ML24324A002
| ML24324A002 | |
| Person / Time | |
|---|---|
| Site: | Surry  |
| Issue date: | 11/18/2024 |
| From: | Denise Wilson Virginia Electric & Power Co (VEPCO) |
| To: | Office of Nuclear Reactor Regulation, Document Control Desk |
| References | |
| 24-346 | |
| Download: ML24324A002 (1) | |
Text
VIRGI NIA ELECTRIC AND POWER COMPANY RICHMOND, VIRGINIA 23261 United States Nuclear Regulatory Commission Attention: Document Control Desk Washington, DC 20555-0001 VIRGINIA ELECTRIC AND POWER COMPANY SURRY POWER STATION UNITS 1 AND 2 STEAM GENERATOR TUBE INSPECTION REPORTS Serial No.
SS&L/MMT Docket Nos.
License Nos.24-346 RO 50-280/281 DPR 32/37 FOR THE UNIT 1 FALL 2022 AND THE UNIT 2 SPRING 2023 REFUEUNG OUTAGES By letter dated August 23, 2024 (ADAMS Accession No. ML24219A237), the U.S. Nuclear Regulatory Commission (NRC) issued Amendment Number 319 to Subsequent Renewed Facility Operating License No. DPR-32 and Amendment Number 319 to Subsequent Renewed Facility Operating License No. DPR-37 for Surry Power Station (SPS), Units 1 and 2, respectively. Amendments 319 and 319 revise Technical Specification (TS) 6.6.A.3, "Steam Generator Tube Inspection Report," based on Technical Specifications Task Force (TSTF) Traveler TSTF-577, Revision 1, "Revised Frequencies for Steam Generator Tube Inspections" and requires a Steam Generator Tube Inspection Report to be submitted within 30 days after implementation of the license amendment.
Pursuant to TSTF-577, Revision 1, Steam Generator Tube Inspection Reports satisfying the revised TS 6.6.A.3 requirements are being provided to the NRC staff because a 100%
inspection during the SPS Unit 1 Fall 2022 End-of-Cycle 31 (EOC31) refueling outage (1 R31)
(i.e., before adopting TSTF-577) and a 100% inspection during the SPS Unit 2 Spring 2023 EOC 31 refueling outage (2R31) (i.e., before adopting TSTF-577) are being credited as the beginning points of the new inspection periods, respectively. to this letter contains the Steam Generator Tube Inspection Report for the SPS Unit 1 Fall 2022 EOC31 refueling outage (1 R31) in accordance with the revised TS 6.6.A.3 reporting requirements. to this letter contains the Steam Generator Tube Inspection Report for the SPS Unit 2 Spring 2023 EOC31 refueling outage (2R31) in accordance with the revised TS 6.6.A.3 reporting requirements.
If you have any questions concerning this information, please contact Mr. Michael M.
True, Jr. at (757) 365-2446.
Respectfully, David H.
ilson Site Vice resident November 18, 2024
Attachments:
Serial No.24-346 Docket Nos. 50-280/281 Page 2 of 2
- 1. Surry Unit 1 Steam Generator Tube Inspection Report for the Fall 2022 Refueling Outage
- 2. 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 NRC 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
ATTACHMENT 1 SURRY UNIT 1 Serial No.24-346 Docket No. 50-280 REVISED STEAM GENERATOR TUBE INSPECTION REPORT FOR THE FALL 2022 REFUELING OUTAGE VIRGINIA ELECTRIC AND POWER COMPANY
{DOMINION ENERGY VIRGINIA)
SURRY UNIT 1 REVISED STEAM GENERATOR TUBE INSPECTION REPORT FOR THE FALL 2022 REFUELING OUTAGE Serial No.24-346 Docket No. 50-280 page 1 of 24 In accordance with Surry Power Station Unit 1 (SPS1) Technical Specification (TS) 6.6.A.3, Virginia Electric And Power Company (Dominion Energy) is submitting this Steam Generator Tube Inspection report which describes the results of the previously complete SPS1 Steam Generator (SG) examinations. During the SPS1 Fall 2022 End-of-Cyle 31 (EOC31) refueling outage (1 R31 ), SG inspections were completed in accordance with TS 6.4.Q for all three SGs, designated as SG-A, SG-B, and SG-C. Based upon entry into Mode 4, exceeding 200°F, on December 13, 2022, a report was required to be submitted by June 11, 2023. Due to adopting a revised Technical Specifications, TSTF-577 Rev. 1, a revised Steam Generator Tube Inspection Report is required to be submitted within 30 days after implementation of the license amendment.
All three Unit 1 SGs were last inspected during the Spring 2021 refueling outage (EOC30) and had operated for 383.1 EFPM prior to that outage. Unit 1 operated for 16.8 EFPM during cycle
- 31.
Consequently, at the time of this inspection the Unit 1 SGs had operated for 399.9 EFPM since the first in-service inspection.
The three Surry Unit 1 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 1981. The moisture separators were subsequently upgraded to support a core power up-rate implemented in 1995. The feedrings were replaced in 2010.
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. Surry Unit 1 Steam Generator Tube Inspection Report for Fall 2022 Refueling outage (Serial No.23-020) figure 10 contains the general arrangement and figures 11 and 12 contain a photo and illustration of the loose parts catching mechanism in the in the Feedwater Regulating Valves. 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 1 steam generators have experienced no reportable primary to secondary leakage since the 1990s and operate with a nominal hot leg temperature of 604°F.
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.
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 12 at the end of this report.
A report shall be submitted within 180 days a'fter 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 Serial No.24-346 Docket No. 50-280 page 2 of 24 The 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 Table 1 were examined full length with both Bobbin and Array probes due to the potentially increased susceptibility of Stress Corrosion Cracking as detailed in the response for b. below.
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 burnish marks, volumetric indications, and wear (excluding AVB wear).
As a result of concerns for possible degradation at dent/ding locations, the special interest scope of dents/dings with a +Point' probe included 100% of all dents/dings 2: 2 Volts located in the hot leg straight section and 100% of all dents/dings 2: 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.
Serial No.24-346 Docket No. 50-280 page 3 of 24 The primary side work scope also included video/ visual examinations (as-found I as-left) of all channel heads 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 All primary side visual examinations were completed satisfactorily with no degradation or anomalies reported.
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.
All secondary side visual examinations were completed satisfactorily with no degradation detected or anomalies reported.
- b. The nondestructive examination techniques utilized for tubes with increased degradation susceptibility.
Each of the Surry Unit 1 SGs was screened to identify any low row indications of improper heat treatment. None were identified. All of the SGs were also screened for long row indications of improper heat treatment (-2 sigma tubes) and associated high residual stress. This evaluation identified 19, 22, and 3 tubes in SGs A, B, and C, respectively, which may have been improperly heat treated.
One of the 19 tubes in SG-A with potentially higher stress has since been plugged. Table 1 provides a listing of the 43 in-service tubes that have been identified through screening as possibly containing high residual stress due to an improper heat treatment.
