ML20197H196
| ML20197H196 | |
| Person / Time | |
|---|---|
| Issue date: | 05/18/1993 |
| From: | Muscara J NRC OFFICE OF NUCLEAR REGULATORY RESEARCH (RES) |
| To: | Shao L NRC OFFICE OF NUCLEAR REGULATORY RESEARCH (RES) |
| Shared Package | |
| ML20197H148 | List: |
| References | |
| FOIA-97-488 NUDOCS 9812140023 | |
| Download: ML20197H196 (9) | |
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UNITED STATES
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NUCLEAR REGULATORY COMMISSION j
E WASHINGTON, D. C. 20555
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May 18, 1993 l
NOTE FOR:
Lawrence C. Shao, Director Division of Engineering, RES FROM:
Joseph Muscara Materials Engineering Branch, DE/RES
SUBJECT:
TECHNICAL
SUMMARY
OF NSRRC MEETING ON STEAM GENERATOR TUBE NDE HELD ON APRIL 28-29, 1993 The week before the subject NSRRC meeting we met (L. Shao, C. Serpan, J. Muscara) briefly with Mr. Beckjord to discuss plans for the NSRRC meeting.
Mr. Beckjord requested that, following the meeting, we prepare a technical summary of the meeting.
You then requested that I prepare such a sumary.
Enclosure (1) provides an updated agenda showing the actual speakers and Enclosure (2) is a summary of meeting presentations listed by author in the order presented.
p WW Joseph Muscara i
Materials Engineering Branch, DE/RES
Enclosures:
As stated cc:
E. Beckjord T. Speis J. Craig C. Serpan G. Sege 1
i 9812140023 981202 PDR FOIA WILLIAPf97-488 PDR G y 1) ljCO > ]
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May 18, 1993 r
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NOTE FOR:
Lawrence C. Shao, Director Division of Engineering, RES FROM:
Joseph Muscara Materials Engineering Branch, DE/RES
SUBJECT:
TECHNICAL
SUMMARY
OF NSRRC MEETING ON STEAM GENE l
HELD ON APRIL 28-29, 1993 The week before the subject NSRRC meeting we met J. Muscara) briefly with Mr. Beckjord to discuss p(lans for the NSRRC L. Shao, C. Serpan, Mr. Beckjord requested that following the meeting, we prepare a technical summary of the meeting.
following the meeting.
You then requested that I prepare such a summary 1
Enclosed is the update agenda showing the actual speakers and a summary of meeting presentations listed by author in the order presented.
I Original signed by Joseph Huscara s
Materials Engineering Branch, DE/RES
Enclosures:
As stated cc:
E. Beckjord T. Speis t
J. Craig C. Serpan G. Sege Distribution MEB Rdg. File J. Muscara MEB JMuse./
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Enclosure (1) l AGENDA FOR NSRRC NEETING ON STEAF GENERATOR TUBE N0NDESTRUCTIVE EXAMINATION APRIL 28 - 29, 1993 Chevy Chase Holiday Inn, Palladian Center i
5520 Wisconsin Avenue, Chevy Chase, MD 20815 i
Telephone No. (301) 656-1500 OBJECTIVE l
The purpose of this meeting is to review the status of information and research on nondestructive examination (NDE) of steam generator tubes l
and the pertinent background of technology and practices.
i April-28. 9:30 a.m. - 12:15 p.m.
l 9:30-9:45 I.
OPENING REMARKS E. Beckjord David Morrison II.
BACKGROUND AND OVERVIEW 9:45-9:55 o Introduction L. Shao, NRC/RES l
9:55-10:40 o Review of SGT Designs, Damage Mechanisms and C. Welty, EPRI Operating Experience 10:40-11:00 o BREAK l
11:00-11:30 o Eddy Current Test - Basics C. Dodd, ORNL l
11:30-12:15 o Overview of SG NDE Methods, Procedures, H. Houserman, ZETEC Personnel, i
Equipment, Practical Aspects amd Logistics for SG ISI April 28. 1:30 p.m. - 4:30 p.m.
III. CURRENT PRACTICES
. 1:30-2:00 o Westinghouse D. Malinowski 2:00-2:30 o B&W Nuclear Technologies (Includes CONAM)
T. Richards 2:30-3:00 o Zetec J. Siegel 3:00-3:15 o BREAK l
3:15-3:45 o French Practice R. Comby, EDF 3:45-4:30 COMMITTEE DISCUSSION 4
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April 29. 8:30 a.m. - 10:45 a.m.
