ML23304A013
| ML23304A013 | |
| Person / Time | |
|---|---|
| Site: | Surry  |
| Issue date: | 10/30/2023 |
| From: | Denise Wilson Virginia Electric & Power Co (VEPCO) |
| To: | Office of Nuclear Reactor Regulation, Document Control Desk |
| References | |
| 23-258 | |
| Download: ML23304A013 (37) | |
Text
October 30, 2023 VIRGINIA ELECTRIC AND POWER COMPANY RICHMOND, VIRGINJA 23261 United States Nuclear Regulatory Commission Attention: Document Control Desk Washington, DC 20555-0001 VIRGINIA ELECTRIC AND POWER COMPANY SURRY POWER STATION UNIT 2 filEAM GENERATOR TUBE INSPECTION REPORT FOR THE SPRING 2023 REFUELING OUTAGE Serial No.
SS&L/MMT Docket No.
License No.23-258 RO 50-281 DPR37 Technical Specification 6.6.A.3 for Surry Power Station Units 1 and 2 requires the submittal of a Steam Generator Tube Inspection Report to the NRC within 180 days after Tavg exceeds 200°F following completion of an inspection performed in accordance with Technical Specification 6.4.Q, Steam Generator Program. Attached is the Surry Unit 2 report for the Spring 2023 refueling outage.
If you have any questions concerning this information, please contact Mr. Michael M.
True, Jr. at (757) 365-2446.
Very truly yours, David H. Wilson Site Vice President
Attachment:
Surry Unit 2 Steam Generator Tube Inspection Report for the Spring 2023 Refueling Outage Commitments made in this letter: None
cc:
U.S. Nuclear Regulatory Commission Region II Marquis One Tower 245 Peachtree Center Ave., NE Suite 1200 Atlanta, Georgia 30303-1257 Mr. John Klos NRC Project Manager - Surry U. S. Nuclear Regulatory Commission One White Flint North Mail Stop 09 E-3 11555 Rockville Pike Rockville, Maryland 20852-2738 Mr. G. Edward Miller N RC Senior Project Manager - North Anna U.S. Nuclear Regulatory Commission One White Flint North Mail Stop 09 E-3 11555 Rockville Pike Rockville, Maryland 20852-2738 NRC Senior Resident Inspector Surry Power Station Mr. Rusty R. Richardson Authorized Nuclear Inspector Surry Power Station Serial No.23-258 Docket No. 50-281 Page 2 of 2
ATTACHMENT 1 SURRY UNIT 2 STEAM GENERATOR TUBE INSPECTION REPORT FOR THE SPRING 2023 REFUELING OUTAGE VIRGINIA ELECTRIC AND POWER COMPANY (DOMINION ENERGY VIRGINIA)
Serial No.23-258 Docket No. 50-281
SURRY UNIT 2 STEAM GENERATOR TUBE INSPECTION REPORT FOR THE SPRING 2023 REFUELING OUTAGE Serial No.23-258 Docket No. 50-281 page 1 of 34 The following satisfies the Surry Power Station Technical Specification (TS) reporting requirement section 6.6.A.3. During the Surry Unit 2 Spring 2023 End-Of-Cycle 31 (EOC31) refueling outage, Steam Generator (SG) inspections were completed in accordance with TS 6.4.Q for all three SGs, designated as SG-A, SG-B, and SG-C. Unit 2 exceeded 200°F on June 06, 2023; therefore, this report is required to be submitted by December 03, 2023.
All three SGs were last inspected during the Fall 2021 refueling outage (EOC30). Just prior to the EOC30 shut down, all SGs had a cumulative operating time of 398.4 EFPM. Over cycle 31, the SGs operated for an additional 16.5 EFPM.
Therefore, at the time of this inspection (EOC31 ), the Unit 2 SGs had a cumulative operating time of approximately 415 EFPM since the first in-service inspection.
The three Surry Unit 2 steam generators are replacement Model 51 F lower assemblies (i.e.,
tube bundle, lower shell, and channel head) and primary moisture separator assemblies (F-type). They were replaced in 1980. The moisture separators were subsequently upgraded to support a core power up-rate implemented in 1995. The feedrings were replaced in 2011.
Each of the three SGs were fabricated with 3,342 Thermally Treated Alloy 600 tubing, with nominal 0.875" OD x 0.050" wall thickness.
The seven broached quatrefoil support plates are fabricated from 405 Stainless Steel.
Figure 10 contains a schematic depicting the general arrangement of the steam generators without dimensions.
The Disk Stack in the Feedwater Regulating Valve, detailed in the previous Steam Generator Tube Inspection Report, provides an effective barrier against foreign objects (in the feedwater supply) from entering the steam generators. However, it is believed that the legacy foreign material on the top of the tubesheet had been introduced into the steam generators from the previously mentioned maintenance activities performed in the steam drums.
The Unit 2 steam generators have experienced no reportable primary to secondary leakage since the forced shutdown of June 1986 and operate with a nominal hot leg temperature of 604°F.
Each of the Surry Unit 2 SGs was screened to identify any low row indications of improper heat treatment. None were identified. All the SGs were also screened for long row indications of improper heat treatment (-2 sigma tubes) and associated high residual stress. This evaluation identified 0, 2, and 14 tubes in SGs A, B, and C, respectively, which may have been improperly heat treated. Table 1 provides a listing of tubes that have been identified through screening as possibly containing high residual stress due to an improper heat treatment.
These tubes were examined full length using the bobbin and array probes and closely scrutinized during the analysis process.
There were no deviations taken from Mandatory and/or Needed (Shall) requirements important to tube integrity from the EPRI Guidelines referenced by NEI 97-06 during the examination or the cycles preceding the EOC31 examination.
Table 1: Tubes with Potentially High Residual Stress SG Row Column No. Tubes A
None 0
B 17 71 B
17 78 2
C 14 7
C 23 10 C
23 31 C
23 87 C
24 15 C
24 16 C
25 11 14 C
25 30 C
26 10 C
27 15 C
27 16 C
27 77 C
32 15 C
32 24 Serial No.23-258 Docket No. 50-281 page 2 of 34 In the discussion below, Bold Italicized wording represents TS verbiage and the required information is provided directly below each reporting requirement.
A list of acronyms is contained in Table 17 at the end of this report.
A report shall be submitted within 180 days after Tavg exceeds 200°F following completion of an inspection performed in accordance with the Specification 6.4.Q, "Steam Generator (SG) Program." The report shall include:
- a. The scope of inspections performed on each SG Primary Side The in-service tubing in each SG was inspected with bobbin coil probes over their full length except for the Row 1 and 2 U-bends, which were examined with a +Point' rotating probe. An array probe examination was conducted on 100% of the tubes at the hot leg and cold leg tubesheets. The extent of the array probe tubesheet examinations was from the first support structure located above the tubesheet down to the H-star dimension.
Note that the permanent alternate repair criteria (PARC), Technical Specification (TS 6.4.Q),
eliminates the need to analyze the Surry SG tubing for degradation in the region below the H-star dimension which is 17.89 inches below the top of the tubesheet. It also eliminates the need to plug tubes if the only repairable degradation is located below the H-star dimension.
All high residual stress (HRS) tubes in SGs B and C (SG-A does not have HRS tubes) were examined full length with both Bobbin and Array probes due to the increased susceptibility of Stress Corrosion Cracking.
In addition to the base scope, a preplanned special interest scope was developed for the EOC31 inspection, which includes a sample of previously identified dents, dings, manufacturing
Serial No.23-258 Docket No. 50-281 page 3 of 34 burnish marks, volumetric indications, and wear (excluding AVB wear).
The EOC31 preplanned special interest strategy was identical to the preplanned EOC30 special interest scope.
The specific dent/ding scope performed during the EOC31 inspection included 100% of all dents/dings.:: 2 Volts located in the hot leg straight section and 100% of all dents/dings.:: 5 Volts in the U-bend and cold-leg sections of the tubes.
It should be noted that both terms Dent and Ding refer to a plastic deformation of the tube that results in a reduction in the tube diameter. The two different terms were used to differentiate between the location of the signals.
