ML20050A284
| ML20050A284 | |
| Person / Time | |
|---|---|
| Site: | Ginna, 05000000, Crane |
| Issue date: | 03/19/1982 |
| From: | Harold Denton Office of Nuclear Reactor Regulation |
| To: | Moholt B CENTER FOR ENVIRONMENTAL HEALTH |
| References | |
| NUDOCS 8204010008 | |
| Download: ML20050A284 (5) | |
Text
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Dear Dr.11olholt:
Your letter of February 15, 1982 to Chairrun Palladino was referred to ne for reply.
In your letter you refer to recent steam generator tube inspection results from Three Mile Island Unit 1 and the Ginna Nuclear Power Plant, and you conclude by reconnending that the NRC nandate fiber optic inspection in all pressurized water reactors.
For your infornation the primary neans used to inspect for stean generator tube degradation is eddy current testing (ECT). This method is used because it can detect and measure the depth of flaws in stean generator tubes.
Fiber optic inspection and other visual techniques such as television cameras are incapable of detecting all forns of steam generator tube degradation. They are, however, used to supplenent ECT findings, to detect and locate foreign material in stean generators, and to aid in steam generator tube repairs.
In the case of Tri! Unit 1, tube degradation was first determined using the ECT imthod with subsequent fiber optic inspection used to visually confirm that the proper tubes were being repaired. At the Ginna nuclear plant, fiber optic inspection was used to locate and characterize the recent stean generator tube f ai lu re.
During this inspection, foreign material was found in the faulted stean generator.
The NRC has relied upon quality control measures to provide assurance against foreign material renainins in stean generators after inspections or repair opera t ions. Although these measures have been reasonably effective, due to recent events we are reassessing our requirenents in this regard.
It is uncertain at this time whether or not the existing quality control neasures will be supplenented by visual inspection techniques, such as fiber optics, since these events are currently under active review.
I trust that the information provided by this letter is responsive to your letter.
Sincerely, Origin:t signed by
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PDR llarold R. Denton, Director Office of Nuclear Reactor Regulation h
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Bruce Molholt, Ph.D.
Director Center for. Environrental health 1315 Walnut Street Suite 1632 N Philadelphia,' Pennsylvania 19107 N
Dear Dr. Molholb Your letter of Fet uary 15, 1982 to Chairnan Pallddino was referred to re for reply.
In your letter you refer to recent stean generator tube inspection results fron Three Mile, Island Unit 1 and the Ginna Nuclear Power Plant, and you conclude by recommending that the NRC nandate fiber optic inspection in all pressurized water reactors.
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For your infornation the primary neans used to inspect for steau generator tube degradation is eddy current testing (ECT). This method is used because it can detect and reasure the depth of, flaws in stean generator tubes.
Fiber optic inspection and other visual techniques such as television caneras are incapable of detecting all forus of stean generator tube degradation.
They are, however, used to supplement ECT findings, to detect and locate foreign naterial in stean qenerators, and to aid in steam'gerie ator tube repairs.
In the case of TM1 Unit 1, tube degra'dation was first determined using the ECT nethod with subsequent fiber optic inspection used to visually confirn that the proper tubes were being repaired.
At the Ginna nuclear plant, fiber optic inspection was used to locate and characterize the recent stean generator tube f a i lu re.
During this inspection, foreign ' material was found in the faulted stean generator.
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The NRC has relied upon quality control naasu'res to provide assurance against j
foreign naterial renaining in stean generators \\af ter inspections or repair opera t i on s.
Although these neasures have been Effective, the Ginna event oay cause us to reassess our requirerents in this regard.
It is uncertain at this time whether,or not the existing quality control rnasures will be supplemented by visual inspection techniques, such as fiber optics, since this event is currently.under active review.
i I trust / that the information provided by this letter is\\ responsive to your letter.
/
Sincerely, Harold R. Denton, Director Office of buclear Reactor Regulation
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Dr. Nunzio J. Palladino, Chairman
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Wa shington, D.C. 20555 15 February 1982 Re:
Steam generator tubes in PWRs
Dear Dr. Palladino,
Twice in the past month significant damage to steam generator tubes of pressurized-water nuclear reactors have been dis-covered during detailed inspections.
In November, 1981, at Three Mile Island, Unit 1, the routine type of inspection for steam generator tubes indicated that 124 were damaged.
Closer inspection last month, however, revealed that as many as 10,000 tubes at TMI-1 contain cracks.
Until fiber optics were employed, the extent of tube damage in the steam turbine at TMI-1 was vastly underestimated.
Similarly, at the Ginna reactor, much more extensive damage to steam turbine tubes was found than anticipated upon examination with fiber optical systems.
There have been recent reports of extensive damage to piping due to corrosion at other nuclear power plants, such as at Indian Point.
Given that corrosion and foreign body damage to tubing within the steam turbines may be a rather common feature of pressurized-water reactors, it would behoove the Nuclear Regulatory Commission to catch these " accidents waiting to happen" before another incident like the Ginna site emergency, or worse, erupts.
I strongly urge the Nuclear Regulatory Commission to mandate complete fiber optical inspection of all extant pressurized-water reactors in the U.S. at their next i
l refueling.
Yours sincerely, W (hlY C
/ ruce Molholt, Ph.D.
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/ Director NRC Commissioners Senstors Conc r es s men _
Press.
Victor Gilinsky Arlen Spector William H. Gray, III Wilford Peter A.
Bradford H. John Heinz, III Robert Edgar Wald John F. Ahearne Alan K. Simpson Allen Ertel Sullivan Thomas M. Roberts Garv Hart Robert Alvarez Stranahan
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Secretary Bruce Molholt incom.ing-From: _. Center for Environmental Health Palladino
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2/15/82 oate To:
steam generator tubes in PWRs
Subject:
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