ML23352A243
| ML23352A243 | |
| Person / Time | |
|---|---|
| Site: | Electric Power Research Institute |
| Issue date: | 12/18/2023 |
| From: | Licensing Processes Branch |
| To: | Electric Power Research Institute |
| References | |
| MRP-227, Rev 2, EPID L-2022-TOP-0029 | |
| Download: ML23352A243 (11) | |
Text
1 REQUEST FOR ADDITIONAL INFORMATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION ELECTRIC POWER RESEARCH INSTITUTE REPORT NO. 3002020105, MATERIAL RELIABILITY PROGRAM:
PRESSURIZED WATER REACTOR INTERNALS INSPECTION AND EVALUATION GUIDELINES (MRP-227, REVISION 2),
EPRI PROJECT DOCKET NO. 99902021 1.0 Introduction By letter dated May 9, 2022 (Agencywide Documents Access Management System Accession No. ML21301A195), the Electric Power Research Institute (EPRI) Materials Reliability Program (MRP) submitted for U.S. Nuclear Regulatory Commission (NRC) review and approval topical Report (TR) No. 3002020105, "Materials Reliability Program: Pressurized Water Reactor [PWR]
Internals Inspection and Evaluation Guidelines (MRP-227, Revision 2), (Agencywide Documents Access and Management (ADAMS) Accession No. ML22129A141). EPRI MRP submitted the TR to support regulatory improvements related to the methodologies for inspecting and verifying the integrity of reactor vessel internal (RVI) components throughout the life of the plant, including the period of extended operation.
The TR contains the technical basis for the development of plant-specific aging management programs (AMPs) for RVI components in PWRs and provides inspection and evaluation (I&E) guidelines for PWR owners to use in their plant-specific AMPs to develop plant-specific inspection plans to manage aging effects on RVI components, as described by their final safety analysis report commitment.
By email dated December 1, 2022 (ADAMS Accession Nos. ML22335A491 and ML22335A513), the NRC forwarded EPRI the first set of requests for additional information (RAI). By letter dated April 4, 2023 (ADAMS Accession No. ML23095A049), EPRI provided response to the NRC staff first set of RAI (ADAMS Accession No. ML23095A050).
To complete its review, the NRC staff requests additional information as follows.
2.0 Regulatory Basis Part 54 of 10 CFR, "Requirements for Renewal of Operating Licenses for Nuclear Power Plants, addresses the requirements for the license renewal application. The regulation in 10 CFR 54.21, "Administrative review of applications; hearings," requires that each application for license renewal contain an integrated plant assessment (IPA) and an evaluation of time-limited aging analyses. The IPA shall identify and list those structures and components subject to an aging management review and demonstrate that the effects of aging (i.e., cracking, loss of material, loss of fracture toughness, dimensional changes, loss of preload) will be adequately managed so that their intended functions will be maintained consistent with the current licensing basis for the period of extended operation as required by 10 CFR 54.29, Standards of Issuance of a Renewed License.
2 3.0 Request for Additional Information RAI # 1 Background and Relevant Information: The clevis bearing Stellite wear surfaces and clevis insert bolts remain as Existing Program category components, through the inclusion of Item W14 in Table 4-9 of the TR, but with some modifications of the technical basis for inspecting the components from that established for the Item W14 of Table 4-9 in MRP-227, Rev. 1. In the TR, Item W14 credits the American Society of Mechanical Engineers Boiler and Pressure Vessel Code (ASME Code),Section XI, VT-3 visual inspection requirements as the condition monitoring basis for the clevis insert component. However, the TR allows Pressurized Water Reactor Owners Group (PWROG) Letter OG-21-160 to be used as an alternative non-destructive examination (NDE) option for performing ultrasonic testing (UT) of the components.
TR Item W14 designates that the clevis insert bolts would be managed only for the aging effect of cracking induced by a stress corrosion cracking mechanism (SCC) and the clevis bearing Stellite wear surfaces as being managed only for the aging effect or loss of material due to wear. However, recent PWR operating experience indicates that cracking may occur in the clevis insert dowel pins and has occurred in the clevis insert wear surfaces.
Issue and Request Part 1: The staff acknowledges that PWROG Letter OG-21-160 may provide relevant guidance for performing ultrasonic inspections for the clevis insert bolts or base metal.
However, the PWROG Letter OG-21-160 is not docketed as an official NRC record. If the guidance in PWROG Letter OG-21-160 can be used as an alternate NDE method for performing UT inspections of the clevis insert assembly components, the staff requests the PWROG Letter OG-21-160 be docketed as a supporting record in the ADAMS for the staffs review and processing of the TR.
