ML20085M679
| ML20085M679 | |
| Person / Time | |
|---|---|
| Site: | Comanche Peak  |
| Issue date: | 06/27/1995 |
| From: | Terry C, Walker R TEXAS UTILITIES ELECTRIC CO. (TU ELECTRIC) |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| References | |
| GL-95-03, GL-95-3, TXX-95169, NUDOCS 9506290303 | |
| Download: ML20085M679 (12) | |
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g Log # TXX 95169 ,
-- File # 10035 >
F7 Ref. # 10CFR50.54(f)
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. g GL 95-03 1l9 ELECTRIC
% 7,,, June 27. 1995 Group Vke Presides U. S. Nuclear Regulatory Commission Attn.: Document Control Desk Washington, DC 20555 0001-
SUBJECT:
COMANCHE PEAK STEAM ELECTRIC STATION (CPSES) -
DOCKET NOS. 50 445 AND 50-446 UNITS 1 AND 2 RESPONSE TO GENERIC LETTER 95 03, "CIRCUMFERENTIAL CRACKING OF STEAM GENERATOR TUBES" REF: 1) Generic Letter 95 03, "Circumferential Cracking of Steam Generator Tubes." dated April 28, 1995 ,
Gentlemen:
On April 28, 1995, the NRC issued Generic Letter 95 03, "Circumferential :
cracking of Steam Generator Tubes" (Reference 1). j Pursuant to Section 182a of the Atomic Fnergy Act of 1954, as amended, and 10 CFR 50.54(f). TU Electric.is submitting a response under affirmation (Attachmeni.1) to the requested information and requested actions as stated ,
in Reference 1. The response is provided in Attachment 2 (Unit 1) and Attachment 3 (Unit 2).
If you have any questions, please contact Carl B. Corbin at (214) 812-8859.
Sincerely, d' B.
C. L. Terry By:_ N
- Roger D. Walker Regulatory Affairs Manager Attachments c- Mr. L. J. Callan, Region IV Resident Inspectors. CPSES (2) .
Mr. T. J. Polich. NRR l s
9506290303 950627 PDR ADOCK 05000445 !
P PDR P.O. Box 1002 Glen Rose. Texas 76043
. j Attachment 1 to TXX 95169- '
Page 1 of 1 .
UNITED STATES OF AMERICA ,
NUCLEAR REGULATORY COMMISSION .
In the Matter of )
)
Texas Utilities Electric Company ) Docket Nos. 50 445 1
) and 50 446 (Comanche Peak Steam Electric )
Station, Units 1 & 2) ) e i
AFFIDAVIT l l
Roger D. Walker being duly sworn, hereby deposes and says that he is the ".
Regulatory Affairs Manager, fNuclear Production of TV Electric, the licensee herein: that he is duly authorized to sign and file with the Nuclear Regulatory Commission this Response to Generic Letter 95 03 -
"Circumferential Cracking of Steam Generator Tubes"; that he is familiar with the content thereof: and that the matters set forth therein are true and correct to the best of his knowledge, information and belief. '
1 1
W Roger M. Walker
~
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Regulatory Affairs Manager, 1 Nuclear Production !
1 STATE OF TEXAS )
) i COUNTY OF )
Subscribed and sworn to before me, on this A7 dayofhbnL' ,
1995. #
L
. _ _ _ . . ________, 1
. CAROLYN L.COSENTINO
.,g.memm.sm.m...,
l My comm. tapes WW98 y[hgg '
d NotaryJPublic i
Attachment 2 to TXX-95169 Page 1 of 6 UNIT 1 RESPONSE TO GENERIC LETTER 95 03.
"CIRCUMFERENTIAL CRACKING OF STEAM GENERATOR TUBES" INTRODUCTION A number of incidents have been documented regarding circumferential cracking in Alloy 600 mill annealed (MA) tubing (Ref. NRC Information Notice (IN) 92-80 and IN 90 49). These cracks have initiated from both .
the primary and secondary tube surfaces. As is the case at Maine Yankee, the occurrence of circumferential cracking has principally been at the steam generator hot leg tubesheet expansion transition region at the top of the tube sheet. There are also several units where circumferential cracking has occurred at low radius u-bends. Two units at one plant (the ,
steam generators are now retired) have had confirmed circumferential cracking at dented support plate intersections.
