ML20246F950
| ML20246F950 | |
| Person / Time | |
|---|---|
| Site: | Arkansas Nuclear  |
| Issue date: | 08/24/1989 |
| From: | Turk C ARKANSAS POWER & LIGHT CO. |
| To: | |
| Shared Package | |
| ML20246F906 | List: |
| References | |
| WP890132, NUDOCS 8908310181 | |
| Download: ML20246F950 (8) | |
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WP890132 Pcge 1 of 8 ARKANSAS NUCLEAR ONE, UNIT-2 Steam Generator Tubing Inservice Inspection Report 2R6 Refueling Outage INTRODUCTION An inservice inspection was cerformed on tubes in Arkansas Nuclear One, Unit-2 steam generators 2E-24A and 2E-24B during the period February 16-22, 1988. The minimum number of steam generators inspected and the number of tubes inspected in each steam generator were determined according to criteria outlined in Unit-2 Technical Specifications 4.4.5.1 and 4.4.5.2, respectively. Since the previous inspection was concluded on June 21, 1986, this inspection satisfied the minimum inservice inspection frequency as outlined in Technical Specification 4.4.5.3.
Tubes were inspected full length from the cold leg channel head with a 0.580" bobbin coil probe. The MIZ-18/DDA-4 multi-frequency eddy current system was used for data acquisition and analysis. All eddy current inspection data were analyzed by an independent group in parallel with the ISI contractor.
INSPECTION
SUMMARY
Eddy current inspections of steam generators 2E 24A and 2E-24B included first and second samples. The first sample contained 421 tubes, or approximately 5% of the 8411 tubes in each steam generator. Tubes were selected randomly 3/td from special interest (critical) areas such as tubes in the " kidney beand region, near the stay cylinder, around stay rods, etc., and those tubes known from previous inspections to contain imperfections >20% through wall (TW). In the
'A' steam generator first sample, 237 tubes were selected from special interest areas and 184 tubes were selected randomly. In the 'B' steam generator first sample, 225 tubes were from special interest areas and 196 tubes were selected randomly.
A second sample was also inspected in both steam generators following the discovery of three defective (240% TW) tubes in the 'B' steam generator first sample. The defects were wear-type indications located at the intersection of the horizontal sections of the tubes and " batwing" diagonal support straps. All defective tubes were located in one special interest area - near the stay cylinder. Similar
" batwing" wear problems have been observed in the stay cylinder area of other Combustion Engineering steam generators. The problem is a result of flow-induced vibrations in an area of high secondary side flow velocities and a slight variability in tube support mechanics.
Technical Specification 4.4.5.2 required the 'B' second sample contain an additional 6% (505 tubes) of the total tubes in the steam generator. The 'A' second sample was voluntarily included to assure that a similar " batwing" wear problen. had not gone undetected in the 'A' first sample. Both second samples were concentrated in the stay cylinder area in a band approximately six pitches out from the periphery.
All 235 'A' second sample tubes were located along the stay cylinder. In the 'B' second sample of 505 tubes, 366 tubes were located along with the stay cylinder and 139 tubes were randomly selected from the rest of the tube bundle.
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Page 2 of 8 All-defective tubes were re-tested for confirmation of defects and tube coordi-nates. The inspection of confirmed defects was performed using an 8 x 1 probe to better characterize details of each wear indication.
INSPECTION RESULTS Eddy current inservice inspection results for steam generators 2E-24A and 2E-248 are presented in Tables 1 and 2, respectively.
In the 'A' steam generator, no defective tubes were found. Eight tubes were classified as degraded with imperfections ran0ing from 21 - 35% TW. Six of the tubes were inspected in the first sample. Two imperfections were located at the hot leg tube sheet, five near hot leg eggcrate supports, and one at a " Batwing" support.
Twenty-eight tubes, having a total of thirty-four imperfections reported as
<20% TW, were identified. Seventeen of these tubes, with twenty-two imperfections, were inspected in the 'A' first sample. The location of the thirty-four imperfections were distributed among three general areas - hot leg tube sheet, hot leg egg crate supports, and cold leg tube sheet. Only two were found near cold leg egg crate supports.