Issue and Request Part 2: (a) Item W14 in TR Table 4-9 does not cite the clevis insert dowel pins as managed clevis insert assembly components even though there is operating experience with cracking of clevis insert assembly dowel pins. Justify why Item W14 in TR Table 4-9 does not include clevis insert assembly dowel pins among the set of clevis insert assembly components. (b) Given the operating experience of cracking in clevis bearing Stellite wear surface, clarify whether the listing of cracking in Item W14 covers potential cracking that may occur in the clevis bearing Stellite wear surfaces and whether additional cracking mechanisms (e.g., fatigue or irradiation-assisted stress corrosion cracking [IASCC]) need to be added to Item W14 in addition to SCC in the TR.
Issue and Request Part 3: The clevis insert assemblies are typically defined as a reactor vessel interior attachments under the ASME Code,Section XI, Table IWB-2500-1, Examination Category B-N-2. The clevis insert assembly serves a safety-related function for the core barrel assembly through bolted interactions with the reactor pressure vessel and configurational alignment interactions with the radial support keys. In light of operating experience reported to date for detected degradation in Westinghouse Electric Company (WEC)-design clevis insert assembly components, justify why the current I&E criteria defined for the TR Table 4-9 Item W14 clevis insert assembly components are considered to still be capable of managing the components prior to a loss of integrity and/or a loss of the intended support function of the clevis insert assembly.
3 RAI # 2 Background and Relevant Information: Section 4 I&E criteria items covering the three-tiered, susceptibility-ranked categories of Primary category baffle-former bolts (BFBs) based on bolt susceptibility fatigue, IASCC, irradiation embrittlement (IE), or irradiation-enhanced stress relaxation or creep (ISR/IC) are given in Items W6a, W6b, and W6c of TR Table 4-3. The acceptance criteria and sample-expansion criteria Primary BFB inspection results triggering potential sample-expansion to Expansion category core barrel to former bolts (Item W6.1 components) and lower support column bolts (Item W6.2 components) are given in Item W6 of TR Table 5-3. Item W6 in TR Table 5-3 includes a footnote Note 3, which redefines defective BFBs in clustered groupings (i.e., definition for BFB degraded clustered conditions) as follows:
A large cluster of degraded baffle-former bolts is defined as any group of adjacent baffle-former bolts at least 3 rows high by at least 10 columns wide, or at least 4 rows high by at least 6 columns wide where 80% or greater of the baffle-former bolts have unacceptable UT indications or are visibly degraded.
Note 3 in TR Table 5-3 identifies that this definition of clustered conditions is based on the EPRI MRP interim guidelines in MRP Letter 2018-002 (TR Reference 48), Transmittal of NEI-03-08 Needed Interim Guidance Regarding MRP-227-A and MRP-227, Revision 1 Baffle-Former Bolt Expansion Inspection Requirements for PWR Plants, dated January 17, 2018.
In 2017, EPRI MRP addressed the need for evaluating degraded BFBs with cracklike conditions in close proximity of one another (i.e., bolt degraded clustered conditions) in EPRI MRP Interim Guidance MRP Letter 2017-009, Transmittal of NEI-03-08 Needed Interim Guidance Regarding Baffle-Former Bolt Inspections for PWR Plants as Defined in Westinghouse NSAL 16
-01 Rev. 1, dated March 15, 2017 (TR Reference 78; ML17087A106). MRP Letter 2017-009 provided the original definition of BFB degraded clustered conditions and defined clustered conditions as: Clustering defined per NSAL-16-1 Rev.1: three or more adjacent defective BFBs or more than 40% defective BFBs on the same baffle plate. EPRI MRPs definition of BFB degraded clustered conditions in MRP Letter 2017-009 was the definition for clustered conditions approved in the staffs April 25, 2019, safety evaluation (ML19081A001) for MRP-227, Rev. 1/Rev. 1-A.
Issue and Request Part 1: The interim guidelines in MRP Letter 2018-002 have not been submitted for inclusion in the ADAMS as an official, publicly available NRC record. Therefore, if MRP Letter 2018-002 is to be relied upon as the source of the redefinition for BFB degraded clustered conditions in the TR, MRP Letter 2018-002 must be submitted for inclusion in the ADAMS. Therefore, the staff requests that MRP Letter 2018-002 be submitted as a publicly available record for inclusion in the ADAMS.
