ML24169A409
| ML24169A409 | |
| Person / Time | |
|---|---|
| Site: | Fermi  |
| Issue date: | 07/18/2024 |
| From: | Jeffrey Whited Plant Licensing Branch III |
| To: | Peter Dietrich DTE Electric Company |
| Arora S | |
| References | |
| EPID L-2023-LLR-0042 | |
| Download: ML24169A409 (1) | |
Text
July 18, 2024
Peter Dietrich Senior Vice President and Chief Nuclear Officer DTE Energy Company Fermi 2 - 26 0 TAC 6400 North Dixie Highway Newport, MI 48166
SUBJECT:
FERMI 2 - RELIEF REQUEST RR-A25, ALTERNATIVE TO REACTOR VESSEL CIRCUMFERENTIAL SHELL WELD EXAMINATIONS (EPID L-2023-LLR -0042 )
Dear Peter Dietrich:
By letter dated August 4, 2023, Agencywide Documents Access and Management System (ADAMS) Accession No. ML2 3216 A187, DTE Energy Company (DTE) submitted alternative request RR-A25 to the U.S. Nuclear Regulatory Commission ( NRC). The proposed alternative requests elimination of the full ultrasonic examination of the r eactor pressure vessel (RPV) circumferential shell welds for the period of extended operation of Fermi 2.
Specifically, DTE requested the alternative pursuant to Title 10 of the Code of Federal Regulations (10 CFR) part 50, s ection 50.55a(z)(1), on the basis that the alternative provides an acceptable level of quality and safety. T he alternative requested relief from circumferential weld examinations required by the ASME (American Society of Mechanical Engineers) Code, from the current fourth inservice inspection interval through the period of extended operation. The DTE also stated in its request that Fermi 2 will continue to perform volumetric examinations of essentially 100 percent of the RPV longitudinal shell welds and that a portion of the circumferential welds will be volumetrically examined at their points of intersection with the longitudinal welds.
The NRC staffs evaluation of the proposed alternative request concludes that DTE has adequately addressed all of the regulatory requirements set forth in 10 CFR 50.55a( z)(1). Based on its review, the NRC staff approves use of the proposed alternative for the welds included in RR-A25 through the period of extended operation ending on March 20, 2045.
All other ASME Code,Section XI, requirements for which the relief was not specifically requested and approved in this request remain applicable, including the third-party review by the Authorized Nuclear Inservice Inspector.
P. Dietrich
If you have any questions, please contact the Project Manager, at 301-415-1421 or e-mail at Surinder.Arora@nrc.gov.
Sincerely,
Jeffrey A. Whited, Chief Plant Licensing Branch III Division of Operating Reactor Licensing Office of Nuclear Reactor Regulation
Docket No. 50-341
Enclosure:
Safety Evaluation
cc: ListServ
SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION
RELIEF REQUEST RR-A25
ALTERNATIVE REQUIREMENTS FOR REACTOR PRESSURE VESSEL
CIRCUMFERENTIAL WELD EXAMINATIONS
DTE ELECTRIC COMPANY
FERMI 2
DOCKET NO. 50-341
1.0 INTRODUCTION
By letter dated August 4, 2023 (Agencywide Documents Access and Management System Accession No. ML23216A187 ), DTE Electric Company (DTE, the licensee) submitted a request to the U.S. Nuclear Regulatory Commission (NRC) for the use of the alternative to examination requirements of the American Society of Mechanical Engineers Boiler and Pressure Vessel Code (ASME Code), s ection XI, Rules for lnservice Inspection [ISI] of Nuclear Power Plant Components, applicable to the reactor pressure vessel (RPV) circumferential shell welds at Fermi 2. The licensees proposed alternative is identified as relief request RR -A25 and the request for the use of this alternative was submitted pursuant to Title 10 of the Code of Federal Regulations (10 CFR) 50.55a(z)(1) on the basis that the alternative would provide an acceptable level of quality and safety.
