ML050810474
| ML050810474 | |
| Person / Time | |
|---|---|
| Site: | Comanche Peak  |
| Issue date: | 03/14/2005 |
| From: | Blevins M, Madden F TXU Generation Co, LP, TXU Power |
| To: | Document Control Desk, Office of Nuclear Reactor Regulation |
| References | |
| CPSES-200500561, TXX-05059 | |
| Download: ML050810474 (22) | |
Text
- ? TXU TXU Power Comanche Peak Steam Electric Station P.O. Box 1002 (EO1)
Glen Rose, TX 76043 Tel: 254 897 5209 Fax: 254 897 6652 mike.blevins txu.com Mike Btevins Senior Vice President
& Chief Nuclear Officer Ref: 10 CFR 50.55a CPSES-200500561 Log #
TXX-05059 March 14, 2005 U. S. Nuclear Regulatory Commission Attn: Document Control Desk Washington, DC 20555
SUBJECT:
REF:
COMANCHE PEAK STEAM ELECTRIC STATION (CPSES)
UNIT 1, DOCKET NO. 50445 CPSES RESPONSE TO REQUEST FOR ADDITIONAL INFORMATION CONCERNING THE SPRING 2004 (lRFIO) STEAM GENERATOR INSERVICE INSPECTION REPORTS
- 1.
TXU Power letter, logged TXX-04085, from Mike Blevins to the U. S. Nuclear Regulatory Commission, dated April 27, 2004.
- 2.
TXU Power letter, logged TXX-04141, from Mike Blevins to the U. S. Nuclear Regulatory Commission, dated July 29, 2004.
- 3.
TXU Power letter, logged TXX-04157, from Mike Blevins to the U. S. Nuclear Regulatory Commission, dated August 27, 2004.
- 4.
TXU Power letter, logged TXX-04172, from Mike Blevins to the U. S. Nuclear Regulatory Commission, dated September 27, 2004.
Gentlemen:
By means of the letters referenced above, TXU Generation Company LP (TXU Power) submitted several reports to the NRC detailing the Steam Generator (S/G) inservice inspection completed at CPSES during the Spring 2004 refueling outage (lRFI0).
After review of these reports, NRC Staff has since submitted questions and requests for clarification to CPSES concerning these reports. A telephone conference was subsequently held on February 24, 2005, to discuss these questions and to ensure the answers provided by TXU Power were sufficient to address the information needed by the NRC staff to adequately review the previously submitted reports.
The attachment to this letter provides a summary of the telephone conference, including a listing of all participants. This attachment also contains a detailed listing of the NRC questions and a response to each by TXU Power.
A oq4 A member of the STARS (Strategic Teaming and Resource Sharing) Alliance Callaway
- Comanche Peak Diablo Canyon Palo Verde
- South Texas Project Wolf Creek
TXX-05059 Page 2 of 2 If there arc any questions concerning this submittal, please contact Mr. Bob Kidwell at (254) 897-5310.
This communication contains no new licensing basis commitments regarding CPSES Unit 1.
Sincerely, TXU Generation Company LP By:
TXU Generation Management Company LLC, Its General Partner Mike Blevns By:
2Vjila_
W. Madden Director, Regulatory Affairs RJK Attachment c -
B. S. Mallett, Region IV W. D. Johnson, Region IV M. C. Thadani, NRR D. H. Jaffe, NRR CPSES Resident Inspectors
Attachment to TXX-05059 REOUEST FOR ADDITIONAL INFORMATION COMANCHE PEAK, UNIT 1 SPRING 2004 (lRF10) STEAM GENERATOR INSERVICE INSPECTION REPORTS
Attachment to TXX-05059 Page 2 of 20 A conference call was held on 02/24/05 at 1300 CST to clarify NRC staff's questions concerning the post-I RF1 0 Steam Generator inspection reports previously submitted by TXU Power (References 1, 2, 3, and 4).
Attendees:
NRC Mohan Thadani Joseph Terrell Kenne th Karwoski TXU Power Westinghouse -
Fred Madden Steve Smith Tim Hope Dave Weyandt Vince Polizzi Bob Kidwell Bili Cullen PJ Prabhu Steve O'Neill Both the NRC questions, and a response to each by TXU Power, are contained on the following pages.
Attachment to TXX-05059 Page 3 of 20 General questions:
- 1.
Confirm that the only sleeves installed in the steam generators prior to 1 RFI 0 were Alloy 690 TIG-welded sleeves. Further confirm that these sleeves were installed during 1 RF9 and only in steam generators 2, 3, and 4.
RESPONSE
Confirmed - Alloy 690 TIG-welded sleeves only were installed for the first time during IRF09 in SGs 2,3 and 4.
- 2.
Confirm that +PointTm exams of the top-of-tubesheet (TIS) region were not conducted in the tubes that were deplugged in IRFIO since sleeves were to be installed to repair degradation in the expansion transition region of these tubes.
RESPONSE
Not confirmed - +FointTm (+Pt) inspection of deplugged tubes at TTS was performed. Actual +Pt extent included +3 to -10 inches bounding the TTS region. Although the initial inspection of-7 to -10 inches was established to bound the lower sleeve joint, it was later decided to simplify acquisition and use the TTS +3 inch upper extent as is done for all other HL tubes.