All the high residual stress (HRS) tubes in Table 1 were examined full length with both Bobbin and Array probes and closely scrutinized during the analysis process due to the potentially increased susceptibility of Stress Corrosion Cracking.
Table 1: Tubes with Potentially High Residual Stress SG Row Column No. Tubes A
9 33 A
11 8
A 13 86 A
14 44 A
16 6
A 16 11 A
16 41 A
16 90 A
17 42 A
17 72 18 A
20 42 A
20 51 A
22 9
A 22 11 A
22 13 A
23 43 A
26 81 A
28 77 B
9 79 B
11 4
B 11 10 B
11 11 B
11 85 B
18 31 B
18 50 B
18 75 B
19 50 B
21 6
B 21 7
22 B
23 8
B 23 25 B
23 41 B
23 88 B
24 42 B
25 9
B 25 39 B
25 53 B
26 15 B
26 45 B
27 38 C
22 21 C
23 12 3
C 29 16
- c. For each degradation mechanism found:
- 1. The nondestructive examination techniques utilized; Serial No.24-346 Docket No. 50-280 page 4 of 24
- 2. The location, orientation (if linear), measured size (if available), and voltage response for each indication. For tube wear at support structures
Serial No.24-346 Docket No. 50-280 page 5 of 24 less than 20 percent through-wall, only the total number of indications needs to be reported;
- 3. A description of the condition monitoring assessment and results, including the margin to the tube integrity performance criteria and comparison with the margin predicted to exist at the inspection by the previous forward-looking tube integrity assessment; and
- 4. The number of tubes plugged during the inspection outage.
During the EOC31 examination, degradation modes observed were legacy anti-vibration bar (AVB) wear and various legacy volumetric indications (two maintenance related, several foreign object related, some TSP wear, and a few of undetermined origin). New degradation included a single small TSP wear indication and several small AVB wear indications. None of legacy or new degradation exceeded the 40% TW technical specification plugging criteria. No corrosion related degradation (such as stress corrosion cracking) was detected. No detected degradation exceeded condition monitoring limits.
The inspection program focused on the degradation mechanisms listed in Table 2 and utilized the referenced eddy current techniques.
Serial No.24-346 Docket No. 50-280 page 6 of 24 Table 2 - Inspection Method for Applicable Degradation Mechanism Classification Degradation Location Probe Type Mechanism Existing Wear Anti-Vibration Bars Bobbin - Detection and Sizing Existing OD Pitting Top-of-Tubesheet (TTS)
Bobbin and Array - Detection
+Point' - Sizing Existing Wear Tube Support Plate Bobbin - Detection
+Point' - Sizing Existing Tube Wear (Foreign Freespan and TTS Bobbin and Array - Detection Objects)
+Point' - Sizing Existing PWSCC Tube Ends N/A*
Existing Wear Flow Distribution Ba_ffle (FOB)
Bobbin - Detection
+Point' - Sizing Potential PWSCC Tubesheet Overexpansions (OXP)
Array - Detection
+Point' - Sizing Bulges, Dents, Manufacturing Array - Detection Potential ODSCC, PWSCC Anomalies, and Above Tubesheet Overexpansions (OVR)
+Point' - Sizing Potential ODSCC Tubesheet Crevice in Tubes With N/A**
NTE Potential Tube Slippage Within Tubesheet Bobbin - Detection Existing ODSCC, PWSCC Hot Leg TTS Array - Detection
+Point' - Sizing Potential ODSCC, PWSCC Row 1 and 2 U-bends
+Point' - Detection and Sizing Potential ODSCC Freespan and Tube Supports Bobbin - Detection
+Point' - Sizing Existing ODSCC, PWSCC High Residual Stress Tubes Bobbin and Array - Detection
+Point' - Sizing Inspection not required per technical specification alternate repair criteria
- All tubes with no tubesheet expansion (NTE) have previously been plugged As stated above, anti-vibration bar (AVB) wear, tube support plate (TSP) wear, flow distribution baffle (FOB) wear, and foreign object wear were detected during EOC31.
No indications of stress corrosion cracking (SCC) were detected during the EOC31 SG tube inspection.
AVB Wear In total, 114 AVB wear indications in 84 tubes were identified among all three SGs during EOC31. Of these, 12 indications in 8 tubes were sized ~ 20% TW. None of the identified flaws exceeded the Technical Specification plugging limit (40% TW) and none were
Serial No.24-346 Docket No. 50-280 page 7 of 24 plugged. The maximum reported depth was 28% TW. A listing of all 12 indications of AVB Wear~ 20% TW is contained in Table 3.
Table 3: Surry 1 EOC31 Inspection Summary - AVB Wear Indications 2:20% TW Wear Depth (% TW)
ETSS 96041.1 SG Row Col AVB No.
EOC30 EOC31 A
32 69 AV2 25 21 A
33 63 AV3 25 21 B
34 58 AV2 27 27 B
34 58 AV3 23 22 B
35 17 AV3 26 26 C
35 17 AV1 25 24 C
38 67 AV3 22 20 C
39 23 AV2 21 20 C
39 23 AV3 30 28 C
42 31 AV1 24 23 C
42 31 AV2 24 23 C
42 31 AV3 22 20 Non-AVB Wear Bobbin probe or array probe inspections of in-service tubes identified 36 indications of volumetric tube degradation not related to AVB wear, in 35 tubes among all three SGs.
The measured flaw depths range from 5% TW to 33% TW.
Sizing of these indications was performed with a +Point' rotating coil.
Table 4 lists the 15 Non-AVB Wear indications that recorded wall losses ~ 20% TW.
The sizing techniques used to determine the dimensions of the flaws are also identified in the table.
Thirty-five (35) of the 36 indications were reported during previous inspection outages, meaning that one indication was newly reported during EOC31 (15%TW TSP wear in SG-C R34-C55 at 02H-0.67"). None of the 35 repeat indications have exhibited signal change indicative of wear growth.
Two (2) of the 36 indications (SG-A R1-C86 and SG-B R1-C7) were caused by a sludge lancing process applied approximately 20 years ago (no longer used). Seven (7) of the indications result from support wear (TSP or baffle plate). One (1) indication result from legacy pitting. Three (3) of the indications are of uncertain origin, and twenty-three (23) indications result from 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 21998.1, 27901.1, 27902.1, and 96910.1 respectively. The CM curves represent the structural
Serial No.24-346 Docket No. 50-280 page 8 of 24 performance criteria derived by conservatively accounting for material property uncertainties, model uncertainties, and NDE 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.
