DCL-06-129, Special Report 06-03 - 180 Day Report for Steam Generator Technical Specification Task Force 449, Thirteenth Refueling Outage

Special Report 06-03 - 180 Day Report for Steam Generator Technical Specification Task Force 449, Thirteenth Refueling Outage

ML063320484
Person / Time
Site:	Diablo Canyon
Issue date:	11/17/2006
From:	Jacobs D Pacific Gas & Electric Co
To:	Document Control Desk, Office of Nuclear Reactor Regulation
References
DCL-06-129, NEI 97-06, Rev 2, OL-DPR-82, SR-06-03, TSTF-449, Rev 4
Download: ML063320484 (52)

Text

V,* Pacific Gas and Electric Company D Donna Jacobs tirablo Canyon Power Plant Vice President P. 0. Box 56 Nuclear Services Avila Beach, CA 93424 805.545.4600 November 17, 2006 Fax: 805.545.4234 PG&E Letter DCL-06-129 U.S. Nuclear Regulatory Commission ATTN: Document Control Desk Washington, DC 20555 Docket No. 50-275, OL-DPR-82 Diablo Canyon Unit 2 Special Report 06 180 Day Report for Steam Generator Technical Specification Task Force (TSTF) 449 for Diablo Canyon Power Plant Unit 2 Thirteenth Refueling Outage

Dear Commissioners and Staff:

Pursuant to NEI 97-06 Revision 2, "Steam Generator Program Guidelines," and Technical Specification Task Force (TSTF) 449, Revision 4, Enclosure 1 provides the 180-day reporting of steam generator (SG) condition monitoring for non-alternate repair criteria (ARC) degradation mechanisms. The operational assessment is also provided for information only.

Pacific Gas and Electric Company (PG&E) Letter DCL-06-100 dated August 21, 2006, provided the 90-day and 120-day reporting of condition monitoring and operational assessment for ARC degradation mechanisms.

PG&E has identified an error in the circumferential indication depth adjustment processing software inputs that were used for reporting depths in Table 6 and Figure 4 of Enclosure 1 to DCL-06-100. The circumferential indication depth measurements in the attached Table 5 reflect corrections made to the software inputs and supersede the depths listed in Table 6 and Figure 4 of Enclosure 1 of DCL-06-1 00. The changes are minor, and do not alter any of the conclusions or actions associated with primary water stress corrosion cracking ARC contained in DCL-06-100.

If you have any questions, please contact John Arhar at (805) 545-4629.

Sincerely, Donn cobs A member of the STARS (Strategic Teaming and Resource Sharing) Alliance A*)ol Callaway

• Comanche Peak ° Diablo Canyon

• Palo Verde

• South Texas Project e Wolf Creek

Document Control Desk PG&E Letter DCL-06-129 November 17, 2006 Page 2 ddml/469/A0660367 Enclosures cc: Alan B. Wang, Project Manager NRR Diablo Distribution cc/enc: Bruce S. Mallett, NRC Region IV Terry W. Jackson, NRC Senior Resident State of California, Pressure Vessel Unit A member of the STARS (Strategic Teaming and Resource Sharing) Alliance Callaway

• Comanche Peak

• Diablo Canyon

• Palo Verde ° South Texas Project

• Wolf Creek

Enclosure 1 PG&E Letter DCL-06-129 STEAM GENERATOR CONDITION MONITORING AND OPERATIONAL ASSESSMENT REPORT DIABLO CANYON POWER PLANT (DCPP)

UNIT 2 THIRTEENTH REFUELING OUTAGE 1.0 TSTF-449 Reporting Requirements Pursuant to Nuclear Energy Institute (NEI) 97-06, Revision 2, "Steam Generator Program Guidelines," submittal of reports consistent with Technical Specification Task Force (TSTF) 449, Revision 4, is required. Pursuant to TSTF-449, a report shall be submitted within 180 days after initial entry into Mode 4 following completion of an inspection performed in accordance with Technical Specification (TS) 5.5.9, "Steam Generator (SG) Tube Surveillance Program."

Pacific Gas and Electric Company (PG&E) letter DCL-06-100 dated August 18, 2006, was submitted to the NRC to document the Unit 2 Thirteenth Refueling Outage (2R1 3) condition monitoring and operational assessment (CMOA) for SG alternate repair criteria (ARC) damage mechanisms. This enclosure documents the CMOA report for non-ARC damage mechanisms.

The specific TSTF-449 reporting requirements are listed in italics below, followed by PG&E's description of compliance.

• The scope of inspections performed on each steam generator(SG).

Table 1 provides a summary of eddy current inspections performed in each SG.

" Active damage mechanisms found.

The following active ARC damage mechanisms were found, and CMOA is documented in DCL-06-100:

o Axial primary water stress corrosion cracking (PWSCC) in hot leg WEXTEX tubesheet region o Axial PWSCC at hot leg dented tube support plate (TSP) intersections o Axial outside diameter stress corrosion cracking (ODSCC) at hot leg TSP intersections The following active non-ARC damage mechanisms were found:

o Circumferential ODSCC and PWSCC at hot leg dented TSP intersections o Combined axial PWSCC and axial ODSCC at hot leg dented TSP intersections (referred to as inside diameter/outside diameter (ID/OD) indications) o Axial ODSCC at free span dings 1

Enclosure 1 PG&E Letter DCL-06-129 o Circumferential ODSCC at hot leg WEXTEX top of tubesheet region o Axial PWSCC in Row 1 U-bends o Circumferential PWSCC in U-bend flank locations o Cold leg thinning at cold leg TSP intersections o Antivibration bar (AVB) wear in U-bend region o TSP ligament thinning/cracking o Combined axial PWSCC and circumferential indications at hot leg dented TSP intersections (referred to as PWSCC mixed mode indications)

• Nondestructive examination techniques utilized for each degradationmechanism.

Table 1 provides the nondestructive examination (NDE) techniques (bobbin and Plus Point probes) utilized for each inspection category. The degradation-specific analyses in this enclosure provide more detailed discussion of the probes used to identify and size the degradation mechanism.

• Location, orientation (if linear), and measured sizes (if available) of service induced indications.

The degradation-specific condition monitoring (CM) analysis provides a discussion of the location, orientation, and measured sizes of service induced indications.

• Number of tubes plugged during the inspection outage for each active degradation mechanism.

Table 2 provides the number of tubes plugged during 2R1 3 for each active degradation mechanism. The cumulative number of tubes plugged for each degradation mechanism is shown in Table 3 (by SG) and Table 4 (by outage).

A total of 70 tubes were plugged. Framatome-ANP alloy 690 roll plugs were used in both legs. Tubes with circumferential indications were evaluated for stabilization prior to plugging. Westinghouse stabilization analysis determined that three tubes required stabilization (see Table 5), and tubesheet stabilizers were inserted in these tubes before plugging.

Total number and percentage of tubes plugged (or repaired)to date.

Table 2 provides the total number and percentage of tubes plugged to date, by SG and overall. No tubes have been repaired by sleeving.

The results of condition monitoring, including the results of tube pull and in-situ testing.

Section 4 provides the degradation-specific results of condition monitoring and operational assessment for all active non-ARC damage mechanisms, as identified 2

Enclosure 1 PG&E Letter DCL-06-129 earlier, with the exception of PWSCC mixed mode indications at hot leg dented TSP intersections, which is provided in DCL-06-100. DCL-06-100 also provides CMOA for all ARC damage mechanisms. There were no tube pulls or in-situ testing performed in 2R13.

Section 5 provides the results of 2R1 3 inspections and operational assessment for potential degradation mechanisms that were not detected in 2R1 3, as listed below.

o Circumferential PWSCC in Row 1 U-bends (see Section 4) o Circumferential PWSCC in hot leg WEXTEX top of tubesheet region o ODSCC mixed mode indications at hot leg dented TSP intersections o Axial ODSCC in hot leg top of tubesheet region o Secondary side integrity and potential tube damage due to loose parts and foreign object o Axial PWSCC in high row U-bends 2.0 Background Steam GeneratorDescription The commercial operation dates for Units 1 and 2 are May 1985 and March 1986, respectively. Diablo Canyon Power Plant (DCPP) Units 1 and 2 use Westinghouse Model 51 SGs with explosively expanded (WEXTEX) transitions. The SGs contain Alloy 600 Mill Annealed tubing. The nominal outside diameter of the tubing is 0.875 inch with a 0.050 inch nominal wall thickness. DCPP Unit 1 and 2 SGs currently operate with a nominal hot leg temperature (Thot) of about 604 degrees. The cycle lengths vary to support a nominal 20-month operation period. Unit 2 Cycle 13 had an actual duration of 1.31 effective full power years (EFPY). Unit 2 Cycle 14 has a projected duration of 1.62 EFPY.

PG&E has implemented several initiatives to minimize PWSCC and ODSCC. Primary side initiatives include U-bend heat treatment, WEXTEX tubesheet shotpeening, and zinc injection. Secondary chemistry initiatives include: copper removal program; ethanol amine to control pH; increased hydrazine levels; molar ratio control program to prevent excess alkalinity; boric acid addition program (including boric acid soaks at startup to mitigate denting and ODSCC at TSPs); periodic tube sheet sludge lancing; SG blowdown is maintained at one percent of the main steam flow rate; condensate polishers were installed and emergency (plant curtailment) procedures issued to protect against seawater condenser tube leaks; chemical cleaning in Unit 1 Twelfth Refueling Outage (1R12) and Unit 2 Twelfth Refueling Outage (2R12).

Technical Specification Repair Criteria DCPP TS require plugging of any tube that has degradation greater than or equal to 40 percent of the nominal tube wall thickness, unless ARC are implemented. Other 3

. Enclosure 1 PG&E Letter DCL-06-129 than degradation subject to ARC, all crack-like indications are required to be plugged on detection by a rotating coil probe, regardless of depth measurements. Cold leg thinning and AVB wear are sized by bobbin and allowed to remain in service if less than 40 percent throughwall (TW).

Several ARC are implemented in DCPP Units 1 and 2:

• In March 1998, the DCPP TS were revised to allow implementation of ARC for ODSCC at TSPs pursuant to NRC Generic Letter (GL) 95-05, "Voltage-Based Repair Criteria for Westinghouse Steam Generator Tubes Affected by Outside Diameter Stress Corrosion Cracking." ODSCC ARC was implemented starting in Unit 2 Eighth Refueling Outage (2R8) for Unit 2 and Unit 1 Ninth Refueling Outage (1 R9) for Unit 1. The ODSCC ARC TS changes were granted by the NRC in License Amendment (LA) 124/122 dated March 12, 1998, in response to License Amendment Request (LAR) 97-03. Use of an improved probability of detection (POD) method, referred to as probability of prior cycle detection, was approved for both units in LA 177/179 dated October 28, 2004, in response to LAR 04-01.

• In February 1999, the DCPP TS were revised to allow implementation of Wstar (W*)

ARC for axial PWSCC in the WEXTEX tubesheet region. W* ARC was implemented starting in 1R9 and Unit 2 Ninth Refueling Outage (2R9). The W* ARC TS for Cycles 10 and 11 were granted by the NRC in LA 129/127 dated February 19, 1999 (in response to LAR 97-04). The W* ARC TS for Cycles 12 and 13 were granted by the NRC in LA 151 dated April 29, 2002 (in response to LAR 01-03). Use of W* ARC on a permanent basis beyond Cycle 13 was granted by the NRC in LA 182/184 dated October 28, 2005 (in response to LAR 05-01).

" In May 2002, the DCPP TS were revised to allow implementation of ARC for axial PWSCC at dented TSPs. The PWSCC ARC TS changes were granted by the NRC in LA 152 dated May 1, 2002 (in response to LAR 00-06, Supplement 3). PWSCC ARC was implemented starting in Unit 2 Eleventh Refueling Outage (2R1 1) and Unit 1 Eleventh Refueling Outage (1 R1 1). Validated depth sizing of axial PWSCC at dented TSP intersections was previously implemented in 1 R9 and Unit 1 Tenth Refueling Outage (1 R10) for Unit 1; and 2R9, and Unit 2 Tenth Refueling Outage (2R1 0) for Unit 2, such that axial PWSCC less than the TS limit of 40 percent maximum depth (MD) limit was allowed to remain in service.

NRC Reporting for Category C-3 Reporting During 2R! 3, greater than one percent of inspected tubes in SG 2-4 were defective and required plugging, thus the results of the SG tube inspections were classified as Category C-3. To satisfy DCPP Technical Specification TS 5.5.9, Table 5.5.9-2, PG&E notified the NRC in accordance with 10 CFR 50.72. In addition, PG&E submitted Licensee Event Report 2-2006-002 to the NRC via PG&E Letter DCL-06-068 dated May 19, 2006, to report this condition as required by TS 5.6.10.c.

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Enclosure 1 PG&E Letter DCL-06-129 3.0 Condition Monitoring and Operational Assessment Summary NEI 97-06, Revision 2, provides structural integrity performance criteria (SIPC),

accident induced leakage integrity performance criteria (AILPC), and operational leakage performance criteria. These performance criteria were satisfied at the Unit 2 End of Cycle (EOC) 13 based on a condition monitoring assessment, and are projected to be satisfied at EOC 14 based on an operational assessment. This conclusion is based on assessing the conditions of the SG tubing on a degradation-specific basis.

Structural Integrity Performance Criteria:

Three times normal operating pressure differential (3dPNO) and 1.4 times steam line break differential pressure (1.4dPSLB) are the burst margin requirements for free span degradation, and degradation confined to the TSP crevice, respectively. SIPC are satisfied at EOC 13 and EOC 14. (Note: See DCL-06-1 00, Enclosures 1,2, and 3 for discussion of W* ARC, PWSCC ARC, and GL 95-05 voltage-based ARC, respectively).

Accident-Induced Leakage Integrity Performance Criteria:

" For degradation subject to ARC, the maximum allowable steam line break (SLB) induced leak rate limit is 10.5 gallons per minute (gpm) in a faulted SG, based on an analysis which uses current licensing basis assumptions and is approved by the NRC. As described in Enclosure 1 to DCL-06-100, the aggregate SLB leak rate from ARC degradation and non-ARC degradation in the limiting SG is 1.193 gpm (at EOC 13) and 5.695 gpm (at EOC 14). These leak rates are less than the 10.5 gpm acceptance limit. Therefore, AILPC for ARC degradation are satisfied at EOC 13 and EOC 14

• For degradation not subject to ARC, the maximum allowable SLB-induced leak rate is one gpm in a faulted SG. There is no SLB leakage attributed to any non-ARC degradation at EOC 13 and EOC 14. Therefore, AILPC for non-ARC degradation are satisfied at EOC 13 and EOC 14.

Operational leakage performance criterion: Primary-to-secondary leakage through any one SG must be limited to 150 gallons per day (gpd). This limit is reflected in DCPP TS.

In Unit 2 Cycle 13, a small 0.4 gpd primary to secondary leak rate was again detected in December 2004 by routine monitoring, as indicated by noble gas in the steam jet air ejector (SJAE) exhaust. Chemistry determined that SG 2-4 had the highest relative leak rate (less than 0.2 gpd), with very low leakage detected in the other 3 SGs.

Leakage in other SGs could be low level leakage in those SGs, or cross-over leakage from SG 2-4. In Unit 2 Cycle 14, a similar small leak rate of about 0.2 gpd was detected in July 2006, shortly after startup following 2R13.

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Enclosure 1 PG&E Letter DCL-06-129 The source of the small leakage was not detected by eddy current inspections in 2R13.

The source could be attributed to some of the larger voltage crack-like indications that are in service under TSP and tubesheet ARC. ARC indications confined to the TSP crevice and WEXTEX tubesheet have a low probability to contribute to significant operational leakage due to the tight TSP and tubesheet constraints. Another potential source of leakage is from plugged tubes. For example, SG 2-4 has four tube remnants for tubes that have been cut and removed for destructive examination (2 in 2R8 and 2 in 2R1 1). For each of these four tubes, the hot leg tubesheet hole is plugged with a weld plug, and the cold leg tube portion is plugged with a mechanical roll plug. The roll plugs are leak limiting, so with an open tube remnant, it is possible that some leakage past the plug could escape to the secondary side.

