ML20086S416
| ML20086S416 | |
| Person / Time | |
|---|---|
| Site: | Farley  |
| Issue date: | 07/31/1995 |
| From: | WESTINGHOUSE ELECTRIC COMPANY, DIV OF CBS CORP. |
| To: | |
| Shared Package | |
| ML20086S408 | List: |
| References | |
| SG-95-07-010, SG-95-7-10, NUDOCS 9508010220 | |
| Download: ML20086S416 (90) | |
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FARLEY UNIT 2 r
L 1995 INTERIM PLUGGING CRITERIA 90 DAY-REPORT f
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[ JULY 1995
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i Westinghouse Nuclear Energy Systems
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FARLEY UNIT 2 k
1995 INTERIM PLUGGING CRITERIA 90 DAY REPORT
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JULY 1995 E-
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WESTINGHOUSE ELECTRIC CORPORATION ENERGY SYSTEMS BUSINESS UNIT NUCLEAR SERVICES DIVISION 9_ P.O. BOX 355 PITTSBURGH, PENNSYLVANIA 15230 l
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FARLEY UNIT 2 1995 INTERIM PLUGGING CRITERIA 90 DAY REPORT g JULY 1995 i
TABLE OF CONTENTS 1
1.0 Introduction B !
2.0 Summary and Conclusions 3.0 Farley Pulled Tube Data 3.1 Farley 21995 Pulled Tube Examination Results 3.2 Farley 2 Pulled Tube Evaluations for ARC Applications 3.3 Comparison of Farley-1 Data with Existing IPC Correlations 4.0 EOC-10 Inspection Results and Voltage Growth Rates 4.1 EOC-10 Inspection Results 4.2 Voltage Growth Rates I 4.3 Probability of Prior Cycle Detection 4.4 Assessment of RPC Co Armation Rates 4.5 NDE Uncertainties 5.0 Data Base Applied for IPC Correlations I 6.0 SLB Analysis Metbods 7.0 Bobbin Voltage Distributions 7.1 Probability Of Detection (POD)
I 7.2 Calculation of Voltage Distributions 7.3 Comparison of Predicted and Actual EOC-10 Voltage Distributions 7.4 Predicted EOC 11 Voltage Distributions 8.0 Tube Leak Rate and Burst Probabilities 8.1 Jomparison of Predicted and Actual EOC-10 Tube Leak Rate and l Probability of Burst (PoB) for EOC-10 8.2 Predicted Leak Rate and Tube Burst Probability for EOC-11 9.0 Comparison of POPCD for 9 Inspections, 7 Plants with EPRI POD 10.0 References I s.\APC\apr95\APR90 DAY.12 ii 07/24/95. 14 46 5
FARLEY UNIT 2
, 1995 INTERIM PLUGGING CRITERIA 90 DAY REPORT
1.0 INTRODUCTION
This report provides the Farley Unit 2 steam generator bobbin voltage distribution summary, together with Steam Line Break (SLB) leak rate and tube burst probability analysis results, in support of the implementation of a 2.0 volt Interim Plugging l Criteria (IPC) at End Of Cycle 10 (EOC-10) according to NRC guidelines.
I Calculations ofleak rates and probability of tube burst (PoB) are reported, based on actual EOC-10 bobbin voltage distributions. Also provided are projections of bobbin voltage distributions, leak rates and burst probabilities for Cycle 11 operation. The methodology used in these evaluations is in accordance with previously published Westinghouse reports (Reference 10.1).
The application of the Interim Plugging Criteria (IPC) at Farley Unit 2 involves bobbin coilinspection of the tube bundle and plugging of >2.0 volt indications which are confirmed by Rotating Pancake Coil (RPC). Plugging of >3.6 volt bobbin indications is performed regardless of RPC inspection results. Calculations of SG tube leak rate and probability of burst during a postulated SLB are within regulatory requirements.
I SMPC\spr95NAPR90 DAY.12 1-1 07/24/95, 14 46 l
1
i 2.0
SUMMARY
AND CONCLUSIONS SLB leak rate and tube burst probability analyses were performed for the actual EOC-10 bobbin voltage distributions and are projected for EOC-11. SG C was found to be the limiting SG at EOC-10 and is projected to be the limiting SG for Cycle 11.
The calculations demonstrate that IPC performance at EOC-10 (actual distribution) and EOC-11 satisfy NRC criteria for allowable leakage and burst probability.
A total of 198 indications were found in the EOC-10 inspection of which 35 were RPC inspected and 17 were confirmed as flaws by the RPC inspection (all 17 were above 1.0 volt, including one above the IPC limit of 2.0 volts); 196 of the 198 were returned to service for Cycle 11. SG C had 99 bobbin indications, of which 30 were above 1.0 volt and 16 of these were confirmed by RPC inspection. Only one RPC-confirmed i indication (in SG C) was above the 2.0 volt IPC repair limit. There were no abnormal indications such as circumferentially oriented indications or PWSCC at TSP locations !
found in the 1995 EOC-10 inspection.
4 For the actual EOC 10 bobbin voltage distribution, the SLB leak rate for the limiting SG C is calculated to be 0.25 gpm and the burst probability is 2.8 E-05 for SG C, substantially lower than the Farley Unit 2 allowable SLB leakage limit of 11.4 gpm and the NRC guideline of 10 2 for the tube burst probability (Reference 10.2). The projections for EOC-10, performed at EOC-9, estimated the tube burst probability at 4.6 E-05 and SLB leakage at 0.20 gpm. Both are in good agreement with that obtained for the actual EOC-10 distribution. The small difference in SLB leak rate is attributable to methodology differences between Draft NUREG 1477 used at EOC-9 and the draft NRC generic letter used at EOC-10. The EOC-10 actual voltage distribution was reasonably predicted with a POD = 1.0 and excessively conservative for the NRC required POD = 0.6.
During the outage, tubes previously plugged in accordance with prior repair criteria for ODSCC at TSPs were deplugged, inspected and either returned to service in accordance with IPC criteria or replugged. Accordingly,111 such indications wne returned to service, for a total of 307 indications returned to service for Cycle 11 operation in accordance with IPC criteria.
Using the NRC criteria of POD = 0.6 to calculate the performance of Farley Unit 2 during the next operating cycle (EOC-11) in the limiting SG C, the SLB leak rate is predicted to be 1.23 gpm and the burst probability is predicted to be 1.05 E-04 at EOC-11. These results are much lower than the IPC requirement on allowable leakage (11.4 gpm) and the NRC guideline of 1.0 E-02 for the burst probability.
S \APC\spr95\APR90 DAY.12 2-1 07/2495, is.s7
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One tube with three TSP intersections was pulled during the EOC-10 outage to obtain data to support the EPRI ARC database. The tube had a field indication of 1.86 volts at TSP 1. Reevaluation of the field data identified a small 0.31 volt indication at TSP 3. Destructive examination found maximum crack depths of 92%,
36% and 34% at TSP 1 to 3, respectively. Thus, the two field NDD indications at TSPs 2 and 3 were shallow with < 36% maximum depth. Crack morphology and corrosion of the pulled tube were consistent with and did not affect the IPC/ ARC l
database. The TSP 1 indication was leak tested with no leakage identified. The g burst pressure found for the TSP 1 indication was 7,350 psi, which is just below the 3 mean of the EPRI burst correlation. The Farley-2 pulled tube results do not significantly change the EPRI ARC burst or probability ofleakage correlations.
To assist development of a voltage dependent probability of detection (POD) to more accurately project bobbin indication distributions for IPC evaluations, analyses were performed for the probability of prior cycle detection (POPCD) which includes indications that were missed during the previous inspection, indications below the g detectability threshold of the previous inspection, and new indications appearing E since the previous inspection. POPCD was evaluated for the EOC-8 and EOC-9 inspections, based on indications RPC confirmed plus not RPC inspected at EOC-9 and EOC-10, respectively. The inclusion ofindications not RPC inspected leads to E
E a lower bound POD assessment since it can be expected that many of these low voltage (< 1.0 volt) indications would not be confirmed by RPC. A POD assessment based on RPC confirmed indications is appropriate for IPC applications since only g
indications detected by both bobbin and RPC probes would have potentially contributed to significant leakage and burst probability over the prior operating cycle.
This is based on the database for POD versus maximum depth from pulled tube l examinations that show that both bobbin and RPC PODS approach unity at > 90% g depth. For pulled tube indications at TSP intersections that were called RPC NDD 5 by field inspection, none have exceeded 62% depth by destructive examination. The Farley -2 POPCD for the EOC-8 and EOC-9 inspections strongly supports a voltage g dependent POD substantially higher than the NRC uniform POD value of 0.6, and E approaching unity above about 1.8 volts. Except for the 1.2 to 1.8 voltage range, the POPCD obtained at EOC-10 for the EOC-9 inspection is higher than that obtained ,
at EOC-9 for the EOC-8 inspection. There are only 3 to 5 indications in each bin in the 1.2 to 1.8 voltage range in the EOC-9 inspection and 1 or 2 missed indications can significantly affect the POPCD values for those bins. Hence, the dips found in the POPCD distribution in the 1.2 to 2.0 voltage range for the two inspections are not l.
statistically significant.
POPCD evaluations for nine inspections in seven plants, including the last two Farley-2 inspections, have been evaluated and are compared in this report.
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Comparisons of the combined POPCD evaluation for all nine inspections with that L for the five inspections performed since 1992 also show the overall improvement in POD since 1992. The POPCD for the five inspections since 1992 is in excellent
/
L agreement with the EPRI POD. It is concluded that the POD applied for IPC leak and burst projections needs to be upgraded from the POD = 0.6 to a voltage dependent POD. This conclusion is further supported by the comparisons in Section
' 7 between projected and actual EOC-10 voltage distributions. The POPCD for the most recent five inspections strongly supports the EPRI POD, without further g adjustments for new indications, as an acceptable POD.
None of the eighteen 1993 RPC NDD indications left in service at BOC-10 were RPC confirmed in 1995. Even in the prior inspection, the RPC confirmation rate for RPC L indications left in service at BOC-9 was 0.0%. This result is much better than industry experience, which typically shows less than 25% RPC confirmation rates for
[ RPC NDD indications left in service. Based on these results, it is recommended that future Farley-2 IPC applications be based on including only 20% of the RPC NDD indications in the BOC voltage distribution used for EOC projections and leak / burst analyses.
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l 3.0 FARLEY PULLED TUBE DATA 3.1 FARLEY 21995 PULLED TUBE EXAMINATION RESULTS 3.1.1 Introduction During the EOC-10 outage in 1995, steam generator Tube R27C54 was removed from the hot leg side of S/G C at Farley Unit 2 in support of alternative repair criteria (ARC) applications. The subsequent examination was conducted at the Westinghouse Science and Technology Center to characterize tube corrosion at steam generator ho.
leg support plate crevice locations. The first, second and third support plate crevice regions (TSP 1, TSP 2 and TSP 3) and the free span (FS) regions associated with these I locations were available for examination. Only the TSP 1 region had original field l eddy current calls of OD origin indications.
After nondestructive laboratory examination by eddy current, ultrasonic testing, I radiography, dimensional characterization and visual examination, the TSP 1 region h was leak tested at elevated temperature. Subsequently, room temperature burst 5 testing was conducted on the three TSP regions. The three burst tested TSP l specimens were destructively examined using metallographic and SEM fractography I
l techniques to characterize any corrosion. In addition, an analysis of the OD deposits, OD oxide film, fracture face oxide film, and ID oxidt film was performed using EDS, EPMA, XRD, ESCA and AES techniques.
3.1.2 Non Destructive Examination (NDE) Results l
Table 3-1 presents a summary of the more important field and laboratory NDE B results. The eddy current data were reviewed, including reevaluation of the field
! data, to finalize the voltages assigned to the indications and to assess the field no detectable degradation (NDD) calls for detectability under laboratory analysis B conditions. A single analyst performed this work to minimiu data variability. Field j and laboratory eddy current inspections (bobbin and RPC probes) produced similar L data for most regions examined. For the called field indication at the TSP 1 location, there was little difference in the eddy current bobbin voltage call between the field and laboratory results. The field bobbin data for the two field NDD calls at TSP 2 and TSP 3 locations were reevaluated to derive the most appropriate amplitude measurements, where possible, for these very small signals. This review indicated that the TSP 3 field NDD call could be assigned a bobbin flaw voltage. This bobbin signal was reevaluated as a distorted indication where the selection of the flaw segment was aided by use of the 400 kHz data. The reevaluated field RPC data for these two NDD calls continued to be NDD with no discernible flaw separable from the background level. In the laboratory, the TSP 3 location was identified to have an RPC indication, but the presence of a dent caused by the tube pulling operation resulted in a bobbin distorted dent signal. (The dent distorted / obscured any potential bobbin signal although an indication was observed by the ';PC inspection.) In the SAAPC\apr95\APR90 DAY,3 3-1 w.ao..a.y up 19,19951128 am
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laboratory, no bobbin or RPC indication was detected at the TSP 2 location, although the presence of a tube pulling dent at the TSP 2 location would have obscured any potential bobbin signal. The dents at the TSP 2 and TSP 3 locations resulted from the tube pulling operation.
Negligible change in signal strength (voltage) was observed in the laboratory eddy g current inspections. Field bobbin probe signal strength for TSP 1 was 1.87 volts (1.86 5 volta after data reevaluation) while corresponding post-pull bobbin strength was 1.71 volts. Consequently, only minor tearing ofligaments between microcracks could have g occurred during the tube pull. m The radiographic and UT laboratory examination detected only a SAI at the TSP 1 region which was confined to within the crevice region.
g None of the field or a laboratory eddy current RPC or laboratory UT indications had any significant width in the data which would have suggested the possibility of intergranular cellular g corrosion (ICC) or three dimensional intergranular attack (IGA) in addition to and e in association with any axial cracking.
3.1.3 Leak Testing The TSP 1 crevice region, which had the original field eddy current indication, was leak tested at elevated temperature and pressure at conditions that ranged from a g simulated normal operating condition to that of a simulated steam line break condition. No leaks were observed. The maximum test differential pressure was 2609 psi with corresponding primary and secondary side temperatures of 626 and 617 F.
3.1.4 Burst Testing The three TSP crevice regions were burst tested at room temperature at a pressurization rate of 2000 psi per second. The burst tests were performed g simulat ng free span conditions with no TSP enveloping the indications. In addition, the field indication specimen (TSP 1) was tested using a bladder and foil for the burst test with a " semi-constraint" condition which simulated the lateral constraint 5
5 provided by the TSPs located below and above the crack indication. Results of the burst tests are presented in Table 3-2. All burst specimens developed axial burst g openings. The openings for the TSP crevice region specimens were centered within the crevice regions. The circumferential position of the burst opening in the TSP 1 specimen was the same as the location of the UT mdication. (The other specimens g did not have UT indications and the eddy current RPC data does not provide an absolute circumferential position.) The lowest burst pressure for the TSP crevice regions (TSP 1, the 1.86 volt indication) was 7,350 psi, 64% of the burst pressure of its free span equivalent and typical of a 0.875 inch diameter specimen with a 1.86 volt indication.
