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NEI 16-03-A, Revision 1, Guidance for Monitoring of Fixed Neutron Absorbers in Spent Fuel Pools
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NEI 16-03-A, Revision 1 Guidance for Monitoring of Fixed Neutron Absorbers in Spent Fuel Pools February 2024

From:

Leslie Fields To:

MONTGOMERY, Bruce Cc:

Gerond George; Matthew Yoder; Reena Boruk; Steven Bloom; Robert Weisman

Subject:

[EXTERNAL] NRC Transmittal of the Final Safety Evaluation for NEI 16-03 Revision 1 Date:

Tuesday, January 30, 2024 4:28:27 PM CAUTION: This email originated from outside of NEI. DO NOT CLICK on any links or attachments unless you trust the sender, know the content is safe, and are expecting this email.

Mr. Bruce Montgomery, Director, Decommissioning and Used Fuel Nuclear Energy Institute 1201 F Street NW Suite 1100 Washington DC, 20004

SUBJECT:

NRC Transmittal of the Final Safety Evaluation for the Nuclear Energy Institute Topical Report, NEI 16-03, Revision 1, Guidance For Monitoring of Fixed Neutron Absorbers in Spent Fuel Pools

Dear Mr. Montgomery,

By letter dated August 19, 2022 (Agencywide Documents Access and Management System (ADAMS) Accession No.ML22231B042), as supplemented by letters dated October 12, 2022 (ADAMS Accession No. ML22298A281), December 15, 2022 (ADAMS Accession Nos. ML22349A656), May 23, 2023 (ADAMS Accession Nos.

ML23143A306), and August 24, 2023 (ADAMS Accession No. ML23236A503). NEI submitted guidance document, NEI 16-03, Revision (Rev.) 1, Guidance for Monitoring of Fixed Neutron Absorbers in Spent Fuel Pools, on behalf of its members for U.S. Nuclear Regulatory Commission (NRC) review and endorsement.

The NEI provided comments on the draft SE via Box.com on December 19, 2023. A copy of the final SE for TR NEI 16-03 Rev. 1 has been placed on BOX.com and access has been granted for review. The final SE will be published in ADAMS within a week under ADAMS Accession No. ML24011A002.

The NRC staff agrees that the purpose of NEIs document is to provide guidance for licensees to develop an acceptable fixed neutron absorber monitoring program in spent fuel pools (SFPs) as a means to demonstrate compliance with applicable regulations as discussed in the SE.The final SE defines the basis of NRCs acceptance of the TR.NRCs acceptance applies only to information provided in the subject TR.In accordance with the guidance provided on the NRC website, NRC requests that NEI publish an accepted version of the TR, within three months of receipt of the date of this email.The accepted version shall incorporate this email and the enclosed SE after the title page.

This email has been placed in ADAMS (Accession No. ML24011A272) and has been declared as an Official Agency Record for public availability.

Please be informed that the accepted versions of this TR must contain historical review

information, including NRC requests for additional information (RAI) questions and the associated responses.The accepted versions shall also include a -A (designating approved) following the TR identification symbol.

As an alternative to including the RAI questions and RAI responses behind the title page, if changes to the TR provided to the NRC staff to support the resolution of RAI responses, and if the NRC staff reviewed and approved those changes as described in the RAI responses, there are two ways that the accepted version can capture the RAIs:

(1.) The RAI questions and responses can be included as an Appendix to the accepted version.

(2.) The RAI questions and responses can be captured in the form of a table (inserted after the final SE) which summarizes the changes as shown in the accepted version of the TR. The table should reference the specific RAI questions and RAI responses which resulted in any changes, as shown in the accepted version of the TR.

If future changes to the NRCs regulatory requirements affect the acceptability of this TR, NEI will be expected to revise the TR appropriately.Licensees referencing this TR would be expected to justify its continued applicability or evaluate their plant using the revised TR.

If you have any questions, please contact the Project Manager for the review,Leslie Fields,at301-415-1186or via electronic mail atleslie.fields@nrc.gov.

Sincerely, Leslie C. Fields US NRC Senior Project Manager 301.415.1186

leslie.fields@nrc.gov

FINAL SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION FOR THE NUCLEAR ENERGY INSTITUTE TOPICAL REPORT NEI 16-03, REVISION 1, GUIDANCE FOR MONITORING OF FIXED NEUTRON ABSORBERS IN SPENT FUEL POOLS PROJECT NO. 689; DOCKET NO. 99902028; EPID L-2022-NTR-0002

Table of Contents

1.0 INTRODUCTION

2.0 REGULATORY EVALUTION........................................................................................

2.1 Applicability of NRC Regulatory Requirements and Guidance.....................................

2.1.1 NRC Regulations.........................................................................................................

2.1.2 General Design Criteria................................................................................................

2.1.3 NRC Guidance Documents..........................................................................................

3.0 TECHNICAL EVALUATION

3.1 Guidance for Developing a Neutron Absorbing Monitoring Program...........................

3.2 Coupon Testing Program.............................................................................................

3.2.1 Overview of NEI 16-03, Revision 1..............................................................................

3.2.2 NRC Staffs Evaluation of the Coupon Testing Program..............................................

3.3 Industrywide Learning Aging Management Program...................................................

3.3.1 Overview of NEI 16-03, Revision 1..............................................................................

3.3.2. NRC Staffs Evaluation of the Industrywide Learning Aging Management Program....

3.4.

In-Situ Measurement Program.....................................................................................

3.4.1. Overview of NEI 16-03, Revision 1..............................................................................

3.4.2. NRC Staffs Evaluation of In-Situ Measurement Program..........................................

3.5.

Evaluating Neutron Absorber Test Results................................................................

3.5.1. Overview of NEI 16-03, Revision 1............................................................................

4.0 CONDITIONS, LIMITATIONS, AND/OR ACTION ITEMS...........................................

5.0 CONCLUSION

S..........................................................................................................

6.0 REFERENCES

1.0 INTRODUCTION

By letter dated August 19, 2022 (Ref. 1), as supplemented by letters (Ref. 4) dated October 12, 2022, December 15, 2022, May 23, 2023, and August 24, 2023, the Nuclear Energy Institute (NEI) submitted proposed methodology document NEI 16-03, Revision (Rev.) 1, Guidance for Monitoring of Fixed Neutron Absorbers in Spent Fuel Pools (Ref. 2), on behalf of its members for U.S. Nuclear Regulatory Commission (NRC) review and endorsement. NEI 16-03, Rev. 1 includes Electric Power Research Institutes (EPRIs) Technical Report 3002018497, Industrywide Learning Aging Management Program (i-LAMP): Global Neutron Absorber Material Monitoring Program for Spent Fuel Pools (Ref. 3) dated August 2022, as an alternative monitoring approach.

The purpose of NEIs document is to provide guidance for licensees to develop an acceptable fixed neutron absorber monitoring program in spent fuel pools (SFPs) as a means to demonstrate compliance with applicable regulations in Section 50.68 of Title 10 of the Code of Federal Regulations (10 CFR), Criticality Accident Requirements, Appendix A to 10 CFR Part 50, General Design Criterion (GDC) 61, Fuel Storage and Handling and Radioactivity Control, and Appendix A to 10 CFR Part 50, GDC 62,Prevention of Criticality in Fuel Storage and Handling, with respect to neutron absorbing materials (NAMs). Although NEI requested the NRC staff to endorse NEI 16-03, Rev. 1, the NRC staff is not proposing to issue a regulatory guide to endorse NEI 16-03. Instead, as stated in this Safety Evaluation (SE), the NRC staff is treating NEI 16-03, Rev. 1, as a topical report, and as described below, the NRC staff has determined that NEI 16-03, Rev. 1 is acceptable, with the limitation described below, for referencing in a licensing action that includes the information described below in Section 4.0 of this SE.

2.0 REGULATORY EVALUTION The effectiveness of the NAM installed in SFP storage racks ensures that the effective neutron multiplication factor (keff) does not exceed the maximum value derived from the criticality analysis of record (AOR) and other licensing basis documents. The AOR is the basis, in part, for demonstrating compliance with plant technical specifications and with applicable NRC regulations. Degradation or deformation of the credited NAM may reduce safety margin and potentially challenge the subcriticality requirement. NAMs utilized in SFP racks exposed to treated water or treated borated water may be susceptible to reduction of neutron absorbing capacity, changes in dimension, and/or loss of material that increases keff. A licensee implements a monitoring program to ensure that degradation of the NAM used in SFPs, which could compromise the ability of the NAM to perform its safety function as assumed in the AOR, will be detected.

2.1 Applicability of NRC Regulatory Requirements and Guidance NRCs regulatory requirements and the corresponding staff review criteria and guidance for NAM monitoring programs are identified in the following subsections.

2.1.1 NRC Regulations The regulations in 10 CFR 50.68(b)(4), Criticality accident requirements, indicates that if the licensee does not credit soluble boron in the SFP criticality AOR, the keff of the SFP storage

racks must not exceed 0.95 at a 95 percent probability, 95 percent confidence level, if flooded with unborated water. If the licensee does take credit for soluble boron, the keff of the SFP storage racks must not exceed 0.95 at a 95 percent probability, 95 percent confidence level, if flooded with borated water; and if flooded with unborated water, the keff must remain below 1.0 at a 95 percent probability, 95 percent confidence level.

2.1.2 General Design Criteria GDC 61, Fuel storage and handling and radioactivity control, states, in part, that The fuel storage and handling, radioactive waste, and other systems which may contain radioactivity shall be designed to assure adequate safety under normal and postulated accident conditions. These systems shall be designed (1) with a capability to permit appropriate periodic inspection and testing of components important to safety[.]

GDC 62, Prevention of Criticality in Fuel Storage and Handling, states that Criticality in the fuel storage and handling system shall be prevented by physical systems or processes, preferably by use of geometrically safe configurations.

2.1.3 NRC Guidance Documents NUREG-0800, Standard Review Plan [(SRP)], Section 9.1.1, Rev. 3, Criticality Safety of Fresh and Spent Fuel Storage and Handling (Ref. 7) provides guidance regarding the acceptance criteria and review procedures to ensure that the proposed changes satisfy the requirements in 10 CFR 50.68.

NUREG-0800, Standard Review Plan, Section 9.1.2, Rev. 4, New and Spent Fuel Storage (Ref. 8) provides guidance regarding the acceptance criteria and review procedures to ensure that the proposed changes satisfy the requirements in 10 CFR 50.68.

NUREG-1801, Generic Aging Lessons Learned (GALL) Report, Rev. 2 (Ref. 9) provides guidance on what constitutes an acceptable monitoring program for NAMs providing criticality control in the SFP.

3.0 TECHNICAL EVALUATION

This technical evaluation section documents the NRC staff's evaluation of the NEI 16-03, Rev. 1 against the relevant criteria identified in Section 2.0 of this SE.

3.1 Guidance for Developing a Neutron Absorbing Monitoring Program NEI 16-03, Rev. 1 provides guidance for developing a NAM monitoring program for NAM in the SFP. The purpose of a NAM monitoring program is to verify that the NAM installed in SFPs continues to provide the criticality control relied upon in the AOR and help to maintain the subcriticality margin in accordance with 10 CFR 50.68 requirements. NEI 16-03, Rev. 1 provides an approach for developing a NAM monitoring program that relies on periodic inspection, testing, monitoring, and analysis of the NAM. To accomplish this purpose, the NEI 16-03, Rev. 1

states that a monitoring program must be capable of identifying unanticipated changes in the absorber material and determining whether anticipated changes can be verified. NEI 16-03, Rev. 1 describes a method that uses coupon testing, in-situ measurement, and/or an i-LAMP as a means to monitor potential changes in characteristics of the NAM.

The NRC staff reviewed NEI 16-03, Rev. 1 to determine whether the approach it describes will result in an acceptable monitoring program, i.e., one that has the ability to ensure that potential degradation of SFP NAM will be detected, monitored, and mitigated. As set forth below, the NRC staff determined that an appropriate combination of the three methods listed above (coupon testing, in-situ measurement, and/or i-LAMP) can comprise an effective NAM monitoring program. During the course of NRC staffs review, several topics were identified that warranted clarification. The NRC staff issued a request for additional information (Ref. 10) and NEI provided clarifying responses and modified NEI 16-03, Rev. 1 as appropriate.

3.2 Coupon Testing Program 3.2.1 Overview of NEI 16-03, Revision 1 NEI 16-03, Rev. 1 describes the use of a coupon testing program as the preferred method for a NAM monitoring program. This method employs small sections (coupons) of the same NAM installed in the SFP, which are attached to a structure (coupon tree) in the SFP. The coupon tree is placed near freshly discharged fuel assemblies in an attempt to accelerate potential degradation mechanisms.

NEI 16-03, Rev. 1 provides the following criteria for an acceptable coupon program:

The number of coupons needs to be adequate to allow for sampling at intervals for the intended life of the absorbers.

The sampling intervals are based on the expected rate of material change.

Performance of coupon testing includes:

Basic testing defined as visual observations, dimensional measurements, and weight analysis, and Full testing defined as density measurements, Boron-10 (10B) areal density (AD) measurements, microscopic analysis, and characterization of changes, in addition to the basic testing parameters.

NEI 16-03, Rev. 1 states that the coupons will be located in the SFP such that their exposure to parameters controlling change mechanisms is conservative or similar to the in-service neutron absorbers. For neutron attenuation testing, NEI 16-03, Rev. 1 provides acceptance criteria for the NAM depending on if there is, or is not, an anticipated loss of 10B AD. The acceptable result for NAMs with expected 10B AD loss is the 10B AD of the test coupon is greater than the 10B AD assumed in the licensees SFP criticality AOR. For NAM without an expected loss of 10B AD, the acceptable result is the 10B AD of the test coupon is equal to the original 10B AD of the coupon (within measurement uncertainty).

In regard to sampling frequency, NEI 16-03, Rev. 1 states that the acceptable initial sampling interval for testing of new material (i.e., with a limited, or no, operating history) is up to 5 years, with subsequent intervals up to 10 years. For those materials that have well-documented

operating experience, they do not have a history of degradation or degradation mechanisms, and information on stability of the material condition is well developed. NEI 16-03, Rev. 1 states that initial and subsequent test intervals up to 10 years are acceptable. NEI 16-03, Rev. 1 states that for materials with known degradation mechanisms, or a history of known degradation (e.g.,

Boraflex, Carborundum, Tetrabor, etc.), the acceptable interval for neutron attenuation testing is at least once every five years. In addition, NEI 16-03, Rev. 1 includes neutron attenuation testing in the full testing approach for any NAMs used, as a component of a satisfactory NAM monitoring program.

3.2.2 NRC Staffs Evaluation of the Coupon Testing Program The NRC staff has evaluated NEI 16-03, Rev. 1 for the basic and full portions of a coupon testing program. The basic portion of the testing includes methods to monitor the physical condition of the NAM so that signs of potential degradation may be observed. The full portion of the testing includes neutron attenuation testing for all NAMs that are credited in the SFP criticality analysis, which will allow the licensee to detect a potential loss in 10B AD. The staff finds the coupon testing program to be acceptable because it includes measurements of 10B AD and of dimensional changes in the material that can impact the ability of the NAM to perform its function as assumed in the licensees SFP criticality AOR.

The NRC staff also determined the acceptance criteria for the coupon testing program provided in NEI 16-03, Rev.1 is acceptable, as follows. The acceptance criteria are adequate to establish that the assumptions regarding the AD of the NAM in the licensees SFP criticality AOR will be maintained, because the acceptance criteria show that the material is either not losing 10B AD (for materials not expected to lose 10B AD), or the 10B AD is still above the 10B AD assumed in the licensees SFP criticality AOR (for NAM anticipated to lose 10B AD). In addition, the NRC staff recognizes that if a coupon being tested approaches the 10B AD value used in the licensees SFP criticality AOR, the licensee would likely need to perform further evaluations and/or take additional corrective actions to conclude that the in-service NAM will not degrade below the 10B AD assumed in the licensees SFP criticality AOR. Provisions for additional corrective actions that may be necessary are discussed in Section 2.4, Evaluating Neutron Absorber Test Results, of NEI 16-03, Rev. 1, and NRC staffs evaluation is discussed in Section 3.5 of this SE.

NEI 16-03, Rev. 1 also states that coupons may be re-inserted into the SFP after non-destructive examination and analysis as long as the coupons are not subjected to heat drying which may cause mechanical damage. The NRC staff understands that the re-installation of coupons may be valuable for licensees that have a limited number of coupons remaining. As stated previously, coupon testing is the preferred method for NAM monitoring and efforts to maintain the coupon inventory are acceptable if the reinserted coupons will continue to yield valid data.

3.3 Industrywide Learning Aging Management Program 3.3.1 Overview of NEI 16-03, Revision 1 The primary difference between NEI 16-03, Rev. 0 and NEI 16-03 Rev. 1 is the addition of i-LAMP as an alternative monitoring option for BORAL plants that do not have surveillance coupons in their SFP. The objective of i-LAMP is to provide access to surrogate or sibling pool data for plants that do not have a coupon monitoring program. The i-LAMP approach is not intended to serve as a replacement for a coupon monitoring program for SFPs with coupons.

The key components of i-Lamp are the SFP coupon database, water chemistry database, analysis of these databases, and analysis of their potential impact on reactivity. The core of i-LAMP is an SFP coupon database. EPRI compiled data from existing coupon test reports and continues to add data as new test results become available.

NEI 16-03, Rev. 1 states that the following data is being collected from plants with BORAL coupon monitoring programs:

Pool name Rack installation year Rack type (egg crate versus flux trap)

Stainless steel encapsulation or not Coupon unique identification (ID) number Coupon analysis year(s), if the same coupon is analyzed multiple times Dimension data (pre-characterization and post-irradiation)

- Height, width, thickness

- Weight

- Areal density values (pre-characterization and post-irradiation)

- Pit and blister data To participate in i-LAMP and leverage surrogate test results for an SFP, a facility that does not have a BORAL coupon monitoring program identifies a sibling plant or plants in the existing database.

The essential parameters needed to identify an appropriate sibling plant are listed below:

Similarity of BORAL characteristics

- Areal density values

- Manufacturing and installation years

- Thickness Similarity of water chemistry data between SFPs

- Boron levels

- Chlorine, Fluorine, Sulfate levels

- Other chemistry parameters NEI 16-03 Rev. 1 calls for licensees to review i-LAMP data at least every 5 years to confirm the continued acceptable performance of sibling pool BORAL.

Acceptance Criteria are described as follows:

The sibling pool BORAL material is represented in the i-LAMP database.

Representation is determined using the parameters described above including material age, areal density, and SFP water chemistry.

Applicable surrogate data has been updated with new operating experience within the last 10 years, unless older data remains bounding for the sibling pool.

Applicable surrogate data does not indicate unanticipated changes are occurring.

Applicable surrogate data confirms that there is no loss of 10B within the measurement uncertainty.

NEI 16-03 Rev. 1 states that based on major research projects conducted by EPRI and data collected from the industry, there are no known degradation mechanisms that have resulted in loss of 10B in BORAL. Because of this, NEI 16-03, Rev. 1 proposes a 2 bin approach which separates plants into those with coupons and those without coupons. NEI 16-03, Rev. 1 proposes that plants without coupons are bounded by the collective database of plants with coupons and therefore do not need to perform a detailed analysis to confirm that they are bounded by a sibling plant or plants. The NRC staffs evaluation of this concept is provided below.