4.0 Degradation-Specific Condition Monitoring and Operational Assessment for Active Non-ARC Damage Mechanisms 4.1 Circumferential ODSCC and PWSCC at Dented TSP Intersections (Active)

Condition Monitoring Fourteen circumferential ODSCC indications and two circumferential PWSCC indications were detected by Plus Point at dented hot leg TSP intersections, as listed in Table 5. All the circumferential indications (SCI) were plugged. All of the dent voltages associated with circumferential cracking were greater than 4 volts.

Circumferential PWSCC and ODSCC indications at dented TSPs are capable of being detected by Plus Point using EPRI ETSS 20510.1 and 22842.3, respectively.

The circumferential indications were sized by Plus Point using the technique described in Appendix B of WCAP-1 5573, Revision 1. The depth profiles were then processed for corrections in accordance with the depth adjustment rules in Section 4.10.4 of WCAP-1 5573, Revision 1. The adjusted NDE results were corrected for 95 percentile NDE uncertainty using the NDE uncertainty regression parameters in WCAP-15573, Revision 1. The adjusted NDE and adjusted NDE with uncertainty results are listed in Table 5.

PG&E identified an error in the depth adjustment processing software inputs subsequent to submittal of the PWSCC ARC 90 day report, such that Table 6 and Figure 4 of Enclosure 1 of DCL-06-100 (PWSCC ARC 90 day report) provide incorrect adjusted depths of circumferential indications. The adjusted depth measurements in Table 5 reflect corrections made to the software inputs. Table 5 supersedes Table 6 of of DCL-06-100. Likewise, the adjusted circumferential depths in Table 5 for SG 2-2 R10 C30 1H supersede the depths shown in Figure 4 of Enclosure 1 of DCL-06-1 00. The changes are minor, and do not alter any of the conclusions or actions associated with primary water stress corrosion cracking ARC contained in DCL-06-1 00.

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Enclosure 1 PG&E Letter DCL-06-129 The 3dPNO structural limit for a straight leg SCI is 265 degrees, assuming a 100 percent TW defect, and 73.5 percent degraded area (PDA). From Table 5, the longest NDE length was 52.6 degrees, and is adjusted to 182.2 degrees after applying large 95 percentile NDE uncertainties. This length is less than the 265 degree structural limit.

Therefore, structural integrity was satisfied at EOC 13.

The maximum Plus Point voltages of the 2R13 TSP circumferential ODSCC and PWSCC indications were 0.57 volt and 0.44 volt, much less than the 1.31 volts and 1.25 volts thresholds for leak testing of circumferential ODSCC and PWSCC indications at explosive expansions, respectively, documented in Revision 2 of the EPRI In-Situ Pressure Test Guidelines. The associated maximum NDE MDs of these bounding flaws, including 95 percent NDE uncertainty, were 64.3 percent (ODSCC) and 92.5 percent (PWSCC). Therefore, no SLB leakage should be postulated for circumferential indications at EOC 13.

OperationalAssessment All TSP intersections containing circumferential ODSCC and circumferential PWSCC were also inspected by Plus Point in 2R12. Most of the indications were detectable in 2R12 data based on a lookup, with the exception of four circumferential ODSCC indications. The growth rates were very small as noted in Table 5. Adding these 2R13 growth rate data points to the existing database from WCAP-1 5573, Revision 1, plus data points from 1R11, 2R11, 1R12, 2R12, and Unit 1 Thirteenth Refueling Outage (1 R1 3), results in the following growth rates.

Post-2R13 95 Percentile Growth Rates per EFPY for TSP Circumferential Indications PWSCC ODSCC Average Depth 10.3% 6.4%

Maximum Depth 16.6% 7.0%

Length 12.7 deg 17.7 deg Number of DCPP data points 27 54 in growth distribution The limited data would indicate that PWSCC depth growth rates are larger than ODSCC. ODSCC growth is conservatively assumed to be the same as PWSCC.

The average depth (AD) growth data at 95 percent cumulative probability can be combined with the estimated detection thresholds derived from destructive examination (25 percent and 35 percent AD detection thresholds estimated for PWSCC and ODSCC, respectively, per WCAP-1 5573, Revision 1, Section 4.11, no NDE uncertainty is necessary) to obtain a deterministic projection of expected EOC 14 ADs for circumferential indications, as given in the following table.

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Enclosure 1 PG&E Letter DCL-06-129 Average Depth EOC Projected TSP Circumferential Indications PWSCC ODSCC Detection threshold for Average Depth 25% 35%

+95% AD growth over 1.62 EFPY cycle 17% 17%

Projected EOC 14 Average Depth 42% 52%

Largest found at 2R13 51.3% 69.8%

Assuming that the worst case projected flaw is 52 percent AD over 360 degrees results in a conservative EOC 14 projection of 52 PDA. This conservative projection is less than the straight leg circumferential indication structural limit of 73.5 PDA. Since the largest circumferential crack angle at 2R1 3 was 182.2 degrees including adjustment for angle uncertainty at 95 percent probability, the assumption that the projected EOC 14 indication is 360 degrees is very conservative.

Similar to above, the MD growth data at 95 percent cumulative probability can be combined with the estimated detection thresholds based on the minimum values used in the sizing adjustment procedures (45 percent and 35 percent MD for ODSCC and PWSCC, respectively, per WCAP-1 5573, Revision 1, Section 4.10.4, no NDE uncertainty is necessary) to obtain a deterministic projection of expected EOC 14 MDs, as given in the following table.

Maximum Depth EOC Projected TSP Circumferential Indications I PWSCC ODSCC Detection threshold for Maximum Depth 35% 45%

+95% MD growth over 1.62 EFPY cycle 27% 27%

Projected EOC 14 Maximum Depth 62% 72%

Largest found at 2R1 3 79% 86%

The projected EOC 14 MDs of 62 and 72 percent present no challenge to SLB leakage integrity.

A review of the 2R1 3 as found circumferential indications was performed to validate the OA methodology, and it was determined that four 2R1 3 indications had maximum and AD combinations that were under predicted. Three 2R13 ODSCC indications had ADs greater than 52 percent and MDs greater than 72 percent. One 2R13 PWSCC indication had an AD greater than 42 percent and a MD greater than 62 percent. No adjustments to the operational assessment (OA) method are deemed necessary for the following reasons: The under predicted indications have small maximum Plus Point voltages (less than or equal to 0.44 volt) which could result in overly-conservative depth estimates at small amplitudes, and also have short lengths (less than or equal to 31.5 degrees) which do not challenge structural integrity. In addition, the OA methodology conservatively assumes the projected AD applies to a 360 degree indication.

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Enclosure 1 PG&E Letter DCL-06-129 Based on the comprehensive inspection of dented TSP intersections during 2R13, the slow rate of circumferential degradation growth, acceptably low detection threshold, limited maximum angular extent associated with circumferential cracks, and the large structural margin associated with circumferential indications, no TSP circumferential indications are expected that would challenge structural performance criteria at EOC 14. Since the largest projected MD is not near TW, it is also unlikely that TSP circumferential indications will tear ligaments and pop through over the next cycle.

Therefore, no leakage is postulated in a faulted SG following a SLB at EOC 14.

4.2 Combined Axial PWSCC and Axial ODSCC at Dented TSP (Active)

Condition Monitoring Table 6 provides a list of all tubes with combined axial PWSCC and axial ODSCC (ID/OD) indications through 2R13. In 2R13, two tubes were identified by Plus Point with ID/OD indications located at the same dented TSP intersection. These tubes were plugged because this type of flaw combination is excluded from both PWSCC ARC and ODSCC ARC application. One of the axial ODSCC indications had been left in-service in 2R1 2 using the ODSCC ARC, and the other was new. Both of the axial PWSCC indications were new.

PG&E Letter DCL-02-098 to the NRC dated August 22, 2002, derived a bounding conservative hoop direction ligament length of 0.1 inch (two times the tube wall thickness of 0.050 inch), such that if this separation distance is met or exceeded, there is no interaction relative to either burst pressure or leak rate.

Based on review of the eddy current data and terrain maps for all 2R1 3 ID/OD intersections, the axial PWSCC and axial ODSCC components are separated by hoop direction ligament gaps. Table 6 provides the separation gap distances (angles) between the ID and OD indications detected in 2R13, as well as all prior inspections.

For TSPs with multiple ID or OD indications, the smallest (minimum) separation angle is provided. The shortest 2R13 gap is 64 degrees (about 0.49 inch). This separation distance exceeds the required hoop direction ligament thickness of 0.1 inch. Therefore, for condition monitoring, the flaws are treated independently under theirrespective ARC for structural and leakage integrity.

OperationalAssessment Extent of Inspection at Dented TSP Intersections All ID and OD bobbin indications in any size dent were Plus Point inspected. In addition, a detailed Plus Point inspection program of dented intersections was conducted, which included 100 percent inspection of greater than 2 volts dents up to coldest TSP elevation with any PWSCC indication, plus 20 percent at the next coldest TSP elevation.

9,

Enclosure 1 PG&E Letter DCL-06-129 Based on the extent of the inspection and repair of all detected combined ID/OD indications, any potential combined PWSCC and ODSCC indications left in service at dented TSP intersections would have one of the indications below the detection threshold of the Plus Point coil or both of the ID/OD indications would be new indications. The Plus Point detection threshold is expected to be less than 30 percent and 20 percent MD for ODSCC and PWSCC axial indications, respectively. As a consequence of the low detection thresholds and modest crack depth and length growth rates for both axial PWSCC and ODSCC, deep new indications would not be expected at EOC 14.

Number of Occurrences of Combined Axial PWSCC and ODSCC Indications All data on combined ID/OD indications through 2R13 are given in Table 6. A total of 101 TSP intersections have been identified with combined ID/OD indications, 12 for Unit 2 and 89 for Unit 1. Fifty-two of these TSP intersections were in tubes that were previously inactive, i.e., tubes that were deplugged and then replugged in the same outage. Therefore, only 49 TSP intersections were in active tubes at the time the ID/OD indications were detected.

Dependence of Combined Axial PWSCC and ODSCC Indications on Dent Volta-qe The vast majority of the ID/OD intersections have small dents, less than 5 volts. Only two intersections have greater than 5 volts dents, and these are in deplugged tubes.

The dominance of axial ODSCC at non-dented TSP intersections or intersections with small dents is expected based upon experience in eddy current examination of greater than 5 volts dents as part of ODSCC ARC applications. Few indications have been reported in greater than 5 volts dents under ARC applications for many plants. For DCPP Units 1 and 2, axial ODSCC has been detected in only 24 intersections with greater than 5 volts dents, with the first occurrences in 1 R9 and 2R9, none in 2R1 1, six in 1R12, one in 2R12, four in 1R13, and two in 2R13. This number is small when compared to the large number of Plus Point inspections of greater than 5 volts dents, and also small when compared to the number of ODSCC signals detected in both units (greater than 1000 indications in each unit since 1R11/2R11). When the intersection is highly dented, corrodents can be expected to have increased difficulty in concentrating within the crevice, and axial ODSCC is very infrequent in large dents. Consequently, the potential occurrence of combined ID/OD indication can be expected to be dominantly limited to dents less than 5 volts as supported by DCPP Units 1 and 2 inspection results. This limits the potential population of TSP intersections with significant potential for combined ID/OD indications, and also increases the likelihood of bobbin detection in less than 5 volts dents.

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Enclosure 1 PG&E Letter DCL-06-129 Crack Sizes for Combined Axial PWSCC and ODSCC Indications Table 6 provides the Plus Point sizing of all PWSCC indications at TSP intersections with ODSCC indications, along with the Plus Point and bobbin voltages for the ODSCC indications. The listed bobbin voltage is either the bobbin distorted OD signal (DOS) indication voltage or, if the bobbin indication was not detectable, an inferred voltage based on the square root of the sum of squares of the all the Plus Point ODSCC voltages. The largest maximum and ADs for the PWSCC indications in previously active tubes at these intersections are shallow, only 60 percent and 48 percent, respectively. New PWSCC indications are also small as discussed below. The largest voltages for the ODSCC indications at intersections with PWSCC in active tubes are 4.58 bobbin DOS volts, which is influenced by both the PWSCC and ODSCC axial cracks, and 2.66 Plus Point volts (2R1 1 SG 2-2 R22C67). The 4.58 bobbin voltage is well below the ODSCC ARC structural limit of about 9 volts, and would have less than a 50 percent probability of leaking as a free span indication, per the ODSCC ARC correlations. The 2.66 Plus Point volts is less than the 2.75 volts threshold applied for amplitude sizing of ODSCC indications that has been found to result in good agreement with DCPP pulled tube TW lengths. The other ID/OD indications are small, and it can be expected that all indications found to date at TSP intersections with combined ID/OD cracks have large structural margins and no leakage.

New Indication Crack Sizes and Growth Rates New indication crack sizes are of interest for assessing potential interaction between the ID and OD indications, because one or both indications must be a new indication.

Both the ID and OD new indications are small.

From DCL-06-1 00: The largest maximum and ADs for all new PWSCC indications at any TSP intersection in 2R1 3 are 45 percent and 34.9 percent, respectively; the largest new ODSCC indication at any TSP intersection in 2R13 has a bobbin coil voltage of 1.40 volts; and the average ODSCC bobbin voltage for new indications in 2R1 3 is 0.37 volt, excluding axial ODSCC not detectable by bobbin (AONDB) indications.

From Table 6, the largest new ODSCC indication at a TSP with ID/OD indications had a bobbin DOS voltage of 1.29 volts, which is influenced by both the PWSCC and ODSCC indications, and a largest Plus Point voltage of 0.38 volt. The largest new PWSCC indication at a TSP with ID/OD indications had a MD of 51 percent.

Since both the new PWSCC and ODSCC indications are small, the structural influence of a new ID or OD indication interacting with an indication left in service would be small even under the very low likelihood of closely spaced indications.

From DCL-06-100, the PWSCC MD, AD, and length growth rate distributions from Unit 2 Cycle 13 are small. The upper 95 percent growth rate for new and repeat ODSCC indications in Unit 2 Cycle 13 is 0.18 volt/EFPY and 0.31 volt/EFPY, respectively, 11

Enclosure 1 PG&E Letter DCL-06-129 showing that new indication growth is smaller than growth for prior indications. Based on the modest growth rates for new PWSCC and ODSCC indications, any new indications occurring to obtain combined ID and OD flaws at the same intersection would continue to be small indications.

Separation Distances Between Axial PWSCC and ODSCC Indications Based on review of the eddy current data and terrain maps for DCPP Units 1 and 2 intersections with combined ID/OD indications, the axial PWSCC and axial ODSCC components are separated by hoop direction ligament gaps in excess of about 30 degrees (0.23 inch). The angles separating the PWSCC and ODSCC indications are given in Table 6. For TSP with multiple indications, the reported angle is the minimum separation distance. The separation distances are measured as distances between the peak amplitude responses, which is preferred given the width of a rotating pancake coil response. The lowest separation angle found in DCPP Units 1 and 2 is 34 degrees (0.26 inch), found at 1 R1 1. The separation angles between axial PWSCC and ODSCC indications are predominantly in the 40 to 90 degree range. This range of separation angles can be expected based upon the,separation distances between the locations of maximum hoop stress on the tube ID and OD at dented TSP intersections, as previously discussed in DCL-02-098.

Conclusions Relative to Closely Spaced Axial PWSCC and ODSCC Indications at Dented TSP Intersections Based on the assessments provided in PG&E Letter DCL-02-98, the potential for closely spaced axial PWSCC and ODSCC macrocracks at the same dented TSP intersection is negligible due to the high compressive OD hoop stresses near the minor axis of dent ovalization where the PWSCC occurs. Even the potential for shallow ODSCC microcracks is negligible unless formed prior to the denting, which occurred in the first cycle of operation for the DCPP SGs. Consequently, combined PWSCC and ODSCC indications at the same dented TSP intersection would have no impact on the operational assessment, and separate operational assessments for the individual indications are appropriate.

4.3 Axial ODSCC at Free Span Dings (Active)

Condition Monitoring Two axial ODSCC indications were reported by bobbin as ding with indication (DNI) at small voltage free span dings located in the cold leg lower elevations, and confirmed by Plus Point as axial ODSCC. This is a new degradation mechanism for DCPP Unit 2.

Prior to 2R13, no occurrences of stress corrosion cracking at free span dings had been observed at DCPP Units 1 and 2, based on Plus Point sampling of free span dings every outage starting in Unit 2 Seventh Refueling Outage (2R7) and Unit 1 Eighth 12

Enclosure 1 PG&E Letter DCL-06-129 Refueling Outage (1 R8). Axial ODSCC at free span dings has been reported in several original Westinghouse designed SGs.