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Table 3-2 also provides room temperature tensile properties obtained from a FS l, section of the tube. The tensile strengths for the FS section are typical for Westinghouse tubing of this vintage.
l 3.1.5 Destructive Examination Results Post-burst test visual inspection data showed that corrosion cracks were present on
! all three TSP specimens. The three TSP specimens were subsequently given destructive examinations which ied.uded SEM fractography of the burst openings, SEM inspection of some surfe.ce features and metallography of secondary corrosion l within the crevice regions.
The burst fracture faces of these three TSP crevice region specimens were opened for l SEM fractographic examinations. Table 3 3 presents the results of the fractographic data in the form of macrocrack length versus depth, macrocrack length / average and I maximum depth; ductile or uncorroded ligaments were not found on the fracture face.
l The burst openings occurred in axial macrocracks that were composed of numerous I
I axially oriented intergranular microcracks of OD origin that were aligned in a tight and narrow axial band. While many ligaments separating the microcracks were present in all three specimens, no ligaments with ductile features were present. All I
i had intergranular features. The data of Table 3 3 indicate that the TSP regions from Farley Unit 2 did not have a typical number of remaining uncorroded ligaments between microcracks comprising the burst macrocracks.
Allintergranular corrosion was confined to and located in the central to upper portion I of the crevice regions. The burst opening macrocracks for the TSP crevice regions I
l had maximum depths ranging from 34% to 92% throughwall, with average depths ranging from 20% to 50% throughwall and with macrocrack lengths ranging from 0.250 to 0.500 inch.
Two TSP regions were initially called bobbin NDD in the field, one of which was l subsequently found by reevaluation of the field data to have a small (0.31 volts)
I indication prior to the tube exam. The maximum crack depths for these two locations were 36% and 34% for the TSP 2 and the TSP 3 regions, respectively. Both had average macrocrack depths of 20%.
Figures 3-1 to 3-3 present sketches of the crack distributions found by visual (30X stereoscope) examinations and by subsequent metallographic examinations. The sketches show the locations where cracks were found and their overall appearance, not the exact number of cracks or their detailed morphology. All TSP regions had their corrosion located within and confined to the crevice regions. Note that a number of long axial crack networks were observed at several crevice locations on both TSP 2 and TSP 3, in addition to the burst fracture crack network. These axial networks are discussed below.
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Due to the complexities of the crack networks observed in some of the TSP regions, radial metallography was utilized, in addition to transverse metallography and SEM inspection of local surface features, to provide an overall understanding of the g intergranular corrosion morphology for the TSP regions. In radial metallography, a small sections of the tube (typically 0.5 by 0.5 inch) are flattened, mounted with the OD surface facing upwards and then progressively ground, polished, etched and g viewed from the OD surface towards the ID surface. Table 3-4 provides a summary 5 of the metallographic data.
From the metallographic and SEM surface examinations conducted on the TSP regions, it was concluded that the dominant OD origin corrosion morphology was axial intergranular stress corrosion cracking (IGSCC). In addition, especially for the g TSP 2 and TSP 3 regions, there were regions with oblique angles corrosion. These 5 oblique angled cracks were frequently associated with the long axial crack networks sketched in Figures 3 2 and 3-3. Some tended to form " railroad track" structures and g these networks were more complex than the simple axial macrocracks that formed 5 the burst opening of all the TSP regions. More than a dozen axial networks were observed, some more complex than others, and all were shallow compared to the burst opening corrosion. Due to their limited (narrow) area and overall axial directionality of these " railroad track" networks, the oblique angled corrosion is not defined as intergranular cellular corrosion (ICC), which is frequently found in association with E the axial IGSCC. With an ICC morphology, a complex mixture of short axial and W oblique angled cracks interact to form cell like structures where the structures occur randomly in patches without a pronounced direction. Also, note that at least five of g these long axial crack networks, but with less complexity (i.e., with only slight a
" railroad track" characteristics), were associated with deposit covered axial scratches.
Four of these and all of the more significant ones were observed at the TSP 3 location E where the scratches continued for long distances above and below the crevice region, E but the intergranular corrosion was confined to surface locations within the crevice region. The corrosion associated with these axial scratches was not deeper than the
" railroad track" corrosion that occurred without the presence of surface scratches. g IGSCC morphology can be characterized by DAV ratios where the extent of IGA g associated with a given crack is measured by the ratio of crack depth to the width of 5 the crack at its mid-depth. DAV ratios greater than 20 are defined as minor and ratios less than 3 are defined as significant. Crack density is also considered an important parameter in characterizing corrosion Crack densities greater than 100 g
cracks in 360 degrees are defined as high while values less than 25 are defined as low. The OD origin axial intergranular corrosion observed in TSP crevice regions of the tubes varied moderately in crack density and to a lesser extent with crack morphology. The crack density ranged from low (TSP 1 corrosion) to moderate (TSP 2 corrosion) while the crack morphology ranged from moderate to slightly significant, as measured by DAV ratios, with the smaller DAV ratios (defined as significant) being g-associated with the more shallow cracks. (As shallow cracks became deeper, they tended to develop more moderate DAV ratios.) Table 3-4 presents this data.
s ___ m . _ .., m ,,. _ _
g I
R Specimen TSP 2 had the largest number of cracks (an estimated 50 cracks over the tube circumference) with most of these cracks occurring in several narrow axial zones with complex crack structures, while the TSP 1 specimen basically had only the burst I macrocrack structure with one small (4 degree wide) zone with shallow intergranular corrosion. ,
3.1.6 Conclusions I The TSP crevice regions of Tube R27C54 had corrosion present. Metallographic and SEM fractographic data showed that the corroded TSP crevice regions primarily had axially oriented OD origin IGSCC. The axial macrocracks associated with the burst l test openings were typical and simple axial macrocracks, but with no ductile
, ligaments present between the individual microcracks. At other locations, when oblique angled intergranular corrosion was present, it was primarily associated with !
E more shallow but also more complex axial corrosion patterns. These patterns 5 frequently appeared with " railroad track" formations. In addition, some of the axial cracking patterns were associated with shallow, pre-operational axial scratches that extended through and beyond the TSPs. All corrosion was confined to the crevice )
i regions, even when the pre-operational scratches extended beyond the crevice regions.
The overall corrosion morphology, while typical of pulled tubes within the EPRI 13 database, tended not to have regions with intergranular cellular corrosion (ICC),
5 which has been an important feature of TSP corrosion in most recent tube j examinations. The " railroad track" corrosion patterns are also an infrequent J observation, but they are considered a curiosity and not a new concern. They may i B be related to the presence of unusual surface residual stresses. The observed corrosion most likely resulted from a past mildly alkaline and somewhat oxidizing crevice environment, even though the data suggest that more recent crevice I environments are neutral to slightly acidic.
Eddy current bobbin and RPC probe data correlated well with corrosion distribution I for the only deep crack found, that from the TSP 1 region. Two TSP crevice regions .
(TSP 2 and TSP 3) were initially called bobbin NDD in the field and subsequently one (TSP 3) was found by reevaluation of the field data to have a small (0.31 volts) indication prior to the tube exam. These regions had corrosion ranging from 34% to 36% throughwall, maximum depth. Consequently, these locations had corrosion near I the eddy current detection threshold. These two locations also served in determining the UT detection threshold, as neither TSP 2 or TSP 3 corrosion was detected by UT, only the deep axial crack in the TSP 1 region was detected. The maximum corrosion depth not called was 36%.
Leak rate testing performed at elevated temperatures and pressures simulating normal operating and steam line break conditions produced no leakage for the TSP 1 I region specimen. The field bobbin probe signal strength for this specimen was 1.86 volts. The TSP crevice region burst pressures ranged from 7,350 to 11,190 psi. All burst pressures were above safety guidelines required by R.G.1.121 including the
- ' * " ' " - " " ~ ~~""~""-
I I
O C
1.86 volt indication at TSP 1 region. The burst tests were performed simulating free span conditions with no TSP enveloping the indications. The leak and burst pressure data were consistent with expectations and near mean predictions for the ARC burst a
pressure versus bobbin voltage correlation. W 3.2 FARLEY-2 PULLED TUBE EVALUATION FOR ARC APPLICATIONS The pulled tube examination results were evaluated for application to the EPRI database for ARC applications. The eddy current data were reviewed, including 3 reevaluation of the field data, to finalize the voltages assigned to the indications and E to assess the field NDD calls for detectability under laboratory conditions. The data for incorporation into the EPRI database were then defined and reviewed against the g EPRI outlier criteria to provide acceptability for the database. 5 3.2.1 Eddy Current Data Review Table 3-5 provides a summary of the eddy current data evaluations for the Farley-2 pulled tubes. These NDE data results have been discussed in the above Section 3.1.2. g As noted above, the field and laboratory reevaluations of the field bobbin data are in 5 good agreement for the field call at R27C54, TSP 1. The laboratory reevaluation identified a small indication of 0.31 volt at TSP 3 that was not called in the field, g while both evaluations were NDD at TSP 2. The reevaluated bobbin voltages, 5 including the adjustment for cross calibration of the field ASME standard to the laboratory standard, are used for the EPRI ARC database. The reevaluation was E performed by the same analyst that performed a large part of the EPRI database and W the use of these voltages minimizes analyst variability in the database, which is separately accounted for in ARC applications as an NDE uncertainty.
g 3.2.2 Farley-2 Data for ARC Applications The pulled tube leak test, burst test and destructive examination results are summarized in Table 3-6. The largest indication at TSP 1 was leak tested and no leakage was found even at SLB conditions. It can be inferred from the maximum g depths of 36% and 34% and TSP 2 and TSP 3 that these indications would not have W leaked if they had been leak tested. The measured burst pressures are adjusted to the reference 150 ksi for the sum of the yield plus ultimate tensile strengths. An axial tensile test to rupture in support of the tube expansion APC was not performed for these indications at the TSP intersections since the indications do not have significant cellular corrosion and any axial teat would result in high tensile loads.
The data of Table.3-6 should be used in EPRI ARC burst pressure and SLB g probability ofleakage correlations.
The Farley-2 pulled tube results were evaluated against the EPRI data exclusion criteria for potential exclusions from the database. Criteria la to le apply primarily to unacceptable voltage, burst or leak rate measurements and indications without s _.- se .. ., _ ,, _
g I
l B leak test measurements. None of these criteria are applicable to the Farley-2 indications. Criterion 3 applies to potential errors in the leakage measurements and is not applicable to the Farley-2 indications with no leakage.
l EPRI Criterion 2a applies to atypical ligament morphology for indicationt ving high burst pressures relative to the burst / voltage correlation and states t'.. At high burst pressure indications with 5 2 uncorroded ligaments in shallow cracks < 60%
deep shall be excluded from the database. Table 3-6 identifies the number of I remaining ligaments and the maximum depths for the indications. None of the three indications had remaining ligaments and the indications at TSPs 2 and 3 are < 60%
deep, although the TSP 2 indication was NDD and would not be included in the I database. The 0.31 volt indication at TSP 3 satisfies the EPRI data exclusion Criterion 2a and is also high on the burst / voltage correlation. Therefore, the indication on R27C54, TSP 3 is excluded from the EPRI ARC database due to I exclusion Criterion 2a. Overall, the crack morphology and corrosion of the pulled tube were consistent with and did not affect the IPC/APC database.
3.3 COMPARISON OF FARLEY-2 DATA WITH EXISTING IPC CORRELATIONS The purpose of this section is to report on evaluations performed which utilized the I results of leak rate and burst testing of tube sections which were removed from Farley Unit 2 in the Spring of 1995. The Farley 2 pulled tube data for ARC applications is given in Tables 3-6 and 3-7. Destructive examinations to obtain data for ODSCC IPC applications were as follows:
(1) Burst Testing - Two (2) tube sections, which had indications exhibiting bobbin I
i' amplitudes greater than zero volts, based on the field inspection data, were tested to determine their burst pressures.
(2) Probability of Leak (pol) Testing - One (1) of the specimens was tested to evaluate its probability ofleak. The other specimen was estimated to have a pol of zero based on the results of the metallurgical examination.
I (3) Leak Rate Testing - No leak rate testing was performed since both specimens exhibited a pol of zero.
I Destructive examination of the cracks after the testing revealed that one of the specimens was not consistent with the EPRI acceptance criteria for inclusion of the results into the reference database. Accordingly, only the data from one of the l specimens' test results were retained for further consideration. The outcomes of the tests for the remaining specimens, see Table 3-7, were compared to the EPRI data-base of similar test results for 7/8" outside diameter steam generator tubes. In addition, the effect of including the new test data in the reference database was evaluated. In summary, the test data are consistent with the database relative to the burst pressures, the probability ofleak, and the leak rate as a function of the bobbin g - . - - ~ . . . , _ ~
I
f3 -
C amplitude. The results of these comparisons and evaluations are discussed in what follows.
3.3.1 Burst Pressure vs. Bobbin Amplitude The result from one (1) burst test, performed on one of the tube specimens which exhibited a non-zero bobbin amplitud6 at a location corresponding to the in-plant elevation of a tube support plate, was considered for evaluation. A plot of the burst pressures of the Farley 2 specimen is depicted on Figure 3-4 relative to the correlation developed for the reference database.2 It was verified that the measured burst pressure falls within the scatterband of the reference data about the reference regression line, thus, no significant departure from the reference database is indicated. Although not shown, the data point falls well within the two-sided 90%
prediction band about the regression line, thus, no statistically significant anomaly is indicated.
Since the Farley 2 burst pressure data was not indicated to be from a separate population from the reference data, the regression analysis of the burst pressure on g the common logarithm of the bobbin amplitude was repeated with the additional data g included. A comparison of the regression results obtained by including those data in the regression analysis is provided in Table 3-8. Regression predictions obtained by g including these data in the regression analysis are also shown on Figure 3-4. The 5 affect on the regression parameters is as follows:
- 1. The intercept of the burst pressure, P,, as a linear function of the common logarithm of the bobbin amplitude regression line is decreased by 0.1%.
- 2. The slope is increased by less than 0.1%, i.e., the slope with the Farley 2 data is a smaller negative number.
