Text

Request for Alternative from Volumetric/Surface Examination Frequency Requirements of ASME Code Case N-729-4
	ML18213A375
Person / Time
Site:	Diablo Canyon
Issue date:	08/01/2018
From:	Welsch J; Pacific Gas & Electric Co
To:	; Document Control Desk, Office of Nuclear Reactor Regulation
References
	DCL-18-057
	Download: ML18213A375 (50)
	v • d • e

{{#Wiki_filter:m Pacific Gas and Electric Company"' James M. Welsch Vice President Nuclear Generation and Diablo Canyon Power Plant P.O. Box 56 Avila Beach, CA 93424 Chief Nuclear Officer 805.545.3242 E-Mail: James.Welsch@pge.com August 1, 2018 PG&E Letter DCL-18-057 U.S. Nuclear Regulatory Commission 10 CFR 50.55a ATTN: Document Control Desk Washington, D.C. 20555-0001 Docket No. 50-275; OL DPR-80 Docket No. 50-323; OL DPR-82 Diablo Canyon Power Plant Unit 1 and Unit 2 Request for Alternative from Volumetric/Surface Examination Frequency Requirements of ASME Code Case N-729-4

Dear Commissioners and Staff:

Pursuant to 10 CFR 50.55a(z)(1), Pacific Gas and Electric Company (PG&E) hereby requests approval of a proposed alternative for the Diablo Canyon Power Plant (DCPP) Units 1 and 2 lnservice Inspection program . This request is associated with the examination frequency requirements of the American Society of Mechanical Engineers (ASME) Boiler and Pressure Vessel Code, Section XI, Code Case N-729-4, which specifies that reactor pressure vessel closure head (RVCH) welded Alloy 690 penetration nozzles shall undergo volumetric/surface examinations on a nominal inspection frequency of ten years. The original DCPP Unit 1 and Unit 2 RVCHs, which were manufactured with Alloy 600/82/182 materials, were replaced with new RVCHs using Alloy 690/52/152 materials during the refueling outages that ended in November 2010 and November 2009, respectively. The proposed alternative would allow deferral of the volumetric/surface examinations of the RVCHs of both Units 1 and 2 beyond the nominal ten-year inspection interval required by Code Case N-729-4. The details of the proposed alternative are provided in the Enclosure. The inspection intervals would be extended from 2020 and 2019 through the end of the current operating licenses in 2024 and 2025 for Units 1 and 2, respectively. The requested alternative inspection interval provides an acceptable level of quality and safety, as demonstrated in the Enclosure. PG&E requests approval of the attached Alternative Request by February 28, 2019, in order to prepare for this change request. PG&E makes no new or revised regulatory commitments (as defined by NEI 99-04) in this letter. If you have any A member of the STARS Alliance Callaway

Diablo Canyon
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Document Control Desk PG&E Letter DCL-18-057 August 1, 2018 Page 2 questions or require additional information, please contact Mr. Hossein Hamzehee at (805) 545-4720. Sincerely, J a ~ Vice President, Nuclear Generation and Chief Nuclear Officer rntt/4231/50987963-01 Enclosure cc: Diablo Distribution cc/enc: Kriss M. Kennedy, NRC Region IV Administrator Christopher W. Newport, NRC Senior Resident Inspector Gonzalo L. Perez, Branch Chief, California Department of Public Health Balwant K. Singal, NRR Project Manager State of California, Pressure Vessel Unit A member of the STARS (Strategic Teaming and Resource Sharing) Alliance Callaway

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Enclosure PG&E Letter DCL-18-057 Diablo Canyon Power Plant, Units 1 and 2 10 CFR 50.55a Request Number ISI-RXHDVS Request for Alternative from Volumetric/Surface Examination Frequency Requirements of ASME Code Case N-729-4 Proposed Alternative in Accordance with 10 CFR 50.55a(z)(1)

     --Alternative Provides Acceptable Level of Quality and Safety--

Page 1 of 15

Enclosure PG&E Letter DCL-18-057 10 CFR 50.55a Request Number ISI-RXHDVS Proposed Alternative in Accordance with 10 CFR 50.55a(z)(1)

              --Alternative Provides Acceptable Level of Quality and Safety--

1. American Society of Mechanical Engineers (ASME) Code Components Affected The affected components are the Diablo Canyon Power Plant (DCPP) Unit 1 and Unit 2 ASME Code Class 1 reactor pressure vessel closure head (RVCH) nozzles and partial-penetration welds fabricated from Primary Water Stress Corrosion Cracking (PWSCC) -

resistant materials. Each unit's RVCH Control Rod Drive Mechanism (CROM) nozzles, thermocouple nozzles, vent nozzle, and reactor vessel level indication system (RVLIS) nozzle are fabricated from Alloy 690 material with Alloy 52/152 attachment welds.

2. Applicable Code Edition and Addenda

The applicable Code edition for the DCPP fourth lnservice Inspection (ISi) interval, which began on May 7, 2015, for Unit 1 and March 13, 2016, for Unit 2, is ASME Boiler and Pressure Vessel Code (ASME Code) Section XI, "Rules for lnservice Inspection of Nuclear Power Plant Components," 2007 Edition, with 2008 Addenda.

3. Applicable Code Requirement

10 CFR 50.55a(g)(6)(ii)(D)(1) requires (in part) that: "Holders of operating licenses or combined licenses for pressurized-water reactors as of or after August 17, 2017 shall implement the requirements of ASME BPV Code Case N-729-4 instead of ASME BPV Code Case N-729-1, subject to the conditions specified in paragraphs (g)(6)(ii)(D)(2) through (4) of this section, by the first refueling outage starting after August 17, 2017." ASME Code Case N-729-4 [Reference 18] specifies that the reactor vessel upper head components shall be examined on a frequency in accordance with Table 1 of this Code Case. The basic inspection requirements of Code Case N-729-4 for partial-penetration welded Alloy 690 head penetration nozzles are as follows:

Volumetric/surface examination of all nozzles every ASME Section XI ten-year ISi interval (provided that flaws attributed to PWSCC have not previously been identified in the head) (Item 84.40).
Direct visual examination of the outer surface of the head for evidence of leakage every third refueling outage or 5 calendar years, whichever is less (Item 84.30) .

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Enclosure PG&E Letter DCL-18-057 The Item B4.40 volumetric/surface re-examination interval of ASME Code Case N-729-4 is identical to that of Code Case N-729-1 [Reference 1], which was mandated by the NRC prior to August 17, 2017, by 10 CFR 50.55a(g)(6)(ii)(D). The previous NRC conditions on N-729-1 and the current NRC conditions on N-729-4 in 10 CFR 50 .55a(g)(6)(ii)(D) do not affect the re-examination interval required for Item B4.40.

4. Reason for Request

Treatment of Alloy 690 RVCHs in Code Case N-729-4 was intended to be conservative and subject to reassessment once additional laboratory data and plant experience on the performance of Alloy 690 and Alloys 52/152 weld metals became available [References 2 and 3]. Based on plant and laboratory data, and using appropriate analytical tools, Electric Power Research Institute (EPRI) document Materials Reliability Program (MRP)-375 [Reference 3] was developed to support a technically based volumetric/surface re-examination interval. This technical basis demonstrates that the re-examination interval can be extended through the end of the current operating licenses for DCPP Units 1 and 2 while maintaining an acceptable level of quality and safety. Therefore, Pacific Gas and Electric Company (PG&E) is requesting approval of this alternative to extend the inspection interval for the volumetric/surface examination of the affected DCPP Unit 1 and Unit 2 components.

5. Proposed Alternative and Basis for Use Proposed Alternative Pursuant to 10 CFR 50.55a(z)(1), PG&E requests an alternative from performing the required volumetric/surface examinations for the DCPP Unit 1 and Unit 2 RVCH components identified above on a nominal inspection frequency of ten years as prescribed in Table 1, Item B4.40, of ASME Code, Section XI, Code Case N-729-4.

Specifically, PG&E requests to extend the inspection interval of the volumetric/surface examination of the RVCH components for three fuel cycles for Unit 1 and four fuel cycles for Unit 2 beyond the (nominal) ten calendar years.

For DCPP Unit 1, this request would extend the volumetric/surface examination through the end of the operating license on November 2, 2024. At that point, the Unit 1 RVCH will have been in service for approximately 14.0 calendar years.
For DCPP Unit 2, this request would extend the volumetric/surface examination through the end of the operating license on August 26, 2025. At that point, the Unit 2 RVCH will have been in service for approximately 15.8 calendar years.

Page 3 of 15

Enclosure PG&E Letter DCL-18-057 No alternative examination processes are proposed to those required by ASME Code Case N-729-4, as conditioned by 10 CFR 50.55a(g)(6)(ii)(D). The visual examinations and acceptance criteria as required by Item B4.30 of Table 1 of ASME Code Case N-729-4 are not affected by this request and will continue to be performed on a frequency of every third refueling outage or five calendar years, whichever is less. Basis for Use The original DCPP Unit 1 and Unit 2 RVCHs, which were manufactured with Alloy 600/82/182 materials, were replaced with new RVCHs using Alloy 690/52/152 materials during the refueling outages that ended in November 2010 and November 2009, respectively. In accordance with Table 1 of ASME Code Case N-729-4, Item B4.40, as conditioned by 10 CFR 50 .55a(g)(6)(ii)(D), PG&E is currently required to perform a volumetric/surface examination of essentially 100 percent(%) of the required volume or equivalent surfaces of the nozzle tubes as follows:

For DCPP Unit 1, during the Cycle 22 refueling outage that is scheduled for Fall 2020 (9.9 calendar years following replacement).
For DCPP Unit 2, during the Cycle 21 refueling outage that is scheduled for Fall 2019 (9.9 calendar years following replacement).

The basis for the inspection frequency for ASME Code Case N-729-4 comes, in part, from the analysis of laboratory and plant data presented in report MRP-111 [Reference 4], which was summarized in the safety assessment for RVCHs in MRP-110NP [Reference 5]. The material improvement factor for PWSCC of Alloy 690/52/152 materials over that of mill-annealed Alloys 600 and 182 was shown by this report (MRP-111) to be on the order of 26 or greater. Under an EPRI MRP initiative, further evaluations were performed to demonstrate the resistance of Alloys 690/52/152 to PWSCC and documented in MRP-375. The MRP-375 report combines:

An assessment of the test data and operating experience developed since the technical basis [Reference 2] for the 10-year interval of Case N-729-1 and Case N-729-4 was developed in 2004.
Deterministic and probabilistic evaluations to assess the improved PWSCC resistance of Alloys 690/52/152 relative to Alloys 600/82/182.

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Enclosure PG&E Letter DCL-18-057 Evaluation of Alloys 690/52/152 Data and Experience by MRP-375 Operating experience to date for replacement and repaired components using Alloys 690/52/152 has shown a proven record of resistance to PWSCC during numerous examinations in more than 25 years of its application. This experience includes steam generators, pressurizers, and RVCHs. In particular, at the completion of the Spring 2017 refueling outage season, Alloy 690/52/152 operating experience includes inservice volumetric/surface examinations performed in accordance with ASME Code Case N-729-1 on 16 of the 42 replacement RVCHs currently operating in the United States (U.S.). Some of these examined heads had continuous full power operating temperatures that may approach 613 degrees Fahrenheit (°F). None of these examinations revealed PWSCC, and these examination results further support the low likelihood of the potential for the DCPP RVCHs to experience PWSCC during the extended inspection interval. The evaluation performed in MRP-375 considers a simple Factor of Improvement (FOi) approach applied in a conservative manner to model the increased resistance of Alloys 690/52/152 compared to Alloys 600 and 182 at equivalent temperature and stress conditions. 1 FOls were estimated for the material improvements of Alloy 690/52/152 materials using an extensive database of test data. Results for both crack initiation and crack growth conclude that there is a substantially improved resistance to PWSCC for Alloy 690 base material and Alloy 52/152 weld materials. Figures 3-2, 3-4, and 3-6 of MRP-375 provide crack growth rate data for Alloy 690/52/152 materials and heat affected zones with curves plotting FOls of 1, 5, 10, and 20 on a statistical basis reflecting the material variability exhibited in MRP-55 [Reference 6] for Alloy 600 material and in MRP-115 [Reference 7] for Alloy 82, 182, and 132 weld material. 2 A FOi of 20 bounds most of the data plotted, and a FOi of 10 bounds all of the crack growth rate data. Table 3-6 of MRP-375 provides a summary of FOls determined on the basis of crack growth rate and crack initiation data. As discussed in MRP-375, laboratory and plant data demonstrate a FOi in excess of 13 in terms of the time to PWSCC initiation. Conservatively, credit was not taken for the improved resistance of Alloys 690/52/152 to PWSCC initiation in the MRP-375 analyses. 1 Alloy 600 wrought material is the appropriate reference for defining the FOi for Alloy 690 wrought material. As discussed in Section 3.1 of MRP-375, Alloy 182 weld metal is chosen as the reference for defining the FOi for Alloys 52 and 152 weld metals because Alloy 182 is generally more susceptible to PWSCC initiation and growth than Alloy 82 (due to the higher chromium content of Alloy 82) . 2 As discussed in Section 3.3 of MRP-375, the laboratory crack growth rate data compiled in MRP-375 represent the values reported by individual res~archers, without any adjustment by the authors of MRP-375 other than for temperature and stress intensity factor. The data presented in Figures 3-2, 3-4, and 3-6 of MRP-375 represent essentially the entire set of data points reported by the various laboratories. No screening process was applied to the data on the basis of test characteristics such as minimum required crack extension or minimum required engagement to intergranular cracking. Instead, an inclusive process was applied to conservatively assess the FOls apparent in the data for specimens with less than 10% added cold work. Page 5 of 15