Table 9 summarizes the inspection scopes for dings at DCPP Units 1 and 2 from 2R7/1 R8 through 1 R1 3/2R1 3. Plus Point sample inspections of greater than 2 volts dings were routinely performed prior to 2R1 1. Starting with 2R11/1 R12, the bobbin coil was credited for detection of cracking in less than or equal to 5 volts dings and Plus Point inspections were focused on greater than 5 volts dings. The Plus Point detection technique is in accordance with EPRI ETSS 21409.1. The bobbin coil detection technique is in accordance with EPRI ETSS 24013.1.

In 2R13, the initial eddy current scope was 20 percent Plus Point sample of greater than 5 volts dings in the U-bend and 20 percent in the straight legs. The straight leg sample was biased to the hot leg. After detection of the ding axial ODSCC in SG 2-1 R1C30 and SG 2-2 R23C51, the Plus Point scope was expanded to 100 percent of greater than 5 volts dings in these two SGs. No additional indications were detected.

In addition, 20 percent of greater than or equal to 2 volts dings that are coincident with AVB structures in the U-bend region were Plus Point inspected, to address industry experience of the potential masking effects of AVBs on bobbin coil flaw detection. In these exams, the Plus Point inspection extent consisted of the entire length of free span between the support structures. No degradation was detected in this exam.

Table 11 provides the 2R1 3 bobbin and Plus Point data for the ding ODSCC indications, including tube location, voltages, phase angles, length, and MD estimate.

The Plus Point phase angles are in the ID plane. As such, MDs reported by Plus Point are not reliable. Westinghouse reported that ID phase angles for ding ODSCC are consistent with the qualification data set for flaws less than 70 percent MD due to the resultant response created by the ding and the ODSCC indication. Therefore, the flaws are judged to be less than 70 percent MD.

The location of the axial ODSCC indications in R1iC30 and R23C51 are coincident with the locations of the dings, such that the resultant Plus Point voltages (0.34 volt and 0.79 volt, respectively) are conservatively high and reflect the combination of the ding voltage and the ODSCC voltage. The estimated Plus Point voltages for only the axial ODSCC indications are 0.10 and 0.25 volt, respectively. Based on these voltages, the estimated MDs are about 37 percent and 55 percent based on the mean depth/voltage correlation in Figure B-6 of EPRI Report 1007904 for axial ODSCC in Westinghouse SGs based on combined free span, ding, sludge pile, and TSP indications.

The Plus Point voltages of 0.34 and 0.79 volt for R1iC30 and R23C51 were less than the in-situ leak testing threshold value of 1.23 volts as provided in Section B.5.3.5 of EPRI Report 1007904, so in-situ leak testing was not required. Therefore, no SLB leakage is postulated at EOC 13. The judgment of shallow ODSCC depth is supported 13

Enclosure 1 PG&E Letter DCL-06-129 because the resultant ding ODSCC signals, which include the ding amplitude component, are much less than the in-situ leakage screening value.

The lengths of the axial ODSCC indications were 0.17 inch and 0.22 inch and are much less than the 100 percent TW structural limit of 0.43 inch at 3dPNO. As such, in-situ proof testing was not required. Accounting for NDE uncertainty is not required since the indication is assumed to be 100 percent TW and the length will be overestimated due to coil lead-in and lead-out affects.

In conclusion, leakage and structural integrity were satisfied at EOC 13 for axial ODSCC indications at free span dings.

PG&E evaluated the potential for circumferential ODSCC at free span dings based on industry experience in original Westinghouse designed SGs. PG&E determined that a total of four small circumferential indications at free span dings were reported in two plants. The indications were in-situ proof tested with no leakage identified. In all cases, the ding orientation was circumferential, and limited to dings that occur in pairs (termed paired dings). Paired dings result from the tube being rotated out of plane while engaged with a TSP during tube insertion, such that the paired dings would be located about 0.75 inch from each other and on opposite sides of the tubes.

PG&E has reviewed the industry data for applicability to DCPP Unit 2, and has concluded that there is a potential for paired dings at DCPP Unit 2. The axial separation distances of DCPP Unit 2 ding indications were reviewed and it was determined that 25 free spans had dings located about 0.75 inch apart (plus or minus 0.25 inch). Eleven of these 25 free spans had a prior Plus Point examination during at

'least one of the past four inspections, with no ODSCC detected. This is a sufficient sample to conclude that circumferential ODSCC in free span paired dings is not an active damage mechanism at DCPP Unit 2.

In addition to the examination of paired dings discussed above, PG&E has performed a sufficient Plus Point sample inspection of the total population of dings. As seen in Table 9, PG&E has performed several 100 percent Plus Point inspections of greater than 5 volts dings, and many 20 percent Plus Point sample inspections of less than 5 volts dings, and no circumferential indications have been detected. Table 10 provides the less than 5 volts ding population for DCPP Units 1 and 2, along with the number of Plus Point inspections conducted on less than 5 volts dings over the last four inspections on each unit (refueling outage 10 to refueling outage 13). Some of the less than 5 volts dings may have been inspected more than once in this study period. Most of the less than 5 volts ding inspections have occurred in the U-bends as a result of Plus Point inspections to detect circumferential PWSCC, with a smaller sample in the straight legs.

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Enclosure 1 PG&E Letter DCL-06-129 OperationalAssessment The 2R13 ding ODSCC indications were traceable by bobbin data to 2R12 and 2R1 1 data, based on phase angle rotations. This supports the industry experience of slow growth rates for this damage mechanism.

Assuming the longest ding axial ODSCC at Beginning of Cycle (BOC) 14 is 0.22 inch (the longest length detected in 2R13), and adding 95 percentile growth of 0.12 inch per EFPY (default growth rate for ODSCC per Section 5.5 of EPRI Report 1012987, SG Integrity Assessment Guidelines, Revision 2), the EOC 14 bounding length of 0.41 inch would be less than the 100 percent TW structural limit of 0.43 inch at 3dpNO. As such, structural integrity is satisfied at EOC 14 for axial ODSCC indications at free span dings.

Leakage integrity at postulated SLB conditions for axial ODSCC at dings is demonstrated by applying the Arithmetic Special Case approach in Section 8.5 of EPRI Report 1012987. This approach has been verified versus a series of fully probabilistic analyses that consider the entire degradation population, both detected and undetected in previous inspections. When the observed flaw population is small, the worst case BOC depth may be chosen as the MD value at a POD equal to 0.5 if all other input is selected at worst case 95 percentile values.

From a log-logistic fit to the detection data in ETSS 24013.1, the worst case BOC undetected MD is 62 percent TW. The 95 percentile MD growth is 16.4 percent per EFPY (ODSCC default AD growth rate of 13.1 percent per EFPY times 1.27 ratio for MD to AD, based on Section 5.5 of EPRI Report 1012987). The applied MD growth of 16.4 percent per EFPY is conservative compared to ding ODSCC growth rates developed for another plant with Model D4 SGs, when the observed 95 percentile depth growth is adjusted for operating temperature differences between DCPP Unit 2 SGs and the Model D4 SGs.

The resultant projected worst case EOC 14 depth for a 1.62 EFPY cycle length is 89 percent TW. As discussed earlier, the worst case projected length at EOC 14 using an upper 95 percentile growth rate is 0.414 inch. For a lower 95 percent probability at 95 percent confidence (95/95) tolerance limit flow strength, applying the axial crack pop through equation of Section 9.7 of EPRI Report 1012987 leads to a required depth for pop through of 91 percent TW at the bounding length of 0.414 inch. The projected worst case depth is less than that required to create a leakage path at a SLB pressure differential of 2405 pounds per square inch (psi). Therefore, no SLB leakage is projected at EOC 14.

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Enclosure 1 PG&E Letter DCL-06-129 4.4 Circumferential ODSCC at Top of Tubesheet Region (Active)

Condition Monitoring Circumferential ODSCC indications at the top of tubesheet are capable of being detected by Plus Point using EPRI ETSS 21410.1.

One circumferential ODSCC indication (SCI) in the hot leg top of tubesheet WEXTEX transition region was detected by Plus Point in 2R13. The Plus Point data are listed in Table 5, As noted in Table 5, the indication was too small to be depth profiled.

The location of the SCI was very close to the top of tubesheet elevation, within the WEXTEX expansion transition region, and in the center bundle region where the largest tube scale buildup existed prior to chemical cleaning in 2R12.

The 3dPNO structural limit for an SCI is 265 degrees, assuming a 100 percent TW defect, and 73.5 PDA. The 2R13 SCI measured length was 73 degrees, and adjusted to 190.6 degrees after applying large 95 percent NDE uncertainties. This length is less than the 265 degree structural limit under the very conservative assumption that the indication is uniformly TW. Therefore, structural integrity was satisfied at EOC 13.

The Plus Point voltage was 0.16 volt, much less than the 1.31 volts threshold for leak testing of circumferential ODSCC in transitions as documented in EPRI Report 1007904. Based on this small voltage, no SLB leakage should be postulated for this degradation at EOC 13. A MD measurement was not identified for this low voltage circumferential indication due to difficulties in sizing circumferential indications below about 0.5 volt.

OperationalAssessment The 2R1 3 WEXTEX transition circumferential indication was not detectable in the prior outage data based on a lookup analysis. There are 21 DCPP Units 1 and 2 growth rate data points for WEXTEX transition circumferential ODSCC using the WCAP-1 5573, Revision 1, sizing techniques. The as-found maximum voltages of this data set are all less than 0.5 volt, so depth sizing may not be reliable at these small voltages.

Nonetheless, the 95 percent growth rates per EFPY for this data set are 27.5 degrees, 35 percent MD, 23.5 percent AD, and 0.21 volt.

Assuming the same AD detection thresholds as for TSP circumferential ODSCC (35 percent for AD), the projected EOC 14 AD would be 73.1 percent, less than the 73.5 PDA structural limit. Alternatively, assuming the worst case length of an undetected circumferential indication is equal to the indication detected in 2R13 (73 degrees), the projected EOC 14 length would be 118 degrees, much less than the 265 degree structural limit.

16

Enclosure 1 PG&E Letter DCL-06-129 Because MD measurements in low voltage circumferential indications are not realistic due to difficulties in sizing circumferential indications below about 0.5 volt, maximum voltage is applied for determining leakage integrity at EOC 14 conditions. Assuming the worst case maximum voltage of an undetected circumferential indication is equal to the maximum voltage detected in 2R13 (0.16 volt), the projected EOC 14 voltage would be 0.5 volt, much less than the 1.31 volts threshold for leak testing of circumferential ODSCC in transitions as documented in EPRI Report 1007904.

Based on the 100 percent Plus Point inspection of the hot leg WEXTEX region, observations of small numbers of circumferential indications, very small growth rates, and large structural margin, there is a low probability that ODSCC circumferential indications located in the WEXTEX transition zone will challenge the 3dPNO structural integrity performance criteria through EOC 14. Likewise, based on the small maximum voltages associated with circumferential ODSCC indications located in the WEXTEX transition zone, along with very small voltage growth rates, there is a low probability that circumferential ODSCC indications would grow TW in a cycle, and no leakage should be postulated in a faulted SG following a SLB at EOC 14.

4.5 Axial PWSCC in Rows 1 and 2 U-Bends (Active)

Circumferential PWSCC in Row 1 U-Bends (Non-Active)

SG tubes in Rows 1 and 2 U-bends were heat treated following one cycle of operation for Unit 2 and two cycles of operation for Unit 1 to relieve stresses and mitigate the potential for PWSCC in this location. One hundred percent of Rows 1 and 2 U-bends have been inspected each refueling outage. Bobbin probes were used in the first refueling outage inspection. Since then, these inspections were conducted with a single coil rotating probe. Starting in 2R7 and 1R8, a Plus Point probe was used to inspect Rows 1 and 2 U-bends for detection of PWSCC.

PWSCC has been detected in the U-bend region of Row 1 tubes in all Unit 1 and Unit 2 SGs. The majority of Row 1 PWSCC has been axial, with a small number of circumferential. Axial PWSCC has also been detected in Row 2 in SG 1-4 (1R8) and SG 2-3 (2R8). Starting in 2R1 1 and 1 R1 2, 100 percent of Rows 1 to 10 have been Plus Point inspected. The 2R1 1 inspection included 100 percent inspection to Row 46. No axial PWSCC indications have been detected in greater than Row 2 in these inspections. Prior to 2R1 3, 2R1 1 was the last occurrence of Row 1 or 2 U-bend axial and circumferential PWSCC indications.

ETSS 96511.2 is the Plus Point technique that is applied for detection of PWSCC in low row U-bends.

Condition Monitoring In 2R13, 100 percent of Rows 1 and 2 U-bends were Plus Point inspected. Two axial PWSCC indications were detected in Row 1 tubes, and the tubes were plugged.

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Enclosure 1 PG&E Letter DCL-06-129 The axial indications were sized by Plus Point using line by line phase sizing techniques that are applied for axial PWSCC at dented TSP intersections (WCAP-1 5573, Revision 1). The MDs were adjusted in accordance with the depth adjustment rules in WCAP-1 5573, Revision 1, that is, the MD is taken as the depth at the maximum amplitude from the line by line sizing profile. The adjusted MDs are more representative of the true MD for small voltage indications. Table 7 provides the Plus Point sizing data (maximum volts, length, MD from phase angle analysis, and adjusted MD taken from the maximum amplitude). Lookup data for 2R12 is also provided. The NDE depths are not corrected for NDE uncertainty because the sizing technique is not validated for axial PWSCC in low row U-bends.

The maximum voltages of the axial PWSCC indications were 0.68 and 1.00 volt with lengths of 0.11 inch. The maximum voltages were less than the threshold voltage of 1.20 volts for in-situ leak testing documented in EPRI Report 1007904. As such, in-situ leak testing was not required. Subsequent to EPRI Report 1007904, in-situ testing of DCPP Unit 2 axial PWSCC in Row 1 U-bends of 1.23 volts and 1.15 volts in 2R1 1 (2003) did not result in leakage, further validating the conservative applied threshold of 1.20 volts.

The flaw lengths are less than the bounding 100 percent TW structural limit length of 0.64 inch for 3dPNO conditions for Rows 1 and 2. Accounting for NDE uncertainty is not required since the indication is assumed to be TW and the length will be overestimated due to coil lead-in and lead-out affects. As such, in-situ proof testing was also not required.

In conclusion, leakage and structural integrity were satisfied at EOC 13 for axial PWSCC indications in Row 1.

One Row 2 tube (SG 2-2 R2C80) was preventively plugged in 2R1 3 due to U-bend data quality concerns. The 0.620 inch Plus Point coil exhibited noisy data in the U-bend region. Preventive plugging due to noisy data in Rows 1 and 2 U-bends has also occurred in previous outages. CMOA is not required for preventive plugging.

OperationalAssessment This operational assessment covers both axial and circumferential PWSCC in Rows 1 and 2 U-bends, even though circumferential PWSCC was not detected in 2R13.

Both of the axial PWSCC indications were detectable in the 2R1 2 Plus Point data based on a lookup. The lookup data is provided in Table 7, along with growth rates.

The growth rates per EFPY were very small, bounded by 0.14 volt, 0.02 inch, and 4 percent MD. The small growth rates are consistent with prior observations of this slow growing damage mechanism.

18

Enclosure 1 PG&E Letter DCL-06-129 There are some additional Plus Point growth rates from prior DCPP Unit 1 and 2 inspections, but the resulting data set is very limited. There is a large database of growth rates for axial PWSCC at dented TSPs, as discussed in the PWSCC ARC 90 day report. For the conservative data set used in the PWSCC ARC Unit 2 Cycle 14 operational assessment, the 95 percentile growth rates per EFPY are bounded by about 0.12 inch for length, 12 percent for MD, and 11 percent per EFPY for AD. This large growth rate data set from axial PWSCC at dents is used for the operational assessment for axial and circumferential PWSCC in low row U-bends.

Assuming that an axial PWSCC indication with a 100 percent TW length of 0.11 inch is the largest undetected Row 1 or Row 2 flaw (0.11 inch based on the length of the longest Row 1 axial PWSCC indication detected in 2R13), and adding a growth rate of 0.12 inch per EFPY, the resulting EOC 14 indication would be about 0.3 inch. This flaw length is less than the bounding 100 percent TW structural limit length of 0.64 inch for 3dPNO conditions in Rows 1 and 2, thereby demonstrating that structural integrity would be satisfied at EOC 14. As noted earlier, accounting for NDE uncertainty is not required due to the NDE length overestimations by Plus Point.