Issue and Request Part 2: The definition of BFB degraded clustered conditions in Note 3 of the TR and in MRP Letter 2018-002 varies significantly from the previous definition of BFB degraded clustered conditions in MRP Letter 2017-009. The staff must consider whether this change in definition is non-conservative. Specifically, in order for a group of defective BFBs to be considered as a clustered group of BFBs under the new definition in the TR Table 5-3, the population of BFBs with unacceptable cracklike conditions (defective bolts) would now have to be 80% of the total population of bolts in the assessed array (i.e., either an 4-by-6 array of BFBs in the baffle plate or 3-by-10 array of BFBs in the baffle plate, as defined in Note 3 in TR Table 5-3). This new definition is different from the 40% population of defective BFBs set for meeting clustered conditions in the definition provided in MRP Letter 2017-009. The new
4 definition for BFB clustered conditions in Note 3 and MRP Letter 2018-002 also appears to be eliminating the additional criterion for BFB degraded clustered conditions in MRP Letter 2017-009 which states that: three or more adjacent defective BFBs... Thus, the staff seeks the justifications regarding new definition for BFB degraded clustered conditions in Note 3 of TR Table 5-3:
(1) Clarify why a redefinition for BFB degraded clustered conditions is needed as shown in Note 3 of TR Table 5-3 from the prior definition for BFB degraded clustered conditions in MRP Letter 2017-009 (which is the current staff-approved definition).
(2) The definition in Note 3 of TR Table 5-3 references two different arrays representing total populations of assessed BFBs: (1) an array of BFBs at least 3 rows high and at least 10 columns wide, and (2) an array of BFBs at least 4 rows high and at least 6 columns wide. Explain why two different arrays of total BFB populations are specified.
Clarify whether this is representing two different designs of baffle plates.
(3) (a)For a proper comparison of the two definitions, the staff needs to have the population of defective BFBs for meeting degraded clustered conditions in terms of total number of defective bolts in close proximity groupings, and not the percentage of defective bolts in close proximity groupings. Therefore, for the definition in MRP Letter 2017-009, provide the total number of defective BFBs that represents the 40% population of defective BFBs in the same baffle plate. For the definition in Note 3 of TR Table 5-3 and in MRP Letter 2018-002, provide the total number of defective BFBs that represents the 80%
population of BFBs in the 3-by-10 array of bolts and the total number of defective BFBs that represents the 80% population of defective BFBs in the 4-by-6 array of bolts. (b)
Demonstrate that the total number of defective BFBs for the two arrays defined in Note 3 of TR Table 5-3 would still be an acceptable total number of defective BFB basis for triggering BFB degraded clustered conditions when compared to the total number of defective BFBs that would trigger BFB degraded clustered conditions for the definition provided in MRP Letter 2017-009.
- 4) Justify why the new definition in Note 3 of TR Table 5-3 does not include the additional criterion for defective BFBs in close proximity groupings as specified in MRP Letter 2017-009 which states: three or more adjacent defective BFBs...
- 5) Justify the validity of the new definition for BFB degraded clustered conditions in Note 3 of TR Table 5-3 as compared to the current staff-approved definition for BFB degraded clustered conditions in MRP Letter 2017-009, as previously approved in the staffs safety evaluation of April 25, 2019, for MRP-227, Rev. 1/Rev. 1-A.
RAI # 3 Background and Relevant Information: Item B20 in TR Table 4-1 includes criteria for managing cracking due to fatigue in B&W-design core barrel (CB) cylinder top flange circumferential weld regions using either enhanced visual (EVT-1), volumetric (UT), or eddy current test (ECT) NDE methods. The linked Expansion category component items for fatigue are cited as Item B20.1 (plenum cover weldment ribs-to-each other welds) and Item B20.2 (core support shield cylinder top flange) in TR Table 4-4. In the staffs previous RAI #MRP-227-B&W-2, the staff inquired why the scope of Primary components in TR Item B20 did not include the additional CB assembly components that were identified in TR Table 3-1 as screening in for fatigue through reference of a Primary or P screening ranking for fatigue.
5 In its response to RAI #MRP-227-B&W-2 (ML23095A050), EPRI MRP clarified that: (1) Note 2 of Table 3-1 of TR permits aging management of fatigue-induced cracking to be dispositioned by a fatigue analysis in lieu of inspection for the CB assembly welds, and (2) to eliminate the fatigue-based inspection need, a cumulative usage factor (CUF) calculation would need to be performed for the entire CB assembly (including flanges, cylinders, and associated vertical and circumferential seam welds), as was performed in relation to the staffs review of the subsequent license renewal application for Oconee Nuclear Station (ONS), Units 1, 2, and 3.