Ouestion from Affachment 2 of the April 27, 2004, submittal:
- 3.
On page 1, it is stated that six tubes were designated as F* tubes. Discuss the nature and location of the degradation in these tubes.
RESPONSE
1RF10 F* Tubes Row Col Ind Loc Inchl 42 43 SAI HTS
-2.49 SG1 39 68 SVI HTS
-4.81 SG2 31 17 SAI HTS
-5.04 SG3 44 49 SVI HTS
-3.06 SG4 98 6
SVI HTS
-6.37
____62 SVI CTS
-4 The indication on R31C17 SG2 is axial PWSCC. The indication on R42C43 SG1 is an OD signal of indeterminate origin and not likely attributed to degradation. The remaining indications (SVI) are likely historic lap signals.
These signals contain phase responses typical of the OD plane. Their depth below the top of tubesheet precludes secondary side contaminant ingress due to the mechanical roll expansion.
Attachment to TXX-05059 Page 4 of 20 Ouestion from the July 29, 2004. submittal:
- 4.
On page 2-1, it was indicated that the 0.540-inch wide grobve bobbin probe was site qualified. In addition, you indicated that the results from the 0.610-inch probe were regarded as truth for purposes of this site-qualification.
Given that the 0.610-inch probe may not detect all degradation (i.e., it may have a probability of detection of 0.80 at 90% confidence for its qualification database), discuss the basis for concluding that the 0.540-inch wide groove probe meets or exceeds the EPRI requirements. In addition, address how you ensured that the qualification database met the guidance in the EPRI guidelines concerning the number and size of flaws.
RESPONSE
The EPRI POD methodology uses a binomial approximation. As such, the listed POD is dependent upon sample size, and therefore could be misleading.
A 0.80 POD does not imply that 20% of the indications will be missed. For 11 samples with all detected the binomial POD is 0.80 at 90% confidence.
For 59 samples with 44 detected, POD = 0.80, and for 100 samples with 86 detected, POD = 0.80 at 90% confidence. Important to the site qualification is that the 0.540 inch wide groove is capable of detecting DSI signals of significance with regard to GL 95-05. The binomial POD of ETSS 96007.1 is 0.89 at 90% confidence for indications >60%TW (33 of 34 indications detected). The indication not detected was 62%TW, removed from the Farley Unit 1 site.
The method of site qualification of the 0.540 inch wide groove probe at Comanche Peak Unit 1 is consistent with the methodology applied at other sites. In these previous applications the methodology was discussed with NRC prior to application. The TXU implementation plan for the 0.540 inch wide groove probe called for any reported DSI to be plugged on detection, i.e., any DSI reported with the 0.540 inch wide groove is not justified for continued operation under GL 95-05.
The site qualification of the 0.540 inch wide groove probe showed that all indications >0.51V (based on the 0.610 inch analysis) were detected; indications <0.51V were also detected with the 0.540 inch wide groove probe.
Pulled tube data forming the database for the alternate repair criterion per GL 95-05 was investigated to determine an approximate depth of a 0.51V signal. The correlated depth for such a signal is 51%TW, and thus would not be considered in the ETSS binomial POD evaluation. As all DSI signals
>0.51V were detected with the 0.540 inch wide groove bobbin probe, the binomial POD for DSIs >0.51V is 0.93 at 90% confidence (31 of 31 detected).
A 0.51V (0.610 basis) bobbin DSI signal has no structural or leakage significance with regard to GL 95-05. Therefore, it can be concluded that the functional performance of the 0.540 inch wide groove bobbin probe is consistent with the 0.610 inch bobbin probe. A total of 71 DSI signals based on the 0.610" bobbin coil analysis were utilized for the 0.540" wide groove probe site qualification, of which 68 were reported by the 0.540" wide groove
Attachment to TXX-05059 Page 5 of 20 probe. The range of DSI voltages was 0.17 to 0.98 volt, based on the 0.610" bobbin coil analysis. The amplitudes of the DSIs not reported by the 0.540" wide groove probe were 0.19, 0.37, and 0.51 volt.
A log logistic POD was developed using the site qualification data. Due to the large number of DSIs evaluated and significant number of detections at a voltage lower than the lowest non-detected voltage, the POD curve shows that at PODs of 0.8 and 0.95 the 0.610 inch voltages are 0.00 and 0.20 volts.
The POD curve shape does not follow the typical "S-curve" shape of log logistic POD curves due to the presence of detections below the lowest non-detected voltage. The site qualification data and POD curve developed using the as reported data suggests that there is no functional difference in detection between the 0.610 inch bobbin and 0.540 inch wide groove bobbin coils. If the site qualification data is artificially adjusted to force no detection for all 0.610 inch basis DSIs <0.25 volt, at PODs of 0.8 and 0.95 the 0.610 inch basis voltages are 0.32 and 0.44 volts. This curve developed by forcing no detection for <0.25 volt DSIs has a characteristic shape and is judged consistent with industry data.