Assuming that a circumferential PWSCC indication with a 100 percent TW length of 15.7 degrees is the largest undetected Row 1 or Row 2 flaw and was left in service (15.7 degrees based on the length of the most recent Row 1 circumferential PWSCC indication detected in 2R1 1), and adding a growth rate of 13 degrees per EFPY, the resulting EOC 14 indication would be about 37 degrees. This flaw length is much less than the Rows 1 and 2 100 percent TW structural limit length of 265 degrees, thereby assuring structural integrity is satisfied at.EOC 14. The large margin between the projected EOC flaw length and the structural limit allows for large NDE uncertainties.

A MD detection threshold of 45 percent is assumed to be applicable for axial and circumferential PWSCC in Rows 1 and 2 U-bends, based on the 45 percent MD detection threshold applied for TSP circumferential ODSCC. Adding 12 percent per EFPY MD growth results in an EOC MD of about 64 percent for axial and circumferential PWSCC in Rows 1 and 2 U-bends. Therefore, no leakage should be postulated in a faulted SG following a SLB at EOC 14.

In conclusion, no axial or circumferential PWSCC indications in Row 1 and 2 U-bends are expected that would challenge structural integrity performance criteria through EOC 14. In addition, no leakage should be postulated in a faulted SG following a SLB at EOC 14 due to the extremely low probability that indications would tear ligaments and pop through in one cycle.

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Enclosure 1 PG&E Letter DCL-06-129 4.6 Circumferential PWSCC in Rows 3 to 10 U-Bend Flank Locations (Active)

Background

In 2R1 1, a secondary side pressure test in SG 2-4 identified leakage in the R5C62 U-bend region. Subsequent Plus Point inspection detected several short circumferential crack-like indications on the ID of the Row 5 U-bend, extending from the hot leg tangent point to the cold leg tangent point. Because industry had never performed extensive high row U-bend inspections with a rotating probe, and this was a first of a kind degradation mechanism in both domestic and foreign plants, a critical area could not be immediately determined to limit the Plus Point inspection scope. As a result, the U-bend Plus Point inspection program was expanded to include 100 percent of the U-bend regions of all rows (Rows 3 through 46) in each SG. A total of 12 tubes were identified to have similar circumferential indications, ranging from Row 3 to Row

10. Each SG had at least one indication. The indications were located on the flanks of the tube. Video probe inspections confirmed the presence of circumferential ID cracking. The tubes were in-situ leak and proof tested, and only R5C62 exhibited leakage at SLB differential pressure (about 0.003 gpm at room temp). There were no tube bursts at 3dPNO.

The root cause of the indications was attributable to circumferential PWSCC due to high residual stresses inherent to the tube bending process, as documented in a formal root cause report issued by PG&E.

Following the 2R1 1 experience, the Westinghouse Owner's Group (WOG) issued a report on September 15, 2003, which defined a critical area for this damage mechanism and provided inspection and expansion recommendations for similar Model 51 SGs.

The WOG report demonstrates that U-bend circumferential flaw development is related to longitudinal residual stress, which is dependent on row (bend radius). Based on finite element analysis, longitudinal stress is reduced by a factor of 4 from Row 5 to Row 10, and a factor of 2 from Row 10 to Row 15. Figure 10 of the WOG report plots longitudinal strain as a function of row, and shows similar results (e.g., longitudinal strain, and hence stress, is reduced by a factor of about 2 from Rows 9 and 10 to Row 16). Figure 10 of the WOG report is used to define the expansion plans because it provides more conservative results than the WOG finite element analysis.

All Westinghouse SGs with Alloy 600 mill annealed tubing have completed the initial and subsequent U-bend inspections per the WOG inspection guidelines. For plants that had circumferential indications detected in the first inspection, the number of indications in their second inspection was dramatically reduced, illustrating the Plus Point inspection transient associated with this damage mechanism.

For DCPP Unit 2, the first time inspections in 2R1 1 identified 12 tubes with circumferential PWSCC, and the second time inspections in 2R12 identified 2 tubes with circumferential PWSCC. Most of the indications were in Rows 5 and 6.

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Enclosure 1 PG&E Letter DCL-06-129 For DCPP Unit 1, the first time inspections in 1R1 2 identified 85 tubes with circumferential PWSCC indications, with Row 8 being the highest row affected and most of the indications occurred in Rows 5 and 6. No PWSCC indications were detected in the 1 R1 3 U-bend inspections, validating that the previous outage Plus Point inspection results were a transient associated with this damage mechanism. In 1R12, a total of 9 tubes with U-bend circumferential PWSCC indications had Plus Point voltages in excess of 1.73 volts, and were in-situ pressure tested. Four of the tubes leaked slightly at pressures in excess of 3750 psi, well above SLB pressure of 2405 psi. At 3dPNO, no burst occurred and very small leak rates were measured. Based on these 1R12 results, no SLB accident-induced leakage was attributed to U-bend circumferential PWSCC, and structural margins were maintained. It was believed that the SG 1-4 prior cycle operational leakage of 1 gpd may have been due to leakage from one or all of these 4 tubes even though no leakage was identified in the in-situ tests at normal operating pressure and SLB differential pressures.

For PWSCC data limited to DCPP SGs, Unit 1 is limited to Row 8 and Unit 2 is limited to Row 10. For Model 51 SG data not including DCPP, PWSCC is limited to Row 9, consistent with DCPP experience. The peak voltages of the DCPP indications also decrease with increasing row. The combination of smaller numbers and smaller voltages with increasing row validates the information on Figure 10 of the WOG report which shows decreasing strain with increasing row.

Condition Monitoring The 2R1 3 inspection plan consisted of inspection of 100 percent of the Row 3 to Row 10 U-bend region by 0.680 inch diameter mid range Plus Point in each SG, applying ETSS 96511.2 techniques.

As shown in Table 8, in 2R13, 5 small circumferential PWSCC indications were detected in three tubes in Row 7 and Row 8. The indications were located in the ridge of probe liftoff signals, similar to prior Unit 2 indications, which were shown to be oriented on the flanks of the tubing based on Unit 2 video inspections.

An expansion plan was also documented in the Degradation Assessment, as summarized in Table 1, but implementation was not required because the indications were confined to Row 8 and lower.

The circumferential indications were sized by Plus Point using line by line phase sizing techniques that are applied for circumferential indications at dented TSP intersections (Appendix B of WCAP-1 5573, Revision 1). The MDs were taken as the depth at the maximum amplitude from the line by line sizing profile. The adjusted MDs are more representative of the true MD for small voltage indications. Table 8 provides the Plus Point sizing data (maximum volts, length, MD from phase angle analysis, and adjusted MD taken from the maximum amplitude). Lookup data for 2R12 is also provided. The 21

Enclosure 1 PG&E.Letter DCL-06-129 NDE depths are not corrected for NDE uncertainty because the sizing technique is not validated for circumferential PWSCC in U-bends.

The most significant (largest voltage) indications were in SG 2-4 R8C25, which had 3 separate indications.

All indications were screened for potential in-situ testing in accordance with the guidance in EPRI Report 1007904, Steam Generator In-Situ Pressure Test Guidelines, Revision 2, August 2003. The pre-established voltage screening threshold leakage value for U-bend circumferential PWSCC was 2.01 volts Plus Point, based on the data in Table B-16 of the EPRI guidelines as supplemented by industry U-bend in-situ test data compiled in 2003 through 2005 (including the DCPP Unit 2 SG 2-4 R5C62 U-bend leaker discovered in 2003). The largest Plus Point voltage was 0.79 volt for R8C25, well below the 2.01 volts threshold for leak testing, and therefore no in-situ leak testing was required.

The 3dPNO structural limit for 100 percent TW circumferential cracking in Rows 1 to 10 U-bends is 265 degrees, not accounting for NDE uncertainty. The longest reported length was 18.5 degrees in R8C25, much less than the 100 percent TW structural limit length of 265 degrees. This difference allows for significant margin for NDE uncertainty. As such, no in-situ proof testing was required.

OperationalAssessment All of the circumferential PWSCC indications were detectable in the 2R12 Plus Point data based on a lookup. The lookup data is provided in Table 8, along with growth rates. The growth rates per EFPY were very small, bounded by 0.21 volt, 2.1 degrees, and 11 percent MD. 2R1 1 data was also reviewed, and only R8C25 indication number 3 was detectable. This was the largest voltage indication detected in 2R1 3.

The small growth rates are consistent with prior observations of this slow growing damage mechanism. Also, analytical and test information indicates that cracks should remain short, i.e., once away from the flanks of the tube, the residual stresses become compressive and crack growth in the hoop direction would be expected to stop.

One additional Plus Point growth rate data point is available from the prior 2R1 2 inspection. Therefore, there are 6 growth rate data points at DCPP Units 1 and 2, which is a very limited data set. There is a large database of growth rates for axial PWSCC at dented TSPs, as discussed in the PWSCC ARC 90 day report. For the conservative data set used in the PWSCC ARC Unit 2 Cycle 14 operational assessment, the 95 percentile growth rates per EFPY are bounded by about 0.12 inch for length, 12 percent for MD, and 11 percent per EFPY for AD. There is a smaller growth rate database for circumferential PWSCC at dented TSPs. As discussed earlier in this enclosure, the 95 percentile growth rates per EFPY for circumferential PWSCC at dented TSPs are about 13 degrees, 17 percent MD, and 10 percent AD. The larger 22

Enclosure 1 PG&E Letter DCL-06-129 growth rate data set from axial PWSCC at dents is used for the operational assessment for circumferential PWSCC on the flanks of U-bends.

The assumed detection threshold for circumferential PWSCC in Rows 3 and higher is about 18.5 degrees (the longest length of the 2R13 indications). Adding 16 degrees per EFPY growth over Cycle 14 to the detection threshold results in a projected EOC 14 length of about 45 degrees. This length is much less than the 265 degree structural limit, thus allowing large margins for NDE length measurement uncertainty. In addition, the axial stress field in the flanks of the U-bends is very limited in circumferential extent, which is consistent with the short flaw lengths found for previously uninspected tubes.

Consequently, the potential circumferential extent is much less than the structural limit.

Therefore, structural margins would be maintained at EOC 14.

The possibility of circumferential PWSCC in Rows 11 and higher U-bends at EOC 14 is unlikely, given the 100 percent Plus Point inspection performed in 2R1 1 with no detected indications in Rows 11 and higher, the decreasing residual stresses in higher rows, and the 2R12 and 2R13 Plus Point NDD condition in Rows 9 and 10.

Because Plus Point inspections were performed in 100 percent of Rows 1 to 10 U-bends, it is reasonable to assume that all 100 percent TW U-bend indications were detected and plugged. The Plus Point MD detection threshold for Rows 1 and 2 PWSCC is about 45 percent as discussed earlier, and is applied for circumferential PWSCC in U-bend flank locations. Adding 19 percent growth over Cycle 14 to the detection threshold results in a projected EOC 14 MD of about 64 percent. Therefore, leakage integrity would be maintained for Cycle 14. This conclusion is further supported by the fact that, based on in-situ pressure testing of many U-bend circumferential PWSCC indications in Rows 3 to 8 conducted in 2R1 1 (12 tubes tested, maximum Plus Point voltage of 3.04 volts) and 1R1 2 (9 tubes tested, maximum Plus Point voltage of 3.52 volts), only one indication (SG 24 R5C62) had measurable leakage (0.004 gpm) at SLB pressure differentials.

In conclusion, no circumferential PWSCC indications in U-bends are expected that would challenge structural integrity performance criteria through EOC 14. In addition, no leakage should be postulated in a faulted SG following a SLB at EOC 14 due to the extremely low probability that indications would tear ligaments and pop through in one cycle. This conclusion is validated based on the results of 2R1 1 in-situ pressure testing of the worst case TW indication, which demonstrated structural integrity at 3dPNO conditions and significant SLB leakage margin compared to the performance criteria limit.

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Enclosure 1 PG&E Letter DCL-06-129 4.7 Cold Leg Thinning (Active)

Condition Monitoring Cold Leg Thinning (CLT) indications at cold leg TSP intersections are detected by bobbin probes, applying EPRI ETSS 96001.1, as part of the 100 percent full-length bobbin inspection. In outage inspections prior to 1R12 and 2R12, CLT indications were sized by bobbin (phase based depth sizing) also using EPRI ETSS 96001.1, and CLT indications were plugged if bobbin indicated a depth greater than or equal to 40 percent TW.

PG&E and Westinghouse had determined that field indications sized by phase angle analysis were found to have deep indicated depths for low voltage indications, resulting in unnecessary tube plugging of low voltage CLT indications. Therefore, a project was undertaken to develop improved bobbin coil sizing techniques to support tube repair decisions, and to develop burst correlations to support tube integrity analyses for CLT indications in Westinghouse Model 51 SGs. The initial work was documented in Westinghouse Report SG-SGDA-02-41, "Cold Leg Thinning Database for Tube Integrity Assessments and NDE Depth Sizing," October 31, 2002. In addition, to support implementation of the improved sizing techniques, a performance demonstration was conducted in 2004 to incorporate analyst uncertainty into the correlations, and the results were documented in Westinghouse report SG-SGDA-04-17, "Diablo Canyon Performance Test Based NDE Sizing Uncertainties for Cold Leg Thinning Indications,"

April 15, 2004. The performance tests were conducted by 14 NDE analyst teams based upon blind analyses of 201 cold leg thinning samples that included noise additions that applied DCPP noise data to the laboratory simulations of cold leg thinning indications.

Report SG-SGDA-04-17 concluded that amplitude sizing of CLT indications is appropriate to establish the percent TW, with 4.5 volts as the upper limit for amplitude sizing. Above 4.5 volts, phase sizing is used to establish the percent TW. The 4.5 volts cutoff superseded the preliminary recommended cutoff of 1.9 volts provided in report SG-SGDA-02-41 based on the conclusion that amplitude sizing is more reliable than phase sizing below 4.5 volts for indications with high noise levels.

In 2R13 (as in 2R12), this new CLT sizing technique was used, in conjunction with the previously established repair limit of 40 percent TW. In 2R13, only new bobbin TSP indications in the cold leg thinning zone were inspected by Plus Point. This contrasts with 2R12 inspections, in which 100 percent of bobbin indications at cold leg TSPs that had never been Plus Point inspected were inspected by Plus Point to re-establish and validate the cold leg thinning region. 2R12 bobbin TSP indications located in the periphery of the bundle at lower TSP elevations were verified to be volumetric indications by Plus Point, indicative of cold leg thinning. All other 2R12 bobbin TSP cold leg indications were NDD by Plus Point.

24

Enclosure 1 PG&E Letter DCL-06-129 In 2R13, 173 CLT indications were detected and sized by bobbin, of which two were greater than or equal to 40 percent and were plugged. All indications were limited from 1C and 4C TSPs. No indications exceeded the 4.5 volts cutoff, so all indications were sized by amplitude analysis.

The deepest indication identified in 2R1 3 was 46 percent TW. Applying the regression equation from SG-SGDA-04-17 to correct the NDE measurement to the actual depth for 95 percent NDE uncertainty based on the analyst performance test {%TWActual =

(%TWMeasured*1 .09 + 7.51) + (1.64* standard deviation of 5.73)}, results in a CLT flaw of 67 percent. Applying the lower 95 percent CLT burst correlation from Figure 8-7 of SG-SGDA-02-41 (correlation of burst pressure with actual MD, where actual depth conservatively obtained from the NDE sizing correlation with application of the 95 percent uncertainty on the NDE measurement) yields a CLT burst pressure of 7293 psi, much greater than the 3367 psi burst pressure margin requirement for 1.4dPSLB, where SLB differential pressure is 2405 psi. Therefore, the structural integrity performance criteria were satisfied for this bounding indication at EOC 13. Applying the lower 95 percent CLT ligament tearing correlation from Figure 8-16 of SG-SGDA-02-41 (correlation of ligament tearing pressure with actual MD, where actual depth conservatively obtained from the NDE sizing correlation with application of the 95 percent uncertainty on the NDE measurement) yields a CLT ligament tearing pressure of 6261 psi, much greater than the 2405 psi SLB differential pressure and 3367 psi burst pressure margin requirement. Therefore, no SLB leakage is postulated for this bounding indication at EOC 13.

