220
Dear Dr. Macdonald:
Subject:
Sulfur Removal From Reactor Coolant System Surfaces at TMI #1 Thank you for your letter of Jely 23, 1982. % expressed concern that sufficient effort is not being focused by GPUN on sulfur removal from system surfaces at TMI fl. We concur with your recommendation that "if GPUN does not intend to desulfkrize, that they be required to present argu-monts to support their posities." Nousver, as will also require GPUN to present data to support the viability of desulfkrization because the staff is apprehensive about the corrosion aspect of desulfkrization. To resolve our concerns. EPtal is condecting tests of tukee removed from the steen generators to detensine the necessity and viability for desulfurization.
GPUN has retained NUS to coordinate these efforts.
The studies to date by both EftNI and the staff have been focused on the steam generator repair technignes hosesse that effset is on the critical path. A meeting is testatively scheduled for August 19, 1982 for GPUN to present their final plane for the steen generator repair efforts. Assuming GPWs steen generator 1r plans en acceptable to us, repairs will start about the first of
. Once steen generator repairs are lattiated.
GPUN will update es es their progma fpr descifurizstion.
We have fbruerded sour letter and attachments to GPUN fbr consideration in their desulfkrization progree. Following the steam generator repsir meeting with GPUN on August 19, 1982, as will have a meeting with our consultants to review the details of the GPUM pleas for restart. One of the major topics to be discussed la that meeting will be desulfkrization. We look forward to seeing you at the August 19 meeting; we will confirm the date of this meeting by phone.
I sincerely, XA Copy Has Been Seni to PDR Victor Benaroya, Chief I
4 82 i
6 05000289 Chemical Engineering Branch SE Division of Engineering cc: See next page 1
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- 5. Paullekt T. Sullivan W. Hazalton H. Conrad C. Cheng E. Murphy P. k S. Young R. Jacobs P. Grant J. Rajan L. Freak C. McCracken TMI Coasvitants W1111aa Seagraves. FRC Ashort Miloa PE John Weaka. BE C. Dodd, ORIE.
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DEGRADATION AND REPAIR TECHNICAL EVALUATION REPORT DRAFT d2 3/23/83 J
- 1. Band y, R. N ewman, R. R ober g e, C. Au e r ba c h a nd J. R. W e e k s Brookhaven Bational L.iboratory Department of Nuclear Energy Cor:rosion Science Group Uptoe, New York 11973
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i INTRODUCTION in November 1981, primary to secondary side leaks were discovered in both of the once-through ste.sm generators (OTSC) at Three Mile Island Unit 1 (TNI-f 1).
Subsequent inspections and f ailure analysis performed by the utility and t heir conomitants revealed widespread circumf erential intergranular stress corrosion cracking (SCC) en the Incemel 600 tabes in the upper portions of both j
OTSC's.
In Jamsary 1982. Brookhaves National Laboratory (ENL) was requested to participate in the NRC task force evalsating the causes of this incident and the ef f ectiveness of the remedial actions. la particular, BNL was requested to provide two independent reviewers to essist ces this task f orce. These review-ers were labindranath Randy and Roger C. Newnea, of the Departwent of Nuclear Energy (IntE) st af f.
These reviewers participated la aumerous meetings with the
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utility hth at NEC Headgearters and at the offices of the utility or their consultants. They set up a variety cf SCC test,s in the laboratory to verity
.hc susceptibility of the Incomel 600 in the metallurgical condition in which it is prosect in the TMI-l'OTSC's.
Clocaus Auerbach and Real Roberge became t,volved later, contributing both laboratory work sad theoretical evaluations our understanding of the water chemistry environment that caused the inct-to m'
dent 2a the THI-l OTSC's ; J. E. Weeks coordinated the ef f ort for ENL.
E la December 1982, BNL received the To,sical Report GPUNC-008, " As ses secnt TNI-1 Plant Saf ety f or Return to Service Af ter Steam Generator Repair."
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XA Copy Has Been Sent to PDR Vietting Scientist from Institut de Recherche d' Hydro-Quebec, Varennes, Quebec, Canada.
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1 SNL was a sked to review this document and provide a technical evaluation of the saf ety of the return to service of TMI-1, f ollowing this repair, from a potot of view of our understanding of the corrosion processes that have occurred and the remedial actions proposed by the licensee.
ENL subsequently received Topt-cal Report GFUNC-010. "Saf ety Evaluation of TML-1 teactor Coolant System Clear.-
ing," and the report of a third party review. The present document prov t ie s the technical evaluation of these three reports (1) by the EN1. team, fosch of the experimental work perf ormed at ENL b4e already been written in the f orm of technical papers f or presentation at public meetings.(2) The work described in them and la this report has been perf ormed under our tec'anical assistance program f or the Chemical Engineering Branch of the Division of g
Engineering of the Esciear Regulatory Casumission, " Operating Reactor Water j
i Chemistry and Corrosion," TIN A3380, Project 6.
DIgCUS$105 All of the evidesce provided in the CPURC reports and our own laboratory investigations confirm that the intergranular SCC occurred on heavily sensi-timed Inconel 600 at temperatures below 100*C due to the presence in TMI-l coolant of one or more low-oxidation state sulf ur species and oxygen. The sul-
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f ur species in the coolant are believed to have originated f rom leakage in t o the primary coolant of sodium thiosulf at e from the reactor building spray sys-tem.
In Septenher 1981, bot f unctional testing was perf ormed, at whach time t he r e w a s no pr ima r y-t o-s e conda r y l e a ka g e. Following cooldown from this test-inn, sodium thiosulf ate entered the reactor coolant, possibly at levels of 4 to 5 ppe.
Additional thiosulf ate may have resulted f rom injections of the borated b
4 wat er storage tank (BVST) contents during ecoldown f rom this hot functional k
testing, since the water in the BWST had been previously sized with water fro the reactor building spray piping. The reactor coolant sys t em wa s v ec t ed t o the atmosphere through a co. trol rod drive mechanism (CRDM) vent in October s
1981, and oxygen ent ered t he primary side of the OTSC's at the het lee or ucrer
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Thiosulfate Crsckinz of Seceitized_ Stainless Steel and Inconel I
Intergranular attack (ICA) and totergranular SCC cf sensitized Inconel 600 by concentrated polythionic acid solutions has been kncvn f or many years.(3 )
Thiosulfate solutions, such as were present in the building spray syste:a tanks at TMI-1, can undergo a variety of oxidation and/or disproportionation reac-tions during long storage to f orm polythionates and other intermediate sulf ur species.
In the sometr of 1979, inservice inaPections shoved a significant I
nimsber of def ects is the best-ef f ected zones of st ainless steel piping at i
n1-1, especially where these lines were stagnant, had access to the air, and l
were filled with bocic acid solutions.
In 1979, the U.S. Nuclear Regulatory causaission put out I&E Bulletia 79-17, " Pipe Cracks in Stagnated Borated Vater Systems at PWR Flants.*(4) In reviewing the data in this bulletin, it be came evident that tha f rogmency of occurrence of this phencoenon was greatest in t
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those units that had thiosulfate in their building spray systems, eapecially 1
TNI-1 and ANO-1.
Ia October 1979, Erl. transmit ted t his cosciusion and prelim-imary recommeedations to the *tC regarding control of the v,e of thiosulf ate solstices in FWE's.(5)
Portions of the TMI-1 speet fuel p<rel piping containing a throuthwall stress corrosion crack were received at EKL is the f all of 1979, and a fmilure analysis performed,(6) wkich showed evidence of sulf ur contamination on the cracked estrfaces. heder a research pecgram f or the Department of Energy, l
" Mechanisms of Interg'rsamlar Sgress Corrosion Crackicg," H. S. Isaace,
- 5. Vya s,
and M. W. Eeedig began Lwestigst.ing the sensitivity of sensitized stainless steels to SCC at enhLent temperature by thiosulf at e solutions. Their first ob-servaties reported in 1979 at am E71I smainer and at the NACE Conference in 1980 (3) clearly skwed that thiosulf at e solutions with sulf ur concentrations less than 1 ppe were sufficient to cause intergranular SCC of sensitized stain-less steel. These results were transmit ted t o tb t NRC in the spring of 1980 t s preliminary work, the NRC with a verbal recoasreada tion that, based a
+t seriously consider recommending that
,J ihi olfate solations be removed f ro:t FV1 containment sprays. NUR EC46 91. h ) recom.*nded on page 2-4 9 t ha t c o n t a rr -
instion of the external and internal surf aces of pipsrg by caustic, chlertu er thiosulfate ions be carefully controlled.
3
In the OTSG design, the Inconel 600 tubes are present in the steam gen-erator vessel when the vessel itself is given a post-meeld heat treatment at approximately 621*C for 18 hours2.083333e-4 days <br />0.005 hours <br />2.97619e-5 weeks <br />6.849e-6 months <br />. This situation autor.atically produces a sensitised condition in the Inconel tubing.