EPRI MRP stated that, if the calculated CUF value of the supplemental analysis meets the acceptance criteria on fatigue, the entire CB assembly would not need to be examined for fatigue.
The staff noted that the additional CB assembly components and welds that screen in as Primary for fatigue (i.e. in addition to the screening of the CB top flange-top cylinder circumferential weld regions in for fatigue) are: (1) the CB top and bottom cylinders and associate cylinders circumferential seam weld, (2) the CB cylinder top flange and associated top flange-to-top cylinder circumferential weld, (3) the CB cylinder bottom flange and associated bottom flange-to-bottom cylinder circumferential weld, and (4) the CB top and bottom cylinders vertical seam welds. The staff notes that there are additional technical or regulatory considerations that factor into this request as well. Foremost, the staff emphasizes that the original design bases for ONS Units 1, 2, and 3, the Davis Besse (DB) unit, and Arkansas Nuclear One, Unit 1 (ANO-1) did not require an ASME Code Section III CUF analysis to be performed as part of the current licensing basis (CLB) for the reactor internals. Thus, there is no fatigue analysis that could normally qualify as a 10 CFR 54.3(a)-defined time-limited aging analysis on fatigue for the CB assembly components and welds in the CLB for these units.
Thus, it would need to be a supplemental fatigue analysis that is performed for the CB assembly per the RAI response. EPRI MRP is not firmly establishing in Primary Item B20 that a supplemental fatigue analysis will need to be performed for the entire CB assembly. The omission of this type of information in Item B20 prevents the implementation of Item B20 as an NEI 03-08 Needed Requirement (i.e., as defined as a Needed Requirement in TR Section 7.3) from covering the remaining CB assembly base metal and weld components that screen in as Primary for fatigue in TR Table 3-1. Thus, the omission of the additional CB assembly components and welds in Primary Item B20 is contrary to EPRI MRPs response to RAI #MRP-227-B&W-2 that the entire CB assembly components and welds would require a fatigue analysis for disposition of fatigue.
Issue and Request Part 1: EPRI MRPs response to the staffs RAI #MRP-227-B&W-2 does not resolve the staffs concern whether the scope Primary Item B20 in TR Table 4-1 should include the remainder of CB assembly components or welds that screened in as screening ranking P for fatigue in TR Table 3-1 (See components referenced in the background and relevant information section of this RAI). Specifically, EPRI MRPs response to the staffs RAI
- MRP-227-B&W-2 acknowledges that a fatigue analysis is needed for all of the remaining CB assembly base metal and weld components, as they screened in for fatigue under screening ranking P in TR Table 3-1, and further, Primary Item B20 indicates that aging management of cracking by fatigue can be dispositioned by a fatigue analysis in lieu of inspection. Therefore, justify why the additional CB assembly components and welds (as referenced in the background and relevant information section of this RAI) do not need to be included within the scope of the Primary components listed and referenced in Primary Item B20 in TR Table 4-1.
Issue and Request Part 2: Implementation of Item B20 in TR Table 4-1 does not clearly cover how sample-expansion to the linked Expansion category plenum cover ribs-to-each other welds
6 (Expansion Item B20.1 components in TR Table 4-4) and Expansion category core support shield cylinder top flange (Expansion Item B20.2 component type in TR Table 4-4) will be accomplished as an NEI 03-08 Need Requirement if a fatigue analysis of the CB cylinder top flange circumferential welds regions or the entire CB assembly is used to manage fatigue under the criteria in Item B20 of TR Table 4-1 and the corresponding sample-expansion acceptance criteria (expansion triggering criteria) set forth in Item B20 of TR Table 5-3. Specifically, if disposition of cracking due to fatigue is accomplished by a fatigue analysis for the Primary CB assembly components, then there would be no inspection results available to determine whether sample-expansion to the Expansion Item B20.1 and B20.2 component types would be triggered per the acceptance criteria for inspection results applying to the Primary category CB cylinder top flange circumferential welds regions as defined in Item B20 of TR Table 5-3.
Item B20 of TR Table 5-3 lacks specific criteria for sample-expansion to the Expansion Item B20.1 and Item B20.2 if disposition of fatigue for the Primary CB assembly components is accomplished by an alternative fatigue analysis. Therefore, justify why TR Item B20 in TR Table 5-3 does not specify that, if the CB cylinder top flange circumferential weld (or the entire CB assembly) is dispositioned by alternate fatigue analysis under Item B20 in TR Table 4-3, the performed fatigue analysis would need to trigger EVT-1 visual inspections or a corresponding fatigue analysis of the plenum cover ribs-to-each other welds and core support shield cylinder top flange component types as the linked Expansion category components.