Furthermore, the detection conditions at Comanche Peak Unit 1 and other plants from which pulled tube data is contained within the ETSS 96007.1 database do not affo.d a direct comparison due to the improved noise condition at Comanche Peak compared to these other plants.
Attachment to TXX-05059 Page 6 of 20 Ouestions from Enclosure 1 of the August 27, 2004. submittal:
- 5.
On page 1, you indicated that the number of tubes with circumferentially oriented outside diameter stress corrosion cracking (ODSCC), ding ODSCC, and freespan ODSCC were less than that reported during the previous outage. In addition, you indicated that the flaws detected during IRF1O were less severe than in the prior inspection.
Discuss any insights into why this trend may have occurred. Include in the discussion any potential role data quality may have had in this trend (e.g., were the trends a result of more noise in the data).
RESPONSE
SCC initiation and propagation depends on a number of contributing factors that include temperature, time at temperature, environment, applied and residual stress, and material susceptibility. With no apparent change in environment, depletion of the most susceptible population through plugging could involve a decrease in the observed degraded population from one outage to the next. As the most susceptible population is eliminated by plugging, the future degraded population would be expected to be less numerous and less severe than previously observed indications. The observed degraded population from one outage to the next includes new initiates and indications that grow to a readily detectable condition at the reporting outage. Growth studies performed for Comanche Peak indicate that the majority of the observed indications contain a precursor signal in the prior inspection. This observation suggests that the aggressiveness of the secondary side chemistry condition is minimal. Chemical cleaning at the 1RF05 outage likely removed the most aggressive species with regard to attack of nickel based alloys. The ongoing chemistry monitoring and control suggests that measures are being taken to reduce the aggressiveness of the environment.
Data quality at the 1RF10 inspection was judged consistent with or improved compared to the 1RF09 outage. The observation of a higher percentage of vary small (i.e., <0.25 V) amplitude signals at 1RF10 compared to previous outages can suggest an improved detection condition. If data quality negatively affected the 1RF10 detection condition the IRF10 flaw amplitude distribution would include a lesser percentage of small amplitude signals. In addition, a noise comparison was performed for the 1RF09 and 1RF10 outages. +PointTrl noise conditions for IRF09 and 1RF10 are essentially equal. Bobbin noise for 1RF10 was bounded by the IRF09 noise statistics.
Attachment to TXX-05059 Page 7 of 20
- 6.
On page 2, you indicate that changes were made to the bobbin reporting criteria. Briefly discuss the nature of these changes. In particular, discuss whether the changes were conservative.
RESPONSE
Numerous conservative enhancements to the overall inspection campaign were implemented during IRF10 as an outcome of the lessons learned from 1RF09. Among the key changes to the bobbin analysis program conducted at 1RF10 was; adding a requirement that all bobbin signals in a particular structure to structure length of tubing be reported not just the largest; requiring the analyst to review data at a span of 5 and performing history lookups of any new signals to the first ISI/PSI. The most notable change was that no lower voltage threshold for reporting axial ODSCC in the freespan was used.
- 7.
On pages 4 and 5 of the submittal, you indicate that oblique PWSCC indications were detected in the Row 13 U-bends of four tubes. It is the staffs understanding, based on an analysis of the residual stresses imparted to the U-bend areas during tube fabrication, that the U-bends of the lower row tubes (e.g., rows 1 through 8) are considered susceptible to circumferential PWSCC, and the U-bends of the higher row tubes (e.g., greater than row
- 13) are susceptible to axial PWSCC.
Since oblique (circumferential) PWSCC was found in the U-bend region of a row 13 tube, discuss whether these findings have any implications with respect to your understanding of the phenomenon in this region of the tube bundle. In addition, discuss whether these findings have any impact on the inspection strategy for this region of the tube bundle.
RESPONSE
Susceptibility to oblique PWSCC indications in the U-bend decreases with increasing Rows and does not stop at Row 9. The results of the IRF10 U-bend inspection do not affect this conclusion nor do the 1RF10 inspection results affect future inspection strategy. Residual stress development in lower rows is highly complex and dependent upon a number of variables.
Prior to the IRF10 outage it was concluded that based on time at temperature, that Comanche Peak Unit 1 represented the highest PWSCC initiation potential of operating units. Therefore, the observation of indications is Row 13 is not unexpected. Note that the severity of the Row 13 indications were bounded by indications observed in lower Rows. The Comanche Peak 1RF10 inspection results suggest that for most tubes, the Comanche Peak material susceptibility may be reduced compared to other units. With increased operating experience, additional indications could be observed. It is likely that such indications will be observed in Rows <10.
Attachment to TXX-05059 Page 8 of 20 The initial inspection recommendations for axial PWSCC in larger radius U-bends was based on ovality conditions. Conservative assumptions regarding residual stress condition produced by the observed ovality condition appear to have been overly conservative since no axial PWSCC has been reported in any unit in large (i.e., >Row 10) radius U-bends at any site.
Tne IRF11 large radius U-bend inspection scope intends to follow a critical area and buffer zone approach based on the observed 1RF10 degradation.
- 8.