Enclosure PG&E Letter DCL-18-057 Additional Evaluations Performed under MRP-375 MRP-375 applied the FOi results to perform a combination of deterministic and probabilistic evaluations to establish an appropriately conservative inspection interval for Alloy 690 RVCHs. The deterministic technical basis applies industry-standard crack growth calculation procedures to predict time to certain adverse conditions under various conservative assumptions. A probabilistic evaluation is then applied to make predictions for leakage and ejection risk, generally using best-estimate inputs and assumptions, with uncertainties treated using statistical distributions. The deterministic crack growth evaluation provides a precursor to the probabilistic evaluation to directly illustrate the relationship between the improved PWSCC growth resistance of Alloys 690/52/152 and the time to certain adverse conditions. These evaluations apply conservative crack growth rate predictions and the assumption of an existing flaw, which is replaced with a PWSCC initiation model for probabilistic evaluation. These evaluations provide a reasonable lower bound on the time to adverse conditions, from which a conservative inspection interval may be recommended. These evaluations draw from various EPRI MRP and industry documents that evaluate, for Alloys 600/82/182, the time from a detectable flaw being created to leakage occurring and from a leaking flaw to the time that net section collapse (nozzle ejection) would be predicted to occur. Applying a conservative crack growth FOi of 20 to circumferential and inside diameter (ID) axial cracking and a FOi of 10 to outside diameter (OD) axial cracking for Alloy 690 versus Alloy 600, the results show that more than 20 years is required for leakage to occur and that more than 120 years would be required to reach the critical crack size subsequent to leakage. The probabilistic model in MRP-375 was developed to predict PWSCC degradation and its associated risks in RVCHs. The model utilized in this probabilistic evaluation is modified from the model presented in Appendix B of MRP-335, Revision 1 [Reference 8], which evaluated surface stress improvement of RVCHs with Alloy 600 nozzles. The integrated probabilistic model in MRP-375 includes sub-models for simulating component and crack stress conditions, PWSCC initiation, PWSCC growth, and flaw examination. The sub-models for crack initiation and growth prediction for Alloy 600 reactor pressure vessel head penetration nozzles in MRP-335, Revision 1, were adapted for RVCHs with Alloy 690 nozzles by applying FOls to account for the superior PWSCC resistance of Alloys 690/52/152. The average leakage frequency and average ejection frequency were determined using the Monte Carlo simulation model with conservative FOi assumptions. The results show that, even using conservatively small FOls for Alloys 690/52/152, the potential for developing a safety significant flaw (risk of nozzle ejection) is acceptably low for a volumetric/surface examination period up to 40 years. Page 6 of 15

Enclosure PG&E Letter DCL-18-057 The evaluations performed in MRP-375 were prepared to bound all Pressurized Water Reactor (PWR) replacement RVCH designs that are manufactured using Alloy 690 base material and Alloy 52/152 weld materials. The evaluations assume a continuous operating RVCH temperature of 613°F and a relatively large number of RVCH penetrations (89). The number of penetrations included in the probabilistic model is not a key variable, and the assumed number of penetrations results in a small change in results relative to other sensitivity cases. Thus, the probabilistic calculations of MRP-375 cover all U.S. replacement RVCHs regardless of the precise number of penetrations. While approval of this PG&E request for alternative is not contingent on U.S. Nuclear Regulatory Commission (NRG) review and approval of MRP-375, the insights gained in this technical report help substantiate the limited extension duration being requested. In particular, the tabulation of crack growth rate data for Alloys 690/52/152 (Section 3 of MRP-375) and review of inspection experience for Alloy 690/52/152 plant components (Section 2 of MRP-375) are sufficient to demonstrate the acceptability of the limited extension duration being requested. This request is not dependent on the more detailed probabilistic calculations presented in Section 4 of MRP-375. Reactor Vessel Closure Head (RVCH) Design and Operation The analysis presented in MRP-375 was intended to cover all replacement RVCHs in U.S. PWRs, including the DCPP Unit 1 and Unit 2 RVCHs. The MRP-375 analyses assume a reactor vessel head operating temperature of 613°F to bound the known reactor vessel head temperatures of all U.S. PWRs currently operating. RVCH operating temperature considerations for DCPP are as follows:

For DCPP Unit 1, the RVCH operating temperature since installation of the replacement head in 2010 is 589.1 °F [Reference 9]. 3
For DCPP Unit 2, the RVCH operating temperature since installation of the replacement head in 2009 is 545.1 °F. For Unit 2, the RVCH temperature is lower due to upper head temperature reduction modifications that were implemented prior to installation of the replacement RVCH [Reference 17]. 4 These temperatures are applicable until the end of the requested volumetric/surface inspection period.

3 The DCPP Unit 1 RVCH operating temperature cited from MRP-48 [Reference 9] was developed by Westinghouse in support of evaluations of the original Alloy 600 RVCH nozzles, but continues to be representative of current plant operation. 4 DCPP Unit 2 upper head temperature reduction modifications were completed by Westinghouse in 2005 prior to initial installation of the replacement RVCH in 2009. The post-modification operating temperature, as stated in WCAP-16487-P, remains current for Unit 2. Page 7 of 15

Enclosure PG&E Letter OCL-18-057 Based on the above , the OCPP Unit 1 and Unit 2 RVCH average operating temperatures are bounded by the MRP-375 evaluation , which assumes 613°F for its main deterministic and probabilistic calculations. The average RVCH operating temperature is a measure for potential PWSCC degradation. The OCPP Unit 1 and Unit 2 RVCHs each contain 60 nozzle penetrations, of which 53 are used for control rod drive mechanisms (CROM), five are used for in-core thermocouples, and two are small-diameter penetrations near the center of the RVCH used for vent and RVLIS pipes. The replacement RVCHs were manufactured by AREVA NP, Inc., and placed in service in November 2010 for Unit 1 and November 2009 for Unit 2. The replacement RVCHs were manufactured as single forgings, which eliminated all circumferential and meridional welds in the original RVCHs. The replacement RVCHs are fabricated from SA-508 , Grade 3, Class 1 low-alloy steel and clad with SA-240, Type 304 (E308L/E309). The CROM and thermocouple nozzle penetrations are fabricated from SB-167 (Alloy 690) UNS N06690. The small diameter vent and RVLIS connections on the replacement RVCHs are fabricated from SB-166 (Alloy 690) UNS N06690. The penetration nozzle J-groove welds utilized ERNiCrFe-7 (UNS N06052) and ENiCrFe-7 (UNS W86152) weld materials. RVCH - Preservice Volumetric Examinations Preservice volumetric examinations of the OCPP Unit 1 and Unit 2 replacement RVCH partial-penetration welded nozzles were performed using eddy current (ET) and ultrasonic (UT) examination techniques. The volumetric examinations included scanning the nozzles to the fullest extent possible, from the end of the nozzle to a minimum of 2 inches above the root of the J-groove weld on the uphill side. No recordable ET or UT indications were found in any of the penetrations or welds. RVCH - Bare Metal Visual Examinations Bare metal visual examinations were performed on the OCPP Unit 1 replacement RVCH in 2015, and on the Unit 2 replacement RVCH in 2014, in accordance with ASME Code Case N-729-1, Table 1, Item B4.30. The visual examinations were performed on the outer surface of the RVCHs including the annulus area of the penetration nozzles by VT-2 qualified visual testing examiners. The examinations did not detect any boric acid indications on the surface or on the nozzle penetration that would be indicative of nozzle leakage. These examinations will be performed again in the Unit 1 Cycle 22 refueling outage scheduled for fall 2020 and the Unit 2 Cycle 21 and Cycle 24 refueling outages scheduled for fall 2019 and (tentatively) fall 2024, respectively. Page 8 of 15

Enclosure PG&E Letter DCL-18-057 Minimum Factor of Improvement (FOi) implied by Requested Inspection Period ASME Code Case N-729-4 is based upon conclusions reached [Reference 10] that a re-examination interval between volumetric/surface examinations of one 24-month operating cycle is acceptable for a head with Alloy 600 nozzles and operating at a temperature of 605°F. The inspection period for heads with Alloy 690 nozzles in Case N-729-4 is a nominal 10 years, which represents a minimum implied FOi of 5 over Alloy 600. FOi Approach Per the technical basis documents for ASME Code Case N-729-4 for heads with Alloy 600 nozzles [References 5, 10, and 11 ], the effect of differences in operating temperature on the required volumetric/surface re-examination interval for heads with Alloy 600 nozzles can be addressed on the basis of the Re-Inspection Years (RIY) parameter. The RIY parameter adjusts the effective full power years (EFPYs) of operation between inspections for the effect of head operating temperature using the thermal activation energy appropriate to PWSCC crack growth. For heads with Alloy 600 nozzles, ASME Code Case N-729-4 as conditioned by 10 CFR 50.55a(g)(6)(ii)(D) limits the interval between subsequent volumetric/surface inspections to RIY = 2.25. The RIY parameter, which is referenced to a head temperature of 600°F, limits the time available for potential crack growth between inspections. The RIY parameter for heads with Alloy 600 nozzles is adjusted to the reference head temperature using an activation energy of 130 kilojoules per mole (kJ/mol) [31 kilocalories per mole (kcal/mol)] [References 1 and 18]. Based on the available laboratory data, the same activation energy is applicable to model the temperature sensitivity of growth of a hypothetical PWSCC flaw in the Alloy 690/52/152 material of the replacement RVCH. Key laboratory crack growth rate testing data for Alloy 690 wrought material investigating the effect of temperature are as follows: (1) Results from Argonne National Laboratory (ANL) reported in NUREG/CR-7137 [Reference 12] indicate that Alloy 690 with 0-26% cold work has an activation energy value between 100 and 165 kJ/mol (24-39 kcal/mol). NUREG/CR-7137 concludes that the activation energy for Alloy 690 is comparable to the standard value for Alloy 600 (130 kJ/mol). (2) Testing at Pacific Northwest National Laboratory (PNNL) found an activation energy value of about 120 kJ/mol (28.7 kcal/mol) for Alloy 690 materials with 17-31 % cold work [Reference 13]. (3) Additional PNNL testing determined an activation energy value of 123 kJ/mol (29.4 kcal/mol) for Alloy 690 with 31% cold work [Reference 14]. Page 9 of 15

Enclosure PG&E Letter DC L-18-05 7 These data show that it is reasonable to assume the same crack growth thermal activation energy as was determined for Alloys 600/82/182, namely 130 kJ/mol (31 kcal/mo!), for modeling growth of hypothetical PWSCC flaws in Alloys 690/52/152 PWR plant components. As discussed in the MRP-117 technical basis document for RVCHs with Alloy 600 nozzles, effective time for crack growth is the principal basis for setting the appropriate re-examination interval to detect any PWSCC in a timely fashion. U.S. PWR inspection experience for heads with Alloy 600 nozzles has confirmed that the RIY = 2.25 interval results in a suitably conservative inspection program . There have been no reports of nozzle leakage or of safety-significant circumferential cracking subsequent to the time that the Alloy 600 nozzles in a head were first examined by nonvisual inservice nondestructive examination [References 15 and 16]. FOi Implied by Requested Inspection Period for DCPP Unit 1 and Unit 2 PG&E has assessed the minimum Alloy 690/52/152 FOi that supports the requested DCPP Unit '1 and Unit 2 extension periods for comparison with the laboratory crack growth rate data presented in MRP-375. Based on the previously stated conclusion that a re-examination interval between volumetric/surface examinations of one 24-month operating cycle is acceptable for a head with Alloy 600 nozzles and operating at a temperature of 605°F, an extension of the DCPP examination interval to 16 years 5 would imply a factor of 16/2 or 8.0 for Alloys 690/52/152 relative to Alloys 600 and 182 for the proposed volumetric/surface examination interval extension if the heads operated at a temperature of 605°F. The RIY parameter for the requested examination interval is compared with the N-729-4 interval for Alloy 600 nozzles of RIY = 2.25, to calculate the minimum implied FOi for the Unit 1 RVCH operating temperature of 589.1 °F and the Unit 2 RVCH operating temperature of 545.1 °F. 5 The nominal interval of 16 years was selected by conservatively adding four 18-month fuel cycles to the nominal inspection interval of 10 years. The actual proposed intervals between RVCH installation and the end of license for DCPP Unit 1 and Unit 2 are 14.0 and 15.8 calendar years, respectively . The projected EFPYs at the end of the proposed RVCH inspection intervals for DCPP Unit 1 and Unit 2 are 14.0 and 15.8 FPYs, respectively. No examinations are proposed at the end of the proposed intervals, which correspond with the ends of the operating licenses. Page 10 of 15