3.3.2. NRC Staffs Evaluation of the Industrywide Learning Aging Management Program The NRC staff has evaluated the proposal in NEI 16-03, Rev. 1, for the implementation of i-LAMP surrogate test data for BORAL plants without a coupon monitoring program. The staff finds that the guidance provides adequate detail with respect to the essential parameters needed to identify a sibling plant. Specifically, the manufacture date, areal density, service life, physical thickness of the BORAL, and its SFP environment including chemistry should be consistent with or bounded by the characteristics of the BORAL and the service environment in a sibling plant in the existing database.

In addition, the staff finds that the acceptance criteria and surveillance intervals described in NEI 16-03 Rev. 1 conform to the NRC guidance in the GALL Report, Rev. 2. The acceptance criteria provide reasonable assurance that the assumptions regarding the AD of the NAM in the licensees SFP criticality AOR will be maintained, because the acceptance criteria show that the material not losing 10B AD and is still above the 10B AD assumed in the licensees SFP criticality AOR.

With respect to the concept of a 2 bin approach, the staff finds that NEI 16-03 Rev. 1 represents an overly simplistic approach. While it may be true that the data collected in i-LAMP to date is representative of all operating SFPs in the United States, the NRC staff is approving use of the i-LAMP approach only for a SFP for which the i-LAMP data bounds the physical characteristics of the BORAL and environmental conditions in the specific SFP. A licensee seeking to reference NEI 16-03, Rev. 1 in an application will need to verify in its application that such is the case. Any licensee that intends to employ i-LAMP as an alternative monitoring strategy should perform a detailed analysis of their SFP and BORAL material considering the parameters described in NEI 16-03 Rev 1. Failure to perform plant-specific analysis to verify that parameters are consistent with a sibling SFP, or bounded by another SFPs BORAL,

constitutes inappropriate application of i-LAMP as an alternative monitoring strategy. This will be addressed in Section 4.0, Limitations and Conditions of this safety evaluation.

Should a new or different degradation mechanism that causes a loss of 10B in BORAL be discovered, NEI 16-03, Rev. 1, calls for that information to be entered into each affected sites corrective action program. This may include development a coupon monitoring program, or use of in-situ monitoring. If the sibling plant data shows a loss of 10B, then the licensee needs to assume that its plant is also losing 10B and develop another means to monitor its NAM.

3.4.

In-Situ Measurement Program 3.4.1. Overview of NEI 16-03, Revision 1 NEI 16-03, Rev. 1 states that in-situ measurement is another method that can be used to confirm 10B AD of NAM. It further states that this method can be used to supplement coupon monitoring to extend the coupon testing interval, permit greater reliance on basic testing, or in lieu of coupon testing for plants that may no longer have coupons in the SFP. It also states that in-situ measurement can be used if surrogate data in i-LAMP may not be bounding of a plants SFP and NAM parameters.

The NEI 16-03, Rev. 1 states that all in-situ measurement campaigns are to be performed at an acceptable interval and on an adequate number of panels. NEI 16-03, Rev. 1 gives two options for determining what constitutes an adequate number of panels. The first option uses the methodology of NUREG-6698, Guide for Validation of Nuclear Criticality Safety Calculational Methodology (Ref. 10), to measure a minimum of 59 panels to provide 95/95 confidence limits.

The second option selects the panels with the greatest exposure (top 5%) to parameters that influence degradation (e.g., neutron fluence, temperature, time). The number of panels selected from those with the greatest exposure for testing will be no less than one percent of the total panels in the SFP, although more panels can be tested from other areas of the SFP to gain a more representative sampling. NEI 16-03, Rev. 1 also states sources of uncertainty in the in-situ measurement will be identified and quantified.

The sampling interval will be based upon the NAM credited in the SFP. New materials with minimal operating experience will have an initial test interval that does not exceed 5 years, with subsequent intervals up to 10 years (with appropriate operating experience). For materials with known histories of degradation and known degradation mechanisms, test intervals do not exceed 5 years. For other materials that do not have known histories of degradation or known degradation mechanisms test intervals will not exceed 10 years. NEI 16-03, Rev. 1 also states that if used in conjunction with a coupon monitoring program, the in-situ sampling interval can be longer.

NEI 16-03, Rev. 1 also provides acceptance criteria for in-situ measurements. It states that for NAMs that do not have potential degradation mechanisms for loss of 10B AD, results of the in-situ measurements are acceptable if the nominal measured 10B AD is greater than or equal to the value assumed in the licensees criticality AOR (within measurement uncertainties). For materials that have potential degradation mechanisms that result in loss of 10B AD, results are

considered acceptable if the nominal measured 10B AD minus measurement uncertainty is greater than the 10B AD used in the licensees criticality AOR.

3.4.2. NRC Staffs Evaluation of In-Situ Measurement Program The NRC staff has reviewed the NEI 16-03, Rev. 1 method for performing in-situ measurement testing and finds it to be acceptable, because it allows for detection of degradation mechanisms, potential loss of neutron absorption capacity (e.g., loss of 10B), and ensures the NAM will continue to provide the criticality control relied upon in the AOR. The NRC staff reviewed the methodology recommended for determining the number of panels that may be selected for in-situ inspection and finds it to be acceptable because it is based in part on guidance provided in NUREG-6698, or on selecting panels that have experienced the greatest exposure to the SFP environment. The NRC staff also finds that depending on the population of NAM panels in the SFP, a licensee may need to measure more than the minimum of 59 panels to produce 95/95 confidence limits. The method used for selecting the panels for in-situ testing will be used to obtain data that is bounding or representative of the entire NAM in the SFP.

In addition, the NRC staff has determined that the proposed testing intervals (intervals not to exceed 10 years for materials with no known history of degradation/degradation mechanisms, and 5 years for materials with a known history of degradation/degradation mechanisms or for new materials (i.e., no operating history)) are acceptable and consistent with NRC guidance in the GALL Report, Rev. 2. Regardless of how the licensee uses the in-situ monitoring program (e.g., in conjunction with coupons, without a coupon program, or other reasons as described in NEI 16-03, Rev. 1), NEI 16-03, Rev. 1 is acceptable only if neutron attenuation is performed on the intervals as described in the in-situ methodology. The statement in NEI 16-03, Rev. 1 that the in-situ sampling interval can be longer if used in conjunction with a coupon program does not obviate the need to perform neutron attenuation testing on intervals not to exceed 5 or 10 years (depending on the NAM used and associated operating experience).

In addition, sources of uncertainty can greatly impact results and confidence in the data collected, especially as it relates to the subcriticality margin. Accordingly, the NRC staff finds the program to be acceptable if it includes provisions to identify and evaluate sources of uncertainty in order to assess the reliability of the instruments and methodology used to the collect the data.

3.5.

Evaluating Neutron Absorber Test Results 3.5.1. Overview of NEI 16-03, Revision 1 NEI 16-03, Rev. 1 states that the test results from neutron absorber monitoring may fall within the following categories:

1) Confirmation that no material changes are occurring,

2) Confirmation that anticipated changes are occurring, and/or

3) Identification that unanticipated changes are occurring.

Furthermore, NEI 16-03, Rev. 1 states that the testing results, and/or surrogate i-LAMP data, will be compared to the AOR input (i.e., 10B AD assumed in criticality AOR). If there are no material changes, or if anticipated changes are occurring, then the proposed program indicates that the licensee can conclude that the material continues to be adequately represented in the AOR.

NEI 16-03, Rev. 1 also describes the additional actions that may be necessary when unanticipated changes in the NAM are identified. It states that there are certain technical evaluations that may be necessary in addition to any required regulatory or licensing processes.

The technical evaluations include one to determine if an unanticipated change in NAM may result in a loss of 10B AD. Any potential impacts of a loss of 10B AD on the SFP criticality AOR will be evaluated and addressed through licensee processes. In addition, the results of monitoring and testing are to be evaluated and trended, regardless of potential impact on the SFP criticality AOR. If an unanticipated change does not appear to result in the loss of 10B AD, the change will still be evaluated for impacts on the SFP criticality AOR. The effects on the SFP criticality AOR due to a potential dimensional change of the NAM, or other material in the SFP, are evaluated and addressed in accordance with licensee processes.

3.5.2. NRC Staffs Evaluation of Neutron Absorber Test Results The NRC staff has reviewed the actions described in NEI 16-03 Rev. 1 for when potential degradation is detected in the neutron absorbing material as potential degradation of the NAM may impact 10B AD assumptions in the SFP criticality AOR. The NRC staff finds the actions described in the NEIs document acceptable because they will be able to identify anticipated, and unanticipated changes to provide information that will allow a licensee to determine whether the neutron absorbing material is performing its safety function as credited in the AOR.

The NRC staff has also determined that it is necessary to evaluate and trend the results of 10B AD measurements from neutron attenuation testing in the NAM as described in NEI 16-03, Rev.1. The NRC staff finds the methods to trend data acceptable because they will provide information regarding the potential degradation mechanism(s) and rate for the NAM in the SFP.

This information will also help the licensee determine whether the 10B AD of the NAM will not decrease below the value assumed in the SFP criticality AOR between the specified test intervals for neutron attenuation testing. In addition, these data can identify previously un-evaluated degradation mechanisms that may have an impact on the SFP criticality AOR.

The actions described above ensure, in part, that the ability of the NAM to provide the criticality control relied upon in the AOR, is maintained.

3.6.

NRC Technical Evaluation Conclusion As summarized below, the NRC staff has determined that the NAM monitoring program described in NEI 16-03, Rev. 1 is acceptable because it includes neutron attenuation testing at acceptable intervals or relies on testing from a surrogate i-LAMP plant that is acceptable if the surrogate plant SFP and NAM conditions and parameters are consistent with or bounding of those of the licensees plant. More specifically, the NRC staff finds the interval for inspection and testing acceptable because the frequency is determined to be based on the neutron absorbing material credited and the operational history of that material. Further, depending on

the material used, the interval for neutron attenuation testing will not exceed 5 years (for materials with a history of known degradation or a known degradation mechanism, and new materials), or 10 years (for other materials that do not have a history of degradation, or a known degradation mechanism). Such testing intervals are adequate to detect degradation of NAM before such degradation has the potential to affect criticality safety. Periodic neutron attenuation testing, and the intervals described in NEI 16-03, Rev.1 are consistent with NRC guidance (i.e.,

the GALL Report, Rev. 2). Licensees will likely need to request site-specific NRC review and approval to extend the interval of any neutron attenuation testing past the approved intervals, as described in NEI 16-03, Rev. 1.

In addition, the NRC staff finds the proposed program acceptable insofar as it calls for the inclusion of the measurement uncertainty in a determination whether the 10B AD value derived from the program is lower than the assumed value in the SFP criticality AOR. If a given test result shows a 10B AD value lower than the value assumed in the SFP criticality AOR, the program provides for the appropriate corrective actions in accordance with licensee programs and processes.

Based on the foregoing, the NRC staff has determined that NEI 16-03, Rev.1 is acceptable for referencing in a licensing action to implement a NAM monitoring program.

4.0 CONDITIONS, LIMITATIONS, AND/OR ACTION ITEMS Limitations and Conditions are additional restrictions imposed by the NRC staff to further define the scope of applicability of NEI 16-03 Rev. 1 and identify any additional actions that will need to be addressed to support NRC staffs review of a request associated with this NEIs document.

4.1.

Limitations and Conditions Based on the staff review of NEI 16-03, Rev. 1, described above, the NRC staff has identified the following limitation on the use of the methodology shown below:

The NRC staff approves the NEI 16-03, Rev. 1, methodology for employing i-LAMP as an alternative monitoring strategy only if the i-LAMP program provides for the licensee to perform a detailed analysis of its SFP and BORAL material considering the parameters described in NEI 16-03 Rev 1. The i-LAMP alternative strategy is unacceptable unless a plant-specific analysis verifies that SFP conditions and BORAL parameters are consistent with those of a sibling SFP or are bounded by those of another SFPs BORAL. This limitation is imposed to address the discussion in NEI 16-03 Rev.1 of a 2-bin system in which plants without coupons are assumed to be bounded by those with coupons.

5.0 CONCLUSION

S The NRC staff has reviewed NEI 16-03, Rev.1 and the proposed methods for developing a NAM monitoring program. For the reasons discussed in this SE, the staff has determined that a NAM monitoring program implementing the NEI 16-03, Rev. 1 program will be able to detect degradation of neutron absorbing material and provides assurance that the ability of the NAM to provide the criticality control relied upon in the AOR is maintained.

The NRC staff finds that the requirements of 10 CFR 50.68(b)(4), GDC 61, and GDC 62, as well as the guidance provided in SRP 9.1.1, SRP 9.1.2, and the GALL, Rev. 2, would be satisfied with respect to NAMs and the NAM monitoring program if referenced in a licensing action to implement the program, and, for an application requesting use of i-LAMP as an alternative, that meets the limitation stated in this SE. Accordingly, the NRC staff has concluded that NEI 16-03, Rev. 1 is acceptable for referencing in an application requesting approval of a NAM monitoring program.

Each licensee adopting NEI 16-03, Rev. 1 will need to implement it in accordance with its plant-specific processes and licensing basis. This will involve review under the plant commitment control process and 10 CFR 50.59. Either of these processes could result in the need for a plant-specific license amendment request. Each licensee will need to make its own evaluation in this regard under its site-specific change control program.

6.0 REFERENCES

1. Letter from R. McCullum (NEI) to J. Donoghue (NRC), Transmittal of Guidance Document NEI 16-03, Revision 1, "Request for Review and Endorsement of NEI 16-03, Guidance for Monitoring of Fixed Neutron Absorbers in Spent Fuel Pools, Revision 1 dated August 2022,"

August 19, 2022 (Agencywide Documents Access and Management System (ADAMS)

Accession No. ML22231B042).

2. Nuclear Energy Institute Guidance Document NEI 16-03, Revision 1, "Request for Review and Endorsement of NEI 16-03, Guidance for Monitoring of Fixed Neutron Absorbers in Spent Fuel Pools," August 2022 (ADAMS Accession No. ML22231B043 (Non-Proprietary).

3. Electric Power Research Institute (EPRI) Technical Report 3002018497, Industrywide Learning Aging Management Program (i-LAMP): Global Neutron Absorber Material Monitoring Program for Spent Fuel Pools, August 2022 (ADAMS Accession No. ML22231B044 (Non-Proprietary).

4. Letters from R. McCullum (NEI) to J. Donoghue (NRC), "Supplement to NEIs Request for Review and Endorsement of NEI 16-03, Guidance for Monitoring of Fixed Neutron Absorbers in Spent Fuel Pools, Revision 1, dated August 19, 2022", October 12, 2023, (ADAMS Accession No. ML22298A281), and Response to NRC Request for Supplemental Information Supporting the Acceptance review of NEI 16-03, Rev. 1, Guidance for Monitoring of Fixed Neutron Absorbers in Spent Fuel Pools, December 15, 2022 (ADAMS Accession Nos. ML22349A656), and Response to NRC Request for Additional Information Supporting the Review of NEI 16-03, Rev. 1, Guidance for Monitoring of Fixed Neutron Absorbers in Spent Fuel Pools, May 23, 2023 (ADAMS Accession Nos. ML23143A306),

and Letter from B. Montgomery (NEI) to NRC, NRC Review of NEI 16-03, Guidance for Monitoring of Fixed Neutron Absorbers in Spent Fuel Pools August 24, 2023 (ADAMS Accession No. ML23236A503).

5. Nuclear Energy Institute 16-03, Guidance for Monitoring of Fixed Neutron Absorbers in Spent Fuel Pools, Revision 0-A, May 2017 (ADAMS Accession Nos. ML17263A133 and ML16354A486 (FSE)).

6. U.S. Nuclear Regulatory Commission, NUREG-0800, "Standard Review Plan for the Review of Safety Analysis Reports for Nuclear Power Plants" (SRP), Section 4.2, "Fuel System Design," Revision 3, March 2007 (ADAMS Accession No. ML070740002).

7. U.S. Nuclear Regulatory Commission, Standard Review Plan, Section 9.1.1, Criticality Safety of Fresh and Spent Fuel Storage and Handling, NUREG-0800, Revision 3, March 2007 (ADAMS Accession No. ML070570006).

8. U.S. Nuclear Regulatory Commission, Standard Review Plan, Section 9.1.2, New and Spent Fuel Storage, NUREG-0800, Revision 4, March 2007 (ADAMS Accession No. ML070550057).

9. U.S. Nuclear Regulatory Commission, Generic Aging Lessons Learned (GALL) Report, NUREG-1801, Revision 2, December 2010 (ADAMS Accession No. ML103490041).

10. U. S. Nuclear Regulatory Commission (NRC) E-mail to NEI Final Request for Additional Information - NEI 16-03, Guidance for Monitoring of Fixed Neutron Absorbers in Spent Fuel Pools, Revision 1 (EPID No. L-2022-NTR-0002) April 24, 2023 (ADAMS Accession No. ML23102A099).

11. U.S. Nuclear Regulatory Commission, Guide for Validation of Nuclear Criticality Safety Calculational Methodology, NUREG/CR-6698, January 2001 (ADAMS Accession No. ML050250061).

Principal Contributor: Matthew Yoder, NRR Date: January 30, 2024 Enclosure NUCLEAR ENERGY INSTITUTE TOPICAL REPORT 16-03, REVISION 1 COMMENT/RESOLUTION TABLE FOR NRCs DRAFT SAFETY EVALUATION (DSE)

Comment Number Text Location in the DSE Comment Type (Clarification, Editorial,

Accuracy, Proprietary)

NEI Suggested Revision NRC Response Page Line No.

No.

1 7

31 Editorial Draft SE text:

The core of i-LAMP is an SFP coupon database.

Suggested edit:

The key components of i-LAMP are the SFP coupon database, water chemistry database, and additional analysis.

Analysis not only includes data analysis for coupons and water chemistry but also impact on reactivity.

The NRC staff finds the comment partially acceptable and revisions have been incorporated.

The NRC staff contends that the coupon database is by far the most important component of i-LAMP. Therefore, the existing language will remain. However, an introductory sentence is added to capture the point that there are other components in the program:

The key components of i-LAMP are the SFP coupon database, water chemistry database, analysis of these databases, and analysis of their potential impact on reactivity.

2 3

13 14 14 20-25 15-16 9-14 17-Editorial/

Clarification Draft SE text:

Section 1.0: the NRC staff has determined that NEI 16-03, Rev. 1 is acceptable, with the limitation described The NRC staff finds the comment partially acceptable and revisions have been incorporated.

NUCLEAR ENERGY INSTITUTE TOPICAL REPORT 16-03, REVISION 1 COMMENT/RESOLUTION TABLE FOR NRCs DRAFT SAFETY EVALUATION (DSE)

Comment Number Text Location in the DSE Comment Type (Clarification, Editorial,

Accuracy, Proprietary)

NEI Suggested Revision NRC Response Page Line No.

No.

21 below, for referencing in a license amendment request (LAR) that includes the information described below in Section 4.0 of this SE.

Suggested edit:

the NRC staff has determined that NEI 16-03, Rev. 1 is acceptable, with the limitation described below, for referencing in a licensees regulatory change control process (e.g., 10 CFR 50.59 review, (LAR), etc.) that includes the information described in Section 4.0 of this SE.