The proposed alternative would eliminate the requirement to inspect the RPV circumferential shell welds, except for the areas of intersection with the axial welds, for the extended license term at Fermi 2, also referred to as the period of extended operation (PEO). The licensees proposed alternative addressed the specific guidance referenced in NRCs Generic Letter (GL) 98-05, Boiling Water Reactor Licensees Use of the BWRVIP -05 Report to Request Relief from Augmented Examination Requirements on Reactor Pressure Vessel Circumferential Shell Welds (ML031110082). This specific guidance provides staff expectations and acceptance criteria for plant-specific applications for ASME Code alternatives to implement the Boiling Water Reactor Vessel and Internals Project (BWRVIP) topical report BWRVIP -05, BWR Reactor Pressure Vessel Shell Weld Inspection Recommendations (proprietary) probabilistic fracture mechanics (PFM) methodology in lieu of the subject RPV circumferential shell weld examinations.
2.0 REGULATORY EVALUATION
Pursuant to 10 CFR 50.55a(g)(4), lnservice inspection standards requirement for operating plants, ASME Code Class 1, 2, and 3 components (including supports) must meet the requirements, except the design and access provisions and the preservice examination requirements, set forth in the ASME Code, s ection XI, to the extent practical within the limitations of design, geometry, and materials of construction of the components. The regulations require that inservice examination of components and system pressure tests conducted during the first 10-year ISI interval and subsequent intervals comply with the requirements in the latest edition and addenda of s ection XI of the ASME Code incorporated by reference in 10 CFR 50.55a(a)(1)(ii), 18 months prior to the start of the 120-month interval, subject to the conditions listed in 10 CFR 50.55a(b)(2).
GL 98-05 provides recommendations for licensees planning to request permanent relief from the ISI requirements of 10 CFR 50.55a(g) for the volumetric examination of RPV circumferential welds. The recommendations include the need for licensees to perform their required inspections of essentially 100 percent of all axial welds. These recommendations are only applicable to the remaining term of operation under the initial existing license.
Pursuant to 10 CFR 50.55a(z), Alternatives to codes and standards requirements, alternatives to the requirements of paragraph (g) may be used, when authorized by the NRC, if (1) the proposed alternatives would provide an acceptable level of quality and safety, or (2) compliance with the specified requirements would result in hardship or unusual difficulty without a compensating increase in the level of quality and safety.
3.0 TECHNICAL EVALUATION
3.1 Licensees Relief Request RR-A25
3.1.1 Components for Which the Alternative is Requested
Code Class: 1 Examination Category: B-A Item No: B1.11
==
Description:==
RPV Circumferential Pressure Retaining Shell Welds Weld Nos.: 4-308A, 4-308B, 1-313, and 9-307
3.1.2 Applicable Code Edition and Addenda
The Fermi 2 ISI Program is in its fourth ten-year interval. The applicable code is the ASME Code,Section XI, 2013 Edition. The licensee stated that the applicable code will be updated in future intervals in accordance with 10 CFR 50.55a(g)(4)(ii).
3.1.3 ASME Code Requirements
The ASME Code, s ection XI, 2013 Edition, Table IWB-2500-1, Examination Category B -A, Item No. B1.11, requires a volumetric examination of essentially 100 percent (i.e., greater than 90 percent) of the length of all the RPV circumferential shell welds during each ISI interval.
3.1.4 Reason for Licensees Request
The licensee proposed to forego examining RPV circumferential welds from the current fourth ISI interval through the PEO. The licensee stated that it will continue to perform volumetric examinations of essentially 100 percent of the RPV longitudinal shell welds and a portion of the circumferential welds will be volumetrically examined at their points of intersection with the longitudinal welds. As documented in s ection 4.2.5 Reactor Vessel Circumferential Weld Examination Relief, of NUREG -2210, Safety Evaluation Report Related to the License Renewal of Fermi 2 (ML16356A234), the NRC has concluded that the evaluation for the t ime limiting aging analysis (TLAA) for Fermi 2s RPV circumferential welds is acceptable because (1) the 52 effective full power years (EFPY) conditional failure probability will remain bounded by the NRC analysis in the staffs safety evaluation report (SER) dated July 28, 1998, approving BWRVIP-05 (proprietary package ML20236V551), and (2) the licensee will be using procedures and training to limit cold overpressure events during the period of extended operation. The NRC staff stated that the analysis is consistent with the evaluation criteria in the staffs SER for BWRVIP-05. The staff further stated that the applicant is still required to request relief from RPV circumferential weld examination requirements for ISI intervals over the extended period of operation in accordance with 10 CFR 50.55a.