The most recent inspection findings concern circumferential cracking at steam generator tube expansion regions (Maine Yankee and Arkansas Nuclear One Unit 2) and appear to have impacted those steam generators utilizing the Combustion Engineering (C E) EXPLANSION process more than others.
While there are similarities between the EXPLANSION process and the Westinghouse WEXTEX process used in a portion of the Comanche Peak Steam i Electric Station (CPSES) Unit 1 tubes, the degree to which Westinghouse units, regardless of the tube expansion process, have been affected by circumferential cracking is significantly less than the most recent experience of the C E units. Furthermore, the reported sludge pile height at Maine Yankee (up to 18 inches) may have influenced detectability of indications. CPSES has no sludge pile.
UNIT 1 i
CPSES Unit I has four Westinghouse Model D4 steam generators. The D4 has the following design characteristics:
. Alloy 600 MA tubing, 3/4" 0D, 0.043" wall,
. Full depth hardroll mechanical expansion of the tube in the tube sheet for the majority of tubes (89.5%) and full depth explosive expansion (WEXTEX) for the remainder, and
. Drilled carbon steel support plates.
Unit 1 is currently in its fifth fuel cycle. At the start of cycle 5.
Unit I had 3.6 effective full power years (EFPY) of operation. Unit I has no tubes plugged or sleeved as a result of service related degradation.
Beauested Information (1) of GL 95-03:
A safety assessment justifying continued operation that is based on the evaluations performed in accordance with requested actions (1) and (2) above.
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Attachment 2 to TXX 95169 1 Page 2 of 6 Requested Actions (1) Evaluate recent operating experience with respect to the detection and sizing of circumferential indications to determine the applicability to their plant.
(2) On the basis of the evaluation of item (a) above, past inspection scope and results, susceptibility to circumferential cracking, threshold of detection, expected or inferred crack growth rates, and other relevant factors, develop a safety assessment justifying continued operation until the next scheduled steam generator tube inspections are performed.
SAFETY ASSESSMENT SUSCEPTIBILITY There are ten operating units (including CPSES Unit 1) with steam generators containing full depth hardroll Alloy 600 MA tubing. Seven of those units have reported circumferential cracking at the tubesheet expansion region. There are nine operating units (including CPSES Unit 1) with WEXTEX expanded Alloy 600 MA tubing. Of the nine units, only CPSES Unit I has not reported circumferential cracking at the tubesheet expansion region. Low radius u bend circumferential cracking has been reported at three units with Alloy 600 MA tubing. Due to the fact that a number of units with alloy 600 MA tubing have observed circumferential cracking, TV Electric has taken measures to minimize this potential.
Measures have been taken both prior to operation and on an ongoing basis to help prevent degradation from occurring.
Prior to operation, the tube sheet expansion transition regions were shot peened. The peening process imparts a thin layer of compressive stress on the tube ID which inhibits the initiation of primary water stress corrosion cracking (PWSCC). The predominant mode of circumferential degradation in units with 3/4" full depth roll expansion has been secondary side initiated, suggesting that the peening application has been successful at mitigating the initiation of PWSCC, particularly when applied prior to operation. To address the potential for PWSCC in the low radius u-bend regions, these areas were in situ heat treated, prior to operation, as a form of stress relief. The stress relief was conducted from tangent to tangent on all row I and 2 u bends.
Secondary chemistry environment is a major factor in the initiation of outside diameter stress corrosion cracking (ODSCC). In particular, the presence of significant sludge accumulations at the tube sheet surface is associated with ODSCC at the roll transition of full depth expanded tubing, To address the potential for ODSCC at this location, aggressive chemistry controls have been implemented to minimize accumulation of sludge at the tube sheet surface. These controls are part of an overall chemistry program to maximize steam generator reliability and serve to inhibit initiation of stress corrosion cracking throughout the steam generator secondary side. Components of this program include limiting
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. 1 Attachment 2 to TXX 95169 Page 3 of 6 corrosion product transport. elimination of secondary side copper and sodium sources and implementation of molar ratio control.
