ML20093A294

Forwards 840706 Quarterly Update on long-term Corrosion Test Program.Certificate of Svc Encl.Related Correspondence

ML20093A294
Person / Time
Site:	Three Mile Island
Issue date:	07/06/1984
From:	Churchill B METROPOLITAN EDISON CO., SHAW, PITTMAN, POTTS & TROWBRIDGE
To:	Hetrick D, John Lamb, Wolfe S Atomic Safety and Licensing Board Panel
References
83-491-04-OLA, 83-491-4-OLA, OLA, NUDOCS 8407100304
Download: ML20093A294 (4)

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SHAW. PITTMAN, PoTTs & TROWBRIDGE

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(202) 822-1051 HAND DELIVERED BY FEDERAL EXPRESS Sheldon J. Wolfe Dr. David L. Hetrick Administrative Judge Administrative Judge Chairman, Atomic Safety and Atomic Safety and Licensing Board Licensing Board College of Engineering U.S. Nuclear Regulatory Commission Dept. of Nuclear & Energy Engr.

Washington, D.C. 20555 The University of Arizona Tucson, Arizona 85721 BY FEDERAL EXPRESS Dr. James C. Lamb, III Administrative Judge Atomic Safety and Licensing Board 313 Woodhaven Road Chapel Hill, North Carolina 27514 In the Matter of Metropolitan Edison Company, Et Al.

(Three Mile Island Nuclear Station, Unit No. 1)

Docket No. 50-289-OLA and ASLBP 83-491-04-OLA (Steam Generator Repair)

Dear Administrative Judges:

Enclosed for your information is Licensee's July 6, 1984, quarterly update on the long term corrosion test program.

Sincerely yours, l .

8407100304 840706 O' -

PDR ADOCK 05000289 ayygi Q PDR Bruce W. C'hurchill Enclosure o^

n cc: Service List (attached) x- hV]

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l M7 GPU Nuoteer Ceeporation 100 Interpace Parkway l Persiocany.New Jersey 07054-1149 '

(201)263-6500 -

TELEA 136 4a2 Writer's Drect Dial Number:

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July 6,1984 5211 84 2172 Office of Nuclear Reactor Regulation Attn: J. F. Stolz, Chief Operating Reactor Branch No. 4 Division of Licensing U.S. Nuclear Regulatory Conunission Washington, DC 20555

Dear Mr. Stolz:

Three Mile Island Nuclear Station Unit 1 (TMI-1)

Operating License No. OPR-50 Docket No. 50-289 Long Term C0rrosion Test Program This letter provides the quarterly update on the long term corrosion test program, as well as recent results of destructive examinations of tube specimens. The operational cycling phase of the test program was completed 1 in mid May. All specimens were examined in accordance with the normal i non-destructive techniques, and destructive examinations are now in progress.

As you are aware, specimens used in the long term corrosion program are 'ctual TMI-l tubing removed from the steam generators and exposed to one of four simulated operating environment test loops. All four test loops had chlorides and fluorices at the maximum permitted concentrations (by plant chemicalspecifications). Loops two through four had sulfur (measured as sulfate) at its maximum limit, maintained by the addition of sodium sulfate. Loop one maintained sulfur (measured as sulfate) at its maximum concentration through the addition of thiosulfate (the known contaminant responsible for cracking). In addition, only specimens in loops three and four have been hydrogen peroxide cleaned; specimens in loops one and two thus have higher than typical levels of residual sulfur. Loop one is l atypical of actual RCS conditions in terms of both chemistry and residual sulfur.

Testing completed to date for the specimens from the test loops has included all non-destructive examinations, destructive examinations of "C" rings, and more detailed electron microscopy examinations of tube specimens from loops one, two and three. In specimens from loops two through four, no evidence of crack initiation or crack growth has been identified. Electron GPU Nuctear Corporation is'a sLDs@ary of GeceralPubhc Utahties Corporation

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microscopy examinations conducted June 29, 1984, on one tube specimen from the first loop identified a crack which had not been noted earlier.