3.1.5 Licensees Proposed Alternative
In lieu of the inspection requirements of the ASME Code, s ection XI, table IWB -2500-1, the licensee has proposed to eliminate the examination of the RPV circumferential shell welds through the PEO. The licensee also proposes to continue performing volumetric examinations of essentially 100 percent of the RPV axial shell welds, and the RPV circumferential welds at their points of intersection with the RPV axial shell welds.
3.1.6 Licensees Basis for the Proposed Alternatives
The licensees technical basis for determining an acceptable level of quality and safety included plant-specific evaluations for demonstrating that the limiting RPV circumferential shell weld at Fermi 2 has conditional failure probabilities that are bounded by (i.e., less than) the NRC staffs acceptance criteria for the weld failure probabilities, considering projected RPV circumferential weld embrittlement through the end of the PEO. The staffs specific acceptance criteria for these circumferential shell weld failure probabilities were established in its final SE dated July 28, 1998, for the BWRVIP-05 report.
The licensee noted that, as documented in s ection 4.2.5 of NUREG-2210, the NRC staff previously found that Fermi 2 submitted analyses for the PEO consistent with the evaluation criteria in the NRCs final SE for BWRVIP-05 but the licensee is still required to request relief in accordance with 10 CFR 50.55a for ISI intervals in the PEO.
3.1.7 Duration of Proposed Relief Alternative
The licensee stated that the duration of this request is for the remainder of the Fermi 2 extended license ending on March 20, 2045.
3.2 NRC Staff Evaluation
=
Background===
By letter dated September 28, 1995 (ML20098B288), the Boiling Water Reactor Owners Group (BWROG) submitted topical report BWRVIP-05, via the Electric Power Research Institute (EPRI). Parts of the topical report (TR) can also be found in EPRI TR -105697, BWR Reactor Pressure Vessel Shell Weld Inspection Recommendations, September 1995 (BWRVIP -05)
(ML032200246). The TR provides the technical basis for eliminating inspections of RPV circumferential shell welds in BWR (boiling-water reactor) plants. In its review of BWRVIP -05, the NRC staff performed an independent PFM analysis to estimate RPV failure probabilities. In its associated safety evaluation (SE) dated July 28, 1998 (ML20236V550, proprietary), the NRC staff approved the generic use of BWRVIP-05 and concluded that BWR licensees may request relief from examination of RPV circumferential shell welds by satisfying the following two criteria:
- Criterion 1 - At the expiration of the operating license, the circumferential welds will continue to satisfy the limiting conditional failure probability for circumferential welds in the staffs July 28, 1998, SE.
- Criterion 2 - Licensees have implemented operator training and established procedures that limit the frequency of cold over-pressure events to the amount specified in the staffs July 28, 1998, SE.
Subsequently, in 1998, the NRC staffissued GL 98-05 permitting BWR licensees to request permanent relief from the examination of RPV circumferential welds, if the above two criteria are satisfied.
By letter dated August 19, 1999 (ML9908250188), DTE had submitted initial request No. RR-A25 to forgo the examination of the RPV circumferential welds at Fermi 2 for the 40-year license. By letter dated March 30, 2000 (ML003697623), the NRC staff had approved the initial RR-A25.