Section 3.6:

Based on the foregoing, the NRC staff has determined that NEI 16-03, Rev.1 is acceptable for referencing in a LAR requesting approval of a NAM monitoring program.

Section 5.0 (paragraph 2): The NRC staff finds that the requirements would be satisfied with respect to NAMs and the NAM monitoring program if referenced in an LAR Although the suggested edits are not accepted verbatim, the language will be changed from license amendment request to licensing action.

As described in Section 5.0 of the safety evaluation, the NRC staff does not intend that application of NEI 16-03 Rev 1 is limited to an LAR or that an LAR is required by all licensees implementing the program.

The final comment is not accepted.

Plant procedures are not regulated by the NRC unless they are included in a license commitment. In which case the other processes listed will cover them.

NUCLEAR ENERGY INSTITUTE TOPICAL REPORT 16-03, REVISION 1 COMMENT/RESOLUTION TABLE FOR NRCs DRAFT SAFETY EVALUATION (DSE)

Comment Number Text Location in the DSE Comment Type (Clarification, Editorial,

Accuracy, Proprietary)

NEI Suggested Revision NRC Response Page Line No.

No.

requesting use of the program Suggested edit:

The NRC staff finds that the requirements would be satisfied with respect to NAMs and the NAM monitoring program if referenced in a licensees regulatory change control process to implement the program Section 5.0 (paragraph 3): Each licensee adopting NEI 16-03, Rev. 1 will need to implement it in accordance with its plant-specific processes and licensing basis. This will involve review under the plant commitment control process and 10 CFR 50.59. Either of these processes could result in the need for a plant-specific LAR. Each licensee will need to make its own evaluation in this regard under its site-specific change control program.

Suggested edit:

Each licensee adopting NEI 16-03, Rev. 1 will need to implement it in accordance with its plant-

NUCLEAR ENERGY INSTITUTE TOPICAL REPORT 16-03, REVISION 1 COMMENT/RESOLUTION TABLE FOR NRCs DRAFT SAFETY EVALUATION (DSE)

Comment Number Text Location in the DSE Comment Type (Clarification, Editorial,

Accuracy, Proprietary)

NEI Suggested Revision NRC Response Page Line No.

No.

specific processes and licensing basis. This will involve review under the plant commitment control process, procedure revision process, and/or 10 CFR 50.59. Either process could result in the need for a plant-specific LAR. Each licensee will need to make its own evaluation in this regard under its site-specific change control program.

Note:

If the suggested edits are untenable, please confirm that the existing SE language does not require licensees to adopt i-LAMP/NEI 16-03 Rev 1 via a LAR, exclusively.

3 9

25-26 Editorial Draft SE text:

With respect to the concept of a 2 bin approach, the NRC staff finds that NEI 16-03 Rev. 1 represents an overly simplistic approach.

Suggested edit:

Suggest deleting the sentence. Licensees will identify sibling(s) for analysis per Limitations and The NRC staff does not find the comment acceptable and the revisions have not been incorporated.

As described in the Limitations and Conditions, the NRC staff does not endorse the 2-bin approach.

Note that the NRC

NUCLEAR ENERGY INSTITUTE TOPICAL REPORT 16-03, REVISION 1 COMMENT/RESOLUTION TABLE FOR NRCs DRAFT SAFETY EVALUATION (DSE)

Comment Number Text Location in the DSE Comment Type (Clarification, Editorial,

Accuracy, Proprietary)

NEI Suggested Revision NRC Response Page Line No.

No.

Conditions in the SE.

Two bin approach is still discussed elsewhere in NEI 16-03 Rev 1 and this sentence appears to be unnecessary to support the overall regulatory determination made in the SE.

staff expects that any relevant data is shared with i-LAMP participants regardless of their identified sibling plant(s). This is intrinsic to the program and independent of the concept of the 2-bin approach.

4 13 29-36 Clarification Draft SE text:

The NRC staff approves the NEI 16-03, Rev. 1, methodology for employing i-LAMP as an alternative monitoring strategy only if the i-LAMP program provides for the licensee to perform a detailed analysis of its SFP and BORAL material considering the parameters described in NEI 16-03 Rev 1. The i-LAMP alternative strategy is unacceptable unless a plant-specific analysis verifies that SFP conditions and BORAL parameters are consistent with those of a sibling SFP or are bounded by those of an older SFPs BORAL. This limitation is imposed to address the discussion in NEI 16-03 Rev.1 of a 2-The NRC staff does not find the comment acceptable and the revisions have not been incorporated.

As described in response to comment #3 the staff does not endorse the 2-bin approach.

Note that the phrase, or bounded by those of an older SFPs Boral is modified consistent with the response to comment #10.

NUCLEAR ENERGY INSTITUTE TOPICAL REPORT 16-03, REVISION 1 COMMENT/RESOLUTION TABLE FOR NRCs DRAFT SAFETY EVALUATION (DSE)

Comment Number Text Location in the DSE Comment Type (Clarification, Editorial,

Accuracy, Proprietary)

NEI Suggested Revision NRC Response Page Line No.

No.

bin system in which plants without coupons are assumed to be bounded by those with coupons.

Suggested edit:

The NRC staff approves the NEI 16-03, Rev. 1, methodology for employing i-LAMP as an alternative monitoring strategy only if the i-LAMP program provides for the licensee to perform a detailed analysis of its SFP and BORAL material considering the parameters described in NEI 16-03 Rev 1. The i-LAMP alternative strategy is unacceptable unless a plant-specific analysis verifies that SFP conditions and BORAL parameters are consistent with those of a sibling SFP.

Note: licensees will identify sibling to perform requisite analysis per the SE, but there is no need to retain language specifically diminishing the 2-bin approach.

Industry understands the 2-bin approach will still effectively be part of the

NUCLEAR ENERGY INSTITUTE TOPICAL REPORT 16-03, REVISION 1 COMMENT/RESOLUTION TABLE FOR NRCs DRAFT SAFETY EVALUATION (DSE)

Comment Number Text Location in the DSE Comment Type (Clarification, Editorial,

Accuracy, Proprietary)

NEI Suggested Revision NRC Response Page Line No.

No.

industrywide and learning aspects of i-LAMP after initial implementation of the program.

5 9

27 Clarification Draft SE text:

While it may be true that the data collected in i-LAMP to date anecdotally bounds all operating SFPs in the United States A large body of data has been collected from coupon measurements, actual panels, and EPRI projects such as the Zion comparative analysis project that have shown no parameters with adverse trends in the performance of BORAL.

Suggested edit:

Replace anecdotally bounds with is representative of The NRC staff finds the comment acceptable and the revisions have been incorporated.

6 8

21 Editorial Draft SE text:

The essential parameters needed to identify an appropriate sibling plant is listed below:

Suggested edit:

Replace the word is with the word are in this line.

The NRC staff finds the comment acceptable and the revisions have been incorporated.

7 13 3

Editorial Draft SE text:

described in The NRC staff finds the comment

NUCLEAR ENERGY INSTITUTE TOPICAL REPORT 16-03, REVISION 1 COMMENT/RESOLUTION TABLE FOR NRCs DRAFT SAFETY EVALUATION (DSE)

Comment Number Text Location in the DSE Comment Type (Clarification, Editorial,

Accuracy, Proprietary)

NEI Suggested Revision NRC Response Page Line No.

No.

NEI 16-03 are consistent Suggested edit:

Add Rev. 1 after NEI 16-03 acceptable and the revisions have been incorporated.

8 9

12 14-15 39 Editorial/

Clarification Draft SE text:

Section 3.3.2: and its SFP environment including chemistry should be consistent with or bounded by the characteristics of the BORAL Suggested edit:

Remove or bounded by in this sentence.

Section 3.6: SFP and NAM conditions and parameters bound those of the licensees plant.

Suggested edit:

Replace bound with are consistent with The NRC staff does not find the comment acceptable and the revisions have not been incorporated.

Removing the concept of bounding would create a more restrictive situation for licensees. They would be forced to show consistence with another plant.

This leaves the question of whether a parameter is perfectly matched.

That is not the NRC staffs intent. By allowing licensees to be consistent with or bounded by other plants, licensees have more freedom when identifying sibling plants.

Note that are consistent with was added to Section 3.6, but the

NUCLEAR ENERGY INSTITUTE TOPICAL REPORT 16-03, REVISION 1 COMMENT/RESOLUTION TABLE FOR NRCs DRAFT SAFETY EVALUATION (DSE)

Comment Number Text Location in the DSE Comment Type (Clarification, Editorial,

Accuracy, Proprietary)

NEI Suggested Revision NRC Response Page Line No.

No.

concept of bounding remains.

9 3

7 7

7 12 13 13 38 3

5 10 17 10 11 Editorial Suggested edit:

Draft SE uses presume/presumption and assume/assumption seemingly interchangeably.

Revise document to be consistent, using assume/assumption throughout, as analyses use assumptions rather than presumptions The NRC staff finds the comment acceptable and the revisions have been incorporated.

10 10 33-36 Clarification Draft SE text:

Failure to perform plant-specific analysis to verify that parameters are consistent with a sibling SFP, or bounded by an older SFPs BORAL, constitutes inappropriate application of i-LAMP as an alternative monitoring strategy. This will be addressed in Section 4.0, Limitations and Conditions of this safety evaluation.

Suggested edit:

Failure to perform plant-specific analysis to verify that parameters are consistent with a sibling SFP, or bounded by an older SFPs BORAL, constitutes inappropriate application of i-LAMP as The NRC staff finds the comment partially acceptable and revisions have been incorporated.

The term bounded by remains but the term older was changed to another.

NUCLEAR ENERGY INSTITUTE TOPICAL REPORT 16-03, REVISION 1 COMMENT/RESOLUTION TABLE FOR NRCs DRAFT SAFETY EVALUATION (DSE)

Comment Number Text Location in the DSE Comment Type (Clarification, Editorial,

Accuracy, Proprietary)

NEI Suggested Revision NRC Response Page Line No.

No.

an alternative monitoring strategy. This will be addressed in Section 4.0, Limitations and Conditions of this safety evaluation.

Note: Age is one of the applicable parameters of interest from NEI 16-03 Rev 1 to be considered in determining a sibling SFP.

NEI 16-03-A, Revision 1 Nuclear Energy Institute Guidance for Monitoring of Fixed Neutron Absorbers in Spent Fuel Pools August 2023

ACKNOWLEDGEMENTS This guidance was developed by EPRIs Neutron Absorber User Group (NAUG). The dedicated and timely effort of the many participants, including management support of the effort, is greatly appreciated. Finally, we would like to thank the U.S. Nuclear Regulatory Commission for providing feedback during a pre-application meeting (ML21187A057).

NOTICE Neither NEI, nor any of its employees, members, supporting organizations, contractors, or consultants make any warranty, expressed or implied, or assume any legal responsibility for the accuracy or completeness of, or assume any liability for damages resulting from any use of, any information apparatus, methods, or process disclosed in this report or that such may not infringe privately owned rights.

NEI 16-03-A, Revision 1 August 2023

i FOREWORD This guidance describes acceptable methods that may be used by industry to monitor fixed neutron absorbers in PWR and BWR spent fuel pools to ensure that aging effects and corrosion and/or other degradation mechanisms are identified and evaluated prior to loss of the intended safety function.

NEI 16-03-A, Revision 1 August 2023

ii TABLE OF CONTENTS 1

INTRODUCTION.......................................................................................................... 1 1.1 PURPOSE.........................................................................................................................1

1.2 BACKGROUND

.................................................................................................................1 1.3 APPLICABLE REGULATIONS...........................................................................................2 2

NEUTRON ABSORBER MONITORING PROGRAMS................................................... 2 2.1 COUPON TESTING PROGRAM.........................................................................................3

2.2 I-LAMP

INDUSTRYWIDE LEARNING AGING MANAGEMENT PROGRAM.....................5 2.2.1 i-LAMP Components and Development.......................................................5 2.2.2 Sibling Pool Criteria.......................................................................................8 2.2.3 i-LAMP Implementation................................................................................8 2.2.4 i-LAMP Acceptance Criteria.........................................................................9 2.3 IN-SITU MEASUREMENT PROGRAM.............................................................................10 2.4 EVALUATING NEUTRON ABSORBER TEST RESULTS...................................................11 3

REFERENCES........................................................................................................... 12 3.1 REGULATIONS...............................................................................................................12 3.2 NUREGS.......................................................................................................................12 3.3 OTHER 12 APPENDIX A: INDUSTRYWIDE LEARNING AGING MANAGEMENT PROGRAM (I-LAMP):

GLOBAL NEUTRON ABSORBER MATERIAL MONITORING PROGRAM FOR SPENT FUEL POOLS............................................................................................................ 14 A.1 I-LAMP DEVELOPMENT................................................................................................14 A.1.1 Overview of Neutron Absorber Materials and Monitoring Status in i-LAMP.............................................................................................................14 A.1.2 SFP Water Chemistry.......................................................................................16 A.1.3 SFP Coupon Database......................................................................................17 A.1.4 SFPs with No Coupons......................................................................................18 A.1.5 Synergy Effects..................................................................................................18 A.1.6 Sibling Pool Criteria.........................................................................................19 A.2 AUGMENTATION AND BOUNDING OF I-LAMP VIA EVALUATION OF PANELS FROM AN OPERATING SPENT FUEL POOL...................................................................................20 A.2.1 History of the Panels.........................................................................................20 A.2.2 Removal of the Panels.......................................................................................21 A.2.3 Water Chemistry History.................................................................................22 A.2.4 Areal Density Values.........................................................................................26 A.2.5 Comparison of Panels from Zion SFP and SFP-2..........................................33 A.3 DEMONSTRATION OF I-LAMP VIA CASE STUDIES........................................................35 A.3.1 Pilot-1 as Case Study.........................................................................................35 A.3.2 Pilot-2 as Case Study.........................................................................................44

NEI 16-03-A, Revision 1 August 2023

iii A.4 PROPOSED IMPLEMENTATION.......................................................................................47 A.5 EXAMPLE SURROGATE APPROACHES AS PART OF MONITORING AND AGING MANAGEMENT PROGRAMS..........................................................................................48 A.5.1 High Burnup (HBU) Demonstration Project..................................................48 A.5.2 Dry Cask Storage Aging Management............................................................50 A.5.3 Aging Management Programs for Reactor Pressure Vessel.........................51 A.6 APPENDIX A REFERENCES.............................................................................................51

NEI 16-03-A, Revision 1 August 2023

iv TABLE OF FIGURES Figure A. 1: Distribution of NAMs as a function of areal density............................................... 15 Figure A. 2: Distribution of NAMs as a function of installation year.......................................... 16 Figure A. 3: Blister height as a function of measurement year.................................................... 19 Figure A. 4: Summary of the history of the panels....................................................................... 21 Figure A. 5: Sample 12 from Panel-1 (left) and Sample 20 from Panel-2 (right)........................ 22 Figure A. 6: Boron concentration over time for SFP-2................................................................ 23 Figure A. 7: Distribution of B levels across the industry for PWR pools.................................... 23 Figure A. 8: Cl levels over time.................................................................................................... 24 Figure A. 9: Sulfate levels over time............................................................................................ 24 Figure A. 10: F levels over time................................................................................................... 25 Figure A. 11: Silica levels over time............................................................................................ 26 Figure A. 12: Areal density measurement locations for neutron absorber panel samples............ 27 Figure A. 13: Distribution of areal density values for samples from Panel-1.............................. 28 Figure A. 14: Areal density values for samples from Panel-1...................................................... 29 Figure A. 15: Average areal density values for samples from Panel-1 as a function of sample number.......................................................................................................................................... 30 Figure A. 16: Distribution of areal density values for samples from Panel-2.............................. 31 Figure A. 17: Areal density values for samples from Panel-2...................................................... 32 Figure A. 18: Average areal density values for samples from Panel-2 as a function of sample number.......................................................................................................................................... 33 Figure A. 19: Panel history for panels residing in Sibling Pool (top) and Pilot-1 (bottom)......... 36 Figure A. 20: B levels for SFP-2 (top) and Pilot Plant 1, SFP-B (bottom).................................. 38 Figure A. 21: Cl levels for SFP-2 (top) and Pilot Plant 1, SFP-B (bottom)................................. 39 Figure A. 22: Sulfate levels for SFP-2 (top) and Pilot Plant 1, SFP-B (bottom).......................... 40 Figure A. 23: F levels for SFP-2 (top) and Pilot Plant 1, SFP-B (bottom)................................... 41 Figure A. 24: Silica levels for SFP-2 (top) and Pilot Plant 1, SFP-B (bottom)............................ 42 Figure A. 25: Benefits of the proposed approach for Pilot-1, Sibling-1, and i-LAMP................ 44 Figure A. 26: Boron levels for Pilot-2 (left), Sibling-1 (center), and Sibling-2 (right) over time 46 Figure A. 27: Cl levels for Pilot-2 (left), Sibling-1 (center), and Sibling-2 (right) over time...... 46 Figure A. 28: Silica levels for Pilot-2 (left), Sibling-1 (center), and Sibling-2 (right) over time. 46 Figure A. 29: Updated NAM status as a function of areal density............................................... 48 TABLE OF TABLES Table A. 1: Comparison of panels removed from Zion and SFP-2.............................................. 34 Table A. 2: Summary of the specifications for sibling pool and pilot pool.................................. 37 Table A. 3: Summary of water chemistry levels for Sibling-1 and Pilot-1.................................. 43 Table A. 4: Summary of the NAM specifications for Pilot-2 and identified siblings.................. 45

NEI 16-03-A, Revision 1 August 2023

v ABBREVIATIONS AND ACRONYMS AD Areal Density BWR Boiling Water Reactor CAP Corrective Action Program CFR Code of Federal Regulations EPRI Electric Power Research Institute i-LAMP Industrywide Learning Aging Management Program ISG Interim Staff Guidance LAR License Amendment Request LWR Light Water Reactor NAM Neutron Absorber Material NAUG Neutron Absorber User Group NEI Nuclear Energy Institute NRC Nuclear Regulatory Commission PWR Pressurized Water Reactor QA Quality Assurance SFP Spent Fuel Pool

NEI 16-03-A, Revision 1 August 2023

1 1 INTRODUCTION 1.1 PURPOSE This document provides acceptable methods for monitoring of neutron absorber materials (NAMs) in spent fuel storage racks at nuclear power plants. This guidance is applicable to both Boiling Water Reactor (BWR) and Pressurized Water Reactor (PWR) spent fuel pools.

This document is developed to provide comprehensive and durable guidance to improve consistency and clarity for implementing neutron absorber monitoring programs. It is envisioned that this guidance will be reviewed and approved as a Topical Report by the NRC in accordance with NRR Office Instruction LIC-500 [11].

1.2 BACKGROUND

Spent fuel storage racks were originally designed to preclude a criticality event through geometric separation and neutronic decoupling of the spent fuel assemblies by a large distance, with no neutron absorbers. However, when reprocessing ceased to be a viable option and the federal repository progress was delayed, nuclear plants were faced with storing a greater number of discharged spent fuel assemblies in the spent fuel pool. Since the original racks utilized geometric spacing as the primary method of criticality control, a large part of the spent fuel pool was not efficiently utilized for storage.