- 3. The standard error of the residuals is decreased by 0.5%. The effect of this change would be reflected in a slightly smaller deviation of the 95% prediction line from the regression line.
l The effect on the predicted structural integrity of the SG tubes is as follows:
- 1. There is no significant change in the SLB structural limit. l
- 2. Since the intercept is decreased and the slope increased by the inclusion of the Farley 2 data point, predicted burst pressures for indications up to about 20 3
3 volts would be slightly less than the value obtained using the reference regression line. This will lead to a slight increase of the predicted. probability 3 of burst for indications in this range. 5I 1
The database is not shown since it is proprietary to the Electric Power Research Institute.
S \APC\APR95\ArR90 DAY.33 3-8 o m v9s I
5
- 3. The decrease in the standard error of the residuals will slightly decrease the predicted probability of burst for bobbin indications over most of the structural
. range ofinterest.
Based on the insignificant change in the structural limit, the change in the probability of burst would also likely not be significant. It is noted that for high l voltages, e.g., near the SLB structural limit, the effect of the lower intercept and increased slope is likely offset by the smaller standard error and the probability of burst would not significantly change.
I 3.3.2 Probability of Leak The same data point examined relative to the burst pressure correlation 'vas also examined relative to the reference correlation for the pol as a function of the common logarithm of the bobbin amplitude. Figure 3-5 illustrates the Farley 2 data l point (the solid symbol) relative to the reference correlation. The specimen exhibited pol behavior commensurate with expectations indicated by the reference regression curve. Based on the visual examination, there appears to be no significant evidence of irregular results, i.e., outlying behavior is not indicated.
In order to assess the effect of the new data on the correlation curve, the database l was expanded to include the Farley 2 data and a Generalized LinearModel regression of the Pot on the common logarithm of the bobbin amplitude was repeated. A comparison of the correlation parameters with those for the reference database is l shown in Table 3-9. These results indicate:
- 1. A 0.3% reduction in the logistic intercept parameter (larger negative number)
I 2. A 0.3% increase in the logistic slope parameter.
- 3. The values of the parameter variance-covariance matrix changed by 0.4% to l 0.5%.
- 4. The Pearson standard error decreased by 0.1% from 0.622 to 0.621. This is a l
negative indicator since the ideal value would be 1.0. However, the magnitude of the change is not significant.
I In order to assess whether or not these changes are significant, the reference correlation and the new correlation were also plotted on Figure 3-5 (the reference l correlation is shown as a dashed line and the new correlation as a solid line). An examination of Figure 3 5 reveals essentially no change in the correlation, thus, the Farley 2 data are consistent with the reference database. It is noted that when the total leah rate is determined using the leak rate to bobbin volts correlation, the resulting value can be quite insensitive to the form of the pol function. Hence, the effect of the changes in the parameter values and variances is judged to be l insignificant relative to the calculation of the expected totalleak rate.
I - - - " 34 -
I
[]
O 3.3.3 Leak Rate vs. Bobbin Amplitude None of the indications exhibited any leakage, hence the reference correlation ofleak B rate to voltage is unaffected. Since the reference correlation ofleak rate to voltage W exhibits a p-value of 6.5% for the slope parameter, the use of the correlation in performing Monte Carlo simulations to estimate the totalleak rate is not considered g to be justified, based on the requirements stipulated in the draft Generic Letter for 5,l voltage based plugging criteria. l 3.3.4 General Conclusions The evaluation of the affect of the Farley 2 data indicates that the burst pressure, the 3l probability ofleak, and the leak rate correlations to the common logarithm of the 5; bobbin amplitude would not be significantly changed by the inclusion of the data.
Therefore, the conclusions relative to EOC probability of burst and EOC totalleak E rate based on correlations obtained using the reference database would not be signifi- 5 cantly affected by repeating those analyses using an expanded database which includes the Farley 2 test data.
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I SAAPCNAPR35\APR90 DAY.33 3-10 07eistes I
ea ma emeee emW W M 'm W W mW Table 3-1 Comparison of NDE Indications Observed at Farley Unit 2 on S/G Tube R27C54 location Field EC 12b FlC ** lab Ur Data i.ab X-Ray f TSPI Bobbin 1.87V OD Ind, (1.86V,71% Bobbm: 1.71V OD Ind,72% deep 0.465" long SAI, 75% deep, 0.5" long SAI composed of at deep)* E: 036" sal,1.19V at 0* location least 3 microcracks E: 1.21 V SAI TSP 2 Bobbm: NDD Bobbm: NDD,4.5V dent at TSP top location NDD NDD l RID NDD E: NDD TSP 3 Bobbin: NDD (031V DI)* Bobbm: Distorted dent signal at center of TSP, NDD NDD E: NDD 14.5V dent at top of TSP & 10.7V dent at bottom of1EP E: 0.25" SAI in noisy data
( )* = Eddy current n: evaluation value using cross calibration of ASME standant to irference lab standani.
- Dents at TSP 2 and TEP3 locations resulted from tube-pull.
Ireend of Ablueviations:
Ind = Indication NDD = no detectable degradation SAI = single axial indication 1EP = tube support plate RPC = Rotating Pancake Coil V = volts l
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i Table 3-2 Room Temperature Burst and Tensile Test Data for Farley Unit 2 S/G Tube R27C54 location Durst Presstre, Durst Durst length, Durst Wkltts 0.2%OtTset Tensile Tensile Ultinne Tensile Elongatxri, psig Ductility, % inches inches Yield Strength, psi Strengtit psi % '
13Pl* 7,350 9.0 1.195 0335 TSP 2 10,910 213 1358 0398 i
TSP 3 11.190 22.2 1.517 0.446 l
FE 4.6" to 15.4" above 'ISPI IIJJD 23.7 1.968 0395 l FS,18.4" to 29.4" above TSPI $4,900 103,800 25.1 Camrol. NX8161 !!.470 31.8 1.950 0370 52,300 101.500 18.5+
LEGEND TSP = tube support plate; FS = free span; S/G = steam generator
- = Burst with foil and bladder in a semi-restraint condition, all others burst without restraint, bladder, or foil.
+ = The standard tensile specimen has a gage length at the center of the siu.imen. For we of the ductility measurement, the failure should occur within the gage length.
l l I
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- _ _ -- __ ____x _ _ _ _ _ .--.w_ _n.._- - - _ - -_ . - . . _ ____ - .- -- _
W W W W W W W W W W W W W W W W W. W '91 Table 3-3 (Page 1 of 2)
Farley Unit 2 S/G Tube R27C54 Burst Opening Macrocrack Profiles Specimen location length vs. Depth & Ductile Ligament Data Positional Information Comments (inches &.througimall)
TSPI 0.0W00 Crack Top (located 0.04" The axially onented burst 0.05/42 belowTSP top) irsuvuack had no ductile 0.1W42 thpu a 6 with dmple 0.15/50 rupture features occurring 0.2W46 over more than 50% of 0.25/62 theirlength.
0.3074 035l88 (037B2) glix. depth = 92%)
0.4W88 0.45/58 0.5W00 Crack Bottorn (Ave. depth = 50% hwa length = 0.500 inch) a S:\APC\APR95\APR90 DAY.33 3-13
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Table 3-3 (Page 2 of 2)
Farley Unit 2 S/G Tube R27C54 Burst Opening Macrocrack Profiles Spedmen Length vs. Depth & Ductile LJgament Data PositionalInfonmtion Cu m a6 Location (inches /% throughwall)
TSP 2 0.0000 Crack Top (located 0.056" 'Ihe axially onented txrst 0.05/24 below TSP top) nwuuack had no ductile 0.10/20 livaia 6 with dir@le rupture 0.15/25 features occuning over rnare 0.20/28 than 50% of their length.
(0.22!36) <-(Pkx. depth = 36%)
0.25/29 0.30/24 0.35/12 (0.376/00) Crack Bottom (Ave. depth = 20%, Macrocrack Length = 0.376 inch)
TSP 3 0.0000 Crad Top (located 0.03" The axially onented burst 0.05/26 belowTSP top) nwectack had no ductile 0.1 &32 ligara6 with dimple rupture (0.13/34) <-(Max. depth = 34%) features occurring mer nue 0.15/32 than 50% ofits length.
0.2728 0.2500 Crack Bottom (Ave. depth = 20%, Macrocrs& Length = 0.250 inch)
S.MPCMPR95MPR90 DAY.33 3-14 07tizes 3 3 3 M M M S W W .E E E E E E E
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M M M M M M M W M M M M M M M MM M M Table 3-4 Metallographic Data for Farley Unit 2 S/G Tube R27C54 l
Specirrea Section Type Nanter Secbon Cracks per Estinuted Max. Max 1 Ave. Max. Depth of Axial and Ave. DMI Location of Length inch Number of Depth (% Oblique Cuiraents(%
Ratio from Cracks (inch) Cracks at Md- throughwall) throughwallin Radial Section) Transverse Crevice Section TSP 1 Transverse 5 2.1 2 7 24/14 no significant oblique cracks 8 Trmsverse 6 2.1 3 50 20/15 10%< Axial >20% 6 TSP 2 Radial 1a 20 0.36 56 (95)+ depth = 4% 10%<Chique*>20%
Radial 1b 8-9 0.36 24 (47)+ depth = 10%
Radial ic 0 0.36 0 depth = 20%
Radial 2a 3 0.22 14 (250)+ depth = 4%
Radial 2b 4 0.22 18 (118)+ depth = 10%
Radial 2c 1-2 0.22 7 (39)+ depth = 20%
TSP 3 Transverse 1 3 2.0 1.5 15 12/8 10%< Axial >20% 2 Transverse 2 7 0.38 13 14/9 10%<Obfque*>20%
Radial 1a 8 0.43 19 (37)+ depth = 4%
Radial 1b 34 0.43 8 (18)+ depth = 10%
Radial ic 0 0.43 ,O depth = 20%
- = Oblique cracks occuned primarily in association with long axial networks of " railroad track" corrosion up to 0.03 inch wide.
+ = The value in p& enti6s is the cracks per inch within the corrosion banci The first value is the cracks / inch over the width of the metallographic sanple.
S.\APCMPR95MPR90 DAY.33 3-15 O M U95
_ _ - _ _ _ _ . - - . _ _ - - _ - - _ - ~ _ - - - . - - _ . - . - - - - - - - - - - - - . - - - - - - - - - - - - - - - - - - - - J
l Table 3-5. Sununary of Farley-2 Pulled Tube Eddy Current Results l
TSP Field Call Lab. Reevaluation of Field Data Post Pull Data Bobbin RPC Bobbin ASME Bobbin Depth RPC Bobbin RPC UT Volts
- Volts Volts Cal.* Volts
- Volts Volts Volts R27C54 1 1.87 1.21 1.85 1.007 1.86 72% 1.2 1.71 1.19 SAI 2 NDD NDD NDD NDD NDD NDD NDD Dent 3 NDD NDD 0.31 1.007 0.31 DI ND9 DI SAI NDD Dent Noisy Notes: 1. Field data include cross calibration of ASME standard to the reference laboratory standard
- 2. ASME calibration represents the cross calibration factor for the field ASME standard to the reference laboratory standard and is applied to the laboratory reevaluation to obtain the corrected APC volts S;\AFCNAPR95\APR90 DAY.33 3-16 omas em W W W W W W W W W W W W m M M M SB
g ammmmeeammmeM M W W .M M Table 3-6. Farley-2 Pulled Tube Data for ARC Applications T Bobbin Data Destructive Exam Results Leak Rate-1/hr Burst Pressure Data - ksi Tube S RPC g Volts Max. Avg. Crack No. N. O. SLB Meas. o, Adj.
c4 Volts Depth Depth Depth Length Lig.* 1300 2560 Burst Burst psid psid Press. Press.
R27C54 1 1.86 72% 1.2 92% 50% 0.500" 0 0.0 0.0 7.350 6.947 2 NDD NDD 36% 20% 0.376" 0 0.0* 0.0* 10.910 10.312 3 0.31 DI NDD 34% 20 % 0.250" 0 0.0* 0.0* 11.190 10.637 Note 4 Note 4 Note 4 Note 4 FS 11.500 54.9 103.8 10.932 Notes:
- 1. FS is freespan section of tubing with no tube degradation to obtain tensile properties and undegraded tubing burst pressure
- 2. Number of uncorroded ligaments with > 50% ofligament length remaining in burst crack face.
- 3. Inferred from destructive exam depth, leak test not performed. Corrosion depth too shallow for leakage at SLB conditions.
- 4. Data point excluded from ARC database based on EPRI data exclusion Criterion 2a - cracks having $ 2 uncorroded ligaments in shallow cracks < 60% maximum depth are excluded from the database due to atypical high voltages when the burst pressure is high on the burst pressure / voltage correlation S:\APCNAPR95\APR90 DAY.33 3-17 07/12/95
i l
l l
Table 3-7: Results of Destructive Examinations, and Leak Rate and Burst Pressure Testing of Tube Sections Removed from Farley 2 for Expansion of the EPRI ODSCC Database Specimen Bobbin Burst Pressure Probability of Leak Rate ID Amplitude for q = 75 ksi Leak During During SLB (Volts) (ksi) SLB (lph)
R27C054-1 1.86 6.947 0 R27C054-2 NDD 10.3125 R27C054-3 0.31 10.637
- Om Notes (1) NDD tube results are not used to expand the El-RI database.
(2) Excluded for database per EPRI criterion 2a.
SM *CMPR95MPR90 DAY.33 3-18 omass 4
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Table 3-8: Effects of the Farley Unit 2 Data on the I Burst Pressure vs. Bobbin Volts Correlation ("
P, = g + g log (Volts)
Parameter Reference Database Database with Value c2> Farley 2 l
% 8.295 8.286
% -2.568 -2.566
%,,,, 0.888 0.885 N (data pairs) 76 77 p Value for % 5 10 310 a.
r' 82.8% 82.7 %
Notes: (1) The reference flow stress for the i determination of the parameters of the correlation equation was 75.0 ksi.
(2) The reference database includes the I results of data obtained from tubes removed from Beaver Valley Unit 1 in the Spring of 1995.
I I
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I Table 3-9: Effect of Farley Unit 2 Data on the Probability of Leak Correlation Pr(Leah) = f1 + e -lE
- A' ""'**'d Parameter Reference Database Database with Value ") Farley 2 l
Q -6.905 .G.928 Q 8.359 8.383 V, ,
- 3.484 3.466 V,2 -3.828 -3.811 V22 4.563 4.547 DoF() ,
103 104 Deviance 25.1 25.1 g i Pearson c% 0.62 0.62 Notes: (1) The reference database includes the results of data obtained from tubes g
removed from Beaver Valley Unit 1 in the Spring of 1995.
(2) Parameters Ve are elements of the covariance matrix of the coefficients, R, of the above regression equation.
(3) Degrees of Freedom g I
I! !