Enclosure PG&E Letter DCL-18-057 As discussed previously, it is appropriate to apply this standard activation energy of 130 kJ/mol (31 kcal/mol) for modeling of crack growth rate in Alloy 690/52/152 plant components. The representative DCPP Unit 1 RVCH operating temperature of 589.1 °F corresponds to a temperature adjustment factor of 0.759 (versus the reference temperature of 600°F), and the Unit 2 RVCH operating temperature of 545.1 °F corresponds to a temperature adjustment factor of 0.235 (versus the reference temperature of 600°F). Conservatively assuming that the EFPYs of operation accumulated at DCPP Unit 1 and Unit 2 since RVCH replacement is equal to the calendar years since replacement, the RIY for the requested extended period for DCPP Unit 1 would be (0.759 temperature factor for growth rate) x (14.0 total calendar years for extended interval) = 10.63 RIY. As a result of this temperature adjustment factor, the implied FOi for DCPP Unit 1 would be (0 .759 temperature adjustment factor for crack growth rate) x (14.0 total calendar years for extended interval) /2.25 = 4.72. Similarly, the implied FOi for Unit 2 would be (0.235 temperature adjustment factor for crack growth rate) x (15.8 total calendar years for extended interval) /2.25 =1.65. Consequently, 4.72 is used as a bounding FOi for both units. This FOi of 4.72 is conservatively less than the FOi of 10 that statistically bounds the crack growth rate data presented in Figures 3-2, 3-4, and 3-6 of MRP-375. Furthermore, as discussed in Sections 2 and 3 of MRP-375, PWR plant experience and laboratory testing have demonstrated a large improvement in resistance to PWSCC initiation of Alloys 690/52/152 in comparison to that for Alloys 600/82/182. Therefore, the demonstrated improvements in PWSCC initiation and growth confirm, on a conservative basis, the acceptability of the limited requested period of extension. The attachment to this Enclosure, prepared by Dominion Engineering for EPRI, provides further support for the requested alternative inspection interval based on the available laboratory PWSCC crack growth rate data and the FOi approach. describes the materials tested for data points within a factor of 12 below the MRP-55 and MRP-115 crack growth rate curves for the 75th percentile of material variability. The FOi value of 4.72 associated with the proposed alternative for the DCPP replacement heads is conservatively smaller than this FOi of 12. The test materials discussed in Attachment 1 correspond to the materials used to fabricate the DCPP replacement heads. It is concluded that the available crack growth rate data do not indicate any susceptibility concerns specific to the nozzle or weld materials of the DCPP replacement heads. Page 11 of 15

Enclosure PG&E Letter DCL-18-057 Conclusions PG&E concludes that the Alloy 690 nozzle base and Alloy 52/152 weld materials used in the DCPP Unit 1 and Unit 2 replacement RVCHs provide for a superior RCS pressure boundary, for which the potential for PWSCC has been shown by analysis and by years of positive industry experience to be remote. This conclusion is further supported by direct visual examination of the DCPP Unit 1 replacement RVCH in 2015, direct visual examination of the Unit 2 replacement RVCH in 2014 and the lack of PWSCC detected in the volumetric examinations performed to date of Alloy 690 nozzles in similar replacement RVCHs. The minimum FOi of 4.72 implied by the requested extension period for DCPP represents a level of reduction in PWSCC crack growth rate versus that for Alloys 600/82/182 that is completely bounded on a statistical basis by the laboratory data compiled in MRP-375 and Attachment 1. The lack of PWSCC detected to date in any PWR plant applications of Alloys 690/52/152 and the results of the FOi assessment support the requested period of extension. Therefore, the requested periods of extension to perform volumetric/surface examinations of the DCPP Unit 1 and Unit 2 RVCH nozzles provide an acceptable level of quality and safety in accordance with 10 CFR 50 .55a(z)(1 ).

6. Duration of Proposed Alternative The proposed alternative is requested:

For DCPP Unit 1, for the duration of the fourth ISi interval up to and including the end of the operating license on November 2, 2024.
For DCPP Unit 2, for the duration of the fourth ISi interval up to and including the end of the operating license on August 26, 2025.

Page 12 of 15

Enclosure PG&E Letter DCL-18-057

7. Precedents NRG has previously approved submittals from multiple plants that requested an alternative from the frequency of ASME Code Case N-729-1 and N-729-4 for volumetric/surface examinations of heads with Alloy 690 nozzles. Examples of these plant requests and NRG authorizations are identified below:

NRC ADAMS Accession No. Plant Request for Status NRC Safety Relief Request Additional RAI Response Evaluation Information (RAI) Arkansas Nuclear ML14118A477 ML14258A020 ML14275A460 ML14330A207 Approved One, Unit 1 Arkansas Nuclear ML16173A297 None None ML17018A283 Approved One, Unit 1 Beaver Valley, ML14290A140 None None ML14363A409 Approved Unit 1 Beaver Valley, ML17044A440 None None ML17222A162 Approved Unit 1 Calvert Cliffs, ML15201A067 None None ML15327A367 Approved Units 1 & 2 Comanche Peak, ML15120A038 None None ML15259A004 Approved Unit 1 D.C. Cook, ML15023A038 None None ML15156A906 Approved Units 1 & 2 D.C. Cook, ML18075A329 None None ML18103A059 Approved Units 1 & 2 J.M. Farley, ML15111A387 None None ML15104A192 Approved Unit 2 North Anna, ML14283A044 None None ML15091A687 Approved Unit 2 Prairie Island, ML14258A124 ML15030A008 ML15036A252 ML15125A361 Approved Units 1 and 2 Palo Verde, ML17101A678 None None ML17306B432 Approved Units 1, 2, and 3 H.B. Robinson, ML14251A014 ML14294A587 ML14325A693 ML15021A354 Approved Unit 2 H.B. Robinson, ML17269A016 None None ML18163A412 Approved Unit 2 Salem, ML15098A426 None None ML15349A956 Approved Unit 1 St. Lucie, ML14206A939 ML14251A222 ML14273A011 ML14339A163 Approved Unit 1 St. Lucie, ML17045A357 None None ML17219A174 Approved Unit 1 St. Lucie, ML16076A431 None None ML16292A761 Approved Unit 2 Page 13 of 15

Enclosure PG&E Letter DCL-18-057

8. References

1. ASME Code Case N-729-1, "Alternative Examination Requirements for PWR Reactor Vessel Upper Heads With Nozzles Having Pressure-Retaining Partial-Penetration Welds," Section XI, Division 1, approved March 28, 2006 [Agencywide Documents Access and Management System (ADAMS) Accession No. ML070170679]

2. ASME Section XI, Code Case N-729, "Technical Basis Document," dated September 14, 2004

3. Materials Reliability Program: Technical Basis for Reexamination Interval Extension for Alloy 690 PWR Reactor Vessel Top Head Penetration Nozzles (MRP-375). EPRI, Palo Alto, CA: February 2014

4. Materials Reliability Program: Resistance to Primary Water Stress Corrosion Cracking of Alloys 690, 52, and 152 in Pressurized Water Reactors (MRP-111). EPRI, Palo Alto, CA: March 2004 [ADAMS Accession No. ML041680546]

5. Materials Reliability Program: Reactor Vessel Closure Head Penetration Safety Assessment for U.S. PWR Plants (MRP-110NP). EPRI, Palo Alto, CA: April 2004

[ADAMS Accession No. ML041680506]

6. Materials Reliability Program (MRP): Crack Growth Rates for Evaluating Primary Water Stress Corrosion Cracking (PWSCC) of Thick-Wall Alloy 600 Materials (MRP-55, Revision 1). EPRI, Palo Alto, CA: November 2002

7. Materials Reliability Program: Crack Growth Rates for Evaluating Primary* Water Stress Corrosion Cracking (PWSCC) of Alloy 82, 182, and 132 Welds (MRP-115).

EPRI, Palo Alto, CA: November 2004

8. Materials Reliability Program: Topical Report for Primary Water Stress Corrosion Cracking Mitigation by Surface Stress Improvement (MRP-335, Revision 1). EPRI, Palo Alto, CA: January 2013

9. PWR Materials Reliability Program: Response to NRC Bulletin 2001-01 (MRP-48).

EPRI, Palo Alto, CA: August 2001

10. Materials Reliability Program: Inspection Plan for Reactor Vessel Closure Head Penetrations in U.S. PWR Plants (MRP-117). EPRI, Palo Alto, CA: December 2004

[ADAMS Accession No. ML043570129]

11. Materials Reliability Program: Probabilistic Fracture Mechanics Analysis of PWR Reactor Pressure Vessel Top Head Nozzle Cracking (MRP-105 NP). EPRI, Palo Alto, CA: April 2004 [ADAMS Accession No. ML041680489]

Page 14 of 15

Enclosure PG&E Letter DCL-18-057

12. U.S. NRG, "Stress Corrosion Cracking in Nickel-Base Alloys 690 and 152 Weld in Simulated PWR Environment- 2009," NUREG/CR-7137, ANL-10/36: June 2012

[ADAMS Accession No. ML12199A415]

13. Materials Reliability Program: Resistance of Alloys 690, 152, and 52 to Primary Water Stress Corrosion Cracking (MRP-237, Rev.2): Summary of Findings between 2008 and 2012 from Completed and Ongoing Test Programs. EPRI, Palo Alto, CA: April 2013

14. M.B. Toloczko, M.J. Olszta, and S.M . Bruemmer, "One Dimensional Cold Rolling Effects on Stress Corrosion Crack Growth in Alloy 690 Tubing and Plate Materials," 15th International Conference on Environmental Degradation of Materials in Nuclear Power Systems - Water Reactors, TMS (The Minerals, Metals & Materials Society): 2011

15. EPRI Letter MRP 2011-034, "Tcold RV Closure Head Nozzle Inspection Impact Assessment," December 21, 2011 [ADAMS Accession No. ML12009A042]

16. G. White, V. Moroney, and C. Harrington, "PWR Reactor Vessel Top Head Alloy 600 CROM Nozzle Inspection Experience," presented at EPRI International BWR and PWR Material Reliability Conference, National Harbor, Maryland, July 19, 2012

17. WCAP-16487-P, "Diablo Canyon Nuclear Plant Unit 2 Upflow Conversion and Upper Head Temperature Reduction Engineering Report," Westinghouse Electric Corp.,

October 2005

18. ASME Code Case N-729-4, "Alternative Examination Requirements for PWR Reactor Vessel Upper Heads With Nozzles Having Pressure-Retaining Partial-Penetration Welds," Section XI, Division 1, approved June 22, 2012 Page 15 of 15

Attachment PG&E Letter DCL-18-057 Dominion Engineering Report Assessment of Laboratory PWSCC Crack Growth Rate Data Compiled for Alloys 690, 52, and 152 with Regard to Factors of Improvement (FOi) versus Alloys 600 and 182 TN-5696-00-02 Revision 0 March 2015

Dominion fn~ineerin:,1/ TECHNICAL NOTE Assessment of Laboratory PWSCC Crack Growth Rate Data Compiled for Alloys 690, 52, and 152 with Regard to Factors of Improvement (FOi) versus Alloys 600 and 182 TN-5696-00-02 Revision 0 March 2015 Principal Investigators G. White K. Fuhr Prepared for Electric Power Research Institute, Inc. 3420 Hillview Avenue Palo Alto, CA 94303-1338 12100 Sunrise Valley Drive, Suite 220

Reston, VA 20191
PH 703.657.7300
FX 703.657.7301

Dominion fn~ineerin~, Inc. TN-5696-00-02, Rev. 0 RECORD OF REVISIONS Prepared by Checked by Reviewed by Approved by Rev. Description Date Date Date Date 0 Original Issue 3(~

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K. J. Fuhr M. Burkard! G. A. White G. A. White Associate Engineer , Associate Engineer Principal Engineer Principal Engineer The last revision number to reflect any changes for each section of the technical note is shown in the Table of Contents. The last revision numbers to reflect any changes for tables and figures are shown in the List of Tables and the List of Figures. Changes made in the latest revision, except for Rev. 0 and revisions which change the teclmical note in its entirety, are indicated by a double line in the right hand margin as shown here. ii