I'M c n, ot SCC of, the sensitized Incosel tubing by the thiosulf ate-contaminated boric acid primary coolant in t5e presence of oxyses is theref ore a likely cause of the situation that de-veloped at TMI-1 in the steens generators in the f all of 1984.
l Exnerimental Work at
^ _Episted to the Mechanism of TMI-l Steam Generator Teilures l
Gives the strong suspicion that the thiosulfate was capable of causing SCC l
of sensitised Income!'in a usener similar to its effect on sensitised stainless l
steel se noted above, SCC tests were perf ormed to determine the eff ects of thiosulfate or othed 'envirosuseats containing reduced f orms of sulfur. The re-selts have been writtaa up is detail is other reports by the EEL reviewers.(2) w From these, we concluded that the TEI steen generator tube f silures were due to contaoimation of theihimary emelaat by sodissa thiosulfate, or some other metastableionsuchY$tetrathiomateformedbyoxidatica,duringcoldshutdown, of a sulfide scale f during power operaties. These experiments demon-strated f or the first time that very low levels of sulfur compounds in borated l
water could cause 9dC is sensitised Inconal 600 at ambient temperatures. The l
objective of these tests was to assess the influence of a variety of metal-1ersical and environmental factors on the initiation and growth of the cracks.
The results have clarified the differences between various metastable sulfur I
compounds, the behavier of the alloy at diff eraet degrees of sensttization, and the mechanism of SCC inhibition by lithium hydroxide. Sensitizad Inconel 600 l
behaves very similarly to sensitised Type 304 stainless steel in sulfur environments.(9,10)
The results of tF's investigation are summarized:
1 (i) Using the best available inf ormation on the water chemistry pre-vailing at the time of the cracking, SCC of severely sensitized material was reproduced in the laboratory at temperatures from l
l 4
l 22 ts 95'C, and at rates varying from 0.1 to 2.5 cm/ day.
Dissolved oxygen is required at these t emperatures.
(ii) Mill-annealed or thermally stabilized material is immune to low I
temperature SCC by sulfur esspounds, t'
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(iii)
In the absence of lithium hydroxide additions, the threshold sulfur
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9 concentration f or SCC (as Na2S203 added to aerated 1.3% boric
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acid at 40*C) is less than 75 ppb.
l l
I (iv) Initiation of SCC is of ten slow under static loading, but a brief period of dynamic straining is sufficient to initiate cracks which then require low stresses f or propagation. Initiation under static load is particularly difficult in marginally sensitised material, which is therefore not suitable f or tests aimed at generating con-servative water chemistry criteria.
J (v) Sodiwa tetrathionate is much more effective than sodium thiosulf ate in the initiatien stage of SCC, especially on marginally sensitized I
mat erial. However, very little diff erence was noted between the sulfur compounds os their ef f ects on crack growth under static or j
dynamic loading.
li d
(vi) Lithium hydroxide additions inhibit SCC; s. s general guide, one j
i can rely upon maintaining a critical ratio of Li to S conce..tra-tions of greater than 10/1, expressed in ppa. This is thought to be related to the necessity for concentration of the thiosulf ate ion in the cracks by electromigration; lithium hydroxide inhibits ji SCC by partial r.cutralization of the boric acid and f ormation of the competing anion, HB 0.
47 l
(vii) Under certain conditions of long exposure, dilute solutions of the metastable sulfur compounds can cause pitting or ICA of sensitized Inconel 600 without applied stress.
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These results show that slight dif f erences in environment, SCC test method or material heat treatment can give quite dif f erent result s, and have empha-sized the value of studying environmental influences on crack growth by alter-ing the environment during the test.
Rational inhibitory measures can be devised by manipuisting ion transport in the sracks, without necessarily making massive alterations to the water chemistry.
Based 'on these results, we believe that the removal of oxygen f rom the system, the sulfur from solution, and increasing the lithium concentration should reduce the risk of future SCC of Incomel in this unit.
genovel of Abeorbed s lfur from the Surface Films on the Inconel Tubian u
The licensee's reported f ailure analyses have shows that the tubing re-moved frou TMI-I has significant quantities of swifur absorbed la or absorbed on the surface oxide films, and the question has been raised whether or not these resideal amousta of sulfur could become activated at some future time and cause a renewal er a recurresce of the phenomeson. From our research, it is apparent that, due to the relatively low stress intensity required to propagate a crack in the presence of thieselfate ions and the extremely high crack propa-sation rates measured la our laboratory, any cracking that is going to occur would have occurred already. The utility has described in GFUNC-006 and 010 a l
technique they propose to use to remove the residust sulfur from the surf ace falas on the Incesel tubing. The technique involves oxidation of the inter-l mediate sulfur species to sulfate, using an alkaline solution of hydrogen l
Peroxide. It is reported that dilute solutions of sulf ate do not promote significant SCC of the matcials in question in the absence of a concentratinir mechanism. In an attempt to confirm this s*.tement, an exploratory test was performed at BEL La which a U-bend specimen of sensitized Inconel 600 was immersed in a borated solution obtained by (a) beating about 10 ppa thiosulfate with excess hydrogen peroxide at 60*C and pH 10 for one hour, (b) destroying the remaining hydrogen peroxide, and (c) bringing the pH down to 5 (the natural pH of boric acid solutions). No significant SCC was observed in this sulfate-containing medium af ter a 42-day exposure, in cont art with a parallel test in which a similar specimen was exposed to 10 ppa taiosulf ate at pH 5, witbcut 6
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I bydrogen peroxide tr e a tm en t.
In addition, experiscots are in progress at BNL the course and rate of the reaction between thiosulfste and hydrogen on peroxide in an alkaline medium prepared by appropriate neutralization of simulated primary coolant. Ion chrosnatography and colorimetry are used as the analytical t echniques f or thiosulf ate and hydrogen peroxide, respectively.
Add i t i ona l t e s t s w il l be pe r f ormed a t BNL to determine the susceptibility of seesitised Incocel tubing to SCC during the sulfur removal procedure.
Salsace of Fisst Gives the informaties described above about the sensitivity of sensitized stainless steel to SCC la the presence of oxyges and small assounts of sodium thiosulfate in solstices, any sessitized stainless steel components that saw the same primary coelart enviroceest (that is, thiosulfate and high exygen levels) would be likely to have wedergone SCC.) mat from residual stresses f rom welding, for example. The licensee has described as inspection systen given to the balance of the plant components.(12) Fress the TN1-1 FSA1, Section 4.2.2, (13) the reactor coelast piping is described as being carbon steel piping with a weld overlay cladding of stainless steel on the primary slee. This materia !
l would not be likely to be susceptible to SCC. However, the piping safe ends are designed so that there will act be any furnace sensitized stainless steel in the pressure boundary material. This is described as being accomplished either by installing stainless steel safe ends af ter stress relief or by using l
l Inconel.
If Inconel asfe ends are present, they would have been sensitized j
j during the post-weld heat treatment of the reactar vessel, and are therefore likely to have been suscsytible to the same SCC pbesonenen that occurred on the I
steam generator tabing. The FgAR also describes smaller piping, including t be l
i pressuriser surge and spray times, as betas f abricated f rom auste'itic stain-less steel. Again, any of this piping, where it is welded, would have residual stresses and residual sensitisation f rom welding and couid have suffered inter-granular SCC.
The licensee's topical reports describe in spections made on the balance of plant to look for instanc.ss of SCC.
However, it is not clest t ha t the specific i t ems sectioned a bove, that is, Incouel safe ends or welded L
austenitic stainless steel auxiliary piptag, have been thoroughly inspected.
The licensee describes no evidence of SCC throughout the plant other than that which occurred in the steam generator.
Why Did SCC Occur Oniv st the Upper Ends of the Steam Generatc - Tubes?
i The licensee has described the predominance of this cracking occurring in
[
the upper end of the steam generators as a result of the very high levels of oxygen at this point. It is quite possible from our own calculations that if the water is truly stagnant, oxidation of the amount of sulfur that is present in the surf ace filme could in fact have removed oxygen f rom the stagnant water in the tubes, so that indeed high oxygen levels were present only at the upper end of the OTSC's, where oxygen could difface into the liquid from the gas
)
1 phase in a reasonable length of time, possibly coupled with some movement of the waterline. This hypothesis, however, remains to be demonstrated, as the CPU topical report does not give data or sa analysis of oxygen levels through-out the plaat during the period from September through November 1981. Follow-ing the redecing conditions during operation (and the hot f unctional tasting),
the sulfur la the fils is likely to have been la a state highly active towards oxygen (i.e., selfide, polyesifide, etc.), as indicated by the I-ray phote-electros, spectroscopy (IPS) analysis of CPU's consultants.(14) In order to remove 6 ppe 02 from a tube 3/4" i.d., approximately 10-7 mole of sulfide Per ce2 most he oxidised to sulfate.