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Il ,
SNUT\APR95\APR90 DAY.33 3-20 07/13/9s ,
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um m as eee mW W un m mmmm m m M W I
I I l l
l SP Top 1
('
i R a j O
C e /
tu SP Bottom i
I I I 180* 270* 0* 90* 180'
'f
- Circumferential Position (degrees)
Figure 3-1 Sketch of the OD surface crack distribution found at the first tube support plate (TSPI) crevice region of Tube R27C54.
Also shown is the location of the burst fractum opening. The burst opening extended beyond the TSP crevice region, but the corrosion cracking on the burst fracture was confined to the crevice mgion.
1 I I j
~
P
/"' 'll'% 1 ji i I
\
i I i i ( ,
\ l, o a i T g
$ I 1 l ill k g
- SP Bottom e
ill I I I w
$ O' 90* 180* 270* 360*
Circumferential Position (degrees)
Figure 3-2 Sketch of the OD surface crack distribution found at the second tube support plate (TSP 2) crevice region of Tube R27C54. Also shown is the location of the burst fracture opening. The burst opening extended beyond the TSP crevice region, but the corrosion cracking on the burst fracture was confined to the crevice region.
4 I I -1
-1 SP Top )
g i 1, j I{i: g ,
e f ' .
t '
(
D o h
)
t b' lt !
h sm ii I"8
. i l' t :
j in 'h t' ii fl l ,
I i
- SP Bottom I I I y 0* 90* 180* 270* 360*
O Circumferential Position (degrees)
Figure 3-3 Sketch of the OD surface crack distribution found at the third tube support plate (TSP 3) crevice region of Tube R27C54. Also shown is the location of the burst fracture opening. The burst opening extended beyond the TSP crevice region, but the corrosion cracking on the burst fracture was confined to the crevice region.
m___.._____ ____ _ m____ _ . - _ . _ _ m_ _ m _
Figure 3-4 Burst Pressure vs Volts for 7/8" OD Alloy 600 SG Tubes EPRI/NRC Database, Reference or = 68.8 ksi @ 650 F 12.0 EPRI Database a Farley 2 Data 10.0 m LS EPRUNRC N g + LS w/Farley 2 N s --- 95% Prediction @ LTL N ---- SLB Structural Limit
@ 8.0 '~
'- N ---- SLB Limit d$
o
~' \
E N
@ 6.0 N
o '~. . y g
A x
4'0 '
3.657 ksi j
-------- - .- - -------- --- L -~-- -- -l - N N ' s.
i s.
2_5gn y,; . .-. .-. .. ......... .-...... ..-....... ...... .. .... ... . . . . - . ' .. . .y 2.0 '"'--
l h 9.0 V 28.7 V 0.0 '
O.1 1. 10. 100.
Bobbin Amplitude (Volts)
S:\ APC\APR95\APR90 DAY.33 3-24 07/19/9s M M M M M M M M M M M M M M M M M M U
_. _ _ 1 Figure 3-5 Probability of Leak for 7/8" SG Tubes Effect ofInclusion of Farley 2 Data-1.0 g y-f 0.9 --
EPRUNRC Database a New Farley 2 Data 0.8 --
. . . POL EPRUNRC Data 3 w/Farley 2 Data /
l (n 0.7 j n
Q D 0.6 }[
Y f j 0.5 }
b 0.4 5
~E
.g 0.3 ,
d:
0.2 0.1 /
/
/
0.0 --
/
0.01 0.1 1.0 10.0 100.0 Bobbin Amplitude (Volts)
S;\APC\APR95\APR90DAYm 3-25 omses
lt g 4.0 EOC-10 INSPECTION RESULTS AND VOLTAGE GROWTH RATES 4.1 EOC-10 INSPECTION RESULTS
, In accordance with the IPC guidance provided by the NRC draft generic letter (Reference 10.2), the end of Cycle 10 inspection of the Farley Unit 2 steam generators (SG) consisted of a complete,100% bobbin probe full length examination of all TSP intersections in the tube bundles of the three SGs. During this outage, tubes I previously plugged in accordance with prior repair criteria for ODSCC at TSPs were deplugged, inspected, and either returned to service in accordance with IPC criteria I or replugged. Tube R27C54 in SG C was pulled for inspection, as reported in Section 3 of this report.
RPC examination was performed for potential indications (PI) >1.5 V bobbin coil amplitude in SG A and B, and >1.0 V in SG C. RPC testing confirmed 46 of 58 hot leg intersection PIs, with the majority associated with deplugged tubes. In the RPC j
I augmented inspection of 35 dented intersections >5 V and of 105 intersections with residual signals, the RPC analysis reported no degradation. Only one RPC confirmed I indication with >2.0 bobbin volts was found and was plugged. TSP PIs with 52 V bobbin could remain in service even if confirmed by RPC test. No indications at TSPs were identified that had cracks extending outside the TSPs by either the bobbin or RPC inspections. In addition, no abnormal indications such as circumferentially oriented indications or PWSCC at TSP locations were found in the 1995 inspection.
A summary of ECT indication distributions for all three steam generators is shown on Table 4-1 and Table 4-2. For those tubes that were in service during Cycle 10, Table 4-1 provides the number of field bobbin indications, the number of these field I bobbin indications that were RPC inspected, the number of RPC confirmed indications, the number of plugged indications, the number of Cycle 10 in-service I indications that remain active for Cycle 11, the number of deplugged tubes returned to service for Cycle 11 and the total indication population being returned to service for Cycle 11 (BOC-11). Overall, the combined data for all three steam generators of l Farley Unit-2 shows that:
Out of a total of 198 indications which were in service for Cycle 10 and were identified during the EOC-10 inspection, a total of 196 of these indications were returned to service for Cycle 11.
Of the 198 indications, a total of 35 were RPC inspected.
,I I "--- 4-' - " -
I
O O
Of the 35 RPC inspected, a total of 17 were RPC confirmed. All 17 were >1.0 V and one was >2.0 V.
+
A total of 111 indications, out of a total of 125 indications, in tubes deplugged at EOC-10 were returned to service for Cycle 11, for a total of 307 indications g returned to service for Cycle 11 in accordance with IPC criteria. 3 Review of Tables 41 and 4 2 indicates that steam generator C has more total as well g as higher amplitude BOC-11 indications (a quantity of 97, with 28 indications >1.0 V W and one indications >2.0 V, that were in service for Cycle 10, ni addition to a quantity of 89, with 55 indications >1.0 V and none >2.0 V, that were deplugged at EOC-10 g and are being returned to service, for a total of 180 indications for BOC-11) than SG A or B, thereby it potentially will be the limiting SG at EOC-11.
Figure 41 shows the actual bobbin voltage distribution determined from the EOC-10 ECT inspection; note that SG C predominates above 0.5 V. The largest bobbin g indication found in the EOC-10 inspection was 2.5 volts. Figure 4-2 shows the bobbin 3 voltage distribution for the deplugged indications which were returned to service for Cycle 11. Figures 4-3 show the totalindications which are being returned to service for Cycle 11. Figure 4-4 shows the repaired population distribution for those in-service EOC-10 indications which were plugged.
The distribution of EOC-10 indications as a function of support plate elevation, I summarized in Table 4-3 and shown on Figure 4-5, shows the predisposition of ODSCC to occur in the first few hot leg TSPs (115 of 197 indications occurred in the first two hot leg TSPs), although the mechanism does extend to higher TSPs. There l
are 12 bobbin indications reported in the cold leg. This distribution indicates the predominant temperature dependence of ODSCC at Farley Unit 2, similar to that 5
E observed at other plants.
4.2 VOLTAGE GROWTH RATES Average growth rates for the Farley Unit 2 steam generators, shown on Table 4-4, provide a comparison of six operating cycles (1986-1987,1987-1989,1989-1990, and 1990-1992, 1992-1993, 1993 1995). These results show a continuous reduction in g average growth rates from Cycle 6 (1989) to Cycle 10. 3 Average growth rates in each SG for Cycle 10 (1993 - 1995) are shown in Table 4-5.
SG C has the largest number ofindications and the highest average voltage at BOC-E u
- 10. There is no definitive distinction between the SGs for the largest average voltage growth during Cycle 10; the average growth rates for all SGs during Cycle 10 are low, g S \APc\sla95\ArR90 DAY.4 4-2 07/2495,19:06 I
I varying between zero (the negative growths result from uncertainties in the difference between small numbers) and 5%.
The cumulative probability distribution function, another indicator of relative growth, is summarized on Table 4-6 for Cycles 9 and 10; the same data is shown on Figure l 4-6, where the Cycle 9 growth rate clearly exceeds that of Cycle 10. Cycle 9 has both larger average and maximum growth rates than Cycle 10 and is used herein as the basis for Cycle 11 bobbin population prediction. The NRC draft generic letter I recommends that the more conservative growth distribution from the last two cycles be used for projecting EOC distributions and that the growth distribution for IPC I analyses be based on at least 200 indications. The 172 Cycle 9 and 197 Cycle 10 indications are sufficiently close to 200 to be acceptable and are used for the IPC analyses. Using the Cycle 9 growth distributions is more conservative than using the combined Cycle 9 and 10 distributions.
l 4.3 PROBABILITY OF PRIOR CYCLE DETECTION (POPCD)
The inspection results at EOC-10 permit an evaluation of the probability of detection I at the prior EOC-9 inspection. For APC/IPC applications, the important indications are those that could significantly contribute to EOC leakage or burst probability.
These significant indications can be expected to be detected by bobbin and confirmed I by RPC inspection. Thus the population ofinterest for APC POD assessments is the EOC RPC confirmed indications that were detected or not detected at the prior inspection. The probability of prior cycle detection (POPCD) can then be defined as:
EOC-10 RPC Confirmed and Detected at EOC-9 +
I POPCD(EOC-9) =
EOC-9 RPC Confirmed and Plugged at EOC-9 Numerator + New EOC-10 RPC Confirmed 1
Indications (i.e., not detected at EOC-9)
POPCD is evaluated at the 1993 EOC-9 voltage values (from 1995 reevaluation for i growth rate) since it is a EOC-9 POPCD assessment. The indications at EOC-9 that I were RPC confirmed and plugged are included as it can be expected that these indications would also have been detected and confirmed at EOC-10. It is also l
I appropriate to include the plugged tubes for APC applications since POD adjustments to define the BOC distribution are applied prior to reduction of the EOC indication distribution for plugged tubes.
I It is noted that the above POPCD definition includes all new EOC-10 indications not reported in the EOC-9 inspection. The new indications include EOC-9 indications present at detectable levels but not reported, indications present at EOC-9 below l
g s urcs.t 9ssira90niv 4 4-3 o2,24w is;is I 1
O O
detectable levels and indications that initiated during Cycle 10. Thus, this definition, by including newly initiated indications, differs from the traditional POD definition.
Since the newly initiated indications are appropriate for APC applications, POPCD is an acceptable definition and eliminates the need to adjust the traditional POD for new indications.
The above definition for POPCD would be entirely appropriate if all EOC-10 indications were RPC inspected. Since all EOC-10 bobbin indications were not RPC inspected, a lower bound POPCD estimate can be made by assuming that all bobbin indications not RPC inspected would have been RPC confirmed. This definition is applied only for the 1995 EOC 10 indications not RPC inspected since inclusion for the EOC-9 inspection could increase POPCD by including indications on a tube l plugged for non-ODSCC causes. This lower bound POPCD can be obtained by g replacing the EOC-10 RPC confirmed by RPC confirmed plus not RPC inspected in g the above definition of POPCD. Inclusion of the indications not RPC inspected in POPCD primarily influences detectability below two volts since indications > 2.0 volts g which are not plugged for other causes are RPC inspected at Farley-2. For this a report, both POPCD definitions are evaluated for Farley Unit 2.
The POPCD evaluation for the 1993 EOC 9 inspection data is summarized in Table 4-7. Figure 4-7 shows POPCD evaluated for RPC confirmed plus not RPC inspected indications and the EPRI POD developed by analyses of field indications for 3/4 inch diameter tubing in Model D SGs. As expected, the use of POPCD based on RPC confirmed plus not RPC inspected leads to a lower POPCD. The lower POPCD for g using only RPC confirmed indications in the 0.6 - 0.8 volt bin is due to only two 3 confirmed indications being available to evaluate POPCD in this voltage range. As shown in Table 4-7, there are only 19 RPC confirmed plus RPC not inspected indications between 1.2 and 3.0 volts for evaluating POPCD. Thus a reliable POPCD cannot be determined in this voltage range. The 33% POPCD between 1.6 and 1.8 volts is based on only three indications. The limited data would indicate an average POPCD of about 60% (9 of 15 indications detected at EOC 9) between 1.2 and 2.0 l
volts and 100% (4 of 4 indications) above 2.0 volts. It is seen that the Farley-2 POPCD is higher than the EPRI POD below 0.8 volt and lower than the EPRI POD above 0.8 volt. Above 1.8 volts, POPCD is 1.0 while the EPRI POD equals 1.0 at 3.0 volts. However, there are only six Farley-2 indications above 1.8 volts.
The POPCD was also calculated using 1993 EOC-9 data to evaluate POPCD at the 1992 EOC-8 inspection. The IPC at Farley-2 was initially implemented in 1990 at EOC-7. The POPCD evaluation for the 1992 EOC-8 inspection is summarized in Table 4-8 and shown in Figure 4-8. For this case, the lower bound POPCD based on RPC confirmed plus not tested is below the EPRI POD curve above 0.6 volt. The low l
_ . _ _ . 44 __ g I
50% POPCD between 1.6 to 1.8 and 1.8 to 2.0 volts includes only two indications in each bin and one missed indication results in the 50% POPCD in these bins. As shown in Table 4-8, there are only 16 RPC confirmed plus not RPC inspected l indications between 1.2 and 3.0 volts for evaluating POPCD and a reliable POPCD l cannot be obtained in this voltage range. The limited data indicate an average POPCD of about 77% (10 of 13 indications detected at EOC-8) between 1.2 and 2.0 volts and 100% (3 of 3 indications) above 2.0 volts. The POPCDs for EOC 8 and
.g EOC-9 are similar above 1.2 volts while the EOC-9 POPCD is higher than the EOC-8 5 POPCD below 1.2 volts. Both inspections support a POD of about 1.0 above 2.0 volts.
In summary, the Farley Unit 2 EOC-8 and EOC-9 POPCDs support a voltage dependent POD higher than the NRC POD = 0.6 and approaching unity above - 1.8 volts. It is concluded that the POD applied for IPC leak and burst projections needs to be upgraded from the POD = 0.6 to a voltage dependent POD. This conclusion is l further supported by the comparisons in Section 7 between projected and actual EOC-10 voltage distributions.