Dominion fn~ineerin~, Inc. TN-5696-00-02, Rev. 0 CONTENTS Last Rev. Page Mod. 1 INTRODUCTION .. ........ ........ .... ... .. ... .... ....... ................................................ ... ..... .... ....... ...... 1 0 2 DISCUSSION OF DATA POINTS FROM MRP-375 [2] .......................... .. .......... .................... 3 0 2.1 Data Points Above a Hypothetical 12.0 Factor of Improvement Line in Figure 3-1, 3-3, and 3-5 of MRP-375 .......................................... ........................... 3 0 2.2 Data Most Directly Applicable to Plant Conditions .. ................ ..................... .......... 6 0 2.3 Data Specific to Argonne National Laboratory (ANL) and Pacific Northwest National Laboratory (PNNL) .......... ................................................... .... 8 0 2.4 Data for Alloy 690 Wrought Material Including Added Cold Work up to 20% for CROM Nozzle and Bar Material Product Forms ....................................... 8 0 2.5 Conclusion .. ................................ ........ ....................... ..... ..... .. ................ ............... 9 0 3 POTENTIAL IMPLICATIONS OF SPECIFIC CATEGORIES OF NOZZLE AND WELD MATE RIALS .... ... ..... .. .... .... ... ... ....... .. ... .............................. ......... ......... .... ... .... ...... .... .. ...... ... 9 0 3.1 Potential Similarities for Laboratory Specimen Material Exhibiting a Deterministic Factor Less than 12.0 ......................................................... ............. 9 0 3.2 Potential Implications .. ........... ........................................... ........... .. ..................... 10 0 4 REFERENCES ..... ............................................. .................. .. ............. .. ...... .... ..... .. .. .. ..... ..... 12 0 iii

Dominion fn~ineerin~, Inc. TN-5696-00-02, Rev. 0 LIST OF FIGURES Last Rev. Page Mod. Figure 1. Plot of Crack Growth Rate (da/dt) versus Stress Intensity Factor (K1) for Alloy 690 Data from Plate Material Tested by CIEMAT.. ..... .. .... .. .... ... .... .... .. .. ... .... .... .. 14 0 Figure 2. Plot of da/dt versus K1 for Alloy 690 Data from Heat WP787 .. .. .. ....... .......... ....... 14 0 Figure 3. Plot of da/dt versus K1 for Alloy 690 Data from Heat WP142 .... .. .. ... .. ................. 15 0 Figure 4. Plot of da/dt versus K1 for Alloy 690 HAZ Data from Heat WP 142 .... .. ................ 15 0 Figure 5. Plot of da/dt versus K1 for Alloy 690 HAZ Data from Plate Material Tested by CIEMAT .... .. ....... .. ... ...... .. ............ ........ .. ... .. ................. .......... ................ .. ............ 16 0 Figure 6. Plot of da/dt versus K1 for Alloy 152 Data from Heat WC83F8 .... .. .. .. .................. 16 0 Figure 7. Plot of da/dt versus K1 for Alloy 152 Data from Heat WC04F6 ...... .. .... ...... .. .. ...... 17 0 Figure 8. Plot of da/dt versus K1 for Alloy 690 Data from All Laboratories, ::;; 10% Cold Work, Constant Load or K1 ................ .. ........ .. ...... .... .. .. .. .. ................ ...... .. .. .... .... .. 18 0 Figure 9. Cumulative Distribution Function of Adjusted da/dt for Alloy 690 Data from All Laboratories, ::;; 10% Cold Work, Constant Load or K1 .. .... .. .............. .. ........... 18 0 Figure 10. Plot of da/dt versus K1 for Alloy 690 HAZ Data from All Laboratories, :5 10% Cold Work, Constant Load or K1 .................................. .. .......... ... .. .............. .. ... ... 19 0 Figure 11. Cumulative Distribution Function of Adjusted da/dt for Alloy 690 HAZ Data from All Laboratories, :5 10% Cold Work, Constant Load or K1 .............. .. ........... 19 0 Figure 12. Plot of da/dt versus K1 for Alloy 52/152 Data from All Laboratories, ::;; 10% Cold Work, Constant Load or K1 .... .. ........ .. .. .. .... .. .. .. ...... ... ............... .. .. .. ... .. ........ 20 0 Figure 13. Cumulative Distribution Function of Adjusted da/dt for Alloy 52/152 Data from All Laboratories, ::;; 10% Cold Work, Constant Load or K1 .. ...... .. .... .. ........... 20 0 Figure 14. Plot of da/dt versus Loading Hold Time (for PPU testing) or Test Segment Duration (for Constant Ki/Load Testing) from Heat WP787 ........ ...... .. ................ 21 0 Figure 15. Plot of da/dt versus K1 for Alloy 690 Data Produced by ANL and PNNL and Available in Reference [17]; ::;; 22% Cold Work ...................... ............................. 22 0 Figure 16. Cumulative Distribution Function of Adjusted da/dt Alloy 690 Data Produced by ANL and PNNL in References [17]; ::;; 22% Cold Work and Constant Load/Ki ............ ... .. ..... .. .. .... ............ .................. .. ...................................... .... ...... .22 0 Figure 17. Plot of da/dt versus K1 for Alloy 690 HAZ Data Produced by ANL and PNNL and Available in Reference [17];::;; 22% Cold Work .............. .. ... ...... .. .. .. ............. 23 0 Figure 18. Cumulative Distribution Function of Adjusted da/dt Alloy 690 HAZ Data Produced by ANL and PNNL [17];::;; 22% Cold Work and Constant Load/Ki ...... 23 0 Figure 19. Plot of da/dt versus K1 for Alloy 52/152 Data Produced by ANL and PNNL iv

Dominion fn~ineerin~, Inc. TN-5696-00-02, Rev. 0 Last Rev. Page Mod. and Available in References [17] and [18];::;; 22% Cold Work ............................ 24 0 Figure 20. Cumulative Distribution Function of Adjusted da/dt Alloy 52/152 Data Produced by ANL and PNNL ([17] and [18]);::;; 22% Cold Work and Constant Load/Ki .............. ...... .......................................... ................ .... .. ...........................24 0 Figure 21 . Plot of da/dt versus K1 for Alloy 690 Data from All Laboratories, > 10 & ::;; 20% Cold Work, CROM and Bar Material, Constant Load or K1 Testing .. .... .... .. .25 0 Figure 22. Cumulative Distribution Function of Adjusted da/dt Alloy 690 Data from All Labs,::;; 20% Cold Work, CROM and Bar Material, Constant Load or K1 .. .......... 25 0 Figure 23. Plot of da/dt versus K1 for Alloy 52/152 Data from All Laboratories, > 10 & ::;; 20% Cold Work, Constant Load or K1 .. .......... .. ........ .. ............... .. ........................ 26 0 Figure 24. Cumulative Distribution Function of Adjusted da/dt Alloy 52/152 Data from All Laboratories,::;; 20% Cold Work, Constant Load or Ki .......................... .............. 26 0 V

Dominion fn~ineerin~, Inc. TN-5696-00-02, Rev. 0 ACRONYMS ANL Argonne National Laboratory ASME American Society of Mechanical Engineers AWS American Welding Society BWC Babcock & Wilcox Canada CEDM Control Element Drive Mechanism CGR Crack Growth Rate CIEMAT Centro de Investigaciones Energeticas, Medioambientales y Tecnol6gicas CRDM Control Rod Drive Mechanism CT Compact Tension DEi Dominion Engineering, Inc. EPRI Electric Power Research Institute FOI Factor of Improvement GE-GRC General Electric Global Research Center GTAW Gas Tungsten Arc Welding HAZ Heat Affected Zone ICI In-Core Instrumentation K Stress Intensity Factor MRP Materials Reliability Program NRC Nuclear Regulatory Commission PNNL Pacific Northwest National Laboratory PPU Partial Periodic Unloading PWR Pressurized Water Reactor PWSCC Primary Water Stress Corrosion Cracking RIY Re-Inspection Year RV Reactor Vessel RVCH Reactor Pressure Closure Head UNS Unified Numbering System vi

Dominion fn~ineerin~, Inc. TN-5696-00-02, Rev. 0 1 INTRODUCTION The purpose of this DEI technical note is to examine laboratory crack growth rate (CGR) data for primary water stress corrosion cracking (PWSCC) compiled for Alloys 690, 52, and 152 to assess factors of improvement (FOI) for these replacement alloys relative to the CGR behavior for Alloys 600 and 182 as documented in MRP-55 [1] and MRP-115 [2] . In addition, an assessment is made of the available laboratory CGR data for the potential concern of elevated CGRs for specific categories of nozzle and weld materials. Per ASME Code Case N-729-1 [3], the volumtric inspection interval for Alloy 600 RV head nozzles is based on operating time adjusted for operating temperature using the temperature sensitivity for PWSCC crack growth. The normalized operating time between inspections, called the Re-Inspection Years (RIY) parameter, represents the potential for crack growth between successive volumtric examinations. Thus, the FOI for Alloys 690/52/152 exhibited by laboratory CGR data can be used to support appropriate volumetric inspection intervals for RV heads with Alloy 690 nozzles. On the basis of the RIY = 2.25 limit of Code Case N-729-1 for Alloy 600 RV head nozzles, an FOI of 12 corresponds to an inspection interval of 20 years for Alloy 690 RV head nozzles operating at 613 °F. 1 A temperature of 613 °F is expected to bound the head operating temperature for the U.S. pressurized water reactor (PWR) fleet. As discussed in Section 3 of Electric Power Research Institute (EPRI) Materials Reliability Program (MRP) report MRP-375 [2] , a conservative approach was taken in MRP-375 to develop the factor of improvement (FOI) values describing the primary water stress corrosion cracking (PWSCC) crack growth rates applicable to Alloy 690 reactor vessel (RV) top head penetration nozzles. The crack growth rate data points presented in Figures 3-1, 3-3, and 3-5 ofMRP-375 represent the values reported by individual researchers, without any adjustment by the authors of MRP-375 other than to normalize for the effect of temperature. The data in these figures represent essentially all of the Alloys 690, 52, and 152 data points reported by the various 1 To calculate the implied FOI for the bounding RV top head operating temperature of613 °F, the re-inspection year (RIY) parameter for a requested examination interval of20 years is compared with the N-729-1 interval for Alloy 600 nozzles ofRIY = 2.25. The representative head operating temperatures of613 °F corresponds to an RIY temperature adjustment factor of 1.38 (versus the reference temperature of 600°F) using the activation energy of 31 kcal/mo! (130 kJ/mol) for crack growth of ASME Code Case N-729-1. Conservatively assuming that the effective full power years (EFPY) of operation accumulated since RV top head replacement is equal to 98% of the calendar years since replacement, the RIY for a requested extended period of20 years would be (1.38)(19.6) = 27.0. The FOI implied by this RIY value is (27.0)/(2.25) = 12.0.

Dominion fn~ineerin~, Inc. TN-5696-00-02, Rev. 0 laboratories. No screening process was applied to the data on the basis of test characteristics such as minimum required crack extension or minimum required extent of transition along the crack front to intergranular cracking. Instead, an inclusive process was applied to conservatively assess the factors of improvement apparent in the data for specimens with less than 10 percent added cold work. The approach was conservative in that no effort was made to screen out data points reflecting tests that are not applicable to plant conditions. Instead, the data were treated on a statistical basis in Figures 3-2, 3-4, and 3-6 ofMRP-375, 2 and compared to the crack growth rate variability due to material variability for Alloy 600 in MRP-55 [1] and Alloy 182 in MRP-115 [2]. A comparison between the cumulative distributions of the crack growth rates for Alloys 690/52/152 and Alloys 600/82/182 treats the full variability in both original and replacement alloys, rather than comparing the variability of the replacement alloy against a conservative mean (7 5th percentile) growth rate for the original alloys. By considering the cumulative distributions, a fuller perspective of the improved resistance of Alloys 690/52/152 emerges where over 70% of the data in each of Figures 3-2, 3-4, and 3-6 ofMRP-375 indicate a factor of improvement beyond 20 and all of the data 3 correspond to a factor of improvement of 12 or greater. It is emphasized that the deterministic MRP-55 and MRP-115 crack growth rate equations were developed not to describe bounding crack growth rate behavior but rather reflect 75 th percentile values of the variability in crack growth rate due to material variability. Twenty-five percent of the material heats (MRP-55) and test welds (MRP-115) assessed in these reports on average showed crack growth rates exceeding the deterministic equation values. Thus, the most appropriate FOI comparisons are made on a statistical basis (e.g., Figures 3-2, 3-4, and 3-6 of MRP-375). Comparing the crack growth rate for Alloys 690/52/152 versus the deterministic crack growth rate lines in Figures 3-1, 3-3, and 3-5 ofMRP-375 represents an unnecessary compounding of conservatisms. Essentially none of the data presented lies within a statistical FOI of 12 below the MRP-55 and MRP-115 distributions of material variability. The technical basis for the inspection requirements for heads with Alloy 600 nozzles ([5], [6], [7]) are based on the full range of crack growth rate behavior, including heat-to-heat (weld-to-weld) and within-heat (within-weld) material variability factors. Thus, the Re-Inspection Year (RIY) = 2.25 inspection interval developed for heads with Alloy 600 nozzles reflects the possibility of crack 2 Figures 3-2, 3-4, and 3-6 ofMRP-375 show cumulative distribution functions of the variability in crack growth rate normalized for temperature and crack loading (i.e., stress intensity factor). Each ordinate value in the plots shows the fraction of data falling below the corresponding normalized crack growth rate. Thus, the cumulative distribution function has the benefit of illustrating the variability in crack growth rate data for a standard set of conditions. 3 Excluding data points that reflect fatigue pre-cracking conditions and are not relevant to PWSCC. 2