Beginning in the late 1970s, industry proposed installing high-density storage racks in the spent fuel pool to accommodate the discharged fuel. Since the fuel assemblies were now placed closer together, other means needed to be employed to preclude a criticality event, namely fixed neutron absorbers installed between each storage cell. Many types of neutron absorbers have been used over the past four decades, but in all cases, the primary neutron absorbing isotope is 10B, which has a large thermal neutron absorption cross-section, and therefore is ideal for absorbing neutrons in the spent fuel pool (i.e., in a system with a strong moderator such as water)

[10].

With nuclear power reactors and their associated spent fuel pools undergoing license renewal for an additional 20 years of operation, the NRC developed aging management guidance for fixed neutron absorbers in spent fuel pools in NUREG-1801, Revision 2 [8].

In conjunction with the use of fixed neutron absorbers, the NRC required periodic demonstration of the efficacy of the installed neutron absorber, through monitoring of the behavior of the neutron absorber via coupons or in-situ measurements [7]. The frequency of inspections and criteria for inspection was determined on a case-by-case basis, depending upon the type of material, historical operating experience for the specific material to be used, and other factors during the license amendment request process.

Licensee commitment(s) to one or more NAM monitoring programs may be made through various processes and at different levels of formality. Changing commitments may involve a range of options from the use of 10 CFR 50.59 [5] to a license amendment request depending on how and where the commitment is described.

NEI 16-03-A, Revision 1 August 2023

2 1.3 APPLICABLE REGULATIONS The following regulations are applicable to neutron absorber materials for nuclear fuel storage at LWR facilities:

Title 10 of the Code of Federal Regulations (10 CFR) 50 Appendix A, General Design Criteria for Nuclear Power Plants Criterion 61, Fuel Storage and Handling and Radioactivity Control. [1]

10 CFR 50 Appendix A, General Design Criteria for Nuclear Power Plants Criterion 62, Prevention of Criticality in Fuel Storage and Handling. [2]

10 CFR 50 Appendix B, Quality Assurance Criteria for Nuclear Power Plants and Fuel Reprocessing Plants. [3]

10 CFR 50.36, Technical Specifications. [4]

It is noted that in addition to the applicable regulations, the NRC has developed associated staff review guidance associated with neutron absorbers for nuclear fuel storage at LWR facilities.

NUREG-0800, Standard Review Plan, Section 9.1.1, Criticality Safety of Fresh and Spent Fuel Storage and Handling, Revision 3. [6]

NUREG-0800, Standard Review Plan, Section 9.1.2, New and Spent Fuel Storage, Revision 4. [7]

NUREG-1801, Revision 2, Generic Aging Lesson Learned (GALL) Report, Revision 2, December 2010. [8]

2 NEUTRON ABSORBER MONITORING PROGRAMS1 Neutron absorbers serve as an important material to control reactivity in most spent fuel pool storage racks. Neutron absorber monitoring programs are developed with the purpose of verifying that the neutron absorbers continue to provide the criticality control relied upon in the criticality analyses. To accomplish this, the monitoring program must be capable of identifying whether changes to the material are occurring; and if those changes are occurring, that the anticipated characteristics of change can be verified.

A neutron absorber monitoring program may rely on one of the following approaches:

1) Installation of a neutron absorber coupon tree with periodic removal and testing of neutron absorber coupons.

2) EPRIs industrywide learning aging management program (i-LAMP).

1 While these guidelines for neutron absorber monitoring programs are intended for initial license applications and license amendment requests that install new neutron absorber materials, they may be useful for licensees consideration in license renewal applications under 10 CFR Part 54.

NEI 16-03-A, Revision 1 August 2023

3

3) In-situ measurements of the neutron absorbing capability of the installed neutron absorber panels.

Alternative approaches are also acceptable if adequately justified.

A monitoring program consists of identifying original material characteristics, material testing, awareness of ongoing research and development, participation in industry groups that share operating experience amongst plants, and evaluation of the relevance of outside data on the in-service material. Acceptance criteria provide the basis for the comparison of results in order to determine whether material performance is acceptable, or actions are necessary to address performance issues.

2.1 COUPON TESTING PROGRAM Use of coupons is the preferred testing method for a neutron absorber monitoring program. The coupon testing program consists of a population of small sections of the same neutron absorber installed in the storage racks. These coupons can either be encased in the same material as the storage rack structure, to simulate the geometry of the storage rack, or they may remain fully exposed to the spent fuel pool environment. The coupons are generally attached to a structure that can be placed in a spent fuel rack storage cell, referred to as a coupon tree. The coupon tree is placed in a location in the spent fuel pool, near freshly discharged fuel assemblies, to generate an accelerated rate of accumulated exposure to those parameters that may impact aging/degradation mechanisms.

A coupon testing program consists of the following elements:

The number of coupons needs to be sufficient to provide sampling at an appropriate interval for the intended life of the neutron absorber. Coupons may be re-inserted into the SFP after non-destructive analysis, provided they are not heat dried. The intended life of the neutron absorber is based upon the amount of time the neutron absorber will be relied upon to provide criticality control. This is typically the life of the plant (including license renewal) plus some additional time to permit off-loading the spent fuel pool during decommissioning.

Sampling intervals are based upon the expected rate of material changes, which may be influenced by the qualification testing of the material. For new materials that do not have applicable operating experience in conditions similar to the pool environment (i.e., their ability to perform over time is not well known), the initial interval of 5 years, with subsequent intervals up to 10 years is acceptable. For materials that have been used for several years in conditions similar to the pool environment (i.e., their ability to perform is well known), and for which stability of the material condition has been documented, initial and subsequent intervals up to 10 years is acceptable.

Coupon testing is categorized as a combination of basic and full testing. The coupon testing is used to identify whether unanticipated changes are occurring. If they are, the condition of the neutron absorber material is determined to evaluate further actions. The extent to which each of these is utilized is determined based upon the operating history of the material, as follows:

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4 a) Basic testing consists of visual observations, dimensional measurements, and weight that may be performed at the spent fuel pool. These parameters focus on identification of whether changes are occurring in the materials. Basic testing is appropriate when previous testing and operating experience of the material indicates that there are no degradation mechanisms that would result in loss of 10B areal density that would affect reactivity. Basic testing will occur at least every 10 years.

b) Full testing may consist of a combination of mass-density measurements, 10B areal density measurements, microscopic analysis, and characterization of changes, in addition to the basic testing parameters. These parameters focus on quantifying changes if they are occurring in the materials. Basic testing may be used in combination with full testing for materials that have degradation resulting in loss of 10B areal density to extend the interval of full testing, if appropriately justified. The 10B areal density measurement will occur at least every ten years*.

For materials with known degradation or degradation mechanisms that impact the efficacy of the neutron absorber (e.g., Boraflex, Carborundum, Tetrabor or other phenolic resin-based materials), the measurement of the areal density at least once every 5 years is acceptable.

Note: Licensees that are nearing exhaustion of the originally installed coupons in the spent fuel pool and have a compelling need to extend the life of the neutron absorber coupon monitoring program, should consider re-insertion of coupons after testing. If re-insertion is not possible or practical, and if the remaining coupon population is low, licensees may seek NRC review and approval of an exception to the prescribed periodic areal density measurements. This exception would be explored on a site-specific basis, subject to NRC review and approval, supported by the data from the previous neutron absorber coupon measurements that the neutron absorber will continue to serve its intended safety function and that any precursors to degradation will be captured by basic testing. Additionally, this exception may warrant more frequent basic testing, depending upon the experience obtained from previous coupon measurements.

The location of the coupons is such that their exposure to parameters controlling change mechanisms (e.g., gamma fluence, temperature) is conservative or similar to the in-service neutron absorbers.

Results are acceptable to confirm the continued performance of neutron absorber materials if either:

a) For materials that are not anticipated to have a loss of 10B areal density; the 10B areal density of the test coupon is the same as its original 10B areal density (within the uncertainty of the measurement2).

2 In the NRC Safety Evaluation Report for NEI 16-03 Revision 0 [9], a condition was added to this criterion such that if the measured 10B areal density minus measurement uncertainty falls below the areal density used in the criticality analysis, the result is not acceptable.

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5 b) For materials that are anticipated to have a loss of 10B areal density; the 10B areal density of the test coupon is greater than the 10B areal density used in the criticality analysis.

2.2 I-LAMP

INDUSTRYWIDE LEARNING AGING MANAGEMENT PROGRAM In 2018, EPRI published the Roadmap for the Industrywide Learning Aging Management Program (i-LAMP) for Neutron Absorber Materials in Spent Fuel Pools, which demonstrates the viability of an industrywide neutron absorber monitoring program [12]. The objective of the i-LAMP program is to provide access to surrogate or sibling pool NAM performance data to SFPs without a coupon monitoring program and to identify aging trends earlier to improve control and mitigation of degradation effects. The i-LAMP proposal was cited in the closure of GL 2016-01 in 2018 [13] along with the EPRI study on the impact of blisters and pits [14] on SFP criticality.

To demonstrate the viability of an industrywide monitoring program, data for the key components of i-LAMP (SFP water chemistry and neutron absorber material specifications and results to date for SFPs, with initial focus on BORAL) are being collected across the global industry and analyzed. EPRIs i-LAMP program is described in detail in a recently published EPRI report [15].

i-LAMP is intended to allow the use of surrogate coupon measurement data for SFPs without coupons, specifically for BORAL. It is not intended to serve as a replacement for a coupon monitoring program for SFPs with coupons. In response to an NRC letter [16], with EPRIs permission, portions of the EPRI i-LAMP report [15] are reproduced in this section and in Appendix A.

For newer materials (for example, Metamic and Boralcan), there is currently no surrogate coupon monitoring option. Participation in the i-LAMP program by SFPs with coupon testing of these materials enables proactive industrywide data collection (coupon results and SFP water chemistry), analysis, and trending of material performance. If any issues are identified, the i-LAMP program can assist with early detection of trends and timely dissemination of this information for appropriate follow-on actions for the benefit of i-LAMP participants and the industry via regular EPRI Neutron Absorber User Group (NAUG) meetings.

2.2.1 i-LAMP Components and Development For a given neutron absorber material, aging effects in SFPs may be a function of:

1. Type and vintage of the material

2. Time in the SFP

3. SFP water chemistry

4. Temperature

5. Cumulative neutron dose

6. Cumulative gamma dose

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6 It should be noted that for different materials, the significance of the listed factors can vary. For example, for materials like Boraflex, cumulative gamma dose was the primary factor for degradation.

In the following sections, i-LAMP components and subsequently, development of sibling pool criteria based on these components, will be presented.

2.2.1.1 SFP Water Chemistry SFP water chemistry is monitored at regular intervals at all the SFPs in the U.S. and in many of the countries around the world. SFP water chemistry measurements serve two purposes:

Ensuring compliance with water chemistry guidelines for corrosion. The EPRI PWR and BWR water chemistry guidelines [18, 19] recommend Chloride (Cl), Fluoride (F), and Sulfate (SO4) levels below 150 ppb to reduce the corrosion potential. The guidelines were developed primarily to reduce corrosion of the fuel.

As a monitoring tool, when there are anomalies, the chemistry levels can be an early indicator. For example, Boraflex degradation was first identified when SFP silica levels were elevated.

In other programs (for example, vessel integrity, steam generator integrity), water chemistry is used as a part an of industrywide monitoring program for the same purpose.

The collected water chemistry data typically includes the following measured parameters for pools:

pH

Conductivity

Chloride (Cl) concentration

Fluoride (F) concentration

Sulfate (SO4) concentration Additionally, for PWRs

Boron (B) concentration

Sodium (Na) concentration Historic SFP water chemistry data from all U.S. utilities and other participating countries (for example, Mexico, Taiwan, S. Korea, U.K.) has been collected. The water chemistry database is being updated with new data approximately every six months.

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7 2.2.1.2 SFP Coupon Database The SFP coupon database is developed to collect the data, analyze the data to determine bounding conditions (changes in areal density, maximum observed blisters/pit sizes to date),

trends, and any potential relationship between observed degradation and SFP water chemistry and other parameters.

The data that are being extracted from coupon reports currently include:

Pool name

Rack installation year

Rack type (egg crate versus flux trap)

Stainless steel encapsulation or not

Coupon unique ID number

Coupon analysis year(s), if the same coupon is analyzed multiple times

Dimension data (pre-characterization and post-irradiation) o Height, width, thickness o Weight o Areal density values (pre-characterization and post-irradiation) o Pit and blister data 2.2.1.3 SFPs with No Coupons To develop an industrywide monitoring program and develop sibling pool criteria for the entire fleet of SFPs, basic information on neutron absorber materials from all the participating SFPs was gathered. This data collection and analysis allowed the development of sibling pool criteria.

For SFPs without a coupon program, some of the basic information related to neutron absorber materials was collected and analyzed. The basic information needed for SFPs without coupons includes:

Neutron absorber material areal density values

Neutron absorber material thickness

Manufacturing and installation year If a particular characteristic is unbounded, i-LAMP data may still be applicable for surrogate coupon monitoring provided analysis shows that there is no degradation trend related to that

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8 characteristic. An example for this case is illustrated in Appendix A for implementation of i-LAMP via case studies.

2.2.2 Sibling Pool Criteria Sibling pool relationship is assessed by comparison of material and water chemistry characteristics:

1) Similarity of NAM characteristics

Areal density values

NAM manufacturing and installation years

NAM thickness

2) Similarity of water chemistry data between SFPs

Boron levels

Cl, F, Sulfate levels

Other chemistry parameters (for example silica levels)

Practical examples of similarity assessment are provided in Appendix A as case studies.

However, to date no degradation trend leading to loss of 10B has been observed for BORAL.

With no identified trends, applicability of i-LAMP to a particular SFP can be determined by assessing whether the sibling pool characteristics are bounded by the total coupon experience database (the two-bin approach discussed in Section 2.2.3).

Sibling pool criteria are also useful in the event a pool that no longer needs coupons (such as decommissioning) chooses to provide coupons to a sibling pool that has no coupons for installation in the sibling pool.

2.2.3 i-LAMP Implementation Based on the key findings from major research projects conducted by EPRI and data collected from the industry across the globe, there are no known degradation mechanisms that have resulted in loss of 10B in BORAL. Because of this, a very simple industry-wide binning approach can be used at this time instead of sibling identification. If in the future further binning or use of surrogate/sibling relationships is required, this will be done consistent with the acceptance criteria described in Section 2.2.4.

Bin 1 - SFPs with coupons

Bin 2 - SFPs without coupons The proposed approach considers significant operating experience and analysis to date:

1. Coupon results from many SFPs over decades.

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9

2. Actual panel removal from a decommissioned site (Zion) and comparison to coupon results to evaluate if coupons indeed represent the panel conditions.

3. Removal and evaluation of panels with unique history from an operating SFP.

The two-bin approach will simplify implementation because it would not require identification of siblings for every licensee without coupons unless future NAM monitoring data indicate there is a need for identification of specific siblings or further binning refinement.

Since i-LAMP is a learning aging management program, the number of bins will be refined if/when trends resulting in loss of 10B are identified. If any issues are identified, the i-LAMP program can assist with early detection of trends and timely dissemination of this information for appropriate follow-on actions for the benefit of i-LAMP participants and the industry via regular EPRI Neutron Absorber User Group (NAUG) meetings.

Should a new or different degradation mechanism that causes a loss of 10B in the NAM be discovered, that information would be entered into that sites corrective action program and shared with the industry via the NAUG. Each plant receiving this information would evaluate it within its operating experience program and/or corrective action program as circumstances dictate.

2.2.4 i-LAMP Acceptance Criteria Use of i-LAMP surrogate data to confirm the continued acceptable performance of sibling pool BORAL is analogous to use of coupon testing results described in Section 2.1. Periodic review of i-LAMP data performed at 5-year intervals maintains this consistency with the coupon testing program interval (performed at 5-year or 10 -year intervals, as discussed in Section 2.1). Results are acceptable if:

The sibling pool BORAL material is represented in the i-LAMP database.

Representation is determined using the characteristics described in Section 2.2.2 and Appendix A, including material age, areal density, and SFP water chemistry.

Applicable surrogate data has been updated with new operating experience within the last 10 years, unless older data remains bounding for the sibling pool.

Applicable surrogate data does not indicate unanticipated changes are occurring.

Applicable surrogate data confirms that there is no loss of 10B within the measurement uncertainty.

Anticipated BORAL coupon changes including blistering and pitting are well-known and have been previously documented and evaluated. To date (40+ years of operating experience),

BORAL has not been found to undergo aging degradation that results in a loss of 10B. However, if applicable surrogate data (two-bin or sibling approach, depending on the implementation status) does indicate loss of 10B, the sibling pool BORAL would be treated as a material that is known to lose 10B (acceptance criterion (b) in Section 2.1), including trending of 10B loss over time and other appropriate corrective actions.

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10 2.3 IN-SITU MEASUREMENT PROGRAM In-situ measurement is another acceptable method for confirming 10B areal density of neutron absorber material. In-situ measurement is used to confirm the presence of NAM in the SFP racks and identify whether 10B areal density loss is occurring. Some industry experience indicates that the current tool can exhibit significant uncertainty and bias, which subsequently may be interpreted as loss of 10B when in fact, no loss of 10B occurred (i.e., false degradation indication)

[17]. In situ measurements can be used in lieu of coupon testing if coupons do not exist and surrogate data in i-LAMP (for BORAL) may not be bounding.

The in-situ measurement program consists of the following elements:

In-situ measurement campaigns include an adequate number of panels and at an acceptable interval. Two options are available for determining an adequate number of panels:

o Option 1: Take a measurement of a minimum of 59 panels, based on the methodology of NUREG-6698 to provide a 95% degree of confidence that 95%

of the population is above the smallest observed value.

o Option 2: Selectively choose panels to be tested that have experienced the greatest exposure (within the top 5%) to those parameters that influence degradation (i.e.,

radiation fluence, temperature, time). The number of panels selected consists of no less than 1% of the total number of panels in the spent fuel pool. Additional panels can be selected from other areas of the spent fuel pool to gain a more representative sampling of the spent fuel pool.

It is recommended that in-situ measurement campaigns consider the availability of equipment to reach storage locations, minimization of spent fuel transfers and separation of the measured storage cells from other spent fuel to minimize signal noise and eliminate corruption of the results by background radiation.

The sampling interval is based upon the expected rate of material change, which may be influenced based upon the qualification testing of the material. For new materials that do not have a lot of operating experience in conditions similar to the pool environment (i.e.,

their ability to perform is not well known), the initial interval of 5 years, with subsequent intervals up to 10 years is acceptable. For materials that have been used for several years in conditions similar to the pool environment (i.e., their ability to perform is well known),

and for which stability in the material condition has been documented, initial and subsequent intervals up to 10 years is acceptable. For materials with known degradation or degradation mechanisms that impact the efficacy of the neutron absorber (e.g.,

Boraflex, Carborundum, Tetrabor or other phenolic resin-based materials), a testing interval of 5 years is acceptable.

Note that the sampling interval can be longer if used in conjunction with coupons.

Sources of measurement uncertainty are to be identified and the degree of uncertainty quantified.

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11 Additional criteria for in-situ measurements depend upon the performance of the neutron absorber material, specifically whether material changes result in a degradation of the 10B areal density.

a) For materials where operating experience indicates that potential change mechanisms do not result in a loss of 10B areal density, in-situ measurements are used to confirm their presence and provide validation of the original as-manufactured areal density. Results confirm the continued performance of neutron absorber materials if the nominal measured 10B areal density is equal to or greater than the 10B areal density assumed in the criticality analysis, within the uncertainties of the measurement.

b) For materials where operating experience indicates that degradation mechanisms may result in a loss of 10B areal density, in-situ measurements are used to determine the amount of 10B areal density remaining. Results confirm that potential loss of 10B has not resulted in the loss of the neutron absorber materials ability to perform its criticality control function if the nominal measured 10B areal density minus the measurement uncertainty is greater than the 10B areal density assumed in the criticality analysis.