OperationalAssessment Nineteen new CLT indications were detected in 2R1 3. All but one were detectable in the prior outage lookup data and were added to the growth distribution. NDE uncertainties were applied to estimate the mean actual depth for both the 2R12 and 2R1 3 indications prior to calculating the growth rates for the cycle, using the mean regression equation. One hundred seventy two indications are in the Cycle 13 growth distribution, and the 95 percent growth rate per EFPY is 4.17 percent.

The largest beginning of cycle flaw left in service (39 percent), corrected for 95 percent NDE uncertainty, plus 4.17 percent/EFPY growth rate, results in a projected EOC 14 flaw size of 66 percent TW. Applying the lower 95 percent CLT burst correlation yields a CLT burst pressure of 7346 psi, much greater than the 3367 psi burst pressure margin requirement. Therefore, the structural integrity performance criteria were satisfied for this bounding indication at EOC 14. Applying the lower 95 percent CLT ligament tearing correlation yields a CLT ligament tearing pressure of 6380 psi, much greater than the 2405 psi SLB differential pressure and 3367 psi burst pressure margin requirement. Therefore, no SLB leakage is postulated for this bounding indication at EOC 14.

25

Enclosure 1 PG&E Letter DCL-06-129 4.8 Antivibration Bar Wear (Active)

Condition Monitoring AVB wear indications are detected by bobbin probes during the 100 percent full-length bobbin inspection. AVB wear indications are sized by bobbin using EPRI ETSS 96004.1. AVB wear indications are plugged if bobbin indicates a depth greater than or equal to 40 percent TW. The 3dPNO structural limit for the worst case tube with AVB wear is 71 percent for Row 16 and higher, and 65 percent for Row 15 and lower. All AVB wear in 2R13 is in greater than Row 15 tubes, so 71 percent is the applicable structural limit. The AVB wear repair limit of 40 percent allows for NDE uncertainty and flaw growth progression.

In 2R13, the bobbin coil inspection identified 302 AVB wear indications, of which one was greater than or equal to 40 percent and plugged. The deepest indication identified in 2R13 was 40 percent.

In accordance with EPRI ETSS 96004.1, sizing of AVB wear with bobbin coil has an NDE regression correlation (0.97* percent TW+ 3.49 percent) with a standard error of 4.49 percent. Additionally, the standard error for analyst uncertainty is conservatively assumed as 7.04 percent (reference "Appendix G Generic NDE Information from CM/OA," extracted from "Capabilities of Eddy Current Analysts to Detect and Characterize Defects in SG Tubes," Doug Harris, presented at November 1996 EPRI NDE workshop.) These uncertainties (technique and analyst) were combined (8.17 percent NDE uncertainty using the method in "The Use and Misuse of ETSS and Analyst Uncertainty", Bob Keating, presented at February 2003 EPRI SG Integrity Workshop) and applied at 95/50 confidence to the limiting flaw detected at 2R13 (40 percent), resulting in a 56 percent AVB wear flaw, which is less than the AVB wear structural limit of 71 percent. Therefore, the structural integrity performance criteria were satisfied for this bounding indication at EOC 13. Because AVB wear was too shallow to consider ligament tearing (pop through), no leakage is postulated in a faulted SG following a SLB at EOC 13.

OperationalAssessment Eighteen new AVB wear indications were detected in 2R1 3, and all but one were detectable in the prior outage lookup data and were added to the growth distribution.

As a result, 301 indications are in the Cycle 13 growth distribution, and the 95 percent growth rate per EFPY is 5.3 percent.

Application of growth to the largest AVB wear indication left in-service results in a projected EOC 14 flaw size of 63 percent TW. This value is less than the AVB wear structural limit of 71 percent.

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Enclosure 1 PG&E Letter DCL-06-129 In conclusion, no AVB wear indications are expected to challenge structural integrity performance criteria through EOC 14. In addition, no leakage should be postulated in a faulted SG following a SLB at EOC 14 due to the extremely low probability that AVB wear indications would tear ligaments and pop through in one cycle.

4.9 Tube Support Plate (TSP) Ligament Thinning/Cracking (Active)

Starting in 1R8 and 2R8, PG&E implemented an inspection program to detect degradation of SGs at TSPs. A summary of this program was reported to the NRC in response to GL 97-06 (PG&E Letter DCL-98-046 dated March 27, 1998). Visual inspections performed in 1 R8 confirmed several missing TSP ligaments. Westinghouse has concluded that the missing TSP ligaments are related to TSP drilled hole manufacturing anomalies. The TSP manufacturing practices employed at the time that the DCPP steam generators were produced used a stacked drilling procedure. Several TSPs were clamped together and drilled simultaneously. A review of the eddy current suspect ligament crack (SLC) locations indicates distinct location patterns, indicative of manufacturing anomalies of the automatic drilling equipment.

Condition Monitoring The 2R13 eddy current inspection program consisted of several steps: 100 percent bobbin inspection to detect SLC at TSPs; Plus Point inspection of preexisting Plus Point confirmed indications (referred to as baseline indications); and Plus Point inspection of newly detected bobbin SLC indications. Plus Point indications are characterized as either single indication ligament cracks (LIC), or indications exhibiting a missing TSP ligament, referred to as ligament gaps (LIG). LIG indications are further assessed using Plus Point probe data to determine the gap extent.

Only missing TSP ligaments are a threat to tube integrity, as a gap could permit a tube burst under normal operating conditions, assuming tube cracking coincident with the location of the gap.

Axial PWSCC indications or axial ODSCC indications that have a LIC or LIG indication at the same TSP are required to be plugged due to PWSCC ARC and ODSCC ARC exclusion criteria.

In 2R13, Plus Point confirmed all of the 100 baseline ligament indications. In addition, Plus Point confirmed 61 new indications (11 LIG and 50 LIC indications). Thus, a total of 161 indications were detected, 132 LIC and 29 LIG. Sixteen of the indications were at the same TSP. Thus, a total of 145 TSPs were identified to have indications.

The largest measured LIG gap was 83 degrees. This largest gap bounds the combined gap for TSPs with two LIG indications, assuming that the gaps were connected. This bounding gap is less than the 146 degree threshold gap for preventive tube repair. As such, no tube plugging was required as a consequence of TSP ligament indications 27

Enclosure 1 PG&E Letter DCL-06-129 with large gaps. However, two LIC indications were plugged due to axial ODSCC indications at the same TSP. One new TSP axial ODSCC indication (less than 2 volts ARC repair limit) was plugged due to a new LIC indication at the same TSP. One repeat TSP axial ODSCC indication with a new LIC indication at the same TSP was plugged, although the ODSCC indication was already required to be plugged because the bobbin voltage exceeded the 2 volts ARC repair limit.

OperationalAssessment The preservice inspection data and 2R12 data were reviewed for the 61 new indications. Fifty five new indications were traceable to 2R1 2 bobbin or Plus Point data, demonstrating negligible change over Cycle 13. Only four new indications were traceable to preservice inspection bobbin data.

For the 18 repeat LIG indications, the largest gap was 33 degrees. Repeat gaps were compared to the prior outage gap measurements, showing negligible change. For the 11 new LIG indications, the largest gaps were 83 degrees and 59 degrees. All other new gaps were less than 28 degrees. These new LIG indications were traceable to 2R12 bobbin data based on a lookup. In addition, the LIG indication with a gap of 59 degrees had a prior 2R12 Plus Point inspection, which showed a gap of 49 degrees based on a lookup, indicating negligible change. None of the other new gaps had prior Plus Point inspection data, so a quantitative gap change assessment cannot be made.

The slow progression of ligament gaps indicates an insignificant change in the material condition of the TSPs. It is expected that the gap sizes of repeat and new LIG indications will not extend beyond the. 146 degree threshold gap for tube repair at EOC 14.

5.0 Degradation-Specific OA for Non-Active Potential Damage Mechanisms 5.1 Circumferential PWSCC in Row 1 U-Bends (Non-Active)

OA is discussed in Section 4 in conjunction with axial PWSCC in Rows 1 and 2 U-bends.

5.2 Circumferential PWSCC in WEXTEX Tubesheet Region (Non-Active)

No circumferential PWSCC was detected in the hot leg WEXTEX transition region by Plus Point in 2R13, based on 100 percent Plus Point inspection of the hot leg top of tubesheet region. The most recent Unit 2 circumferential PWSCC was detected in 2R10, so this damage mechanism is non-active for Unit 2. An OA is conservatively performed for this degradation mechanism.

Circumferential PWSCC indications in the tubesheet region are capable of being detected by Plus Point using EPRI ETSS 20510.1.

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Enclosure 1 PG&E Letter DCL-06-129 OperationalAssessment There is very limited DCPP Units 1 and 2 growth data for WEXTEX transition circumferential PWSCC using the WCAP-1 5573, Revision 1, sizing techniques. In addition, growth rates for DCPP top of tubesheet circumferential indications may not be reliable due to the small voltages of the indications. Because of this limited growth data, the growth rates per EFPY for circumferential PWSCC in the WEXTEX transition region are conservatively assumed to be the same as the 95 percent growth rates for TSP circumferential PWSCC (16.6 percent MD, 10.3 percent AD, 12.7 degree length).

Conservatively assuming a detection threshold of 35 percent for MD and 25 percent for AD (based on TSP circumferential PWSCC degradation), the projected EOC 14 AD and MD would be 42 percent and 62 percent, respectively. Circumferential indications of this size present no challenge to structural and leakage integrity. The 3dPNO structural limit for an SCI is 265 degrees, assuming a 100 percent TW defect.

Based on the 100 percent Plus Point inspection of the hot leg WEXTEX region, no detected PWSCC circumferential indications, very small growth rates, and large structural margin, there is a low probability that PWSCC circumferential indications located in the WEXTEX transition zone will challenge the 3dPNO structural integrity performance criteria through EOC 14. Also, there is a low probability that circumferential PWSCC indications in the WEXTEX transition zone would grow TW in a cycle, and no leakage should be postulated in a faulted SG following a SLB at EOC 14.

5.3 Axial ODSCC at Top of Tubesheet Region (Non-Active)

Axial ODSCC at the TTS is typically related to sludge pile accumulation at the TTS, and was identified as a potential degradation mechanism in the 2R13 degradation assessment because of the industry incidence of this damage in similarly designed SGs, including DCPP Unit 1 in 1R1 3. A large sludge pile height does not exist at DCPP Units 1 and 2, due to periodic sludge lancing cleanings. Chemical cleaning was performed in 1R1 2 and 2R1 2 to further reduce accumulated sludge at the TTS.

The Plus Point coil can reliably detect axial ODSCC at the TTS per ETSS 21409.1. In addition, the bobbin coil is capable of detecting axial ODSCC at the TTS per ETSS 96008.1.

Unit 2 axial ODSCC has never been detected in the hot leg WEXTEX transition region by Plus Point, based on 100 percent Plus Point inspections of the hot leg top of tubesheet region. Axial ODSCC at the TTS was detected in Unit 1 (twelve indications) in 1 R1 3, for the first time. The 1R1 3 indications were located near the TTS region, either within or slightly above the WEXTEX transition. The 1R1 3 affected tubes were located in the center of the tube bundle where most of the sludge accumulates. The largest peak Plus Point voltage was 0.23 volt and the longest length was 0.37 inch (shorter than the 3dPNO structural limit of 0.43 inch for 100 percent TW indications).

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Enclosure 1 PG&E Letter DCL-06-129 Even though no indications were detected in 2R1 3, a simplified OA is conservatively performed for this degradation mechanism.

OperationalAssessment Only four growth rate data points are available based on Unit 1 (1 R1 3) data. The largest growth rates are 0.1 volt per EFPY, 11.9 percent MD per EFPY, and 0.11 inch per EFPY, indicating small growth.

Assuming the largest indication left in-service in Unit 2 is bounded by the voltage of the largest indication detected in 1R1 3 (0.23 volt), and adding the largest voltage growth rate of 0.1 volt per EFPY, results in a bounding EOC 14 indication of 0.39 volt. This voltage is less than the 0.5 volt lower bound threshold for indications that will not leak at SLB conditions or burst at 3dPNO margins.

5.4 ODSCC Mixed Mode Indications at Dented TSP Intersections (Non-active)

If a dented TSP intersection contains an axial ODSCC indication and a circumferential indication (either ODSCC or PWSCC), this degradation is termed ODSCC mixed mode indication. Since axial ODSCC indications detected by bobbin at dented locations must be inspected with Plus Point, 100 percent of the susceptible population of ODSCC mixed mode indications would be detected at each inspection. No ODSCC mixed mode indications have been detected to date in Unit 2. However, two indications were detected in 1R12 (which were determined to be non-interacting), and one indication was detected in I R11.

An OA is performed for ODSCC mixed mode indications because this degradation mechanism has increasing potential for occurrence due to the increasing population of TSP axial ODSCC indications returned to service every inspection under ODSCC ARC.

OperationalAssessment In Unit 2 Cycle 14, there is a low likelihood of interacting ODSCC mixed mode indications developing that could affect leakage or burst margins of the axial ODSCC flaw, based on the following assessment. Potential TSP circumferential cracking should mainly occur in greater than 2 volts dents. There have only been two circumferential indications observed at a dent less than 2 volts (one in 1R1 2 and one in 1 R13). Nonetheless, potential circumferential indications at all dent sizes are considered. There were 223 intersections returned to service following 2R13 that contained Plus Point confirmed axial ODSCC at dented intersections. Two hundred seven of these intersections contained dents less than or equal to 2.0 volts and 16 of these intersections contained dents greater than 2.0 volts. All of these intersections were inspected by Plus Point to verify that no axial PWSCC or circumferential indications were detectable. Of these ODSCC indications at dented TSPs that were 30

Enclosure 1 PG&E Letter DCL-06-129 returned to service, the largest bobbin amplitude was 1.93 volts with a maximum Plus Point amplitude of 1.38 volts. The largest Plus Point amplitude from ODSCC indications returned to service at dented TSPs was 1.55 volts with a corresponding bobbin amplitude of 1.49 volts.

The upper 95 percent growth rate per EFPY for axial ODSCC in Cycle 13 is bounded by about 0.3 volt/EFPY. Adding this growth rate to the largest bobbin indication left in service at a dented TSP (1.49 volts) results in an EOC 14 flaw of about 1.98 volts.

Assuming the largest projected EOC 14 TSP circumferential indication (52 percent AD) interacts with a projected EOC 14 axial ODSCC indication of 1.98 volts:

" The axial ODSCC indication burst margin would not be affected because the 52 percent circumferential AD is less than the 75 percent AD threshold for mixed mode burst affects developed in WCAP-1 5573, Revision 1. In addition, a 1.98 bobbin volts ODSCC indication has a large margin against burst compared to the approximate 9 volts structural limit.

• The axial ODSCC indication SLB leak rate margin would not be affected because a 1.98 bobbin volts ODSCC indication has a very small probability of leaking as a free span indication, per the ODSCC ARC correlations. In addition, the largest ODSCC Plus Point amplitude of 1.55 volts found at a dented TSP returned to service would be expected to remain below the 2.75 volts typical of a TW indication for axial ODSCC.

5.5 Secondary Side Integrity and Potential Tube Damage from Loose Parts and Foreign Objects (Non-active)

In 2R13, there were no SG secondary side maintenance activities. No sludge lancing was performed, no foreign object search and retrieval (FOSAR) inspections were performed, no SG upper internals inspections or repairs were conducted, and the lower (handholes) and upper secondary side manways were not removed.

EPRI letter SGMP-IG-05-04 dated November 18, 2005 transmitted a new Chapter 10 of the Integrity Assessment Guidelines (IAGL), providing guidance on SG secondary side maintenance, including cleaning and visual inspection activities. PG&E followed the EPRI guidance in developing justifications for not performing secondary side maintenance activities in 2R13.

A detailed technical justification for not performing sludge lancing was prepared well in advance of 2R13, approved by DCPP management, and was documented in the Degradation Assessment. Chemical cleaning was performed in 1R12 and 2R12, in which about 19,000 pounds (Unit 1) and 29,000 pounds (Unit 2) of sludge and scale were removed. The small amount (total 56 pounds) of sludge removed in 1R1 3 (first outage after chemical cleaning), together with the small numbers of TTS ODSCC 31

Enclosure 1 PG&E Letter DCL-06-129 detected to date, provided sufficient technical basis for not performing sludge lancing activities in 2R13, which is the final outage before SG replacement.