Previous eddy current examinations by Westinghouse had noted an anomalous i

l l signal in that area since the second simulated operating cycle, although i

analysts at the laboratory felt it was not a crack. Neither the other lead test specimen in this loop, which cor.tained a known defect, nor any of the C-rings in this loop, had shown any new or continuing damage. The decision was made to allow the test to continue running and observe the addy current signature of the anomalous indication to watch for any additional changes.

A.s a consequence of the June 29 test results, GPU initiated a reexamination of the corrosion test program eddy current tapes by .

independent analysts inspecting the TMI-I steam generators. The analysts  !

also reviewed all other record tapes of the tube from which the specimen was taken. Close examination of an early 4xl absolute probe inspection tape (developed as part of an unrelated test program) identified a small indication in the area which is now the test specimen. It was concluded that a small defect was present in the tube before the corrosion test program was begun, but that it was below the threshold of detectability for the .540 probe. The independent analysts' review of the corrosion test program tapes indicated that this defect provided a detectable signal by the

! .540 probe after HFT and two cycles. Over the next three cycles, the ECT signal grew in amplitude. The preliminary interpretation of these data is i

propagation of a pre-existing crack. When the test program was complete, and the tube specimen was examined, the crack was through-wall radially for

approximately one half inch circumferential1y, and partially through wall (20-505) for an additional half inch.

From the evidence available to date, it can be concluded that the thiosulfate environment in loop one has a sufficiently high concentration of

' reduced sulfur species to propagate pre-existing cracks in tubing that has not been chemically cleaned. However, the absence of cracks in C-ring specimens indicates that these leveh are not sufficient to cause crack initiation on uncracked surfaces.

These results corroborate the effectiveness of GPU's corrective actions to prevent recurrence of the sulfur attack of the steam generator.

I The conditions in loop one are prevented in the RCS by the removal of thiosulfate from the plant, the chemical cleaning of the steam generator tubing, and by employing analytical techniques which permit ana ysis for i

both reduced and oxidized species of sulfur.

l GPU's assessment of the final metallographic tests is continuing.

Additional information will be provided to you as available.

Verytrul{yours,

\ .s R. F. Wilson l Vice President Technical Functions MJG: dis:0599f

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UNITED STATES OF AMERICA NUCLEAR REGULATORY COMMISSION ,

Before the Atomic Safety and Licensing Board In the Matter of )

)

METROPOLITAN EDISON COMPANY, ET AL.

) Docket No. 50-289-OLA

) ASLBP 83-491-04-OLA (Three Mile Island Nuclear ) (Steam Generator Repair)

Station, Unit No. 1) )

SERVICE LIST Sheldon J. Wolfe Atomic Safety and Lcensing Administrative Judge Board Panel Chairman, Atomic Safety and U.S. Nuclear Regulatory Commission Licensing Board Washington, D.C. 20555 -

U.S. Nuclear Regulatory Commission Docketing and Service Section (3)

Washington, D.C. 20555 Office of the Secretary Dr. David L. Hetrick U.S. Nuclear Regulatory Commission Washington, D.C. 20555 Administrative Judge Atomic Safety and Licensing Board Joanne Doroshow, Esq.

College of Engineering Louise Bradford Dept. of Nuclear and Energy Engr. Three Mile Island Alert, Inc.

The University of Arizona Tucson, Arizona 85721 315 Peffer Street Harrisburg, Pennsylvania 17102 Dr. James C. Lamb, III Administrative Judge Atomic Safety and Licensing Board 313 Woodhaven Road Chapel Hill, North Carolina 27514 Richard J. Rawson, Esq.

Mary E. Wagner, Esq.

Office of Executive Legal Director U.S. Nuclear Regulatory Commission Washington, D.C. 20555 Atomic Safety and Licensing Appeal Board Panel U.S. Nuclear Regulatory Commission Washington, D.C. 20555 l

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