2.4 EVALUATING NEUTRON ABSORBER TEST RESULTS For either coupon testing (and by surrogate relationship, i-LAMP) or in-situ measurements, results from neutron absorber monitoring fall within the broad categories of 1) confirmation that no material changes are occurring; 2) confirmation that anticipated changes are occurring; and/or

3) identification that unanticipated changes are occurring. Relevant processes are used to evaluate results of the monitoring program with the criticality analysis input. If no changes, or if anticipated changes are occurring that have already been accounted for, then the material condition continues to be adequately represented in the criticality analysis.

If unanticipated changes are identified (either new mechanisms or anticipated mechanisms at rates or levels beyond those anticipated), then additional actions may be necessary. In addition to relevant regulatory and licensing processes (e.g., corrective action program, reporting requirements, the 10 CFR 50.59 [5] process, operability determination or functionality assessment), the following technical evaluations may be necessary:

Determine if unanticipated changes could result in a loss of 10B areal density. Evaluation of the effects of 10B areal density on the criticality analysis are to be performed and addressed through appropriate licensee processes. Additionally, monitoring or test results that indicate potential degradation are evaluated and trended, even if it does not challenge the criticality safety analysis.

Determine if unanticipated changes not resulting in loss of 10B areal density have an impact on the criticality analyses. Dimensional or non-neutron absorbing material changes (e.g., formation of gaps, localized displacement of moderator, or superficial scratches) may have no or little impact on the criticality analyses. However, the potential effects of these changes on the criticality analysis are evaluated and addressed through appropriate licensee processes.

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12 3 REFERENCES 3.1 REGULATIONS

1.

Title 10 of the Code of Federal Regulations (10 CFR) 50 Appendix A, General Design Criteria for Nuclear Power Plants Criterion 61, Fuel Storage and Handling and Radioactivity Control.

2.

Title 10 of the Code of Federal Regulations (10 CFR) 50 Appendix A, General Design Criteria for Nuclear Power Plants Criterion 62, Prevention of Criticality in Fuel Storage and Handling.

3.

Title 10 of the Code of Federal Regulations (10 CFR) 50 Appendix B, Quality Assurance for Nuclear Power Plants and Fuel Reprocessing Plants.

4.

Title 10 of the Code of Federal Regulations (10 CFR) 50.36, Technical Specifications.

5.

Title 10 of the Code of Federal Regulations (10 CFR) 50.59, Changes, Tests and Experiments.

3.2 NUREGS

6.

NUREG-0800, Standard Review Plan for the Review of Safety Analysis Reports for Nuclear Power Plants: LWR Edition, Section 9.1.1, Criticality Safety of Fresh and Spent Fuel Storage and Handling, Revision 3, March 2007.

7.

NUREG-0800, Standard Review Plan for the Review of Safety Analysis Reports for Nuclear Power Plants: LWR Edition, Section 9.1.2, New and Spent Fuel Storage, Revision 4, March 2007.

8.

NUREG-1801, Generic Aging Lessons Learned (GALL) Report, Revision 2, December 2010.

3.3 OTHER

9.

NEI 16-03, Guidance for Monitoring of Fixed Neutron Absorbers in Spent Fuel Pools, Revision 0-A, May 2017, ML17263A133.

10.

Handbook of Neutron Absorber Materials for Spent Nuclear Fuel Storage and Transportation Applications, Revision 1: 2022 Update. EPRI, Palo Alto, CA: 2022.

3002018496.

11.

NRR Office Instruction, LIC-500, Revision 5, Topical Report Process, ML13158A296.

12.

Roadmap for Industrywide Learning Aging Monitoring Program (i-LAMP): For Neutron Absorber Materials in Spent Fuel Pools. EPRI, Palo Alto, CA: 2018.

3002013122.

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13

13.

Pham, B.M., Closeout of Generic Letter 2016-01, Monitoring of Neutron-Absorbing Materials in Spent Fuel Pools, U.S. NRC Memorandum, December 2018. ADAMS Accession No. ML18332A316.

14.

Evaluation of the Impact of Neutron Absorber Material Blistering and Pitting on Spent Fuel Pool Reactivity. EPRI, Palo Alto, CA: 2018. 3002013119.

15.

Industrywide Learning Aging Management Program (i-LAMP): Global Neutron Absorber Material Monitoring Program for Spent Fuel Pools. EPRI, Palo Alto, CA:

2022. 3002018497.

16.

Acceptance Review for Nuclear Energy Institute Document NEI 16-03, Revision 1, Guidance for Monitoring of Fixed Neutron Absorbers in Spent Fuel Pools, (EPID L-2022-NTR-0002), December 2, 2022, ADAMS Accession No. ML22301A179.

17.

Characterization and Analysis of Boral from the Zion Nuclear Power Plant Spent Fuel Pool, SRNL-TR-2018-00244, Revision 0, March 2019. ADAMS Accession No. ML19155A215.

18.

Pressurized Water Reactor Primary Water Chemistry Guidelines: Volume 1, Revision

7. EPRI, Palo Alto, CA: 2014. 3002000505.

19.

BWRVIP-190 Revision 1: BWR Vessel and Internals Project, Volume 1: BWR Water Chemistry Guidelines - Mandatory, Needed, and Good Practice Guidance. EPRI, Palo Alto, CA: 2014. 3002002623.

20.

NEI letter to NRC, Response to NRC Request for Additional Information Supporting the Review of NEI 16-03, Rev. 1 Guidance for Monitoring of Fixed Neutron Absorbers in Spent Fuel Pools (EPID L-2022-NTR-0002).

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14 APPENDIX A: INDUSTRYWIDE LEARNING AGING MANAGEMENT PROGRAM (I-LAMP): GLOBAL NEUTRON ABSORBER MATERIAL MONITORING PROGRAM FOR SPENT FUEL POOLS In response to NRCs letter, dated December 2, 2022 [A1], relevant sections of EPRIs i-LAMP report [A2], with EPRIs permission, are reproduced in this appendix.

A.1 I-LAMP DEVELOPMENT3 There are a number of SFPs that use BORAL as a neutron absorber material and do not have a coupon monitoring program, or with a limited number of coupon samples remaining [A3]. Given the fact that many of the SFPs have similar properties and exposure, EPRI proposed to initiate an industrywide Learning Aging Management Program (i-LAMP) as an alternative monitoring approach for neutron absorber materials in SFPs [A4].

For a given neutron absorber material, aging effects in SFPs are a function of:

1) Type and vintage of the material

2) Time in the SFP

3) SFP water chemistry

4) Temperature

5) Cumulative neutron dose

6) Cumulative gamma dose It should be noted that for different materials, the significance of the listed factors can vary. For example, for materials like Boraflex, cumulative gamma dose was the primary factor for degradation. It should also be noted that increased silica levels in measured water chemistry indicated the potential degradation and are used for quantification of the degradation.

SFP water chemistry is maintained based on EPRI guidelines, which were primarily developed for minimizing fuel degradation.

A.1.1 Overview of Neutron Absorber Materials and Monitoring Status in i-LAMP The status of NAMs as a function of areal density is shown in Figure A.1. In this figure:

1) Boraflex, Carborundum, and Tetrabor are not shown as these materials are not part of the proposed i-LAMP program.

2) For the case of BORAL, separated into two categories: SFPs with and without an existing coupon monitoring program. This categorization allows:

3 This section is reproduced, with minor revisions, from Section 4 of EPRIs i-LAMP report [A2], with EPRIs permission.

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15 a) Determination of how many SFPs do not have a coupon monitoring program.

b) Determination of whether SFPs without coupons are bounded by the SFPs with coupons in terms of areal density and installation year.

As is evident from Figure A.1, for BORAL, in terms of areal density, all the SFPs without coupons are bounded by the SFPs with coupons.

Figure A. 1: Distribution of NAMs as a function of areal density The status of NAMs as a function of installation year are presented in Figure A. 2. It should be noted that manufacturing and installation years may be different, in some instances, even substantially different, pending on the history of the panels. In the U.S. there are two SFPs with unique history where there is significant difference between installation and manufacturing years. These two unique SFPs are discussed in detail in Appendix A.2 and Appendix A.3.1.

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16 Figure A. 2: Distribution of NAMs as a function of installation year A.1.2 SFP Water Chemistry The SFP water chemistry is monitored at regular intervals at all the SFPs in the U.S. and in many of the countries around the world. SFP water chemistry measurements serve two purposes:

Ensuring compliance with water chemistry guidelines for corrosion. The EPRI PWR and BWR water chemistry guidelines [A5, A6] recommend Chloride (Cl), Fluoride (F), and Sulfate (SO4) levels below 150 ppb to reduce the corrosion potential. The guidelines were developed primarily to reduce corrosion of the fuel.

As a monitoring tool, when there are anomalies, the chemistry levels will be an early indicator. For example, boraflex degradation was first identified when SFP silica levels were elevated.

In other programs (for example, vessel integrity, steam generator integrity), water chemistry is used as a part an of industrywide monitoring program for the same purpose.

The collected water chemistry data include all the measured parameters for each pool. The parameters that are measured and recorded include:

pH

Conductivity

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17

Chloride (Cl) concentration

Fluoride (F) concentration

Sulfate (SO4) concentration Additionally, for PWRs

Boron (B) concentration

Sodium (Na) concentration For pools that still have Boraflex, silica levels are also measured. Very few pools also measure Aluminum (Al) but the majority of utilities discontinued this practice because Al levels were usually below detectable limits. At this time, no additional measurements are required.

The historic SFP water chemistry data from all U.S. utilities and other participating countries (for example, Mexico, Taiwan, S. Korea, U.K.) was collected. The water chemistry database is being updated with new data approximately every six months.

A.1.3 SFP Coupon Database The SFP coupon database is developed to collect the data, analyze the data to determine bounding conditions (changes in areal density, maximum observed blisters/pit sizes to date),

trends (as a function of time in service), and any potential relation between potential degradation and SFP water chemistry and other parameters.

The data that are being extracted from coupon reports currently include:

Pool name

Rack installation year

Rack type (egg crate versus flux trap)

Stainless steel encapsulation or not

Coupon unique ID number

Coupon analysis year(s), if the same coupon is analyzed multiple times

Dimension data (pre-characterization and post-irradiation) o Height, width, thickness o Weight o Areal density values (pre-characterization and post-irradiation) o Pit and blister data

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18 A.1.4 SFPs with No Coupons To develop an industrywide monitoring program and develop sibling pool criteria for the entire fleet of SFPs, basic information on neutron absorber materials from all the participating SFPs was gathered. This data collection and analysis allowed the development of sibling pool criteria.

Therefore, for SFPs without a coupon program, some of the basic information related to neutron absorber materials was collected and analyzed. The basic information needed for SFPs without coupons includes, but is not limited to:

Neutron absorber material areal density values

Neutron absorber material thickness

Manufacturing and installation year

Manufacturer and vendor information may also be needed Additionally, if it is determined that the NAM properties in this category are not bounded by the NAM properties in SFPs with coupons category, additional analysis will be needed. The scope of the additional analysis can be determined after the completion of the data collection and analysis of the range of variations. An example for this case is illustrated in Appendix A.3.1 for implementation of i-LAMP via case studies.

A.1.5 Synergy Effects As part of the investigation to determine if there are synergistic effects that cause degradation, water chemistry data was compared against blister and pit results from coupons. Similarly, the progression of blisters and pits over time was analyzed. To date, no trending is found between the degradation for:

Coupons in PWR versus BWR pools. This is consistent with the results obtained from the laboratory tests using accelerated corrosion [A7, A8, A9]. It should be noted that while accelerated corrosion coupons showed increased number of pits for PWR coupons, compared to BWR coupons, it did not show any adverse impact on the measured areal density. The results from accelerated corrosion tests were especially important for clad removed coupons, which indicated no loss of absorber over five years for coupons in PWR and BWR test baths.

Degradation rate over time - The analysis indicated no trends, to date, for the change in degradation rate over time for the coupons. Evaluation of neutron absorber panels, with unique history, from an operating SFP are presented in Appendix A.2 and the results confirm that degradation rate over time is not showing trends to date. There are not many results where the same coupon was evaluated over the years4. One of the exceptions is the blister formation trending over time for a coupon in one of the operating SFPs. For this coupon, blister height measurements were taken between 1991 and 2017, at certain 4 Prior to Zion comparative analysis project, utilities were mostly discarding the coupons after analysis since coupons were dried. After Zion project, EPRI recommended to stop drying and re-inserting the coupons to the SFP.

This recommendation was approved by the NRC.

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19 intervals. The results were presented in [A4] and reproduced in Figure A.3. In this figure, F-1 to F-4 represent the blisters on the front side of the coupon and B-1 to B-2 represent the blisters on the back of the coupon. As is evident from the figure, there is not much change in blister height over time.

Figure A. 3: Blister height as a function of measurement year A.1.6 Sibling Pool Criteria When i-LAMP was proposed, EPRI proposed to analyze the data from SFP water chemistry, coupon results and establish sibling pool criteria based on the analysis results. This was done by asking two primary questions to determine the similarities between SFPs:

1) How similar are the NAM characteristics? This refers to the similarities between:

Areal density values NAM thickness NAM manufacturing and installation years

2) How similar is the water chemistry data between SFPs? This refers to the similarities between:

Boron levels (PWR versus BWR as the first step)

Cl, F, Sulfate levels (as they are considered corrosion accelerant)

Other chemistry parameters (for example silica levels)

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20 Based on the analysis, pools with similar characteristics were categorized, as is evident from the graphs presented in Figure A.1 and Figure A.2, for NAM characteristics. Water chemistry data for these pools were compared against each other to further evaluate and determine if indeed they are similar.

However, given that as of today, no trending is established, for this phase, implementation of i-LAMP is proposed using only two bins, as is discussed in Section A.4.

A.2 AUGMENTATION AND BOUNDING OF I-LAMP VIA EVALUATION OF PANELS FROM AN OPERATING SPENT FUEL POOL5 Recently, one utility, due to regulatory commitments made prior to the i-LAMP proposal, removed two BORAL panels from an operating SFP to develop a NAM aging management program based on coupon monitoring [A10]. Following removal of BORAL panels, the utility cut coupons from both panels and shared some of the samples with EPRI for independent analysis. This section describes the panels, panel in-service history, SFP water chemistry history, and areal density values for the samples.

The two BORAL panels, removed from an operating SFP, are unique for the following reasons

[A10]:

Age of the panels: The panels are over 40 years old and therefore bound the entire industry, with one exception.

History of the panels: These panels resided in two different operating SFPs with transportation and dry storage time in between the two in-service SFP periods.

Water chemistry: Compared to industry averages, SFP water chemistry shows relatively higher levels of boron concentration.

A.2.1 History of the Panels The panels removed from this pool have a unique history. Not only are these panels representing some of the oldest panels (over 40 years old), but through their lifetime have been placed in two different SFPs as well as stayed out of pool for ~2 years (wet-dry-wet) [A10]. These panels also represent the vintage that was assumed to be prone to blistering due to their age.

The history of these panels is summarized in Figure A.4. As summarized in the figure:

The BORAL panels were manufactured by AAR and Brooks and Perkins in 1979.

Rack modules were initially installed in SFP-1 in November 1980.

Rack modules were removed from SFP-1 from December 1994 to March 1995.

Rack modules were stored in a warehouse for ~2 years.

5 This section is reproduced from Section 5 of EPRIs i-LAMP report [A2], with EPRIs permission.

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21

In 1997, the racks were installed in SFP-2. Because operating experience based on coupon results was reporting blistering, the recommendation was to vent the SS encapsulation. For this purpose, prior to installation at SFP-2, holes were drilled into the upper part of the can at the top of the BORAL plates to vent the void space and allow SFP water ingress to the neutron absorber and to allow venting of gas.

Minimum certified 10B areal density is specified as 0.0233 g10B/cm2.

Nominal 10B areal density is specified as 0.0248 g10B/cm2.

Figure A. 4: Summary of the history of the panels A.2.2 Removal of the Panels Previously, EPRI removed two rack modules, representing Region 1 and Region 2 of the pool, from the Zion SFP [A11]. Because Zion was going through decommissioning and all the fuel was offloaded, rack modules were transported to a location where panels were harvested from the rack modules.

However, because SFP-2 was an operating pool, absorber panels had to be removed while the rack module was in the SFP. A special tool was constructed to enable cutting the stainless steel encapsulation under water, and panel removal. Following removal, panels were cut into 23 samples. Samples were numbered from 1 to 22, with Sample 1 referring to the bottom of the panel and Sample 22 referring to the top of the panel. The top portion, Sample 23, was shorter in size and was damaged during removal. Therefore, top portions from both panels were discarded.

Two representative samples from two BORAL panels following harvesting and sectioning are shown in Figure A.5. In this figure, Sample 12 from Panel-1 is shown on the left, and Sample 20 from Panel-2 is shown on the right. Top pictures show the front of the sample, while bottom pictures show the back of the sample. As is evident from the pictures, BORAL samples show general corrosion, flow patterns, and some pits. However, the samples do not reveal any

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22 significant degradation and are in excellent condition despite being over 40 years old and having a unique wet-dry-wet history.

It should be noted that there are no blisters on any of the samples despite the age of the panels given the expectation has been that older BORAL would be more susceptible to blistering.

Figure A. 5: Sample 12 from Panel-1 (left) and Sample 20 from Panel-2 (right)

A.2.3 Water Chemistry History Water chemistry values from the SFP where panels are currently residing (designated as SFP-2 in Figure A.4), have been collected as part of i-LAMP.

As an example, boron (B) levels over time are presented in Figure A.6. It should be noted that for this SFP, B levels are higher than the industry averages (~2000-2500 ppm) for PWR pools, which is presented in Figure A.7.

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23 Figure A. 6: Boron concentration over time for SFP-2 Figure A. 7: Distribution of B levels across the industry for PWR pools To reduce corrosion, EPRI water chemistry guidelines recommend that Cl, F, and sulfate levels should be maintained below 150 ppb [A5, A6]. Chlorine (Cl) levels over time are presented in Figure A.8. As evident from Figure A.8, Cl levels are well below 150 ppb, which is marked with

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24 a solid line. Sulfate levels over time are presented in Figure A.9. For sulfate levels, early cycles have few measurement points that are above 150 ppb, as shown in Figure A.9. The measured fluoride (F) levels over time are illustrated in Figure A.10. The inset figure shows a closer look at the distribution of the measured data. As is evident from the inset, F levels are well below 150 ppb (<10 ppb over time).

Figure A. 8: Cl levels over time Figure A. 9: Sulfate levels over time

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25 Figure A. 10: F levels over time It is clear from the data presented in these figures, water chemistry was maintained according to EPRI water chemistry guidelinesmaintaining chloride, sulfate, and fluoride levels below 150 ppb. Silica levels over time are presented in Figure A.11.

It should be noted that although dates are not shown, the data presented in Figure A.6 to Figure A.11 represent measurement data spanning over 20 years. Although B (>1000 points), Cl, sulfate, F (~450 points), and silica (~160 points) have different numbers of measured data points, the data interval is the same for all these nuclides. The differences in number of measured points are mainly due to the varying intervals for the measurement of each nuclide.