These actions have been very successful to date. Corrosion product transport during cycle four has averaged 0.74 ppb and molar ratio averages 0.32. CPSES has not observed hideout return of corrosive impurities as reported by other units. To further quantify the success of the chemistry actions, sludge lancing during the most recent outage (1RF04) removed a '
total of only 8 lbs of sludge from the four SGs. Additionally, a limited inspection of the upper tube bundle from the secondary side confirmed the ,
absence of any significant corrosion products at the tube surface, tube supports and tube support plate crevices.
PREVIOUS RESULTS Unit 1 is in its fifth fuel cycle and has therefore completed four refueling outages. The inspection program at CPSES Unit I has consistently included a 20% sample of the available steam generator tubes for full length multifrequency bobbin coil examination during each refueling, 3-coil rotating pancake coil (RPC) probes have been used during each of these inspections to characterize signals which were not readily resolvable by bobbin coil alone. The inspection sample was distributed between the four steam generators during the first refueling.
Subsequent inspections have involved two steam generators on a rotating basis.
Refueling outage four (1RF04), conducted during March 1995, represented l
the first application of 3 coil RPC technology other than for signal characterization. During 1RF04, a total of 2505 tubesheet expansions were examined using the 3 coil RPC probe in the two steam generators selected for examination. This represents 27.4% of the available intersections, including 100% of the WEXTEX expanded tubes in those two. steam generators.
Additionally. 552 (6%) of the first hot leg tube support plate intersections were examined using 3 coil RPC. During the tubesheet expansion inspection, indications were noted which were inconsistent with the expected response from either a flawed tube or a tube free of degradation. To better understand the signal response, supplemental examinations were conducted using magnetically biased and Plus Point coils, as well as ultrasonics. Recognized industry experts were mobilized to CPSES to assist in this evaluation. The supplemental examinations confirmed that the indications were anomalies rather than degradation.
Inspection results have been encouraging. The detection of '
circumferential cracking is typically preceded by other forms of intergranular attack / stress corrosion cracking. There is no evidence of any active corrosion mechanism occurring in the steam generators. As previously mentioned, there are no tubes plugged or sleeved due to service related degradation. There has been no observations of significant primary to secondary leakage.
DATA ANALYSIS Beginning at 1RF04, plant specific steam generator data analysis
Attachment 2 to TXX 95169 Page 4 of 6 guidelines have been and will continue to be used. These guidelines as with prior application of vendor guidelines incorporate the latest industry information relative to proper analysis techniques for damage mechanisms including circumferential cracking. The current CPSES guidelines, which were used during 1RF04 incorporate the latest EPRI recommendations on detection and sizing of circumferential cracks (EPRI letter of Feb. 23. 1995 " Points to Consider in Circumferential Crack Detection and Length Sizing"). These recommendations were also specifically incorporated into the data analyst training program.
Subsequent to the analyst training. each analyst must successfully complete a written test of their knowledge of the guidelines and damage mechanisms. Additionally, each analyst must complete a test on their ability to apply the guidelines to eddy current data from actual flawed tubes, including tubes with circumferential cracks. Each analyst is required to successfully complete both the written test and performance demonstration prior to performing data analysis at CPSES.
Eddy current data at CPSES is reviewed by two independent analysts employed by the eddy current vendor. This primary and secondary analysis provides reasonable assurance that indications are not missed. Qualified TV Electric personnel perform an oversight function of the vendor. During 1RF04 an independent vendor was contracted to provide a third party review of eddy current results. This third party review was utilized to provide an objective perspective external to the principle vendor. "
CPSES uses qualified data analysts (ODAs). At a minimum, the primary data analysts are ODAs. During 1RF04. each shift lead data analyst for the third party vendor was also a ODA.
JUSTIFICATION FOR CONTINUED OPERATION Examination hardware and analysis techniques utilized at CPSES are sufficient to identify circumferential degradation. Limiting through wall crack angles for laterally restrained 3/4" tubing having a single through wall crack with a 50% degraded ligament have been established by Westinghouse as 240' (Westinghouse Owners Group letter 0G 95-03 from Roger Newton to WOG Primary Representatives, dated June 14, 1995). These angles establish the structural adequacy limits that satisfy the requirements of Reg. Guide 1.121 burst margin for 3 times normal operating pressure differential which is more conservative than the steam line break differential pressure. Such an indication, if found in the field would likely indicate an arc length of 360" based on industry accepted detection thresholds. Additionally, it is expected that through wall cracks of this size would experience primary to secondary leakage, as was the case for
, the McGuire kinetically welded sleeve event. Results provided by Westinghouse indicate that there have been no circumferential indications found in either WEXTEX or full depth hardroll expanded tubes which have failed to satisfy the burst requirements of Reg. Guide 1.121 either by test or analysis.