SG Row Col Location A
1 86 BPC -5.55" A
2 57 06C -0.37" A
3 66 05C -0.67" A
6 88 TSH +0.16" A
8 38 TSH +0.40" A
34 67 TSH +0.03" A
38 30 TSC +1.84" B
1 7
TSH+0.24" B
12 51 TSC+0.27" B
31 15 BPH +0.53" B
31 16 BPH +0.53" B
32 15 BPH +0.51" B
32 18 BPH +0.61" B
33 17 BPH+0.56" B
33 18 BPH +0.61" B
35 20 BPH +1.07" B
37 31 04H-24.40" B
40 50 TSH +0.48" Table 4: Summary of Non-A VB Wear Volumetric Degradation Axial Circ Max Depth Length Length Initially ETSS Volts
(%TW)
(in)
(in)
Reported Cause Lancing 21998.1 0.32 25 0.85 0.37 2015 Equipment 96910.1 0.51 13 0.27 0.32 2006 TSP Wear 27901.1 0.21 24 0.27 0.32 2009 Foreign Object 27901.1 0.20 23 0.35 0.42 2006 Foreign Object 21998.1 0.21 16 0.27 0.37 2001 Legacy Pitting 27901.1 0.19 22 0.27 0.26 2006 Foreign Object 27901.1 0.12 16 0.27 0.42 2018 Foreign Object 27901.1 0.15 19 0.37 0.37 27901.1 0.12 16 0.35 0.4 2006 Foreign Object 21998.1 0.21 18 0.37 0.32 2007 Historical SG Maintenance 21988.1 0.11 10 0.32 0.37 2019 Unknown. Small volumetric 27901.1 0.11 15 0.21 0.37 2010 Foreign Object 27901.1 0.16 20 0.24 0.48 2010 Foreign Object 27901.1 0.1 14 0.21 0.48 2010 Foreign Object 27901.1 0.09 12 0.24 0.26 2010 Foreign Object 27901.1 0.05 8
0.21 0.34 2019 Foreign Object 27901.1 0.13 17 0.29 0.32 2010 Foreign Object 27902.1 0.27 15 0.48 0.48 2010 Foreign Object 21998.1 0.13 12 0.21 0.37 2013 Unknown. Small volumetric 27901.1 0.31 31 0.48 0.42 2007 Foreign Object Foreign Object Remaining?
NIA NIA No No NIA No No No NIA NIA No No No No No No No NIA No In Situ Tested?
No No No No No No No No No No No No No No No No No No No Serial No.24-346 Docket No. 50-280 page 9 of 24 Plugged &
Stabilized?
No No No No No No No No No No No No No No No No No No No
B 40 51 TSH +0.85" 27901.1 0.34 33 B
41 51 TSH +0.13" 27901.1 0.11 15 B
45 48 TSC+2.48" 21998.1 0.43 32 C
3 52 TSC +0.40" 27901.1 0.3 30 C
4 68 06C -0.32" 96910.1 0.33 17 C
15 49 04H -0.61" 96910.1 0.31 15 C
26 85 BPH + 0.59" 27901.1 0.26 28 C
27 82 BPH +0.56" 27901.1 0.25 27 C
29 82 BPH + 0.56" 27901.1 0.23 25 C
34 55 02H -0.67 96910.1 0.32 15 C
36 24 BPH -0.27" 96910.1 0.12 7
C 36 64 TSC +0.03" 27901.1 0.3 30 C
36 66 TSC-0.11" 27901.1 0.22 25 C
38 66 TSC +0.08" 27901.1 0.29 30 C
44 50 BPH -0.29" 96910.1 0.09 5
C 45 52 BPH -0.21" 96910.1 0.09 5
0.32 0.45 2007 Foreign Object 0.24 0.32 2007 Foreign Object Unknown. Small 0.32 0.32 2013 volumetric 0.27 0.37 2015 Foreign Object 0.29 0.37 2015 TSP Wear 0.24 0.32 2021 TSP Wear 0.19 0.63 2018 Foreign Object 0.29 0.4 2010 Foreign Object 0.27 0.56 2018 Foreign Object 0.27 0.26 2022 TSP Wear 0.32 0.26 2012 FOB Wear 0.27 0.37 2012 Foreign Object 0.27 0.37 2015 Foreign Object 0.32 0.37 2009 Foreign Object 0.24 0.26 2015 FOB Wear 0.24 0.29 2015 FOB Wear No No N/A No N/A N/A No No No N/A N/A No No No N/A N/A No No No No No No No No No No No No No No No No Serial No.24-346 Docket No. 50-280 page 10 of 24 No No No No No No No No No No No No No No No No
Stress Corrosion Cracking No indications of stress corrosion cracking were identified during EOC31.
Condition Monitoring Serial No.24-346 Docket No. 50-280 page 11 of 24 None of the tube degradation identified in Surry Unit 1 SGs during the EOC31 outage violated the structural integrity performance criteria; thereby providing reasonable assurance 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.
The Condition Monitoring (CM) Assessment for each detected degradation mechanism was determined using the methodology described below.
Table 5 - CM Methodology CM (Mechanism)
Methodology 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 (NDE, burst relationship, and material properties). The Mixed Arithmetic/Monte Carlo methodology accounts for these uncertainties as follows. The Arithmetic part accounts for NDE 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 upper bound % TW value. The Monte Carlo part accounts for uncertainty, from burst relationship and material properties, for determining the structural limit. If the upper bound % TW value is less than the structural limit, CM is met.
- 2) The CM curve, itself, has built into it the three uncertainties using Monte Carlo methods.
Therefore, no arithmetic correction for NDE sizing is required since it's accounted for by the CM curve.
AVB Wear Table 6: A mixed Arithmetic/Monte Carlo methodology was used for CM of AVB wear.
Degradation Mechanism Maximum 95%/50% Upper CM Limit Depth (wear)
Depth Bound Depth AVB Wear 28%
34.7%
61%
Since this upper bound estimate does not exceed the conservative structural limit of 61 % TW, it is concluded that none of the AVB wear flaws exceeded the structural limit. 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 flaws sized with ETSS 21998.1, 27901.1, 27902.1, and 96910.1 respectively.
Serial No.24-346 Docket No. 50-280 page 12 of 24 Figure 1: CM Curve for Flaws Sized w/ETSS 21998.1 - Model: Axial Thinning w/Limited Circumferential Extent 100 90 80 70
[
~
60 J:::
Q.
50 C
E =
40 E
- c..
- E w
30 C z 20 10 0
0.0 0.2 0.4 ETSS21998.1 R4 0.6 0.8 Length, (Inch)
-21998.1 R4 VOLs 1.0 1.2 1.4 Figure 2: CM Curve for Flaws Sized w/ETSS 27901.1 - Model: Axial Thinning w/Limited Circumferential Extent 100 ETSS27901.1 R1 90
-27901.1 R1 Foreign Object Wear 80 70
~ 60
~
J:::
Q..,
50 C
E =
40 E
- c..
- E 30 w
C z I *
- 20 I **
10 0
0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 Length, (Inch)
Serial No.24-346 Docket No. 50-280 page 13 of 24 Figure 3: CM Curve for Flaws Sized w/ETSS 27902.1 - Model: Axial Thinning w/Limited Circumferential Extent 100 ETSS 27902.1 R1 90
-27902.1 R1 Foreign Object Wear 80 70
[
~
60
.s::
Q.
50 C
E 40 E
'le..
- E 30 w
C z 20 10 0
0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 Figure 4:
100 90 80 70
[
60
~
0
.s::
Q.
50 C
E 40 E
- c..