Dominion fn~ineerin~, Inc. TN-5696-00-02, Rev. 0 growth rates being many times higher than the deterministic 75 th percentile values per MRP-55 and MRP-115. Nevertheless, as described below, the large majority of the data points for the conditions directly relevant to plant conditions (e.g., constant load conditions) are located more than a factor of 12.0 below the deterministic (75 th percentile) MRP-55 and MRP-115 equations. 2 DISCUSSION OF DATA POINTS FROM MRP-375 [2] 2.1 Data Points Above a Hypothetical 12.0 Factor of Improvement Line in Figure 3-1, 3-3, and 3-5 of MRP-375

Figure 3-1 of MRP-375. Figure 3-1 shows the complete set of data points compiled by the PWSCC Expert Panel organized by EPRI at the time MRP-375 was completed for Alloy 690 specimens with less than 10% added cold work. The following points are within a factor of 12.0 below the MRP-55 deterministic crack growth rate for Alloy 600:

There are 16 points within a factor of 12.0 below the MRP-55 75 th percentile curve, out of a total of75 points shown in Figure 3-1 ofMRP-375. These data represent test segments from six distinct Alloy 690 compact tension (CT) specimens that were tested by Centro de Investigaciones Energeticas, Medioambientales y Tecnol6gicas (CIEMA T) and two that were tested by Argonne National Laboratory (ANL). Two of the points tested by CIEMAT are from specimen 9ARB1, comprised of Alloy 690 plate material, loaded to 37 MPa(m)° 5 , and tested at 340°C and 15 cc H 2/kg H 20 [8]. Both of these data are for the first half of segments that exhibited a crack growth rate that was an order of magnitude lower in the second half of the segment. A plot of crack growth rate versus crack-tip stress intensity factor (K) for the Alloy 690 data from MRP-375 for plate material tested by CIEMAT is provided here as Figure 1. These two points have minimal implications for the requested inspection interval extension for several reasons:

As illustrated in Figure 1 and subsequent figures using open symbols, one of the two points was generated under partial periodic unloading (PPU) conditions.

As discussed below in Section 2.2, PPU conditions may result in accelerated crack growth rates that are not directly representative of plant conditions, especially for the case of alloys with relatively high resistance to environmental cracking like Alloy 690.

U.S. PWRs operate with a dissolved hydrogen concentration per EPRI guidelines in the range of 25-50 cc/kg for Mode 1 operation. Testing at 15 cc/kg results in accelerated crack growth rates versus that for normal primary water due to the proximity of the Ni-NiO equilibrium line [2].
Specimens fabricated from Alloy 690 plate material are not as relevant to plant RV top head penetration nozzles as specimens fabricated from control rod drive mechanism (CRDM) / control element drive mechanism (CEDM) nozzle 3

Dominion fn~ineerin~, Inc. TN-5696-00-02, Rev. 0 material. CRDM and CEDM nozzles in U.S. PWRs are fabricated from extruded pipe or bar stock material. Note that term CRDM nozzle is used henceforth to refer to both CRDM and CEDM nozzles (CEDM is the terminology used by plants designed by Combustion Engineering).

The wide variability in crack growth rate within even the same testing segment indicates that significant experimental variability exists. Thus, there is a substantial possibility that a limited number of elevated growth rate data points do not reflect the true characteristic behavior of the material tested.

The remaining 11 CIEMA T points are from specimens comprised of Valinox WP787 CRDM nozzle material that was cold worked by a 20% tensile elongation (9.1 % thickness reduction) [9]. One datum was for specimen 9T3-tested at 310°C, 22 cc H2/kg H20 , and 39 MPa(m)05-but was from the test period immediately following a reduction in temperature from 360°C to 3 l 0°C [9]. The next period of constant load growth had a factor of 10 lower CGR. The other 10 data are for testing at 325°C and 35 cc H 2/kg H 2 0, and seven of these points are for PPU testing (which may accelerate growth beyond what would be expected for in-service components). Four of the data are for specimens 9Tl and 9T2 (loaded to roughly 36 MPa(m) 0 5), and the remaining six data are from specimens 9T5 or 9T6 (loaded to roughly 27 MPa(m)0 5). The results for 9Tl and 9T2 are contained in Reference [9]; the final data for 9T5 and 9T6 are contained in EPRI MRP-340, but have not been openly published. As discussed later in Section 2.4, the addition of cold work may result in a material that is substantially more susceptible than the as-received material. The extent of transition along the crack front to intergranular cracking for these data was extremely low (:S 10%) for the ten points from specimens tested at constant temperature. A plot of crack growth rate versus K for the Alloy 690 data from MRP-375 for heat WP787 is provided here as Figure 2. As in Figure 1, there is significant growth rate variability within the data for the same heat of material. The median for the CIEMAT specimens is more than a factor of 12 below the MRP-55 curve. Additionally, the Pacific Northwest National Laboratory (PNNL) data indicate that the specific laboratory that produces the data can significantly influence the reported growth rate, such that there is a substantial possibility that a small number of reported data points with relatively high crack growth rates from a single laboratory are not characteristic of the true susceptibility of a specific heat of Alloy 690 material. The three ANL data points are for CT specimens C690-CR-1 and C690-LR-2, comprised ofValinox heat number WP142 CRDM nozzle material that were not cold worked and were tested at 21 to 24 MPa(m) 05 , 320°C, and 23 cc H2/kg H2 0 [10]. The intergranular engagement for these specimens was extremely low (almost entirely transgranular). A plot of crack growth rate versus K for the Alloy 690 data from MRP-375 for heat WP142 is provided here as Figure 3. As in Figure 2, PNNL data indicate that the specific laboratory that produces the data can significantly influence the reported growth rate.

Figure 3-3 of MRP-375. Figure 3-3 shows the complete set of data points compiled for Alloy 690 heat affected zone (HAZ) specimens at the time MRP-375 was completed by the PWSCC Expert Panel that was organized by EPRI. The following points are within a factor of 12.0 below the MRP-55 deterministic crack growth rate for Alloy 600:

4

Dominion fn~ineerin~, Inc. TN-5696-00-02, Rev. 0 There are eight points within a factor of 12.0 below the MRP-55 75 th percentile curve, out of a total of 34 points shown in Figure 3-3 of MRP-375. All but one of the eight data points are for PPU testing, and all but two appear to have had very little to no intergranular engagement. Six of the points are from ANL testing of specimens comprised ofValinox CRDM nozzle material heat WP142 and Alloy 152 filler (Special Metals heat WC43E9), tested at 320°C and 23 cc H2/kg H 2 O [11]. Five of the points are from specimens CF690-CR-1 and CF690-CR-3 (loaded to roughly 28 to 32 MPa(m)05 ) [11], and the other point is from specimen CF690-CR-4 (loaded to roughly 22 MPa(m) 0 5) [12]. A plot of crack growth rate versus K for all the Alloy 690 HAZ data from MRP-375 for heat WP142 is provided here as Figure 4. As discussed below, PPU conditions-under which five of these six points were obtained-may result in accelerated crack growth relative to plant conditions. The remaining two points are from CIEMAT testing of specimens 19ARH 1 and 19ARH2, comprised of welded Alloy 690 plate material, tested at 340°C and 15 cc H2/kg H2 O, and loaded to roughly 37 MPa(m) 05 [8]. A plot of crack growth rate versus K for the Alloy 690 HAZ data from MRP-375 for plate material tested by CIEMAT is shown in Figure 5. As discussed later, the orders of magnitude difference between these two PPU points and the constant load testing for this HAZ is indicative of the substantial accelerating effect that PPU testing can have beyond what would be expected in service environments.

Figure 3-5 ofMRP-375. Figure 3-5 shows the complete set of data points compiled by the PWSCC Expert Panel organized by EPRl at the time MRP-375 was completed for Alloy 52 and 152 weld metal specimens. The following points are within a factor of 12.0 below the MRP-115 deterministic crack growth rate for Alloy 182:

There are 19 points within a factor of 12.0 below the MRP-115 75 th percentile curve, out of a total of212 points shown in Figure 3-5 of MRP-375. Five of these points are not relevant to PWR conditions and should not be considered further, as discussed in the following bullets.

One of these points is from PNNL testing of the dilution zone of a dissimilar metal weld between 152M (Special Metals heat WC83F8) and carbon steel, tested at 360°C and 25 cc H2/kg H2O [13]. This material condition is not applicable to the wetted surfaces of CRDM nozzle I-groove welds because the dilution zone where Alloy 52/152 contacts the low-alloy steel RV head is below the stainless steel cladding. A plot of crack growth rate versus K for the Alloy 152 data from MRP-375 for heat WC83F8 is provided here as Figure 6.
Four of the remaining points, including the point closest to the MRP-115 curve, are for environmental fatigue pre-cracking test segments [14]. The status of these four data points, which are shown in black in Figure 7, as being fatigue pre-cracking test segments irrelevant to PWSCC conditions was clarified subsequent to publication of MRP-375.

The remaining 14 data points represent four specimens from Alloy 152 weld material (Special Metals heat WC04F6) that were tested by ANL at 320°C and 23 cc H2/kg H2 O ([15] and [10]). Ten of these points are for specimen A152-TS-5 at loads of about 28, 32, and 48 MPa(m) 05 [14]. The other four points were obtained at loads of 5

Dominion fn~ineerin~, Inc. TN-5696-00-02, Rev. 0 27 MPa(m) 05 for specimen N152-TS-1 and 30 MPa(m)05 for specimens A152-TS-2 and Al52-TS-4. The Alloy 152 specimens all came from welded plate material. A plot of crack growth rate versus K for the Alloy 152 data from MRP-375 for heat WC04F6 is provided here as Figure 7. All but three of these points were for PPU conditions, which may result in accelerated crack growth rates that are not directly representative of plant conditions. Figure 7 shows a very large variability in the crack growth rate reported by different laboratories for this heat of Alloy 152 weld material. Roughly one third the ANL data (specimen N152-TS-l), all of the General Electric Global Research Center (GE-GRC) data, and all the PNNL data for this heat are for specimens from a single weld made by ANL [16], illustrating the role of experimental variability. A small number of elevated data points for a weld produced by a single laboratory may not be representative of the true material susceptibility. 2.2 Data Most Directly Applicable to Plant Conditions As described above, Section 3 of MRP-375 took an inclusive approach to statistical assessment of the compiled data. A conservative approach was applied in which both constant load data and data under PPU conditions were plotted together. In addition, weld data reflecting various levels of weld dilution adjacent to lower chromium materials was included in the data for Alloys 52/152. An assessment of the crack growth rate data points most applicable to plant conditions is presented in Figure 8 through Figure 13. The assessment shows very few points located within a factor of 12.0 below the deterministic MRP-55 and MRP-115 lines, with such points only slightly above the line representing a factor of 12.0:

Figure 8 for Alloy 690 with Added Cold Work Less than 10%.

Only seven of the 55 points are within a factor of 12.0 below the MRP-55 deterministic crack growth rate for Alloy 600. Figure 9 shows that the data are bounded by an FOI of more than 12 relative to Alloy 600 data on a statistical basis.

Figure 10 for Alloy 690 HAZ.

Only one of the 24 points is within a factor of 12.0 below the MRP-55 deterministic crack growth rate for Alloy 600. Figure 11 shows that the data are bounded by an FOI of more than 12 relative to Alloy 600 data on a statistical basis.

Figure 12 for Alloys 52/152.

Only three of 83 points are within a factor of 12.0 below the MRP-115 deterministic crack growth rate for Alloy 182. Figure 13 shows that the data are bounded by an FOI of more than 12 relative to Alloy 182 data on a statistical basis. As discussed above, the technical basis for heads with Alloy 600 nozzles assumes the substantial possibility of crack growth rates substantially greater than that predicted by the deterministic 6

Dominion fn~ineerin~, Inc. TN-5696-00-02, Rev. 0 equations ofMRP-55 and MRP-115 . The MRP-55 and MRP-115 deterministic crack growth rate equations are not bounding equations, but rather reflect the 75th percentile of material variability. Thus, the perspective provided in Figure 9, Figure 11, and Figure 13 is most relevant to drawing conclusions regarding FOI values applicable to inspection intervals for heads fabricated using Alloy 690, 52, and 152 materials. The data presented in Figure 8 through Figure 13 were included on the basis of the following considerations:

As demonstrated and discussed in MRP-115, certain PPU conditions will act to accelerate the crack growth rate. PPU conditions, which include a periodic partial reduction in load, are often used in testing to transition from initial fatigue conditions toward constant load conditions with the crack in a state most representative of stress corrosion cracks if they had initiated in plant components over long periods of time. The periodic load reductions and accompanying load increases may rupture localized crack ligaments along the crack front, facilitating transition of the crack to an intergranular morphology. In MRP-115, data with hold times less than 1 hour were screened out of the database for Alloys 82/182/132.

The greater resistance of Alloys 690/52/152 to cracking is expected to result in a greater sensitivity of the crack growth rate to partial periodic unloading conditions. Figure 14 and Figure 5, in particular, show that there is an apparent significant bias for the data for Alloy 690 in which the data for partial periodic unloading conditions are substantially higher than for constant load conditions. Thus, the data presented in Figure 8 through Figure 13 have been restricted to the constant load (or constant K) conditions that are most relevant to plant conditions for growth of stress corrosion cracks.