Growth rates are difficult to obtain due to the industry practice of repairing the tube when circumferential degradation is found. Occasions
. have occurred where it has been possible to reanalyze prior years data
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. l Attachment 2 to TXX-95169 Page 5 of 6 following observation of a previously unidentified indication.
Preliminary results have been obtained from Westinghouse regarding a plant with 3/4" full depth roll expanded tubing, This effort on a limited sample of 17 indications indicate that over a one year period the average arc length growth was essentially zero, with a maximum rate at 60 . The average peak depth growth of these indications was 14%, with the maximum peak depth growth at 52%.
Considering the fact that CPSES has no active corrosion related degradation. the maximum arc length and depth growth rates of 60 and 52%
respectively, the bounding condition for Regulatory Guide 1.121 structural integrity and the industry accepted detection thresholds, no degradation -
is expected which would compromise tube integrity at the end of the current operating cycle.
Recuested Information (2) of GL 95-03:
A summary of the inspections plans developed in accordance with i requested action (3) above and a schedule for the next planned ;
inspection. j Requested Action (3) Develop plans for the next steam generator tube inspections as they pertain to the detection of circumferential cracking.
The inspection plans should address, but not be limited to, scope (including sample expansion criteria, if applicable),
methods, equipment, and criteria (including personnel training and qualification).
FUTURE INSPECTIONS The next scheduled steam generator inspection will be conducted during the fifth refueling outage. This outage is scheduled to commence in September 1996. During this inspection, examinations will be performed in each of the four steam generators. A sample of approximately 40% of the tubes in both steam generator 1 and 4 will be selected for full length bobbin coil .
examination. This sample will include all remaining tubes which have not been inspected since baseline. A full length bobbin coil examination of a sample of at least 20% of the tubes in steam generators 2 and 3 will also be performed. All tubes in steam generators 2 and 3 have been inspected at least once since commercial operation. The sample for each steam generator will consist of tubes selected at random plus an augmented sample of tubes containing previously detected eddy current indications.
Supplemental techniques will be utilized, as appropriate, to resolve ambiguous eddy current results.
To further address the potential for circumferential cracking at the l hotleg tubesheet expansion area. 20% of the tubes in each of the four i steam generators will be inspected at the hot leg expansion transition :
with techniques to supplement bobbin coil. Likewise. for low radius I u bends, 20 % of the tube u bends in rows 1 and 2 of each steam generator .
will be inspected using supplemental techniques. To address the potential
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Attachment 3 to TXX 95169 Page 1 of 4 UNIT 2 RESPONSE TO GENERIC LETTER 95 03.
"CIRCUHFERENTIAL CRACKING OF STEAM GENERATOR TUBES" INTRODUCTION A number of incidents have been documented regarding circumferential cracking in Alloy 600 mill annealed (HA) tubing (Ref. IN 92-80 and IN 90-49). These cracks have initiated from both the primary and secondary tube surfaces. As is the case at Maine Yankee, the occurrence of circumferential cracking has principally been at the steam generator hot leg tubesheet expansion transition region at the top of the tube sheet.
There are also several units where circumferential cracking has occurred at low radius u-bends. Two units at one plant (the steam generators are now retired) have had confirmed circumferential cracking at dented support plate intersections.
The most recent inspection findings concern circumferential cracking at steam generator tube expansion regions (Maine Yankee and Arkansas Nuclear One Unit 2) and appear to have impacted those steam generators utilizing the Combustion Engineering EXPLANSION process more than others. While there are similarities between the EXPLANSION process and the Westinghouse WEXTEX process used in a reortion of the Comanche Peak Steam Electric Station (CPSES) Unit 1 tut'es the degree to which Westinghouse units.
regardless of the tube expansion process. have been affected by circumferential cracking is significantly less than the most recent experience of the C E units. Furthermore, the reported sludge pile height at Msine Yankee (up to 18 inches) may have influenced detectability of indications. CPSES has no sludge pile.