On page 5, you indicate that a volumetric signal was observed in the tube in Row 4, Column 91 of steam generator 1 on the cold-leg side near the ITS. You further indicate that upon further review the indication was judged to be a conservative overcall. Discuss the nature of the eddy current signal and why this indication was judged to be a conservative overcall.
RESPONSE
The IRF10 inspection yielded a small number of ECT indications that were conservatively reported as flaws, but prone to interpretation following a subsequent reviewed by the on-site Westinghouse Corporate Level III.
Fol!owing consultation with the site NDE Level III, the independent QDAs and the Westinghouse Senior Analyst some of these initial calls were deemed to be conservative overcalls and the final resolution report changed accordingly to indicate a non flaw condition. Supplementary information from subsequent examinations using mag-biased probes, slower test speeds and/or multi-frequency mixes, augmented by historical data comparisons formed the technical basis for the changes (note that the original I-Code was reported from the initial scan of the tube). Notwithstanding, if the highest level of confidence was not able to ensure the original call was indeed an overcall, the database was not changed. Such was the case for the above tube. Other cases were noted where volumetric reports from the initial scan associated with possible loose parts could not be observed after the part was removed. In these instances the influence of the object produced a false flaw signal. For R4 C91, the signal is lecated within the expansion transition, has a minimal +Pt amplitude (0.08 volt), and performs similarly to a deposit signal. The pancake coil response does not contain flaw-like components.
Attachment to TXX-05059 Page 9 of 20
- 9.
On page 5, it is stated that all newly rep3rted occurrences of preheater baffle wear (which are identified by bobbin) were inspected with a rotating probe. It is also stated that, through the previous outage, all previously reported baffle wear had been inspected with a
+PointTm probe.
Discuss how ODSCC would be detected in a wear scar if a rotating probe inspection is not performed (since not all wear scars were inspected during lRFIO). If the detection of ODSCC is accomplished in these cases by assessing changes in the bobbin signal, discuss the database used for demonstrating the adequacy of the signal change criteria. For example, discuss the amount of change expected in the bobbin coil response for various size cracks located in various sized wear scars.
RESPONSE
ODSCC coincident with wear scars has not been observed in Westinghouse SGs. The potential for development of this combined mode degradation is further reduced at Comanche Peak based on the application of chemical cleaning and reduced potential for deposit formation based on the location of baffle plate wear scars witbin the SG (high flow velocity regions within preheater). Detectlon of a combined ODSCC/wear condition would be expected to be made p'ssible by changes in the response characteristic of the
+Pt signal. SCC and wear scar responses produce differing signal characteristics to the +Pt coil.
Detectability of a iomrbined wear scar and SCC site is limited using the bobbin coiL. Thus a RPC sanmpling program is implemented.
- 10.
On page 5, you indicate that "SVI calls by RPC not associated with loose parts were traced to the first inservice inspection of the SGs. These indications were conservatively repaired at lRF1O." Clarify these statements. For example, discuss whether all tubes with manufacturing burnish marks, dings, and bulges were plugged.
RESPONSE
All volumetric indications (based on RPC examination) in the past and continuing through 1RF10 have been conservatively repaired. Conversely, MBMs, dings or bulges that do not produce a volumetric degradation response by RPC examination are not plugged. Tubes with signals classified as MBMs are left in service if the signal can be traced to the baseline or an earlier inspection with no apparent growth or signal characteristic change.
Dings or bulges are only repaired by plugging if the bobbin or RPC inspection suggests a crack-like response.
Attachment to TXX-05059 Page IO of 20
- 11.
On page 5, you indicate that the U-bend inspection scope for "dents" at anti-vibration bars (AVBs) was expanded to include all "dings" within +1 inch of the AVB since ODSCC associated with a ding was detected approximately 0.6-inches from an AVB using a +PointTm probe. On page 17, it is stated that all ding signals within 1 inch on either side of the AVB were examined with a +PointTm coil.
A.
Clarify whether the expanded inspection scope included 1 inch of the tube on both sides of the AVB or just 1 inch of the tube on only one side of the AVB.
RESPONSE
Expanded inspection scope included 1 inch on either side of the AVB.
B.
Discuss whether any ofthe less than 5 volt dings (as measured from the bobbin coil) in the U-bend region were examined using a +PointTm probe. If so, discuss whether any crack-like axial indications were detected. For the crack-like indications identified in the U-bend region, provide the size of the dent/ding, the location of the flaw (at an AVB or in the freespan), and the methods by which the flaw was detected (bobbin and/or rotating probe).
RESPONSE
Less than 5V dings in the U-bend are RPC inspected if a bobbin DNI' report is produced. Additionally, <5V dings in the U-bend without a bobbin DNI report were RPC inspected by default based on the manner that RPC data is collected. The standard data collection mode is from support to support. Therefore, the entire tube length between the supports is subsequently collected and analyzed. The response to question 20 provides a summary of all IRF1O ding ODSCC indications as reported by +Pt examination. Included in this summary is the associated bobbin coil call for that location.
In the case of R48 C30, the associated bobbin coil call of INR (indication not resolvable) does not affect the performance of a +Pt exam at this site. The pre-outage inspection plan established that all dings within +/- 1 inch of the center of the AVB would be inspected with the +Pt coil.