By letter dated September 21, 1999, BWRVIP submitted for NRC review and approval TR BWRVIP-74, BWR Vessel and Internals Project: BWR Reactor Pressure Vessel Inspection and Flaw Evaluation Guidelines for License Renewal.By letter dated October 18, 2001, the staff
approved for generic use TR BWRVIP-74-A (package ML031710354; Non-proprietary ML031710343; and proprietary ML031710349). BWRVIP-74 -A demonstrates that NRC-approved inspection, flaw evaluation and aging management programs of the BWR vessel for the current operating license are also adequate for a 20-year license renewal term. The NRCs SE (ML012920549) approving TR BWRVIP A specifies action items for license renewal applicants for the PEO with regard to the RPV circumference weld inspections. BWRVIP-74-A provides a technical basis for the elimination of RPV circumferential weld examination for the PEO. Item 11 in section 4.1, Renewal Applicant Action Items, of the SE for BWRVIP-74-A states that a licensee may obtain relief from the ISI of the circumferential welds during the PEO by demonstrating that (1) at the end of the renewal period, the circumferential welds will satisfy the limiting conditional failure frequency for circumferential welds in the a ppendix E of the NRC staffs July 28, 1998, final SE for BWRVIP-05 and (2) that the licensee has implemented operator training and established procedures that limit the frequency of cold overpressure events to the amount specified in the staffs final SE.
By letter dated April 24, 2014 (ML14121A554), the licensee submitted Fermi 2 license renewal application for the PEO. Section 4.2.5, Reactor Vessel Circumferential Weld Inspection Relief, of the Fermi 2 license renewal application (ML14121A536) discusses the TLAA associated with the elimination of the RPV circumferential weld examination. In December 2016, the NRC published its SER approving the Fermi 2s license renewal application in NUREG-2210.
Section 4.2.5 of NUREG-2210 concludes that the licensees TLAA for RPV circumferential welds is acceptable for the PEO because the NRC staff finds that DTE has demonstrated, pursuant to 10 CFR 54.21(c)(1)(iii), that the effects of cracking on the intended functions of the RPV circumferential welds will be adequately managed for the period of extended operation. In NUREG-2210, the NRC staff noted that: (a) the applicant has demonstrated that the conclusions of the BWRVIP-05 report are applicable to and valid for the design of the RPV circumferential welds at Fermi 2 during the period of extended operation. (b) the applicant plans to reapply for relief from the ISI requirements for the RPV circumferential welds during the period of extended operation in accordance with 10 CFR 50.55a.
Request No. RR-A25 Submittal
The NRC staff evaluated whether request RR-A25 is based on plant-specific implementation of the NRC-approved BWRVIP -05 methods for the limiting circumferential shell weld at Fermi 2, considering projected RPV weld neutron embrittlement through 52 years of facility operation.
NRC approval for the BWRVIP-05 states that the conditional failure probability of the limiting RPV circumferential shell weld at the end of plant license needs to be less than the conditional failure probability for the limiting generic circumferential shell weld in the NRCs final SE for BWRVIP-05.The conditional failure probability is based on the RPV shell weld embrittlement consideration.
The specific RPV weld embrittlement parameter used for the NRC staffs evaluation is referred to as the mean adjusted RTNDT (ART). The mean ART value for demonstrating an acceptable RPV weld conditional failure probability is calculated based on the following inputs:
(1) The Projected RPV Neutron Fluence: RPV neutron fluence, as determined based on staff-approved calculation methodologies, is the key time-dependent parameter for all RPV integrity analyses that consider neutron embrittlement of the RPV beltline materials.
The projected neutron fluence input to the mean ART value, for demonstrating an acceptable RPV weld conditional failure probability at the end of the licensed operating term, shall include the effects of any power uprates that are implemented during the licensed operating term of the unit.
(2) The Weld Chemistry Factor (CF): The CF is determined based on both copper and nickel content in the RPV circumferential weld, or the application of credible RPV material surveillance data from a RPV material surveillance program in accordance with 10 CFR Part 50, Appendix H. If the weld is represented in the plant-specific or industry integrated surveillance program, all credible RPV surveillance data shall be used for the CF calculation per the requirements of 10 CFR Part 50, Appendix G and guidance of Regulatory Guide (RG) 1.99, Revision 2. CF values shall be periodically recalculated based on new credible RPV surveillance data that becomes available when a surveillance capsule is withdrawn from the RPV and tested in accordance with 10 CFR Part 50, Appendix H.