This amount is equivalent to a NiS film l
spyroximately 10 se thick, or 20% of as Rio film 1 m thick which contains 5%
EiS. Some oxygen gett0 ring can also be expected from corrosion processes or oxidation of metal ions in highly reduced surf ace films, e.g., Fe2+
Fe3+;
also fece reactions with residual hydraaine, and from reactions involving free radicals predsced by the radiation fis1d.
EVA1.UATION The repairs to the steam generators proposed by ihe licensee consist of i
both mechanical and chemical modifications. Both of these appear acceptable, as discussed below, 8
~
Mechanical Modifications The mechanical modifications are tube expansions to produce a minimum of six inches of fully expanded tube below the lowest known serious defect, or else expansion and removal f ree service of the tubes where def ects are known to i
exist below the upper tube sheet surface. The plugged tubes will be stabilized to prevent excessive motion of these tubes, should the def ect s propagate f ollowing return to service by scue mechanism to the point that the tube would break. The criteria established by the licensee f or these repairs appear i
prudect, and we reecamend their acceptance by the HC.
Because crack l
propagation rates are anticipated to have been high during the period between Sep*. ember and Bovember 1981 whom a corrosive environment existed in the TMI-l stern generator, we believe that most stress corrosion cracks that would have l
propagated through-wall have alrisady done so.
Based upon considerations from i
eer prvious review of the concept of a leak limiting sleeve f or use in l
vestinghouse steen generators (15), we concur that the criterion of a six inch minians expansion below the lowest known def ect on each tube is acceptable to i
ensure leak tightness should the defects propagate through-wall following retars to service.
l l
Chemic4LRemedits i
The licenses has stready removed most of the residual sulfur f rom the l
rrimary coolmat and has taken steps to increase the lithium ion concentration.
1 Both of these actioes should minimize any f urther damage by the same stress l
corrosion mechanism. Controls are spelled out by the utility which should l
either prevent or greatly rsdaca any subsequent intrusion of sulf ur compeunds.
l
.sto the primary coolant at TM1-1.
The sodium thiosulfate tank has been Jrained.
l l
Considerable sulfur does remain in the surf ace oxides at the present time, however, and it is not clear whether or not this su l f ur ha s the poten tial to cause subsquent SCC of the incocel tubicg during operation et the units.
Although sulfur compounds have probably been present in the W.1-1 steam 1
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generators throughout the operation of the plant, it teck the cnobination cf 1
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I thiosu.f ate or other low oidatioa state f orms of sulfur ions in solution at lov teoperature, plus a low p3 (low lithium), plus a high oxygen environment to cause the cracking that occurred. Leaving the reside.a1 sulfur in the oxide films is not likely to cause subsequent SCC, except in the event t ha t this consbination of circunstances recurs. The remedial procedure proposed by the licensee for removal of this residual sulfur should therefore be examined very carefully, weighing its effectiveness against possible saf ety problems. Based on the evidence available to us, we conclude that the procedure does not pose a safety issue. A smaker of remaining questions regardias the ef f ectiveness are currently being addressed by the licensee, and BKL remains prepared to perf orm ceafirmatory testa of any aspects of the cleasias procedure which may he maeful.
~
The licensee describes the attack as having occurred at the upper eos of the OTSG's becassa, during the coeldose. ' sir was admitted to the appar ple ion sad there was sa a'ltasaste wetting and drycet ocearring is the upper end of the Ek11e we comeur that the high oxygen is the myper end steen seeerster tubes..
of the steam generator tabes use probably reopensible fer the predominance of the stress corrosias~ esserries la this ares, the stility has not provided a l
detailed analysis, of'the amygda levels is the coolant la the balance of the
't i
system, including a lese,r. part of the steemi generster where stattar sensiti-nation and stress levels ocese er la 'varlses stataless steel components in the s
restoftheprimarycireAit. De de met necessarily agree that_the alternate wetting and drying wsa sa essenttal cause of the SCC phenceensg from our teets, gives as oxidising potential and.the known concentrations of sulfur and boron in the coolant, SCC of the type observed sould readily have occurred in absence of any dryout sones. We suggest that, in the stasaast balance of the system, there may have been sufficient sulfur or other reduced species present in ene surf ace films to react with and reeme the residual oxygen in the water.
By one such calculation, it voeld only have required rencval of the sulfur f rom approximately 2000 angstross of surf ace films, given the known concentration of sulfur in these films, to react with the oxygen in the steam generator tube itself. A similar argument may also apply f or other stainless steel portions of the systems. We believe the applicant should have provided a more detailed I
analysis of the oxygen levels in the primary coolant throut out the system h
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J during this period of time, and that this analysis should have been included ic his selection of balauce of plant e.aterials for inspection for their continued integrit y en return to serv '.ce.
Likelihood of Cree'.< int Recurrint Given the chemical changes proposed by the licensee, and assuming these are rigidly followed, there will be little opportunity f or continued degradation of the steen generator tubes by the same mechanism. The proposed changes in the primary coolant technical specifications are theref ore in our opinion satisfactory.
Freedom free Strese Corrosion is the Salance of the Plant The licensee's report describing their inspections of the balance of the plast yields relatively little information os inspections of weld sensitized stainless steels that might be expected to have sufficiently high residual stresses f ree welding to be susceptible to thiosulfate attack. The one or two composents la this category that were inspected (12) appeared to show minor indications that were difficult to interpret. The licensee placed considerable emphasis os emaalaing Incomel 1-750 aprings because of their high applied stress, wheresa Type 304 stainless steel in the weld-sensitized condition is l
more susceptible to SCC, even at lower stresses. Further, the chemical environment to which these pipes might have been exposed during the period that l
there were significant known sulf ur levels in the primary coolant, especially j
the level of oxygen that vow 1d have been present in these areas, needs to be caref ully assessed. Bowever, thiosulf ate cracting of sensitised stainless steel, once initiated, progresses very rapidly at temperatures below 100'C, so l
that, in the absence of any through-vs11 leaks, the likelihood of significant deterioration of this material existing without being known is small. We believe the utility should better document the inspection of any eenottized stainless steel components, especially weld-sensitized mat eris t with high residual welding stresses, and the sensitized Inconel safe ends.
I1
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CONCLUSIONS From our evaluation of the tct ormation,,rovided by the licensee and t rom the results of our own bench tests as well as those of the other consultants to this program, we have reached the f ollowing conclusions regarding the return of TMI-1 to service following steam generator repair:
1.
The intergranular SCC that occurred in the upper end of the OTSG tubes was due to a combination of high oxygen levels in this portion of the stess generator coolant and the presence in solution of one or more icv oxidation state sulfur ;ompounds.
l 2.
The los oxidation statt-sulfur compounds were probably sodium tniosulf ate or its decomposition products.
I l
3.
Evidence available to date suggesta that the chemir.a1 treatment proposed I
by the licessee does not pose a safety issue. Indications at this time are that implementation of this treatment, combined with maintenance of minimal sulfur levels and increased lithium concentrations in the primary coolant, should prevent recurrence of the phenomenon during future operation of the plant.
l 4.
The water chemistry controls to be placed on the primary cociant 1
following return to service are satisf actory.
5.
The mechanical tube expension and the plugging and stabilitation criteria proposed by the licensee are satisf actory, and the likelihood of f urther degradation or leakage occurring as a result of these actions is small.
6.
Given the high SCC rates of sensitized stainlese steel in oxygen containing thiosulf ate environment s, it would appear that any sensit ited stainless stel component in the reactor coolant pressure boundary tha t experienced the same environment as did the upper en? of the steam genersters would have already undergone SCC and have leaked.
1:
I -.
7.
A reinspection of selected areas of the primary coolant pressure boundary includin. at ras generator tubes and any Inconel saf e ends should be made af ter approximately six months f ull power operation f ollowing return to service. to
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confirm that the degradation processes base not continued. This inspection should include all steam generator tubes containing less than 40 through-vall l
defects which were not previonaly plugged.
REFERENCES 1.
a)
T. M. Moran, "Assessnest of TMI-1 Plant Saf ety f or Return to Service af ter Steam Generator Repair," CPURC Topical Report 008, Rev.1,12/7/82; b)
M. J. Graham and W. Groessway, " Safety Evaluation of TMI-1 Reactor Coolant System Cleaning," CPURC Topical Report 010, Rev. O, 3/3/83; c) Report of Third Party Review of TMI-1 Stamm Generator Repair, 2/18/83.
2.
See Appeo61x A.
l l
3.
C. E. Samana, Cerrneios. R 256(t), 1963.
4.
U.S. Inc I&E Bulletin 79-17, " Pipe Crocks in Stagnated Borated vater Systems at FWR Flaats," Rev. 1,10/29/79.
5.
J. R. Weeks, Letter to E. F. Conrad (CMES-511) 10/30/79.
6.