I Bobbin DNI code reflects a freespan "ding" indication that has greater than 10 degree phase angle change since the first ISI or a DNT at support plate H3. This code is changed to DNS if subsequent MRPC test does not confirm the indication.
Attachment to TXX-05059 Page I11 of 20
- 12.
On page 6, you indicate that one tube in steam generator 2 was plugged due to a large horizontal noise component that extended for essentially the entire length of the tube.
Discuss whether this noise was present during prior outages. If not, discuss any insights into the source of this noise.
RESPONSE
A review of IRF09 data indicates that horizontal noise was observed in tube R4 C104 in SG2. The condition appears to be similar to be pilger noise observed in other SG designs. This was judged to be inspectable at the 1RF09 outage. A circumferential indication was reported by +Pt examination at the hot leg top of tubesheet at IRF09 and sleeved. The enhanced industry sensitivity to noise conditions since the 1RF09 outage prompted the analyst to bring this condition to the attention of plant personnel. The tube was conservatively repaired by plugging at 1RF1O. The bobbin horizontal noise component at IRF10 was judged acceptable for detection using the ding reporting criterion, however the tube was plugged despite this judgment.
- 13.
In the middle of page 10, you indicate that, "Using the lower 90% probability, 50%
confidence line relating +Pt amplitude to PDA, the estimated PDA of this indication is
..." Confirm whether the word "lower" should be "upper."
RESPONSE
The word 'lower' should have read 'upper'.
- 14.
Question deleted at the request of NRC Staff.
- 15.
On page 13 of the submittal, it is stated that several in-situ pressure tests were performed during lRF10. Discuss whether there was any leakage at the proof test pressure for any of the tested tubes.
RESPONSE
There was no leakage at the proof test for any of the in-situ tested tubes (See Table 8 of the referred enclosure).
Attachment to TXX-05059 Page 12 of 20 16.
On page 16, the last two sentences on the page refers to the number of detected DNI signals from one inspection to the next, and briefly mentions the degree of change of confirmed DNI signals from one inspection to the next. Clarify these statements, including a discussion of their implications on looking for change in the bobbin signal to determine which indications should be tested with a rotating probe. Discuss whether these statements are simply implying that the change in the bobbin signal must be evaluated over more than one inspection interval.
RESPONSE
In IRF08 only one confirmed DNI was reported, but in 1RF09, as a result of a very deliberate 'change in history' review back to the first ISI, a total of 16 tubes were ultimately confirmed with ding ODSCC. Thus the change in history review, albeit over a long period of time did indeed drive a RPC inspection that otherwise would not have been performed based on initial bobbin signals alone. Therefore, by way of clarification, a change in the bobbin signal must be evaluated over more than one inspection interval since any significant change in amplitude from one inspection to the next is unlikely. Thus history comparison to as far back as the availability of data allows is being performed since 1RF09. This was done during 1RF10.
- 17.
On pages 18 and 19, tube wear due to foreign object interaction was discussed. Discuss whether the loose parts were removed. On page 5, it is mentioned that, "All loose part wear signals were conservatively repaired." Discuss whether the repaired tubes were stabilized.
It is also mentioned that the wear mechanism, in some cases, could be tracked to the previous inspection. Discuss whether there was any progression in the size of the wear scars and whether the loose part was "visible" either through direct visual observation or eddy current examination.
RESPONSE
The table provided on the following pages provides a summary of the loose parts identified, the method of detection, those PLPs removed and those that remained following 1RF10. Tubes repaired due to foreign object wear scars were evaluated for the need for stabilization and did not require stabilization.
Any report of volumetric degradation associated with PLPs were resolved by either plugging or plugging with stabilization. PLP locations that did not contain volumetric degradation were evaluated for continued operability.