Historically (early generation designs) the term dent referred to local tube diameter reductions due to corrosion products from carbon steel (typically, drilled carbon steel tube support plates).
The term ding referred to local tube diameter reductions due to mechanical means (manufacturing, vibration, incidents during maintenance activities, or impact from foreign objects).
Since the eddy current signals from both dents and dings are similar, the location of the indication was used to differentiate which term was used (dent for indications at supports and ding for all free span indications).
At Surry Power Station, the referenced dent signals do not represent the same phenomena as classical denting on older generation units caused by drilled carbon steel support plate corrosion damage. Since the Surry units are not similar in design (i.e., quatrefoil stainless steel tube support plate design vs. drilled hole carbon steel tube support plate design) these same "denting" issues do not directly apply to the Surry units. Tube support plate areas are not susceptible to denting caused by corrosion of the tube support plates.
However, the historical nomenclature assigned to these signals has existed in the database since the steam generators were installed and has remained unchanged since that time.
No scope expansions were required; however, the base scope was augmented with additional rotating probe (including magnetically bias probes) to resolve ambiguous indications consistent with the special interest criteria.
The primary side work scope also included video/ visual examinations (as-found/ as-left) of all channel heads (hot leg and cold leg) specifically including:
All plugs Tube-to-tubesheet welds Stub runner and divider plate Stub runner to divider plate welds Stub runner to tubesheet clad weld Divider plate-to-channel head clad weld Tubesheet cladding Closure ring welds Entire bowl cladding with the bowl effectively dry During the Surry 2R31 outage, an as found visual inspection of each steam generator's channel head inside surface was performed in accordance with NSAL-12-1 Rev. 1 for evidence of discoloration, which could indicate a breech in the stainless-steel cladding.
A breech in the channel head bowl cladding is necessary for wastage of the channel head base material to occur.
In the hot-leg plenum of steam generator SG-8 a dime-size area of discoloration was observed. Since the discoloration could be caused by corrosion of the carbon steel base metal,
Serial No.23-258 Docket No. 50-281 page 4 of 34 residue of the discolored area was collected and tested using an energy dispersive spectroscopy system with a scanning electron microscope providing the energy excitation source.
The microanalytical testing revealed that most of the particles captured to be mainly iron, chromium, nickel, and zirconium-based.
Elemental mapping also detected oxygen with each type of fragment, indicating that the elements were most likely in an oxide form.
The iron, nickel, and chromium would represent normal oxidation products from 300 series stainless steel material, while the zirconium presumably would originate from the fuel assemblies.
The results from the testing are as expected for "normal" oxidation products along the inside of RCS components.
Corrosion of the underlying low alloy carbon steel portion of the steam generator would have shown primarily iron with little or no nickel and chromium and certainly no zirconium.
Based on these results, it would appear that either the residue does not represent corrosion of carbon steel material, or that the corrosion residue from any breach was so thin that during the collection process, it was mixed with the normal oxidation product present along the surface.
In addition to the microanalytical test, a volumetric ultrasonic examination was performed from the channel head outside surface to examine for evidence of carbon steel base material wastage.
According to plant drawings, the nominal wall thickness of the carbon steel base material is 5.2 inches. A 10-inch by 11-inch area centered on the location of the discoloration observed in the channel head cladding was scanned with no evidence of wastage identified.
The lowest thickness reading observed was 6.55 inches.
Since the rate of carbon steel corrosion during operation, with very low oxygen in the primary coolant, is much lower than that during shutdown conditions when the material could be exposed to air, corrosion would not impact the structural integrity of the channel head base material during the remaining life of the component.
(The Surry Unit 2 steam generators are scheduled to be replaced in 6 years.)
No structural analysis was required during 2R31 since no base material wastage was observed.
Another primary side cladding examination is required to be performed after a maximum of 3 cycles of operation.
Secondary Side During the EOC31 examination, the following secondary side activities were performed in all three SGs:
Top of tubesheet water lancing Post-lancing visual examination of the tube bundle from the entire periphery Visual examination of historical foreign object-related locations Visual investigation of any accessible locations having eddy current signals potentially related to foreign objects, and removal of retrievable foreign objects.
No steam drum examinations were performed during the EOC31 inspection.
All secondary side examinations were performed satisfactorily with no degradation detected and no foreign objects that could challenge tube integrity are known to remain in the SGs.
- b. Degradation mechanisms found Serial No.23-258 Docket No. 50-281 page 5 of 34 During the EOC31 examination, anti-vibration bar (AVB) wear, tube support plate (TSP) wear, flow distribution baffle (FOB) wear, and legacy foreign object wear were detected during the SG tube examination.
- c. Nondestructive examination techniques utilized for each degradation mechanism The inspection program focused on the degradation mechanisms listed in Table 2 and utilized the referenced eddy current techniques.
Table 2 - Inspection Method for Applicable Degradation Mechanism Classification Degradation Location Probe Type Mechanism Existinq Wear Anti-Vibration Bars Bobbin - Detection and Sizinq Existing Tube Wear (Foreign Freespan and TTS Bobbin and Array - Detection Objects)
+Point' - SizinQ Existing Wear Tube Support Plate (TSP)
Bobbin - Detection
+Point' - Sizinq Existing Wear Flow Distribution Baffle (FOB)
Bobbin - Detection
+Point' - SizinQ Existing Gire. PWSCC Hot Leg TTS and Array - Detection Expansion Transition (EZ)
+Point' - Sizinq Existing Axial PWSCC Tubesheet Overexpansions (OXP)
Array - Detection
+Point' - SizinQ Existing OD Pitting Top-of-Tubesheet (TTS)
Bobbin and Array - Detection
+Point' - Sizina ExistinQ PWSCC Tube Ends N/A*
Potential ODSCC, PWSCC Row 1 and 2 U-bends
+Point' - Detection and Sizinq Potential Axial ODSCC Freespan and Tube Supports Bobbin - Detection
+Point' - Sizinq Potential Axial/ Gire. ODSCC, Hot Leg TTS Array - Detection Axial PWSCC
+Point' - Sizing Bulges, Dents, Manufacturing Array, Bobbin and +Point' -
Potential ODSCC, PWSCC Anomalies, and Near Tubesheet Detection Overexpansions (OVR)
+Point' - Sizinq Potential ODSCC Tubesheet Crevice in Tubes With N/A**
NTE Potential Tube Sliooaqe Within Tubesheet Bobbin - Detection Potential ODSCC, PWSCC High Residual Stress Tubes Bobbin and Array - Detection
+Point' - SizinQ Inspection not required per technical specification alternate repair criteria All tubes with no tubesheet expansion (NTE) have previously been plugged
Serial No.23-258 Docket No. 50-281 page 6 of 34
- d. Location, orientation (if linear), and measured sizes (if available) of service induced indications As stated in the (b) response above, anti-vibration bar (AVB) wear, tube support plate (TSP) wear, flow distribution baffle (FDB) wear, and legacy foreign object wear were detected during the EOC31 SG tube inspection.
AVB Wear In total, 123 AVB wear indications in 85 tubes were identified among all three SGs during EOC31. Of these, 101 indications in 77 tubes were sized <20% TW. None of the identified flaws exceeded the Technical Specification plugging limit (40% TW) and no tubes were plugged due to AVB wear.
The maximum reported depth was 33% TW (reported in tube SG-C R25-C27 at AV2).
There was one newly reported AVB wear indication during EOC31 (SG-C tube 40-29 at AV2), and there were two AVB wear indications reported in EOC30 that were not reportable (INR) during EOC31.
A listing of all 22 indications of AVB Wear ;:: 20% TW is contained in Table 3 and the 101 indications of AVB Wear :5 20% TW is contained in Table 4.
Table 3: Surry 2 EOC31 Inspection Summary-AVB Wear Indications ~20%TW Wear Depth (% TW)
Amplitude ETSS 96041.1 SG Row Col AVB No.
