ML20092P549

Forwards Hd Hukill 840703 Followup to to NRC Re Status of Steam Generators.Certificate of Svc Encl.Related Correspondence

ML20092P549
Person / Time
Site:	Three Mile Island
Issue date:	07/03/1984
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 8407090082
Download: ML20092P549 (4)

Text

'%S RELATED COREspCNDENCE

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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 Professor of Nuclear Engineering U.S. Nuclear Regulatory Commission University of Arizona Washington, D.C. 20555 Tucson, Arizona 85271 BY FEDERAL EXPRESS Dr. James C. Lamb, III Administrative Judge _

Atomic Safety and Licensing Board.d ed c

313 Woodhaven Road x-Chapel Hill, North Carolina 2755'4 t g Jo x.=.

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In the Matter of Metropolitan Edison Company, Et Al.

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& QD (Three Mile Island Nuclear Station, Unit No. 1); Q Docket No. 50-289-OLA and ASLBP 83-491-04-OLA --

o F (Steam Generator Repair) N

Dear Administrative Judges:

For the information of the Hearing Board and the parties, I am enclosing a copy of a letter sent today by Licensee to the NRC staff which follows up on the letter of June 27, 1984 con-cerning the status of the TMI-l steam generators.

Jiaper.elyyours,f i

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v 4_ f( vYhurchill Bruce.W.

Enclosure' cc: Service List (attached) 8497090002 840703 PDR ADOCK 05000289 .

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.. l GPU Nuclear Carperstlen '

5 duclear  :::e5;a-Middletown. Pennsylvania 17057 0191 717 944 7621 TEl.EX 84 2386 Writer's Direct Olal Number:

5211-84-2169 July 3, 1984 Office of Nuclear Reactor Regulations Attn: John F. Stolz, Chief Operating Reactors Branch No. 4 U. S. Nuclear Regulatory Connission Washington, D.C. 20555

Dear Mr. Stolz:

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

Operating License No. DPR-50 Docket No. 50-289 TMI-1 Steam Generator Inspection In my letter of June 27, 1984, I described additional testing being conducted to investigate a small leakage increase in the "B" steam generator. This testing is now complete.

As reported previously, bubble testing identified only one tube as bubbling significantly, tube 80-45 in OTSG "B". A fibrescope was placed in tube 80-45 with the secondary pressurized. Water could be seen coming through a crack at a point above the kinetic expansion joint qualified length, confirming that the leakage path was between the tube and tubesheet. This tube has been plugged.

Drip tests of the "B" steam generator identified nine plugs in the lower tubesheet, and three tubes that were dripping very slightly. The three tubes (which included 80-45) had all been previously identified by the bubble test. Eight of the slightly dripping plugs were rolled plugs.

Slight dripping or wetness is acceptable and not unexpected for this type of joint. A third plug was an explosively welded plug, which was repaired by placing a new plug below it.  ;

Eddy current testing using a differential probe has now been conducted for i all tubes identified as bubbling, all tubes with less than 40 percent through wall indications left in service in the "B" generator, and .

approximately seventy other tubes in the "B" generator which are p.srt of the l supplemental ECT sample population. No new eddy current indications were found. No known indications were found to have grown. No tubes that were bubbling have any ECT indications below the kinetic expansion joint, confirming that bubbling is past the joint in all cases. No additional ECT .

is planned. l l

GPU Nuclear Corporation la a subsidiary of the General Public Utilities Corporation a

t One very low voltage ECT signal was noted by data analysts in tube 70-8 in

.the "B" generator, six inches above the lower face of the upper tube sheet.

A review of previous. inspections showed a signal of the same shape and voltage at that location for both pre- and post- expansion inspections, indicating that this signal does not represent a new or growing defect.

This size and type of signal, which is very close to the threshold of detectability of the probe in use, cannot reliably be distinguished from background using this probe. This threshold of detectability has been considered and found acceptable in GPU's evaluation of the steam generators. When such small signals are identified, additional inspections using the more sensitive 8x1 probe are normally conducted to determine whether the anomalous signal represents an ECT indication or simply part of background. The additional time necessary to prepare equipment and to carry out this inspection is not considered warrented for one tube. Rather than leave the steam generators open to oxygen for the additional time period this tube will be plugged as a precautionary measure.

In addition to the two tubes described above, GPU plans to plug one additional tube in the "B" generator, tube 79-41. This is one of the slightly bubbling tubes identified in my June 27, 1984 letter. Although it bubbled so slightly that the water surface above remained undisturbed, bubble formation at the tube surface appeared somewhat more frequent than for other slight bubblers. In the interest of maintaining secondary activity levels as low as possible, this tube is being plugged.

GPU's investigations of the small leakage increase are now complete, and plugging is complete. The steam generators will be closed and returned to service this week. All evidence continues to support the conclusions drawn in GPU's submittals on the acceptability of the steam generators for return to service. Baseline leakage will be re-established, as required after plugging, prior to criticality.

Sincerely,

. . kill i Vice President - TMI-1 HDH/MJG/ RAS /mle cc: R. Conte J. Van Vliet l

.- -- . - - . - - - - - - - - . - - A

4-i I

UNITED STATES OF AMERICA NUCLEAR REGULATORY COMMISSION Before the Atomic Safety and Licensing Board In the Matter of )

)

METROPOLITAN EDISON COMPANY, ET AL. ) Dccket 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 Licensing 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 U.S. Nuclear Regulatory Commission Dr. David L. Hetrick Washington, D.C. 20555 Administrative Judge Atomic Safety and Licensing Board Joanne Doroshow, Esq.

Professor of Nuclear Engineering Louise Bradford University ~of Arizona Three Mile Island Alert, Inc.

Tucson, Arizona- 85271 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 j

-U.S. Nuclear Regulatory Commission *'

Washington, D.C. 20555 Atomic Safety and Licensing Appeal Board Panel'.

U.S. Nuclear Regulatory Comission Washington, D.C. 20555 l

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