A detailed technical justification for not performing FOSAR inspections was also prepared well in advance of 2R1 3, along with a FOSAR contingency plan that was dependent on the results of the eddy current inspections. The justification addressed the specific EPRI guideline recommendations listed below. The justification was approved by DCPP management and was documented in the Degradation Assessment. The small numbers and declining trend of foreign objects detected in the SGs, combined with the observation that no tube wear attributable to foreign objects has ever been detected by eddy current testing in the DCPP Unit 1 and 2 SGs, provided sufficient basis for deletion of FOSAR activities in 2R1 3.

The EPRI guideline requires that FOSAR inspections be performed following each sludge lancing, or any other time that the secondary side handholes are opened for maintenance access. If sludge lancing is not being performed and the secondary side hand holes are not scheduled to be opened, then the decision to perform a scheduled FOSAR during a refueling outage is to be based on a documented evaluation that considers the maximum interval between secondary side visual inspections, and also consider operating experience from all pressurized water reactors. If FOSAR is not scheduled to be performed during a refueling outage based on a documented evaluation, a plan to perform a contingency FOSAR in the affected SG(s) during the refueling outage is to be developed. The contingency plan is to consider the results of the primary side eddy current inspections, subsequent potential engineering evaluation of possible loose part (PLP) indications, and known foreign objects that could have entered the SGs (e.g., from the feed train).

The EPRI guideline provides the following specific elements (including historical loose parts, wear indications, similar plant inspection results, maintenance activities, and the planned eddy current inspection intervals) that need to be addressed when documenting the maximum interval between secondary side visual inspections. PG&E's detailed evaluation considered the following elements identified in the guideline, as discussed below.

Location and description of historicalloose parts.

A loose parts log was created to describe, track and trend loose parts retrieved (or not retrieved) from the DCPP SGs. In general, most of the loose parts are associated with DCPP SG upper internals maintenance activities that were initiated in the Units 1 and 2 Fifth Refueling Outages (1 R5/2R5). The trend for loose parts has declined over the years, coincident with the decline of SG upper internals maintenance activities, which were finally completed in 2R1 1/1R12. The 2004 Self Assessment 32

Enclosure 1 PG&E Letter DCL-06-129 of DCPP foreign material exclusion (FME) practices showed that the FME program is in good health and is continuing to improve.

Unit 2 had only two PLP indications in the last two inspections (none in 2R1 1, two in 2R1 2). The PLP indications in 2R1 2 were not detected during 2R12 FOSAR inspections. These indications were believed to be conductive sludge piles on the tube that could have been removed during the subsequent chemical cleaning. The 2R12 eddy current inspections at these locations were performed before chemical cleaning, and the FOSAR inspection was done after chemical cleaning.

Description of those foreign objects with associated wear indications.

This element is not applicable to DCPP Unit 1 and 2, as no loose part wear indications have been detected over the life of the plant.

Failureof control and monitoringof foreign objects and loose parts.

Based on the larger number of loose parts associated with DCPP SG upper internals maintenance activities, it appears that there was a failure of control and monitoring of foreign objects during these activities. Upper internals maintenance was completed in 2R1 1 and 1 R1 2. There are no known issues in the feedwater system that would result in loose parts being transported to the SGs.

High flow, or susceptible areas.

Susceptible tube bundle areas are tubes adjacent to the annulus, due to high flow. The annulus region has been routinely FOSAR inspected every outage, and the vast majority of loose parts have been retrieved from this region. The most recent FOSAR in 2R12 and 1R13 identified a few wires of insignificant mass and one magnetic object.

Inspection limitations.

Previous FOSAR inspections have been confined to the annulus and tube lane, with several columns selected for in-bundle exams.

Categorizationof probable causes, origins, and migration.

Most of the loose parts have been due to upper internals secondary side maintenance activities, which were completed in 2R1 1 and 1R1 2.

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Enclosure 1 PG&E Letter DCL-06-129 Trends for foreign objects associated wear.

This element is not applicable to DCPP Unit 1 and 2, as no loose part wear indications have been detected over the life of the plant.

Eddy current detectability issues.

EPRI SG Examination Guidelines, Revision 6, Section 3.4, states that all peripheral tubes, including tubes adjacent to no-tube lane regions, shall be added to the periodic sample to monitor for loose parts, and that a secondary-side FOSAR examination may be used to meet this requirement. Possible crediting of FOSAR to meet this requirement was added in Revision 6 of the EPRI guideline because it was recognized that the bobbin probe has some detection limitations at the TTS due to the potential masking affects of the expansion transition on some small loose parts. For 2R13, the periodic sampling of the cold leg peripheral tubes was satisfied by 100 percent bobbin inspection as augmented by a special bobbin turbo mix evaluation of peripheral tubes (3 tubes in from outer periphery and tube lane) at the cold leg top of tubesheet, in order to detect potential tube degradation that could be missed by the bobbin probe (reference NRC IN 2004-17 dated August 25, 2004). This is considered satisfactory because: DCPP has a good FME program so there is low probability of having loose parts in SG; SG upper internals maintenance activities have been terminated after 2R11 and 1R12; DCPP has never detected any loose part tube wear; DCPP has performed FOSAR in every prior outage, chemical cleaning eliminated sludge piles; the WEXTEX transition region is small (on the order of 1/4 inch), such that bobbin should be able to detect large tube wear indications and loose parts that would be a potential threat to tube integrity; bobbin turbo mix analysis of cold leg TTS peripheral tubes should be able to detect tube wear indications in the periphery; and there are no known un-retrieved foreign objects in the last inspection (2R12).

Eddy currentinspection intervals.

Eddy current inspections will be performed in 2R13 and 1R14, so eddy current detection capability of potential loose parts and loose part wear is maintained.

Condition Monitoring In 2R13, 100 percent of the bobbin data was reviewed for PLP indications. In addition, a special in-depth analysis was performed for PLP indications along the full length of Rows 1 to 3 and the outer 3 peripheral tubes. At the hot leg top of tubesheet, Plus Point data was reviewed for PLPs during the 100 percent hot leg TTS Plus Point inspections. At the cold leg top of tubesheet for the outer three 34

Enclosure 1 PG&E Letter DCL-06-129 peripheral tubes (including tube lane), a special in-depth analysis for tube wear was performed using a turbo mix of the bobbin data in order to detect potential tube degradation in susceptible areas that could be missed by the bobbin probe.

No potential loose part signals or tube wear was detected by the eddy current inspections in 2R13. As such, the FOSAR contingency plan was not required to be implemented. In addition, the 2R12 PLP locations were re-addressed in 2R1 3 during the Plus Point top of tubesheet examination, and no PLP indications were detected, thus validating the pre 2R13 assumptions that the 2R12 indications could have been related to the sludge pile.

In conclusion, no tube wear from foreign objects were detected in 2R1 3, such that there were no challenges to structural integrity and leakage integrity performance criteria through EOC 13. No leakage should be postulated in a faulted SG following a SLB at EOC 13.

OperationalAssessment No foreign objects are expected that would challenge structural integrity performance criteria through EOC 14. In addition, no leakage should be postulated in a faulted SG following a SLB at EOC 14. This is based on the pre-2R13 evaluation that was performed to justify 2 cycles of operation without a secondary side visual inspection, as discussed above, in conjunction with the results of 2R13 eddy current inspections which showed no presence of PLPs or loose part wear.

5.6 Potential Axial PWSCC in High Row U-Bends (Non-active)

Westinghouse WOG evaluation SG-SGDA-03-33, "Generic Evaluation of U-Bend PWSCC Susceptibility for Model 51 SGs with Mill Annealed Alloy 600 Tubing," states that significant ovality could be experienced in large radius bends (Rows 10 and higher) that could have resulted in significant residual stresses in the tubes. These residual stresses could lead to axial PWSCC in large radius U-bends. Figure 5 of the WOG report graphs tube ovality by row, which are from DCPP Unit 2 SG tubing manufactured in Blairsville. This data suggests that Rows 13 to 15 ovalities could exceed Rows 3 to 9 ovalities. This is mostly likely due to changes in the Blairsville bending process starting in Row 13, where the bending die most likely changed from being radiused to being flat, as discussed in Section 7.4.1 of the WOG report. The WOG report indicates that this change of bending technique could also have occurred starting in Row 10; however, for the DCPP Unit 2 data set plotted in Figure 5 of the WOG report, it appears that the process changed at Row 13.

Figure 7 of the WOG report provides a plot of total strain percentage by row, combining the effect of longitudinal strain (from WOG report Figure 10 residual bending stresses) and hoop strain (from WOG report Figure 5 ovality data). This figure shows that the 35

Enclosure 1 PG&E Letter DCL-06-129 average strain in Rows 3 to 7 exceeds the average strain in any higher row, including Rows 13 to 15.

In 2R1 1, PG&E performed a first time Unit 2 Plus Point inspection of large radius (Rows 10 and higher) U-bends, consisting of 100 percent of U-bends to Row 46. In 1R1 2, PG&E performed a first time Unit 1 Plus Point inspection of large radius U-bends, consisting of 20 percent of U-bends in Rows 13 to 17. No axial PWSCC degradation was detected in these exams, or in the 100 percent Plus Point inspection of Rows 3 to 10 U-bends. This confirmed that axial PWSCC in high row U-bends is not an active damage mechanism at DCPP Units 1 and 2.

In 2R13, the following inspection plan was implemented to detect potential axial PWSCC in high row U-bends:

" In each SG, Plus Point inspection was conducted on 100 percent of U-bends in Rows 3 to 10. The critical area (CA) for axial PWSCC is defined as Rows 3 to 7, with a buffer zone defined as Row 8. Thus, 100 percent of the CA and buffer were inspected in each SG. Axial PWSCC indications in U-bends are capable of being detected by Plus Point using EPRI ETSS 96511.2.

• For greater than Row 10 U-bends, as a defense in depth approach (non-EPRI Appendix H), the bobbin coil was credited for detection of axial PWSCC in U-bends.

An expansion plan was documented in the Degradation Assessment, but was not required to be implemented.

In 2R13, axial PWSCC was not detected in the Plus Point inspection of 100 percent of Rows 3 to 10. Also, bobbin did not detect any U-bend signals that are indicative of potential axial cracking and that would require Plus Point inspection. These inspection results once again confirmed that axial PWSCC in high row U-bends in not active, and OA is not required.

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Enclosure 1 PG&E Letter DCL-06-129 Table 1 - 2R13 Eddy Current Inspection and Expansion Plan Item Area Probe Inspection Criteria Expansion Criteria I Full Length Bobbin 100% (Except Rows 1 and 2 U-bend) N/A Ifa C-3 condition is identified in the hot leg TTS inspection, inspect 20% of the cold leg TTS region in the affected SG in the current or subsequent outage. The 20% inspection should be biased to an area where degradation has the greatest potential to occur.

Ifcold leg TTS cracking is detected, then either:

Inspect 100% of the cold leg TTS region in the affected SG, plus 20% cold leg sample in the other SGs. If cracking is detected in the 20% sample, then inspect 100% of the cold leg TTS in the affected SGs.

OR t100% of hot leg TTS Define a critical area (CA) and buffer zone and inspect 100%

2 +Point 1of the tubes in the CA and buffer zone in the affected SG, plus 20% of the cold leg CA sample in the other SGs.

Ifcold leg TTS non-crack-line indications are detected, then either:

WEXTEX Region TTS Define a critical area of the tubes in the CA(CA) and and buffer buffer zonezone in theandaffected inspect 100%

SG, plus 20% cold leg CA sample in the other SGs.

OR For Category C-2 cold leg results, inspect an additional 20%

cold leg sample in the affected SG.

For Category C-3 cold leg results, inspect 100% of the cold leg TTS region in the affected SG, plus 20% cold leg sample in the other SGs.

Hot leg WEXTEX inspection extent is 3Hotoint

+2 from tos-8c.Coldele enEXTEXIfinitial inspection 3 +Point from +2" to -8". Cold leg WEXTEX increase inspectionextent extent.is less than flexible W* length, region extent is +2" to -8.5".

100% of hot leg WEXTEX anomalies if crack-like indications are detected in hot leg WEXTEX 4 +Point (NTE anomaly extent is +2" to tube anomalies, then inspect 100% of the cold leg WEXTEX end) anomalies.

5 +Point 100% of previous W* indications N/A within the W* length 6 +Point 100% of bobbinin distorted tubesheet N/A signals (DTS) the W* length 7 Low Row - +Point 100% of Rows 1 and 2 N/A bends If circ PWSCC detected in Rows 9 or 10, expand to Row 20 at 100%.

If circ PWSCC detected in Rows 11 through 14, redefine High Row U- critical area (CA) and buffer zone based on review of Figure 8 bends for Circ +Point 100% of Rows 3 to 10 10 of WOG U-Bend report and application of a factor of two PWSCC reduction in longitudinal strain, and inspect 100% of the new CA and buffer zone in the affected SGs.

If circ PWSCC detected in Rows 15 through 20, expand to 100% of all remaining rows in the affected SGs.

If axial PWSCC is detected in Rows 3 to 8 with NDD in Rows 9 and 10, then in the affected SG inspect 100% of Rows 11 to 16, 50% of Row 17, and 20% of Row 18.

If axial PWSCC is detected in Rows 9 to 10, then inspect High Row U- 100% of Rows 11 to 25 in the affected SGs.

9 bends for Axial +Point 100% of Rows 3 to 10 If axial PWSCC is detected in Rows 11 to 25, then review PWSCC Figure 5 of the WOG U-Bend report to define a critical area and buffer zone based on tube ovality data, and inspect 100% of the CA and buffer zone in the affected SGs.

Ifaxial PWSCC is detected in greater than Row 25, then inspect 100% of all rows in the affected SGs.

10 Ž5Volts 10 Dentedots Dented TSP I +Point 100% N/A 37

Enclosure 1 PG&E Letter DCL-06-129 Table 1 - 2R13 Eddy Current Inspection and Expansion Plan Item Area Probe Inspection Criteria Expansion Criteria

• SG 2-1: 20% of >2 and <5 volts dents at 1H

• SG 2-2: 100% of >2 and <5 If PWSCC (at any size dent), circumferential indications (at volts dents from 1H to 5H, 20% any size dent), or >2 inferred volts AONDB (at >2 and <5 at 6H volts dent) are detected at a TSP elevation where 100%

• SG 2-3, 2-4: 100% of >2 and <5 inspections were not required, expand the Plus Point

>2 Volts and volts dents from 1H to 3H, 20%

><5 11

<5 Volts +Poid vts at 4H ds finspections and 20% at (in 11 Volts +Point nexta step-wise manner, TSP) up through the100% to affected hot leg TSP side of the SG Dented TSP For any 20% sample, a minimum of and down the cold leg side until a 20% sample is obtained 50 >2 volts and <5 volts dents shall that is free from PWSCC, circumferential cracking, or >2 be inspected. Ifthe population of >2 inferred volts AONDB.

volts and <5 volts dents at that TSP elevation is less than 50, then 100%

of the >2 volts and <5 volts dents at that TSP shall be inspected.

Generic criteria: On a SG-specific basis, if a circ indication or

>2 inferred volts AONDB is detected in a dent of 'x' volts, N/A where 'x" is less than or equal to 2.3 volts, then expand Plus Point inspections to include 100% of dents greater than "x -

Note: Bobbin is used for detection of 0.3" volt up to the affected TSP, plus 20% of dents greater 12 2DentedTsP +Point axial PWSCC in <2 volts dents. than "x- 0.3" volt at the next higher TSP.

+Point inspection of <2 volts dents is not required, unless dictated by Note: For any 20% sample, a minimum of 50 "x - 0.3" volt expansion requirements. dents shall be inspected. If the population of "x - 0.3" volt dents at that TSP elevation is less than 50, then 100% of the "x - 0.3" volt dents at that TSP shall be inspected.

Repeat 13 PWSCC ARC +Point 100% N/A Indications at Dents 14 DIS +Point 100% of distorted ID support plate N/A bobbin signals (DIS) at dented TSP 100% of bobbin distorted OD support 15 +Point signals (DOS) at dented intersections N/A (no lower voltage cutoff) 16 +Point 100% of DOS >1.7 volts N/A 17 +Point DOS with suspected TSP ligament N/A cracking (SLC) 18 +Point Any bobbin indication region exclusion zone in the wedge N/A 19 +Point DOS at 7th TSP exclusion zone N/A 20 TSP Inspection +Point DOS that extend outside the TSP N/A for ODSCC 2+iT Isco crevice

< 100% of hot leg intersections with ARC >2.3 volts SPR (mixed residual N/A signal), and minimum of 5 largest hot leg SPR per SG.