(3) The Initial (Unirradiated) RTNDT: The initial RTNDT is determined in accordance with the requirements of 10 CFR Part 50, Appendix G, based on the procured RPV material impact test data or the use of NRC-approved methods in NUREG-0800, Branch Technical Position 5-3, Revision 2, Fracture Toughness Requirements, dated March 2007 (ML070850035), as applicable to the unit. This is expected to remain fixed throughout the operating life of the plant.
(4) The RTNDT: The initial RTNDT of the RPV will be increased as a result of neutron fluence irradiation. This increase is designated as RT NDT, which is a product of a CF and a fluence factor as specified in RG 1.99. The fluence factor is dependent upon the neutron fluence predicted to the end of 60 years.
In the evaluation of RR-A25, the mean ART is the combination of the initial RT NDT and RTNDT.
RG 1.99 specifies a margin term in calculating the ART. However, the margin term was not considered in the evaluation of RR-A25 because the mean ART and RT NDT values were used in the NRCs final SE for BWRVIP-05.
The NRC staff evaluated request No. RR-A25 with respect to the staffs SE for BWRVIP-05 to determine whether the proposed request complies with the above two criteria.
Criterion 1 - Conditional Failure Probability of Fermi 2 RPV Circumferential Welds
The BWRVIP-05 report states that the mean ART value is the parameter that is used to assess the degree of embrittlement in RPV circumferential welds affected by neutron fluence irradiation.
In the final SE for BWRVIP-05, the NRC staff independently calculated generic mean ART values of welds in the RPV fabricated by various vendors per RG 1.99. The NRC staff compared its calculated generic mean ART values with the ART values calculated by BWRVIP-05. The staff noted that the mean ART values are used to calculate the conditional probability of failure of RPV circumferential welds. The higher the mean ART value of the RPV
circumferential weld, the higher the conditional failure probability because a higher mean ART value implies that the RPV circumferential weld is embrittled more than a lower mean ART and, therefore, has a higher failure probability. The NRCs final SE for BWRVIP-05 concludes that the conditional failure probability for site-specific RPV circumferential welds is adequately bounded and acceptable if the limiting mean ART of the limiting site-specific RPV circumferential weld is less than or equal to the generic mean ART calculated as shown in the staffs SE for BWRVIP-05.
In response to Criterion 1, the licensee provided the key parameters that affect the mean ART of the subject RPV circumferential welds during plant operation. These key parameters are neutron fluence, weld chemistry, initial RT NDT and RTNDT. The licensee derived these key parameters for the limiting RPV circumferential weld 1-313 at Fermi 2 and compared them to the corresponding parameters used for the limiting generic circumferential weld in the NRCs final SE for BWRVIP-05 as shown in table 1 of request No. RR-A25. The licensee stated that Fermi 2s RPV is fabricated by Combustion Engineering (CE). The NRCs final SE for BWRVIP-05 calculated two different chemistry factors for the limiting generic weld based on BWRVIP -05 data and CE BWROG data.
As shown in table 1 of request N o. RR-A25, the licensee calculated the mean ART for the limiting circumferential weld 1-313 using (1) an initial RTNDT of - 50 (minus 50) degrees Fahrenheit (°F), (2) an inside diameter neutron fluence value of 5.74E17 neutron/centimeter2 (n/cm2) at 52 EFPY, (3) a weld CF of 236ºF, and (4) a RTNDT value of 59 ºF. Based on these key parameters, the licensee calculated a limiting mean ART of 9 ºF for the limiting RPV circumferential weld 1-313 at 52 EFPY.
In the NRCs final SE of BWRVIP-05 for the limiting generic CE -fabricated RPV circumferential weld, the limiting end-of-license neutron fluence was 0.4E19 n/cm2 at 64 EFPY as shown in table 1 of No. RR-A25 and table 2.6-5 of the NRCs final SE for BWRVIP-05. As shown in table 1 of request No. RR-A25, this neutron fluence resulted in the limiting mean ART value of 113.2°F and 128.5°F based on the BWRVIP-05 data and CE BWROG data, respectively.