30 w
0 z 20 10 0
0.0 Length, (Inch)
CM Curve for Flaws Sized w/ ETSS 96910.1 - Model: Axial Thinning w/Limited Circumferential Extent ETSS96910.1 R11
-96910.1 R11 TSP / FOB Wear
- i 0.2 0.4 0.6 0.8 1.0 1.2 1.4 Length, (Inch)
Serial No.24-346 Docket No. 50-280 page 14 of 24 Table 7 illustrates that the current (EOC31) inspection results are bounded by the previous (EOC30) OA projections.
Table 7: Summary of Prior OA Validation Spring 2021, EOC30 Operational Fall 2022 EOC31 Degradation Mechanism Assessment Projection Observed AVBWear 33%TW 28%TW TSP/FOB Wear 22%TW 17%TW Specific depth not projected; no actual Maximum depth of 33% TW Volumetric Degradation growth expected; flaws expected to remain detected; no growth observed.
structurally insignificant CM criteria satisfied.
Circumferential ODSCC Lower 95/50 burst pressure= 7385 psi at No indications detected at top of tubesheet EOC33 Axial PWSCC Lower 95/50 burst pressure = 5155 psi at No indications detected at top of tubesheet EOC33 Circumferential PWSCC Lower 95/50 burst pressure = 7385 psi at No indications detected within Tubesheet EOC33 Operational Leakage Projected: <150 GPD No measurable leakage during cycle 31 One tube in SG-A was plugged for a large historical free span ding indication during 1 R31.
No tubes were plugged in SG-8 or SG-C.
- d. An analysis summary of the tube integrity conditions predicted to exist at the next schedule inspection (the forward-looking tube integrity assessment) relative to the applicable performance criteria, including the analysis methodology, inputs, and results; 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 54 effective full power months or at least every other refueling outage (whichever results in more frequent inspections). All existing and potential degradation mechanisms were evaluated for a 3-cycle operating period over a 4.5 EFPY duration.
The following sections summarize the evaluations performed for existing degradation mechanisms as well as important potential degradation mechanisms.
Table 7 illustrates that the current (EOC31) inspection results are bounded by the previous (EOC30) OA projections; therefore, providing a basis that
Serial No.24-346 Docket No. 50-280 page 15 of 24 the OA methodology is sufficient, and adjustments to the current QA methodology are not required. Table 8 identifies the degradation specific QA methodology. Table 9 summarizes the EOC34 QA projections with comparisons to the applicable structural and leakage limits.
Table 8-0A Methodology OA (Mechanism)
Methodoloav Structural Limit Note AVB Wear Mixed Arithmetic/Monte Carlo Structural Limit (61 % TW) 1 TSP/FDB Wear Mixed Arithmetic/Monte Carlo Structural Limit (57% TW) 1 FO Wear Monte Carlo Structural Limit (58% TW) 2 Circ PWSCC (TTS/TS)
Fully Probabilistic Multi-Cycle OA Lower 95/50 Burst Pressure > 3~P 3
Axial PWSCC (TTS/TS)
Fully Probabilistic Multi-Cycle OA Lower 95/50 Burst Pressure > 3~P 3
Circ ODSCC (TTS)
Fully Probabilistic Multi-Cycle OA Lower 95/50 Burst Pressure > 3~P 3
Fully Probabilistic Multi-Cycle OA Lower 95/50 Burst Pressure > 3~P 3
Axial ODSCC (DNT/DNG)
Fully Probabilistic Multi-Cycle OA Lower 95/50 Burst Pressure > 3~P 3
- 1) For OA (plug on NOE sizing), four uncertainties must be considered (NDE, 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 (from the ETSS standard deviation) to arrive at the limiting BOC % TW value.
The limiting BOC % TW value is adjusted for growth allowance/uncertainty to arrive at the EOC % TW value, for comparison to the structural limit. Built into the structural limit, using Monte Carlo methods, are adjustments for burst relationship and material properties uncertainties. When the EOC % TW value is less than the structural limit, OA is projected to be met.
- 2) The limiting BOC % TW is set equal to the upper 95th POD physical depth value. This value is adjusted for growth to arrive at the EOC % TW, for comparison to the structural limit. Built into the structural limit, using Monte Carlo methods, are adjustments for burst relationship and material properties uncertainties. When the EOC % TW value is less than the structural limit, OA is projected to be met.
- 3) For the Fully Probabilistic Multi-Cycle OA, all uncertainties are accounted for within the probabilistic model. OA is projected to be met when the calculated lower 95/50 burst pressure exceeds three times the primary-to-secondary differential pressure (3~P).
Serial No.24-346 Docket No. 50-280 page 16 of 24 Table 9-OA Projected Condition During EOC34 Structural Integrity Accident Induced Leakage Performance Criteria Performance Criteria Degradation Mechanism EOC34 EOC34 Limit Projection Limit Projection AVB Wear 61%
40.8%TW 470 GPO Zero Leakage Maximum Depth Foreign Object Wear 58%
54.3%TW 470 GPO Zero Leakage Maximum Depth TSP/FOB Wear 57%
53%TW 470 GPO Zero Leakage Maximum Depth Pittinq Dormant. No projected pittin l Circumferential OOSCC @
4470 psi 7147 psi 470 GPO Zero Leakage TTS Axial PWSCC (@ TTS 4470 psi 5647 psi 470 GPO Zero Leakage Circumferential PWSCC within 4470 psi 7106 psi 470 GPO Zero Leakage tubesheet expansion Axial OOSCC (@ TSPs 4470 osi 6079 osi 470 GPO Zero Leakaqe Axial OOSCC @ (ONT/ONG) 4470 psi 5507 psi 470 GPO Zero Leakage Figure 5: EOC34 Worst Case Burst Pressure - Circumferential ODSCC @TTS 0.25 --------------------------r--------,
0.20
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---1 1,000 2,000 3,000 4,000 5,000 6,000 7,000 8,000 9,000 Projected EOC34 Worst Case Burst Pressure (psi)
~
- E Serial No.24-346 Docket No. 50-280 page 17 of 24 Figure 6: EOC34 Worst Case Burst Pressure - Axial PWSCC @TTS 0.25 ~----------------------,;..-------------,
0.20
- E ca 0.15
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..... _--r-___
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---1 2,000 3,000 4,000 5,000 6,000 7,000 8,000 9,000 Projected EOC34 Worst Case Burst Pressure (psi)
Figure 7: EOC34 Worst Case Burst Pressure - Circ PWSCC within Tubesheet 0.25..------------------------------,-, ---------,
EOC34 Min BP 0.20 I
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--=-:...* -
- -----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)
Serial No.24-346 Docket No. 50-280 page 18 of 24 Figure 8: EOC34 Worst Case Burst Pressure - Axial ODSCC @TSPs 0.25 ~------ -------------------~.- ------~
=
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~ 0.15
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2,000 3,000 4,000 5,000 6,000 7,000 8,000 9,000 Projected EOC34 Worst Case Burst Pressure (psi)
Figure 9: EOC34 Worst Case Burst Pressure - Axial ODSCC @Dents/Dings 0.25,-------------------------=,--------------,
0.20
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1 2,000 3,000 4,000 5,000 6,000 7,000 8,000 9,000 Projected EOC34 Worst Case Burst Pressure (psi)
Serial No.24-346 Docket No. 50-280 page 19 of 24
- e. The number and percentage of tubes plugged to date, and the effective plugging percentage in each SG; Table 10 provides the plugging totals and percentages to date.