C. J. Caajkowski, "Interstamalar SCC of Type 304 SS in the Spent Fuel Pool Piping of TMI-1," EELh28879, Octokr 1980.
7.
E. 8. Isaacs, 5. Tyss, and M. W. Kendig, "rbe Stress corrosion cracking of Sensitised Stainless Steel in Thiossifate solutions," BNL-28816,1980.
8.
MUEEG-0691 "Investigatioe and Ev&1mation of Cracking Incidents in Piping in Pressurized Water Reactors," May 1990.
9.
R. C. Newman, E. Sitradski, and E. S. Isaacs, Metall. Trans. 13A 2015 (1982).
10.
K. Sieradski, H. S. Isaacs, and R. C. Newman, " Ambient Temperature 3CC of Sensitised Stainleep Steels, CORROSION 82, Preprint 224, 11.
R. C. N ewman and 1. Bandy, "Rankin g o f Env i ro nmen t s i n S t r e s s Cor ro s i o n Cracking," CORROSION 83, Preprint 9.
'43, "Reac t or Coola nt 12.
N. C. Essanas, CPUNC Technical Data Report Inspections and Requalifications" (with appendicesi June 1982.
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- ,. s iiEFf RENCES (Cont
- d )
13.
Final Safety Analysis Report. T'ree Mile Is la nd, trendment l'
'l.'-;'
pages 4-12 and Tables
- -6 and 4 '.
14 Fical Report on Failure Analysis of Inconel 500 Tubes : rom OTSG A sud E of TNI-1, &at t elle-Co lumbus 1.abora t or ie s, bi 30/ 8:.
l 15.
J. 1. Week s, "Re tu rn t o Se rv i c e o f t he Sa n Ono f r e l'a it i St es: Genera: ors Following the Tube Sleeving Program," Lette r Report to S. S. Pawltcki o:
U.S.
NRC, 3/27/61.
l 6
i I
(
l l
l'A p:
A P P EN DII A spers bv BN1. staff or i g i na t t o g frcs labora cry investi,attens su;mor t ed (at
_?
cast pa r t ia lly ) by this project.
- ifd%
R. Bandy,R. Roberge, and R. C. Newman, "L ov T.spersture trene Corroster C
Cracking of Sensittmed inconel 600 in Tetrathionate and Thtosulfate c;r',
3)@
Solutions, Corroston, in press.
4 i
k $u u.
- 1. Sa n d y, R. Roberge, ard R. C. Newman, "1. ow Temperature Stress Co r ro s to n
..?a-Cracking of Inconel 600 under Two Dif f er ent Conditions of senetttration,"
%W
- s-bN e
C or ro s ion Science, in press, t W.
t
':s R. C. N ewma n and 1. Eandy, " Ranking o f Envi ro nmen t s in Stress Corrosion Cr acking," NACE-83 preprint s 49.
E; g[*-;j R. C. Nevaan,
- 1. Roberge, and R.
Esady, "Eny t ro nssen t a l Va r ia b l e s in the Low l
j Temperature Stresa Corrosion Cracking of Inconel 600, COEROSION, in press.
i
'I t
R.
C. Nevaan, E. Bandy, and E. Roberge, "Mec han i s aa of TMI-I Steas
- [
Generator Failures," abstract submitted to A35-RACE-AIME International Conf erence on Envirossmental begradation of teactor Nterials, Myrtle Beach, i
4 SC, August 1983.
1 1
E. C. Nevaan, R. Roberge, and R. Sand y in, "Env i ro nme n t -Sen s i t iv e Fracture,
.E
]5h:
j Evaluation and Comparison of Test Methods," ASTM-STP, in press.
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1149 Regency Dr.
3 Columbus, Ohio 43220 August 30, 1982 Mr, Victor Benaraya, Chie f Chemical Engineering Branch Olvision of Engineering United States Nuclear Reglatory Comission Washington, D.C.
20555
Subject:
Review of 8 & W Document No. 77-1135317. " Evaluation of Tube Samples from TMI-1."
Dear Mr. Benaroya,
I have now had an opportunity to review the recent report from B & W referred to above. My review and comuments are given below, in general, the report describes a thorough and comprehensive evaluation of inconel-600 tubes removed from the TM!-1 steam generators subsequent to detection of extensive primary-to-secondary leaks in September 1981. However, there are a number of features of the report that deserve comument, particularly with regard to findings which may have implications for future activities by GPU and B 8 W in repairing the damaged steam generators. The more important of these are as to11eus:
Page 11 - Several references have been made to " greenish" and " greenish-yellow" deposits in areas which gave eddy current indications. However, no positive identification of this deposit has been made. Compounds having this characteristic color include copper oxyhydroxy chlorides, nickel hydroxide, and various sulfur compounds such as elemental sulfur, iron disulfide (Fe52, pyrite), and possibly sone nickel sulfides (as indicated in the 5 & W report).
Although electron diffraction studies were performed in an effort to identify some of the deposits observed, these efforts were only partly successful.
I believe that efforts should continue to identify the deposits, because. positive identification may provide unequivocal evidence for any given failure mechanism.
Page 26 - The report states the 26-3/4" location did not.show any signi ficar.t sulfur peak, and that other spectra, not recorded, also did not show the cresence of sul fur. However, it is difficult to sue ~' this I
,?.teer* from tha spectrum ecwn ir "i.
'.'.C.
t u -
'teJe oackground signal in the region ar.eet,ultur is c.
accear, to me that tulfur species could very well be pre.ert, in which case there is nt *hing unique about these particule enes.
Page 35 - The authors have made artensive use of the sodium azide test for k
sul fur species.
However, i t s hould be c~rh is i;ed tha t, II *.*r,ueln l }
the nan 1 test detects " reduced" for% of.ulfur, it i s no t wr,
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E w. W speci fic as to the for'n of the sul fur-containing species.
From a chemistry viewpoint, the most important Characteristic of the
" reduced" forins of sul fur is that they contain elecental sul fur.
R
.hich can act as a powerful oxidant, particularly when deposited bf';
at the tip of a stress corrosion crack.
In my opinion, a better method would have been to extract the zero-valent sulfur from the surface using cyclohexane followed by UV absorption spectrometry L.
to determine the concentration of sul fur.
I believe that this F,
technique, which can also be applied to bulk water samples, would provide more reliable measures of the local concentrations of
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aggressive sul fur.
m.
Section 2.8.2 - The Auger depth profile data contained within this section i
are difficult to understand on a quantitative basis, since the data indicate that the films (and possibly the alloy after For example, in sufficient s uttering) contain up to 10% carbon. I of sputtering Fig. 2.8.10 f.he oxygen signal is lost after sl400 indicating that the surface oxide fila is completely removed at this point. However, the carbon content remains coastant from 400A onwards at about 91. Even taking tato account hydrocarbon contamin-ation, and the fact that Ar+ sputtering could result in " scrambling" of the underlying atomic layers, this figure appears to be far too high when coepared to the bulE alloy carbon concentration of 0.0411 The alogoriths used for computing elamental composition was not described in detail, and hence it is not possible to comment on the viability of the particular method used. The data do, however, demonstrate the very serious problems that can arise when using Auger Spectroscopy for quantitative or seal-quantitative surface analysis.
t l
Similar en-*nts may be levelled against the ESCA (or IPS) data, i.e., it is frequently difficult to give an unambiguous interpreta-2 tion of the data without independent chemical evidence. Thus, on O
l page 55 it is stated that the hydrocarbon is doubly and singly bonded to oxygen, presumeably as katone (R C=0), aldehyde (RCH0),
2 or acid (RCOOH) groups and alcohol (ROH) functions, respectively.
The authors also state that carbon-nitrogen bonds were detected; presumeably these indicate the existence of primary (RMH )*
2 secondary (RR'NH), or tertiary (RR'R*N) amines or asides (including substituted asides of the type RCOMR'R").
It was stated at a meeting of the Task Group at GPU that the primary circuit may have 1
l been contaminated with ar. oil of some type, i f so, the oil may
(
orovide an explanation for the ESC A observation, but this has nos l
5een demonstrated by the authors.
It is also clalp !
't' araa, and eac*ated afsevkar** in the raw t'
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+
- r sul fur wk ara issoc,s'ed with ~'
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ev nience that a sul fur (+7) Weies of this type entsts
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conilitions which are relevant to IMI-1
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'e 5 5 - T he 51 **s res u l ts wh i c h show tr it significant a rno u n t s o f % 'rogen ice l
present i n the alloy, part 'c u' irl y in the -egion o f the c r ick tip, (fj j c a r r (. ' rat
- m 3re very i n t e re; t i n.;.
