2CAN129613, Forwards Summary of a & B Steam Generator Tubes Inspected During Forced Outage
| ML20133E791 | |
| Person / Time | |
|---|---|
| Site: | Arkansas Nuclear  |
| Issue date: | 12/30/1996 |
| From: | Mims D ENTERGY OPERATIONS, INC. |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| References | |
| 2CAN129613, NUDOCS 9701130155 | |
| Download: ML20133E791 (7) | |
Text
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Entergy Operations, Inc.
= -ENTERGY
=m33 Rw/Mc AR 72301 Tcl 501858HCC December 30,1996 2CAN129613 U. S. Nuclear Regulatory Commission Document Control Desk Mail Station PI-137 Washington, DC 20555 1
Subject:
Arkansas Nuclear One - Unit 2 Docket No. 50-368 License No. NPF-6 2F96-1 Steam Generator Plugged Tube Summary Gentlemen:
Arkansas Nuclear One - Unit 2 (ANO-2) performed an extensive inspection of the "A" & "B" steam generator tubes during a recent forced outage (2F96-1). The results of this inspection are provided for your information.
On November 16,1996, after 362 days of operation since 2Rll, ANO-2 was taken offline
)
due to an indicated primary-to-secondary leak in the "B" steam generator of approximately 50 gallons per day (gpd). This leak rate was much less than the limit specified in Technical Specification 3.4.6.2 [0.5 gallons per minute (gpm) or 720 gpd] and therefore, an inservice inspection of the steam generators in accordance with Technical Specification 4.4.5.3.c.1 was not required.
The leaking tube (R16-L60) was detected by utilizing a 200 psi nitrogen over pressure on the secondary side of the "B" steam generator. Subsequent eddy current examination of the tube showed the leak to be from an axial crack at the first egg-crate support. Eddy current sized the flaw at approximately 1.3 inches long, with a through-wall extent of 92%. A review of the eddy current data from the two previous refueling outages showed no detectable indications at this location.
To determine the structural integrity of the flaw, a localized in-situ pressure test was conducted. The goal of this test was to measure leakage at accident pressure (2,950 psi) and to demonstrate structural integrity at the Regulator Guide 1.121 limit of 3AP (4,750 psi). The 1
flawed portion of the tube was initially pressurized to 1,750 psi, which equates to 100 psi
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above normal operating conditions. At this pressure, a leak rate of approximately 14 gpd was measured. Pressure was then raised to measure accident leakage. Due to the limited makeup hDO) 9701130155 961230
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R ADOCK 05000368 PDR
U. S. NRC December 30,1996 i 2CANI29613 Page 2 capability of the pressure test device, the highest pressure reached was 2,250 psi, the pressure at which the pump reached its maximum capacity of 0.4 gpm. A bladder was inserted into the test device and the flawed portion of the tube was pressurized to 3,975 psi before the tube failed. Subsequent visual examination of the tube showed an axial fishmouth tear.
It. is believed the flaw damage mechanism is outside diameter stress corrosion cracking (ODSCC). Due to the unusually rapid growth of the flaw which caused the leak, it was determined that a 100% bcbbin coil inspection of both steam generators was necessary. The inspection results indicated that, with the exception of two tubes, the axial flaws located primarily at the lower egg-crate support plates and in the hot leg sludge pile were, on average, not growing at an accelerated rate. No other flaws of the same magnitude as the one which leaked were detected. Based upon eddy current indications, it is expected t' a flaws detected, with the exception of R16-160, would meet the Regulatory Guide 1.121 limit for burst pressure. All tubes with _>40% through-wall flaws and those with flaws which exhibited high growth over the current cycle were removed from service. NJ freespan indications detected by the 100% bobbin coil examination were further examined with a rotating pancake coil (RPC). If the RPC confirmed the presence of a flaw, regardless of size, the tube was removed from service.
The root cause of the high growth exhibited in R16-160 is not currently known. To help determine the root cause, two tubes have been removed from the "A" steam generator for analysis. The next largest flaw, after the leaker, which demonstrated high growth and a relatively large flaw that has remained stable over the previous cycle, were removed. These tubes will be shipped to a laboratory for extensive chemical and material properties analyses.
The results of these analyses will be provided to the NRC following Entergy's review.
The need to perform a top-of-tubesheet circumferential crack examination was also considered. It was concluded, based upon the available data, that the assessment performed
- earlier in the year, justifying full cycle operation was still valid. This assessment was formally transmitted to the NRC on July 30,1996 (2CAN079604). Based upon concerns expressed by the NRC with this decision during telephone conferences the weeks of November 17 and 24, 1996, ANO committed to perform a hot leg top-of-tubesheet RPC examination of 100 percent of the tubes in both steam generators. A total of 26 relatively small circumferential indications were detected during this examination. Two of the largest indications were in-situ tested to 6800 psi with no indication ofleakage.
