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Federal Register / Vol. 86, No. 20 / Tuesday, February 2, 2021 / Proposed Rules NUREG2228, Weld Residual Stress Finite Element Analysis Validation: Part IIProposed Validation Procedure, because it provides a proven method for validating the weld residual stress analysis methodology. Because the NRC
requires the use of NUREG2228 within this condition on the requirements in the Code Case, the NRC is incorporating by reference NUREG2228 into 50.55aa3iv.
The fifth condition is related to the longer term volumetric inspection frequencies of Table 1, including notes 1, 3, and 4. These notes provide the BWR design inspection frequency of various EWR types based on Generic Letter 8801 1988 as supplemented by Generic Letter 8801, Supplement 1
1992, NRC Position on Intergranular Stress Corrosion Cracking IGSCC in BWR Austenitic Stainless Steel Piping or BWRVIP75A, BWR Vessel and Internals Project Technical Basis for Revisions to Generic Letter 8801
Inspection Schedules. The NRC has concluded that the inspection requirements for EWRs for BWRs need to be augmented.
The first volumetric examination following application of BWR EWR2A, EWR1B, and EWR2B welds is performed to verify effectiveness of the repair/mitigation before the new weld can be placed in a longer term volumetric inspection frequency. The Code Case allows licensees the option of performing this examination during the first or second refueling outage after installation. However, based on the lower operating temperatures of a BWR
approximately 546 degree F to 558
degree F, and hence the potential slow crack growth rate of the remaining flaw left in service, the NRC has concluded that the examination should occur during the second refueling outage after the EWR application to provide adequate time for any potential measurable flaw growth to occur or in the case of an EWR2A, for crack initiation and growth to occur.
The long term volumetric inspections for BWRs require modification because:
a For EWR1A EWRs, the augmented inspection requirements are consistent with the conditions of the inspection frequencies of Code Case N7705.
These inspection frequency requirements were previously developed by the NRC based on the capabilities of the EWR process to address stress corrosion cracking while providing significant credit for the use of hydrogen water chemistry/noble metal chemical addition controls; and b for EWR1B EWRs, due to the design which would allow a crack to be left in service, should not be allowed to go
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uninspected for the remainder of plant life. Therefore, the NRC requires the long term volumetric inspection of these welds at each 10-year inservice inspection interval. The NRC notes that this condition is consistent with the NRC condition established in 50.55a for Inspection Item N1 EWRs EWR
that meets stress criteria; however, a crack is present.
The sixth condition is related to Table 1, Note 1, and the option to use an unspecified alternative to determine examination frequencies and scope expansion criteria. Note 1 specifies the use of NRC Generic Letter 8801 and includes BWRVIP75A as an example of an alternative. The NRC has concluded that NRC Generic Letter 88
01, 1988 as supplemented by Generic Letter 8801, Supplement 1 1992, or BWRVIP75A, represent sufficient requirements, subject to the fifth condition above, to determine examination frequencies and scope expansion criteria. However, Note 1
would allow the use of other, unknown alternatives and does not provide criteria to ensure alternatives are adequate for this purpose. Therefore, to ensure that licensees use an adequate standard to determine examination frequencies and scope expansion criteria, the sixth condition requires that licensees must not use an alternative other than those specified in Note 1.
Code Case N864 Supplement 2, 2017
Edition Type: New.
Title: Reactor Vessel Threads in Flange Examinations, Section XI, Division 1.
Code Case N864 proposes to eliminate the required ASME Code, Section XI examination for the reactor vessel threads-in-flange for all inservice inspection intervals. The NRC has previously granted alternatives under 50.55az that eliminate the reactor pressure vessel threads-in-flange examinations ASME Section XI, Examination Category BG1, Item No.
B6.40 for up to two inservice inspection intervals through the NRCs alternative request process. For alternatives that requested elimination of the examination for a second consecutive ten-year inservice inspection interval, the NRC has been requesting additional information on activities performed to ensure that the condition of the reactor pressure vessel threads-in-flange receives some level of monitoring. These activities typically have been care and maintenance of the reactor vessel threads-in-flange and studs whenever the closure head is removed. The NRC has limited approval
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of such requests to two subsequent inservice inspection intervals because the NRC has determined that complete elimination of the examinations does not provide adequate protection against long-term degradation of the threads-inflange. The NRC is proposing conditions on the use of Code Case N864 that are consistent with the limits the NRC has placed on similar alternatives requests.
The first proposed condition in Code Case N864 requires that the reactor pressure vessel threads-in-flange examinations ASME Section XI, Examination Category BG1, Item No.
B6.40 must be performed in at least every third 10-year ISI interval. The first proposed condition also limits the application of Code Case N864 at facilities that have been authorized under 10 CFR 50.55az to use alternatives that eliminate reactor pressure vessel threads-in-flange examinations to ensure that the required examination is performed at least every third 10-year inservice inspection interval.
The second proposed condition in Code Case N864 ensures that sufficient monitoring and maintenance activities are performed when the Code Case is applied.
Code Case N869 Supplement 6, 2017
Edition Type: New.
Title: Evaluation Criteria for Temporary Acceptance of Flaws in Class 2 or 3 Piping, Section XI, Division 1.
Code Case N869 contains provisions for temporary acceptance of flaws, including through-wall flaws in Class 2
or 3 piping including elbows, pipe bends, reducers, and branch tees, whose maximum operating pressure is greater than 275 psig, and does not exceed 600
psig, without performing a repair/
replacement activity. The Code Case contains provisions regarding the scope, flaw characterization, periodic leakage monitoring, flaw evaluation, and augmented examinations. The NRC
finds that the Code Case provides reasonable assurance that structural integrity of degraded piping will be maintained until the next scheduled refueling outage. However, the NRC
finds that the augmented examination provisions in Section 5 of the Code Case are inadequate and need additional requirements.
When a licensee applies N869 to disposition a through-wall leak or wall thinning in a piping system, Section 5
of the Code Case requires augmented examinations for flaws and significant flaws. The augmented examination
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