UNIT 2 CPSES Unit 2. has four Westinghouse Model D5 steam generators. The D5 has the following design characteristics:
- Alloy 600 thermally treated (TT) tubing, 3/4" OD, 0.043" wall,
- Full depth hydraulic expansion of the tube in the tube sheet, and
. Quatrefoil stainless steel support plates.
Unit 2 is currently in its second fuel cycle. At the start of cycle 2, !
Unit 2 had 0.9 EFPY of operation. Unit 2 has no tubes plugged or sleeved '
as a result of service related degradation.
Requested Information (1) of GL 95-03:
A safety assessment justifying continued operation that is based on the evaluations performed in accordance with requested actions (1) and (2) above.
Attachment 2 to TXX 95169 Page 6 of 6 for circumferential cracking at dented support plates, all dents exceeding i 5 volts at the lowest hot leg support plate will be examined with !
supplemental techniques. The particular inspection hardware and analysis I techniques selected for each of these areas will be based upon the potential damage mechanism (s), industry experience and examination state ;
of the art at the time of the inspection. The inspection hardware and l analysis techniques shall be consistent with industry practice for '
detecting circumferential degradation. Analysis training will continue to specifically indoctrinate the analyst on the technologies associated with the reliable detection of circumferential degradation.
The standard industry practice has been to repair (plug or sleeve) upon detection of a circumferential crack. This is based in part on the threshold of detection and uncertainties as to crack growth rates. This practice of repair on detection will be implemented at CPSES until such time as the industry reliably defines the uncertainties related to detection sizing and growth rates. If any circumferential degradation is detected, 100% of the tubes in each of the steam generators will be examined in the area along the tube length where the crack was detected.
Expansion criteria for defects which are not circumferentially oriented will be consistent with Technical Specification 4.0.6.
CPSES personnel continue to maintain an industry awareness in steam generator maintenance and inspection issues (including circumferential cracking) through participation in industry, EPRI and owners group forums.
These efforts allow TV Electric to stay informed of industry experience and inspection enhancements so they can be integrated into our inspection activities. In this manner TU Electric will be better able to ensure utilization of the most appropriate inspection methodologies during future inspections.
Attachment 3 to TXX-95169 Page 2 of 4 Requested Actions:
(1) Evaluate recent operating experience with respect to the detection and sizing of circumferential indications to determine the applicability to their plant.
(2) On the basis of the evaluation of item (a) above, past inspection scope and results, susceptibility to circumferential cracking, threshold of detection, expected or inferred crack growth rates, and other relevant factors.
develop a safety assessment justifying continued operation until the next scheduled steam generator tube inspections are performed.
SAFETY ASSESSMENT SUSCEPTIBILITY There are 16 domestic Westinghouse units (including CPSES Unit 2) operating with Alloy 600 TT hydraulically expanded tubing. Experience, as well as laboratory results, indicate thermally treated tubing is much less susceptible to stress corrosion cracking in general than mill annealed tubing. Also Westinghouse data indicates the residual stress levels present in hydraulically expanded tubing are lower than in either mechanically or explosively expanded tubing. Based upon the extensive operational experience to date. which extends to 1980, none of these units have reported any circumferential cracking.
The enhancements incorporated in the fabrication of the CPSES Unit 2 steam generators eliminate the need to perform the localized preventive measures to preclude initiation of PWSCC conducted in Unit 1. These enhancements include use of the hydraulic expansion process to expand the tube in the tube sheet. Additionally, the u-bends in rows 1 through 9 were heat treated as a form of stress relief prior to steam generator assembly.
These material and fabrication enhancements notwithstanding, as in Unit 1 a similar program of aggressive chemistry controls commensurate with the steam generator characteristics has been in place since the beginning of operation to minimize the potential for initiation of any corrosion damage.
PREVIOUS RESULTS During the first Unit 2 refueling outage (2RF01), a full length examination of 23.9% of the total number of steam generator tubes was performed using multi frequency bobbin coil techniques. These examinations were conducted in each of the four steam generators.
Additionally, 359 tubes were examined using 3-coil RPC at the hot leg tubesheet expansion. These examinations were distributed between steam generator 1, 2 and 4. As in Unit 1. 3 coil RPC was also used to characterize signals which were not readily resolvable by bobbin coil alone. No tubes were plugged during this inspection.