The Alloy 52/152 weld metal data shown in Figure 3-5 and Figure 3-6 of MRP-375 include data reflecting a range of weld dilution levels. The data presented in Figure 12 and Figure 13 exclude the weld dilution data points because of the limited number of data points available, the variability in results, and the limited area of continuous weld dilution for potential flaws to grow through. The weld dilution data are not reflective of the full chromium content of Alloy 52/152 weld metal.
The data presented in Figure 12 and Figure 13 exclude a small number of data points that reflect cracking at the fusion line with carbon or low-alloy steel material. Some of these data reflect cracking in the adjacent carbon or low-alloy steel material that was not post-weld heat treated as would be the case in plant applications.
The data presented in Figure 12 and Figure 13 eliminate the few data points that in fact reflect fatigue pre-cracking rather than stress corrosion cracking. The status of these data points was clarified subsequent to publication of MRP-375.

The limited number ofremaining points in Figure 8 and Figure 12 that lie within a factor of 12.0 below the deterministic MRP-55 and MRP-115 lines represent the upper end of material and/or experimental variability. Figure 9, Figure 11, and Figure 13 consider the variability in crack growth rate among different heats/welds of Alloys 600/82/182 and compare this against the full variability of the Alloy 690/52/152 data most applicable to plant conditions. The lack of any 7

Dominion fn~ineerin~, Inc. TN-5696-00-02, Rev. 0 points within a factor of 12 when accounting for variability in Alloy 600/82/182 crack growth rates supports a reexamination interval longer than the requested interval corresponding to an FOI of 12.0. The volumetric or surface inspection interval for heads with Alloy 600 nozzles reflects consideration of crack growth rates on a statistical basis, with crack growth rates often higher than that given by the deterministic equations ofMRP-55 and MRP-115. 2.3 Data Specific to Argonne National Laboratory (ANL) and Pacific Northwest National Laboratory (PNNL) The U.S. NRC is most familiar with the crack growth data for Alloys 690/52/152 that have been generated by ANL and PNNL, so the data specific to these national laboratories have also been evaluated separately. Based on the compilation of ANL and PNNL crack growth rate data recently released by NRC [17]4, the results are shown in Figure 15 through Figure 20. These data reflect Alloy 690 test specimens with up to 22% added cold work. The data in Reference [17] are consistent with the ANL and PNNL data in the wider database presented in MRP-375. As shown in Figure 15, Figure 17, and Figure 19, only 10 of the total of 86 constant load (or constant K) data points generated by ANL and PNNL are within a factor of 12.0 below the deterministic MRP-55 and MRP-115 lines. Only one of these points is within a factor less than 9.0 below the deterministic MRP-55 and MRP-115 lines. Furthermore, among the constant load data, only five of the 55 points with less than 10% cold work are within a deterministic factor of 12.0. Finally, when the statistical variability in material susceptibility is considered for the reference material (Alloys 600 and 182) as well as for the subject replacement alloys, all the data points for constant load conditions show a factor of improvement greater than 12.0. This favorable result is clearly illustrated in Figure 16, Figure 18, and Figure 20. 2.4 Data for Alloy 690 Wrought Material Including Added Cold Work up to 20% for CRDM Nozzle and Bar Material Product Forms An assessment of the crack growth rate data points for Alloy 690 CRDM nozzle and bar material product forms for cold work levels up to 20% is presented in Figure 21 and Figure 22. Equivalent plots for Alloy 52/152 material for the purpose of including the limited number (i.e., five) of weld metal data points generated for added cold work conditions are shown in Figure 23 4 The data in Reference [16] are augmented by the crack growth rate data for Alloys 52/152 produced by PNNL and previously published in an NRC NUREG contractor report [17]. While these PNNL data are shown graphically in Enclosure 3 of Reference [16], the enclosures of tabular data in this NRC document omitted all of the PNNL data for Alloys 52/152. It is also noted that contrary to the enclosure titles of Reference [16], Enclosure 2 contains the PNNL tabular data, and Enclosure 4 contains the ANL tabular data. 8

Dominion fn~ineerin~, Inc. TN-5696-00-02, Rev. 0 and Figure 24. Added cold work for weld metals is not directly relevant to plant material conditions. For Alloy 690 control rod drive mechanism (CRDM) / control element drive mechanism (CEDM) nozzles and other RV head penetration nozzles, the effective cold-work level in the bulk Alloy 690 base metal is expected to be no greater than roughly 10%. This is based on fabrication practices specific to replacement heads, i.e., material processing and subsequent nozzle installation via welding [19]. Furthermore, the crack growth rate data presented for Alloy 600 in MRP-55 do not include cases of added cold work. Comparing cold worked Alloy 690 data against non-cold worked Alloy 600 data results in a conservatism in the factor of improvement for Alloy 690 material as the cold worked material condition for Alloy 600 would be expected to result in a somewhat increased deterministic crack growth rate for Alloy 600, and thus a greater apparent factor of improvement. Nevertheless, the assessment in Figure 21 through Figure 24 is included in this document to illustrate the effect of higher levels of cold work. These data show the potential for modestly higher crack growth rates for such elevated cold work levels for the material product forms most relevant to RV top head nozzles. 2.5 Conclusion The data presented above support factors of improvement greater than 12 for the CGR performance of Alloys 690/52/152. Thus, the available laboratory CGR data support a volumetric inspection interval of at least 20 years for Alloy 690 RV head nozzles. 3 POTENTIAL IMPLICATIONS OF SPECIFIC CATEGORIES OF NOZZLE AND WELD MATERIALS Section 3 assesses the available laboratory CGR data for the potential concern of elevated CGRs for specific categories of nozzle and weld materials. 3.1 Potential Similarities for Laboratory Specimen Material Exhibiting a Deterministic Factor Less than 12.0 Any similarities between (a) the data points within a factor of 12.0 below the MRP-55/MRP-l 15 curve in Figure 3-1, 3-3, and 3-5 ofMRP-375 and (b) the associated nozzles and weld material used in the RV heads in U.S. PWRs are as follows: 9

Dominion tn~ineerin~, Inc TN-5696-00-02, Rev. 0

Figure 3-1 of MRP-375 [2]. The only Alloy 690 CRDM material for which crack growth rate data were available at added cold work of less than 10% (the threshold for inclusion in Figure 3-1 of MRP-375) was supplied by Valinox Nucleaire. The few data using CRDM material from other suppliers were obtained at cold works of 20% or higher and were not included in the assessment. The data do not indicate any correlation between material supplier and susceptibility to crack growth rate. Fourteen of the Alloy 690 crack growth data points within a factor of 12.0 below the MRP-55 [1] deterministic crack growth rate in Figure 3-1 ofMRP-375 were produced for specimens of Alloy 690 CRDM nozzle material that was supplied by Valinox Nucleaire. However, for the reasons explained below (e.g.,

the variability among data from different laboratories, the variability among data for a single heat and laboratory, and the use of PPU for eight of these 14 data), this similarity in no way indicates any specific concern for elevated PWSCC susceptibility of the head nozzle material provided by any one supplier.

Figure 3-3 of MRP-375 [2]. Six of the Alloy 690 HAZ data points above a crack growth rate 12.0 times lower than the MRP-55 deterministic crack growth rate in Figure 3-3 of MRP-375 were also produced for specimens of Alloy 690 CRDM nozzle material that was supplied by Valinox Nucleaire. However, for the reasons explained below, this similarity in no way indicates any specific concern for elevated PWSCC susceptibility of head nozzles produced from Valinox material in comparison to Alloy 690 nozzles from another supplier. It is noted that the welding process used to produce the HAZ in the test specimens is not specific to any particular categories of replacement heads.
Figure 3-5 of MRP-375 [2]. There are no relevant similarities between (a) the Alloy 52 and 152 data points above a crack growth rate 12.0 times lower than the MRP-115 [2]

Alloy 182 deterministic crack growth rate in Figure 3-5 ofMRP-375 and (b) the Alloy 52/152 weld material used in any particular categories ofreplacement heads. The variability among test welds with respect to PWSCC crack growth susceptibility reflects a combination of how the weld was made (welding procedure, weld design, degree of constraint, etc.) and perhaps the material variability in the weld consumable (e.g., composition). The test welds used to produce the specimens that showed crack growth rates within a factor of 12.0 below the MRP-115 crack growth rate are not identified with any particular fabricator ofreplacement RV heads. Furthermore, the weld specimens used in the crack growth rate testing were machined from test welds in flat plates, not from actual J-groove welds. Thus, the test weld specimens should not be associated with particular fabrication categories of replacement heads. 3.2 Potential Implications The material and welding similarities in no way indicate any specific concern for elevated PWSCC susceptibility of the head nozzles at any U.S. PWR or provided by any supplier in comparison to other heads with Alloy 690 nozzles or Alloy 690 nozzles supplied by any other supplier. It is emphasized that a small number of data points showing relatively high crack growth rates cannot readily be concluded to be characteristic of the true material behavior expected in the field. This conclusion is made considering the following: 10

Dominion fn~ineerin~, Inc TN-5696-00-02, Rev. 0

The only heats of Alloy 690 CRDM nozzle material that have been used in crack growth rate testing with less than 10% added cold work are supplied by Valinox. Consequently, there is no basis to suggest material from any one supplier is more susceptible than that from another based on the presence or absence of data points within a given factor of the deterministic crack growth rate curve from MRP-55.
The data points showing the highest crack growth rates for the tested Valinox material reflect partial periodic unloading conditions. As discussed above, such conditions tend to result in accelerated crack growth rates that are not representative of plant conditions.
Most of the crack growth rate data for heats that had points within a factor of 12.0 below the MRP-55 deterministic curve or MRP-115 deterministic curve were substantially lower.

The best-estimate behavior for every heat or test weld of material presented in Figures 3-2, 3-4, and 3-6 ofMRP-375 reflects a factor of improvement of 12 or greater. In addition, other factors being equal, one would expect a greater range of crack growth rates for a material heat for which a greater number of data points was produced. Some of the scatter likely reflects experimental uncertainty as opposed to true material variability. Experimental uncertainty is more of a factor for the data for Alloys 690/52/152 than for Alloys 600/82/182/132 considering the greater testing challenges associated with the more resistant replacement alloys.

In some cases, different laboratories have reported large differences in crack growth rate for the same material heat or test weld. This behavior is illustrated in Figure 7 for the Alloy 152 heat WC04F6 and Figure 3 for the Alloy 690 heat WP142. Thus, individual data points showing relatively high crack growth rates might not reflect the true susceptibility of particular categories of nozzle or weld material. Consistent data from multiple laboratories may be needed before one can conclude that a particular category of nozzle or weld material has an elevated susceptibility to PWSCC growth.
Some type of PWSCC initiation is necessary to produce a flaw that may grow via PWSCC.

Laboratory and plant experience show that Alloys 690/52/152 are substantially more resistant to PWSCC initiation than Alloys 600/82/182 [2]. PWSCC has not been shown to be an active degradation mode for Alloys 690/52/152 components after use in PWR environments for over 25 years.

The crack growth rate data compiled in MRP-375 [2] for Alloys 52 and 152 reflect the composition variants applicable to PWR plant applications. Data are included for the following variants: Alloy 52 (UNS N06052 / A WS ERNiCrFe-7), Alloy 52M (UNS N06054 I AWS ERNiCrFe-7A), Alloy 52MSS (UNS N06055 / AWS ERNiCrFe-13), Alloy 52i (AWS ERNiCrFe-15), Alloy 152 (UNS W86152 / AWS ENiCrFe-7), and Alloy 152M (UNS W86152 / A WS ENiCrFe-7). Considering the overall set of available crack growth rate data for the various variants of Alloy 52 and 152, there is no basis for concluding at this time any significant difference in the average behavior between the Alloy 52 and Alloy 152 variants in use at U.S. PWR RV heads with Alloy 690 nozzles.

In addition, it should be recognized that PWSCC of Alloy 690 RV head penetration nozzles or their Alloy 52/152 attachment welds is not an active degradation mode. Thus, it is premature to single out individual materials or fabrication categories of heads with Alloy 690 nozzles for additional scrutiny on the basis of subsets of laboratory crack growth rate data. In the case of 11

Dominion fn~ineerin~, Inc TN-5696-00-02, Rev. 0 heads with Alloy 600 nozzles, for which PWSCC is an active degradation mode, materials and fabrication categories of heads with relatively high incidence of PWSCC are inspected in accordance with the same requirements as other heads. Based on the additional information and discussion provided above, it is concluded that the available crack growth rate data do not indicate any susceptibility concerns specific to the nozzle or weld materials specific to any given replacement head or category of replacement heads. 4 REFERENCES I. Materials Reliability Program (MRP) Crack Growth Rates for Evaluating Primary Water Stress Corrosion Cracking (PWSCC) of Thick-Wall Alloy 600 Materials (MRP-55) Revision 1, EPRI, Palo Alto, CA: 2002. 1006695. [freely available at www.epri .com]

2. Materials Reliability Program Crack Growth Rates for Evaluating Primary Water Stress Corrosion Cracking (PWSCC) ofAlloy 82, 182, and 132 Welds (MRP-115), EPRI, Palo Alto, CA: 2004. 1006696. [freely available at www.epri .com]

3. ASME Code Case N-729-1, "Alternative Examination Requirements for PWR Reactor Vessel Upper Heads With Nozzles Having Pressure-Retaining Partial-Penetration Welds, Section XI, Division l ," Approved March 28, 2006.