(Volts)
Previous Current EOC30 EOC31 A
26 86 AV3 1.03 23 21 A
36 62 AV2 1.48 28 28 A
36 62 AV4 2.01 33 31 A
38 72 AV4 1.39 27 27 A
38 74 AV4 0.97 23 20 A
40 65 AV2 1.08 25 24 EOC30 EOC31 B
24 57 AV1 1.19 18 20 B
38 51 AV4 1.14 19 20 B
38 74 AV4 1.26 23 21 EOC30 EOC31 C
25 27 AV2 2.69 33 33 C
25 29 AV3 1.02 24 22 C
26 26 AV3 0.90 19 20 C
31 69 AV2 1.03 21 23 C
33 59 AV3 0.85 20 20 C
33 68 AV1 0.89 21 20
SG Row Col AVB No.
C 38 30 AV2 C
39 53 AV3 C
39 55 AV3 C
39 55 AV4 C
40 33 AV2 C
40 33 AV3 C
43 61 AV1 Amplitude (Volts) 0.88 1.69 1.42 1.32 1.25 1.28 1.03 Serial No.23-258 Docket No. 50-281 page 7 of 34 Wear Depth (% TW)
ETSS 96041.1 Previous Current 21 20 30 28 26 24 25 23 26 25 25 25 23 22 Table 4: Surry 2 EOC31 Inspection Summary-AVB Wear Indications <20%TW Wear Depth (% TW)
Amplitude ETSS 96041.1 SG Row Col AVB No.
(Volts)
Previous Current EOC30 EOC31 A
25 57 AV2 0.61 20 15 A
26 9
AV4 0.37 13 10 A
29 28 AV3 0.39 15 10 A
29 70 AV2 0.44 13 14 A
30 12 AV1 0.30 9
9 A
30 64 AV2 0.33 12 11 A
33 26 AV4 0.34 10 10 A
36 62 AV3 0.60 18 17 A
36 66 AV2 0.61 17 15 A
36 66 AV3 0.60 16 15 A
37 20 AV1 0.43 13 11 A
37 20 AV4 0.42 13 11 A
38 57 AV1 0.66 17 18 A
38 70 AV3 0.33 15 9
A 38 72 AV3 0.39 16 12 A
40 25 AV4 0.39 14 11 A
40 49 AV1 0.41 13 13 A
40 49 AV2 0.36 12 12 A
40 49 AV3 0.44 13 14 A
40 51 AV2 0.41 13 11
SG Row Col AVB No.
A 40 65 AV3 A
40 65 AV4 A
40 66 AV3 A
42 62 AV3 A
44 35 AV1 A
44 38 AV2 A
45 51 AV1 A
46 45 AV1 A
46 49 AV1 A
46 49 AV2 B
26 64 AV2 B
31 58 AV2 B
32 69 AV2 B
33 60 AV3 B
35 78 AV3 B
37 71 AV3 B
37 75 AV3 B
38 74 AV1 B
38 74 AV2 B
44 60 AV2 B
45 57 AV1 C
24 8
AV4 C
25 9
AV1 C
25 9
AV3 C
25 27 AV1 C
25 27 AV3 C
25 29 AV2 C
26 26 AV4 C
26 39 AV3 C
27 84 AV4 C
31 65 AV2 Amplitude (Volts) 0.46 0.62 0.51 0.43 0.53 0.33 0.34 0.43 0.52 0.37 1.37 0.78 0.43 0.93 0.39 0.44 0.47 0.85 1.09 0.91 0.77 0.47 0.41 0.49 0.83 0.58 0.33 0.75 0.84 0.28 0.35 Serial No.23-258 Docket No. 50-281 page 8 of 34 Wear Depth (% TW)
ETSS 96041.1 Previous Current 17 14 18 17 14 14 13 12 13 13 10 11 11 9
13 13 16 15 13 12 EOC30 EOC31 20 19 15 15 12 10 17 17 13 9
14 10 13 10 18 16 20 19 16 14 10 12 EOC30 EOC31 12 13 14 11 12 13 17 19 17 15 13 10 20 18 18 19 8
10 13 11
SG Row Col AVB No.
C 31 69 AV3 C
31 75 AV2 C
31 75 AV3 C
31 75 AV4 C
33 59 AV4 C
33 67 AV3 C
33 68 AV2 C
33 69 AV1 C
33 69 AV2 C
33 70 AV1 C
33 70 AV3 C
34 29 AV3 C
34 29 AV4 C
34 79 AV1 C
35 77 AV2 C
35 77 AV3 C
36 73 AV3 C
37 63 AV2 C
37 73 AV3 C
37 75 AV3 C
38 28 AV1 C
38 28 AV3 C
38 43 AV3 C
38 67 AV3 C
38 73 AV1 C
38 73 AV2 C
38 74 AV2 C
39 50 AV3 C
39 55 AV3 C
39 71 AV3 C
39 72 AV4 C
40 29 AV2 C
40 63 AV2 Amplitude (Volts) 0.63 0.40 0.68 0.63 0.38 0.49 0.84 0.25 0.39 0.37 0.76 0.50 0.65 0.52 0.34 0.28 0.22 0.45 0.70 0.38 0.28 0.65 0.50 0.30 0.49 0.57 0.44 0.65 0.61 0.40 0.35 0.49 0.32 Serial No.23-258 Docket No. 50-281 page 9 of 34 Wear Depth (% TW)
ETSS 96041.1 Previous Current 16 17 15 10 17 15 17 14 13 11 15 12 22 19 11 8
12 12 15 9
20 16 19 14 21 17 15 12 12 10 12 9
7 6
13 11 20 18 13 10 11 9
21 17 15 14 12 9
16 12 16 13 14 11 17 15 16 14 12 10 11 10 N/A 13 14 10
SG Row Col AVB No.
C 40 63 AV3 C
40 63 AV4 C
40 66 AV3 C
41 64 AV1 C
41 66 AV3 C
42 42 AV3 C
43 39 AV2 C
43 63 AV1 C
44 51 AV2 C
44 51 AV3 C
44 61 AV1 C
46 45 AV2 C
46 45 AV3 C
46 46 AV1 C
46 46 AV2 C
46 46 AV3 C
46 46 AV4 Volumetric Non-AVB Wear Amplitude (Volts) 0.61 0.68 0.33 0.25 0.72 0.25 0.43 0.64 0.36 0.40 0.34 0.50 0.34 0.40 0.40 0.30 0.44 Serial No.23-258 Docket No. 50-281 page 10 of 34 Wear Depth (% TW)
ETSS 96041.1 Previous Current 19 16 21 17 13 9
12 8
20 16 10 9
16 12 17 14 13 12 14 13 13 10 13 13 11 10 10 11 17 11 11 9
13 12 Bobbin probe or array probe inspections of in-service tubes identified 67 indications of volumetric tube degradation not related to AVB wear, in 60 tubes among all three SGs.
The measured flaw depths range from 5% TW to 34% TW. Sizing of these indications was performed with a +Point' rotating coil. Table 5 lists the 67 Non-AVB Wear indications with recorded wall losses. The sizing techniques used to determine the dimensions of the flaws are also identified in the table.
There were no newly reported Non-AVB wear indications during 2R31 (all 67 indications are repeat indications) and none of the 67 repeat indications exhibited signal change indicative of wear growth.
Nine of the indications resulted from support structure wear (TSP or baffle plate) and all the remaining 58 indications are attributed to foreign object wear, with no foreign object remaining in the vicinity of the wear indication.
Figure 1 through Figure 4 provide the 95/50 CM limit curves for flaws sized with ETSS 27901.1, 27902.1, 27905.1, and 96910.1 respectively. The CM curves represent the structural integrity
Serial No.23-258 Docket No. 50-281 page 11 of 34 performance criteria derived by conservatively accounting for material property uncertainties, model uncertainties, and NOE depth sizing uncertainties. The uncertainties were combined using Monte Carlo techniques.
Because each flaw plotted in Figure 1 through Figure 4 lies below the CM limit curve, each flaw satisfies the structural integrity performance criterion.