Attachment to TXX-05059 Page 13 of 20 1RFIO PLP Summary SG Leg RowICol Loc Found By Shape Resolution Removed 1
HL R12C3, R12C4 ITS +Pointml' Star shaped, Object could not be removed, was No flat, curved also observed in IRF08 and 1RF09 1 CL R38C16 C2 Video 1"xl"xl/2" Object removed Yes I_
_Ihex nut 1
CL RlOC21 TTS +Pointrm Scale piece Broken up by video probe NA 1
HL R16C24 ITS +PointT¶ Scale piece No loose/foreign object NA stuck in crevice 1
HL Rl1C27 HiI
+PointT' Possibly the tack weld of stay rod to NA I___top TSP, not confirmed 1
HL R32C30, iTS +PointTM Small sludge Easily moved by video probe NA R33C30 rock or scale - -0.25" 1
HL R14C49 ITS +Point"'
Video insp. found no object in the NA vicinity 1
HL R32C59 TTS +PointTM Video insp. found no object in the NA vicinity I
HL R16C62 ITS +PointTm Video insp. found no object in the NA I
_I vicinity 1
CL R21C70, C2 Video 7"xl/64" dia. Object removed Yes R22C70 Wire F HL R30C72 ITS +PointTm Video insp. found no object in the NA vicinity F HL R43C72 TTS +PointTm Video insp. found no object in the NA vicinity F CL RI C73 TS +Pointrm Scale piece Broken up by video probe NA 1 CL R29C74 ITS +Pointfr 3/4"xl/4" Object removed Yes weld slag 1
HL R13C82, ITS +Pointrm Scale piece Broken up by video probe NA R13C83 F HL R15C86 TTS +PointTM Scale piece No loose/foreign object NA stuck in crevice 1
HL R17C86 ITS +PointTm Scale piece No loose/foreign object NA stuck in crevice 1
CL R8C88 CII +PointTm Possibly the tack weld of stay rod to NA top TSP, not confirmed 1
HL R23C99
'TS +PointTM Scale piece Broken up by video probe NA 1
CL R37C100 C2 Video l11x"xl/2" Object removed Yes hex nut 2
CL R13C8, R13C9, ClI +Pointrm Not confirmed, no wear or ding NA R14C9 indication in tubes at this location 2
HL R2C20, RiC21, H9
+Point'm Not confirmed, no wear or ding NA R2C21 indication in tubes at this location
Attachment to TXX-05059 Page 14 of 20 SG LeRg Row/Col Loc Found By Shape Resolution Removed 2
HL R47C30 HI 1 +Pointrm Not confirmed, no wear or ding NA indication in tube at this location 2
HL R48C31 HI I Bobbin Not confirmed, no wear or ding NA indication in tube at this location 2
HL Rl l C39 iTS +PointTM Video insp. found no object in the NA vicinity 2
HL R14C41 ITS +PointTNl Video insp. found no object in the NA vicinity 2
HL R31C43, TTS Video 0.32"x0.25" Wedged between tubes, not No R3 1 C44 sludge rock or dislodged by video probe weld slag 2
HL R23C44 TIS Video 3/8"xl/64" Could not be removed. Wedged No wire between tube and tubesheet 2
HL R25C44 ITS Video 3/4"xl/16" Object removed Yes wire 2
HL R27C44 TIS Video 1/2" x 1/4" x Object removed Yes 1/16" flex gasket 2
HL R28C44 ITS +PointTm Sludge No foreign object, except sludge NA accumulation 2
HL R29C77, TTS +PointTm Sludge rock Could not be removed. Wedged No R29C78 or scale between tubes 3.3" above ITS.
I_
_II_
Present in 1RF09 2
HL R47C79 TTS +PointTm Scale piece No loose/foreign object NA 3
CL R37C1 6 C2 Video
-1.5" washer Could not be removed. Wedged No between tubes, was present since 1RF06 3
CL R23C44, C2 Video 1.5"x5/16" Object removed Yes
- R24C44, dia. Threaded
- R23C45, rod R24C45 3
HL R37C52, ITS +PointThl 1/2" x 3/8" x Object removed Yes
- R36C53, 1/16" weld
- R38C53, slag R39C53 3
HL R24C55 TIS Video 3/4"xl/64" Object removed Yes dia. wire 3
HL R47C64, H9 Bobbin Not confirmed, no wear or ding NA R47C65 indication in tubes at this location 3
CL R21C70, C2 Video 1.5"x5/16" Object removed Yes
- R22C70, dia. Threaded
- R22C71, rod R22C71 3
HL R26C71 HI
+PointTm Video insp. found no object in the NA II
_vicinity
Attachment to TXX-05059 Page 15 of 20 SG LeglRow/Col Loc Found By Shape Resolution Removed 3
HL R9C102, TITS +PointTm Piece of scale Easily moved by video probe NA
- RlOC102, RIIC102, R12C102 3
HL R3C105 TIS Video 1/2"xl/32" Object removed Yes wire 3
HL R18C105 TTS +Pointrm Piece of scale No loose/foreign object NA 3
HL RR7C107 iTS +Pointrm Piece of scale No loose/foreign object NA 4
CL R37C16 C2 Video 0.25" x 1/2" x Object removed Yes 1/4" curved metal 4
HL R12C20 TTS +PointTt Video insp. found no object in the NA vicinity 4
HL R3C21 TIS +Point'm Scale piece Broken up by video probe NA 4
HL R29C27 TTS +PointTNI Scale piece Broken up by video probe NA 4
CL R23C43 C2 Video 1.5"xl/8" Object removed Yes piece of drill 4
CL R33C51, C2 Video 3.5"xl/8" dia Object removed Yes R34C51 weld rod 4 HL R29C56 ITS +PointTm Video insp. found no object in the NA vicinity 4
HL R28C59 TIS +PointTM 5/16"xl/8" Would not move when pulled by No sludge rock gripper 4
HL R25C64 TIS +PointTm Scale piece in No loose/foreign object NA Crevice 4
HL R28C67 TIS +PointTm' Scale piece Broken up by video probe NA 4
HL R24C69 TITS +PointTml Video insp. found no object in the NA vicinity 4
HL R25C69 TIS +Pointrm Video insp. found no object in the NA vicinity 4
HL R23C70 TITS +Pointrm Scale piece in No loose/foreign object NA Crevice 4
HL R23C74, TITS +PointTm Scale piece Broken up by video probe NA R24C74 4
HL R31C76 TITS +PointTm Video insp. found no object in the NA vicinity 4
HL R24C77 TITS +PointTm Scale piece in No loose/foreign object NA Crevice 4
HL R18C81 TIS +Pointrm Scale piece in No loose/foreign object NA Crevice 4
HL R19C81 TIS +Pointrm Scale piece in No loose/foreign object NA Crevice 4
HL R20C85 TITS +Pointrm Video insp. found no object in the NA vicinity 4