22 +Point TSP with copper signals N/A 100% of prior cycle AONDB (bounds 23 +Point commitment AONDB that to inspectto100%

continue of by be NDD N/A bobbin in current inspection) 100% of prior cycle TSP SAI-OD that 24 +Point are NDD by bobbin in current N/A inspection 100% of existing baseline Plus Point 25

• TSP Ligament +Point confirmed TSP ligament cracking (LIC N/A Cracking or LIG) indications. __I 26 +Point 100% of bobbin SLC indications. N/A 38

Enclosure 1 PG&E Letter DCL-06-129 Table 1 - 2R1 3 Eddy Current Inspection and Expansion Plan Item Area Probe Inspection Criteria Expansion Criteria 20% of >5 volts dings in U-bend 20% of >5 volts dings in straight legs, If ding ODSCC is detected, inspect 100% of >5 volts dings 27 +Point biased to lower hot leg elevations, up/down to the coldest elevation at which degradation has Free Span Note: Bobbin is credited for detection been reported, plus 20% at next elevation.

Dings _____of SCC in <5 volts dings 28 +Point 20% of >2 volts dings in the U-bend If ODSCC is detected at dings in the U-bend coincident with that are -coincident with AVB location AVB locations, coincident then inspect with AVB 100% of >2 volts ding indications structures.

Free span 100% of free span bobbin indications 29 29 bobbin indications +Point that are new or exhibit growth or N/A (MBI, FSI, DNI) change.

30 30 Cotd leg at TSP thinning +Point 100% of new CLT indications. N/A Bobbin If possible loose part (PLP) indication 31 Possible loose or is detected by eddy current, perform N/A parts +Point eddy current inspection to bound the loose part.

39

Enclosure 1 PG&E Letter DCL-06-129 Table 2 Tubes Plugged in 2R13 LOCATION MECHANISM ORIENT 21 22 23 24 Total PWSCC ARC Axial 1 2 3 WEXTIEX TTS ODSCC Circ 1 1 PWSCC ARC Axial 2 2 PWSCC Circ 1 1 ODSCC ARC Axial 3 3 3 29 38 Hot Leg TSP ODSCC Circ 10 10 PWSCC MixMode Axial/Circ 2 2 PWSCC/ODSCC Axial 2 2 Cold Leg TSP Thinning 2 2 PWSCC Axial 2 2 Rows 1 and 2 U-bend Data Quality 1 1 Row 3 to Row 10 U-bend PWSCC Circ 1 1 1 3 U-bend AVB Wear 1 1 Free Span Ding ODSCC Axial 1 1 2 Pluggable Tubes 6 23 6 35 70

% Plugged 2R13 0.18 0.73 0.18 1.15 0.56

% Plugged to Date 3.69 7.91 3.84 10.83 6.57 Note: Some tubes may be plugged for multiple degradation mechanisms. In these cases, the tube is listed in only one degradation mechanism category.

40

Enclosure 1 PG&E Letter DCL-06-129 Table 3 DCPP Unit 2 Historical Tube Plugged by Mechanism and SG LOCATION MECHANISM ORIENT 21 22 23 24 Total WEXTEX TTS PWSCC Axial 24 7 19 18 68 PWSCC Circ 3 4 3 5 15 ODSCC Circ 1 1 0 0 2 Volumetric 1 2 1 0 4 Hot Leg TSP PWSCC Axial 0 86 5 25 116 PWSCC Circ 0 37 0 2 39 ODSCC Axial 50 38 45 271 404 ODSCC Circ 0 19 0 0 19 PWSCC MixMode Axial/Circ 0 8 0 0 8 ODSCC MixMode Axial/Circ 0 0 0 0 0 PWSCC/ODSCC Axial 0 5 1 5 11 Volumetric 0 1 0 0 1 Cold Leg TSP Thinning 17 24 9 5 55 Volumetric 1 0 1 0 2 Rows 1 and 2 U-bend PWSCC Axial 13 11 20 14 58 PWSCC Circ 4 4 2 1 11 Preventive Data Quality 2 5 4 1 12 Row 3 to Row 10 U-bend PWSCC Circ 2 2 5 8 17 U-bend AVB Wear 2 5 4 3 14 Preventive Data Quality 0 2 1 2 5 U-bend Probe Restriction 1 0 0 1 2 Free Span above TTS Mech Damage 3 5 5 2 15 Free Span Ding ODSCC Axial 1, 1 0 0 2 Preventive Fatigue (88-02) 0 1 5 1 7 3dPNO in-situ "leaking" tube NDD 0 0 0 3 3 Pluggable Tubes 125 268 130 367 890

% Plugged 3.69 7.91 3.84 10.83 6.57 Note: Some tubes may be plugged for multiple degradation mechanisms. In these cases, the tube is listed in only one degradation mechanism category.

41

Enclosure 1 PG&E Letter DCL-06-129 Table 4 - DCPP Unit 2 Tubes Plugged by Mechanism and Outage LOCATION MECHANISM ORIENT 2R1 2R2 2R3 2R4 2R5 2R6 2R7 2R8 2R9 2R10 2Rl1 2R12 2R13 Unplug Total Cycle EFPY 1.023 1.024 1.11 1.27 1.31 1.34 1.33 1.62 1.46 1.44 1.60 1.52 1.31 Cumulative EFPYs 1.02 2.05 3.16 4.43 5.74 7.08 8.41 10.03 11.49 12.93 14.57 16.09 17.40 WEXTEX Tubesheet PWSCC Axial 24 11 34 27 5 1 4 2 3 43 68 PWSCC Circ 1 1 8 3 1 1 15 ODSCC Circ 1 1 2 Volumetric 1 3 4 Hot Leg TSP PWSCC Axial 17 3 53 26 18 15 4 6 2 28 116 PWSCC Circ 16 6 5 4 6 1 1 39 ODSCC Axial 3 8 68 7 22 28 269 28 38 67 404 ODSCC Circ 5 2 1 1 10 19 PWSCC Ax/Circ 3 1 1 1 2 8 ODSCC MixMode Ax/Circ 0 PWSCC/ODSCC Axial 1 1 6 1 2 11 OD - Volumetric 1 1 Cold Leg TSP Thinning 5 10 10 3 7 8 9 1 2 55 Volumetric 2 2 Rows 1 and 2 UB PWSCC Axial 10 2 32 9 1 2 2 58 PWSCC Circ 6 3 1 1 11 Data Quality 1 10 1 12 Rows 3 through 10 UB PWSCC Circ 12 2 3 17 U-bend AVB Wear 1 3 2 2 3 2 1 14 Preventive Data Quality 4 1 5 U-bend Probe restriction 1 1 1 1 2 Free Span above TTS Mech damage 2 3 5 5 15 Free Span Ding ODSCC Axial 2 2 Preventive Plugging NRCB 88-02 5 2 7 Precautionary Plugging NRCB 88-02 19 19 0 3dPNO in-situ "leaking" NDD 3 3 Tubes Plugged 2 31 0 1 62 38 231 91 67 64 340 51 70 1048 Tubes Unplugged 0 0 19 0 1 0 0 0 138 0 0 0 0 158 Cum. Tubes Plugged 2 33 14 15 76 114 345 436 365 429 769 820 890 890 Cum. Tubes Plugged 0.01 0.24 0.10 0.11 0.56 0.84 2.55 3.22 2.69 3.17 5.67 6.05 6.57 6.57 Note: Some tubes may be plugged for multiple degradation mechanisms. In these cases, the tube is listed in only one degradation mechanism category.

42

Enclosure 1 PG&E Letter DCL-06-129 Table 5 - 2R13 Circumferential Indications and Growth Rates ODSCC Adjusted Adjusted for Upper for Upper 95% NDE Unadjusted NDE Adjusted NDE 95% NDE Uncertainty Uncertainty Mix Uncertainty Growth Rate per EFPY Mode Only SG R C TSP Crk Axial Max Dent Orient Stab Mix Angle MD AD Angle MD AD % Angle MD AD Angle MD AD Angle MD AD Volt No. Elev Volt Volt Mode deg  %  % deg  % deg  %  % deg  %  % deg  %  %

22 2 40 1H 1 -0.29 0.15 OD Yes 28.2 86 68.7 28.2 77.0 64.2 172.1 91.4 71.5 131.5 91.4 73.4 -6.0 -9.9 -8.4 -0.02 22.92 Yes 22 2 40 1H 2 -0.24 0.21 OD Yes 21.2 94 73.9 21.2 86.0 69.8 169.2 98.0 75.0 127.9 98.0 76.9 -2.1 1.3 0.6 -0.01 22 5 30 1H 1 0.25 0.18 50.10 OD 25.2 1 0.9 25.2 45.0 35.6 170.9 68.0 53.7 0.5 0.0 3.0 0.02 22 10 30 1H 1 0.05 0.16 OD Yes 24.9 1 0.9 24.9 45.0 35.8 170.8 68.0 53.8 129.8 68.0 55.4 0.7 0.0 1.1 0.02 11.84 Yes 22 10 30 1H 2 0.14 0.30 ID Yes 25.0 42 27.6 25.0 36.0 21.6 78.9 61.3 40.6 -2.3 0.8 1.1 -0.01 22 11 31 1H 1 -0.17 0.32 31.90 OD 29.1 35 15.9 29.1 45.0 33.0 172.5 68.0 52.1 -3.1 0.0 -0.2 0.12 22 13 24 1H 1 -0.28 0.16 37.29 OD 31.2 94 69.6 31.2 82.0 63.8 173.4 95.0 71.3 NDD 22 14 39 1H 1 -0.33 0.13 29.96 OD 18.2 82 60.0 18.2 68.5 52.1 168.0 85.2 63.9 NDD 22 15 53 1H 1 0.06 0.23 13.95 OD 52.6 12 3.3 52.6 45.0 37.6 182.2 68.0 54.9 4.7 0.0 0.9 0.02 22 17 29 4H 1 -0.08 0.57 18.28 OD 25.4 39 26.4 25.4 45.0 30.6 171.0 68.0 50.6 3.4 0.0 -1.8 -0.06 22 19 26 1H 1 -0.18 0.22 20.08 OD 32.7 34 20.1 32.7 45.0 34.5 174.0 68.0 53.0 NDD 22 19 27 1H 1 -0.32 0.11 OD 18.2 37 20.6 18.2 45.0 31.8 168.0 68.0 51.4 NDD 41.38 Yes 22 19 27 1H 2 0.32 0.17 OD 25.4 1 0.9 25.4 45.0 34.0 171.0 68.0 52.7 6.8 0.0 2.0 0.00 22 19 32 1H 1 0.02 0.14 4.03 OD 32.7 21 4.9 32.7 45.0 33.5 174.0 68.0 52.4 0.8 0.0 -0.8 0.02 22 24 30 1H 1 0.06 0.22 5.35 OD 21 26 14.1 21 45.0 32.7 169.2 68.0 51.9 -4.8 0.0 0.7 0.06 24 11 16 3H 1 -0.18 0.44 39.06 ID 25.9 99 77.7 25.9 79.0 51.3 79.8 92.5 60.6 1.7 -3.8 -5.2 0.16 22 22 24 TS 1 -0.05 0.16 NA OD 73 73 190.6 NDD H

Note 1: Growth rate based on adjusted NDE, not the uncertainty adjusted NDE.

Note 2: Location (inch) is relative to the centerline of the tube support plate, or top of tubesheet.

Note 3: Tube stabilization determined per evaluation by Westinghouse.

Note 4: NDD means prior outage lookup did not detect any degradation, so no growth rate can be assigned for indication.

Note 5: SG 2-2 R22C24 TSH indication was too small to be depth profiled using line by line sizing technique.

43

Enclosure 1 PG&E Letter DCL-06-129 Table 6 - DCPP Units 1 and 2 Axial ODSCC and Axial PWSCC at Same TSP Intersection (IDIOD Flaws)

MmPWSCC NDE Data ODSCC NDE Data I ~~Minimum I____

DoS I I bin Dent ID/OD ActiveID/OD tube Insp SG Row Col TSP Separation Deplug when Crack PWSCC Length MD AD Max. No. OD ODSCC Larget Angle detected? No. New? (in.) (%) (%) Volt Cracks New? Bobbin Bobbin +Point (Deg.) Voltage Voltage Volts 2R13 24 22 21 03H 2.8 67 1 New 0.24 45.0 34.9 0.90 1 New NA 0.41 0.11 2R13 24 23 52 02H 1.65 64 1 New 0.11 33.0 23.4 0.52 1 0.83 NA 0.29 1R13 11 14 6 2H 0.61 55 1 New 0.17 51 31.9 1.01 1 New NA 0.53 0.23 1R13 11 15 24 2H 0.59 36 1 New 0.25 37 29.6 0.98 1 0.65 NA 0.26 1R13 11 38 54 2H 2.99 56 1 New 0.11 20 12.4 0.59 1 NA 0.55 0.25 1R13 12 34 26 2H 0.75 83 1 New 0.1 31 22.1 0.79 1 New NA 0.47 0.17 1R13 12 5 65 1H 0.72 77 IR10 1 0.35 31 25.3 0.65 1 New NA 0.44 0.14 1R13 12 31 66 1H 0.33 63 1Rll 1 New 0.16 22 14.4 0.34 1 New NA 0.44 0.14 1R13 12 33 68 2H 0.85 44 1 0.07 40.5 26 0.59 2 New NA 0.62 0.17 1 0.09 20 11.1 0.57 1R13 12 13 84 1H 0.93 64 1 New NA 0.57 0.27 2 0.09 25 14.4 0.36 2R12 22 16 30 2H 1.61 78 1 New 0.1 30 19.8 0.47 1 0.59 NA 0.19 1R12 11 26 25 1H 1.95 55 1 0.28 49 33.2 1.31 1 New NA 0.52 0.22 1R12 11 28 27 1H 2.29 67 1 0.34 52 33.1 1.22 2 New NA 0.78 0.3 1R12 12 5 39 2H 0.69 86 1R1l 1 0.19 36 28.5 1 1 New 0.36 NA 0.24 1R12 12 12 77 1H 1.5 55 IRl 1 0.4 54 36.4 1.4 2 New NA 0.68 0.2 1R12 12 22 54 2H 2.14 60 1Rll 1 0.33 60 48.1 2.43 1 New NA 0.54 0.24 1R12 12 23 82 1H 1.47 66 1 0.08 27 17.7 0.49 2 New 0.26 NA 0.26 2R11 22 12 71 1H 4.63 61 1 New 0.11 37 24.6 0.39 1 NA 0.46 0.16 2R11 22 22 67 2H 0.63 53 1 New 0.23 38 24.8 0.91 2 4.58 NA 2.66 2R11 22 24 58 2H 1.08 147 1 New 0.07 20 12.8 0.29 1 New NA 0.52 0.22 2R11 22 28 38 1H 1.56 55 1 0.16 33 17.6 0.44 2 New 0.86 NA 0.15 2R11 23 8 66 1H 1.42 78 1 New 0.11 20 14.5 0.43 1 0.62 NA 0.24 2R11 24 16 11 3H 1.27 83 2R9 1 0.26 30 17.2 0.72 1 New 0.63 NA 0.18 2R11 24 34 43 3H 4.63 63 1 New 0.39 36 22.8 0.65 3 1.73 NA 0.72 1R11 11 14 87 2H 0.51 71 1 New 0.09 30 20.8 0.29 1 0.62 NA 0.63 1l 111115 81 2H 1.2 82 1 New 0.19 21.5 12.4 0.5 1 0.75 NA 0.36 44

Enclosure 1 PG&E Letter DCL-06-129 Table 6 - DCPP Units I and 2 Axial ODSCC and Axial PWSCC at Same TSP Intersection (ID/OD Flaws)

Minimum PWSCC NDE Data ODSCC NDE Data Insp SG Row Col TSP Dent Volt ID/OD Separation Angle 1 Deplug 0 1ec ActiveID/OD when tube dV l Crack PWSCC Length TMD AD Max. No. OD TODSCC BBobbin Bobbin B In) +Pointt Largin Angle detected? No. New? (in.) (%) (%) Volt Cracks New?Voltage Volts