4.4 ASSESSMENT OF RPC CONFIRMATION RATES This section tracks the 1993 EOC-9 indications left in service at BOC-10 relative to RPC inspection results in 1995 at EOC-10. The composite results for all SGs are given in Table 4 9. For 1993 bobbin indications left in service, the indications are tracked relative to 1993 RPC confirmed,1993 RPC NDD,1993 bobbin indications not RPC inspected and 1993 bobbin indications with no indication found in 1995. Also included are new 1995 indications. The table shows, for each category ofindications, the number ofindications RPC inspected and RPC confirmed in 1995 as well as the percentage of RPC confirmed indications.
I The 1995 RPC confirmation rate for eighteen 1993 RPC NDD indications left in I service was 0.0% averaged over all SGs. Out of ten 1993 RPC NDD indications left in service and RPC inspected in 1995, none of the indications were confirmed as flaws by RPC in 1995. For the Farley-2 Cycle 9 inspection, the confirmation rate for RPC I NDD indications left in service at BOC-9 was also 0.0%, based on four indications RPC inspected. For successive IPC inspections at other plants, the confirmation rate for RPC NDD indications left in service was typically < 25%. It can be noted that the l NRC draft generic letter requires that all RPC NDD indications left in service be included in the SLB leak and burst analyses. This is clearly conservative for Farley-2 for which the last two cycles show 0.0% of the RPC NDD indications confirmed at the I next inspection. These results support weighting RPC NDD indications left in service by a factor of about 0.2 (based on industry experience) to define the BOC distribution j
for Farley-2 IPC evaluations.
g ___ 45 _m ,,
I
O O
For the new indications in 1995, the overall 60% RPC confirmation (12 of 20 indications) is higher than that found (33.3%) for all 1993 bobbin indications left in g service and the 100% confirmation (5 of 5 indications) found for bobbin indications not 5 previously RPC inspected. The RPC confirmation rate for new indications in 1993 at EOC-9 was 55%.
As shown in Table 4-9, there were 30 bobbin indications reported in '93 that were not called in '95. This compares to 71 new indications in 1995 such that the effective number of new indications is 41.
l 4.5 NDE UNCERTAINTIES ,
The NDE uncertainties applied for the Cycle 9 voltage projections in this report are documented in References 10.2 and 10.3. The probe wear uncertainty has a standard deviation of 7.0% about a mean of zero and has a cutoff at 15% based on implementation of the probe wear standard. The analyst variability uncertainty has a standard deviation of 10.3% about a mean of zero with no cutoff. These NDE uncertainty distributions are included in the Monte Carlo analyses used to predict the EOC-9 voltage distributions.
I I
I I
I Il l Ii I;
1 I
I, S \APC\ala95NAPk90 DAY.4 4-6 07/24 95. 15 30 l
I I Table 4 - 1 Farley Unit 2 - Steam Generator IPC Summary of Inspection and Repair For Tubes in Service During Cycle 10 Sleam Generatur A Steam Generator B in-Service During Cycle 10 g pi, g y, in-Service Dunng Cycle 10 g,pj g gi
-I Tules Tubes Tubes Tubes Voltage Field Retumed Retumed Resumed Field Rerumed Retumed Returned Bm Bobbm RPC RPC Indicanons to to to Bobbin RPC RPC Indications to to to in& canons Inspected Con 6nned Repaired Semce Service Semce ind casions Irispected Connemed Repaired Service Service Service
.I On 0.3 1
1 0
0 0
0 0
0 1 1 0 0
1 1
0 1
0 0
0 0 0 0 0 1
0 0
0 1
04 2 0 0 0 2 1 3 7 0 0 0 7 0 7
- 05 3 0 0 0 3 0 3 IS 0 0 0 15 0 !$
- 06 7 0 0 0 7 0 7 7 0 0 0 7 0 7 07 6 0 0 0 6 1 7 12 0 0 0 12 0 12 08 4 0 0 0 4 1 5 7 0 0 0 7 0 7 09 1 0 0 0 1 4 5 3 0 0 0 3 0 3 1 0 0 0 0 0 1 1 3 0 0 0 $ 0 $
, 1.1 0 0 0 0 0 3 3 1 0 0 0 1 0 1 12 1 0 0 0 1 2 3 2 0 0 0 2 0 2 1.3 1 0 0 0 1 I 2 4 0 0 0 4 i S 14 0 0 0 0 0 1 ! l 0 0 0 1 0 1
- 15 1 0 0 0 1 3 4 1 0 0 0 1 0 I 16 0 0 0 0 0 1 I i 1 0 0 1 0 1 17 I I I O I 2 3 1 1 0 0 1 0 1 18 0 0 0 0 0 0 0 0 0 0 0 0 0 0
- I 1.9 0 0 0 0 0 0 0 0 0 0 0 0 0 0 2 1 1 0 0 1 0 1 0 0 0 0 0 0 0 l 22 1 1 0 0 1 0 1 0 0 0 0 0 0 0 l 25 0 0 0 0 0 0 0 0 0 0 0 0 0 0 j Tmd 31 3 1 0 31 21 52 68 2 0 0 68 1 69 l
>IV 6 3 1 0 6 13 19 11 2 0 0 11 1 12 l >2V i 1 0 0 1 0 l 0 0 0 0 0 0 0 Sleam Generator C Combased Data In-Service Durmg Cycle 10 in-Service During Cycle 10 Deptwa All g y; Tubes Tubes Tubes Tubes Volta 8e Field Rerumed Retumed Reiurned Field Returned Retumed Returned l Bm Bobbm RPC RPC In& canons to to to Bobbm RPC RPC Inacations to to to
- indicanons inspected Con 6rmed Repaned Sernce Semce Semcc Indicanons inspected Confirnied Repaned Service Service Service i 01 0 0 0 0 0 0 0 1 0 0 0 1 0 1 03 2 0 0 0 2 0 2 4 0 0 0 4 0 4 j 04 2 0 0 0 2 1 3 11 0 0 0 11 2 13 05 14 0 0 0 14 1 15 32 0 0 0 32 1 33 06 19 0 0 0 19 3 22 33 0 0 0 33 3 36 07 18 0 0 0 le 8 19 29 0 0 0 29 9 38 08 to 0 0 0 to 8 18 21 0 0 0 21 9 30 l 09 7 0 0 0 7 5 12 11 0 0 0 11 9 20 1 4 0 0 0 4 8 12 9 0 0 0 9 9 18 11 8 8 6 0 8 7 IS 9 8 6 0 9 10 19 12 4 4 4 0 4 13 17 7 4 4 0 7 15 22 1.3 3 3 1 0 3 14 8 I
Il 3 1 0 8 13 21 14 2 2 1 0 2 8 10 3 2 1 0 3 9 12
[
1.5 2 2 0 0 2 2 4 4 2 0 0 4 $ 9 16 I I O O I 3 4 2 2 0 0 2 4 6 17 2 2 0 0 2 1 3 4 4 a 0 4 3 7 I
18 4 4 2 0 4 2 6 4 4 2 0 4 2 6 19 a l I I O 3 3 I i i 1 0 3 3 2 1 8 0 0 I $ 6 2 2 0 0 2 5 7 22 I I I I O O O 2 2 I I I O 1 2$ i 1 0 0 1 0 i i i 0 0 1 0 I
1 Total 99 30 46 2 97 89 186 198 33 17 2 1% ll 307 D i '. 30 30 16 2 28 $5 83 47 35 17 2 45 69 114
>2V 2 2 4 I i 0 1 3 3 1 1 2 0 2 I _ _.- - - 4-7 I
al
[M LJ ,l l
Table 4 - 2 l 1
Farley Unit 2 - Steam Generator IPC Summary ofInspection and Repair For Tubes Deplugged at EOC-10 )
$ team Generator A $leam Genernier B Vohage Be Feld Bobba RPC RPC Indvas-Returned p
Feld Bobbm RPC ILPC ladicauons Renweed a
I ladecstwms inspecsed Connemed Repowed Service indmons laspected Cos.nemed Repened semce 04 1 0 0 0 1 0 0 0 0 0 05 0 0 0 0 0 0 0 0 0 0 06 0 0 0 0 0 0 0 0 0 0 07 1 0 0 0 1 0 0 0 0 0 08 4 0 0 0 1 0 0 0 0 0 09 4 0 0 0 4 0 0 0 0 0 1 I O O O I O O O O O li 3 0 0 0 3 0 0 0 0 0 12 2 0 0 0 2 0 0 0 0 0 13 1 0 0 0 1 I O O O I 14 1 0 0 0 1 0 0 0 0 0 15 3 0 0 0 3 0 0 0 0 0 16 I I I O i 0 0 0 0 0 17 2 2 2 0 2 0 0 0 0 0 18 0 0 0 0 0 0 0 0 0 0 19 1 I I a 0 0 0 0 0 0 2 0 0 0 0 0 0 0 0 0 0 28 I I I I O O O O O O 22 0 0 0 0 0 0 0 0 0 0 23 0 0 0 0 0 0 0 0 0 0 24 0 0 0 0 0 0 0 0 0 0 25 4 i 1 1 0 0 0 0 0 0 26 8 I I I O O O O O O 28 0 0 0 0 0 0 0 0 0 0 35 0 0 0 0 0 0 0 0 0 0 imd 25 7 7 4 21 1 0 0 0 1
- IV 17 7 7 4 13 1 0 0 0 1
>2V 3 3 3 3 0 0 0 0 0 0 Eleam Generator C C0mbined Data Vohese Raurned F =id Renneed Be Fmid Babben RPC RPC Indicauone o Bobbm RPC RPC ladicauons e Indcatmas inspeceed Conrwmed Rapewed Servue Indeceaons inspected Conarmed Repswed Servus 04 1 0 0 0 l 2 0 0 0 2 OS I O O O I i 0 0 0 1 06 3 0 0 0 3 3 0 0 0 3 07 8 0 0 0 8 9 0 0 0 9 08 8 0 J 0 8 9 0 0 0 9 09 6 0 0 I $ lo 0 0 1 9 I 9 0 8 0 0
~0 1 10 1 9 18 7 7 7 0 7 ID 7 7 0 10 12 13 13 la 12
'0 0 0
13 IS 82 12 0 15 il ll 13 11 11 0 13 le 8 8 0 8 9 8 8 0 9 15 2 2 1 0 2 5 2 2 0 5 16 3 3 3 0 3 4 4 4 0 4 17 I I i 0 1 3 3 3 0 3 18 2 2 2 0 2 2 2 2 0 2 19 3 3 3 0 3 4 4 4 1 3 2 $ 4 4 0 5 5 4 4 0 $
21 1 I i 1 0 2 2 2 2 0 22 1 l i 1 0 t I i 1 0 23 2 2 2 2 0 2 2 2 2 0 24 I I I I O I 1 1 5 0 25 I I i 1 0 2 2 2 2 0 26 0 0 0 0 0 t i i 1 0 28 I I I i 0 I i i 1 0 35 i 1 i n 0 1 1 4 5 0 Toeal 99 el 61 10 89 125 68 68 14 lit blV 63 68 61 8 59 81 68 68 12 69 m2V 8 8 9 8 0 Il 11 11 11 0 RM3MRY XL4 DEFISSUMRY ?!21951142 AM 4-8 I
I
l i
L, c Table 4 - 3 j
Farley Unit-21995 EOC 10 TSP ODSCC Indication Axial Distribution e
S/G A S/G B l
L Tube Number Number Maximum Average Average Maximum Average Average Su W d age &M d e Plate Indications Vonage Indications age M age GM l
111 8 0 79 0.55 0.02 23 1.53 0.69 0.01 211 9 1.42 0.56 0.02 13 1.47 0.62 0.02 311 1 0.54 0.54 -0.08 4 1.63 0.83 0.06 dil i 1.69 I.69 0.09 1 0.67 0 67 0.01 Sil 2 0.68 0.68 0.03 5 129 0.99 -0.01 611 5 2.11 1.34 -0.17 4 1.14 0.71 0.04
( 7H 4 1.13 0.77 0.05 10 1.12 0.56 0.01
[ 2C 0 - - - 1 1.03 1.03 -0.09 l
3C I 0.73 0.73 0.17 0 - - -
[_ .
0 SC - - -
0 - - -
[ 6C 0 - - - 2 0.68 0.62 0.03 L 7C 0 - - - 4 1.21 0 83 -0.03 Total 31 67 S/G C Composite Tube Number Number Support Maximum Average Average Maximum Average Average M g Plate #98 98 V Itage Voltage Growth indications Indications til 48 1.87 0.81 0.05 79 1.87 0.75 0.04 211 14 2.15 0.72 -0 02 36 2.15 0.64 0.00 3H 6 0.76 0.55 -0.05 11 1.63 0.65 -0.02 411 5 1.72 0.98 -0.08 7 1.72 1.04 -0.04 511 7 2.43 1.28 0 04 14 2 43 1.09 -0.02 611 8 I.69 l 08 0.05 17 2.11 1.07 -0.02
[ 711 2C 0 7 1.78 1.09 0.00 21 1.78 0.77 0.01
- - l 1.03 1.03 -0.09 3C 0 - - - 1 0.73 0.73 0.17 SC 2 0.97 1.13 -0.02 2 0.97 1.13 -0 02 6C 0 - - -
2 0.68 0.62 0.03 7C 2 0 43 04 -0 07 6 1.21 0.69 -0 05 Total 99 197
(
l c, nom xmmumm a m 4-9
Table 4 -4 Farley Unit-21995 EOC-10 Average Voltage Growth History Composite of All Steam Generator Data Number of Average Volts Average Delta V % Growth Indications BOC Delta V EFPY Delta ViEFPY per cycle per EFPY 1993 - 1996 (Cycle 10)
Entire Voltage Range 197 0.79 0.010 1.20 0.008 1.2 1.0 V BOC < .75 122 0.55 0.020 0.017 3.6 3.0
> or = .75 75 1.18 -0.007 -0.006 -0.6 -0.5 1992 - 1993 (Cycle 9)
Entire Voltage Range 169 0.76 0.09 12 V BOC < .75 105 0.51 0.1 20
> or = .75 64 1.18 0.09 8 4
1990-1992 (Cycle 8) y Entire Voltage Range 308 0.73 0.14 1.11 0.13 19 17 V BOC < .75 233 0.57 0.17 0.15 30
> or = .75 75 1 23 0.04 0.04 3 1989 - 1990 (Cycle 7)
Entire Voltage Range 326 0.71 0.11 1.28 0.09 15 12 V BOC < .75 207 0.52 0.16 0.13 30
> or = .75 119 1.04 -0.12 -0.09 i -13 1987-1989 (Cycle 6)
Entue Voltage Range 316 l 0.59 l 0.2 1.14 0.18 l l l 34 l 30 1986 -1987 (Cycle 6)
Entire Voltage Range 291 l 0.55 l 0.13 1.26 0.10 l l l 24 l 19 GROWTH XI.51Toble 4 - 4[7/2095i4 M PM
l i JlIl i j 1l lI 1 1l1 lllllI lI,I i l r
w r f y
p e 0 0 2 5
2 3
6 9 1 4 9 9 6 1 r 0 0 2 4 3 2 3 1 0 1 e
p 1 3 0- 0- 4 5 1 2 0 1 3 0 h
t %
w o
r G
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< y 2 8 c 0 0 2 0 7 9 7 4 8 3 2 6 6 3 1 6 5 6 4 4 6 r 1
- e 1 3 0- 0- 5 6- 1 2 0 1 3 0 p
y p s f r
/
e t o 8 7 6 0 0 2 3 6 7 9 2 4 0 8 1 V a r
0 0
1 0 0 0 2 0 0 0 0
1 0
0 0
1 0
1 0
0 0
a e 0 0 0- 0- 0 0- 0 0 0 0 0 0 lt e n D
e A B C G r r r o o o m t a
t a
t a
0 a r r r 1
e e e e h y t S 0 n 0 n 0 n 0 t p 2 e 2 e 2 e 2 Cw f e
l l
A 1 G 1 G 1 G 1 Oo V m ErG f m m 5
D o a a a 5 e e e e e
- 99 e t t t g g t S S a V i s S ,
41 a t r a o 0 0 7 0
3 0
8 1 9
1 4 5 2 1 2 le2lo e t p 1 2 0 0 2 0
1 1 0 1 2 0 b
v l e
0 0 0 0 0 0 0 0 0 V A D m 0 0 0- 0- 0 0- 0 0 0 0 0 0 at Ti ne o Ug C
yr a e ev l
r C F
aA O B
V 9 5 8 6 4 8 0 2 8 7 8 0 e
g 7 5 1 7 5 3 7 5 0 8 5 2 0 0 1 0 0 1 0 0 1 0 0 1 a
r e
v A ~
f s o n r o e i t 7 2 5 3 7 5 2 9 4 b a 9 2 7 1
3 2 8 6 4 2 9 5 5
4 m ic 1 1 u d N I n
M P
9 3
4 l
l 5
e e e 9 g g g e g
/
0 n n n n 2
/
a a a a 7 R R R R 51 -
e g
e e e 4 5 g 5 g 5 g 5 a 7 5 7 a 7 5 a 7 57 a 7 5 le t t 7 t lt 7 b l
o < =
l a
lo < - o < = o < T V C > V C > V C > V C >- 9 ~
e r O e e e L i
r O r O r O X.