The a,, vs have ?een ser y
- a 1901<
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t * *. u-5 tu, %c h si c ic - o
Nsc * - : ' r r, ta
- b a
'ti 'g*"
t o,
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'h, !r,i qe n ec t. i'tI
- b*P e
pp.o ri "as ber-c-
- v N ever, 6
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. 4g (4
' i that partially reduced sulfur species act to poison the hydrogen recombination reaction which occurs at the metal surface during free corrosion. *.krby accelerating. penetration of hydrogen into the bulk alloy phase. It is emphasized that this is an area of great controversy in corrosion science (SCC vs HE). so that it would be premature to attach too much significance to this single observation, p
f Both the ESCA (page 55) and the electron diffraction (page 57) studies p
I inetcate that metal sulfides (e.g. Fe5 and
- igSq *?) am present d
on the entai surface to additten te various sa
,.g., me, r.3o4.
3 "F80.7N 0.300N*,
Rio,g W ).
It'should be recalled that i7 ynamic s et wd eariter fadicated that the product 1
thtosulfate)
)
~%g of sulfur * (e.g.[or other tron of the reactice between res.
and N1-Cr-Fe alleys, such as' le(
~
umuld be Fe5 selftdes) and p6estblw elche [ sell'fenc.
,1etter has not been t
detected,al.
evidnee.s3 siter
.etmed ~sulfsde re.N1 a.
It uns alse.
tapF ~ ter
,this consettant that eaM are
'.weeld - '
d$
lia temeeus solutten upon active sol jisset metal selftdes have accord 1 y,
(thi(JA1gnificant tiesogly;of' thet keen en
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k.1, *Jh11 species any W ebi A r there w e.iainie idize
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credence to the tes by the-
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,.3 21heesteeswe*sebil
h kemirskrtedby8&ilclearlyshow 4 seesttland.alcros aja spite'ef the. fact that the bulk carbon j
concentrattee;fs.get les
.laceael-400, particularly for that of the vintage ~ esed. leMf Tnie 'faictlthat Incenel-600 is much more susceptible te'~carbids.fedeced sensittaatfee that is Type.10453 for egs1 valent carbee. concentrations.can'be attributed to the much lower
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i carbon solubility in the former compared with the latter at the same temperature. Indeed. as a point for future consideration, sansiti-ration-immune low' carbon gr.ades of Inconel-600 aw not ! e F.ticM in the sense that the low carbon grades of austenitic stainless steels are ( e.g.. Type 3041.).
Page 77 - Some effort was invested in this study to determine whether or not slow crack growth would occur in the tubes under static, axial, j
tensile loading. The environments to which the inside surfaces of a
the tube were exposed included laboratory air, moist laboritory air, E
iid primary coolant. Apparently no.ittempt was made to %tarmire 1
},y j 4- -
whether or not crock extension would occur if the inside surfaces were exposed to thiosulfate (or polythlonic acid)-contaelnated environments prepared either a Jsi the addition of the contaminant to the cooleet, or stu the oxidation of metal sulfides on the estal surface.
esta sulfides could easily
/ f-have been props,ed by prior espessfe of the tube to thioswifate gj_
solutions la the. absence of saygge. T belteve that this would have g(p been a croclel emperleest, sface it any.have f adicated whether or not the fears of skbsequest ciechteg ta' fW primary systans which l
have not been d,es,s.1forland-are sell-Segaded.
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,,.,3 At this potat. I wish to reiterate that the W 8 5 study represents a thorough and comprehensive analysis of. the faHe415-1 SS tubes. particularly in view E
of the very severe ti
~ tretatt sinder
ch hors had to 6perate.
1 the '
- Isotter of the 1RI fallures Momever, I heltese.
1s, M;yssek has not been addressed:'.
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ss' tete of tt.faselfate sad at11 the fatieres coatt
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'b; DISTRI ION File RVollmer PCheck DEisenhut DCT 0 51N2 JRoe HThompsom Stinogue SSnyder DeVoung 5Hanauer Cunningham EDO H320 ECase VSenaraya teenton CMcCracken PPAS K. Johnson L. Miller Ms. Jane Lee M. Bridgers EDO-12320 183 Valley Road E. Abbott, OCM Etters, Pennsylvania 17319 Q.. &
Dear Ms. Lae:
i Year letter of September.1,1982, to Cassissionar Gilinsty has been i
referred ta'ide for
. Yes raised five sguestions pertaining to the corrosion,pretees.
D e M -1 stage rs. All of the are betea aued by the staff as part de..td ap' penfa;1E f restart for TNI-L cancerns reised te per; un et ear.
unti N>.4 x. n:. '
,I..J
. $ te cesjgleted k.ing: W. 1983.
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9st a pt n habelpet.
eer fell.evaluaties of'the corrosien prob 1 W st' this ties fylly respond to each of
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your lent, p' re11e1
' data.are available le r of your concerns.
q. :cr;ylation to~
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testleniiItO' h.1 "
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' et tens relate to once through The'eski tiration and GFtE's determination stees
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thek.-
- ss4 la caus4tive We teve 19'
'and believe a
celes_that sodium thiosulfate is causet cerrosion. This determination is based'em!
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'e;
~ for the sodium thiosulfate to ester the' and the presence of sodium
~
thiosulfate'fa at sofficient concentrations to have caused the'correst AdtitIonally, laboratory tests have dessestrated that the spacentration of sulfur as sodium thiosulfate, found in the reactar coolant, was sufficient to have caused the corrosion. None of the other potential sources for sulfur would appear te have provided sufficient concentrations of sulfur or the necessary reduced sulfur chemical forms to cause the observed corresion.
The word " sensitization", which you questioned, is a metallurgical term used to describe the microstructural characteristics of the OTSG t:4e natarial. 5m:ifically, for the OTSG tubes which are manufactured from INCOEL-600, sensitized microstructure refers to l
the preferential carbide precipitation along grain boundaries and the presence of lower chroalue content region, with respect to the bulk chroeluecontent,adjacenttothegrainboundariesinthetubingalloy.
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p OFFICIAL RECORD COPY
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Ms. Jane Lee 2
During the manufacturing and fabrication process, themal mechanical i
effects can lead to the precipitation of chroni m carbides and the redistribution of chroelun stans along and adjacent to the grain I
l boundaries which, in turn, change the mechanical strer.gth and the corrosion resistance of the tet By controlling the heat treatment kl 1 the shape, amount, and distribution conditions, it is possible to can of carbides along grain boundaries, and the degree of chromium depletion -
p in surrounding areas.
In this menner, it is possible to improve resistance p
s of cerrosion. Cemeersely, a material structure which E
to specific is controlled heat treatment te leprose resistance to scos specific h
types of cortes on, can be mere ihie te other types of corrosion.
When selecting a estarial for a Sc amplication, the ersin les distethdlen and grain Soundary structure, carbide arecentrolledtogreeIderesistancetothe L'i region chromium types of corresten dich are typically settelpeted under the intended l
service conditions. The sensitized t e tas used at TNI-1 was selected v
to proeide good strength and other escheefcal properties, and resis-
._t
{W:.
tance to the typical forms of correstem'that would be anticipated in a nuclear stema generster. '1te sedles thfeselfate which was introduced into the reacter coolent is met a twical corredent in nuclear steam generators. TherefeN, the:
ed set heee a Mgh degree of resistance to corresteA by a sulfur species.
N 3
M l
The repairs for 135-1 GT5G's es not include asy changes in treatment er grote hamadwy stygggggg.
{nstead, the focus teing is na renseing the corredent ans esaurlag that it cannot be reintro-duced to the reacter coolant system.
The chlorido dich uns found during eseelnation of the tubing is normally present in trace geestities in unter and is twical y found
)
I dering any corresten examination. The chieride reported in the TM1-1 l
steam generator states report, in our opinien, was not a causative agent 3
in the corrosion process.
{
l I
Question No. 2
\\
This question relates to the presence and potential effect of sodium thiosulfate on other system estarials (reector internals). A thorough L
examination of the reactor internals was conducted including removal and destructive examination of same components. These examinations were r
witnessed by MAC peasonnel and our consultants.
No evidence of sulfur-induced corrosion wee found.
Sulfur has been detected in the protective oxide layer on most systes surfaces. GPtAt is conducting an extensive program to determine if the concentrations of sulfur which have been found can cause further corrosion.
If a significant potential for future corrosion exists, the sulfur will be removed prior to restart.
The staff and our con-L sultants are following these programs closely.
i
- $NsdE ~~
-OFFICIAL RECORD COPY RD-GD,2TOPRP VE CF
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Ms. Jane Lee 3
The most probable explanation of why corrosion was found on the steam generator tubes and not other system saterials is that the tubes were under tension.
The degree of tension in the steam generator tubes was sufficient to fracture their protective oxide film and permit the sulfur to attack the base metal.
This concern will be addressed in detail in our safety evaluation.
Question No. 4 The concern you expressed in the question relates to the potential for a "Ginna Type" tube rupture due to tube pullout potential in the tubesheet and pressurized thermal shock.
The 50*F temperature difference between the tube sheet and tubing within the tubesheet is very conservative.
Under all normal plant operations this difference is only a few degrees.