Table 10 - Tube Pluaaing Summary Steam Generator SG-A SG-B SG-C Total Prior to EOC-31 44 26 42 112 EOC-31 l
0 0
l Total 45 26 42 113
% Plugged 1.3%
0.8%
1.3%
1.1%
Since no sleeving has been performed in the Surry Unit 1 steam generators, the effective plugging percentage is the same as the actual plugging percentage.
- f.
The results of any SG secondary side inspections; Foreign Objects 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 are therefore considered to be benign.
During the EOC29 (Fall 2019) 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 11 below include foreign objects removed during the EOC31 FOSAR and water lancing activities and the foreign objects known to be remaining at the conclusion of the EOC31 outage.
During 1 R31, TTS sludge lancing was performed in each of the Surry Unit 1 SGs. In total, 84 pounds of sludge related material was removed from all three SGs (A= 40 lbs., B= 24 lbs., and C = 20 lbs.).
Table 11: Foreign Object Highlights SG-Item#
Description Location Configuration ECT Results Estimated Size R6-C69 Legacy metal disk lodged between tubes R7-C68 R6-C69 and R7-C69.
1.1" diameter A-1 Historical (1 R20) Metal R7-C69 The disk is sitting on PLP disk its edge and is fused No Wear 0.2" thick TSC +0.24" to +1.24" to the top of the C/L tubesheet.
Legacy entangled Historical (1 R21)
R30-C47 mass of wire and Not A-2 Entangled wire mass of R30-C48 sludge located at TSH NOD Determined sludge/scale at TSH located behind the center stay rod Irregular shaped object A-21 Historical (1 R29) Irregular R36-C73 discovered at TSH PLP
~0.4" diameter object at TSH R37-C73 during 1 R29 post No Wear lance SSI R35-C71 R34-C71 R33-C71 R32-C71 Area of sludge (behind Region is Historical (1R29) Area of R31-C71 inner most tie-rod) spread over 5 A-22 sludge (behind inner most R31-C72 discovered at TSH NOD rows and 2 tie-rod) at TSH during 1 R29 post columns of R32-C72 lance SSI tubes R33-C72 R34-C72 R35-C72 1R31 Hard sludge rock R25-C46 1R31 Hard sludge rock LPS 0.50" X 0.25" X A-33 located on TSH R26-C46 fixed toTSH.
No Wear 0.10" 1 R31 Loose Wire on 1R31 Wire located on A-34 TSH R30-C47 TSH. (Discovered at NOD
~2" long wire FOTS A-2 I location)
Fixity Fixed Fixed Fixed Fixed sludge at TIS. No loose parts noted.
Fixed Retrieved 1R31 Serial No.24-346 Docket No. 50-280 page 20 of 24 2021 Disposition Initially identified 1 R20. Evaluated in 2009 (1 R22) with Framatome CR 2009-2529.
Object has remained fixed since that time.
Position and fixity again confirmed during 1 R31. Object has not caused tube degradation. Leave as is and monitor by ECT and SSI during next ISi.
During 1 R29, a small pile of legacy fine wires embedded in fixed sludge was aggressively raked and water lanced.
During 1 R31, configuration confirmed by SSI. Wires pose no threat to tube integrity (since 2007). Leave as is and monitor by ECT and SSI at next ISi.
Irregular object identified during 1 R29 Post Lance. Object is tightly lodged in place between two tubes. ECT history shows object present back to 2006. 1 R31 ECT observed no wear. Leave as is and monitor by ECT and SSI at next ISi.
During 1 R29, the sludge region was investigated by FOSAR and determined to be sludge deposits located on the TIS (H/L) and fixed in place. No loose parts were noted. During 1R31, ECTwas NOD (no wear). Leave as is and monitor by ECT at next ISi.
During 1 R31 sludge rock discovered and fixed to the TIS. ECT was NOD (no wear).
Leave as is and monitor by ECT at next ISi.
During 1 R31 ~2" wire discovered on TIS.
ECT was NOD (no wear). Item was removed and closed out at 1 R31. No actions required going forward.
SG-Item#
Description Location Configuration Parts captured in the (1 R31) Lancing strainer lancing strainers A-32 parts TTS during 1 R31 TTS lancing Historical (1 R29) lodged R40-C39 1R29 Foreign object 8-9 round object at TSH.
R40-C40 lodged between two Likely hard sludge.
tubes at TSH 1R31 piece of weld 1R31 Piece of Weld Slag R35-C27 8-20 located at TSH R35-C28 slag discovered during post lance inspection.
Parts captured in the 8-21 (1 R31) Lancing strainer TTS lancing strainers parts during 1R31 TTS lancing R4-C55, R4-C56 Historical (1 R29) Deposit 1 R29 Hard deposit C-38 adhered to TSH R5-C55, R5-C56 tightly adhered to TSH.
No tube contact.
1 R29 Hard deposit Historical (1 R29) Hard R9-C40 C-42 deposit bridging at TSH R10-C40 tube-to-tube bridging atTSH 1 R31 Irregular Object C-49 (Tube Scale) in C/L R27-C85 Tube Scale annulus C-50 1 R31 Tube Scale located R4-C29 Tube Scale atTSC R4-C30 C-51 1 R31 Tube Scale located NTL Tube Scale on NTL ECT Results Estimated Size Fixity Various parts Retrieved at N/A ranging from 1R31
-1/8" to -1 "
Two PLPs 0.4" diameter Fixed 1.50" X 0.24" X Retrieved at NOD 0.20" 1R31 Various parts N/A ranging from Retrieved at
-1/8" to -1 "
1R31 NOD
-0.5" diameter Fixed Spans multiple NOD tubes in TTS Fixed sludge region 0.75" piece of Retrieved at INF scale 1R31 NOD 0.3" piece of Retrieved at scale 1R31 N/A 0.75" piece of Retrieved at scale 1R31 Serial No.24-346 Docket No. 50-280 page 21 of 24 2021 Disposition During 1 R31, many objects were captured in the SGA lancing strainers. Most are sludge related. There were also fragments of small diameter wire and small pieces of flex gasket material.
Historical 1 R29 object. During 1 R31 ECT detected two PLP. No wear detected. SSI confirmed that part remains fixed to the TTS. Continue to monitor with ECT and SSI at next ISi.
During 1 R31, weld slag identified during post lance ISi and removed from the SG.
ECT results NDD. Item closed out at 1 R31.
Going forward no further actions required.
During 1 R31, many objects were captured in the SG8 lancing strainers. Most are sludge related. There were also fragments of small diameter wire and flex gasket material.
Deposit is fixed in place and not making contact with tubes. During 1 R31, ECT was NOD (no wear). Going forward, monitor with ECT and perform SSI to verify part configuration.