n B n B i i n B n B i
t t t t t .
i E V EV EV EV T O
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A.[
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Table 4 - 6 Farley Unit-21995 Signal Growth Statistics on EFPY Basis Cycle 9 Gmwth Cycle 10 Growth S/G A S/G B S/G C Combined S/G A S/G B S/G C Combined Bin No. of " " " " "
CPDF CPDF CPDF CPDF CPDF obs obs obs obs CPDF CPDF CPDF obs obs obs obs
-1.1 0 0 1 1.43 0 0 1 0.58 0 0 0 0 0 0 0 0
-0.6 0 0 1 2.86 0 0 1.16 0 0 0 1 0 0 0 0 0
-03 0 0 0 2.86 0 0 0 1.16 1 3.23 0 0 0 0 1 0.51
-0.2 3 14.29 5 10.00 4 4.94 12 8.14 6.45 0 0 1 2 2.02 3 2.03
-0.1 1 19.05 5 17.14 6 1235 12 15.12 2 12.90 5 7.46 13 15.15 20 12.18 0.0 1 23.81 17 41.43 16 32.10 34 34.88 10 45.16 24 43.28 35 50.51 69 47.21
- 0. I 5 47.62 14 61.43 16 51.85 35 55.23 15 93.55 31 89.55 38 88.89 84 89.85 0.2 7 80.95 12 78.57 17 72.84 36 76.16 2 100 6 98.51 6 94.95 14 %.95 03 1 85.71 6 87.14 7 81.48 14 8430 0 l 100 3 97.98 4 98.98 0.4 3 100 4 92.86 8 9?.36 15 93.02 0 0 1 98.99 1 99.49 0.5 0 2 95.71 1 92.59 3 94.77 0 0 0 98 99 0 A 99.49 0.6 0 1 97.14 2 95.06 3 %.51 0 0 0 98.99 0 99.49 h
to 0.7 0 2 100 I % 30 3 98.26 0 0 0 98.99 0 99.49 1.2 0 0 0 % 30 0 98.26 0 0 I 100 1 100 13 0 0 1 97.53 I 98.84 0 0 0 0 1.5 0 0 1 98.77 I 99.42 0 0 0 0 I.6 0 0 0 98.77 0 99.42 0 0 0 0 1.7 0 0 0 98.77 0 99.42 0 0 0 0 1.8 0 0 0 98.77 0 99.42 0 0 0 0 1.9 0 0 1 100 I 100 0 0 0 0 2.0 0 0 0 0 0 0 0 0 2.1 0 0 0 0 0 0 0 0 22 0 0 0 0 0 0 0 0 23 0 0 0 0 0 0 0 0 2.4 0 0 0 0 0 0 0 0 2.5 0 0 0 0 0 0 0 0 Total Obs 21 70 81 172 31 67 99 197 GROWTilELSITable 4-6(7/21/95{l1:48 AM
l l1l1 (l{ 1l l Ill i W
m 2 9 8 4 6 e
t n 6 5 O u 2 2 4 2 2 5 3 2 2 0 2 o 1 1 I / / / I I / / / / / !
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o e s C. lpni f i t C 9 1
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am u o ie F
l aC v
in, b
E b o e e 0 5C-. i 1 B 9 P 0 0 0 0 3 1 0 0 0 0 0 0 0 5 2 5
9 1 R ;n 1 C- 9 o O 9 C 1
E 5
9 e 9 1
Pdt d R n nc ote s 5 ;. up s e 0 7 4 3 7 6 2 2 2 0 0 0 0 0 3 2 n 9 2 1 6 1 io 9 wlpns e C t
a 1 I ic d
I n
M w P e
5C n d 1 4
N 9 2 5 9 P e 0 0 1 1 2 4 1 1 2 0 0 0 0 0 1 8 M 1 R i w
2 1
C 7 Ml U
S-L B
2 4 v m e g
tan lo i
B 0
0 0
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0 4
8 0-6 0
1 8
2 1
0 4
1 2
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1 6
0 2
8 2
2 0
5 2
2 0
3 5
0 4
0 L
A t
A T.
D C
P D
V 0 0 0 0 2 2 T ta P 1 1 1 1 1 2 3 t o
O T e-T M v'
8 9
D C
P o
g A , **-
P g
lll I l l ll)l l' .1 l , l' l .1 l l lllll ll
Table 4 - 8 Farley Unit-2 1993 EOC-9 Evaluation for Probability of Prior Cycle Detection (EOC-8)
Composite of All Steam Generator Data New Indications 1993 Bobbin, Fiekt Callin 1992 1992 Bobbin POPCD 1993 RPC 1993 RPC RPC Voltage 1993 Confirmed 1993 Confirmed 1992 Confirmeo Bn RPC plus not RPC plus not Confirmed RPC Plus Not Confirmed Inspected Conf med Inspected and Plugged Confirmed inspected Frac. Count Frac. Courit
> 0 - 0.2 0 0 0 3 0 -
0/0 1 3/3 0.2 - 0.4 I II I 15 0 0.500 I/2 0.577 15/26 0.4 - 0.6 1 16 7 32 0 0.875 7/8 0.667 32/48 0.6 -0 .8 5 17 7 23 0 0.583 7/I2 0.575 23 /40 0.8 - I.0 4 9 7 16 0 0.636 7 / II 0.640 16/25 1.0 - 1.2 I I O O 3 0.750 3/4 0.750 3/4 A 1.2-1A 1 I 2 1 1 0.750 3/4 0.750 3/4 h
A I.4 - 1.6 1 I I I O 0.500 I/2 0.500 I/2 1.6 - I.8 '
O O O 5 I 5/5 I 5/5 1.8 - 2.0 1 1 0 0 1 0.500 1/2 0.500 I/2 2.0 - 2.2 0 0 0 0 1 I .1/1 I III 22 -2.5 0 0 0 0 1 1 1/1 1 I/I 2.53.0 0 0 0 0 I I I/I i 1/1 TOTAL 15 57 24 91 14 Total > IV . 4 4 2 2 14 1
I PCPCDe2 XLSANTABL.5tWad/o9t2 es P4 l
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i n e n i e n i 1 e o b n t o o bb s C D f c n c D N a o N bo i
p t o Me C C N
C B io t t Me C N N o io Me C C N o n o b S P C a l C B t a 5 C C B o S P C it u
l a P 5 n ic V P 5 9 S P a s o u n R R P R d P R n dic 19 P P 5 i r q i 3 3 3 9
o io t
n 0 R in 3 3 3 9o R n n R R R 9o n ic d t
ii I
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- - - - d n n o
l 5 b I
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N u V 39 s 3 N 3 e m i
9 S e 9 e d e r S l N Su in L G l
A -
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Figure 4 - 1
) Farley Unit-2 1995 EOC-10 l
Bobbin Voltage Distribution for Tubes in Service During Cycle 10 l 20 1
18 -
16 1 BSG-A 14 -
12 -
OSG-B 3
~
- asG-c i n.
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I Bobbin Voltage 4
BOBNSTAT,XLSFig 4-17/21351:59 PM M M M M M M M M M M M M M M M M M M* ' E E
l l l
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I Figure 4 -3 Farley Unit-2 1995 Bobbin Voltage Distribution for All Tubes Returned to Service at BOC-11 j 25 l
20 -
ESG-A
-g OSG-B 15 - - - -
mso-c 10 - - - --- - -
0 E :I E
- : : : : : : : :E :E :
2 2 $ $ $ $ $ $ 3 2 O' 2 3 0 0 O U U $ $ $
Bobbin Voltage l
RPCSMRY.XLSFig 4-37/21/951:47 PM E E E E NE
p m M' M p W W W W M M M 'M M M M. W M' W Figure 4 - 4 Farley Unit-2 1995 EOC-10 Bobbin Voltage Distribution for Repaired Tubes 20 18 ESG-A 14 - -
g OSG-B 5 12 - --
.E 10 - --
E -
8- - -
z -
6- - -- -
4- - - - -- -
2 - - - - - -
0 : : : : : : : : : : ": : : :
2 2 $ $ $ $ $ $ 3 2 U U 3 2 3 O U 3 $ 0 $
i Bobbin Voltage RFCSMRY.XLSTig 447/21/95 I:52 PM I
Figure 4 - 5 Farley Unit-21995 ODSCC Axial Dist ibution f. r Tubes in Service During EOC-10 50 45 -
40 35 ESG-A E
, j 30 0SG-B 4
0 25 -
% ESG-C
! .5 i E 20 - -
Z 15 10 - -
II; . I;_J= , m . , ., n;1 e , , , e e , e e e e e Tube Support Plate l
, GROWHI.XLSFig 4 57/21/95135 PM l aus uma mas amm sua e mas sum me sum num aus as as ime man su as aa
g g g g g g 3 p W W W W W W W E W E W Figure 4 - 6 Farley Unit-2 Cycles 9 and 10 Cumulative Probability Distributions for Growth on EFPY Basis 100 -
= 2 f.j,__4 y _ __c__ _ _ _ -- &
4.,, , s -
90 -
[-
80 '
70 -
.g 5
,y 60 -
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- e- SG - C Cycle 10
$ sj --o--SG - A Cycle 9 O
l 30 - 8
- *-- SG - B Cycle 9 20 -
-o-SG - C Cycle 9 to - a[ -A I
? 0
.._._.----s------ /
w : _ : : : : :
- - m o n y ci
- m n
Growth per EFPY - Volts GROWTILXLSFig 4-67/2385 6:17 PM
Figure 4-7 Farley Unit - 2 1995 EOC-10 Evaluation for POPCD at EOC-9 Cycle Data 1.0 - - -
,_- =-- --- --
,d' 0.9 /
/
/
/
0.8
/
ei- - - -x x- <- - - * '
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w 0.0 - : : : :
0 0.5 1 1.5 2 2.5 3 Dobbin Amplitude POPCD93.XLSJALLSG-POPCD-Chm 1!7/23/95l6:13 PM
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jl lj\lli I ll1 l lll ll l?1,l\
5.0 DATA BASE APPLIED FOR IPC CORRELAT)ONS The database used for the IPC correlations that are applied in the analyses of this report are consistent with the NRC SER applicable to the 1995 Farley Unit 2 inspection as documented in Reference 10.2. The SER recommended data for the burst pressure correlation is the same as the EPRI recommended database described in Reference 10.5 and is applied in the analyses of this report.
For the SLB leak rate correlation, the NRC recommends that Model Boiler specimen 542-4 and Plant J-1 pulled tube R8C74, TSP 1 be included in the database. This database is referred to as the NRC database in Reference 10.5 and is applied for the leak rate analyses of this report. The probability ofleakage correlation of Reference 10.5 is also accepted by the NRC SER and applied in this report.
SAAPC\mla95\APR90 DAY.5-9 5-1 om4ss. 27.s4
i I
6.0 SLB ANALYSIS METHODS-Monte Carlo analyses are used to project the EOC-11' voltage distributions and to calculate the SLB leak rates and tube burst probabilities for both the actual EOC-10 voltage distribution and the projected EOC-11 voltage distribution. These methods are consistent with the requirements of the Farley 2 NRC SER and are described in the IPC report of WCAP-14123 (Reference 10,5) and the generic methods report of WCAP-14277 (Reference 10.1).- 1 Based on the NRC SER recommended leak rate database, the leak rate data do not satisfy the requirement for applying the SLB' leak rate'versus bobbin voltage correlation. The NRC requirement is that the p value obtained from the regression for the slope parameter be less than or equal to 5%. For the NRC recommended data, the p value is about 6.5% and the leak rate versus voltage correlation is not applied.
Tim SLB leak rate correlation applied is based on an average of all leak rate data independent of voltage. The analysis methods for applying this leak rate model are given in Section 4.6 of WCAP-14277. A Monte Carlo analysis is applied to account for parameter uncertainties even though the leak rate is irdependent of voltage. This method ofleak rate analysis is similar to that of draft NUI!EG-1477 except for the uncertainty treatment. The analyses of this report found that the Monte Carlo analyses for the SLB leak rate with the leak rate independent of voltage results in leak rates within 10% of that obtained using the draft NUREG-1477 methodology.
)
S \APC\ala95\APR90 DAY.6 9 6-1 07/24S5,17.56
7.1 PROBABILITY OF DETECTION (POD)
The number ofindications used in the analysis to predict tube leak rate and burst
( probability is obtained by adjusting the number ofindications reported, to account for measurement uncertainty and birth of new indications over the projection period.