-IV.
RESEARCH RESULTS f
'8:30-9:00 o Introduction to NRC's SG Tube Integrity Program J. Muscara, NRC/RES j
9:00-9:45 o Review of Surry SG Program-R. Kurtz, PNL 9:45-10:30 o Improved Multifrequency Eddy Current Inspection Program and Plans for Validation C. Dodd, ORNL 10:30-10:45 o BREAK April 29. 10:45 a.m. - 5:00 p.m.
V.
EMERGING TECHNOLOGY 10:45-11:15 Zetec J. Siegel 11:15-11:45 Westinghouse J. Driggers 11:45-12:15 French Representative R. Comby, EDF 12:15-1:45 LUNCH BREAK 1:45-2:15 Nuson Ultrasonic Inspection C. Morris 2:15-2:45 Neural Networks for ECT Signal B. Upadhyaya, U. of TN Evaluation 2:45-3:00 BREAK 3:00-3:30 PANEL DISCUSSION Moderator:
J. Craig, NRC/RES 3:30-5:00 COMMITTEE DISCUSSION The presentations in Session II aie intended to provide a general background of the different steam generator designs employed in PWRs and the types of damage experienced over the years for different generators. Also, the theory l
of eddy current testing as applied to steam generator tube inspections will be 1
l provided along with NDE methods, procedures, equipment and personnel used, and considerations of the practical aspects and logistics for conducting these t
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inspections.
In Session III, the providers of inspection service will discuss current steam generator tube inspection practices.
They will address the advantages and disadvantages of the techniques, the reliability of flaw detection and accuracy of flaw sizing and, in general, their experiences and findings from field inspections.
Session IV is devoted to discussion of recent, current and future research programs and results related to improvements for nondestructive testing of SG tubes.
Session V addresses emerging methods and technology that may provide improvements for inspections in the near term and in the future.
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l Enclosure (2) i TECHNICAL SUMMAY OF NSRRC MEETING HELD ON APRIL 28-29, 1993 t
Summary - April 28, 1993 Wel.ty I
Steam generator tube degradation mechanisms have evolved with time.
Wastage and denting were the predominant damage mechanisms in the early years.
t SCC (ID) and SCC / IGA (00) are now the most prevalent causes for tube plugging.
1 There has been a significant increase in recent years of ODSCC.
Some of the increase is due to improved flaw identification criteria and some is due to initiation and growth of ODSCC.
Control of SCC can not be obtained simply by using ultrapure secondary water.
It is now recognized that molar ratio control of some species is needed.
Replacement SGs have excellent service history to date.
This is mainly due to use of alloy 600 TT and 690 TT, stainless steel broached TSPs, thermal hydraulic analysis, improved SG management, and improved chemistry control.
There was considerable discussion of a suggestion by Mr. Burstein to reduce Tmax as a means of eliminating corrosion induced tube damage, it was not clear as how successful this might be in general as some corrosion damage is observed on the cold leg tubes.
D.9Ad Dodd discussed the basic principles of eddy current testing, properties of eddy currents and parameters which affect eddy current readings.
The main challenge in SG inspection is to interpret ET signals to determine the structural integrity of the tube.
Houserman There have been substantial improvements in equipment, procedures, and personnel training since the early days of SG inspection.
Computerized data analysis methods have been developed but they have not replaced the human analyst. Signal complexity would appear to limit how far automation of data analysis can be taken.
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Two independent analyses of data taken during a typical ISI are performed to reduce the possibility of missing flaw indications.
" Typical" SG-ISI requires significant quantities of equipment and personnel.
l Halinowski. Richards. Siecel State-of-the-art ET acquisition and analysis equipment used by all vendors.
Special probes and techniques have been developed to address specific damage forms.
The P0D for crack-type flaws generally low (< 50%) for cracks < 40%
through-wall.
P00 near 1.0 for cracks > 70% through wall and longer than 0.2 inches.
Length sizing of SCC reasonably accurate for through-wall cracks.
Depth sizing accuracy of SCC was not discussed.
Comby The approach taken toward SG-ISI in France has many similarities and l
differences compared to the methods in the U.S.
A defect specific strategy is used in France which involves ET techniques, reporting thresholds, specific analysis procedures and l
repair criteria for each kind of degradation.