RAI # 4 Background and Relevant Information: Primary Items B16 and B17 in TR Tables 4-1 and 5-1 provide initial versions of I&E criteria and acceptance criteria and sample-expansion criteria for B&W-design Primary category CB cylinder top flange circumferential weld regions and Primary category CB cylinder center circumferential welds regions, respectively. Items B16 and B17 in TR Table 4-1 applies the enhanced visual (EVT-1), volumetric UT, or ECT methods mentioned in the B16 and B17 items to all remaining operating B&W plants, including Oconee Nuclear Station Units 1, 2, and 3 (ONS-1, ONS-2 and ONS-3), Arkansas Nuclear One, Unit 1 (ANO-1),
and DB, without any designation of linked Expansion category components. For the Primary weld types in the TR Table 4-1 B16 and B17 items (i.e., for both original and revised versions of the items), Items B16 and B17 indicate that the aging management disposition basis for the specified Primary weld types may be performed using an alternate analysis that the TR items (B16 and B17) indicate will be submitted to the NRC for approval.
EPRI MRPs responses to the staffs RAI #s MRP-227-B&W-3 and MRP-227-B&W-4 (as provided in the EPRI MRP letter of April 4, 2023) resulted in changes to Item B16 entry in TR Table 4-1 for the referenced Primary category B&W-design CB cylinder top flange circumferential weld regions and to Item B17 for the Primary category B&W-design CB cylinder center circumferential welds regions, along with some corresponding changes to the acceptance criteria and sample-expansion bases for these Primary weld types in Items B16 or B17 of TR Table 5-1. Of these changes, the most significant impact of changes to the I&E criteria, acceptance criteria, or sample-expansion criteria for the specified weld types is that only the CB cylinder top flange circumferential weld regions and CB cylinders center circumferential weld regions at ONS Unit 2 and ANO-1 are designated as Primary category components. The corresponding weld types at ONS Unit 1, ONS Unit 3, and DB (under new Items B16.1 and B17.1) are now categorized as Expansion category welds for the corresponding designation of the CB cylinder top flange circumferential weld regions and CB cylinders center circumferential weld regions at ONS-2 and ANO-1 as the linked Primary category welds.
7 The changes to TR Items B16 and B17 also add in and designate: (1) the Item B16.2 CB cylinder bottom flange circumferential weld regions at ONS-2 and ANO-1 as additional Expansion category welds for the Primary category (Item B16) CB cylinder top flange circumferential weld regions at ONS-2 and ANO-1, (2) the Item B17.2 CB cylinder vertical seam welds at ONS-2 and ANO-1 as additional Expansion category welds for the Primary category (Item B17) CB cylinder center circumferential weld regions at ONS-2 and ANO-1, (3) the Item B16.3 CB cylinder bottom flange circumferential weld regions at ONS-1, ONS-3, and DB as secondary Expansion components for the B16.1 Expansion category CB cylinder top flange circumferential weld regions at ONS-1, ONS-3, and DB, and (4) the Item B17.3 CB cylinder vertical seams welds at ONS-1, ONS-3, and DB as secondary Expansion components for the B17.1 Expansion category CB cylinder center circumferential weld regions at ONS-1, ONS-3, and DB.
This type of unit-to-unit sample-expansion basis is a new, first-of-a-kind Primary-to-Expansion sample-expansion basis which only sets up the CB cylinder top flange circumferential weld regions and CB cylinder center circumferential weld regions at ONS-2 and ANO-1 as designated Primary CB weld types for operating B&W plants. All other CB assembly welds at ONS-1, ONS-2, ONS-3, ANO-1, and DB are established as either first-tier or secondary-tier Expansion category welds. The revised B16 and B17 items in TR Table 4-1 and the new B16.1, B16.2, B16.3, B17.1, B17.2 and B17.3 items in TR Table 4-4 as proposed in the EPRI MRP letter dated April 4, 2023, only apply to 60 - 80 year periods.