None of the reportable imperfections in either first or second samples revealed a " batwing" wear problem in 'A' steam generator. However, two low-amplitude distorted indications (not reportable) were seen near " batwing" support straps.
These tubes will be included in future inspections as special interest tubes.
In the 'B' steam generator, three defective tubes, having a total of four defects 240% TW, were found in the 'B' first sample. No defective tubes were found in the second sample. As discussed above in the Inspection Summary, defects were located in the " batwing" section of the tubes. The three defective tubes were subsequently removed from service per Technical Specification 4.4.5.4.
Eleven tubes were classified as degraded. These tubes contained a total of twelve imperfections ranging from 21-39% TW. All degraded tube imperfections were located in the " batwing" section of the tubes. Four were inspected in the 'B' first sample and seven were inspected in the 'B' second sample. Two degraded tubes also contained one <20% TW imperfection each. Twc tubes with 38% and 39% TW imperfections were voluntarily removed from service.
Thirteen tubes, having a total of fifteen imperfections <20% TW, were identified. Eight were inspected in the 'B' first sample and five were inspected in the 'B' second sample. Nine tubes contained a <20% TW indication in the " batwing" section. No trend was noted in the location of !
other imperfections as they were evenly distributed frcm hot leg tubesheet ;
to cold leg tubesheet.
1 A high-amplitude distorted indication in tube R28-L300 is included in Table 2.
This anomalous indication was considered significant and caused the tube to be voluntarily removed from service.
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> TABLE 1
'A' Steam Generator Tubing Inspection 2R6 Reportable Indications 2 20% Throughwall Indications a
R0W ,
LINE LOCATION SAMPLE % TW INDICATION l
l-24 108 6H + 0" 2 21
- 39 83 2 BW1 23 42 66 TSH + 1.1" 1 26 62 100 6H + 25.8" 1 31 80 84 8H + 7.4" 1 29 82 64 TSH + 1.9" 1 27 91 107 5H + 19.4" 1 31
<20% Throuchwall Indications 12 58 TSH + 2.4" 1 <20 17 33 TSH + 2.3" 1 <20 17 33 TSH + 3.0" 1 <20 18 106 TSC + 2.9" 1 <20 24 106 6H + 7.6" 2 <20 24 108 5H + 28.5" 2 <20 25 59 TSC + 1.1" 2 <20 25 109 SH + 27.4" 2 <20 29 109 TSC + 0.8" 1 <20 31 105 6H + 29.9" 2 <20 D
32 96 BW3 + 0" 2 DI b
36 32 TSH + 3.0" 1 DI 36 60 TSH + 1.8" 1 <20 36 66 6H + 28.7" 2 <20 36 70 TSC + 2.10" 2 <20 36 100 TSC + 1.90" 2 <20
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TABLE 1 cont'd a
ROW LINE LOCATION SAMPLE % TW INDICATION b
37 43 TSH + 4.10" 1 DI 38 86 TSH + 0.9" 1 <20 39 81 TSC + 1.4" 2 <20 40 74 TSC + 0.7 2 <20 40 74 'TSC + 0.7 2 <20 40 82 TSH + 1.4" 1 <20 59 89 8H + 12.9" 1 <20 63 69 8H + 19.10" 1 <20 65 57 TSH + 3.2" 1 <20 67 67 TSH + 2.5" 1 <20 75 85 TSH + 5.9" 1 <20 77 69 8H + 19.7" 1 <20 80 84 TSH + 3.1" 1 <20 80 84 TSC + 1.1" 1 <2g 80 84 TSH + 4.1" 1 DI 91 75 9H + 7.9" 1 <20 91 103 4H + 12.1" 1 <20 91 103 4H + 25.2" 1 <20 91 103 5H + 20.3" 1 <20 91 103 9C + 8.7" 1 <20 91 107 5H + 6.6" 1 <20 b
110 134 BW1-0.9 1 DI b
121 73 4H + 8.7" 1 DI 135 105 4C + 21.4" 1 <20
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TABLE 1 cont'd a - Location: TSH - Tubesheet Hot leg TSC - Tubesheet Cold leg H, C - Hot leg, Cold leg Tube Supports (eg.. H7 - 7th Hot leg EggCrate. Support)
NOTE: Indication locations are reported in inches above tubesheet or support.