Table 5: Summary of Non-A VB Wear Volumetric Degradation Max Axial Circ Initially SG Row Col Location ETSS Depth Length Length Cause
(%TW)
(in)
(in)
Volts Reported TSC +0.62" 27901.1 17 0.29 0.45 0.13 2015 Foreign Object A
4 37 TSC +1.5" 27901.1 25 0.32 0.26 0.23 2015 Foreign Object A
6 60 05H -0.58" 96910.1 7
0.27 0.29 0.26 2009 TSP Wear A
11 45 TSH +0.98" 27901.1 22 0.27 0.21 0.21 2012 Foreign Object A
15 16 TSH +0.25" 27901.1 22 0.29 0.37 0.19 2012 Foreign Object A
17 16 TSH -0.10" 27901.1 26 0.35 0.48 0.24 2002 Foreign Object A
18 16 TSH -0.12" 27901.1 24 0.29 0.42 0.21 2002 Foreign Object A
32 27 TSC-0.05" 27901.1 16 0.19 0.32 0.12 2006 Foreign Object A
33 27 TSC-0.04" 27901.1 23 0.27 0.26 0.20 2006 Foreign Object A
39 24 TSH +0.43" 27901.1 16 0.32 0.37 0.12 2009 Foreign Object A
42 52 TSC +0.18" 27901.1 16 0.16 0.26 0.12 2009 Foreign Object A
43 61 BPH +0.53" 27901.1 20 0.29 0.32 0.17 2009 Foreign Object A
43 64 BPH +0.66" 27901.1 20 0.27 0.26 0.17 2009 Foreign Object B
10 58 03H-0.66" 96910.1 22 0.29 0.32 0.52 2021 TSP Wear TSC + 0.01" 27901.1 23 0.24 0.26 0.2 2017 Foreign Object B
18 81 TSC + 0.26" 27901.1 20 0.4 0.29 0.17 2017 Foreign Object B
23 82 TSH - 0.18" 27901.1 19 0.29 0.21 0.15 2003 Foreign Object B
34 66 TSC + 0.18" 27901.1 21 0.27 0.37 0.18 2017 Foreign Object B
36 26 TSC + 0.04" 27905.1 27 0.27 0.34 0.85 2008 Foreign Object B
37 27 TSC - 0.01" 27901.1 25 0.21 0.32 0.21 2008 Foreign Object B
41 42 TSC + 0.86" 27901.1 12 0.32 0.37 0.09 2017 Foreign Object B
42 40 03H-0.55" 96910.1 25 0.24 0.37 0.58 2021 TSP Wear B
42 42 TSC-0.18" 27901.1 27 0.32 0.32 0.25 2014 Foreign Object B
46 52 TSC + 9.06" 27901.1 12 0.35 0.26 0.09 2017 Foreign Object Foreign Object Remaining No No N/A No No No No No No No No No No N/A No No No No No No No N/A No No In Situ Tested No No No No No No No No No No No No No No No No No No No No No No No No Serial No.23-258 Docket No. 50-281 page 12 of 34 Plugged Stabilized No No No No No No No No No No No No No No No No No No No No No No No No
Max Axial SG Row Col Location ETSS Depth Length
(%TW)
(in) 03C +0.53" 96910.1 8
0.19 C
3 72 03C+0.51" 96910.1 11 0.21 C
28 22 TSH +0.14" 27901.1 28 0.21 TSH +0.55" 27901.1 25 0.35 C
28 23 TSH +0.25" 27901.1 27 0.27 C
28 71 TSH +0.17" 27901.1 20 0.24 C
28 84 03H +0.31" 96910.1 5
0.16 C
30 48 BPH +0.50" 27901.1 18 0.16 C
30 74 TSH +6.22" 27901.1 14 0.27 C
32 36 BPH +0.63" 27901.1 15 0.21 C
33 17 TSH +2.71" 27901.1 16 0.32 C
34 18 TSH +1.00" 27901.1 19 0.32 C
34 20 TSH +0.92" 27901.1 24 0.29 C
34 74 TSH-0.03" 27901.1 27 0.32 C
35 19 TSH +0.29" 27901.1 28 0.32 C
35 22 TSH +1.04" 27901.1 27 0.4 C
35 30 TSH-0.08" 27901.1 34 0.27 C
36 32 BPH +0.65" 27901.1 18 0.21 C
36 68 TSH-0.06" 27902.1 28 0.51 C
37 31 TSH +0.02" 27901.1 23 0.27 C
37 32 TSH +0.03" 27901.1 20 0.13 C
37 33 TSH +0.04" 27901.1 25 0.29 C
37 34 TSH +0.03" 27901.1 25 0.24 C
37 35 BPH +0.64" 27901.1 31 0.27 C
37 54 TSH +0.04" 27901.1 23 0.24 Circ Initially Length Cause (in)
Volts Reported 0.29 0.13 2011 TSP Wear 0.29 0.2 2011 TSP Wear 0.32 0.26 2014 Foreign Object 0.32 0.22 2014 Foreign Object 0.32 0.25 2014 Foreign Object 0.32 0.17 2009 Foreign Object 0.26 0.12 2014 TSP Wear 0.26 0.14 2015 Foreign Object 0.21 0.1 2014 Foreign Object 0.29 0.11 2009 Foreign Object 0.34 0.12 2005 Foreign Object 0.37 0.15 2005 Foreign Object 0.34 0.21 2005 Foreign Object 0.32 0.25 2005 Foreign Object 0.37 0.26 2005 Foreign Object 0.29 0.25 2005 Foreign Object 0.32 0.36 2005 Foreign Object 0.26 0.13 2015 Foreign Object 0.48 0.73 2005 Foreign Object 0.26 0.2 2011 Foreign Object 0.21 0.16 2011 Foreign Object 0.37 0.23 2011 Foreign Object 0.32 0.22 2009 Foreign Object 0.37 0.32 2005 Foreign Object 0.29 0.2 2005 Foreign Object Foreign Object Remaining N/A N/A No No No No N/A No No No No No No No No No No No No No No No No No No In Situ Tested No No No No No No No No No No No No No No No No No No No No No No No No No Serial No.23-258 Docket No. 50-281 page 13 of 34 Plugged Stabilized No No No No No No No No No No No No No No No No No No No No No No No No No
Max Axial Circ SG Row Col Location ETSS Depth Length Length
(%TW)
(in)
(in)
C 37 73 07C -0.67" 96910.1 17 0.64 0.4 C
38 32 BPH +0.63" 27901.1 24 0.27 0.26 C
38 53 TSH +0.04" 27901.1 20 0.24 0.26 BPH +0.57" 27901.1 24 0.27 0.32 C
39 32 BPH +0.60" 27901.1 18 0.27 0.26 C
39 34 BPH +0.63" 27901.1 23 0.27 0.29 C
40 34 BPH +0.65" 27901.1 19 0.29 0.29 C
40 60 BPH +0.98" 27901.1 12 0.27 0.32 C
44 42 TSH-0.03" 27901.1 20 0.27 0.26 C
44 43 TSH +0.04" 27901.1 22 0.24 0.26 C
44 47 TSH-0.09" 27901.1 25 0.24 0.32 C
44 60 BPH +0.09" 96910.1 6
0.43 0.26 C
45 42 TSH +0.15" 27901.1 14 0.21 0.21 TSH +0.16" 27901.1 20 0.24 0.37 C
45 43 TSH +0.13" 27901.1 23 0.27 0.26 TSH +0.55" 27901.1 16 0.27 0.26 C
45 47 TSH +0.01" 27901.1 23 0.27 0.26 C
45 49 01C +0.35" 96910.1 10 0.59 0.26 Initially Cause Volts Reported 0.34 2005 TSP Wear 0.21 2011 Foreign Object 0.16 2005 Foreign Object 0.21 2011 Foreign Object 0.14 2011 Foreign Object 0.2 2011 Foreign Object 0.14 2011 Foreign Object 0.09 2018 Foreign Object 0.16 2005 Foreign Object 0.19 2005 Foreign Object 0.22 2005 Foreign Object 0.29 2015 FOB Wear 0.1 2015 Foreign Object 0.16 2005 Foreign Object 0.2 2005 Foreign Object 0.12 2005 Foreign Object 0.2 2005 Foreign Object 0.18 2018 TSP Wear Foreign Object Remaining N/A No No No No No No No No No No N/A No No No No No N/A In Situ Tested No No No No No No No No No No No No No No No No No No Serial No.23-258 Docket No. 50-281 page 14 of 34 Plugged Stabilized No No No No No No No No No No No No No No No No No No
Foreign Objects Serial No.23-258 Docket No. 50-281 page 15 of 34 A significant effort was expended on the removal of legacy foreign objects from the secondary side of all three SGs during the EOC30 (fall 2021) outage. It is believed that the legacy foreign material on the top of the tubesheet had been introduced into the SGs from the maintenance activities performed in the steam drums many years before.