There is no evidence of any active corrosion mechanism occurring in the
Attachment 3 to TXX 95169 Page 3 of 4 steam generators. As previously mentioned there are no tubes plugged or sleeved due to service related degradation. There has been no observations of significant primary to secondary leakage.
DATA ANALYSIS The inspection conducted during 2RF01 (October 1994) was prior to the development of plant specific steam generator data analysis guidelines.
However, the analysts were indoctrinated in the latest industry information relative to proper analysis techniques for all damage mechanisms including circumferential cracking. As mentioned previously, the current CPSES analysis guidelines incorporate the latest EPRI -
recommendations on detection and sizing of circumferential cracks as does the CPSES data analyst training program.
As described in the Unit 1 discussion, CPSES uses two independent analysts employed by the eddy current vendor to analyze all eddy current data with qualified TU Electric personnel performing an oversight function of the vendor. At a minimum the primary analyst is a QDA.
JUSTIFICATION FOR CONTINUED OPERATION Examination hardware and analysis techniques utilized at CPSES are sufficient to identify circumferential degradation. Limiting through wall crack angles necessary to satisfy the requirements of Regulatory Guide l 1.121 for Alloy 600 TT would be consistent with Alloy 600 MA tubing.
Since there is no domestic operating experience of circumferential degradation at any units with Alloy 600 TT hydraulically expanded tubing, it is reasonable to assume growth rates of postulated circumferential indications are negligible. When considering these negligible growth rates, the currently accepted industry detection thresholds for circumferential degradation and the limiting through wall crack angles, no degradation is expected which would compromise tube integrity at the end of the current operating cycle.
Reauested Information (2) of GL 95-03:
A summary of the inspections plans developed in accordance with requested action (3) above and a schedule for the next planned inspection.
Requested Action (3) Develop plans for the next steam generator tube inspections as they pertain to the detection of circumferential cracking.
The inspection plans should address, but not be limited to, scope (including sample expansion criteria if applicable).
methods, equipment, and criteria (including personnel training and qualification).
Attachment 3 to TXX-95169 '
Page 4 of 4 FUTURE INSPECTIONS The next inspection for Unit 2 is scheduled for February 1996 during the ,
second refueling outage (2RF02). During this inspection two steam generators will be selected for examination. The inspectico scope will consist of a sample of at least 40% of the tubes in each of the two steam generators selected. Each tube will be examined over its full length using standard multi-frequency bobbin coil technology. This sample will include a random component plus an augmented sample of tubes containing previously detected eddy current indications. Supplemental techniques will be utilized, as appropriate, to resolve ambiguous eddy current results. -
While circumferential cracking in Unit 2 is not anticipated due to the previously mentioned material and fabrication enhancements, supplemental techniques will continue to be used to monitor for the onset of degradation. For this reason, an examination of a 40% sample of the tube sheet expansion transitions in each selected steam generator will be ,
performed using supplemental techniques. Likewise, a random sample of 40%
of the row 1 and 2 u bends in each selected steam generator will also be inspected using supplemental techniques. Additionally, all dents exceeding 5 volts at the lowest hot leg support plate will be examined with supplemental techniques. As in Unit 1, the particular inspection hardware and analysis techniques selected for each of these areas will be based upon the potential damage mechanism, industry experience and examination state of the art at the time of the inspection. The inspection hardware and analysis techniques shall be consistent with industry practice for detecting circumferential degradation. Analysis 4
( training will continue to specifically indoctrinate the analyst on the :
technologies associated with the reliable detection of circumferential degradation.
As described in the Unit 1 discussion, the practice of repair on detection ,
will be implemented at CPSES until such time as the industry reliably defines the uncertainties related to detection sizing and growth rates.
If any circumferential degradation is detected,100% of the tubes in each of the steam generators will be examined in the area along the tube length where the crack was detected. Expansion criteria for defects which are ,
not circumferentially oriented will be consistent with Technical -
Specification 4.0.6.
As mentioned in the Unit I discussion, CPSES personnel continue to maintain an industry awareness in steam generator maintenance and '
inspection issues (including circumferential cracking) through participation in industry, EPRI and owners group forums. These efforts allow TU Electric to stay informed of industry experience and inspection enhancements so they can be integrated into our inspection activities. In
, this manner TV Electric will be better able to ensure utilization of the most appropriate inspection methodologies during future inspections. :
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