Tabulations of the tubes which were removed from service as a result of the examinations performed during 2F96-1 are attached.
The complete result of the examinations performed during 2F96-1 will be provided in the annual steam generator inservice inspection report to be submitted by February 28,1997.
Ifyou have any questions associated with this submittal please do not hesitate to contact me.
U. S. NRC December 30,1996
'.2CAN129613 Page 3 Very truly yours, W
wig
.Mims Direct, Nuclear Safety DCM/dej attachment cc:
Mr. Leonard J. Callan Regional Administrator i
U. S. Nuclear Regulatory Commission Region IV 611 Ryan Plaza Drive, Suite 400
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Arlington, TX 76011-8064 NRC Senior Resident Inspector Arkansas Nuclear One P.O. Box 310 i
London, AR 72847 Mr. George Kalman NRR Project Manager Region IV/ANO-1 & 2 U. S. Nuclear Regulatory Commission NRR Mail Stop 13-H-3 i
One White Flint North j
11555 Rockville Pike Rockville, MD 20852
Attachment to 2CAN129613
- Page l' of 4 Attachment INSPECTION RESULTS A total of 217 tubes were removed from service by plugging. Steam Generator (SG)"A" contained 73 tubes and SG "B" contained 144 tubes which were removed from service.
The predominant reason for plugging was axial indications at the hot leg egg-crates.
Other causes for plugging included top-of-tube sheet (TTS) circumferential indications
[ detected by rotating pancake coil (RPC)], batwing wear, volumetric indications, free span indications and preventative plugging. Below is a summary of the repair results:
Type of Indication No. in "A" No. in "B" Total Freespan Axial 4
0 4
EC Axial 29 100 129 TTS Circumferential 13 13 26 TTS Axial 6
3 9
Batwing 0
11 11 Preventive 9
14 23 Other 12 3
15 Total No. of Plugged Tubes 217 There were 4 tubes removed from service due to literal compliance issues that had j
indications measured 2 40 % by bobbin, but were dispositioned by RPC as no detectable indication. The remainder of the "Other" category were volumetric in nature. Listed below is a break down by tube and type ofindication:
Attachment to 2CAN129613 Page 2 of 4 SG "A" PLUG LIST FOR 2F96-1 1
No.
Row Line Reason for Plue No.
Row Line Reason for Plue 1
36 3
Freespan axial 38 100 88 SCI 2
36 12 Freespan axial 39 139 89 Preventive 3
35 27 Preventive 40 61 91 Preventive 4
14 36 SCI 41 44 92 EC axial 5
20 38 EC axial 42 48 92 EC axial 6
46 38 EC axial 43 81 93 Vol. in freespan 7
33 39 Freespan axial 44 70 98 EC axial 8
28 40 SCI 45 41 99 Preventive 9
37 41 SCI 46 113 99 SCI 10 1
43 Volumetric 47 75 103 Volumetric 11 40 46 2 40% by bobbin 48 24 104 TTS axial 12 40 50 TTS axial 49 25 105 TTS axial 13 59 53 Preventive 50 29 105 TTS axial 14 16 56 EC axial 51 35 105 2 40% by bobbin 15 104 56 Preventive 52 65 105 2 40% by bobbin 16 13 57 Preventive 53 79 105 Vol. in freespan 17 29 57 EC axial 54 82 106 EC axial 18 87 59 Preventive 55 19 107 TTS axial e
19 53 61 EC axial 56 97 107 Vol. in freespan 20 74 62 EC & TTS axial 57 14 110 Freespan axial 21 47 63 EC axial 58 16 110 EC axial 22 53 65 SCI 59 32 110 EC axial 23 97 65 2 40% by bobbin 60 34 110 EC axial 24 92 68 EC axial 61 17 111 SCI 25 60 70 SCI 62 5
113 SCI 26 102 70 SCI 63 94 116 EC axial 27 63 71 SCI 64 50 118 EC axial 28 58 72 EC axial 65 4
124 EC axial 29 74 72 Preventive 66 40 124 EC axial 30 82 78 Vol. in freespan 67 60 126 SCI 31 57 79 EC axial 68 8
138 EC axial 32 40 82 EC axial 69 34 146 EC axial 33 51 83 EC axial 70 30 148 EC axial 34 70 84 TTS axial 71 24 150 SCI 35 51 85 EC axial 72 14 164 Vol. in freespan 36 66 86 EC axial 73 22 164 Vol. in freespan 37 65 87 EC axial SCI - Single Circumferential Indication EC - Egg-Crate TTS - Top-of-Tubesheet Vol-Volumetric i
I Attachment to 2CAN129613
.Page 3 of 4
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SG "B" PLUG LIST FOR 2F96-1 No.