For the worst case postulated accident (main steam line bicak), a maximum of approxiestely 30"F can be predicted. Therefore, testing at a 50'F temperature differential is conservative.
Additionally, GPUN will not expand the bottos two inches of tubing within the tubesheet which provides an additional physical tubing restraint in the event of further corrosion.
Pressurized thermal shock is being reviewed by the staff as Generic Issue A-49. We are currently scheduled to have A-49 resolved by late 1983.
Preliminary information indicates that the potential for significant thermal shock due to a steam generator tube rupture is small.
Questfor No. 5 This questions the suitability and reliability of the kinetic expansion ir process. An extensive amount of testing is being conducted by to qualify the proposed repair process for returning the steam generators to service.
In addition to monitoring this testing, the NRC is having independent *est19g of the repair process conducted by our contractors.
Prelisinary inforestion indicates that kinetic expansion is the best repair method. Accelerated life cycle testing of sockups l
in the laboratory has shown no problems in meeting technical speci-fications for steam generator ttbe leakage for up to a five year period.
l These tests are continuing and will provide life cycle data for a i
period of 35 years.
We appreciate your interest and wish to assure you that we are thoroughly evaluating the corrosion probles which has occurred at i
TMI-1. We will require whatever steps are necessary to protect the health and safety of the public.
5 OE:CMEB %
Harold R. Denton, Director 0
VBenarcha Office of Nuclear Reactor Regulation C.wa ; ken: ao l
9/ 38 /82 9/ p /,82 a,$/ h SW ang
O/605 (1 )
m
~_/
2 DijTRIBUTION :
g[I g,,A Entral File CMEB Reading File M4 3 1M2 n
.-7 o
MDORA40UN FDR: Hugh McVesgh. Chief Pristing and Graphics Breach Meistes of Tech Iah & Decaent Control e
?
ROM:
Victor Senareys. Chief Chemical Engineertag treach i
l Meistem of Engineerint
~:
l I
PRINTIM CGETS FW 1NI M Stun asurnaTOR TUBE 5 SUSJECT:
l l
DESTWCTIVE EINIIMTION MPORT i
i l
Your staff has tafereed as that the printlas cost for the sehject riport (which is la year posseestem) is estimated te he $700 Repredactions l
with clear dotatis of the phetedulcrographs era -am to provida tafor-antles la a timely mammer ihr the MC verteuers and the five esassitants i
de are sepperti the staff te spelgeting the IIII M steam generator M
4 to the assassity ter eesh of the revieners to have repair efeerts.
this inesematies is dotati, se ses es viable alterestive for disseminating this interusties. Messe schedsle the regredacties of this report se that i
4 copies can ha ta the sail by hapst 6.19E.
N Victor benarsys. Chief Chemical Engiacertag Branch Meistem of Entlasering I
l cc:
W. Johnston j
C. McCrocken e
- 5. Paulicki I.
T. Sullivan l
C. Posissay i
Muct:
C. McCracken 128595 I
QW C ' _.. /f &
I' 06 82Ceci ^
6 05000:~n XA Copy Has Been Sent to PDR wr b
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A SIRIgnilC1:
W ntral File CMEB' Reading File TMI-l File g
MEMORAe0W FOR: Victor Benareys. Chief Chemical Eastasering Branch
/
FeuM:
Ceared McCrackes. Sectlen Leader Chemical Tectasiegy Section
SUBJECT:
STATW5 Up0ETE FOR TRI NO. 1 STEAM GENERATOR REPAIRS Three asettags were held staes the last update was issued on August 17. 1982.
y Aspost 25. 1982 Perstypesy: Independent third party review of the repair process. 't,.
+
v
,.py,
September 1.198t. Pepsippany: Prettelsery SER review, fatigue tem progres review. preliminary states of
. ;.v.
September 2.1982. pOibt uttaess leak tests of qualifi-
~
eetten w esha,
- m 2.y.- - -
Based es discussions et thans meettags, the'serrent schedule is as follows:
ML 2 Septesher 15.1982.8$he'e:das WW presentatten to staff and FRC to jostify init.iatten.o.f ~ repairs.
Septester 17.1982: sesfr fsase repair SER.
- september 28 19et: first les of tubes in TMI no.1 oTsG's.
Feilowing tkla.espeneten eestry. ECT and other appropriate tests will he perfomed to vertfy eteeptable expensions. Assuming asseptable reesita from the first espansion, production expansion will start a few days hter.
. ecctober 13, 1982 Betheads: GPWI presentation on status of all progress affecting recovery to staff and staff consultants.
- 0ctober 14, 1982 Bethesda: Staff and staff consultants seet to discuss GPUN's recovery progress and areas of concern.
- November 1982: GPUN submits safety evaluation addressing all aspects of recovery from the OTSG corrosion probles.
- December 1962: Staff issue restart SER.
I l
i o"~ R, mgg..ggyg gyyz y y4.g...
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victor senaroya SEP 10 t%2
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Meeting Susanaries 08/25/82 :
Independent third party review (ITPR) meeting on repair process; j
the preliminary findings of the ITPR are to be issued by 9/10/82.
1 The staff will be provided with this infonmation by the Sept.15
.j meeting in Bethesda so that any ITPR concerns for the repair pro-cess can be factored into our evaluation. No concerns were raised 1
l at the meeting that would delay repair initiation.
Y cj i 09/01/82:
A.
GPUN has initiated an extensive program to:
e,
- h 1.
Develop and prove a method for desul furization.
l i
2.
Assess the risk if desulfuritation is not performed.
1 -
l It is anticipated that preliminary results from this program
(
+
l will be available fhr comment by the October 13, 1982 meeting.
8.
A program is beleg soepleted which addresses the rate of crack propagstfeef tssed en various starting crack sizes, prs 11staary ts' indicate that defects which are too es11 fte by ECT (see. Attachment 1. Trip Report by C. V. Redd, will not propagate to failure due to y
high cJsle"fati ~ '.derlag saticipated operating cycles.
il A substantial amargin exists between the ECT level O
of detestability defect siras which are predicted to l
l l
propagate, e
1 1
09/02/82: Preliminary leak rete testtag of 10 tube qualification blocks
'j !
I at Foster heeler hagt shown leakages approaching the program goals of less them li10-4 f/hr One block was found to be f
i leaking at approatmately 2 a 10-E l/hr, but the welding con-d docted on the block 4'fter assembly may have affected the expsnsion seal. At any rate, these leakage rate goals are approximately h
three orders of magattade below the plant Technical Specification d
limit of 1.0 GPM.
i General 1
Comuments by Dr. D. MsCdonald have been received pertaining to B&W's evaluation l
of tubing removed froa TMI Mo.1 ( Attachment 2).
Dr. Macdonald's coauments focus primarily on the rule of thiosulfate in the corrosion,.-ocess and the necessity for desulfurization prior to restart.
These coments will be pro-vided to GPUN and they will be requested to respond during the October 13, h_
1982 meeting.
The 100% ECT utilizing the 0.540 probe for both steam generators has revealed some defects outside of the tubesheet which are attributable to IGA.
A number of these defects have very small ECT slynals which indicate eitner that they 9
l 1
-l l
c Victor senaraya SEP 101982 are circumferential1y small or a're not far through wall. Preliminary analysis indicates that these defects are unlikely to rapidly propagate as a consequence i
of vibration.
I have discussed with GPtm the possibility of leaving a i
statistically significant number of these tubes in swvice. The advantage te leaving same of these tubes in service is that they can be monitored fregnently ensegh to provide rate information for corrosion propagation of this type of defect. The startup program will include ECT's after:
1.
Pre-critical het fhastionals, 2.
Apprestastely 30 EPPO, 3.
Apprestastely gt,addittenal EPPO.
These pertedts faspectfens will fnsestfee to usetter for initiation of new defects and with eng5' egged " ment e defects' tehes establish corrosion propagstten reta ta tsustles.
Io seest afsnifieset propagation is detected after Mtical het fusstless, the tebes ces then be removed from service. This'eessept util be disenesed la more detail with other staff morters :aedicensultests.at the Octsher 13 sostleg..
he Osteher,N moottog'will be issued if there are N"
te any afge fleest Stees to report.
t
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~
Ceared McCrackos. Section Leader Chesteal Technology Section Chenfeal Engfacertog tranch Attachments: As stated cc POR 80-209 R. 9p11eer
- 9. Itsenhut W. Jonasten T. Revak
- 8. Latmas J. Ilhtght J. Stela
- 5. Paulikki i[
T. Sullivan M. Caered W. mieiten C. Cheng E. k rphy TMI consultants P. We
- [
J. Rajan John Weets. sm-l DE -
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INTRA LABORATDRY CORRESPONDENCE OAK RIDGE NATICN AL L ABOR ATORY August 17, 1982 s
To:
R. W. ItClung From:
C. V. Dodd d. v. C M
Subject:
Travel to Harrisburg, Pennsylvania, August 8-9, 1982 On Monday, August 8, I met with General Public Utilities (GPU) and NRC personnel to discuss the eddy-current inspection of the~ Three-Mile Island Unit 1 steam generators.