Object is hard deposit bridging and fixed in place. During 1 R31, ECT was NOD (no wear). Going forward, monitor with ECT and perform SSI to verify part configuration.
During 1 R31, affected and bounding tubes NOD (no wear). Part was retrieved at R31.
Item closed out at R31 and requires no action going forward.
During 1 R31, affected and bounding tubes NOD (no wear). Part was retrieved at R31.
Item closed out at R31 and requires no action going forward.
During 1 R31, part was retrieved at R31 from the NTL. No tubes affected. Item closed out at R31 and requires no action going forward.
SG-Item#
Description Location Configuration Irregular shaped object 1 R31 Irregular shaped R1-C47 wedged between C-52 object located at TSC R1-C48 center Tie Rod pedestal and first row of tubes R9-C39 C-53 1 R31 Small wire located Small wire embedded atTSH R10-C39 in sludge 1 R31 Small wires C-56 embedded in sludge R1-C48 Small wires embedded buildup at TSH R1-C49 in sludge buildup Parts captured in the (1 R31) Lancing strainer lancing strainers C-58 parts TIS during 1R31 TIS lancing ECT Results Estimated Size Fixity Retrieved at NDD 0.3" diameter 1R31 NDD Small wire Fixed NDD Mass of small Fixed wires Various parts Retrieved at N/A ranging from 1R31
-1/8" to -1/2" Serial No.24-346 Docket No. 50-280 page 22 of 24 2021 Disposition During 1 R31, affected and bounding tubes NDD (no wear). Part was retrieved at R31.
Item closed out at R31 and requires no action going forward.
During 1 R31, affected and bounding tubes NDD (no wear). SSI confirmed that part is fixed. Going forward, monitor with ECT and perform SSI to verify part configuration.
During 1 R31, affected and bounding tubes NDD (no wear). SSI confirmed that part is fixed. Going forward, monitor with ECT and perform SSI to verify part configuration.
During 1 R31, many objects were captured in the SGC lancing strainers. Most are sludge related. There were also fragments of small diameter wire and flex gasket material.
Serial No.24-346 Docket No. 50-280 page 23 of 24
- g. 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 1 SG.
- h. 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; and 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.
- i.
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 ONG ONT ECT EFPM EOC ETSS EWM FAC FOB FO FOSAR GPO HRS ISi LPM LPS MBM Serial No.24-346 Docket No. 50-280 page 24 of 24 Table 12 - Acronyms Accident Induced Leakage Performance Criteria NOD 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
ATTACHMENT 2 SURRY UNIT 2 Serial No.24-346 Docket No. 50-281 REVISED STEAM GENERATOR TUBE INSPECTION REPORT FOR THE SPRING 2023 REFUELING OUTAGE VIRGINIA ELECTRIC AND POWER COMPANY (DOMINION ENERGY VIRGINIA)
SURRY UNIT 2 REVISED STEAM GENERATOR TUBE INSPECTION REPORT FOR THE SPRING 2023 REFUELING OUTAGE Serial No.24-346 Docket No. 50-281 page 1 of 30 In accordance with Surry Power Station Unit 2 (SPS2) Technical Specification (TS) 6.6.A.3, Virginia Electric And Power Company (Dominion Energy) is submitting this Steam Generator Tube Inspection report which describes the results of the previously complete SPS1 Steam Generator (SG) examinations. During the SPS2 Spring 2023 End-of-Cyle 31 (EOC31) refueling outage (2R31), SG inspections were completed in accordance with TS 6.4.Q for all three SGs, designated as SG-A, SG-B, and SG-C. Based upon entry into Mode 4, exceeding 200°F, on June 06, 2023, a report was required to be submitted by December 03, 2023. Due to adopting a revised Technical Specifications, TSTF-577 Rev. 1, a revised Steam Generator Tube Inspection Report is required to be submitted within 30 days after implementation of the license amendment.
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 51F 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. rhe 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.
Surry Unit 2 Steam Generator Tube Inspection Report for Spring 2023 Refueling outage (Serial No.23-258) figure 10 contains the general arrangement and figures 11 and 12 contain a photo and illustration of the loose parts catching mechanism in the in the Feedwater Regulating Valves. 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.
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.
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.
Serial No.24-346 Docket No. 50-281 page 2 of 30 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 as detailed in the response for b. below.
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 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::: 2 Volts located in the hot leg straight section and 100% of all dents/dings 2::: 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.
Serial No.24-346 Docket No. 50-281 page 3 of 30 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, 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.
Serial No.24-346 Docket No. 50-281 page 4 of 30 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. The nondestructive examination techniques utilized for tubes with increased degradation susceptibility.
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. All high residual stress (HRS) tubes in SGs Band C (SG-A does not have HRS tubes) were examined full length with both Bobbin and Array probes and closely scrutinized during the analysis process due to the increased susceptibility of Stress Corrosion Cracking.
Table 1: Tubes with Potentially High Residual Stress SG Row Column No. Tubes A,
None 0
B 17 71 2
B 17 78 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
- c. For each degradation mechanism found:
- 1. The nondestructive examination techniques utilized; Serial No.24-346 Docket No. 50-281 page 5 of 30
- 2. The location, orientation (if linear), measured size (if available), and voltage response for each indication. For tube wear at support structures less than 20 percent through-wall, only the total number of indications needs to be reported;
- 3. A description of the condition monitoring assessment and results, including the margin to the tube integrity performance criteria and comparison with the margin predicted to exist at the inspection by the previous forward-looking tube integrity assessment; and
- 4. The number of tubes plugged during the inspection outage.
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.
The inspection program focused on the degradation mechanisms listed in Table 2 and utilized the referenced eddy current techniques.
Serial No.24-346 Docket No. 50-281 page 6 of 30 Table 2 - Inspection Method for Applicable Degradation Mechanism Classification Degradation Location Probe Type Mechanism Existing Wear Anti-Vibration Bars Bobbin - Detection and Sizing Existing Tube Wear (Foreign Freespan and TIS Bobbin and Array - Detection Obiects)
+Point' - Sizing Existing Wear Tube Support Plate (TSP)
Bobbin - Detection
+Point' - Sizinci Existing Wear Flow Distribution Baffle (FDB)
Bobbin - Detection
+Point' - Sizing Existing Circ. PWSCC Hot Leg TTS and Array - Detection Expansion Transition (EZ)
+Point' - Sizinci Existing Axial PWSCC Tubesheet Overexpansions (OXP)
Array - Detection
+Point' - Sizing Existing OD Pitting Top-of-Tubesheet (TTS)
Bobbin and Array - Detection
+Point' - Sizing Existing PWSCC Tube Ends N/A*
Potential ODSCC, PWSCC Row 1 and 2 U-bends
+Point' - Detection and Sizing Potential Axial ODSCC Freespan and Tube Supports Bobbin - Detection
+Point' - Sizing Potential Axial/ Circ. 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' - Sizinci Potential ODSCC Tubesheet Crevice in Tubes With N/A**
NTE Potential Tube Sliooage Within Tubesheet Bobbin - Detection Potential ODSCC, PWSCC High Residual Stress Tubes Bobbin and Array - Detection
+Point' - Sizing Inspection not required per technical specification alternate repair criteria
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 Wears 20% TW is contained in Table 4.