In previous outages, multiple small pieces of wire had been detected, which had migrated into low flow areas forming localized entangled wire masses. These wire masses had been present in some of the SGs for more than 10 years without causing any tube wall degradation. The wires were evaluated and determined to be made of 304 stainless steel approximately 0.5" long and 0.012" in diameter. This is a diameter common for wire bristles associated with cleaning tools such as small wire brush wheels.
Individually, these small wires don't present a threat to tube integrity because they lack the mass required to penetrate the tube wall and therefore considered to be benign.
During the EOC30 outage an enhanced tubesheet cleaning process was performed in all three steam generators to remove debris and legacy foreign objects. The as-left condition also provided a known baseline to positively identify any new foreign object intrusion during future operational cycles.
The foreign objects identified in Table 6 below include all foreign objects removed during the EOC31 FOSAR and water lancing activities. Foreign objects known to be remaining in the steam generators, at the conclusion of the EOC31 outage, are also identified.
Sludge removed during the EOC31 water lance process was:
SG-A = 3 lbs.
SG-B = 5 lbs.
SG-C = 4.5 lbs.
Table 6: Foreign Object Highlights at EOC31 SG-2023 ECT Item#
Description Affected Tubes Configuration Results Estimated Size 2012 piece of Flexitallic Gasket in flexitallic gasket A-1 sludge formation. At R18-C46 embedded in PLP
~0.6" 2023 flex gasket was TSC +0.10 sludge formation no longer present.
and fixed to tube/
tubesheet Deposit: Not Legacy small LPS Historical LPS deposit Recorded and R10-C47, Rl 1-C47 on tube OD and A-2 and 2023 Flat metallic TSC +0.60 Flat metallic object 2023 Flat object:
metallic object PLPs
~ 1.5" long Fixity Fixed Fixed Flat metallic object Removed Serial No.23-258 Docket No. 50-281 page 16 of 34 2023 Disposition During 2023 a legacy tube and its associated bounding tubes were examined by ECT. The only reported PLP was a legacy PLP from 2012. No tube wear was reported. FOSAR confirmed that the legacy piece of flex is no longer present at the sludge formation. At the next ISI continue to monitor the affected and bounding tubes using ECT and SSL During 2023 the affected and bounding tubes associated with the historical tube deposit were examined by ECT. The legacy LPS continued to be reported. A flat metallic object was also removed from the location. No tube wear indications were reported. At the next ISI, continue to monitor the affected and bounding tubes using ECT and SSL
SG-2023 ECT Item#
Description Affected Tubes Configuration Results R21-C10, R22-C10 2003 bolt like B-1 Legacy R22-Cl 1, R21-Cl 1 object. Four Bounding Bolt Like Object affected tubes tubesNDD 02C+0.65 plugged/stabilized R44-C46, R43-C46, Partial shank of B-2 Partial shank of bolt NDD R43-C45, R44-C45 bolt 2017 sludge rock R5-C88, R6-C88 and 2018-disc C-1 Sludge Rock/ Disc shaped object LPS Shaped Object R6-C89 TSC +0.00 affixed to the tubesheet Estimated Size Fixity 1/2" X 1.5" Remains in SG 1/4" dia. x 1/4" Removed long
-0.4" Fixed Serial No.23-258 Docket No. 50-281 page 17 of 34 2023 Disposition During 2003 four tubes were plugged for a bolt like foreign object. During 2023, the tubes bounding the four plugged tubes were examined by ECT. No PLP or tube wear indications were reported. FOSAR was not able to access the location. At the next ISI continue to monitor the bounding tubes using ECT.
During 2023 SSI identified a partial bolt shank that appeared to be broken off a 1/4"-20 bolt. There were no associated ECT indications (wear or PLPs). The item was removed. Item closed out and no further actions required.
During 2023 the legacy sludge rock and disc-shaped object were both detected by ECT and FOSAR. No tube wear was detected and FOSAR confirmed that the rock/object are still fixed in place. At the next ISI continue to monitor the affected and bounding tubes using ECT and SSL
SG-2023 ECT Item#
Description Affected Tubes Configuration Results R34-C66, R35-C66, C-2 TTS R35-C67 Legacy TTS PLPs Deposit Bridging TSH+0.00 Deposit Bridging R28-C68, R28-C69, 2009 metal nut R27-C70, R27-C71, embedded in hard C-3 Metal Nut R29-C71 deposit PLPs TSH +0.11 formations R24-C63, R24-C62 2009 EWM that C-4 Entangled Wire R29-C62, R29-C63 in 2018 was LPM Mass(EWM) pushed from row-TSH +0.00 24 to row-29 Estimated Size Fixity
~0.4" Fixed 0.36" length 0.25" depth Fixed 0.36" width
~0.5" Fixed diameter Serial No.23-258 Docket No. 50-281 page 18 of 34 2023 Disposition During 2021 Item #44 tubes with WAR (36-68) and PLPs (35-67, 35-66, 34-66) are the same tubes for item #57. The item causing WAR was removed in 2018 and WAR depth has not changed in 2021 and 2023. PLPs due to deposit bridging. At the next ISi continue to monitor with ECT and SSL During 2023 the legacy metal nut was detected by both ECT and FOSAR. No tube wear was reported and FOSAR confirmed the metal nut is still fixed in place.
At the next ISi continue to monitor the affected and bounding tubes using ECT and SSL 2R28 wire mass in hard deposit observed, would not push with Delrin guide; broken up and moved 5 rows by lancing to 29-62, 29-63. During 2R30 broke this area up and nothing remained but a few small wires embedded in sludge pile. During 2R3 l it remains in place unchanged and not disturbed. No tube wear reported. At next ISi continue to monitor with ECT and SSL
SG-2023 ECT Item#
Description Affected Tubes Configuration Results R36-C51, R35-C51 2021 Entangled Wire R34-C51, R36-C52 C-5 Entangled Wire NDD Mass(EWM)
R35-C52, R34-C52 Mass(EWM)
TSH +0.50 2021 Embedded Wire in R34-C51, R34-C50 Wire like object C-6 NDD hard sludge TSH +0.25 embedded in hard sludge Sludge and R31-C54, R31-C55 C-7 Entangled wire mass TSH+0.00 2023 Wire mass NDD (EWM)
Estimated Size Fixity Partially
-3 tubes Fixed in by 2 tubes Place 1.50" length 0.12" depth Fixed 0.12" width Spanning Multiple Fixed tubes Serial No.23-258 Docket No. 50-281 page 19 of 34 2023 Disposition During 2021 FOSAR identified a EWM ( originally logged as being part of POTS item #72 but broke out as separate POTS item #84).
FOSAR broke the mass apart for subsequent removal by lancing.
During 2023 some remnants of the EWM still remain on the TTS but is not considered a threat to tube integrity. ECT reported no associated PLP or tube wear indications. At the next ISI continue to monitor the affected and bounding tubes using ECT.
During 2021 a wire like object was found by FOSAR. Subsequent removal attempts showed the wire to be embedded in hard sludge at the TTS. During 2023, ECT reported no PLP or tube wear indications. FOSAR confirmed EWM location. At the next ISI continue to monitor the affected and bounding tubes using ECT and SSL During 2R31 sludge and EWM found and verified fixed in place.
ECTwas NDD. No tube wear. At the next ISI continue to monitor with ECT and SSL
Serial No.23-258 Docket No. 50-281 page 20 of 34
- e. Number of tubes plugged during the inspection outage for each degradation mechanism One tube in SG-A was plugged on a discretionary basis for an expansion transition signal exhibiting a smaller amplitude than the surrounding tubes. No tubes were plugged in SG-B or SG-C.