There are 17 plugging criteria used in France with the major ones l
including:
ODSCC - voltage based i
Axial SCC - length based l
Circumferential SCC - any indication U-bends - any indication AVB wear - 40% depth (determined from voltage)
In general, more severely degraded tubes are allowed to remain inservice in France.
Techniques and procedures more standardized in France since i
I the SG population is more alike than in the U.S.
iiany SG replacements planned for the next few years Since the entire population of French SGs is relatively homogeneous this implies the replacement effort will be very intensive.
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. j Summary April 29, 1993 i
Muscara l
Summary of NRC research programs on SG tube integrity and inspection presented.
Some members of the NSRRC questioned the appropriateness of the SG tube mockup.
Questions were also raised about proposed research to develop predictive models for various forms of environmentally assisted cracking in steam generator tubes. One member of the NSRRC believed this to be an impossible problem. This project is intended to provide realistic inputs for evaluating flaw-specific plugging limits and for leak rate assessments.
The need to establish statistically significant estimates of P00 and flaw sizing reliability for crack-type flaws was emphasized.
Dodd The program for improved multifrequency eddy current inspection techniques was reviewed. Plans for validating the multiple-property measurement approach were described.
The improved ET inspection approach requires development of a better 4
probe design. A sixteen element reflection probe has been designed and is being constructed by ZETEC.
The second element of improved ET inspection requires improved data analysis methods. A neural network fitting method has been developed to enhance the determination of tube properties from the multiple frequency ET readings.
t Sieael Zetec is developing new equipment to respond to the need for improved I
inspection reliability. The MlZ-30 was developed to permit use of more sophisticated probe designs such as the 16 coil reflection probe.
Dual probing system has been developed to in:rease examination productivity, decrease exposure and cost.
Driocers Westinghouse has been developing advanced send / receive array probes combinued with bobin coils as an alternative to RPC inspection. This technique is much faster than RPC and therefore better suited as a highly sensitive screening probe.
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Advanced software and electronics being developed to implement the new probe technology.
Precision position control techniques for axial and rotary scanning being developed to provide improved inspection accuracy.
Considerable effort has gone into development of a combined UT and ET rotating probe. This probe has nigh sensitivity to OD indications, is immune to magnetic permeability variations or deposits, and provides I
good sizing accuracy.
Inspection rates are comparable to conventional RPC probes.
[omby The French are also putting considerable effort toward development of UT inspection techniques - especially for circumferential crack detection and sizing.
Other efforts include development of automatic acquisition and analysis i
of bobbin coil inspection data, vibration measurements on tubes susceptible to high cycle fatigue, and laser profilometry techniques for mapping dented tube geometries.
Comby also reported on the NDE examinations of the retired from service Dampierre SG. This is a model 27 SG exhibiting U-bend and roll transition PWSCC, TSP and TTS IGA /00 SCC, AVB wear and TSP denting, eleven teams have participated in the examinations using 32 inspection techniques. A limited number (51-797) of tubes have been removed to validate NDE results. Destructive examination of removed tubes is just beginning - no results were reported.
Morris a
UT techniques for SG tube inspection were described.
Accuracy of defect location was given as i 3mm since the pusher puller is positioned inside the channel head.
NUSON used mirrors rather than multiple element UT transducers to obtain multiple beam directions but still keep the probe size small.
UT sizing accuracy shown to be 10% of wall for cracks > 20% through wall.
Little data presented for cracks > 60% through-wall.
P0D claimed to be near unity for circumferential cracks > 30% through-wall.
This estimate is not statistically based.
Speed of NUSON split mirror window probe stated to be about 8X faster than motorized RPC probes.
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Results (if study into feasibility of using artifical neural networks for defect classification and defect parameter estimation using ET data was presented.
Center of gravity representation and data subtraction methods were found to be effective in defect parameter estimation.
Compressed integral data representation gave very good performance for defect classification.
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Techniques have only been applied to ASME tube standard. Application to nuclear plant data remains to be done.
Panel Discussion l
l Panel was moderated by J. Craig (RES), members consisted of D. Malinowski, T. Richards, H. Houserman and C. Welty.
Panel members agreed that present ET inspection equipment and procedures are adequate to detect "significant" flaws with high reliability.
Personnel training and qualification as prescribed by the EPRI Appendices G and H were judged to be adequate by panel members.
i It was discussed that the level of inspection reliability that is needed depends strongly on the damage mechanism since tube integrity at the end of an operating cycle (or the acceptance criteria at the time of the inspection) is, in turn, dependent on the damage mechanism.
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