Serial No.24-346 Docket No. 50-281 page 7 of 30 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 C
38 30 AV2 0.88 21 20 C
39 53 AV3 1.69 30 28 C
39 55 AV3 1.42 26 24 C
39 55 AV4 1.32 25 23 C
40 33 AV2 1.25 26 25 C
40 33 AV3 1.28 25 25 C
43 61 AV1 1.03 23 22 Volumetric Non-AVB Wear 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 4 lists the 67 Non-AVB Wear indications with recorded wall
Serial No.24-346 Docket No. 50-281 page 8 of 30 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 performance criteria derived by conservatively accounting for material property uncertainties, model uncertainties, and NDE 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 4: 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.24-346 Docket No. 50-281 page 9 of 30 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 (in)
Volts Reported 0.29 0.13 2011 0.29 0.2 2011 0.32 0.26 2014 0.32 0.22 2014 0.32 0.25 2014 0.32 0.17 2009 0.26 0.12 2014 0.26 0.14 2015 0.21 0.1 2014 0.29 0.11 2009 0.34 0.12 2005 0.37 0.1 5 2005 0.34 0.21 2005 0.32 0.25 2005 0.37 0.26 2005 0.29 0.25 2005 0.32 0.36 2005 0.26 0.13 2015 0.48 0.73 2005 0.26 0.2 2011 0.21 0.16 2011 0.37 0.23 2011 0.32 0.22 2009 0.37 0.32 2005 0.29 0.2 2005 Foreign Cause Object Remaining TSP Wear N/A TSP Wear NIA Foreign Object No Foreign Object No Foreign Object No Foreign Object No TSP Wear N/A Foreign Object No Foreign Object No Foreign Object No Foreign Object No Foreign Object No Foreign Object No Foreign Object No Foreign Object No Foreign Object No Foreign Object No Foreign Object No Foreign Object No Foreign Object No Foreign Object No Foreign Object No Foreign Object No Foreign Object No Foreign Object 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.24-346 Docket No. 50-281 page 10 of 30 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 FDB 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 NIA No No No No No No No No No No NIA No No No No No NIA In Situ Tested No No No No No No No No No No No No No No No No No No Serial No.24-346 Docket No. 50-281 page 11 of 30 Plugged Stabilized No No No No No No No No No No No No No No No No No No
Stress Corrosion Cracking Serial No.24-346 Docket No. 50-281 page 12 of 30 No indications of stress corrosion cracking were identified in any of the Surry Unit 2 steam generators during 2R31.
Condition Monitoring 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 5-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.
- 2) The CM curve, itself, has built into it all three uncertainties using Monte Carlo methods.
Therefore, no arithmetic correction for NOE sizing uncertainty is required since it's built into the CM curve.
AVB Wear Table 6: A mixed Arithmetic/Monte Carlo methodoloav was used for CM of AVB wear.
Degradation Mechanism Maximum Limiting 95%/50%
CM Limit Depth (wear)
NOE Depth Upper Bound Depth 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
Serial No.24-346 Docket No. 50-281 page 13 of 30 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 c
J::
Q.
50 0
E i 40 "le CD
- E 30 w
0 z 20 10 0
0.0 Figure 2:
100 90 80 70
~ 60 c t 50 0
E 40 i
- E 30 w
0 z 20 10 0
0.0 I
- I I
0.2 0.4 ETSS27901.1 R1
-27901.1 R1 Foreign Object Wear 0.6 0.8 1.0 1.2 1.4 Length, (Inch)
CM Curve for Flaws Sized w/ETSS 27902.1 - Model: Axial Thinning w/Limited Circumferential Extent ETSS 27902.1 R1
-27902.1 RI Foreign Object Wear 0.2 0.4 0.6 0.8 1.0 1.2 1.4 Length, (Inch)
Serial No.24-346 Docket No. 50-281 page 14 of 30 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
~ a 50 a,
C E
40 E
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)
Figure 4: CM Curve for Flaws Sized w/ ETSS 96910.1 - Model: Axial Thinning w/Limited Circumferential Extent 100 ETSS 96910.1 R11 90
-96910.1 R11 TSP/ FDB Wear 80 70
[
60
~
.c a.
50 Cl)
C E
40 E
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)
Serial No.24-346 Docket No. 50-281 page 15 of 30 Table 7 illustrates that the current (EOC31) inspection results are bounded by the previous (EOC30) OA projections.
Table 7: Summary of Prior OA Validation Degradation Fall 2021, EOC30 Spring 2023, EOC31 Operational Mechanism Operational Assessment Assessment Maximum Observed Proiection at EOC31 AVBWear 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 ODSCCatTTS 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 atTSPs 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 GPD No measurable leakage observed Leakaae during Cycle-31 One tube in SG-A was plugged on a discretionary basis for an expansion transition signal exhibiting a smaller amplitude than the surrounding tubes during 2R31. No tubes were plugged in SG-B or SG-C.
- d. An analysis summary of the tube integrity conditions predicted to exist at the next schedule inspection (the forward-looking tube integrity assessment) relative to the applicable performance criteria, including the analysis methodology, inputs, and results; 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 (QA) 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 54 effective full power months or at least every other refueling outage (whichever
Serial No.24-346 Docket No. 50-281 page 16 of 30 results in more frequent inspections). All existing and potential degradation mechanisms were evaluated for a 3-cycle operating period over a 4.5 EFPY duration.
The following sections summarize the evaluations performed for existing degradation mechanisms as well as important potential degradation mechanisms.
Table 7 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 8 identifies the degradation specific OA methodology. Table 9 summarizes the EOC34 OA projections with comparisons to the applicable structural and leakage limits.
Table 8 - OA Methodoloav OA (Mechanism)
Methodoloav Structural Limit Note AVB Wear Mixed Arithmetic/Monte Carlo Structural Limit (61%TW) 1 FO Wear Plant Ooerating History TSP/FDB 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 NDE sizing}, four uncertainties must be considered (NDE, growth, burst relationship, and material properties). The Mixed Arithmetic/Monte Carlo methodology accounts for the four uncertainties as follows. The Arithmetic part accounts for NDE 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 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.
Serial No.24-346 Docket No. 50-281 page 17 of 30 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 9-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 Leakage TSP/FDB Wear 56.6%
52.8%TW 470 GPD Zero Maximum Depth Leakage Pitting Dormant. No oro*ected oittinq.
Circumferential PWSCC within 4470 psi 7314 psi 470 GPD Zero tubesheet expansion Leakaqe Circumferential ODSCC @
4470 psi 7045 psi 470 GPD Zero TTS Leakaqe Axial PWSCC within the 4470 psi 4626 psi 470 GPD Zero tubesheet Leakaqe Axial ODSCC @TSPs 4470 psi 5422 psi 470 GPD Zero Leakage Axial ODSCC @ (DNT/DNG) 4470 psi 5331 psi 470 GPD Zero Leakage AVB Wear 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(StdDev.). 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 (EOCUBD):
BOC32 = 39.7%TW maximum through-wall depth of in-service AVB wear at the beginning of Cycle 32
Serial No.24-346 Docket No. 50-281 page 18 of 30 EOCUBD = BOC32+(4.5 EFPY)(2.2 % TW/EFPY) end of cycle upper bound depth after three cycles EOCUBD = 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 RG1.121.