Issue and Request 1: EPRI MRPs basis for setting up the Primary and Expansion inspection categorizations of B&W-design CB assembly welds is that a given CB weld type would only need to be designated as a Primary category weld if it were confirmed that the weld had been repaired after the unit had initiated successive plant operations from the original startup of the unit. This is based on EPRI MRPs rationale that the welds had been subject to a proprietary stress relief practice during the design and fabrication of the weld, which EPRI MRP states as making the welds less susceptible to SCC and IASCC mechanisms. While the staff did accept this original design stress relief practice as a stress mitigation practice and basis for inspection categorizations of B&W-design CB welds during first renewed 40 - 60 year periods, the staff informed EPRI MRP at the public meetings of May and November 2023 that the staff may not be accepting of this type of design practice as stress mitigation practice and a component-specific inspection categorization basis for B&W-design CB welds during subsequent renewed 60 - 80 year periods. This is based on the staffs observation that the industry has not provided the staff with any direct evidence that the magnitude of weld residual stress reductions imparted by an original weld stress relief practice would still hold true after exposing the CB assembly components to the additional cyclical stress cycles and neutron fluence exposures that are imparted through 80 years of cumulative power operations. Based on these considerations, provide any data, research, or publications that demonstrate that the stress relief process continues to provide more relief from SCC susceptibility during 60 - 80 years as compared to those that have not been stress relieved under cycles and irradiated conditions for the proposed revisions of TR Items B16 and B17, which limit the CB cylinder top flange circumferential weld regions and CB cylinder center circumferential weld regions at ONS-2 and ANO-1 as being the designated Primary category CB assembly welds for B&W-design PWRs during 60 - 80 year operating periods.
Issue and Request 2: The type of unit-to-unit sample-expansion basis for B&W-design CB assembly welds is a new, first-of-a-kind Primary-to-Expansion sample-expansion basis which only establish the CB cylinder top flange circumferential weld regions and CB cylinder center circumferential weld regions at ONS-2 and ANO-1 as designated Primary CB weld types for
8 operating B&W-designed PWRs. All other CB assembly welds at ONS-1, ONS-2, ONS-3, ANO-1, and DB are established as either first-tier or secondary-tier Expansion category welds.
As of the original version of the Primary items for Primary category B&W-design components in TR Table 4-1 and any Expansion items for linked Expansion category B&W-design components on TR Table 4-4, the sample-expansion bases for all Primary category components with linked Expansion category components in TR Table 5-1 were based on linked Primary and Expansion category components in the same unit of interest. The revised Item B16 and B17 criteria (as made in the April 4, 2023 letter) for the referenced B&W Primary category CB welds and the new B16.1, B16.2, B16.3, B17.1, B17.2, and B17.3 items for specified B&W Expansion CB weld types now would require sharing of inspection data between units, and in some cases between units owned by different licensees. However, TR Section 7 does not include any implementation criteria on how this unit-to-unit sharing of inspection data would be performed. This is particularly critical if the sharing of Primary B&W-design CB weld inspection data would need to be performed for units owned by different licensees (e.g., sharing of inspection data for the designated Primary CB welds at ONS-2 or ANO-1 and the linked Expansion category CB weld components at DB, or sharing of Primary inspection data for designated Primary CB assembly welds at ANO-1 and the linked Expansion category CB welds at ONS-2 and ONS-3). Given the lack of implementation criteria for unit-to-unit inspection data sharing practices in Section 7.3 of the TR, especially for units owned by different licensees, provide the details of the process, implementation criteria and reporting procedures for f the proposed revisions of TR Items B16 and B17 made in the April 4, 2023, letter Issue and Request 3: The proposed revisions to TR Item B16 and B17 (as made to the items in TR Table 4-1 and proposed in the EPRI MRPs letter dated April 4, 2023) would leave the DB facility without any CB assembly welds as designated Primary category welds. Therefore, the staff requests that: (1) EPRI MRP amend Items B16 and B17 in TR Tables 4-1 and 5-1 to include DB as third B&W unit whose CB cylinder top flange circumferential weld regions and CB cylinder center circumferential welds regions will be inspected as Primary weld components (i.e., in addition to designating these welds as Primary category welds for ONS-2 and ANO-1),
and (2) make the corresponding changes to the designated B16.1, B16.2, B16.3, B17.1, B17.2 and B17.3 Expansion category CB weld types based on designation of the ONS-2, ANO-1 and DB CB cylinder top flange circumferential weld regions and CB cylinder center circumferential welds regions as Primary category welds, or justify why CB assembly welds are not designated as Primary category weld components at DB.