The NRC staff verified that the limiting mean ART value of 9 ºF for the Fermi 2 limiting circumferential weld 1-313 to be acceptable based on neutron fluence of 5.74E17 n/cm2. In comparison, the NRC staff confirmed that the mean ART for the limiting circumferential weld of 9°F at Fermi 2 is bounded by the limiting mean ART of generic circumferential weld of either 113.2°F or 128.5 °F. Therefore, the staff finds that the conditional failure probability of the Fermi 2 circumferential welds would be lower than the conditional failure probability for the generic circumferential weld for CE-designed RPV in the NRCs final SE for BWRVIP-05.
Based on the assessment above, the NRC staff determined that margin exists in the mean ART value for the Fermi 2 RPV circumferential welds at 52 EFPY as compared to the corresponding limiting mean ART value of the generic CE -fabricated RPV circumferential weld in the NRCs final SE for BWRVIP-05. As such, the NRC staff finds that the licensee has demonstrated that the conditional failure probability of the RPV circumferential welds at Fermi 2 is bounded by the
conditional failure probability results as shown in the NRCs final SE for BWRVIP-05. Therefore, the NRC staff concludes that the subject Fermi 2 circumferential welds satisfy Criterion 1 of the NRCs final SE for BWRVIP-05. The staff further concludes that the proposed alternative satisfies BWRVIP-74-A because the conditional failure probability of the subject circumferential welds is calculated based on the predicted neutron fluence at 52 EFPY which is at the end of the PEO.
Based on the above evaluation, the NRC staff concludes that the Fermi 2 RPV circumferential welds continue to satisfy the limiting conditional failure probability for circumferential welds in appendix E of the NRCs final SE for BWRVIP-5, and guidance of GL 98-05 and BWRVIP A.
Criterion 2 - Operator Training and Established Procedures of Cold Over -Pressure Events
GL 98-05 states that beyond design -basis events occurring during plant shutdown could lead to low temperature over-pressure (LTOP) events that could challenge RPV integrity. The licensee stated that the BWRVIP indicates that LTOP events may come from unmitigated injections from condensate or control rod drive (CRD) systems and a failure to properly realign the reactor water cleanup system following a reactor trip at low temperatures. The licensee further stated that such an event would require several operator errors. Although no LTOP events have occurred at a domestic BWR, the NRC staff identified several events that could be considered precursors to such an event and cited one actual LTOP event that occurred at a foreign BWR.
The licensee explained that Fermi 2 has implemented procedures and t echnical specifications (TSs) which monitor and control reactor pressure, temperature, and water inventory during all aspects of cold shutdown which would minimize the likelihood of an LTOP event from occurring.
Additionally, these procedures are reinforced through operator training.
The licensee further explained that Fermi 2 pressure test procedures have sufficient guidance to prevent a cold, over-pressurization event. The NRC staff noted that licensees are required to perform a pressure test (i.e., a system leakage test) at the end of each refueling outage in accordance with the ASME Code, s ection XI. The licensee stated that the system leakage tests include "pre-job briefing" with all essential personnel which includes conservative decision making, plant safety awareness, lessons learned from similar in-house or industry operating experiences, the importance of open communications, and the process in which the test would be aborted if plant systems responded in an adverse manner. The licensee stated that it monitors vessel temperature and pressure throughout the pressure tests to ensure compliance with the TS pressure-temperature curve.
The licensee stated that to ensure a controlled pressure increase, the rate of pressure increase is administratively limited throughout the pressure test. The licensee further stated that if the pressurization rate exceeds this limit, the procedure dictates that the CRD pumps be turned off which are used for pressurization.
With regard to inadvertent system injection resulting in an LTOP condition, the high-pressure makeup systems (high pressure coolant injection and reactor core isolation cooling systems,
and the normal feedwater supply) at Fermi 2 are all steam driven. The licensee stated that during reactor cold shutdown conditions, no reactor steam is available to operate these systems. As such, the staff determined that because no steam is available when the plant is shutdown, these high NRC -pressure makeup systems will not likely be initiated to cause an overpressure event in the RPV.