4. Materials Reliability Program: Technical Basis for Reexamination Interval Extension for Alloy 690 PWR Reactor Vessel Top Head Penetration Nozzles (MRP-375), EPRI, Palo Alto, CA: 2014. 3002002441. [freely available at www.epri .com]

5. Materials Reliability Program: Inspection Plan for Reactor Vessel Closure Head Penetrations in US. PWR Plants (MRP-117) , EPRI, Palo Alto, CA: 2004. 1007830. [freely available at www.epri.com; NRC ADAMS Accession No. ML043570129)

6. Materials Reliability Program: Reactor Vessel Closure Head Penetration Safety Assessment for US. PWR Plants (MRP-1 JONP) , EPRI, Palo Alto, CA: 2004. 1009807-NP.

[ML041680506]

7. Materials Reliability Program: Probabilistic Fracture Mechanics Analysis of PWR Reactor Pressure Vessel Top Head Nozzle Cracking (MRP-105 NP) , EPRI, Palo Alto, CA:

2004. 1007834. [ML041680489]

8. D. G6mez-Bricefio, J. Lapefia, M. S. Garcia, L. Castro, F. Perosanz, and K. Ahluwalia, "Crack Growth Rate of Alloy 690 / 152 HAZ," Presented at: Alloy 690/152/52 Research Collaboration Meeting, Tampa, FL, December 1-2, 2010.

9. D. G6mez-Bricefio, J. Lapefia, M. S. Garcia, L. Castro, F. Perosanz, L. Francia, and K.

Ahluwalia, "Update of the EPRI-UNESA-CIEMAT Project CGR Testing of Alloy 690," 12

Dominion fn~ineerin~, Inc. TN-5696-00-02, Rev. 0 Presented at: Alloy 690/152/52 Research Collaboration Meeting, Tampa, FL, November 29-December 3, 2011.

10. Stress Corrosion Cracking in Nickel-Base Alloys 690 and 152 Weld in Simulated PWR Environment-2009, NUREG/CR-7137, June 2012.

11. B. Alexandreanu, Y. Chen, K. Natesan and B. Shack, "Cyclic and SCC Behavior of Alloy 690 HAZ in a PWR Environment," 15th International Conference on Environmental Degradation, pp. 109-125, 2011.

12. B. Alexandreanu, Y. Chen, K. Natesan and B. Shack, "Update on SCC CGR Tests on Alloys 690/52/152 at ANL-June 2011," Presented at: US NRCIEPRI Meeting, June 6-7, 2011. [MLl 11661946]

13. M. Toloczko, M. Olszta, N. Overman, and S. Bruemmer, "Stress Corrosion Crack Growth Response For Alloy 152/52 Dissimilar Metal Welds In PWR Primary Water," 16th International Conference on Environmental Degradation of Materials in Nuclear Power Systems- Water Reactors, Paper No. 3546, 2013.

14. B. Alexandreanu, Y. Chen, K. Natesan and B. Shack, "SCC Behavior of Alloy 152 Weld in a PWR Environment," 15th International Conference on Environmental Degradation, pp.

179-196, 2011.

15. B. Alexandreanu, Y. Chen, K. Natesan and B. Shack, "Cyclic and SCC Behavior of Alloy 152 Weld in a PWR Environment," Presented at: Alloy 690/152/52 Research Collaboration Meeting, Tampa, FL, November 29-December 3, 2011.

16. M. Toloczko, M. Olszta, N. Overman, and S. Bruemmer, "Observations and Implications of Intergranular Stress Corrosion Crack Growth of Alloy 152 Weld Metals in Simulated PWR Primary Water," 16th International Conference on Environmental Degradation of Materials in Nuclear Power Systems- Water Reactors, Paper No. 3543, 2013.

17. Memo from M. Srinivasan (U.S. NRC-RES) to D. W. Alley (U.S. NRC-NRR),

           "Transmittal of Preliminary Primary Water Stress Corrosion Cracking Data for Alloys 690, 52, and 152," October 30, 2014. [ML14322A587]

18. Pacific Northwest National Laboratory Investigation of Stress Corrosion Cracking in Nickel-Base Alloys, NUREG/CR-7103, Vol. 2, April 2012.

19. Materials Reliability Program: Material Production and Component Fabrication and Installation Practices for Alloy 690 Replacement Components in Pressurized Water Reactor Plants (MRP-245), EPRI, Palo Alto, CA: 2008. 1016608.

13

Dominion fn~ineerin~, Inc. TN-5696-00-02, Rev. 0 Data from Individual Heats 1.E-09 j i. CIEMAT I MRP-551 Curve/1 I 1.E-10 en

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temperature (325°C) . Q = 130 kJ/mol 1.E-13 10 15 20 25 30 35 40 45 50 55 60 Stress Intensity Factor (MPam) Figure 1. Plot of Crack Growth Rate (da/dt) versus Stress Intensity Factor (K1) for Alloy 690 Data from Plate Material Tested by CIEMAT 1.E-09

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Figure 2. Plot of da/dt versus K1 for Alloy 690 Data from Heat WP787 14

Dominion fn~ineerin~, Inc. TN-5696-00-02, Rev. 0 1.E - OANL

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V 10 15 20 25 30 35 40 45 50 55 60 Stress Intensity Factor (MPam) Figure 3. Plot of da/dt versus K, for Alloy 690 Data from Heat WP142 1.E-09

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Dominion fn~ineerin~, Inc. TN-5696-00-02, Rev. 0 1.E-09

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     *Figure 5.        Plot of da/dt versus Ki for Alloy 690 HAZ Data from Plate Material Tested by CIEMAT 1.E                           DGE-GRC
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Dominion fn~ineerin~, Inc. TN-5696-00-02, Rev. 0 1.E - OANL DGE-GRC l;l MRP-115 - Curve/1

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1.E-13 10 15 20 25 30 35 40 45 50 55 60 Stress Intensity Factor (MPam) Figure 7. Plot of da/dt versus K1 for Alloy 152 Data from Heat WC04F6 17

Dominion fn~ineerin~, Inc. TN-5696-00-02, Rev. 0 Data Most Applicable to Plant Conditions 1.E-09

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1.E-13 10 15 20 25 T 30 35 40 45 Q = 130 kJ/mol 50 55 60 Stress Intensity Factor (MPam) Figure 8. Plot of da/dt versus K1 for Alloy 690 Data from All Laboratories, S 10% Cold Work, Constant Load or K1 1.0 OANL 0.9

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                                   .,,,,,,,                                                                K = 30 MPam 0.0 ~ --=:...:............,.,..._.......~::.._wL...U.f----'---1---J'--L.J.--LLJ..f----L..--=c:==:q::::::====Ii.l 1.E-13                       1. E-12           1.E-11                  1.E-10            1.E-09               1.E-08 Crack Growth Rate (mis)

Figure 9. Cumulative Distribution Function of Adjusted da/dt for Alloy 690 Data from All Laboratories, S 10% Cold Work, Constant Load or Ki 18

Dominion fn~ineerin~, Inc. TN-5696-00-02, Rev. 0 1.E-09

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Figure 10. Plot of da/dt versus K1 for Alloy 690 HAZ Data from All Laboratories, S 10% Cold Work, Constant Load or K1 1.0 0 ,,,,,,. 0 OANL 0.9

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                                       /                                                             K = 30 MPa m 0.0 1.E-13                   1.E-12           1.E-11               1.E-10            1.E-09                1.E-08 Crack Growth Rate (mis)

Figure 11. Cumulative Distribution Function of Adjusted da/dt for Alloy 690 HAZ Data from All Laboratories, S 10% Cold Work, Constant Load or Ki 19

Dominion fn~ineerin~, Inc. TN-5696-00-02, Rev. 0 1.E-09 oANL

                             - A CIEMAT
                                            ~ MRP-115 i---               -
                             - DGE-GRC              Curve/1 I

1. E

PNNL I

        - Q) co 0::

j_MRP/12r

                                                             -      0-
                                                                                 -- . . . . ~                        - -{

r, Q

                                                                                                                               -~
        =

j 1.E-11

                                 ~
          ....0

(!) i...

        ..lll:

0 A

          ....co 1.E-12                                            *            '\ 1        ~                        ~
                             -     Data are adjusted for                                                               ~           ,
                             -    temperature (325°C).

Q = 130 kJ/mol

                                                             ~ 1:J_ -~     :i-- - - 3                             V
                                                                                                                               ~
                                                                                                                  ~
                                                                           ~         l:.J        ~~

1.E-13 y y 10 15 20 25 30 35 40 45 50 55 60 Stress Intensity Factor (MPam) Figure 12. Plot of da/dt versus K, for Alloy 52/152 Data from All Laboratories, S 10% Cold Work, Constant Load or K,

            § 0.7 t -- - - ---e'- - - - - - - - --                                                  -,-- - - - --l.l!...~=-.!.LJ---j

I

t i)

          ~ 0.5 0.6 -+---- - --            - - - - - - - - - ----,..-- - - - --
                        +--- ----c§- - - - - - - - - - --1--                                             ---1 The data points at 1E-13
                                                                                                                                                  -    --1
            >                                                                                                            were reported as "no
          ~ 0.4         +--      ~r--- - - - - - - - - --1-- -----,                                                              growth."

E :=::===:=r:::::===========: 8 0.3 +--a.1!=---- - - - - - - - - - -- - -------1 Data are adjusted for FOi = 12 temperature (325°C) and 0.2 +.IA111L-- - - - - - - - - --=====- -------l stress intensity factor. 0.1 P-- - -- - -- - - - --,-- - - -------1 I Q = 130 kJ/mol K= 30 MPam 0.0 ' -- - - - -................"""""+----....:-"':::::..........'"""""-i-----'--~:i::i:i::::i:i===:::::;:::::::i::::::;::::;:::::::;::~ 1.E-13 1.E-12 1.E-11 1.E-10 1.E-09 Crack Growth Rate (mis) Figure 13. Cumulative Distribution Function of Adjusted da/dt for Alloy 52/152 Data from All Laboratories, S 10% Cold Work, Constant Load or Ki 20

Dominion fn~ineerin~. Inc. TN-5696-00-02, Rev. 0 Comparison of Partial Period Unloading (PPU) Conditions vs. Constant Load Conditions 1.E-09 Data are adjusted for ....: Specimen temperature (325°C) (Q = 130 - - 9T1 1.E-10

                        --, PPU Data r -------------,                 kJ/mol) and K (30 MPam) 9T2 U) g                                                                    Const. Load Data ~ ~            9T3
                                                      ,_                                                ~    9T4
                                ~                                              I                I Q)

I I I ca -+- 9T5 c::: I

        ..c                  I   ,                                                              I 1.E-11                                                                                   D 9T6
        ~

0 (!) ~ - 9TB

        .lll::

0

          ....ca I
                                "/
                                '/
                                ,  ------          _, '-    ~

I ~

"/,

I

                                                                                          '>I'          -0, 9T9 u

1.E-12 I I ~

I

                                                                         ---L      \  / $.      I I                               I              ~

I 1.E-13 I I ----- --* I I 10 100 1000 10000 Hold Time (Hours) Figure 14. Plot of da/dt versus Loading Hold Time (for PPU testing) or Test Segment Duration (for Constant Ki/Load Testing) from Heat WP787 21

Dominion fn~ineerin~. Inc. TN-5696-00-02, Rev. 0 Compilation of ANL and PNNL Data 1.E-09 lBo~~~~~~~~~~~~~~~~~~~~~~~~ I: Box and arrow show the _ ratio between the MRP-55 curve and the data point r:=======================~.=====; I MRP-55 ~ 1_; --~ -~ -::-i::r I Curve/1 I 1.E-10 i - *i;===,;11 10.2

                                                                                            ;;:1                 9.3 13     9*6

_ 7 11 5

                                                                                                                       , .__ _-;:- - - - ~ -, MRP/12 r*

Cl) i' ---- - ---;::::= =--i

       ~                 r-----::~ =::::;-_J 10 2 Ll.__9~*0- -1                                        1_                      .L1    .