- f. The number and percentage of tubes plugged to date, and the effective plugging percentage in each steam generator.
Table 7 provides the plugging totals and percentages to date.
Table 7 - Tube Plugging Summary Steam Generator SG-A SG-B SG-C Total Prior to EOC-31 30 20 51 101 Plugged in EOC-31 1
0 0
1 Total 31 20 51 102
% Plu!!!!ed 0.9%
0.6%
1.5%
1.0%
Since no sleeving has been performed in the Surry Unit 2 steam generators, the effective plugging percentage is the same as the actual plugging percentage.
- g. The results of condition monitoring, including the results of tube pulls and in-situ testing None of the tube degradation identified in Surry Unit 2 SGs during the EOC31 outage violated the structural integrity performance criteria; thereby providing reasonable assurance (since burst and leak are coincident for volumetric degradation) that none of these flaws would have leaked during a limiting design basis accident. Therefore, tube pulls and in-situ pressure testing were not necessary at EOC31.
The Condition Monitoring (CM) Assessment for each detected degradation mechanism was determined using the methodology described below.
Table 8-CM Methodology CM (Mechanism)
Methodoloav Structural Limit Note AVB Wear Mixed Arithmetic/Monte Carlo Structural Limit (61 % TW) 1 Vol (Non-AVB)
Monte Carlo CM Curve 2
Notes;
- 1) For CM, three uncertainties must be considered (NOE, burst relationship, and material properties). The Mixed Arithmetic/Monte Carlo methodology accounts for these uncertainties as follows. The Arithmetic part incorporates NOE uncertainty (ETSS depth sizing regression and 95/50 value of the standard deviation) to arrive at the 95/50 upper bound depth. The Monte Carlo part incorporates burst relationship and material property uncertainties (via a Monte Carlo process) to arrive at the structural limit. If the limiting 95/50 upper bound depth is less than the structural limit, CM is met.
Serial No.23-258 Docket No. 50-281 page 21 of 34
- 2) The CM curve, itself, has built into it all three uncertainties using Monte Carlo methods.
Therefore, no arithmetic correction for NDE sizing uncertainty is required since it's built into the CM curve.
AVB Wear A mixed Arithmetic/Monte Carlo methodology was used for CM of AVB wear.
Degradation Mechanism Maximum Limiting 95%/50%
CM Limit Depth (wear)
NDE Depth Upper Bound Deoth AVB Wear 33%
39.7%
61%
Since the limiting 95/50 upper bound depth (39. 7% TW) does not exceed the conservative structural limit of 61%TW, it is concluded that none of the AVB wear flaws exceeded the structural limit at EOC31. Note that the 61 % TW structural limit was developed under the guidance of Regulatory Guide 1.121 which considers both pressure and non-pressure loads.
Volumetric (Non-AVB Wear)
As indicated above, a Monte Carlo methodology was used for CM of the volumetric indications not attributed to AVB wear.
Figure 1 through Figure 4 provide the 95/50 CM limit curves for indications sized with ETSSs 27901.1, 27902.1, 27905.1, and 96910.1 respectively. Since all indications plot below the CM limit curves, CM was met at EOC31.
Figure 1: CM Curve for Flaws Sized w/ETSS 27901.1 - Model: Axial Thinning w/Limited Circumferential Extent 100 90 80 70
~
60 e:.
.c Q..,
50 C
E 40 E
- c.,
- IE 30 w
C z 20 10 0
0.0 I
Ill II I I
T 0.2 0.4 ETSS 27901.1 R1 0.6 0.8 Length, (Inch) 27901.1 R1 1.0 Foreign Object Wear L
1.2 1.4
Figure 2:
100 90 80 -
70
~ 60 c
.c C.
50 C
E 40 E
30 w
C z 20 10 0
0.0 Serial No.23-258 Docket No. 50-281 page 22 of 34 CM Curve for Flaws Sized w/ETSS 27902.1 - Model: Axial Thinning w/Limited Circumferential Extent ETSS 27902.1 R1
-27902.1 R1 Foreign Object Wear 0.2 0.4 0.6 0.8 1.0 1.2 1.4 Length, (Inch)
Figure 3: CM Curve for Flaws Sized w/ETSS 27905.1 - Model: Axial Thinning w/Limited Circumferential Extent 100 ETSS 27905.1 R2 90
-27905.1 R2 Foreign Object Wear 80 70
~ 60 c
.c C.
50 C
E 40 E
30 w
0 z 20 10 0
0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 Length, (Inch)
Serial No.23-258 Docket No. 50-281 page 23 of 34 Figure 4: CM Curve for Flaws Sized w/ ETSS 96910.1 - Model: Axial Thinning w/Limited Circumferential Extent 100 ETSS96910.1 R11 90
-96910.1 R11 TSP / FOB Wear 80 70 *
~ 60 c
.c
- 0.
50 II>
C E
40
- , E
'ic..
30 w
C z
20 10 0
0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 Length, (Inch)
Stress Corrosion Cracking No indications of stress corrosion cracking were identified in any of the Surry Unit 2 steam generators during 2R31.
Operational Assessment Surry Technical Specifications require that the inspection scope, inspection methods, and inspection intervals shall be such as to ensure that SG tube integrity is maintained until the next SG inspection. Therefore, the Dominion SG Program requires that a "forward looking" operational assessment (OA) be performed to determine if the steam generator tubing will continue to meet the structural and leakage integrity requirements at the end of the upcoming operating interval.
The current Technical Specifications require an inspection of each SG at least every 48 effective full power months or at least every other refueling outage (whichever results in more frequent inspections).
However, all existing and potential degradation mechanisms were evaluated for a 3-cycle operating period over a conservative 4.5 EFPY duration. The following sections summarize the evaluations performed for existing degradation mechanisms as well as important potential degradation mechanisms. Table 9 illustrates that the current (EOC31) inspection results are bounded by the previous (EOC30) OA projections; therefore, providing a basis that the OA methodology is sufficient, and adjustments to the current OA methodology are not required.
Table 10 identifies the degradation specific OA methodology.
Table 11 summarizes the EOC34 OA projections with comparisons to the applicable structural and leakage limits.
Serial No.23-258 Docket No. 50-281 page 24 of 34 Table 9: Summary of Prior OA Validation Degradation Fall 2021, EOC30 Spring 2023, EOC31 Operational Operational Assessment Mechanism Projection at EOC31 Assessment Maximum Observed AVB Wear 36%TW 33%TW TSP Wear 30%TW 25%TW Foreign Object Not to exceed Met Wear SIPC and AILPC DNTODSCC Two (2)
This type of sec has never been Cumulative Detections detected at Surry Unit 2 Circumferential Six (6)
This type of sec has never been ODSCC atTTS Cumulative Detections detected at Surry Unit 2 Three (3) PWSCC detections in 2015 Circumferential Six (6) and one ( 1) in 2021, leaving two (2) detections remaining.
PWSCC TTS/ TS Cumulative Detections No PWSCC was detected at EOC31.
Axial ODSCC Two (2)
This type of sec has never been at TSPs Cumulative Detections detected at Surry Unit 2 One (1) PWSCC detection in 2021, Axial PWSCC Six (6) leaving five (5) detections remaining.
TTS/TS Cumulative Detections No PWSCC was detected at EOC31.