This is accomplished by using a Probability of Detection (POD) factor. The calculation of projected bobbin voltage frequency distribution is based on a net total number ofindications returned to service, defined as:
)
N j Nr, ars = - N a,,,sa + No,,m,,,,,
i where j
hira nrs = Number of bobbin indications being returned to service for the next !
cycle l Ni = Number of bobbin indications (in tubes in service) reported in the current inspection.
POD = Probability of Detection N,,,,3a = Number of N i which are repaired (plugged) after the last cycle N a,,io,,,a = Number ofindications which are deplugged after the last cycle and are returned to service in accordance with IPC applicability.
l The draft NRC generic letter (Reference 10.8) requires the application of a POD = 0.6 to define the BOC distribution for the EOC voltage projections, unless an alternate POD is approved by the NRC. A POD = 1.0 represents the ideal situation where all indications are detected; a voltage-dependent POD can provide a more accurate prediction of voltage distributions consistent with APC/IPC experience.
)
7.2 CALCULATION OF VOLTAGE DISTRIBUTIONS The growth rate distributions for each of the Farley Unit 2 steam generators for Cycle 10 are shown on Figure 4-6, together with the corresponding composite for Cycle 9. For Cycle 10, the growth in SG A is predominant in the low voltage range but SG C has the largest growth rates for the majority of the voltage range, particularly in the tail of the distribution (See Table 4-6) which is important for the leakage rate and burst probability analyses. Also, SG C has the majority of the indications at BOC-11. However, the Cycle 9 composite growth rate (Reference 10.6) substantially exceeds that of Cycle 10, and is used to predict the EOC-11 bobbin voltage distribution.
The operating periods used in the voltage projection calculations are recorded in i Reference 10.7:
I Cycle 9 = 462 EFPD. Cycle 10 = 439 EFPD. Cycle 11 = 479 EFPD.
l 1
[ I S \APC\ala95\APR90 DAY 5 9 7-1 OMMSIM9 I
l l ..
1 O
O 7.3 COMPARISON OF PREDICTED AND ACTUAL EOC-10 VOLTAGE DISTRIBUTIONS The methodology used in the projection of bobbin voltage frequency indications is described in References 10.1 and 10.4 and is essentially the same as that reported in g
Reference 10.6 for the Cycle 10 prediction. Those analyses reported the predicted EOC 10 bobbin voltage distributions in SG C, based on the BOC-10 conditions (excluding UOAs) and Cycle 9 growth rates. The actual EOC-10 bobbin voltage distributions and the corresponding predictions, summarized on Table 7-1 and shown l
on Figure 7-1, provide a comparison of two different detection uncertainty factors represented by: l o POD = 0.6, in accordance with the NRC direction of Reference 10.2, o POD = 1.0, a nominal value with no uncertainty considered.
As shown on Figure 7-1, the POD = 0.6 calculation conservatively over-predicts the bobbin voltage population distribution above 0.6 volts and is excessively conservative in the high voltage tail of the distribution, particularly above ~2 volts. The maximum B
3 predicted voltage is 4.4 volts whereas the actual maximum 2.5 bobbin voltage reported at EOC-10; 178 indications were predicted and 99 were actually reported at EOC-10. The POD = 1.0 prediction is in relatively good agreement with the actual E u
EOC-10 bobbin voltage; 100 indications were predicted and 99 were actually reported at EOC-10. A voltage-based POD would provide a more reliable prediction for IPC/APC performance, as discussed in Section 9. g 7.4 PREDICTED EOC-11 VOLTAGE DISTRIBUTIONS g Using the methodology previously described, analyses were performed to predict the performance of the Farley Unit 2 steam generators at EOC-11, based on the BOC-11 conditions summarized in Table 3-1 and the Cycle 9 growth distribution summarized .
in Table 4-6 (which is conservative, since it exceeds that of Cycle 10, but is in accordance with NRC guidance). EPRI has developed a voltage dependent POD based on expert opinion and multiple analysts' evaluations for plants with 3/4" l
diameter tubes. It is ofinterest to apply the EPRI POD for sensitivity analysis and for comparison with POPCD evaluations in Section 9. The BOC-11 IPC voltage E distributions are summarized on Table 7-2 for POD = 0.6, for the EPRI POD and for 3
POD = 1.0, which is the order of decreasing detection uncertainty. The EOC-11 IPC g voltage distributions are summarized on Table 7-3 for each steam generator for POD E
= 0.6. As anticipated, the limiting steam generator is SG C with 252 indications predicted for POD = 0.6. SG C performance for POD = 1.0 and for the EPRI POD E
is also included on Table 7-3 for information. The EOC-11 bobbin predictions for the 5 three steam generators are shown as histograms on Figure 7-2 for POD = 0.6.
Similarly, the EOC-11 bobbin predictions for the three PODS are shown as histograms on Figue 7-3 for SG C. The maximum bobbin voltage projected for EOC-g, ,
11 is 3.4 volts for POD = 0.6, and 3.3 volts for the EPRI POD and for POD = 1.0.
S MPC\ala95\ArR90 DAY.6-9 7-2 OWN95,18 02 I
g Table 7-1.
- i. Farley Unit 2 S/G C 1995 EOC - 10 Comparison of Predicted and Actual Bobbin Voltage Voltage Predicted Actual Range POD = 0.6 POD =1.0 0.3 4.6 2.7 2 0.4 ':4.8 8.9 2 0.5 17.8 10.7 14 0.6 20.4 12.2 19 0.7 22.0 13.1 11 0.8 19.9 11.8 10 1 0.9 17.0 10.0 7 1.0 14.0 8.0 4 1.1 10.7 5.9 8 5 1.2 7.7 4.0 4 1.3 5.4 2.7 3 I 1.4 1.5 4.1 3.1 2.0 1.5 2
2 1.6 2.4 1.2 1 1.7 2.0 1.0 2 1.8 1.7 0.8 4 I 1.9 1.5 0.7 1
2.0 1.3 0.6 1 2.2 2.2 1.0 1 I 2.4 2.5 2.6 1.6 0.0 0.3 0.7 0
1 1.0 0.0 0 2.7 0.0 0.3 0 5 2.8 0.7 0.0 0 3.0 0.6 0.0 0 l 3.1 0.0 0.0 0 l
3.2 0.4 0.0 0 l 3.3 0.0 0.0 0 l 3.4 0.1 0.0 0 I 3.6 0.0 0.0 0 i 3.9 0.7 0.0 0 I 4.4 0.3 0.0 0 Total 177.8 100.0 99 FALTBL71.XLS 73 I
C
'U a
TABLE 7-2 FARLEY UNIT 2
SUMMARY
OF 1995 BOBBIN DATA FOR CYCLE 11 PREDICTIONS STEAM GENERATOR A STEAM GENERATOR S Voltage EOC 10 EOC-10 EOC-10 E11 E11 BOC-11 EOC 10 EOC-10 EOC-10 E11 E11 E1' Ben Bobben W Rugged POD =
06 POD =
1.0 Bobtzn Rugged Rugged POD =
06 POD =
1.0 Tubes Tubes Tubes Tm 0 10 1 0 0 17 33 1 0 0 0 00 00 0 0 20 0 0 0 00 00 0 0 0 0 00 00 0 -
0 30 1 0 0 17 23 1 1 0 0 17 23 1 0 40 2 0 1 43 47 3 7 0 0 11 7 13 0 7 0 50 3 0 0 50 51 3 15 0 0 25 0 25 6 15 0 60 7 0 0 11 7 11 1 7 7 0 0 11 7 11 1 7 0 70 6 0 1 11 0 98 7 12 0 0 20 0 17 6 12 0 80 4 0 1 77 65 5 7 0 0 11 7 96 7 0 00 1 0 4 57 53 5 3 0 0 50 38 3 1 00 0 0 1 10 10 1 5 0 0 83 62 5 1 10 0 0 3 30 30 3 1 0 0 17 12 1 1 20 1 0 2 37 31 3 2 0 0 33 23 2 1 30 1 0 1 27 21 2 4 0 1 77 54 5 1 40 0 0 1 10 10 1 1 0 0 17 11 1 1% 1 0 3 47 41 4 1 0 0 17 11 1 1 60 0 0 1 1.0 10 1 1 0 0 17 11 1 1 70 1 0 2 37 30 3 1 0 0 17 10 1 1 80 0 0 0 00 00 0 0 0 0 00 00 0 1 90 0 0 0 00 00 0 0 0 0 00 00 0 2 00 1 0 0 17 10 1 0 0 0 00 00 0 2 20 1 0 0 17 10 1 0 0 0 00 00 0 2 50 0 0 0 00 00 0 0 0 0 00 00 0 TOT AL 31 0 21 72 7 68 5 52 68 0 1 114 3 102 2 69 31V 6 0 13 23 19 19 11 0 1 19 13 12
2V i 0 0 2 1 1 0 0 0 0 0 0 STEAM GENERATOR C COMBINED DATA Voltage EOC-10 EOC-10 BOC-11 BOC-11 000-11 EOC 10 EOC 10 BOC 11 Bin Babtzn Rugged # POD = POD = POD = Bobtxn Plug 2ed POD =
Tubes 06 EPRI 10 Tubes 10 0 10 0 0 0 00 00 0 1 0 0 1 OM 0 0 0 00 00 0 0 0 0 0 OM 2 0 0 33 47 2 4 0 0 4 0 40 2 0 1 43 47 3 11 0 2 13 0 00 14 0 1 24 3 24 9 15 32 0 1 33 0 60 19 0 3 34 7 33 0 22 33 0 3 36 0 70 11 0 8 26 3 24 2 19 29 0 9 38 0 60 10 0 8 24 7 21 7 18 21 0 9 30 09 _0 7 0 5 16 7 14 0 12 11 0 9 20 1 00 4 0 8 14 7 12 9 12 9 0 9 18 1 10 0 0 7 20 3 16 5 15 9 0 10 19 1 20 4 0 13 19 7 17 6 17 7 0 15 22 1 30 3 0 11 16 0 14 3 14 8 0 13 21 1 40 2 0 8 11 3 10 2 10 3 0 9 12 1 50 2 0 2 53 41 4 4 0 5 9 1M 1 0 3 47 41 4 2 0 4 6 1 70 2 0 1 43 31 3 4 0 3 L
1 80 4 0 2 87 61 6 4 0 2 6 1 90 1 1 3 37 30 3 1 1 3 3 2M i 0 5 67 60 6 2 0 5 7 2M i 1 0 07 00 0 2 1 0 1 2 SO 1 0 0 17 10 1 1 0 0 1 l TOT AL 99 2 89 252 0 225 9 186 198 0 20 111 0 307 siv 30 2 55 103 86 83 47 2 69 114 '
=2V 2 1 0 2 1 1 3 1 0 2 7-4 vnem e i4 ^u DOSNCOhOljtLB I ,
TABLE 7-3 FARLEY UNIT 2 PREDICTED EOC-11 BOBBIN VOLTAGE DISTRIBUTION STEAM GENER ATOR A STEAM GENERATOR B STEAM GENERATOR C Deita EOC-10 EOC 10 EOC-10 EOC-11 EOC-10 EOC-10 EOC 10 EOC 11 EOC-10 EOC-10 EOC 10 EOC 11 EOC-11 EOC11 Volt Bette Plugged Deptugged Indicatio is Bettin Plugged Deplugged ridications Ektbin Plugged Deplugg=d Incheations indcahans trecahons Tubes Tubes POD =0 6 Tubes Tubes POCho 6 Tubes Tubes POD =0 6 PO(>EPR1 POO=10 0 10 1 0 0 08 0 0 0 00 0 0 0 00 00 00 0 20 0 0 0 04 0 0 0 00 0 0 0 01 01 00 0 30 1 0 0 11 1 0 0 10 2 0 0 15 21 09 0 40 2 0 1 25 7 0 0 62 2 0 36 1 40 23 0 50 3 0 0 39 15 0 0 13 1 14 0 12 6 13 1 1 79 0 60 7 0 0 70 7 0 0 13 6 19 0 3 21 1 20 6 13 5 0 70 6 0 1 84 12 0 0 15 2 11 0 8 23 6 22 3 15 9 0 00 4 0 1 81 7 0 0 13 5 10 0 8 23 4 21 4 16 3 0 90 1 0 4 67 3 0 0 10 7 7 0 5 20 9 18 7 14 9 1 00 0 0 1 49 5 0 0 85 4 0 8 19 0 16 7 14 0 1 10 0 0 3 39 1 0 0 65 8 0 7 18 9 16 4 14 4 1 20 1 0 2 36 2 0 0 53 4 0 13 18 7 16 2 148 1 30 1 0 1 31 4 0 1 50 3 0 11 16 9 148 13 9 1 40 0 0 1 28 1 0 0 41 2 0 8 14 1 12 3 11 8 1 50 1 0 3 27 1 0 0 31 2 0 2 10 9 94 91 1 60 0 0 1 26 0 0 23 1 1 0 3 85 72 69 1 70 1 0 2 22 1 0 0 19 2 0 1 72 59 57
- 15) 0 0 0 18 0 0 0 14 4 0 2 65 52 51 0 1 90 0 0 0 13 0 0 0 09 1 1 3 59 47 46 2N 1 0 0 11 0 0 0 06 1 0 5 50 40 39 2 10 0 0 0 10 0 0 0 06 0 0 0 38 31 30
- 23) 1 0 0 09 0 0 0 00 1 1 0 27 22 21 2M 0 0 0 07 0 0 0 00 0 0 0 19 15 14 2 40 0 0 0 05 0 0 0 00 0 0 0 14 10 10 2 N) ._ 0 0 0 00 0 0 0 07 1 0 0 10 08 07
- 28) 0 0 0 00 0 0 0 00 0 0 0 08 06 06 2 70 0 0 0 07 0 0 0 03 0 0 0 06 07 06 2M 0 0 0 00 0 0 0 00 0 0 0 06 00 00 2 R) 0 0 0 03 0 0 0 00 0 0 0 00 00 00 3N O O O 00 0 0 0 00 0 0 0 00 07 07 3 10 0 0 0 00 0 0 0 00 0 0 0 07 00 00 3M 0 0 0 00 0 0 0 00 0 0 0 00 00 00 3M 0 0 0 00 0 0 0 00 0 0 0 00 03 03 3 40 0 0 0 00 0 0 0 00 0 0 0 03 00 00
- 39) 0 0 0 00 0 0 0 00 0 0 0 00 00 00 TOTAL 31 0 21 72 7 68 0 1 1143 99 2 89 2520 225 9 186 0
>1V 6 0 13 29 11 0 1 19 30 2 55 126 107 100
- 2V 1 0 0 4 0 0 0 0 2 1 0 14 11 10 acaeATs xts 7/1t/95 926 AM
O O
Figure 7 - 1 Farley Unit-2 1995 EOC-10 Comparison of Predicted and Measured Voltage Distributions SG-C POD = 0.6 25 20 - _
~
Total No. ofIndications Predicted Actual
,j 178 99 15 .- - - -
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I 8.0 TUBE LEAK RATE AND TUBE BURST PROBABILITIES 8.1 COMPARISON OF EOC-10 PREDICTIONS WITH ACTUAL LEAKAGE AND PoB Using the methodology previously described in this report, analyses were performed i I to calculate EOC-10 SLB tube leak rate and probability of burst (PoB) for the predicted and the actual bobbin voltage distribution previously presented in this report. The results of Monte Carlo calculations performed for the predicted (reported in Reference 10.0) and the actual voltage distributions are summarized on Table 8-1.