-(Deg.) VolagVotae _Vlt 1Rl 11 16 45 2H 1.32 71 1 New 0.14 34 22.1 0.84 2 New 1.29 NA 0.16 1R11 11 22 71 2H 0.83 81 1 0.11 40 28.6 0.67 1 New NA 0.46 0.16 1R11 11 24 20 2H 1.43 49 1 0.07 43 22.7 0.71 1 New 0.81 NA 0.22 1R11 11 33 40 2H 0.86 59 1 New 0.26 45 28.7 1.13 2 New 1.26 NA 0.25 1Rll 11 36 30 2H 0.56 46 1 0.17 43 30.5 1.34 2 New NA 0.71 0.22 1R11 12 5 59 1H 1.02 49 1R11 No 1 0.34 43 32.4 1.3 2 NA 0.71 0.22 1R1l 12 6 70 2H 1.54 71 1R1l No 1 0.11 36 25.8 0.79 2 NA 0.75 0.25 1 0.07 20 12.4 0.31 1R1l 12 7 28 2H 2.33 64 1Rl No 1 NA 0.47 0.17 2 0.1 24 14.9 0.55 1R1l 12 7 56 1H 1.13 90 1R1l No 1 0.26 43 34.3 2.2 1 NA 0.50 0.2 1Rll 12 7 84 1H 2.19 53 1Rll No 1 0.34 45 35.6 3.06 1 NA 0.58 0.28 1Rll 12 8 67 1H 1.2 64 1 0.2 29 16.9 0.88 1 New NA 0.44 0.14 1Rll 12 8 51 1H 1.48 76 1Rl No 1 0.18 32 19.2 0.69 1 0.51 NA 0.19 1R1l 12 9 28 1H 2.53 71 1Rl No 1 0.16 47 30.3 1.47 2 NA 0.72 0.27 1R1l 12 9 77 1H 2.45 95 1Rll No 1 0.23 39 23.4 1.34 1 0.62 NA 0.29 1R1l 12 10 35 1H 1.34 80 1Rll No 1 0.11 51 33.4 1.65 1 NA 0.49 0.19 1R1l 12 10 83 1H 6.72 60 1R1l No 1 0.27 64 37.5 1.15 2 NA 0.72 0.25 IRll 12 11 27 1H 2.13 49 1R1l No 1 0.5 29 18.7 0.86 1 NA 0.51 0.21 1R111 12 11 47 2H 2.32 73 1R11. No 1 0.21 36 26.7 1.06 1 NA 0.50 0.2 1R1l 12 12 66 2H 2.21 80 1R1l No 1 0.13 45 30.9 1.51 1 NA 0.57 0.27 1R1l 12 12 80 1H 1.04 49 1Rll No 1 0.07 20 12.9 0.6 1 0.45 NA 0.24 1R1l 12 12 84 2H 0.73 64 1Rll No 1 0.29 42 31.1 1.5 1 0.55 NA 0.35 1R1l 12 13 81 1H 3.18 49 1Rll No 1 0.13 23 16.5 0.88 1 0.43 NA 0.33 1R1l 12 13 89 1H 2.33 57 1Rll No 1 0.4 53 41.3 2.97 1 0.56 NA 0.44 1 0.12 21 15.2 0.64 1Rll 12 16 73 1H 18.03 47 1R10 1 New NA 0.49 0.19 2 0.15 20 12.3 0.5 1Rll 12 16 76 2H 0.52 64 IR1O 1 0.18 20 9.7 0.39 1 New 0.05 NA 0.2 1R1l 12 17 8 6H 2.95 75 1R1l No 1 0.23 24 15.6 0.81 1 NA 0.55 0.25 1R1l 12 19 14 2H 1.34 84 1Rl No 1 0.18 44 35 1.73 1 NA 0.52 0.22 45

Enclosure 1 PG&E Letter DCL-06-129 Table 6 - DCPP Units 1 and 2 Axial ODSCC and Axial PWSCC at Same TSP Intersection (ID/OD Flaws)

Minimum PWSCC NDE Data ODSCC NDE Data Dent MID/OD Active tube DOS Inferre Largest Insp SG Row Col TSP Volt Separation Deplug when ID/OD Crack PWSCC Length MD AD Max. No. OD ODSCC Bobbin Bobbin +Point Volt Angle detected? No. New? (in.) (%) (%) Volt Cracks New? Bobban Bobbin +oit (Deg.) Voltage Voltage Volts 1Rll 12 19 51 1H 1.21 76 1Rl No 1 0.57 54 44 3.24 1 NA 0.62 0.32 1Rl 12 20 52 2H 2.55 83 1Rl No 1 0.23 43 28.3 0.91 1 NA 0.50 0.2 1 0.54 57 40.3 2.09 1 NA 0.49 0.19 1R1l 12 20 58 1H 0.65 55 1Rll No 2 0.19 54 44.4 2.23 1Rl 12 21 37 4H 2.25 80 1R1l No 1 0.25 34.5 24.2 0.88 1 NA 0.46 0.16 1R1l 12 21 42 1H 4.87 57 1R1l No 1 0.46 42.0 33.2 1.41 1 New NA 0.78 0.47 1 0.76 57 47.1 2.04 1Rl 12 21 50 1H 2.38 56 1R1l No 1 NA 0.95 0.64 2 0.56 64 39 1.65 1Rll 12 21 53 6H 2.52 56 1R1l No 1 0.62 64 50.7 1.97 1 NA 0.51 0.21 1Rll 12 22 32 2H 1.44 51 1R1l No 1 0.27 54 42.1 2.28 2 NA 0.71 0.23 IR1l 12 22 34 2H 0.69 51 1R1l No 1 0.18 42 31.3 1.03 3 NA 0.84 0.23 1 0.08 30 22 0.58 1R11 12 22 38 1H 4.7 65 1R11 No 2 NA 0.74 0.22 2 0.61 48 38.7 2.19 1R11 12 25 72 1H 2.06 77 1 New 0.09 24 17.3 0.48 1 New NA 0.45 0.15 1R1l 12 26 71 2H 1.4 75 1R1l No 1 0.42 42 30.5 1.68 1 NA 0.48 0.18 1R11 12 26 77 2H 0.71 68 1R1l No 1 0.44 50 38.9 1.87 1 0.81 NA 0.36 1Rl. 12 26 78 11H 1.29 68 IRll No 1 0.32 50 38.6 2.43 1 NA 0.63 0.33 1Rll 12 27 50 1H 1.95 34 1 0.11 27 17.4 0.88 1 New NA 0.49 0.19 1Rll 12 27 36 2H 0.54 58 1Rll No 1 0.09 20 12.5 0.77 1 NA 0.42 0.12 1Rll 12 28 56 2H 0.75 79 1Rll No 1 0.25 40 29.2 1.12 1 NA 0.41 0.11 1Rll 12 28 58 1H 1.67 72 1Rll No 1 0.6 60 44.9 3.05 1 NA 0.52 0.22 1Rll 12 28 68 6H 1.26 57 1Rll No 1 0.08 21 10.9 0.56 1 0.32 NA 0.11 1Rll 12 29 43 2H 1.34 69 1R1l No 1 0.24 39 31.1 1.86 2 0.62 NA 0.42 1R11 12 29 56 2H 1.34 106 IR11 No 1 0.25 34 24.6 1.82 1 NA 0.52 0.22 1Rl 12 29 67 2H 3.02 83 1Rl1 No 1 0.36 48 36.9 2.11 1 NA 0.55 0.25 1Rl 12 30 16 1H 0.9 48 1 0.15 41 28 0.7 1 New NA 0.62 0.32 1 0.11 20 9.7 0.32 1R1l 12 31 32 3H 1.67 69 IR1l No 1 NA 0.39 0.09 2 0.34 48 40.6 1.67 IRl 12 35 45 2H 1.82 95 1R1l No 1 0.29 48 35.7 1.41 1 0.43 NA 0.27 46

Enclosure 1 PG&E Letter DCL-06-129 Table 6 - DCPP Units 1 and 2 Axial ODSCC and Axial PWSCC at Same TSP Intersection (IDIOD Flaws)

Minimum PWSCC NDE Data ODSCC NDE Data Dent ID/OD Active tube DOS Inferred Largest Insp SG Row Col TSP Volt Separation Deplug when ID/OD Crack PWSCC Length MD AD Max. No. OD ODSCC Bobbin Bobbin +Point Volt Angle detected? No. New? (in.) (%) (%) Volt Cracks New? B (Deg.) Voltage Voltage Volts 1R11 12 35 65 2H 2.36 46 1Rl No 1 0.31 48 37.4 1.88 3 NA 0.90 0.23 1R1l 12 37 72 1H 1.65 76 1Rl No 1 0.17 34 24.5 0.93 1 NA 0.55 0.25 1Rl 12 38 70 1H 2.42 61 1R1l No 1 0.09 20 15.6 0.52 1 NA 0.61 0.31 1Rl1 12 40 63 1H 0.87 83 1R1l No 1 0.11 21 9.9 0.46 1 NA 0.67 0.36 1Rll 12 42 28 2H 1.41 69 1 0.11 32 20.1 0.88 1 New NA 0.58 0.28 1R10 11 28 50 1H 0.35 47 1R10 No 1 0.09 29 19.1 0.64 2 0.96 NA 0.81 1R10 12 9 34 2H 1.47 44 1 New 0.09 21 13.3 0.41 2 0.76 NA 0.26 1 0.42 38 16.3 1.04 1R10 12 14 72 2H 2.92 58 1R10 No 1 NA 0.51 0.21 2 0.07 20 12 0.58 IR10 12 14 82 1H 1.55 61 IR10 No 1 0.05 20 10 0.39 1 NA 0.53 0.23 1R10 12 15 10 1H 1.76 90 1 0.21 24 14 0.48 1 New 0.44 NA 0.27 1R10 12 17 60 2H 2.92 51 1R10 No 1 0.17 22 7.2 0.56 1 NA 0.54 0.24 1R1O 12 24 72 1H 1.24 82 1R10 No 1 0.26 22 15.5 0.4 1 0.27 NA 0.14 1R10 12 26 43 2H 2.12 70 1R10 No 1 0.26 30 15.4 0.81 1 NA 0.56 0.26 1R10 12 27 71 1H 1.86 74 1 0.23 39 25.4 1.12 2 New NA 0.77 0.3 1R10 12 33 37 1H 2.01 79 1 New 0.11 20 12 0.38 1 New NA 0.50 0.2 1R10 12 38 61 1H 3.91 51 1R10 No 1 New 0.09 20 13 0.48 1 NA 0.71 0.4 1R10 12 38 63 1H 2.35 79 1 New 0.14 22 13.9 0.78 1 New NA 0.68 0.37 1R10 12 41 62 1H 0.95 109 1 New 0.21 27 17 0.54 1 New NA 0.54 0.24 1R9 11 9 6 1H 0.95 79 1 New 0.13 37 27.2 0.38 1 New 0.35 NA 0.27 1R9 12 6 47 1H 0.77 44 1 New .0.12 26 16.7 0.35 1 New 0.34 NA 0.11 1R9 12 13 75 2H 2.23 53 1 New 0.11 20 11 0.42 1 New 0.37 NA 0.14 2R7 24 9 12 13H 1.84 89 1 New 0.32 123 17.8 11.64 1 New 1 1.25 NA [0.38 2R8 124 34 1 34 1 3H 2.96 1 57 _ 1 [ New 0.16 135.5126.410.381 1 New I NA 0.62 1 0.32 47

Enclosure 1 PG&E Letter DCL-06-129 Table 7 2R13 Axial PWSCC Indications in Row I U-bends 2R1 3 2R1 2 Growth Rate per EFPY Crack Cal Max. Length MD % MD % Max. Length MD % MD % Max. Length MD %

No. No. Volt (in.) phase amplitude Volt (in.) phase amplitude Volt (in.) amplitude 23 1 37 1 7H + 3.67 to 3.78 inch 78 0.68 0.11 93 33 0.50 0.09 73 35 0.14 0.02 -1.9 23 1 -45 1 7H + 3.67 to 3.78 inch 75 1.00 0.11 99 52 0.83 0.11 98 47 0.13 0.00 3.8 Note: Maximum depth (MD) phase estimates are the largest depths reported in the phase angle line by line depth profiling. MD amplitude estimates are taken as the depth at the maximum amplitude from the line by line sizing profile, and are considered to be more representative of the true MD for small voltage indications.

Table 8 2R13 Circumferential PWSCC Indications in U-bend Flank Locations 2R1 3 2R12 Growth Rate per EFPY Crack Cal Max Length MD % MD % Max Length MD % MD % Max Length MD %

No. No. volt deg phase amplitude volt deg phase amplitude volt deg amplitude 21 7 55 1 61 7H + 19.65 inch 0.22 15.6 85 42 0.12 14.3 68 48 0.08 1.0 -4.6 23 7 32 1 66 7H + 10.02 inch 0.35 16 56 45 0.17 14.6 63 49 0.14 1.1 -3.1 24 8 25 1 48 7H + 26.09 inch 0.47 15.4 72 50 0.25 15.6 63 50 0.17 -0.2 0.0 24 8 25 2 48 7H + 38.10 inch 0.59 18.5 98 58 0.36 15.7 63 51 0.18 2.1 5.3 24 8 25 3 48 7H + 38.39 inch 0.79 18.5 75 66 0.52 23.5 84 52 0.21 -3.8 10.7 Note: Maximum depth (MD) phase estimates are the largest depths reported in the phase angle line by line depth profiling. MD amplitude estimates are taken as the depth at the maximum amplitude from the line by line sizing profile, and are considered to be more representative of the true MD for small voltage indications.

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Enclosure 1 PG&E Letter DCL-06-129 Table 9 DCPP Units 1 and 2 Inspection Scope of Dings Plus Point Inspection Scope Bobbin Credit General >2v UB ding at AVB 2R7 20% >2v dings at lower HL elevations 1R8 20% >2v dings at lower HL elevations 2R8 20% >2v dings at lower HL elevations 1 R9 20% >2v dings at lower HL elevations 2R9 20% >2v dings at lower HL elevations 1R10 20% >2v dings at lower HL elevations 2R10 20% >2v dings at lower HL elevations 1 R11 20% >2v dings at each HL elevation 2R11 100% >5v dings 100% <5v dings 1R12 100% >5v dings 100% <5v dings 2R12 100% >5v dings 20% <5v dings 1R13 20% >5v dings in UB, 20% >5v dings in straight 20% <5v dings legs (sample biased to lower HL elevations) 2 20% >5v dings in UB, 20% >5v dings in straight 2R13 legs (sample biased to lower HL elevations). 20% <5v dings Expanded to 100% >5 dings in SG 2-1 and 2-2.

Table 10 DCPP Units 1 and 2 Less Than 5 Volts Dings Population and Number of Plus Point Inspections

1. PP inspections of <5 volts dings over last Elevation <5 volts ding population four inspections Unit 1 Unit 2 Unit 1 Unit 2 TSH-1 H 93 79 40 26 1H-2H 51 81 22 10 2H-3H 54 29 21 5 3H-4H 63 43 28 6 4H-5H 74 34 24 1 5H-6H 78 38 30 4 6H-7H 93 40 21 1 7H-7C 774 281 758 555 7C-6C 86 41 12 11 6C-5C 70 36 10 2 5C-4C 85 34 19 1 4C-3C 103 38 21 1 3C-2C 67 43 5 1 2C-1C 51 57 0 1 1C-TSC 83 92 5 10 Total 1825 966 1016 635 49

Enclosure 1 PG&E Letter DCL-06-129 Table 11 2R13 Axial ODSCC Indications at Free Span Dings Bobbin Plus Plus Plus Plus P Plus .

Elevation Ding Bobbin Bobbin phase Point Point Point Point volt Point volt MD Outage SG Row Col Support (inch) volt call P4 volt P4 angle phase length of length of of ding of estimate P1 P4 angle ding ODSCC plus ODSCC (%)

(deg) (deg) (inch) (inch) ODSCC 2R13 2-1 1 30 2C 46.50 0.92 DNI 0.33 133 2 0.23 0.17 0.34 0.10 37 2R13 12-2 23 1 51 1 TSC 40.47 3.78 IDNI 1.42 137 11 0.44 0.22 0.79 0.25 55 Notes:

P1 - 400/100 kHz differential mix channel P4 - 100 kHz differential raw channel MD estimate is based on Plus Point voltage of ODSCC applying volt/depth correlation in Figure B-6 of EPRI -Report 1007904 (In-Situ Guidelines).

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