A partial list of attendees is attached.
Nick Ka anas of GPU gave a presentation of the development and qualification program for the eddy-current inspection of the steam generators. A set of inside diameter calibration standards with circu=fere;.tial notch lengths of 0.060, 0.100, and 0.187 in., notch depths of 20, 40, 60, and 807., and widths of typically 0.004 to 0.005 in, were constructed.
In addition, an axial notch standard with 0.060 in. leng notches was constructed.
These standards were used to test circunf erential differential probes of 0.510 and 0.540 in., and an eight-coil array with 0.187 in. outside diameter pancake coils.
Various gain and other conditions were run.
The best combination for the differential coil system was the 0.540 in.
outside diameter probe with a permanent magnet saturating core and < gain setting of 60.
The permanent ca gnet sbould not have increased the ignal any but only reduce the noise a small amount.
I exanined a probe a d its field did not seem strong enough to saturate any ferro=agnetism asse:iated with inconel (about 0.3 T is usually needed).
However, it did seem to be core carefully =ade than the regular 0.540 in. probe.
An additional mix l
of the 200 and 400 kH: mixed signal with an 800 kHz signal reduced the l
noise due to probe chatter and pilgering.
1 The 8X1 absolute probe showed more signal to the small defects at a gain of 53, but a fairly large lift-off signal was also present.
The 8XI probe array is being revised to increase t.he probe body from 0.520 to 0.540 in, which should reduce the lif t-o,f f problem.
A correlation of the defects seen by the pancake coils with the defects seen with the 0.540 in. outside diameter differential probe showed that of 3233 defects detected by the pancake coil, 3216 were also detected by the differential probe.
This number was improved to 3229 by using the mix to reduce the inside dia=eter noise.
This shows an excellent match and also showed that the '0. 5 40 in. differential probe, operated under these conditions, can reliably detect the sa e type of circumferential crack.
In order to directly apply the results obtained from the electrodischarge cachined standards, an "eff ective axial crack vidth" fo'r these intergranular stress-corrosion cracks cust be determined.
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s R. W. ikClung Page Two August 17, 1982 On Monday afternoon, John Janiszewski of GPU gave a presentation of the results of the metallography of the cracks.
Some cracks appeared to,have regions of bulk intergranular attack associated with them, and some appeared to be very narrow with very little branching and axial component.
However, the crack would only need a few branches to effectively disrupt the flow of eddy currents.
John Janiszewski will generate an " effective axial component" by reviewing the results of the previous metallography and furnish it to us.
This number will show how applicable the calibration results from electrodischarge machined notches is for the circumferential cracks, and furnish an independent verification of the ability to detect the defects with a different probe.
The results of a dimensional analysis experiment using large scale models at CRNL will be used to correct the sensitivity at one length to the sensitivity at another.
It was stated that the region near the crack was depleted in chro=e, but no esti= ate was made of the bulk electrical and magnetic properties of the region.
A total of 19 ft of " good" tubing has been examined by metallography, with an additional 6 ft to be examined.
No defects were detected by this test that were missed by the eddy-current test.
Some of the defects detected by the eddy currents were not found by the metallographic examination, probably due to the way the samples were cut. Some of the eddy-current signals turned out to be due to manufacturing, handling, and assembly artifacts, and would not be detrimental to the service of the tube.
On esday I visited the data reduction site at the Host inn near the plam.
I reviewed the results of the scan on tube A71-126.
This tube was pulled and a section sent to ORNL for examination. A through-wall defect was detected using a high-frequency (5 IEz) scan with a small (0.020 in.
mean radius) probe from the outside.
The defect was then etched and showed a 0.005 to 0.010-in.-wide affected region on the outer surface.
It is not known if this entire region appears as a low conductivity region or not.
The defect was recorded as 80% through-wall by ConAm, and a blind remeasurement of the defect from tape showed 84%. The magnitude of the signal was 1/2 V at a gain of 34, and an 0.510 in, outside diameter differential probe was used.
I also looked at runs using thf 0.54'O in, outside diameter dif ferential probe with a gain of 60.
The practical noise level to get a reasonable measurement of the defect depth appears to be around 0.5 V, although in many cases smaller def ects can be ocasured' Based on the 0.005 in. wide standards, this falls in the range of a 0.060 in. long defect, 40%
through-wall.
Depth ceasurements on smaller defects will probably be very inaccurate.
A 100% inspection of the full length of all the tubes is being performed using the 0.540 in. probe with a gain of 60.
The number of indications is about three times as many as were observed with the 0.510 in. differential probe. Tube B10-48 showed 16 inside diameter defects, all about 1 V in amplitude, between 30 and 60% of the wall.
The lowest defect was near the third support plate.
The high sensitivity of this new inspection is also
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R. W. McClung Page Three August 17, 1982' picking up a' number of outside diameter signals from the canuf acturing process, which are not detrimental to the < service and can be ignored.
The tubes that exhibit the inside diameter signals should be rescanned with the 8X1 pancake coil array, and. the tubes with defects greater than the plugging limit plugged. The tubes with defects below the plugging limit can be reexamined at later intervals to monitor growth of this type of defect.
There appears to be a drif t and a quality assurance problem with the probec.
This problem doesn't affect the accuracy of the test, but results in frequent probe changes. The inclusion of several of these types of defects in an in-line standard (for future tests) should be considered.
The instrument gain in the field is set to give a repeatable voltage amplitude from a drilled hole flaw, rather than an absolute number.
The pancake coil array is operated at a single frequency and euch more susceptible to different types of noise than the dif ferential probe.
This array also requires cuch more equipment than the differential probe.
Zetec is workin; on a more compact system, but no esti= ate of the availability of this instrumentation was given.
The results that I saw on tbnday and Tuesday answered all the previous questions that E==ett Murphy' had submitted in his letter of April 12, 1982, except ' the one on safety evaluation.
Some attempt should be made to determine how large a defect would have to be before it would present a saf ety proble:
I feel that the defects that can now be reliably detected are =uch small.: than those that would present a hazard, but have no inf ormation tc back this up.
The study, done by the utility, their contractors, and the EPRI NDE Center to determine their seccitivi:y limits, was outstanding.
CVD:jlb cc:
R. Barley, GPU J. H. DeVan L. Frank,.NRC J. C. Griess E. J. Honan N. Kazacas, GPU A.
L. Lotts C. McCracken, NRC/
J. Muscara, NRC P. Patriarca G. M. Slaughter J. H. Smith P. Wu, x NRC, C. V. Dodd/ File t
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Columbus, Ohio 43220 August 30, 1982 Mr. Victor Benaroya, Chief Chemical Engineering' Branch Division of Engineering United States Nuclear Reglatory Commission Washington, D.C.
20555
Subject:
Re,iew of B & W Document Nc. 77-1135317
" Evaluation of Tubs Samples from TMI-1."
Dear fir. Benaroya,
I have now had an opportunity to review the recent report from B & W referred to above.
My review ar.d comments are given below.
In general, the report describes a thorough and comprehensive evuluation cf Inconel-COO tubes removed from the TMI-1 steam generaters subsequent to detection of extensive primary-to-secondary leaks in September 1981.
- However, there are a number of features of the rep, rt that deserve comment, particularly with regard to findings which may have implications for future activities by GPU and B & W.in repairing the damaged steam generators. The more important of these are as fc11ows:
~ 19e 11 - Several references have been made to " greenish" and " greenish-yell: e" deposits in areas which gave eddy current indications. However, n:
positive identification of this. deposit has been made. Compounds having this characteristic color include copper oxyhydroxy chicrides, nickel hydroxide, and various sulfur compounds such as elemental sulfur, iron disulf'de 'JeS, pyrite), and possibly some nickel j
2 sulfides (as indicated in the' E & W report).
Although electron diffraction studies were performed in an effort to identify some of the deposits observed,'these efforts were only partly successful.
'I believe that efforts should continue to identify the deposits, l
, because positive identification may provide unecuivocal evidence
'for any given failure mechanism.
Page 26 - The report states the 26-3/4" location did not show any significant sulfur peak, and that other spectra, not recorded, also did not show the presence of sulfur. However, it is difficult to support this statemer.t from the spectrum shown in fig. 2.6.6, because of the large background signal in the region where sulfur is evident.
It appears to mE that sulfur species Could very well be present, in which case there is nothirg unique about these particular cases.
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Paje 35 - The authors have made extensive. use of the sodium azide test for sulfur species. However, it should be emphasized that,although test detects " reduced" forms of rulfur, it is not very i
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From a chemistry viewpoint, the most important characteristic of the
" reduced" forms of s'ilfur is that they contain elemental sulfur, which can act as a powerful oxidant, particularly when deposited at the tip of a stress corrosion crack.