Comparison of the EOC-10 actuals with the correspondu ; predictions indicates that:
l a) SG C was predicted to be the most limiting steam generator for Cycle 10 (Reference 10.6).
b) SG C was confirmed to have the highest tube leak and PoB numbers based on actual ECT bobbin measurements at EOC-10.
c) The leak and PoB predictions (based en predicted indication population) are in reasonable agreement with actual leak and PoB values (based on ECT bobbin <
I measurements for EOC-10). The POD = 0.6 prediction for SG C was conservative by a factor of -1.8 for number ofindications and the SLB leak rate was slightly lower (0.20 vs 0.25 gpm). Both leak rate analyses are based on no I voltage dependence for the leak rate correlation. The EOC-10 projection applied Draft NUREG-1477 methods while the actual EOC-10 distribution analyses apply Draft NRC Generic Letter methods. The Generic Letter methods are slightly more conservative than the Draft NUREG methods.
The SLB leak rate of 0.25 gpm calculated from the actual EOC-10 voltage distribution is well below the Farley-2 allowable limit of11.4 gpm and the burst probability of 2.4 E-05 is also below the NRC reporting threshold of 1.0 E-2.
l 8.2 LEAK RATE AND TUBE BURST PROBABILITY FOR EOC-11 Calculations have been conducted to predict the performance of the limiting steam l generator C in Farley Unit 2 at EOC-11 conditions. The methodology used in these predictions is the same as previously described. Results of the EOC 11 predictions are summarized on Table 8-1. With the NRC endorsed POD = 0.6, the predicted I EOC-9 SLB leak rate for S/G C is calculated as 1.23 gpm and the EOC-11 SLB tube burst probability is calculated as 1.05 E-04. The performance of the individual steam generators, shown on Table 8-1, indicates that the limiting steam generator for Cycle I 11 of Farley Unit 2 is expected to be SG C.
I The projected EOC-11 SLB leak rate of1.23 gpm is below the Farley 2 allowable limit of 11.4 gpm and the projected tube burst probability of 1.05 E-04 is below the NRC reporting guideline of 1.0 E-02.
I S.\APC\nla95\APR90 DAY 5-9 8-1 07/24 95. 18 05 I
O O
I Table 8-1 Farley Unit 2 g
l - 1995 Outage g Sununary of SLB Tube Leak Rate and Burst Probability Cycle 9 = 462 EFPD, Cycle 10 = 439 EFPD, Cycle 11 = 462 EFPD No. of Max. SLB Burst Probability SLB CASE POD Indic- Volts Leak Rate ations 1 Tube >1 Tube Epm l
EOC 10 PREDICTION C 1.0 100. 2.7 1.9 E-05 Same 0.10*
0.6 C 178. 4.4 4.6 E-05 Same 0.20*
EOC-10 ACTUAL A 1.0 31. 2.4 2.3 E-05 Same 0.04 B 1.0 68. 2.0 9.2 E-06 Same 0.10 '
C 1.0 99. 2.7 2.8 E-05 Same 0.25 EOC-11 PREDICTION A 0.6 73. 2.9 2.4 E-05 Same 0.26 B 0.6 114. 2.7 7.3 E-06 Same 0.35 C 0.6 252. 3.4 1.05 E-04 Same 1.23 C EPRI 226. 3.3 8.5 E-05 Same 1.01 C 1.0 186. 3.3 9.96 E-05 Same 0.94
- Based on Draft NUREG 1477 methodology which most closely approximates the current actual I
analysis with no SLB leak rate vs voltage correlation. The 7/8" database does not satisfy NRC g statistical requirements for application of the correlation.
5 I
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1 9.0 COMPARISON OF POPCD FOR 9 INSPECTIONS,7 PLANTS WITH EPRI POD The evaluation of the probability of prior cycle detection (POPCD) for Farley Unit 2 is described in Section 4.3. At this time, POPCD evaluations are available for nine
[ inspections of seven plants, including the last two inspections at Farley-2. The available data include three inspections of plants with 3/4" diameter tubing and six r inspections of plants with 7/8" diameter tubing. This section summarizes these L POPCD evaluations for comparison with the EPRI proposed POD.
Figure 9-1 shows the POPCD evaluations for plants with 3/4" tubing. These results tend to indicate improvement in POPCD for the later inspections and support a POD approaching unity above - 2 volts.
Figure 9-2 shows the POPCD evaluations for plants with 7/8" diameter tubing and includes results for six inspections, including two Farley-2 assessments (Plant A -2).
[ The Farley 2 EOC-8 results represent the 1992 inspection while the EOC-9 results L represent the 1993 inspection. The lower POPCDs for Plants A 1 and A-2 (EOC-8) represent 1992 inspections such that the general trend also shows increasing PODS for later inspections. The lowest POPCDs at about 1.4 to 2.0 and 2.5 volts represent one or two missed indications in each of these bins and the data are not statistically significant. For the data of Figure 9-2, a POD approaching unity is supported above 3 volts and above 2 volts for inspections performed since 1992.
The individual plant POPCD evaluations can be combined for comparisons with the l EPRI proposed POD. Figures 9-3 to 9-5 show the combined data for 3/4" tubing, for 7/8" tubing and for the combined 3/4" and 7/8" tubing plants. The 3/4" POPCD is in very good agreement with the EPRI POD above 1.0 volt while the 7/8" POPCD is slightly lower than the EPRI POD above 1.0 volt. When all nine POPCD assessments are combined (Figure 9-5), there is generally good agreement with the EPRI POD although the trend exists to be below the EPRI POD. The definition of POPCD includes indications which were not present at the prior inspection and thus would be expected to be somewhat lower than the EPRI POD which is based on " expert" evaluations of inspection results and does not include indications clearly below detectable levels.
The POPCD evaluations shown in Figures 9-1 to 9-5 are based on the definition of
" truth" as RPC confirmed plus not RPC inspected indications. Since many of the indications not RPC inspected would be expected to be found to be NDD ifinspected, this represents a lower bound POPCD evaluation. Figure 9-6 shows the POPCD
) evaluation for all nine inspections based only on RPC confirmed indications. This
} results in a significant increase in POPCD below 1.0 volt and a modest increase between 1.0 and 1.5 volts. Above 1.5 volts, all indications are RPC inspected and S.\APC\ala95\APR90 DAY.5 9 9-1 07/2C95,15:07
)
I OI O
there is no difference in the definitions. The data supporting Figures 9-5 and 9-6 are given in Table 9-1. The data of Table 9-1 show more than 100 indications in all I! !
voltage bins below 1.8 volts and at least 28 indications in the voltage bins up to 4 l, volts. Thus the collective data are a reasonable basis for defining a POD.
As noted above, the POPCD evaluations performed since 1992 show significant improvement over the earlier assessments which represent the first IPC inspections. l Bobbin data analysis guidelines (Appendix A) have been revised since the first inspections to reflect the initial IPC experience. Thus, it is appropriate to assess POPCD for inspections performed since 1992. Five of the nine inspections for which l
POPCD has been evaluated were performed since 1992. The data for these five g inspections are given in Table 9-2 and the POPCD evaluation is shown in Figure 9-7 g for RPC confirmed plus not inspected indications. It is seen that the inspections since 1992 yield a POPCD in good agreement with the EPRI POD which was a 1994 g evaluation. POPCD supports a POD approaching unity above 2 volts while the EPRI E POD is about 0.98 at 2 volts and unity at 3 volts. Since the data analysis guidelines were revised since 1992 and significant experience has been gained in IPC g inspections, the POPCD of Figure 9-7 is the appropriate data for assessing voltage 5 dependent PODS for IPC applications. Figure 9-7 strongly supports the EPRI POD, without further adjustments for new indications, as an acceptable POD.
The results of Figure 9-7 clearly support an increase in the POD for IPC applications above the POD = 0.6, independent of voltage, required by the NRC draft generic g letter. For indications above 1.0 volt, the POD exceeds 0.8 and is 0.96 to near unity at 2.0 volts. A POD of 0.6 is only applicable to indications below about 0.6 volts.
The POPCD evaluations for nine inspections, including five inspections since 1992, I together with the EPRI POD evaluation provide a database for updating the NRC generic letter requirements on POD.
I I
I I
SAAPC\ala95\APR90 DAY.5-9 9-2 07/24/95, 15:07 I
I I
m M M M M M M W W M M M M M M M M M M Table 9 - 1 Combined POPCD Evaluation (9 Assessments) for All Plants POPCD Based on RPC Confirmed Plus Not Inspected Indications New Indications Bobbin Callin Both Inspections First Inspection POPCD RPC RPC Voltage Cor*med Cornmed RPC RPC RPC CorWmed Bir. RPC plus not RPC plus not Cor*med Confirmed Plus Not inspected Cor*med inspected Co *med inspected and Plugged Frac Count Frac Count
>0-02 6 492 0 449 8 0.500 6/12 0480 455/947 02-04 82 2180 23 2154 82 0.561 105/187 0 506 2238/4416 04-06 99 2750 123 2759 188 0.759 311/410 0.517 2947tss97 08-0 8 100 2171 257 2273 159 0.806 416/516 0.528 2432/4603 08-10 92 844 344 1262 185 0.852 529/621 0.632 1447t2291 e 10-1.2 85 142 141 303 435 0.871 576/661 0.839 73s/sso
. 1.2 - 1.4 38 62 51 100 265 7.893 316/354 0.655 assI427 D3 14-18 19 26 33 42 99 0.874 132/151 0.844 14t/187 16-18 9 10 12 12 84 0.914 96/105 0.906 9s/10s 13-20 4 4 7 7 49 0.933 56/60 0 933 5650 20-2.2 1 1 3 3 40 0 977 43/44 0 977 43/44 2.2 - 2.5 0 0 2 2 24 1 26/26 1.000 2st26 25-30 1 1 2 2 22 0.960 24/25 0.960 24/25 30-40 0 0 0 0 22 1 22/22 1.000 22/22 40-50 0 0 0 0 4 1 4/4 1.000 4t4 TOTAL $36 8683 998 9368 1664 Totnt =tv 157 246 251 471 1044 MASTER.XLS Tath 9-17/24/9512.59 PM
Table 9-2 Combined POPCD Evaluation for 5 Assessments Conducted After 1992 POPCD Based on RPC Confirmed Plus Not Inspected Indications New Indications Bobbin Callin Both inspections First inspection POPCD RPC RPC Voltage Cor*med Cor*med RPC RPC RPC Confirmed Bwn RPC plus not RPC plus not Confirmed Con %med Plus Not hspected Con &med inspected Con &med W and Plugged Frat Count Frac Count
>0-02 4 444 0 407 5 0.556 5/9 0 4e1 412tese 02-04 67 1546 18 1782 81 0.596 99/166 0 54s 1863/3409 04-Oe 84 1056 99 1733 183 0.770 282/366 0.645 tetef2972 05-0.s 73 416 218 1058 150 0.834 368/441 0.744 1208/1624 CD 08-t0 60 121 260 488 112 0.861 372/432 0.832 600f721 1.0 12 41 45 71 102 339 0.909 4101451 0.907 441/4,8 12-14 15 16 21 30 195 0935 216/231 0.934 225/241 14 1 e 7 9 14 17 72 0.925 86/93 0.908 stuge te.te 3 3 9 9 55 0 955 64/67 0.955 e4/e7 1 e . 2.0 2 2 3 3 33 0.947 36/38 0.947 3e/3s 2.0 - 2.2 0 0 3 3 26 1.000 29/29 1.000 2W29 22 25 0 0 2 2 15 1 17/17 1.000 17fty 25-30 0 0 2 2 17 1.000 19/19 1.000 twtg 30 40 0 0 0 0 18 1 18/18 1.000 tatts 40-50 0 0 0 0 4 1 4/4 1.000 4r4 TOTAL 356 3658 720 5636 1305 iTotal > tv 68 75 125 168 774 MASTE'tALS Table 9-2 7/24<T512.59 PM
g g g M g M M M M M M M E E E E E E E' Figure 9 - I POPCD Evaluation for Plants with 3/4" DiameterTubes POPCD Based on RPC Confirmed Plus Not Inspected Indications 1.0 x
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m m m M M mM M M M M M M M M M- M M m' Figure 9 -3 Combined POPCD Evaluation (3 Assessments) for Plants with 3/4" Dia. Tubes POPCD Based on RPC Confirmed Plus Not Inspected Indications 1.0
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10.0 REFERENCES
jg 10.1 WCAP-14277, "SLB Leak Rate and Tube Burst Probability Analysis Methods
'a for ODSCC at TSP Intersections", Westinghouse Nuclear Services Division, Jan.1995.
10.2 Safety Evaluation Report, " Safety Evaluation by the Office of Nuclear Reactor Regulation Related to Amendment No.106 to Facility Operating License l NPF-8, Southern Nuclear Operating Company, Inc., Joseph M. Farley Nuclear Station, Unit 2, Docket No. 50-364", United States Nuclear Regulatory Commission, April 7,1995.
.I 10.3 Draft NRC Generic Letter 94-XX, " Voltage Based Repair Criteria for the
- g Repair of Westinghouse Steam Generator Tubes Affected by Outside
- g Diameter Stress Corrosion Cracking", USNRC Office of Nuclear Reactor Regulation, August 1994.
10.4 WCAP-12871 Revision 2, "J.M. Farley units 1 and 2 SG Tube Plugging Criteria for ODSCC at Tube Support Plates", Westinghouse Electric Corporation, Proprietary Class 2, February 1992.
10.5 WCAP-14123 (SG 94-07-009), " Beaver Valley Unit 1 Steam Generator Tube Plugging Criteria for Indications at Tube Support Plates July 1994".
10.6 SG-93-11-015 Revision 2, "Farley-2 Cycle 9 Assessment and Projected EOC-10 SLB Leakage", Westinghouse Electric Corporation, January 14,1994.
10.7 Letter from Southern Nuclear Operating Company letter to USNRC Docket 50-364, " Joseph M Farley Nuclear Plant Technical Specification Changes Associated with Steam Generator Tube Support Voltage based Repair Criteria", March 20,1995.
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