RAI # 5 Background and Relevant Information: Primary Item C12 in TR Table 4-2 provides updated I&E criteria for performing enhanced visual (EVT-1) inspections of lower support structure (LSS) deep beams in CE-design units with welded core shroud (CS) assemblies utilizing full height shroud plates. Only 25 percent of the LSS deep beams are designated as the Primary components, with the remaining 75 percent population of LSS deep beams being the corresponding Expansion category components. The updated version of Primary Item C12 for the LSS deep beams is basically the same as that developed for Primary Item C12 in Table 4-2 of the MRP-227, Rev. 1-A, report, with the exception that the deep beams now screen in for two additional cracking mechanisms for the 80-year basis (i.e., SSC and IASCC in addition to fatigue and IE), whereas the prior version of Item C12 only screened the LSS deep beams in for fatigue and IE. The staff notes that the updated version of Item C12 in TR Table 4-2 continues to maintain the same Examination Method/Frequency criteria for the LSS deep beams as in MRP-227, Rev. 1-A.
9 Issue and Request Part 1: It is not evident whether the updated I&E criteria for LSS deep beams in Item C12 of TR Table 4-2 are calling for either: (1) an initial base-line inspection of the 25%
deep beam locations after entering into the 40 - 60 year period of extended operation, and then an additional base-line inspection upon entry into the 60 - 80 year subsequent period of extended operation, where only the subsequent reinspections in those periods could be potentially be bypassed using an acceptable analysis, or (2) just setting up an initial base-line inspection of the 25% deep beam locations after entering into the 40 - 60 year period of extended operation, and then potentially bypassing any subsequent reinspections using the results of an acceptable component analysis (i.e., no additional base-line inspections of the 25%
population of Primary category LSS deep beams during the 60 - 80 year subsequent period of extended operation would be performed). Therefore, clarify whether Primary Item C12 in TR Table 4-2 is establishing an additional base-line inspection for the 25% population of LSS deep beams that are the Primary components.
Issue and Request Part 2: For reinspection considerations, the updated version of Primary Item C12 in TR Table 4-9 calls for subsequent examination at a 10-year interval if adequacy of remaining fatigue life cannot be demonstrated. This appears to imply that any component-specific analysis to eliminate reinspections of the Primary population of deep beams would only have to be a successful fatigue analysis for the components. However, the staff noted that the LSS deep beams also screen in for SCC, IASCC and IE mechanisms for the 60 - 80 year period. Therefore, justify why the alternate to reinspection option using a component-specific analysis of the deep beams would not have to cover all aging mechanisms that the LSS deep beams screen in for the 60 - 80 year period (i.e., covering fatigue, SCC, IASCC, and IE mechanisms during the subsequent period of extended operation).
Issue and Request Part 3: In evaluating whether a successful component-specific analysis of the LSS deep beams could be used as an alternate aging management option basis in lieu of reinspections, the staff considered whether this type of alternate aging management strategy is still acceptable for the additional period of service that would be incurred during a 60 - 80 year subsequent period of extended operation. This includes considerations of the additional number of fatigue cycles, time at temperature, and neutron fluence exposures that would be incurred to the LSS deep beams during 60 - 80 years. When it comes to reinspection bases for other Primary designated components in the TR, EPRI MRPs citation of alternate disposition by analysis options are only cited as alternate aging management options for extending the periodicity of the specified reinspection interval for the Primary category component type defined in the TR Section 4 table item; For these TR table items, EPRI MRP specifies the analysis used for extending the periodicity of the inspection interval will be submitted for NRC review and approval. (a) Thus, for Year 60 - 80 considerations of the LSS deep beams, justify why the alternate disposition by component-specific analysis option is being used as a potential basis for eliminating reinspections of the Primary LSS deep beam population rather than using this alternate option to extend the periodicity of the reinspection interval beyond a 10-Year basis. (b) Justify why the component-specific analysis for the LSS deep beams would not need to be submitted to the NRC for review and approval similar to EPRI MRPs disposition by alternate analysis options that are included other TR Section 4 table items applying to PWR Primary category components (where EPRI MRP dictates the analysis is to be submitted to the NRC for approval).
10 RAI # 6 Background and Relevant Information: Currently, EPRI MRP designates WEC-design CB upper girth welds (UGWs) as WEC-design Expansion category welds per the I&E criteria in Item W3.1 of TR Table 4-6.
Issue and Request: At least one WEC-designed PWR has experienced and reported significant cracking in the CB UGW. It appears that the TR has not addressed the latest operating experience of cracking in WEC-design CB UGWs which are subject to the new interim guidelines in EPRI MRP Letter 2023-005, dated May 19, 2023,
Subject:
NEI 03-08 Needed Interim Guidance for WEC/CE Core Barrel Inspections, (ML23290A019).
(a) Confirm that MRP-227, Rev. 2 (when it is submitted for the staffs final approval to include in the ADAMS) will include the requirements that the WEC-design CB UGW is designated as a Primary component in the CB assembly category and the inspection of the UGW will be performed consistent with the new criteria for the weld type in EPRI MRP Letter 2023-025.