b - DI = Distorted' Indication a tube wall loss condition that is unquantifiable with a numeric percent call due to the signal characteristics (i.e, low signal-to-noise ratio).
t/P890132 Page 6 of 8 TABLE 2
'B' Steam Generator Tubing Inspection 2R6 Reportable Indications l 220% Throughwall Indications l
d R0W LINE LOCATION SAMPLE % TW INDICATION 28 100 BW1 - 0.7" 1 DIa ,b,e c
29 69 BW1 - 0.9" 1 72 c
30 70 BW1 - 0.9" 1 85 30 70 BW5 + 0.9" 1 53 c
36 92 BW5 + 0.9" 1 81 29 99 BW1 + 4.4" 1 26 29 101 BW5 2 30 b
32 70 BW1 - 0. 8" 1 39 32 70 BW5 + 0.9" 1 (20 34 94 BW1 - 1.1" 2 36 34 94 BW1 + 1.2" 2 <20 38 84 BW5 + 1.1" 2 29 38 86 BW5 - 0.9" 1 30 38 86 BW5 - 0.9" 1 23 b
39 83 BW5 + 0.9" 2 38 42 84 BW1 + 0.9" 2 29 77 89 TSH + 1.5 1 27 85 149 BW5 + 1.5" 2 21 103 29 BW5 + 1.0 2 25
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<20% Throughwall Indications d
R0W LINE LOCATION SAMPLE % TW' INDICATION 27 67 BW1 + 5.7" 1 <20 28 100 BW1 - 0.6" 1 <20 29 99 BW1 + 5.6" 1 <2g 29 99 BW5 - 0.9" 1 DI 30 62- BW1 + 0.6" 2 <2g 30 62 BW3 + 0.9 2 DI 32' 110 6C + 5.6" 1 <20 32- 110 BW1 + 7. 2" 1 <20 33' 95 BW1 + 13.7" 2 <2g 33 95 BW1 - 1.2" 2 DI" 33 95 BW5 + 1.3" 2 DI 34 64- TSH + 4.9" 2 <20 37 81 BW5 + 0.9" 2 <20 38 80 BW1 - 1.0" 1 <20 38 86 BW3 - 0.9" 1 DI' a - Large amplitude distorted indication b - Tube was voluntarily removed from service c - Tube was defective and removed from service d - Location: TSH - Tubesheet Hot Leg H, C - Hot leg, Cold Leg Egg Crate Support BW - Batwing Support Strap TSC - Tubesheet Cold Leg (Indication locations are reported in inches above eggerate support and tubesheet and inches on hot leg side (+) or cold leg side (-) of batwing supports).
e - DI = Distorted Indication - a tube wall loss condition that is unquantifiable l
with a numeric percent call due to the signal characteristics (i.e, low signal-to-noise ratio).
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,,,, Page 8 of 8 TABLE 2 cont'd d
R0W LINE LOCATION SAMPLE % TW INDICATION ~
47 8
.53 6H + 28.3" 3 D1
-47 131 2C + 30.2" 1 DI"
.69 93 TSC + 7.8" 1 <20 73 97 2H + 10.4" 1- <20 96 24 BW1 + 54.8" 1 <20 96 24 BW1 + 60.5 1 <20 100 56 7C + 6.0" 2 <20 102 8 96 TSH + 0" 1 D1 a - Large amplitude distorted indication b - Tube was voluntarily removed from service c - Tube was defective and removed from service d - Location: TSH - Tubeshcet Hot Leg H, C - Hot leg, Cold Leg Egg Crate Support BW - Batwing Support Strap TSC - Tubesheet Cold Leg (Indication locations are reported in inches above eggcrate support and tubesheet and inches on hot leg side (+) or cold leg side (-) of batwing supports).
e - DI = Distorted Indication - a tube wall loss condition that is unquantifiable with a numeric percent call due to the signal characteristics (i.e, low signal-to-noise ratio).
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