Operational Projected: <150 GPO No measurable leakage observed Leakage durinq Cvcle-31 Table 10 - OA Methodoloav OA (Mechanism)
Methodology Structural Limit Note AVB Wear Mixed Arithmetic/Monte Carlo Structural Limit (61 % TW) 1 FO Wear Plant Operatinq Historv TSP/FOB Wear Mixed Arithmetic/Monte Carlo Structural Limit (56.6% TW) 1 Circ PWSCC Fully Probabilistic Multi-Cycle OA Lower 95/50 Burst Pressure > 3~P 2
(TTS/TS)
Axial PWSCC Fully Probabilistic Multi-Cycle OA Lower 95/50 Burst Pressure > 3~P 2
(TTS/TS)
Circ ODSCC Fully Probabilistic Multi-Cycle OA Lower 95/50 Burst Pressure > 3~P 2
(TTS)
Axial ODSCC Fully Probabilistic Multi-Cycle OA Lower 95/50 Burst Pressure > 3~P 2
(TSPs)
Axial ODSCC Fully Probabilistic Multi-Cycle OA Lower 95/50 Burst Pressure > 3~P 2
(DNT/DNG)
- 1) For OA (plug on NOE sizing}, four uncertainties must be considered (NOE, growth, burst relationship, and material properties). The Mixed Arithmetic/Monte Carlo methodology accounts for the four uncertainties as follows. The Arithmetic part accounts for NOE uncertainty by using the ETSS depth sizing regression equation together with a 95/50 value ( of the ETSS standard deviation) to arrive at the limiting BOC % TW value. The limiting BOC % TW value is adjusted
Serial No.23-258 Docket No. 50-281 page 25 of 34 upward for growth allowance/uncertainty (to arrive at the EOC % TW value) and compared to the structural limit. The structural limit has been adjusted for burst relationship and material properties uncertainties using Monte Carlo methods. If the EOC % TW value is less than the structural limit, OA is projected to be met.
- 2) For the Fully Probabilistic Multi-Cycle OA, the lower 95/50 burst pressure must be greater than three times the primary-to-secondary differential pressure (3~P).
Foreign Objects The potential for undetected foreign object wear and the development of new foreign object wear during the ensuing operating intervals in each SG must be considered. It is difficult to predict if, and when, foreign object wear will occur. However, by examining the aggregate operating history of the Surry Unit 2 SGs with respect to foreign object wear, a judgment of the risk can be developed. During the period between 1991 and 2006, the SGs were often operated for three cycles between ECT inspections. Despite the presence of various foreign objects, no foreign object wear exceeding the performance criteria was detected during that period.
Based on Surry and industry operating experience, new foreign material introduced during the upcoming operating period is unlikely to cause structurally significant tube degradation.
However, in the event of such an occurrence, primary to secondary leakage monitoring procedures in place at Surry provide a high degree of confidence of safe unit shutdown without challenging the SIPC or AILPC Table 11 - OA Projected Condition During EOC34*
Structural Integrity Accident Induced Performance Criteria Leakage Performance Degradation Mechanism Criteria EOC34 EOC34 Limit Projection Limit Projection AVB Wear 61%
49.6%TW 470 GPD Zero Maximum Depth Leakaqe TSP/FDB Wear 56.6%
52.8%TW 470 GPD Zero Maximum Depth Leakaqe Pittinq Dormant. No pro*ected pitting.
Circumferential PWSCC within 4470 psi 7314 psi 470 GPD Zero tubesheet expansion Leakage Circumferential ODSCC @
4470 psi 7045 psi 470 GPD Zero TTS Leakaqe Axial PWSCC within the 4470 psi 4626 psi 470 GPD Zero tubesheet Leakage Axial ODSCC @ TSPs 4470 psi 5422 psi 470 GPD Zero Leakage Axial ODSCC @ (DNT/DNG) 4470 psi 5331 psi 470 GPD Zero Leakage
- Although the Operational Assessment is projected to EOC34, an inspection is required to be performed during EOC33 due to the current Technical Specification requirements.
AVB Wear Serial No.23-258 Docket No. 50-281 page 26 of 34 The evaluation requires that structural integrity be demonstrated with a statistical figure of merit of 95% probability and 50% confidence (95/50).
The AVB indications identified during the current inspection were included in the statistical analysis of AVB growth.
The growth rate used for the operational assessment projection was based on the largest upper 95/50 growth rate value among the three steam generators at both EOC30 and EOC31.
The largest upper 95/50 growth rate was taken from SG-B at EOC30 and is 1.878 % TW/EFPY using median ranks and 2.13% TW/EFPY using (mean + 1.645(StdOev.). The 95/50 growth rate was conservatively rounded up to 2.2 % TW/EFPY.
The maximum depth of reported AVB wear returned to service during EOC31 was 33%TW.
Adjusting the 33% TW depth to conservatively account for NOE sizing uncertainty yields a value of 39.7%TW. Therefore, the limiting BOC32 AVB wear depth is 39.7%TW.
Adjusting the BOC32 depth upward to reflect three fuel cycles of growth (4.5 EFPY), yields the end-of-cycle upper bound depth (EOCUBO):
BOC32 = 39.7%TW maximum through-wall depth of in-service AVB wear at the beginning of Cycle 32 EOCUBO = BOC32+(4.5 EFPY)(2.2 % TW/EFPY) end of cycle upper bound depth after three cycles EOCUBO = 49.6% TW The maximum projected EOC34 depth is 49.6%TW which is below the 61%TW structural limit for AVB wear. Therefore, AVB wear is not expected to challenge the SIPC going forward to the next inspection in any Unit 2 SG.
Since AVB wear is not projected to violate the structural performance criteria prior to the next inspection, there is reasonable assurance that the AILPC will not be exceeded prior to the next inspection in any Unit 2 SG.
Volumetric (Non-AVB Wear)
As indicated above, a Mixed Arithmetic/Monte Carlo methodology was used for OA of the volumetric indications not attributed to AVB wear.
The maximum depth of reported TSP/FOB wear returned to service during EOC31 was 25%TW.
Adjusting the 25% TW depth to conservatively account for sizing uncertainty yields a value of 39.3% TW. Therefore, the limiting BOC32 TSP/FOB wear depth is 39.3% TW.
None of the previously reported TSP/FOB wear identified during EOC31 exhibited evidence of growth from the previous inspection. For this OA, a growth rate of 3% TW/EFPY was assumed and applied from EOC31 through EOC34; an assumed duration of 4.5 EFPY. The total growth allowance for TSP/FOB wear is therefore 13.5%TW (i.e., (4.5)(3)). Adjusting the BOC32 depth upward to reflect three fuel cycles of growth, yields the end-of-cycle upper bound depth of 52.8% TW (i.e., 39.3+13.5) which is below the 56.6% TW structural limit for TSP/FOB wear per RG 1.121.
Because the EOC34 projected upper bound depth does not exceed the structural limit, TSP/FOB wear is not expected to challenge the SIPC in any of the Unit 2 SGs during the period preceding the next inspection. Since TSP/FOB wear is not projected to violate the structural
Serial No.23-258 Docket No. 50-281 page 27 of 34 performance criteria prior to the next inspection, there is reasonable assurance that TSP/FOB wear will not cause the AILPC to be exceeded prior to the next inspection.
No indications of Stress Corrosion Cracking were detected during the EOC31 inspection.
However, a fully probabilistic multi-cycle OA analysis was performed simulating the life cycle of a susceptible tube population and generated Monte Carlo projections of both detected and undetected flaws for multiple cycles of operation. The simulation considered inspection POD, new flaw initiation, and growth to calculate burst probability and accident-induced leakage at time points of interest. The POD curves developed for these analyses used noise distributions that bound the 2R31 noise measurements in each area of interest, in conjunction with the MAPOD methodology.
The results are contained in the Figures and Tables below.
Figure 5: EOC34 Worst Case Burst Pressure of Circ PWSCC - Tubesheet Region 0.25...---------------------------r--------,
EOC34 Min BP 0.20 I
I I
I ' '
I I
I I
I
- I I
~
.::i 0.15 I
I I
e a..
Ql
-~
..!ll
~ 0.10
- , u 0.05 3XNOPD: 4470 psi I
I,
I I
Lower 95/50: 7314 psi I I I I I
- I :
I I,:
1 Probability: 0.05 --+----*
I
~
I
,I I
/ I I
,,' I I
I 0.00 +------r-----,,----.,___
--,.-- -- -= -:;;_*_----.--L--
1 --,-------i 2,000 3,000 4,000 5,000 6,000 7,000 8,000 9,000 Projected EOC34 Worst Case Burst Pressure (psi)
Table 12 EOC34 Probabilities of Burst and Leakage --Circ PWSCC in Tubesheet Region Population POB at 3xNOPD POL at MSLB PD Full Bundle
<0.002%
1.21%
SG Program 5%
5%
Maximum Allowable
i
.c Ill
.c 0...