(b) Confirm that that MRP-227, Rev 2 (when it is submitted for the staffs final approval to include in the ADAMS) will be revised to identify the corresponding Expansion category components or welds and the associate new TR Section 5 acceptance criteria and sample-expansion criteria for the CB UGW as Primary category weld, as defined and established in MRP Letter 2023-005.
RAI # 7 Background and Relevant Information: EPRI MRP addresses management of loss material due to wear in WEC-design control rod drive mechanism (CRDM) thermal sleeves in Existing Program Item W21a of Table 4-9 in the TR.
Issue and Request: Item W21a in TR Table 4-9 specifies implementation of a proprietary NDE method for inspection of the thermal sleeves as defined in PWROG Proprietary Report No.
PWROG-16003-P, Rev. 2, Evaluation of. Potential Thermal Sleeve Flange Wear, dated May 2019). The proprietary NDE method is not listed among the NDE methods discussed in TR Section 5 or in MRP-228, Rev. 4, which was used in the development of the NDE methods discussed and invoked in the TR. Additionally, PWROG-16003-P, Rev. 2 has not been submitted for inclusion as an official, non-public, 10 CFR 2.390-protected record in the ADAMS.
Due to a lack of information, the NRC staff has no basis to conclude that use of this proprietary NDE method would be capable of detecting loss of material due wear in the thermal sleeves prior to loss of intended function. (a) Submit the technical basis and justify the use of the proprietary NDE method that will be used to examine the thermal sleeves per the guidance in PWROG-16003-P, Revision 2. As part of this, describe and explain how the proprietary NDE method cited in PWROG-16003-P, Revision 2 can detect and disposition evidence of wear occurring in the thermal sleeves or in the CRDM adapter housings or nozzles associated with the thermal sleeves. (b) Submit PWROG-16003-P, Revision 2 for inclusion in ADAMS, as a non-public, proprietary record per 10 CFR 2.390 requirements.
RAI # 8 Background and Relevant Information: Appendix C of the TR provides a summary of regulatory and technical factors that may need to be considered if an alternate aging management strategy is considered from the defined I&E criteria for age-managed PWR RVI category components in
11 TR Section 4 or the corresponding acceptance criteria or sample-expansion criteria for the component type in TR Section 5. TR Appendix C does not provide specific alternative aging management strategies for specific PWR RVI component types.
Issue and Request: The staff considers that the inclusion of Appendix C in the TR could potentially set a precedent that if the TR is approved by the staff, a licensee implementing the staff-approved TR would be able to use TR Appendix C to propose an alternative aging management strategy that deviates from the specified I&E criteria for a managed Primary, Expansion or Existing Program RVI component in TR Sections 4 and/or 5 without any possibility of an NRC review on the proposed alternate aging management strategy. Therefore, justify the basis for the inclusion of Appendix C in the TR. Clarify whether inclusion of TR Appendix C in the TR and implementation of the alternative aging management strategy in TR Appendix C may be used by a licensee to prevent any NRC review of a component-specific alternate aging management strategy that is proposed and implemented under the criteria defined in TR Appendix C. Justify why the staff should approve TR Appendix C if development and implementation of a component-specific alternate aging management under TR Appendix C can be interpreted by licensee as preventing any NRC review of the alternate aging management strategy.
RAI # 9 Background and Relevant Information: Items C18 of TR Tables 4-2 and 5-2, specify non-qualified visual inspection to manage loss of material due to wear and loss of preload due to irradiation-enhanced stress relaxation or creep in CE-design CS tie rods and nuts for CE-design plants with CSs containing these types of tie rod assemblies.
Issue and Request: Use of non-qualified visual inspection methods is only generally discussed in TR Section 5 and is not defined in MRP-228, Rev. 4. The NRC staff does not have sufficient information as to procedural controls and acceptance criteria that will be applied to the non-qualified visual inspection methods that will be used for examining the CS tie rods and nuts per the I&E criteria in Item C18 of TR Table 4-2. Specifically, the corresponding acceptance criteria for conditions monitored by non-qualified visual methods on Item C18 of TR Table 5-2 do not provide any quantitative criteria on the number of broken tie rod locking tabs, missing tie rod nuts that could be tolerated, or on the degree of displacement or amount of wear that could be tolerated in the CS tie rods. Describe the inspection procedures and the quantitative acceptance criteria that will be used for the non-qualified visual inspections that will be performed on the CE-design core shroud tie rods and nuts per the Item C18 in TR Tables 4-2 and 5-2.