The licensee stated that in the case of inadvertent low -pressure system initiation, the Fermi 2 pressure-temperature limit curves for hydrostatic testing permit pressures up to 312 psig (pounds per square inch gauge) at temperatures from 72°F to 102°F. Above 102°F, the permissible pressure increases immediately to near 800 psig and increases rapidly with increasing temperature. The licensee stated that the shutoff head for the core spray and residual heat removal pumps are both below 400 psig. As such, the NRC staff determined that the potential for an over-pressurization event in the RPV which would exceed the pressure-temperature limits is low. The likelihood of an inadvertent actuation of the core spray and residual heat removal systems is low because the pressure head of the pumps is lower than the pressure inside the RPV.
The licensee has implemented procedural control to respond to an unexpected or unexplained rise in reactor water level which could result from a spurious actuation of an injection system.
The actions in this procedure include preventing condensate pump injection, securing emergency core cooling system injection, tripping CRD pumps, terminating other injection sources, and lowering RPV level via the reactor water cleanup system, and the steam line drains.
In addition to procedural controls to limit an LTOP event, the licensee provides training to operators including the following topics: brittle fracture and vessel thermal stress; operational transient procedures, including the operational transient on reactor high level; technical Specifications training, including Section 3.4.10, "RCS Pressure/Temperature (P/T) Limits" and simulator training of plant heatup and cooldown, including performance of surveillance tests which ensure pressure-temperature curve compliance. The licensee reviews industry operating plant experiences to ensure that the Fermi 2 procedures consider the impact of actual events, including potential LTOP events. The licensee adjusts the procedures and associated training to preclude similar situations from occurring at Fermi 2.
The NRC staff finds that the licensee will continue to implement operator training and procedures to limit the frequency of cold overpressure events in accordance with the NRCs final SE for the BWRVIP -05 report, consistent with the staffs previous approval of these methods for the PEO, as documented in section 4.2.5 of Safety Evaluation Report related to the License Renewal of Fermi 2, July 2016 (ML16190A241). Based on the above evaluation, the NRC staff determines that the probability of a cold over -pressure transient is considered to be unlikely, and Criterion 2 is met.
The NRC staff further determined that the licensees procedures, training, pressure-temperature limits in the TS, the ART calculations, and system design are sufficient to provide reasonable
assurance that the overall plant-specific RPV failure probability per reactor operating year (a product of the weld conditional failure probability and the cold overpressure event frequency) is less than the acceptance criterion specified in the NRCs final SE for BWRVIP-05.
4.0 CONCLUSION
The NRC staff finds that the information submitted by the licensee demonstrates that the conditional failure probabilities for the Fermi 2 RPV circumferential shell welds at the end of the PEO satisfies the staffs final SE for BWRVIP-05, and guidance in GL 98-05 and BWRVIP A.
On this basis, the NRC staff concludes that implementation of the BWRVIP-05 methods, in lieu of the specific inspection requirements of the ASME Code, s ection XI, c ategory B-A, Item No. B1.11 for the subject RPV circumferential shell welds, will provide an acceptable level of quality and safety at Fermi 2 for the units 20-year extended license term.
The NRC staff has reviewed the subject request and concludes as set forth above, that the licensee has adequately addressed all the regulatory requirements set forth in 10 CFR 50.55a(z)(1). Therefore, pursuant to 10 CFR 50.55a(z)(1), request N o. RR-A25 is authorized for the term of the Fermi 2 renewed operating license, which ends on March 20, 2045.
All other ASME Code,Section XI, requirements for which relief was not specifically requested and authorized herein by the staff remain applicable, including the third-party review by the Authorized Nuclear lnservice Inspector.
Principal Contributors: E. Palmer NRR J. Tsao, NRR
Date: July 18, 2024
ML24169A409 OFFICE NRR/DORL/LPL3/PM NRR/DORL/LPL3/LA NRR/DNRL/NVIB/BC NRR/DORL/LPL3/BC NAME SArora SRohrer ABuford JWhited DATE 06/05/2024 06/18/2024 02/16/2024 07/18/2024