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 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.
Stress Corrosion Cracking 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.
~
- 0 Serial No.24-346 Docket No. 50-281 page 19 of 30 Figure 5: EOC34 Worst Case Burst Pressure of Circ PWSCC - Tubesheet Region 0.25 -.--------------------------~--------,
---* EOC34 Min BP 0.20 I
I I
I f
I I I
I I
I I
~ 0.15 I
I e
- a.
Q)
-~
]i 5 0.10
- J u 0.05 3XNOPD: 4470 psi I,
I I
Lower 95/50: 7314 psi I I I I a:
I I I I J 1
Probability: 0.05 --+----*
I fl I
,I I
/ I
,*' I I
, 1 I
0.00 +-----,-----r--.,__
1 ---.---
---.,-....---.--c:-.:::.-*_"..........,-....
- -----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 10 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 Serial No.24-346 Docket No. 50-281 page 20 of 30 Figure 6: EOC34 Worst Case Burst Pressure - Circumferential ODSCC @TTS 0.25...--------------------------,...------
i
---* EOC34 Min BP 0.20 I
I I
I I
I I I I '
I I
I I
~ 0.15 I I '
e
- a.
(D
-~,; 1 0.10
- I (J
0.05 I
I I
I Lower 95/50: 7045 psi
/ '
I I /
I '
I/,,,
3XNOPD: 4470 psi I
--r*---*
,' I I
,l I I
~#
I Prob: 0.05 I
0.00 +-----.------.---~
- -----...,-=-=-*.-*------.... *'-----~--------l 2,000 3,000 4,000 5,000 6,000 7,000 8,000 9,000 Projected EOCJ4 Worst Case Burst Pressure (psi)
Table 11: 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.24-346 Docket No. 50-281 page 21 of 30 Figure 7: EOC34 Worst Case Burst Pressure - Axial PWSCC within Tubesheet 0.25 -r-----------------------~, ---------,
0.20
~
- s t11 0.15
.c e ll..
Cl)
.ii! i
- i 0.10 E
- J u 0.05
EOC34 Min BP I,
I I,,
I ' '
I I,,,
' /,
Lower 95/50: 4626 psi I
I /
I I
I I
I 1,ll' 3XNOPD: 4470 psi 1 ->-------
Probability: 0.05
, ' I I
,,' I I
I I I
I
~.... - -****-
~
I 0.00 - --------=~ ----------~ -~--~--~--~---1 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 12: 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.24-346 Docket No. 50-281 page 22 of 30 Figure 8: EOC34 Worst Case Burst Pressure - Axial ODSCC @TSPs 0.25.,....------- --- ---------
--y- ----------,
0.20
~
- c n:i 0.15
.c e 0..
G) 2:
'li!i :i 0.10 e
- I
()
0.05 I ' '
I
EOC34 Min BP
/
I ' '
I I
I I
I I I I
Lower 95/50: 5422 psi I
I I,,,
I /
1,/
3XNOPD: 4470 psi 1
---~---------
Probability: 0.05 I
,, I I
I I
I t.. **"'
I I
0.00 +------aa.lL!!*=.=- :.=- =- ---~-*L..__~__J*L.._- ~---~---~-----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 13: 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.24-346 Docket No. 50-281 page 23 of 30 Figure 9: EOC34 Worst Case Burst Pressure - Axial ODSCC @Dents/Dings 0.25 ~-----------------~
~
0.20 5 i 0.15
,g e
- n.
Q)
.i:!:
iii
- i 0.10 e
- J u 0.05
EOC34 Min BP I I I
I I
I I
I r I r I r I I,
I I
I,
I I
I '
Lower 95/50: 5331 psi 3XNOPD: 4470 psi I
I,'
I,'
I,'
,'I
,/ I I
I I
I Probability: 0.05 11-,--
I 0.00 +-----
- --~---=- -=---_,.__~_..__
. ______ ~----------!
2,000 3,000 4,000 5,000 6,000 7,000 8,000 9,000 Projected EOC34 Worst Case Burst Pressure (psi)
Table 14: 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
- e. The number and percentage of tubes plugged to date, and the effective plugging percentage in each SG; Table 15 provides the plugging totals and percentages to date.
Table 15 - 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
% Plm.u?: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.
- f.
The results of any SG secondary side inspections; Foreign Objects Serial No.24-346 Docket No. 50-281 page 24 of 30 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 16: 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 Legacy small LPS Deposit: Not Historical LPS deposit Recorded and RI0-C47, RI l-C47 A-2 on tube OD and 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.24-346 Docket No. 50-281 page 25 of 30 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-CI0, R22-CI0 2003 bolt like B-1 Legacy R22-Cl 1, R21-Cl 1 object. Four Bounding Bolt Like Object affected tubes tubes NDD 02C+0.65 plugged/stabilized R44-C46, R43-C46, Partial shank of B-2 Partial shank of bolt NDD R43-C45, R44-C45 bolt 201 7 sludge rock R5-C88, R6-C88 Sludge Rock I Disc and 2018-disc C-1 R6-C89 shaped object LPS Shaped Object affixed to the TSC +0.00 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.24-346 Docket No. 50-281 page 26 of 30 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 Deposit Bridging Deposit Bridging PLPs TSH +0.00 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.24-346 Docket No. 50-281 page 27 of 30 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 Estimated Size R36-C51, R3 5-CS l 2021 Entangled Wire R34-C51, R36-C52
~3 tubes C-5 Entangled Wire NDD Mass (EWM)
R35-C52, R34-C52 by 2 tubes Mass (EWM)
TSH +0.50 2021 Embedded Wire in R34-C5 l, R34-C50 Wire like object 1.50" length C-6 NDD 0.12" depth hard sludge TSH +0.25 embedded in hard 0.12" width sludge Sludge and R3 l-C54, R31-C55 Spanning C-7 Entangled wire mass TSH +0.00 2023 Wire mass NDD Multiple (EWM) tubes Fixity Partially Fixed in Place Fixed Fixed Serial No.24-346 Docket No. 50-281 page 28 of 30 2023 Disposition During 2021 FOSAR identified a EWM ( originally logged as being part of FOTS item #72 but broke out as separate FOTS item #84 ).
FOSAR broke the mass apart for subsequent removal by lancing.
During 2023 some remnants of the EWM still remain on the TIS 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 2R3 l sludge and EWM found and verified fixed in place.
ECT was NDD. No tube wear. At the next ISi continue to monitor with ECT and SSL
Serial No.24-346 Docket No. 50-281 page 29 of 30
- g. 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.
- h. 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; and 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.
- i.
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.24-346 Docket No. 50-281 page 30 of 30 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 Baffie 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 Bame 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