0::: j 1.E-11 : , ~ 10.4 I I *- I '::_:+_6 -t- ,,___ I - I e e> w-

                          ; _ _ _ ___,._::£,_-~ ~ - -~- - - "-                                                            ' ---'-     ~- - - ---1 o ANL CL t;                1--               7"- .,r-                v           O                      Q                            _.v-- - - ---1 OANL PPU t'.3                          /           - - - - - -~ - - - -~- -*~                                                                                                   PNNL 1.E-12 f=-_,..::.
                             -~.-:L-~
                                    - ~- ~=~-~-=-~-~-=-~~-=.~_ ~--~~-~                      -*jr,:~:,~
                                                                                                     -.,,..~-~~~~~~3~~-~~~tFr~=~~~
                                                                                                                                 ~                 Data are adjusted for I

1--- - - - - - - - -~ t~ . 0 ~

                                                                                                                    ~         ~

temperature (325°C). Q = 130 kJ/mol 1.E-13 +-'--'-'--'-+...J.....J.....J.....J..-+-"....L.....1.--'--t...J......l~ A~~'-<:~:>-<:~ :,--,.....:~ J........L-.i...+..L......J.._..L......J.._-t-'---'-'---'-+...J.....J..-'--'-i 10 15 20 25 30 35 40 45 50 55 60 Stress Intensity Factor (MPam) Figure 15. Plot of da/dt versus Ki for Alloy 690 Data Produced by ANL and PNNL and Available in Reference [17]; :S 22% Cold Work 1.0 ,------------------=---------~----::;;;-------, ,... 0.9 - - - - - - - - - ~ <>-'--~ - - - - ----- - - - - - - - - - - - - ! 0.8 +-- - - - - - - - - l i } . ~--,-- - - - -__,_- - - - - - - -----l

         ]     0.? +--------c,c--<Y--                                               --J' - - - - - --1-- - - - - ---,--0-A-NL_C_L--,...j

s

g 0.6 +--- - -- ~ - - -+--- - - - - - - - - ---1 PNNL 1ii

         ~ 0.5 1 - - - J r - - - -, -- - --;=::::::::::::c=.:;---                                                                  ---j The data points at 1E-13 are
         .2:                                                                                                                                 treated as "no growth,"
         ~ 0.4                                                                                                                              consistent with MRP-375.

E 8 0.3 Data are adjusted for IFOi = 12 I temperature (325°C) and 0.2 ~ - - - --========-- - --J~ - - - -- - l *

f

                                                          /                                                                                  stress IntensIty actor.

0.1 - - - -- ~ - - - -- -- - - - - -- Q = 130 kJ/mol

                                         /                                                                                                       K=30MPam 0.0 ..--...-==.......................,_ _~.l-L..1.-'-'+--'----'--'---'-"-.L..L..Lf---'--====+====:::=:r:::Lj 1.E-13                           1.E-12                                   1.E-11                         1.E-10                 1.E-09                                      1.E-08 Crack Growth Rate (mis)

Figure 16. Cumulative Distribution Function of Adjusted da/dt Alloy 690 Data Produced by ANL and PNNL in References [17]; :S 22% Cold Work and Constant Load/Ki 22

Dominion fn~ineerin~, Inc. TN-5696-00-02, Rev. 0 1.E-09 OANL CL Box and arrow show the OANL PPU

ratio between the MRP-55

                            -       PNNL           curve and the data point                                 1 MRP-55 I Curve/1  I U) 1.E-10                                                   -

E

        .....C'CI Cl)                                  -
                                         ~

_ - ~ MRP/12r"- 0:::

        .r::.

1.E-11 / I 9.3 k- oO ~

0 (!) I - - - (.J

                            ;               .,,,.- -                         ~

0

         ....C'CI                        '/

u / 1.E-12 - . *--

                                                                         ~           ~ ~      ~         Data are adjusted for
                                                                                    ~
                                                                        ~

I temperature (325°C). Q = 130 kJ/mol 1.E-13 . A

10 15 20 25 30 35 40 45 50 55 60 Stress Intensity Factor (MPam) Figure 17. Plot of da/dt versus K1 for Alloy 690 HAZ Data Produced by ANL and PNNL and Available in Reference [17]; :S 22% Cold Work 1.0 ,----------------==-------------:::;;_.,.-------, ,,,,-- 0.9 +-- - - - - - - - - - - , - - , . - - - - ~ - -- - - - - - - - ---I

0.8 + -- - - - - - - - - - . - - - - - --1---- - - - - - - - - - - - 1

                                      ~
          ]       O.? +--_,,.,___ _ _ _ __ _ _ , ~ - - - --1-- - - - - ----r-o-A_N_L_CL-,_i

g"t; 0.6 -+--- - * - - - - - -

                                                               -  - - - - - - . 1 ~ - - - - - ----1

PNNL

          ~ 0.5                                                                                  The data points at 1E-13 are
             >                                                                                      treated as "no growth ,"
          ~       0.4                                                                              consistent with MRP-375.

E 8 0.3 Data are adjusted for IFOi = 12 I temperature (325°C) and

0. 2 -- - - --=;==- - - -~ --------1 stress intensity factor.

0.1 ' I ' - - - - - - - ,- - - - - - ~ - - - - - - - - , Q = 130 kJ/mol _,, K= 30 MPam 0.0 -.:...;...............-+---~~L..LI..L+--__J,_--'---'---L.J'-'--'--'-t----'---====i=======l..l 1.E-13 1.E-12 1. E-11 1.E-10 1.E-09 1.E-08 Crack Growth Rate (mis) Figure 18. Cumulative Distribution Function of Adjusted da/dt Alloy 690 HAZ Data Produced by ANL and PNNL [17]; :S 22% Cold Work and Constant Load/Ki 23

Dominion fn~ineerin~, Inc TN-5696-00-02, Rev. 0 1.E-09 Box and arrow show the - I MRP-115 * - ratio between the MRP-115 - __....--1 Curve/1 Ff D 5.5 9.2 I curve and the data point U) 1.E-10 c;;;;;ii'* n:

                                                                                     -                                                1.. ......-       ----  ~

E Cl) __ __ err:; _- - - J "'-"

                                                                                                  ~        ---- ----           l l u

C'a 0::::

        .c j MRP/12  r           -                      -

1.E-11 3: 0 (!) c., *~

OANL CL

(.J C'a (.)

                          ~ OANL PPU
                                 ~ PNNL CK (NUREG)
                                                                                                   ~                           ~

1. E-12 Data are adjusted for .... !:>- A.

                                                                                                   ,Y
                                                                                                                               ;                ~

temperature (325°C). $ ~ Q = 130 kJ/mol *

1. E-13 A

                                                                                   ~
                                                                                             ~

V A T A V 10 15 20 25 30 35 40 45 50 55 60 Stress Intensity Factor (MPam) Figure 19. Plot of da/dt versus K1 for Alloy 52/152 Data Produced by ANL and PNNL and Available in References [17] and [18]; s 22% Cold Work 1.0 o ANL CL 0.9 PNNL CK (NUREG) ~ 0 70 --

0.8

0 0 .I I

I I I MRP-115 L (FOi - 1)

          § 0.7

I

I

g

         .... 0.6

I I

I I 1/)

I

         ~ 0.5                                 ~

The data points at 1E-13 T I

          >                                                                                                                      were reported as "no
         ~    04

I growth."

3 E I 8 0.3

                                                                                               .                              , Data are adjusted for temperature (325°C) and 0.2

IFOl=12I stress intensity factor.

0.1

I Q = 130 kJ/mol

_,,,,. / ~ K = 30 MPam 0.0 1.E-13 1.E-12 1.E-11 1.E-10 1.E-09 Crack Growth Rate (mis) Figure 20. Cumulative Distribution Function of Adjusted da/dt Alloy 52/152 Data Produced by ANL and PNNL ([17] and [18]); S 22% Cold Work and Constant Load/Ki 24

Dominion fn~ineerin~, Inc. TN-5696-00-02, Rev. 0 Data for Less than 20% Cold Work from All Laboratories 1.E-09

AMEC

                                -                                                                                               I MRP-551 CIEMAT I Curve/1 I 1.E-10      i:= DGE-GRC en
        ]_                           PNNL
                                                          ~

a,

                                               .,,,r
                                                                                - ~ --                                                -4 MRP/12r" I ll 0:::
        .c j         1.E-11            /

h. __ _

          ....0               ,;

(!)

        ..lo::

I .,,.,. ---- - - ~0 *

                                                                                                           ,,. A                                   *-

u

          ....                                -7'-                              **

Ill

        <..)

1.E-12

                                      /                                      0 D                         . A
                                ~

I

                                                                                    -T              .
                                                                                                   ...,.   ~

Data are adjusted for temperature (325°C) .

Q = 130 kJ/mol

1. E-13 10 15 20 25 30 35 40 45 50 55 60 Stress Intensity Factor (MPam)

Figure 21. Plot of da/dt versus Ki for Alloy 690 Data from All Laboratories, > 10 & S 20% Cold Work, CRDM and Bar Material, Constant Load or K1 Testing 1.0 -r.======,---------;::--~::-----------::::~- -- - - - - , v AMEC 0.9 A CIEMAT 0.8 DGE-GRC ls 0.7 PNNL

I

g U) 0.6 +--- - - - - -- - -

          ~ 0.5 -+--- - - - - - - < .> ---#-- - - -~- -- -- ~-#--- ~- - - - - I
                                                                               - - - - - - - , j > - - - - - - - - - - - ---1 The data points at 1E-13
            >                                                                                                           were reported as "no

§::I 0.4 -+--- - - -~ - - -----<

                                                                                         '-"-;.-'---'-'-'                      growth."

E 8 0.3 +--- - - - - - - # - - - - - -- ------! Data are adjusted for temperature (325°C) and 0.2 + - -- -----G---l

                                                       '---,,--~                                                       stress intensity factor.

0.1 -+--- - ~ -, - - - - - -#- - - - - - - - - 1 Q = 130 kJ/mol K = 30 MPam 0.0 ...J.-..:::cic:c....;..............~--~:.............'-'-4---'--....L-J-1--.l...,L..I...J..t----'-_'.J:::==:q::=====Iil 1.E-13 1.E-12 1.E-11 1.E-10 1.E-09 1.E-08 Crack Growth Rate (mis) Figure 22. Cumulative Distribution Function of Adjusted da/dt Alloy 690 Data from All Labs, S 20% Cold Work, CRDM and Bar Material, Constant Load or K1 25

Dominion fn~ineerin~, Inc. TN-5696-00-02, Rev. 0 1.E *- DGE-GRC _

                                            ~        MRP-115 p-""

1.E-10 ~ PNNL Curve/1 I en 1:

       -(I)

Cl:I 0::: C

                                                                --                    -      ---        n   --      -     ~      ~
       ..c:

jMRP/12r

       }:      1.E-11 0

(!)

                           ~~
       ~
                                                                                      ~

(.) Cl:I (.) 1.E * ~

                           -   Data are adjusted for temperature (325°C).

Q = 130 kJ/mol 1.E-13 10 15 20 25 30 35 40 45 50 55 60 Stress Intensity Factor (MPam) Figure 23. Plot of da/dt versus K1 for Alloy 52/152 Data from All Laboratories,> 10 & s 20% Cold Work, Constant Load or K1 0.8 D GE-GRC f - - - -= l"'lr"----- - - - - - - --1-- - - - - - - .~-==--'t.,-:-,-,- -l PNNL

S 0.7

                    +-- - - ---=I . F - - - - - - - - - - --,-- - - - --U~..=....!lJ

g 0.6

        -I I)
                    +--- - - - - - , (!,IJ-- - - - - - - - - --
        ~ o.5 +-- - - - - , . ~ - - - - - - - - - --,..- - - - 1 The data points at 1E-13
         >                                                                                                                 were reported as "no
        ~ 0.4       + -- - l l ) \ C - - - - - - - - - - - - - -- - ~                                                          growth ."

8 E 0.3 +-~ Y-~ - - - - - - - - - - - ; :=~==.-- - - - i

.=====~========:::::::

Data are adjusted for FOi = 12 temperature (325°C) and 0-2 stress intensity factor.

                    +ciF - - - - - - - - - - - - -_ . _ - - - --i 1

0. 1 1:::1--- - - - - - - - - - - - - , , - - - - - - - - 1 Q = 130 kJ/mol K = 30 MPam 0.0 ~ _ ...................................1-----=_,,,,,.:::...........i....+----'--~:i:::i::ji::::i:j:===::i:=::::i=:::;:::::;:::::jc::::;::;::y

1. E-13 1.E-12 1.E-11 1.E-10 1.E-09 Crack Growth Rate (mis)

Figure 24. Cumulative Distribution Function of Adjusted da/dt Alloy 52/152 Data from All Laboratories, s 20% Cold Work, Constant Load or Ki 26}}

v t e Letter Sequence Request
EPID:L-2018-LLR-0107, ASME Code Case N-729-4 (Open)
Initiation Request Acceptance Administration Questions Answers Results Approval... Other: ML19023A026
MONTHYEAR2018-08-23 [Table View]

DCL-18-057, Request for Alternative from Volumetric/Surface Examination Frequency Requirements of ASME Code Case N-729-4

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Dear Commissioners and Staff:

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3. Applicable Code Requirement

4. Reason for Request

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DCL-18-057, Request for Alternative from Volumetric/Surface Examination Frequency Requirements of ASME Code Case N-729-4

Text

Dear Commissioners and Staff:

2. Applicable Code Edition and Addenda

3. Applicable Code Requirement

4. Reason for Request

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