HL R27C87, TITS +Point-hl Scale piece Broken up by video probe NA R27C88 I
I I
I
Attachment to TXX-05059 Page 16 of 20 SG Row/Col Loc Found By Shape Resolution Removed 4
HL R8C88, R9C88 HI 1 +PointTm Possibly the tack weld of stay rod to NA top TSP, not confirmed 4
CL RI 5C88 CII
+Pointrm Not confirmed, no wear or ding NA I
__IIindication in tube at this location 4
HL RI OC89 HI1
+Pointrm Not confirmed, no wear or ding NA indication in tube at this location 4
HL R3 1 C92 TTS +PointTmf Video insp. found no object in the NA vicinity 4
HL R34C93 ITIS +Pointm Scale piece Broken up by video probe NA Further review of the volumetric signals reported at IRF10 suggests that 5 tubes may have degradation associated with possible loose parts (PLP), one in SG3, and 4 in SG4. All are located at cold leg baffles. The one in SG3 was initially reported as a DSI at 1RF10. Review of the 1RFO9 bobbin data indicates the presence of a signal of similar amplitude. Thus the degradation had initiated prior to the IRFO9 outage. Of the four in SG4, three were reported by bobbin coil as DSI or NQI and confirmed by +Pt examination.
The fourth indication was reported only by +Pt examination. This tube was inspected based on the established procedure of testing of surrounding tubes if volumetric degradation is reported on the initially tested tubes. Of the four tubes in SG4, the one with no bobbin detection had the lowest +Pt flaw amplitude, shortest axial length, and shortest circumferential length. The three reported by bobbin coil were observed to contain bobbin signals based on history review to at least the 2002 (QRFO9) inspection, and two were observed to contain bobbin signals based on history review to the 2001 (1RF08) inspection.
- 18.
On page 20 regarding the 2.22 volt oblique PWSCC indication, it was stated that the
+PointTm probe diameter was 0.560 inches instead of 0.610 inches. Discuss why the smaller probe was used.
RESPONSE
The indication was located in the U-bend region of the tube. Testing in the bend region of the generator requires the use of flexible probe heads. For use in 0.750" O.D. tubing, the probe bodies are available in 0.580'" and 0.560" O.D. This test was conducted with the 0.560" probe that was in use at the time. For RPC probes, body diameter has no effect on detection as the eddy current coil is spring loaded to maintain surface contact. The 0.580" and the 0.560" probes are functionally equivalent for this test. RPC probe body diameter does not affect detection performance, as may occur with bobbin probes due to a decrease in fill factor.
Attachment to TXX-05059 Page 17 of 20 Ouestions from Attachment 1 of the August 27, 2004, submittal:
- 19.
On page 2, item 15, you indicate that a +PointTm inspection was performed in the region of the lower roll joint (ITS, -7 inches to -10 inches) on tubes selected for the installation of Alloy 800 leak-limiting sleeves. In the supporting information (ML042050194) provided to the staff in preparation for the April 23, 2004 conference call, you indicate that eddy current examination was completed in the parent tube at the locations of the lower (mechanical roll) and upper (hydraulic expansion) sleeve joints.
Discuss whether a +PointTm examination was performed in the parent tube in the location of the upper sleeve joints. If not, discuss how you ensured that the parent tube in the location of the upper sleeve joints was in a condition similar to that in the sleeve qualification program (e.g., no circumferential cracks, cracks associated with dents/dings, etc.).
RESPONSE
+Pt examination was not performed on the parent tube in the location of the upper joint. All sleeved tubes (initial or deplugged) were included in the 100% bobbin inspection program which included the HL straight sections and bounded the upper joint area. A number of conditions provided reasonable assurance of a defect free upper joint including; the absence of circ cracks in the straight leg freespan in the Unit 1 SGs, only a limited number of confirmed axial freespan ODSCC with or without dings, performance of a 100% +Pt inspections for all dings > 5 volts and a 20% +Pt inspection of all dings > 2 volts between the TTS and 113. Finally, a post sleeve installation +Pt inspection of the sleeve and parent tube, 3 inches from the sleeve ends, confirmed the absence of any defects and established a baseline for future ISIs.
- 20.
On pages 7, 10, 14, and 17, you listed tubes which were removed from service by mechanical plugging. In many instances, the indications were categorized as dings (DNG), dents (DNT), permeability variation (PVN), restricted tube (RRT), or possible sleeve collapse (PSC).
A.
For each flaw that was associated with dings/dents, provide the location, dent/ding voltage, orientation of the flaw (i.e., axial, circumferential), and the degradation mechanism (i.e., ODSCC, PWSCC, etc.). Discuss whether the flaw was detected with a bobbin and/or a rotating probe. If a flaw was detected in a dent less than 5 volts and was only detected with a rotating probe, discuss the basis for not expanding the rotating probe examination for dents/dings less than 5 volts. In addition, discuss whether any random rotating probe examinations are performed in less than 5 volt dent/dings.