In my opinion, a better method would have been to extract the zero-valent sulfur froin the surface using cyclohexane followed by UV ' absorption spectrometry to determine the concentration of sulfur.
I believe that this technique, which can also be applied to bulk water samples, would provide more reliable measures of the local concentrations of aggressive sulfur.
Section 2.8.2 - The Auger depth profile data contained within this section are difficult to understand on a quantitative basis, since the data indicate %at the films (and possibly the alloy after For example, in sufficient sputtering) contain up to 10% carbon.1 of sputtering Fig. 2.8.10 the oxygen signal is lost after s1400 indicating that the surface oxide film is completely removed at this point.
However, the carbon content remains constant from 400X onwards at about 9%.
Even taking into account hydrocarbon contamin-ation, and the fact that Ar+ sputtering could result in " scrambling" of the underlying atomic layers, this figure appears to be far too high when compared to the bulk' alloy carbon concentration of 0.041%.
The alogorithm used for computing elemental composition was not described in detail, and hence it is not possible to comment on the viability of the particular method used. The data do, however, demonstrate the very serious problems that can arise when using Auger Spectroscopy for quantitative or semi-quantitative surface analysis.
Similar comments may be levelled against the ESCA (or XPS) data, i.e., it is frequently difficult to give an unambiguous interpreta-tion of the data without independent chemical evidence. Thus, on page 55 it'is stated that the hydrocarbon is doubly and singly bonded to oxygen, presumeably as ketone (R C=0), aldehyde (RCHO),
2 or acid (RC00H) groups and alcohol (ROH) functions, respectively.
The authors also state that carbon-nitrogen bo.ds were detected; presumeably these indicate the existence of primary (RNH ),
2 secondary (RR'NH), or tertiary (RR'R"N) amines or amides (including substituted amides of the type RCONR'R").
It was stated at a meeting of the Task Group at GPU that the primary circuit may have beer, contaminated with an oil of some type.
If so, the oil may provide an explanation for the ESCA observation, but this has not been demonstrated by the authors.
It is also claimed in this section, and repeated elsewhere in the repgrt, that minor portions of the sulfur peak are associated with "S01-" -- I cannot find any evidence that a sulfur (+2) species of this type exists under any conditions which are relevant to TMI-1.
Page 55 - The SIMs results which show that significant amounts of hydrogen are present in the alloy, particularly in the region of the crack tip, are very interesting.
The authers have been very careful not to attach toom much significance to these findings, and at no time imply that a " hydrogen embrittlement" phenomenon is involved in the failure process. However, it has been claimed by others on numerous occasions
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I that partially reduced sulfur species act to poison the hydrogen recombination reaction which occurs at the metal surface during free corrosion, therby accelerating penetration of hydrogen into the bulk alloy phase.
It is emphasized that this is an area of great controversy in corrosion science (SCC vs HE), so that it would be premature to attach too much significance to this single obs'ervation.
Both the ESCA (page 55) and the electron diffraction (page 57) studies indicate that metal sulfides (e.g. FeS and "Fe8NigS16"?) are present on the metal surface in addition to various oxides (e.g., NiO, Fe3 4, 0
Ni.6 4").
It should be recalled that "Fe0.7Ni0 00H", "Fe2 0 0 thermodyn.3amic agrumen.4ts presented earlier indicated that the product 1
of the reaction between " reduced forms of sulfur" (e.g., thiosulfate) and Ni-Cr-Fe ' alloys, such as Inconel-600, would be FeS (or other iron sulfides) and possibly nickel sulfide. The latter has not been detected, although evidence is cited for the mixed sulfide FegNiaSi6"-
It was also argued in an earlier report by this consultant that these*
active sulfides would spontaneously oxidize in aqueous solution upon exposure to oxygen. Accordingly, the fact that metal sulfides have been detected on surfaces that existed for a significant time outside of the reactor indicates that the amount of metal sulfide analyr.ed is in fact a lower limit.
Interestingly, one.of the oxidation reactions which can occur may be written in the form MS + 3/2 0
> M0 + S0 2
2 in which the sulfide anic-is converted to S02 This species may the oxide surface, thereby explaining subsequently chemisorb or o$"".Alternatively, the sulfide may oxidire the ESCA observation of *:0 as previously proposed tc form polythionic acids (H Sx0s) which 2
presumeably could also ex;1ain the ESCA results.
In short, the electrooptical analyses reported by B & W 1end credence to the i
hypothesis that polysulfur oxyanions may be regenerated by the oxidation of metal sulfides on the Incone-600 surface.
If so, the danger of cracking at a later date should be considered to be very real.
The extensive metallographic examinations reported by B & W clearly show a sensitized microstructure, in spite of the fact that the bulk carbon concentration is quite low for Inconel-600, particularly for that of l
the vintage used in TMI.
The fact that Inconel-600 is much more i
susceptible to carbide-induced sensitization that is Type 304SS for equivalent carbon concentrations can be attributed to the much lower carbon solubility in the former compared with the latter at the same temperature.
Indeed, as a point for future consideration, sensiti-zation-immune low carbon grades of Inconel-600 may not be practical i
in the sense that the low carbon grades of austenitic stainless steels are (. e.g., Type 304L).
Page 77 - Some effort was invested in this study to determine whether or not slow crack growth wculd occur in the tubes under static, axial, tensile loading. The environments to which the inside surfaces of the tube were exposed included laboratory air, moist laboratory air, and primary coolant. Apparently no attempt was made to determine
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- a whether or not crack extension would occur if the inside surfaces were exposed to thiosulfate (or polythionic acid)-contaminated environments, prepared either ex situ by the addition of the cont'aminant to the coolant, or Tn situ by the oxidation of metal
,. sulfides on the cet'l surface. The metal sulfides could easily a
have been prepared by prior exposure of the tube to thiosylfate solutions in the absence of oxygen.
I be'lieve that this would have been a crucial experiment, since it may have indicated whether or not the fears of subsequent cracking in: PWR primary systems which have not been desulfurized are well-founded.
At this point, I wish to reiterate that the B & W study represents a thorough and comprehensive analysis of the failed TMI-l SG tubes, particularly in view of the very severe time contraints under which the authors had to operate.
However, I believe that a central issue in the whole matter of the TMI failures has not been addressed: that is, what was the precise role of thiosulfate and will the failures continue to occur if the primary circuits are put back into operation without adequate desulfurization measures being taken.
I am sure that you will agree that these are very important questions indeed.
I look forwaM to your response and those of other interested parties.
Yours sincerely, ggy AC i
D.D. Macdonald DDM:ab i
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MEMORANDUM EOR:
Darrell Eisenhut, Director Division of Licensing n
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EROM:
Richard Vollmer, Director
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Division of Engineering SUBJECI:
REPAIR DE IM1-1 SIEAM GENERAIOR IUBES Q
lhe Division of Engineering and our consultants have reviewed IMl-1 steam generator repair techniques as submitted in the 1982 and updated licensees 10 CER 50.59 evaluation ot August 19,th the licensee's in the September IKl982 meeting. We agree wi detemination that repair of the steam generator can be conducted under 10 CER 50.59.
We are of the opinion that a statt safety evaluation is necessary prior to restart to detemine that the licensee has taken the proper steps to recover tres the 015G corrosion probles Richard Vollmer Director Division of Eng,neering i
cc:
R. Purple W. Johnston G. Lainas J. Knight
- v. Benaroya R. Bosnak J. Stolz W. Hazelton l
C. McCracken R. Jacobs J.Rajan L. Erank
- 1. Ippolito
- 5. Pawlicki
- 1. Sullivan l
l XA Copy Has Been Sent to PDR s
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DE: CME DE:
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D MEMORANDUM FOR:
Richard H. Vollmer, Director y
Divisten of Engineering THRU:
William V. Johnston, Assistant Director Materials & Qualifications Enginearicg Division of Engineering qk FROM:
Poul Wu Chemical Engineering Branch E
Division of Engineering
SUBJECT:
EXTDtSION OF PNL TECHNICAL ASSISTANCE TO THE DIVISION 0F ENGINEERIE
- EVALUATION OF THREE MILE ISLAND UNIT NO. 1 STEAM c w a4 TOR CORROSION" B2506 Pacific Northwest Laboratory (PNL) has provided technical assistance to us in FY 1982 regarding the evaluation of TMI-1 steam generator
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corrosion assessment and repair work. Because of the late completion of repairs by the licensee and the delay in scheduling of a hearing in which PNL is expected to particpata, PNL is requesting to extend the' period of performance for the adject project through March 31, 1983.
Because of the late submittal of the extension request (October 14,1982) by the PML, the contract extension deadline (October 15,1982) has not been met. We have emphasized again to PNL the importance of providing j
work statements and contract extension requests in a timely fashion.
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Paul Wu, Project Manager Chemical Engineering Branch 7f
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,s XA Copy Has Been Scnt to PDR g
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