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26 Figure A. 11: Silica levels over time A.2.4 Areal Density Values For criticality safety, the most important parameter is 10B areal density. A number of these samples (15 samples/panel; 30 samples) were made available to EPRI by the utility for independent analysis. For the samples received by EPRI, 10B areal density measurements were performed at Penn State University (PSU) Breazeale Nuclear Reactor. The areal density measurements, using neutron attenuation were performed following ASTM Standard E2971-16

[A12]. With this approach, a thermal neutron beam is transmitted through neutron absorber material and compared to the calibration standards to determine the effective 10B areal density.

A.2.4.1 Areal Density Measurement Locations Areal density measurements for each sample were performed at five locations as shown in Figure A.12. Areal density measurements were performed about 2.5 cm (1 in.) away from corners for Points A, B, D, E, and at the center of the coupon, Point C.

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27 Figure A. 12: Areal density measurement locations for neutron absorber panel samples A.2.4.2 Areal Density Values for Samples from Panel-1 For Panel-1, areal density measurements for 15 samples were performed. The areal density measurement results for all the samples from Panel-1 samples are presented in Figure A.13. In this figure, areal density measurements for 75 points (15 samples/panel, 5 measurement point/sample, 75 measurement points in total) are displayed. Based on measurement results, the main observations are as follows:

The minimum certified areal density value for the panels in SFP-2 was reported as 0.0233 g10B/cm2. As is evident from Figure A.13, the areal density values for all the points for each sample from Panel-1 are above the minimum certified areal density. In fact, based on the distribution of the measured data, as shown in the figure, the minimum measured areal density is 0.0262 g10B/cm2. The maximum measured areal density is 0.028 g10B/cm2.

The nominal (mean) certified areal density value for the panels in SFP-2 was specified as 0.0248 g10B/cm2. As is evident from the figure, all the measured areal density values are above nominal specified values. Based on the measured areal density value, the mean (nominal) areal density for all the measured areal density is 0.0270 g10B/cm2.

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28 Figure A. 13: Distribution of areal density values for samples from Panel-1 Areal density measurement results for individual samples from Panel-1, for each point as described in Figure A.12, are shown together in Figure A.14. In this figure, for each sample, five areal density values are included. Point 1 refers to Panel-1, Sample-1, Point-A and Point 75 refers to Panel-1, Sample-1, Point-E.

In addition to the conclusions presented above on minimum and nominal areal density values, the main observations from the results presented in Figure A.14 include the following:

As is evident from the figure, there are variations in areal density within the same sample from Points A to E (designated as Points 1 to 5 in the graph).

Furthermore, there are variations in areal density for the samples at different axial heights.

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29 Figure A. 14: Areal density values for samples from Panel-1 To further investigate if there is any correlation between areal density variation and axial height, the average of the five areal density measurements for each sample is calculated for each sample.

The average areal density values for each sample as a function of the sample number (arranged in height order from bottom to top) are displayed in Figure A.15. As is evident from the figure, there is no clear indication of dependence of areal density as a function of axial height.

It should be noted that in Figure A.14 and Figure A.15, the error bars represent 2 values and the minimum certified areal density is marked with a solid line.

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30 Figure A. 15: Average areal density values for samples from Panel-1 as a function of sample number A.2.4.3 Areal Density Values for Samples from Panel-2 For Panel-2, areal density measurements for 15 coupons were performed. The areal density measurement results for all the samples from Panel-2 are presented in Figure A.16. In this figure, areal density measurements for 75 points (15 samples/panel, 5 measurement point/sample, 75 measurement points in total) are displayed. Based on measurement results, the main observations are as follows:

The minimum certified areal density value for the panels in SFP-2 was reported as 0.0233 g10B/cm2. As is evident from Figure A.16, the areal density values for all the points for each sample from Panel-2 are above the minimum certified areal density. In fact, based on the results presented in Figure A.16, the measured minimum areal density is 0.02531 g10B/cm2. The measured maximum areal density for samples from this panel is 0.02776 g10B/cm2.

The nominal (mean) certified areal density value is specified as 0.0248 g10B/cm2. As is evident from the figure, all the measured areal density values are above nominal specified values. Based on the measured areal density value, the mean (nominal) areal density for all the measured areal density is 0.02664 g10B/cm2.

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31 Figure A. 16: Distribution of areal density values for samples from Panel-2 Areal density measurement results for all the samples from Panel-2 for each point are shown together in Figure A.17. In this figure, 75 areal density values (5 AD/sample) are included.

In addition to the conclusions presented above on minimum and nominal areal density values, the main observations from the results presented in Figure A.17 include the following:

As is evident from the figure, there are variations in areal density within the same panel for all samples.

As is evident from the figure, there are variations in areal density within the same sample.

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32 Figure A. 17: Areal density values for samples from Panel-2 To further investigate if there is any correlation between areal density variation and axial height, the average of the five areal density measurements for each sample is calculated. The average areal density values for each sample as a function of the sample number (arranged in height order from bottom to top) are displayed in Figure A.18. As is evident from the figure, there is no clear indication of dependence of areal density as a function of axial height.

It should be noted that in Figure A.17 and Figure A.18 the error bars represent 2 values and the minimum certified areal density is marked with a solid line.

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33 Figure A. 18: Average areal density values for samples from Panel-2 as a function of sample number A.2.5 Comparison of Panels from Zion SFP and SFP-2 Given the extended operation for many plants, the specific questions surrounding fixed neutron absorber materials in SFPs included the following:

1. What are the conditions of the BORAL neutron absorber panels in SFPs? Is there any degradation such as blistering and pitting that could cause potential concern for criticality safety of the pools?

2. Is the BORAL coupon surveillance approach adequate for monitoring the conditions of the panels as part of an aging management program?

3. For plants that do not have coupons, do current in situ measurement approaches provide accurate results? Could such in situ approaches be used as an alternative monitoring approach?

To shed light on these technical questions using actual plant data, EPRI previously initiated the Zion comparative analysis project at the decommissioning of the Zion Nuclear Power Station.

As part of the Zion comparative analysis project, EPRI performed the following tasks:

1. First, removed the remaining coupons from the Zion SFP and analyzed them [A13, A14].

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34

2. Second, to ensure that all panels in the Zion SFP are represented, simulations were performed and identified panels with low, medium, and high exposure [A15]. These criteria were used for panel selection for in-situ measurements and panel removal.

3. Third, performed in-situ measurements on several panels to compare against coupon and actual panel results [A16].

4. Finally, removed several panels from both regions of the Zion SFP and analyzed them

[A11, A17, A18].

When panels were removed, an equal number of samples from each panel was shared with the NRC, under an MOU, and analyzed by SRNL [A19].

Zion rack modules were installed in 1994 and removed in 2016. Therefore, they were representing over 20 years of service time. Because the Zion SFP was shut down in 1997, panels were exposed to few cycles of freshly discharged fuel. Zion SFP had two regions, specifically Region 1 and Region 2, which had NAMs with different areal densities and thicknesses, as shown in Table A.1.

Table A. 1: Comparison of panels removed from Zion and SFP-2 Zion Region 1 Zion Region 2 SFP-2 Installation year 1994 1994 1997(1)

Service time (years)

~20

~40(2)

Number of removed panels 8

6 2

Blisters 1(3)

No No Gross degradation No No No Thickness (in.)

0.101 0.085 0.085 Minimum certified AD (g10B/cm2) 0.03 0.023 0.023 (1) Prior to installation in SFP-2, panels had previous history, as shown in Figure A.4.

(2) Wet storage time, does not include dry storage time in between SFPs.

(3) Out of 14 panels, only one panel showed a very small blister at the corner [A11].

Compared to the panels in SFP-2, Zion panels had a simple history because they were not used in two SFPs with dry storage time in between (wet-dry-wet). Furthermore, Zion panels were manufactured ~15 years after the panels in SFP-2.

Zion panels did not show any gross degradation. Out of 14 panels, only one of them showed a very small blister. Zion panel analysis also showed not only that coupons represent panels, but also that coupons show more pits compared to actual panels [A11, A18].

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35 The areal densities for Zion samples also showed variation in measured areal density in different points for the same sample but no axial dependence. In addition, the areal densities for Zion samples were also significantly higher than the minimum certified values.

Despite the differences in age and history, panels removed from Zion and SFP-2 demonstrate that BORAL panels are more robust than originally thought. Furthermore, the panels in SFP-2, despite their age, did not show any blisters, which brings the question of whether the blisters observed in operating experience are mainly due to the coupon size - compared to panel size.

A.3 DEMONSTRATION OF I-LAMP VIA CASE STUDIES6 In this section, two case studies will be presented to demonstrate how i-LAMP is applied to determine sibling pools that can be used as surrogates for SFPs without coupons. The BORAL absorber panels discussed are integral to spent fuel racks and are encapsulated within a stainless steel (SS) sheath.

A.3.1 Pilot-1 as Case Study The BORAL residing in Pilot-1 has a unique history, similar to the history described in Section A.2. Pilot plant history and comparison to a sibling pool are presented in this section.

A3.1.1 History of Pilot Plant 1 and Comparison to SFP-1 The history of the Sibling-1 (top) and Pilot-1 (bottom) panels is summarized in Figure A.19

[A20]. As is evident from the figure, the panels now residing in SFP-2 and SFP-B have very similar histories:

Panels resided in two different SFPs (SFP-1 SFP-2; SFP-A SFP-B).

Transportation and varying storage time in between two SFPs (wet-dry-wet).

As discussed in detail in Section A.2, due to regulatory commitments made prior to the i-LAMP proposal, SFP-2 removed two BORAL panels from an operating SFP to develop a NAM aging management program based on coupon monitoring. Sibling-1 denotes the SFP from which the panels were removed (SFP-2). As presented in the previous section, despite being over 40 years old and having a unique wet-dry-wet history, BORAL panels removed from Sibling-1 showed no blisters or sign of significant degradation.

It should be noted that although Pilot-1 and Sibling-1 areal densities are similar, there is a slight difference in the thickness of the panels.

6This section is reproduced from Section 6 of EPRIs i-LAMP report [A2], with EPRIs permission.

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36 Figure A. 19: Panel history for panels residing in Sibling Pool (top) and Pilot-1 (bottom)

A.3.1.2 NAM Specifications for Pilot Plant 1 and Comparison to SFP-1 The specifications for the surrogate pool and pilot pool are summarized in Table A.2. As is evident from the table, although the BORAL in the pilot pool is older, the sibling pool BORAL has more service time, meaning it resided in pools for a longer period. The BORAL in both pools is manufactured by the same company.

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37 Table A. 2: Summary of the specifications for sibling pool and pilot pool Sibling Pool Pilot Pool 1 Type PWR PWR Manufacturer AAR and Brooks and Perkins AAR and Brooks and Perkins Age (as of 2022) 43 47 Total service time (wet) 39 31 A.3.1.3 Water Chemistry for Pilot-1 and Comparison to Sibling-1 In this section, water chemistry values for the pilot SFP compared to sibling SFP are presented.

Water chemistry data for both SFPs are based on the data from the second SFP, where panels resided. It should be noted that although the water chemistry history covers the same time period, the number of data points varies between the two pools. This is mainly because different pools use different intervals for water chemistry measurements. Furthermore, measurement intervals vary for different nuclides.

The boron levels for two pools are presented in Figure A.20. In this figure, the boron levels for the sibling pool are shown in top figure while boron levels for the pilot pool are presented in the bottom figure. As is evident from the figure, B levels for the pilot pool are lower than for the sibling pool.

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38 Figure A. 20: B levels for SFP-2 (top) and Pilot Plant 1, SFP-B (bottom)

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39 The Cl levels for the sibling pool (top) and pilot pool (bottom) are presented in Figure A.21. In these graphs, the recommended limit of 150 ppb is marked by a dark blue solid line. As is clear from the figure, for both pools Cl levels are well below the recommended level of 150 ppb.

Figure A. 21: Cl levels for SFP-2 (top) and Pilot Plant 1, SFP-B (bottom)

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40 The sulfate levels for the two pools are presented in Figure A.22. In this figure, the sibling pool is shown on the top while the pilot pool is shown on the bottom. In terms of sulfate levels, earlier in the history, the sibling pool has several points that are above the recommended value of 150 ppb, which is shown with a dark blue solid line. The sulfate levels for the pilot pool are well below the recommended level, as is evident from the figure.

Figure A. 22: Sulfate levels for SFP-2 (top) and Pilot Plant 1, SFP-B (bottom)

The F levels for the sibling pool (top) and pilot pool (bottom) are presented in Figure A.23. As shown in the figure, the F levels for both pools are well below the recommended value of 150

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41 ppb, which is shown with a solid dark blue line. Since the F levels are well below recommended values, a closer look for the sibling pool and pilot pool are also shown in the inset of corresponding figures.

Figure A. 23: F levels for SFP-2 (top) and Pilot Plant 1, SFP-B (bottom)

The silica levels for two pools are presented in Figure A.24. In this figure, the sibling pool is shown on the top while the pilot pool is shown on the bottom figure. As evident from the graphs, there is significant difference in silica levels between the two pools. This is mainly due to the fact that the pilot pool had a history of Boraflex and the remnants of the Boraflex is contributing to increased silica levels.

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42 Figure A. 24: Silica levels for SFP-2 (top) and Pilot Plant 1, SFP-B (bottom)

The minimum, maximum, and average B, Cl, sulfate, F, and silica levels for these two pools are tabulated in Table A.3. As is evident from the graphs presented in Figure A.20 to Figure A.24 as well as values tabulated in Table A.3, there are two main differences between the sibling pool and pilot plant 1 water chemistry:

1) Boron levels between the two pools

2) Silica levels between the two pools

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43 Other water chemistry values, specifically Cl, F, and sulfate levels between the two pools are very similar and well below the recommended values (150 ppb).

Table A. 3: Summary of water chemistry levels for Sibling-1 and Pilot-1 SP-1 P-1 B levels (ppm)

Minimum 3075 2205 Average 3176 2517 Maximum 3292 2674 Cl levels (ppb)

Minimum 0.40 0.70 Average 7.48 8.26 Maximum 64.00 32.10 Sulfate levels (ppb)

Minimum 0.31 0.0 Average 49.21 7.64 Maximum 184.00 66.00 F levels (ppb)

Minimum 0.20 0.10 Average 1.98 6.37 Maximum 10.00 45.00 Silica levels (ppb)

Minimum 47.00 0.0 Average 177.09 5749 Maximum 440.00 18100 A.3.1.4 Proposed Approach for Pilot-1 and Benefits of the Proposed Approach If i-LAMP is approved by the regulator as a replacement for Pilot-1s current commitments, instead of simply proposing to use Sibling-1 as surrogate for Pilot-1, proposing the following:

1. Take some of the remaining coupons from Sibling-1 and transfer to Pilot-1 pool

2. Pilot-1 builds a coupon tree

3. Keep half of coupons bare and encapsulate the other half of the coupons

4. Place them on coupon tree and install in Pilot-1 pool

5. Develop an aging management program based on coupons.

This proposed approach has benefits for i-LAMP, Sibling-1, and Pilot-1, as summarized in Figure A.25, and as follows:

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1. One fewer SFP without a coupon monitoring program.

2. Increased number of coupons across the industry - beneficial for the health of i-LAMP.

3. Opportunity to evaluate the impact of coupon size on the formation of blisters in two SFPs

4. Opportunity to evaluate the impact of SS encapsulation versus bare coupons

5. Opportunity to evaluate the impact of higher boron levels in Sibling-1 versus higher silica levels in Pilot-1.

Figure A. 25: Benefits of the proposed approach for Pilot-1, Sibling-1, and i-LAMP A.3.2 Pilot-2 as Case Study Pilot-2 is selected as a case study to further illustrate how surrogate pools are determined and will be used as part of i-LAMP implementation. A description of NAM for Pilot-2 and its surrogates is presented in the following section. Water chemistry for Pilot-2 and sibling pools is presented in Section A.3.2.2.

A.3.2.1 Description and Specifications for Pilot-2 and Siblings For Pilot-2, two currently operating SFPs with an existing coupon monitoring program were identified as siblings that can be used as surrogates. A summary of the NAM specifications for Pilot-2, Sibling-1 and Sibling-2 are listed in Table A.4. The main observations are as follows:

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Pilot-2, where panels were installed in 1999, is bounded by two siblings that have coupon monitoring programs o Panels in Sibling-1 are older, installed in 1993 o Sibling-2 panels were installed ~3 years after Pilot-1 panels

It should be noted that Pilot-2 panels are also very similar to Zion Region-1 panels, as is evident from Table A.1 in the previous section.

o Older installation date (1994 installation for Zion panels) but the same thickness and minimum certified areal density

Several other pools do not have coupons but have very similar characteristics to Pilot-2; therefore, similar to Sibling-1 and Sibling-2.

Table A. 4: Summary of the NAM specifications for Pilot-2 and identified siblings Pilot-2(1)

Sibling-1 Sibling-2 Installation year 1999 1993 2003 Thickness (in.)

0.101 0.101 0.101 Minimum certified AD (g10B/cm2) 0.03 0.03 0.03 Existing coupon monitoring program No Yes(2)

Yes(3)

(1) Pilot-2 characteristics are very similar to Zion panels, installed in 1994, and Pilot-1 new Boral, installed in 1998.

(2) Coupons analyzed to date showed no blisters. Furthermore, coupons to date showed no signs of gross degradation or more importantly, any decrease in areal density.

(3) Observed pitting and several blisters on some coupons. No gross degradation or decrease in areal density.

A.3.2.2 Water Chemistries for Pilot-2 and Sibling Pools Boron levels for Pilot-2 and sibling pools are presented in Figure A.26. As is evident from the graphs presented in this figure, boron levels for Pilot-2 (left), Sibling-1 (center), and Sibling-2 (right) are very similar. Furthermore, boron levels for all three pools are more consistent with the industry averages (~2500 ppm).

Cl levels for Pilot-2 and sibling pools are presented in Figure A.27. The measured data presented in these graphs show that the Cl levels for Pilot-2 (left), Sibling-1 (center), and Sibling-2 (right) are well below the recommended values (<150 ppb). In fact, as is clear from the data, the maximum Cl level across these three pools is below 15 ppb.

Silica levels for Pilot-2 (left), Sibling-1 (center) and Sibling-2 are illustrated in Figure A.28.

Although Pilot-2 and Sibling-1 have similar silica levels (~200 ppb), Sibling-2 silica levels were relatively higher early in the history. However, Sibling-2 silica levels decreased substantially over time.

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46 In summary, as supported by the data shown in these figures, Pilot-2 and Sibling-1 and Sibling-2 have similar water chemistry histories except for early silica levels for Sibling-2.

Figure A. 26: Boron levels for Pilot-2 (left), Sibling-1 (center), and Sibling-2 (right) over time Figure A. 27: Cl levels for Pilot-2 (left), Sibling-1 (center), and Sibling-2 (right) over time Figure A. 28: Silica levels for Pilot-2 (left), Sibling-1 (center), and Sibling-2 (right) over time

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47 A.4 PROPOSED IMPLEMENTATION7 Based on the key findings from major research projects conducted by EPRI within the past ~10 years, and all the data collected from the industry across the globe, it is evident that BORAL is a far more robust material than initially thought and there are currently no safety significant issues for BORAL aging management. This means there is no loss of NAM function associated with any of the key sibling identification variables. Because of this, a very simple industry-wide binning approach can be used at this time instead of sibling identification. If in the future, further binning is required, this will be done as i-LAMP has been constructed as a learning aging management program.