RESPONSE
The following table summarizes ding/dent SCC observation for 1RF10. All indications are axial ODSCC. For ding locations not in close proximity to AVBs the bobbin detection technique shows detectability beyond the qualified range of less than or equal to 5V.
Attachment to TXX-05059 Page 18 of 20 The initial +Pt program for proximity to AVBs included all dings/dents within 1 inch on either side of the AVB. This is performed due to potential bobbin signal response influence from the AVB itself. The table below includes several cases where detection by only +Pt was noted. In the case of R11 C58 the indication was observed at a ding at the U-bend tangent. No initial bobbin DNG report was noted. The bobbin data was reanalyzed to identify >5V dings at U-bend tangents. Additional +Pt testing was performed as a result of this reanalysis. No further indications were noted.
IRF10 DING Flaws History 1RF10 1RF10 Bobbin Ding
+Pt
+Pt Signal Volts SG Row Col LOCN ELEV Chi Volts Length in 2004 1
27 51 CIO 37.2 5.84 1.11 0.44 DNI 1
48 30 AVI 0.76 2.57 0.47 0.18 INR2 2
4 75 C9 34.5 0.71 0.16 0.29 DNI 2
14 48 H3 4.04 1.85 0.14 0.19 DFI 2
19 30 ClH 3.37 1.85 0.44 0.2 DFI 2
27 8
AV3 0.43 11.43 1.17 0.35 DNG 2
37 35 C9 31.6 0.59 0.14 0.19 DNI 2
42 78 AV2 27.4 2.11 0.32 0.2 DNI 3
11 58 ClH 2.89 5.83 0.77 0.24 NDD 3
49 78 AV2 3.36 1.56 0.29 0.14 DNI 3
48 29 AV4 0.03 3.76 0.3 0.15 DNT B.
With respect to the indications detected in dents and dings, discus whether the data show any trends on the susceptibility of the dent/ding to cracking based on temperature or the severity of the dent/ding. If there are no trends, discuss the implications with respect to your rotating probe sampling strategy for dents and dings.
RESPONSE
The observed trends support the historical trending that shows a reduced initiation potential for larger voltage dings. The majority of the Comanche Peak ding ODSCC indications have occurred in the U-bend region. This occurrence is likely related to partial detubing and retubing during initial manufacture. Observed trends are consistent with historical trends. No changes are planned for the 1RF11 inspection.
2 INR "Indication Not Reportable" code is used by the analyst when a previously reported indication us detected; however, the current guidelines do not require reporting.
Attachment to TXX-05059 Page 19 of 20 C.
For indications designated as PVN, discuss whether the indications have changed since the previous inspection.
RESPONSE
Magnetically biased probes are used for further evaluation of PVN signals. In some cases use of these probes eliminates the PVN response. A change evaluation was not implemented for PVN signals between 1RF09 and 1RF10. Individual probe performance affects response to PV. PVN signals at 1RF10 were evaluated individually to determine if the PVN signal could mask a flaw that could grow to a potentially structural or leakage significant condition. If so, the indication was preventively repaired by plugging. Tubes plugged due to PVN are a data quality issue related to the PVN itself. The PVN code does not imply that degradation is present.
D.
For indications designated as RRT, discuss the cause and location of the restriction. Discuss whether this condition was present during the previous inspection and whether the degree of restriction increased since the previous inspection. Discuss whether this condition is service-induced. If the condition is service induced, discuss the cause. Discuss any implications with respect to tube integrity.
RESPONSE
Restrictions at IRF10 were coincident with previous dent/ding locations. The degree of restriction is dependent upon the stiffness of the inspection probe and ability to collect quality data should not be used to formulate a hypothesis that restriction severity is changing.
Restricted observations in non-sleeve locations are not service induced. Restrictions were also noted in sleeves and for these cases the phenomenon is understood. Such cases have no implication upon tube integrity. These locations were plugged for data quality concerns, not due to progression of the dent/ding.
Attachment to TXX-05059 Page 20 of 20 E.
For indications designated as PSC, discuss the cause of the sleeve collapse and the types of sleeves involved. Provide either a copy or summary of Reference 8 (WPT-16550, "Evaluation of Collapsed TIG Welded Sleeves at Comanche Peak Unit 1," April 2004).
RESPONSE
The sleeved tubes plugged due a PSC report permitted passage of the standard diameter +Pt probe used for sleeve inspection through the entire length of sleeve. The +Pt response contained a horizontal noise component similar to a dent-like response. It was concluded that this observation was associated with incipient collapse, and thus the sleeved tubes were plugged. Reference 8 uses a methodology consistent with other past evaluations for other occurrences of sleeve collapse. In summary, the evaluation concludes that the weld remains intact (thus maintaining structural and leakage integrity) and the hardroll joint retains axial load bearing capability above the design requirement. The evaluation considered the internal tube to sleeve crevice pressure and axial loading induced through Poisson contraction when evaluating integrity of the weld and hardroll.