CL Q)
Ill
- j E
- J u Serial No.23-258 Docket No. 50-281 page 28 of 34 Figure 6: EOC34 Worst Case Burst Pressure - Circumferential ODSCC @TTS 0.25 -.--------------------------,,,-------,
0.20 0.15 0.10 0.05 0.00 2,000
EOC34 Min BP 3XNOPD: 4470 psi I
I I
I I
I I
3,000 4,000 5,000 I '
I I
I I
I I
f f '
I I
I I
I I ' ' '
I I
I I
Lower 95/50: 7045 psi I
I I I /
I '
I /
I/
--r----* Prob: 0.05
/ 1
, I I
I I
6,000 7,000 8,000 Projected EOC34 Worst Case Burst Pressure (psi) 9,000 Table 13: EOC34 Probabilities of Burst and Leakage - Circumferential ODSCC @TTS Population POB at 3xNOPD POL at MSLB PD Full Bundle
<0.002%
1.23%
SG Program 5%
5%
Maximum Allowable
Serial No.23-258 Docket No. 50-281 page 29 of 34 Figure 7: EOC34 Worst Case Burst Pressure - Axial PWSCC within Tubesheet 0.25......-----------------------,....----------,
0.20
~
- s Ill 0.15
.c e a..
Q)
-~
- m
- , 0.10 E
- , u 0.05
EOC34 Min BP I,
I I,,
I ' ' ',,
' ' ' /,
,l Lower 95/50: 4626 psi I /
I,
I I,
I
/
1,l 3XNOPD: 4470 psi 1 ;1--------
Probability: 0.05 i,' I
,,, I
,,' I I
I I
I I
I 0.00 -l---------- -
-=-=-=-=-=---~--~--.,___,
1 1.___~--~--~--~-----l 2,000 2,500 3,000 3,500 4,000 4,500 5,000 5,500 6,000 6,500 7,000 Projected EOC34 Worst Case Burst Pressure (psi)
Table 14: EOC34 Probabilities of Burst and Leakage - Axial PWSCC within Tubesheet Population POB at 3xNOPD POL at MSLB PD Full Bundle 3.8%
0.25%
SG Program 5%
5%
Maximum Allowable
Serial No.23-258 Docket No. 50-281 page 30 of 34 Figure 8: EOC34 Worst Case Burst Pressure - Axial ODSCC @TSPs 0.25 -.--------------------~ ---------,
0.20
~
i 0.15
.c e 0..
Q)
.=!:
"Iii
- i 0.10 E
- J 0.05
EOC34 Min BP I I I
I I,
I I
I,
I I
I I,
Lower 95/50: 5422 psi I,
I ' '
I I,'
I,
I /
1,l 3XNOPD: 4470 psi 1
---~---------
Probability: 0.05 I
,, I t
,, I I
I L---'
I
*r I
0.00 +----...,...___,,-...,,-=-=- -=-- -,--.----'1'---..----"1----r----~-----.--------1 2,000 3,000 4,000 5,000 6,000 7,000 8,000 9,000 Projected EOC34 Worst Case Burst Pressure (psi)
Table 15: EOC34 Probabilities of Burst and Leakage -Axial ODSCC @TSPs Population POB at 3xNOPD POL at MSLB PD Full Bundle 1.16%
0.21%
SG Program 5%
5%
Maximum Allowable
Serial No.23-258 Docket No. 50-281 page 31 of 34 Figure 9: EOC34 Worst Case Burst Pressure - Axial ODSCC @Dents/Dings 0.25 -,---------------------...,------------,
0.20
~
i 0.15
.0 e
- n.
Q)
-~ -;
- i 0.10 E
- J 0
0.05
---* EOC34 Min BP I I I
I I
- I I I
I I
I I I ',
I I
I I,
I I I,
Lower 95/50: 5331 psi I,,
3XNOPD: 4470 psi I,
I,'
I,'
I,'
-* 1----------
,'I
,,, I I
I I
Probability: 0.05
,~.,....
I 0.00 +------------
... -=-=-=-"'....,_-~_.__
, _~~---~------r---------1 2,000 3,000 4,000 5,000 6,000 7,000 8,000 9,000 Projected EOC34 Worst Case Burst Pressure (psi)
Table 16: EOC34 Probabilities of Burst and Leakage -Axial ODSCC @Dents/Dings Population POB at 3xNOPD POL at MSLB PD Full Bundle 0.54%
0.18%
SG Program 5%
5%
Maximum Allowable
Serial No.23-258 Docket No. 50-281 page 32 of 34
- h. The primary to secondary LEAKAGE rate observed in each SG (if it is not practical to assign the LEAKAGE to an individual SG, the entire primary to secondary LEAKAGE should be conservatively assumed to be from one SG) during the cycle preceding the inspection which is the subject of the report, Routine primary-to-secondary leak monitoring is conducted in accordance with station procedures. During the cycle preceding EOC31, no measurable primary-to-secondary leakage was observed in any Unit 2 SG.
- i. The calculated accident induced LEAKAGE rate from the portion of the tubes below 17.89 inches from the top of the tubesheet for the most limiting accident in the most limiting SG. In addition, if the calculated accident induced LEAKAGE rate from the most limiting accident is less than 1.80 times the maximum operational primary to secondary LEAKAGE rate, the report should describe how it was determined, The permanent alternate repair criteria (PARC) requires that the component of operational leakage from the prior cycle from below the H-star distance be multiplied by a factor of 1.8 and added to the total accident leakage from any other source and compared to the allowable accident induced leakage limit. Since there is reasonable assurance that no tube degradation identified during this outage would have resulted in leakage during an accident, the contribution to accident leakage from other sources is zero.
Assuming that the prior cycle operational leakage is <1 GPO originated from below the H-star distance and multiplying this leakage by a factor of 1.8 as required by the PARC, yields an accident induced leakage value of <1.8 GPO.
This value is well below the 470 GPO limit for the limiting SG and provides reasonable assurance that the accident induced leakage performance criteria would not have been exceeded during a limiting design basis accident.
- j. The results of the monitoring for tube axial displacement (slippage). If slippage is discovered, the implications of the discovery and corrective action shall be provided.
No indications of tube slippage were identified during the evaluation of bobbin probe examination data from any SG during EOC31.
AILPC ARC AVB BLG BOC BPC BPH CM DNG DNT ECT EFPM EOC ETSS EWM FAC FDB FO FOSAR GPD HRS ISI LPM LPS MBM Serial No.23-258 Docket No. 50-281 page 33 of 34 Table 17-Acronyms Accident Induced Leakage Performance Criteria NDD No Degradation Detected Alternate Repair Criteria NOPD Normal Operating Pressure Differential Anti-Vibration Bar NTE No Tube Expansion Bulge OA Operational Assessment Beginning Of Cycle OD Outside Diameter Baffle Plate Cold ODSCC Outer Diameter Stress Corrosion Cracking Baffle Plate Hot OVR Over Roll Condition Monitoring Assessment OXP Over Expansion Ding PARC Permanent Alternate Repair Criteria Dent PDA Percent Degraded Area Eddy Current Test PLP Possible Loose Part Effective Full Power Months POD Probability Of Detection End Of Cycle PWSCC Primary Water Stress Corrosion Cracking Examination Technique Specification Sheet sec Stress Corrosion Cracking Entangled wire mass SG Steam Generator Flow Assisted Corrosion SIPC Structural Integrity Performance Criteria Flow Distribution Baffle SSI Secondary Side Inspection Foreign Object TS Technical Specification Foreign Object Search And Retrieval TSC Tube Sheet Cold Gallons Per Day TSH Tube Sheet Hot High Residual Stress TSP Tube Support Plate In-Service Inspection TTS Top ofTubesheet Loose Part Monitoring TW Through Wall Loose Part Signal VOL Volumetric Manufacturing Burnish Mark WAR Wear
Figure 10 - General Arrangement Serial No.23-258 Docket No. 50-281 page 34 of 34