Updated NAM status, including data from non-U.S. SFPs, as a function of credited areal density is presented in Figure A.29. Compared to Figure A.1, the changes in this figure include:

1 SFP from the U.S. moved from No-Coupon category to Coupon category, based on the results presented in Section A.2

1 SFP from Europe added to No-Coupon category

Added data from 2 SFPs, from North America (non-U.S.), to Coupon category

Added data from 8 SFPs, from Asia, to Coupon category Metamic, Boralcan, and MAXUS are relatively newer NAMs and have coupon monitoring programs. For BORAL, there are a number of SFPs without coupon monitoring programs -

labeled as BORAL (no coupon) in the figure. As shown in the figure, SFPs without coupons are bounded by the SFPs with coupons and could use the sibling identification method provided service time, age, and water chemistries are similar.

7This section is reproduced from Section 7 of EPRIs i-LAMP report [A2], with EPRIs permission.

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48 Figure A. 29: Updated NAM status as a function of areal density However, taking advantage of the robust performance of all BORAL, in the first phase of the i-LAMP implementation we propose having only two bins for BORAL:

Bin 1 - SFPs with coupons

Bin 2 - SFPs without coupons Since i-LAMP is a learning aging management program, the number of bins will be refined if/when needed. The proposed two-bin approach will eliminate significant burden from all stakeholders, industry and the NRC, since it would not require plant-specific sibling identification, associated regulatory submissions, and plant-specific review by the regulator.

A.5 EXAMPLE SURROGATE APPROACHES AS PART OF MONITORING AND AGING MANAGEMENT PROGRAMS8 In this section, a few examples in which surrogate data is used for satisfying monitoring requirements as part of aging management programs are presented.

A.5.1 High Burnup (HBU) Demonstration Project The technical basis for dry storage of low burnup fuel was established primarily through the demonstrations at Idaho National Laboratory (INL) in the mid-1980s through early 1990s and the CASTOR-V/21Demonstration Cask that was reopened at INL in 2000 [A21]. For decades, 8This section is reproduced from Section 3 of EPRIs i-LAMP report [A2], with EPRIs permission.

NEI 16-03-A, Revision 1 August 2023

49 low burnup fuel (<45 GWD/MTU) was being placed into dry cask storage. However, with the industry trends, a technical basis for HBU fuel storage was needed. The technical basis for dry storage of HBU fuel was developed based on laboratory testing to allow dry storage of HBU fuel to begin. This technical basis is documented in U.S. Nuclear Regulatory Commission (NRC)

Interim Staff Guidance (ISG) 11, Revision 3 [A22]. With the technical basis established, storage of high burnup fuel (> 45 GWD/MTU) in dry storage casks then began in 2004 in the U.S.

Due to the expanded use of dry storage for high burnup fuel, its different characteristics compared to low burnup fuel, and the lack of data on the behavior of HBU fuel under actual dry storage conditions (vs. lab conditions), similar data on high burnup fuel from a demonstration cask were desired to support Independent Spent Fuel Storage Installation (ISFSI) license renewals as well as transportation licenses. Many organizations across the globe saw the need for such a high burnup demonstration cask. The Extended Storage Collaboration Program (ESCP) led by EPRI began developing plans for a long-term demonstration program for HBU fuel in 2010 [A23] and created a High Burnup Demo subcommittee to address this need.

In 2013, the U.S. Department of Energy (DOE) initiated the High Burnup Dry Storage Cask Research and Development Project to design and implement a high burnup, large scale, long term, dry storage cask research and development project for spent nuclear fuel. The project is led by EPRI. Participants in the project include the host utility Dominion Energy Virginia; technology vendors Orano (formerly AREVA), Framatome (formerly AREVA), Westinghouse, and NAC International; and six DOE national laboratories.

The overview of the HBU demonstration project includes [A24]:

Loading a cask with 32 HBU assemblies at Dominion Energys North Anna Power Station

Including four different cladding types; Zircaloy-4, low-tin Zircaloy-4, ZIRLO' and M5

Collecting temperature data and gas samples

Providing 25 sister rods for pre-characterization The High Burnup Research Project cask was successfully loaded in November 2017 and began collecting data on the performance of HBU fuel under actual dry storage conditions. The loading of the cask and the initial results were presented in detail in EPRI 3002015076 [A24].

The project is expected to continue for at least a decade with plans to open the cask after about 10 years of storage to examine the condition of the cladding after storage. The data from the project was used for blind benchmarking of thermal models [A25] and opened to the international community for code validation [A26]. The aim of the ongoing activities is to support license renewals and new licenses for dry storage facilities, support transportation licensing for HBU fuel, and to provide input to future cask designs.

NEI 16-03-A, Revision 1 August 2023

50 The HBU demonstration project was used to support license renewals of ISFSIs even before cask loading and initial data collection. As an example, text from Calvert Cliffs ISFSI conditional approval is included below [A27]:

Exelon Generation shall submit an evaluation of the results of the confirmatory evaluation related to high burnup fuel cladding performance specified in the High Burnup Fuel Aging Management Program in Attachment 2 to the Response to Fourth Request for Additional Information for Renewal Application, in a letter to the NRC (submitted pursuant to 10 CFR 72.4), by April 30, 2028. The evaluation shall include an assessment of the ability of stored high burnup fuel assemblies to continue to perform the intended function(s). If the licensee identifies fuel which is unable to perform the intended function(s), the licensee shall cease use of such cask or submit a license amendment request to modify this license condition.

A.5.2 Dry Cask Storage Aging Management The objective of NEI 14-03, Guidance for Operations-Based Aging Management for Dry Cask Storage [A28], is to facilitate a consistent approach to the preparation of 10 CFR 72 license and CoC renewal applications given that there is currently a limited amount of operational and research data available on aging mechanisms that could affect dry cask storage structures, systems and components (SSCs). Its purpose is to complement the 10 CFR 72 license and Certificate of Compliance (CoC) renewal review guidance in NUREG-1927, Standard Review Plan for Renewal of Specific Licenses and Certificates of Compliance for Dry Storage of Spent Nuclear Fuel [A29], specifically

Section 3.0, Aging Management Review

Section 1.4.4, Application Content

Section 1.4.6, Amendment Applications Submitted During the Renewal Review or After the Renewal is Issued Additionally, the industry determined that it would be beneficial to develop additional clarifying guidance for the format and content of renewal applications. For this purpose, it provides guidance on format, content, and implementation.

NEI 14-03 definition of surrogate is [A28]:

Surrogate - A DSS or other ISFSI SSC that has been determined by the licensee or CoC holder to provide applicable monitoring or inspection information for other similarly situated components based on its geographic location, length of service and other criteria deemed appropriate by the stakeholders. A surrogate could also be part of a research and development program evaluating relevant aging-related degradation mechanisms not necessarily co-located at an ISFSI site (e.g., a laboratory).

In July 2021, NRC endorsed NEI 14-03, Revision 2 via Regulatory Guide 3.76, Implementation of Aging Management Requirements for Spent Fuel Storage Systems, [A30] with clarifications.

NEI 16-03-A, Revision 1 August 2023

51 NUREG-1927 states that:

The reviewer may accept the use of surrogate inspections (inspections conducted at other sites as a substitute for inspections conducted at the site(s) within the subject license or CoC) for identifying the relevant aging mechanisms and effects in the renewal application, but only when the technical basis is supported by substantial operating experience. Differences in materials, fabrication practices, design modifications, and environmental conditions at various sites could make comparisons between different ISFSI sites invalid.

Degradation mechanisms for stainless steel are a function of environment, material (stainless steel type), and stress. Inspection technology for DCS is relatively new, with only 4-5 years of experience. Consequently, to date, only a few inspections across the U.S. have been performed and not enough variations have been sampled. When enough operating experience provides basis, surrogates will be accepted as stated in NUREG-1927.

A.5.3 Aging Management Programs for Reactor Pressure Vessel Reactor pressure vessel integrity programs are called RPV integrity project for PWRs [A31], and BWRVIP - BWR vessel integrity project for BWRs [A32]. While there are variations between the two programs, both programs also rely on plant specific water chemistry for reactor and surrogate inspections.

In fact, part 50.61 states that Surveillance program results means any data that demonstrates the embrittlement trends for the limiting beltline material, including but not limited to data from test reactors or from surveillance programs at other plants with or without surveillance program integrated per 10 CFR part 50, appendix H. [A33].

For example, the Calvert Cliffs license relied on data from McGuire station [A34] and Beaver Valley relied on data from other sites [A35].

A.6 APPENDIX A REFERENCES A1.

Acceptance Review for Nuclear Energy Institute Document NEI 16-03, Revision 1 Guidance for Monitoring of Fixed Neutron Absorbers in Spent Fuel Pools, (EPID L-2022-NTR-0002), December 2, 2022, ADAMS Accession No. ML22301A179.

A2.

Industrywide Learning Aging Management Program (i-LAMP): Global Neutron Absorber Material Monitoring Program for Spent Fuel Pools. EPRI, Palo Alto, CA:

2022. 3002018497.

A3.

H. Akkurt and A. Jenks, Toward a Global Monitoring Program for Neutron Absorber Material Monitoring in Spent Fuel Pools, Trans. Am. Nuc. Soc., 124, 94-95, (2021).

A4.

Roadmap for Industrywide Learning Aging Monitoring Program (i-LAMP): For Neutron Absorber Materials in Spent Fuel Pools. EPRI, Palo Alto, CA: 2018.

3002013122.

A5.

Pressurized Water Reactor Primary Water Chemistry Guidelines: Volume 1, Revision

7. EPRI, Palo Alto, CA: 2014. 3002000505.

NEI 16-03-A, Revision 1 August 2023

52 A6.

BWRVIP-190 Revision 1: BWR Vessel and Internals Project, Volume 1: BWR Water Chemistry Guidelines - Mandatory, Needed, and Good Practice Guidance. EPRI, Palo Alto, CA: 2014. 3002002623.

A7.

H. Akkurt, EPRIs Accelerated Corrosion Tests and Analysis of Pits and Blisters for BORAL Coupons, Trans. Am. Nuc. Soc., 123, 219-222, (2020).

A8.

H. Akkurt, A. Quigley, and M. Harris, "Accelerated Corrosion Tests to Evaluate the Long-Term Performance of BORAL in Spent Fuel Pools, Proceedings of PATRAM 2019 Conference, New Orleans, LA, August 2019.

A9.

Akkurt, H., A. Quigley, and M. Harris, "Accelerated Corrosion Tests for the Evaluation of Long-Term Performance of Boral in Spent Fuel Pools, Radwaste Solutions, V 25, No 1, 41-43, Spring 2018.

A10. H. Akkurt, Augmentation and Bounding of i-LAMP via Addition of Panels from an Operating Spent Fuel Pool, Trans. Am. Nuc. Soc., 125, 144-147, (2021).

A11. Evaluation of BORAL Panels from Zion Spent Fuel Pool and Comparison to Zion Coupons. EPRI, Palo Alto, CA: 2016. 3002008196.

A12. ASTM E2971-16, Standard Test Method for Determination of Effective Boron-10 Areal Density in Aluminum Neutron Absorbers using Neutron Attenuation Measurements. ASTM International, West Conshohocken, PA, 2016.

A13. Evaluation of BORAL Coupons from Zion Spent Fuel Pool. EPRI, Palo Alto, CA:

2016. 3002008195.

A14. H. Akkurt, S. Feuerstein, M. Harris, and A. Quigley, Analysis of BORAL Coupons from Zion Spent Fuel Pool, Transactions of the American Nuclear Society. 113, 372-375 (2015).

A15. Evaluation and Selection of Neutron Absorber Panels for the Zion Comparative Analysis Project. EPRI, Palo Alto, CA: 2017. 3002010611.

A16. H. Akkurt, S. Feuerstein, M. Harris, and S. Baker, Overview of Zion Comparative Analysis Project for Assessment of BORAL Neutron Absorber Material Performance and Monitoring in Spent Fuel Pools, Proceedings of the ANS Conference: 2015 International Conference on Nuclear Criticality Safety. Charlotte, NC (September 13-17, 2015).

A17. H. Akkurt, M. Harris, A. Quigley, Evaluation of Neutron Absorber Panels from Zion Spent Fuel Pool, Transactions of the American Nuclear Society. 115, 645-647 (2016).

A18. H. Akkurt, Comparison of Neutron Absorber Panels and Monitoring Coupons from Zion Spent Fuel Pool, Proc. of International High-Level Radioactive Waste Management (IHLRWM 2017), April 2017, Charlotte, NC.

A19. Characterization and Analysis of Boral from the Zion Nuclear Power Plant Spent Fuel Pool, SRNL-TR-2018-00244, Revision 0, March 2019. ADAMS Accession No. ML19155A215.

A20. H. Akkurt, Demonstration of i-LAMP via Case Studies and Proposed Implementation Path, Trans. Am. Nuc. Soc., 125, 148-151, (2021).

A21. Dry Cask Storage Characterization Project. EPRI, Palo Alto, CA: 2002. 1002882.

NEI 16-03-A, Revision 1 August 2023

53 A22. Cladding Considerations for the Transportation and Storage of Spent Fuel, ISG-11, Revision 3, Nuclear Regulatory Commission, 2003.

A23. Extended Storage Collaboration Program (ESCP): Progress Report and Review of Gap Analyses. EPRI, Palo Alto, CA: 2011. 1022914.

A24. High Burnup Dry Storage Research Project Cask Loading and Initial Results. EPRI, Palo Alto, CA: 2019. 3002015076.

A25. High-Burnup Used Fuel Dry Storage System Thermal Modeling Benchmark: Round Robin Results. EPRI, Palo Alto, CA: 2020. 3002013124.

A26. International Thermal Modeling Benchmark Description for a High-Burnup Used Fuel Dry Storage System: An Extended Storage Collaboration Program Activity.

EPRI, Palo Alto, CA: 2020. 3002018498.

A27. License for Independent Storage of Spent Nuclear Fuel and High-Level Radioactive Waste. Nuclear Regulatory Commission, 2014. ADAMS Accession No. ML15086A582.

A28. Format, Content and Implementation Guidance for Dry Cask Storage Operations-Based Aging Management. Nuclear Energy Institute, NEI 14-03 Revision 2, December 2016. ADAMS Accession No. ML16356A210.

A29. Standard Review Plan for Renewal of Specific Licenses and Certificates of Compliance for Dry Storage of Spent Nuclear Fuel - Revision 1. NUREG-1927, June 2016. ADAMS Accession No. ML16179A148.

A30. Regulatory Guide 3.76, Implementation of Aging management Requirements for Spent Fuel Storage Systems. Nuclear Regulatory Commission, July 2021. ADAMS Accession No. ML21098A022.

A31. Materials Reliability Program: Reactor Pressure Vessel Integrity Primer (MRP-278, Revision 1): A Primer on Theory and Applications. EPRI, Palo Alto, CA: 2017.

3002007951.

A32. BWRVIP-233, Rev. 2: Updated Evaluation of Stress Corrosion Crack Growth in Low Alloy Steel Vessel Materials in the BWR Environment. EPRI, Palo Alto, CA: 2018.

3002013026.

A33. 50.61 Fracture toughness requirements for protection against pressurized thermal shock events (https://www.nrc.gov/reading-rm/doc-collections/cfr/part050/part050-0061.html).

A34. Calvert Cliffs Nuclear Power Plant Unit Nos. 1 & 2; Docket Nos. 50-317 & 50-318 Revision to Reactor Vessel Surveillance Capsule Withdrawal Schedule, ADAMS Accession No. ML003728345.

A35. Beaver Valley Unit 1 Heatup and Cooldown Limit Curves for Normal Operation, WCAP-18102-NP Revision 1, 2018. ADAMS Accession No. ML18099A125.

ROD MCCULLUM Sr. Director, Decommissioning and Used Fuel 1201 F Street, NW, Suite 1100 Washington, DC 20004 P: 202.739.8082 rxm@nei.org nei.org October 12, 2022 Mr. Joseph E. Donoghue Director, Division of Reactor Safety Systems Office of Nuclear Reactor Regulation U.S. Nuclear Regulatory Commission Washington, DC 20555-0001

Subject:

Supplement to NEIs Request for Review and Endorsement of NEI 16-03, Guidance for Monitoring of Fixed Neutron Absorbers in Spent Fuel Pools, Revision 1, Dated August 19, 2022 Project Number: 689

Dear Mr. Donoghue:

The Nuclear Energy Institute (NEI)0F1, on behalf of its members, has identified a need to supplement its recent request for review and endorsement of NEI 16-03 Revision 1, Guidance for Monitoring of Neutron Absorbers in Spent Fuel Pools. The original submittal was provided in my letter to you dated August 19, 2022

[ML22231B042]. This submittal was supported by the Electric Power Research Institutes Industrywide Learning Aging Management Program (i-LAMP): Global Neutron Absorber Material Monitoring Program for Spent Fuel Pools [attached to ML22231B042 as Reference 4].

This letter seeks to clarify the subject request for review and endorsement as follows:

The i-LAMP report describes a framework potentially applicable to numerous neutron absorber materials, with an initial focus on BORAL, in particular for pools that do not have coupons.

i-LAMP does not intend to replace the coupon monitoring program for SFPs with coupons.

i-LAMP can only be used as a surrogate to meet regulatory requirements at plants using BORAL that do not have coupons. Other plants are still expected to have installed coupons and continue testing.

For newer materials (for example, Metamic and Boralcan), i-LAMP enables industrywide data collection (coupon results and SFP water chemistry), analysis, and trending. In the event 1 The Nuclear Energy Institute (NEI) is responsible for establishing unified policy on behalf of its members relating to matters affecting the nuclear energy industry, including the regulatory aspects of generic operational and technical issues. NEIs members include entities licensed to operate commercial nuclear power plants in the United States, nuclear plant designers, major architect and engineering firms, fuel cycle facilities, nuclear materials licensees, and other organizations involved in the nuclear energy industry.

Joseph E. Donoghue October 12, 2022 Page 2 performance issues are identified in the future, it enables proactive testing, cause determination, extent of condition identification, material lifetime estimation, development of mitigation approaches, and timely dissemination of this information for the benefit of i-LAMP participants.

With this clarification, NEI is narrowing its request for NRC review and endorsement to NEI 16-03 itself and only those portions of the supporting EPRI i-LAMP document that pertain to use of surrogate data for spent fuel pools with BORAL neutron absorbers that do not have coupons. Use of i-LAMP for pools with other types of neutron absorbers is for industry experience sharing purposes only and may not be used as an alternative to meet NRC requirements with respect to coupons in those pools.