Row Line Reason for Plue No.
Row Line Reason for Plue 1
9 15 EC axial 73 82 80 EC axial 2
15 17 EC axial 74 82 82 EC axial 3
9 19 EC axial 75 110 82 EC axial 4
9 21 EC axial 76 46 84 E C A xial 5
9 23 EC axial 77 50 84 EC axial 6
8 24 EC axial 78 62 84 EC axial i
7 1
27 EC axial 79 38 86 Batwing 8
2 30 EC axial 80 72 88 EC axial 9
4 30 EC axial 81 81 89 EC axial 10 38 30 EC axial 82 73 91 EC axial 11 5
31 EC axial 83 85 93 SCI 12 4
32 EC axial 84 74 94 EC axial 13 14 32 EC axial 85 71 95 EC axial 14 5
35 EC axial 86 79 95 EC axial 15 85 35 Preventive 87 65 95 TTS 16 10 38 EC axial 88 70 98 TTS axial 17 20 38 EC axial 89 30 98 Batwing 18 22 38 EC axial 90 73 99 EC axial 19 55 45 SCI 91 38 100 EC axial 20 14 46 EC axial 92 103 101 EC axial 21 30 46 EC axial 93 51 101 EC axial 22 23 47 SCI 94 30 102 EC axial 23 12 48 EC axial 95 54 102 EC axial 24 14 48 EC axial 96 79 103 EC axial 25 77 49 EC axial 97 19 105 EC axial 26 95 49 EC axial 98 21 105 EC axial 27 15 49 Preventive 99 40 106 EC axial 28 14 50 EC axial 100 54 106 EC axial 29 22 50 Preventive 101 17 107 EC axial 30 37 51 TTS axial 102 80 108 EC axial 31 83 51 SCI 103 32 110 EC axial 32 87 51 SCI 104 46 110 EC axial 33 19 51 EC axial 105 50 110 EC axial 34 53 53 Batwing axial 106 62 110 EC axial 35 21 53 EC axial 107 64 110 EC axial 36 74 54 Preventive 108 91 111 SCI 37 45 57 Batwing 109 41 111 Preventive 38 1
57 EC axial 110 30 112 EC axial 39 24 58 Batwing 111 62 112 EC axial 40 83 59 EC axial 112 85 113 EC axial 41 5
59 EC axial 113 63 113 EC axial
Attachment to 2CAN129613 Page 4 of 4 4
o SG "B" PLUG LIST FOR 2F96-1 No.
Row Line Reason for Plue No.
Row Line Reason for Plue 42 3
59 EC axial 114 27 117 Preventive 43 16 60 EC axial 115 47 117 EC axial 44 91 61 EC axial 116 16 120 EC axial 45 79 61 SCI 117 104 120 EC axial 46 113 61 SCI 118 80 120 EC axial 47 11 61 EC axial 119 33 121 EC axial 48 25 61 EC axial 120 14 122 EC axial 49 22 62 EC axial 121 16 122 EC axial j
50 36 62 Preventive 122 36 122 SCI 51 105 63 SCI 123 42 122 Preventive 52 76 64 EC axial 124 22 124 EC axial 53 80 64 EC axial 125 4
126 Preventive 54 26 64 SCI 126 59 127 EC axial 55 20 64 EC axial 127 12 128 EC axial 56 64 68 EC axial 128 73 131 Batwing 57 76 68 EC axial 129 36 132 TTS axial 58 112 68 EC axial 130 3
133 EC axial 59 33 69 EC axial 131 69 133 Batwing 60 137 69 Batwing 132 1
135 Preventive 61 106 70 Batwing 133 65 135 Preventive 62 58 72 EC axial 134 16 138 EC axial 63 65 73 EC axial 135 83 139 Batwing 64 44 74 EC axial 136 9
141 EC axial 65 48 74 EC axial 137 23 141 Preventive 66 76 74 EC axial 138 11 145 SCI 67 68 76 EC axial 139 61 147 Batwing 68 72 76 Preventive 140 63 147 Batwing 69 109 77 SCI 141 1
149 EC axial 70 36 78 EC axial 142 12 156 Preventive 71 64 78 EC axial 143 7
157 EC axial 72 78 78 EC axial 144 38 160 Batwing SCI - Single Circumferential Indication EC - Egg-Crate TTS - Top-of-Tubesheet Vol-Volumetric l