Sincerely, Rod McCullum c:

Mr. Steven Bloom, NRC/NRR Mr. Matthew Yoder, NRC/NRR Ms. Leslie Fields, NRC/NRR Ms. Lois James, NRC/NRR

ROD MCCULLUM Sr. Director, Decommissioning and Used Fuel 1201 F Street, NW, Suite 1100 Washington, DC 20004 P: 202.739.8082 rxm@nei.org nei.org December 15, 2022 Mr. Joseph E. Donoghue Director, Division of Reactor Safety Systems Office of Nuclear Reactor Regulation U.S. Nuclear Regulatory Commission Washington, DC 20555-0001

Subject:

Response to NRC Request for Supplemental Information Supporting the Acceptance review of NEI 16-03, Rev. 1, Guidance for Monitoring of Fixed Neutron Absorbers in Spent Fuel Pools (EPID L-2022-NTR-0002)

Project Number: 689

Dear Mr. Donoghue:

By letter dated December 2, 2022 [ML22301A179], the NRC concluded that NEIs August 19, 2022 request for NRC review and endorsement of NEI 16-03, Revision 1, as supplemented by NEI letter dated October 12, 2022, did not provide technical information in sufficient detail to enable the staff to complete its detailed review and make an independent assessment regarding the acceptability of the proposed topical report in terms of regulatory requirements for the protection of public health and safety and the environment.

The NRC described six areas where additional information was needed for NRC to initiate its acceptance review. The purpose of this letter is to provide NRC with the requested information, which is summarized below. NEI 16-03, Revision 1, has been augmented to include these additional details and is included for your review as an attachment to this letter.

NRC Comment 1:

As described in LIC-109, A licensees use of unapproved codes or TRs (or the use of codes and TRs outside the limitations imposed by the NRC staff) may be acceptable if the licensee has provided a full analysis to justify that the proposed use satisfies NRC regulations and is appropriately conservative. However, simply referencing an unapproved TR or code is not acceptable. Electric Power Research Institute (EPRI) Report 3002018497, Industrywide Learning Aging Management Program (i-LAMP): Global Neutron Absorber

Joseph E. Donoghue December 15, 2022 Page 2 Material Monitoring Program for Spent Fuel Pools, is an unapproved TR that, until the submittal of NEI 16-03, Revision 1, the staff has not seen. While its inclusion as a reference is not an immediate cause for non-acceptance, the lack of a full analysis to justify that the proposed use satisfies NRC regulations and is appropriately conservative cannot be verified.

NEI Response:

In response to this comment, relevant portions of the EPRI i-LAMP report are reproduced in NEI 16-03, Revision 1, with EPRIs permission, specifically in Section 2.2 and Appendix A.

NEI trusts that with the inclusion of the desired detailed technical information directly into NEI 16-03, Revision 1, the NRC concern is adequately addressed.

NRC Comment 2:

The changes made in NEI 16-03, Revision 1, provide a high-level background on the i-LAMP program, but provide no programmatic details and no guidance on how licensees would use the program to manage neutron absorbers at their facility.

NEI Response:

A discussion on programmatic details and how licensees would use the program to manage neutron absorbers at their facility is now included in the Foreword, Section 1.2, Section 2.2, and Appendix A.

NRC Comment 3:

NEI 16-03, Revision 1, does not provide guidance on implementation of i-LAMP. Instead, it says that the i-LAMP report describes different implementation options. These are the details that should be included in the NEI guidance document.

NEI Response:

Discussion of the proposed implementation of i-LAMP is now included in the following sections of NEI 16-03 Rev. 1:

Section 2 describes i-LAMP, including the concepts of sibling pool relationship, degradation trending, and binning to reduce implementation complexity.

Section 2.2.3 describes a two-bin initial implementation approach, with additional binning or use of surrogate/sibling relationships (Section 2.2.2) if needed in the future.

Section A.4 re-iterates the two-bin approach with supporting technical data.

The Foreword and Background (Section 1.2) confirm that i-LAMP implementation is only for BORAL and is not intended to replace an existing coupon monitoring program.

Joseph E. Donoghue December 15, 2022 Page 3 NRC Comment 4:

NEI 16-03, Revision 1 contains no description of parameters that licensees are expected to follow if they choose to use i-LAMP (e.g., verification of bounding data for a specific plant, periodicity of formal i-LAMP data review to ensure the plant is bounded or new operating experience is available).

NEI Response:

The following sections are added to NEI 16-03 Revision 1:

Section 2.2.2 describes sibling pool criteria and parameters.

Section 2.2.4 describes periodicity of review of i-LAMP data and verification of bounding data.

Section A.3 describes two case studies. Case 1 (Section A.3.1) demonstrates how a plant that was not originally bounding can become bounding and can be used to improve the health of the i-LAMP program in the long term. Case 2 (Section A.3.2) shows how a surrogate approach will be used (development of sibling criteria, parameters for establishment of similarity). These are examples on how the surrogate/sibling approach will be used, when/if needed.

NRC Comment 5:

Programs that were approved by the NRC as part of NEI 16-03, Revision 0, include coupon testing, and in-situ measurement. For both programs the Revision 0 guidance provided program elements, sampling intervals, acceptance criteria, and guidance on evaluation of results. None of these programmatic details are provided for the newly proposed i-LAMP program. NEI 16-03, Revision 1, should contain the same level of detail for i-LAMP as the previously approved Revision 0 contained for coupon testing and in-situ measurement.

NEI Response:

Section 2.2.4 describes the acceptance criteria for i-LAMP.

NRC Comment 6:

I-LAMP is only applicable to Boral in the current EPRI document. However, NEI 16-03, Revision 1, does not say that it should only be used for Boral. Although it says that the i-LAMP document has an initial focus on Boral, it does not rule out i-LAMP use for other neutron absorber materials. The NRC staff notes that the supplemental letter dated October 12, 2022, provides some clarification regarding the current programs focus on Boral plants without coupons. However, the same letter goes on to describe i-LAMPs applicability to newer materials. Given the current state of the i-LAMP program (only Boral data has been reported), the staff does not agree with the notion that i-LAMP should be treated as a non-material specific alternative monitoring approach as described in the NEI 16-03, Revision 1, under Forward section.

NEI Response:

It is true that at this phase, i-LAMP is only applicable to Boral, given data collection and analysis is done for Boral plants. This has been clarified further in the Foreword, Section 1.2, and Section 2.2.

Joseph E. Donoghue December 15, 2022 Page 4 The industry appreciates this opportunity to present additional technical detail in support of your review and looks forward to a continuing dialog on this matter. The approach proposed in NEI 16-03, Rev. 1 and EPRI i-LAMP will be vital to licensee programs that provide protection of public health and safety and the environment during the storage of spent fuel in racks containing Boral fixed neutron absorbers.

Sincerely, Rod McCullum Attachment c:

Mr. Steven Bloom, NRC/NRR Mr. Matthew Yoder, NRC/NRR Ms. Leslie Fields, NRC/NRR Ms. Lois James, NRC/NRR Mr. Siva Lingam, NRC/NRR

ROD MCCULLUM Sr. Director, Decommissioning and Used Fuel 1201 F Street, NW, Suite 1100 Washington, DC 20004 P: 202.739.8082 rxm@nei.org nei.org May 23, 2023 Ms. Lois M. James Office of Nuclear Reactor Regulation U.S. Nuclear Regulatory Commission Washington, DC 20555-0001

Subject:

Response to NRC Request for Additional Information Supporting the Review of NEI 16-03, Rev. 1, Guidance for Monitoring of Fixed Neutron Absorbers in Spent Fuel Pools (EPID L-2022-NTR-0002)

Project Number: 689

Dear Ms. James:

By letter dated August 19, 2022, as supplemented by letters dated October 12 and December 15, 2022 (ADAMS Accession Nos. ML22231B041, ML22298A281, and ML22349A656, respectively), the Nuclear Energy Institute (NEI)1 submitted NEI 16-03, Guidance for Monitoring of Fixed Neutron Absorbers in Spent Fuel Pools, Revision 1, for U.S. Nuclear Regulatory Commission (NRC) staff for review and endorsement. The staff reviewed and accepted the guidance for review on January 11, 2023 (ADAMS Accession No. ML23005A144).

Subsequently, via your e-mail dated April 24, 2023, nine requests for additional information (RAIs) identified during NRC staffs review were transmitted to NEI.

This letter transmits industrys response to these RAIs in the attached document. This response has been coordinated with industry through EPRIs Neutron Absorber Users Group.

1 The Nuclear Energy Institute (NEI) is the organization responsible for establishing unified industry policy on matters affecting the nuclear energy industry, including the regulatory aspects of generic operational and technical issues. NEI's members include entities licensed to operate commercial nuclear power plants in the United States, nuclear plant designers, major architect/engineering firms, fuel cycle facilities, nuclear materials licensees, and other organizations and entities involved in the nuclear energy industry.

Lois M. James May 23, 2023 Page 2 Please let me know if you have any questions.

Sincerely, Rod McCullum Attachment c:

Mr. Steven Bloom, NRC/NRR Mr. Matthew Yoder, NRC/NRR Ms. Leslie Fields, NRC/NRR NRC Document Control Desk

RAI #1 Issue/Request:

Section 1.2, Background, on page 1 states that, In some cases, sufficient operating experience was acquired over several decades to allow individual licensees not to need coupons or in-situ examinations, but to rely on the collective industry experience. The staff is unaware of any licensees that have cited collective industry experience in lieu of in-situ or coupon testing for any neutron absorbing material. In addition, this is not consistent with the guidance in NUREG-1801, Revision 2. Please provide the plants and associated NAMs that are relying on collective industry experience instead of in-situ examinations/coupons or modify the background language. The staff recognizes that this statement was also included in Revision 0 of NEI 16-03 (ADAMS Accession No. ML16265A248).

NEI Response:

As indicated in the RAI, this statement was included in NEI 16-03, Revision 0 and left unchanged as part of the Background information. This was the practice in the past, as plants were following industry experience, via EPRIs Neutron Absorber User Group (NAUG), in combination with water chemistry monitoring.

However, based on the RAI, this statement will be removed from revised NEI 16-03, Revision 1.

RAI #2 Issue/Request:

The foreword and background state that i-LAMP is intended to replace a water chemistry monitoring approach from Revision 0 that was not accepted by the NRC to be considered as a stand-alone monitoring approach. It is unclear to the NRC staff what the purpose of this statement is. If the intention of this revision is to make i-LAMP an acceptable stand-alone monitoring approach, why would the current revision reference an approach that was previously rejected and does not appear in the approved Revision 0?

NEI Response:

This statement was included in NEI 16-03 Revision 1 to provide background information and clearly state the differences between NEI 16-03 Revision 0 and Revision 1.

However, based on the RAI, this statement will be removed from the foreword and background sections of the revised NEI 16-03 Revision 1.

RAI #3 Issue/Request:

The last paragraph of the Background section discusses options for licensees to modify their current licensing basis with respect to neutron absorbing material surveillance programs. This paragraph seems insufficient to address the wide variety of individual plant licensing scenarios.

The previously approved revision of this guidance focused on the material surveillance program and did not address plant-specific licensing scenarios. Please clarify that the Revision 1 guidance is not intended to address individual licensing scenarios.

NEI Response:

The Revision 1 guidance is not intended to address individual licensing scenarios. The intent of the portion of the Revision 1 guidance alluded to in the RAI is to recognize the various individual licensing scenarios at plants around the country. These scenarios fall under several categories depending on how the commitment to NAM monitoring is captured in the licensing basis (e.g.,

technical specification, FSAR, licensing commitment, etc.). This guidance paragraph recognizes that each facility adopting the endorsed guidance will need to implement it in accordance with their plant-specific processes. This will likely involve review under the plant commitment control process and/or 10 CFR 50.59. Either of these processes could result in the need for a license amendment request. Each licensee will need to make its own evaluation in this regard under its site-specific change control program.

Based on the above response, no change is proposed to revise this statement in NEI 16-03.

RAI #4 Issue/Request:

Section 2.2.3 states that the 2-bin approach will eliminate regulatory submissions and the need for plant-specific review by the regulator. It is unclear to the NRC staff how the proposed binning approach would absolve a plant from the regulatory process and licensing requirements. Any licensee seeking to adopt an i-LAMP monitoring approach would need to modify their current monitoring program and associated licensing commitments. Please discuss why the proposed binning method would eliminate regulatory submissions and plant-specific reviews by the NRC?

NEI Response:

The intent of the statement is to emphasize the simplicity of the two-bin approach both for the licensee and the regulator.

Proposing to revise NEI 16-03 Revision 1 for this sentence to read:

The two-bin approach will simplify implementation as it would not require identification of siblings for every licensee without coupons unless future NAM monitoring data indicates there is a need for identification of specific siblings or further binning refinement in the future.

RAI #5 Issue/Request:

Section 2.2.3 states that the 2-bin approach is applicable until loss of 10B is identified by global operating experience. However, this does not account for the potential scenario where a plant or plants with the oldest Boral runs out of coupons or ceases operation without transferring their remaining coupons to another operating plant. In this scenario there will be a subset of plants that relied on the data from the plant with the oldest Boral that will no longer be bounded by the collective data set. If a plant is not monitoring a specific sibling plants data but relies on the generic i-LAMP program, as a whole, they may be unaware that they are no longer bounded by the program. How does NEI propose to account for this scenario?

NEI Response:

This RAI is answered in multiple parts to address each question/scenario.

1. Unlike previous practice, when it is possible, it is now recommended to return the coupons to their pools after the analysis. The primary objective of this approach was to make sure plants do not run out of coupons during their operating time.

2. When a plant with coupons ceases operation, when possible, their coupons will be transferred to a sibling pool after all spent fuel is removed from the pool. This will be coordinated via the NAUG.

3. EPRI will be performing continuous data collection and analysis. If a loss of 10B is identified and considered significant enough to impact the assumptions in the criticality analysis, further binning will be performed and communicated to the industry via the NAUG.

Once i-LAMP is endorsed, coupons from the oldest Boral material in service will reside in two pools. It is recommended to re-insert coupons, when possible, after periodic removal and evaluation. These actions reduce the likelihood of not having Boral age coverage. Section 2.2.1.3 addresses another possible response: If a particular characteristic is unbounded, i-LAMP data may still be applicable for surrogate coupon monitoring provided analysis shows that there is no degradation trend related to that characteristic.

Finally, in Section 2.2.4:

Periodic review of i-LAMP data performed at 5-year intervals maintains this consistency with the coupon testing program interval (performed at 5-year or 10 -year intervals, as discussed in Section 2.1). Results are acceptable if:

The sibling pool Boral material is represented in the i-LAMP database. Representation is determined using the characteristics described in Section 2.2.2 and Appendix A, including material age, areal density, and SFP water chemistry.

Applicable surrogate data has been updated with new operating experience within the last 10 years, unless older data remains bounding for the sibling pool.

Section 2.2.4 processes ensure that if the proposed situation does occur, it will be identified within the normal surveillance interval time frame and dealt with using the plant corrective action process.

Based on the above response, no change is proposed to revise this statement in NEI 16-03.

RAI #6 Issue/Request:

There is a potential scenario where a Boral degradation mechanism that results in loss of 10B is identified in the future. If this occurs all plants relying on i-LAMP for their neutron absorber monitoring programs face regulatory uncertainty. Plants relying on a generic 2-bin approach would not have the plant-specific analysis available to rule out the degradation mechanism for their site based on material age or other applicable parameters. How would i-LAMP participating plants demonstrate their material condition and continued criticality safety without plant-specific

analysis or the analysis of a sibling plant with closely related material and spent fuel pool conditions? Specifically, how does the degradation feedback loop from other boral plants work or apply.

NEI Response:

Based on historical trends over decades of operation and observation, a new or different Boral degradation mechanism is unlikely to be discovered. However, should such a scenario unfold, that information would be both addressed at the plant of discovery in the corrective action program and shared with the industry via the NAUG. Since i-LAMP is proposed as a learning aging management program, when this scenario happens, i-LAMP will move to the next level of binning (finer binning as needed). Each plant receiving this information would evaluate it within its operating experience program and/or corrective action program.

Additionally, if i-LAMP is no longer applicable, the issue will be addressed under the corrective action program, including possible use of other NEI 16-03 options - develop a coupon monitoring program, or alternatively use in-situ monitoring.

NEI proposes to make a clarification to the guidance by adding the paragraph below to the end of NEI 16-03, Section 2.2.3:

Should a new or different degradation mechanism that causes a loss of 10B in the NAM be discovered, that information would be entered into that sites corrective action program and shared with the industry via the NAUG. Each plant receiving this information would evaluate it within its operating experience program and/or corrective action program as circumstances dictate.

RAI #7 Issue/Request:

Temperature and cumulative dose (gamma and neutron) are listed in Section 2.2.1 as parameters affecting neutron absorber aging. Why are these parameters not included in the list of sibling pool criteria discussed in Section 2.2.2?

NEI Response:

Section 2.2.1 of NEI 16-03 describes general parameters that affect aging mechanisms.

Temperature and cumulative dose are parameters of interest more applicable for NAM materials other than Boral (i.e., Boraflex, Carborundum), which are not part of i-LAMP. The evaluations of axial 10B areal density distribution from the Boral NAM panels removed from Zion and an operating plant with over 40 years of service time (see NEI 16-03, Section A.2) confirm that dependence on temperature and cumulative dose for Boral is negligible. If the radiation and temperature were factors in degradation, it would have been evident in the areal density values, provided in Figures A.14 and A. 15, as a function of axial height given temperature and radiation dose profiles vary significantly as a function of axial height for a given panel.

Additionally, coupon data comes from operating pools with coupons, in which NAM age and NAM cumulative dose are correlated. Coupons are placed in lead locations, with highest exposures; no trending is observed to date and i-LAMP will continue to analyze and trend the data.

Based on the above response, no change is proposed to revise this statement in NEI 16-03.

RAI #8 Issue/Request:

Appendix A Section A.3.1.4 proposes actions that the pilot plant may make pending regulatory approval. The NRC staff does not intend to perform any regulatory assessment of plant-specific neutron absorber programs as part of its review of NEI 16-03, Rev. 1. Please clarify the intent of this section of Appendix A.

NEI Response:

This section was retained to provide background information regarding the i-LAMP program planned actions intended to maintain the broadest possible coupon coverage for the industry.

The actions listed in this section were referring to pending regulatory approval of i-LAMP as part of NEI 16-03 Revision 1. They were not referring to regulatory assessment of a plant-specific neutron absorber program.

This sentence will be revised in NEI 16-03 Revision 1 as following (by adding bolded i-LAMP is to avoid misunderstanding for plant specific review/approval):

If i-LAMP is approved by the regulator as a replacement for Pilot-1s current commitments, instead of simply proposing to use Sibling-1 as surrogate for Pilot-1, proposing the following:

RAI #9 Issue/Request:

Section 2.2.1.1 states that water chemistry is used as a monitoring tool for early indications of anomalies. In the case of Boraflex, water chemistry programs identified excess silica in the spent fuel pool water. For Boral, the primary material composition is aluminum (Al). However, Appendix A Section A1.2 states that very few pools also measure Al and the majority of utilities discontinued this practice. For pools that do not have their own Boral coupons, plant specific data such as dissolved Al is essential for ensuring the integrity of the Boral. This is exemplified by the other industry programs (reactor vessel integrity and steam generator integrity) that are cited in NEI 16-03 as examples of industrywide monitoring programs that rely on water chemistry measurements. How can water chemistry readings identify early signs of Boral degradation if pools are not testing for the primary element comprising the Boral material (Al)?

NEI Response:

As discussed in the document, plants have been following EPRI water chemistry guidelines to minimize corrosion. As indicated, these water chemistry guidelines are used by other programs as well. EPRI water chemistry guidelines have mandatory and recommended measurements. However, the current EPRI water chemistry guidelines do not require measuring Al levels - they are more focused on measurement of Cl, F, Sulfate as they are known corrosion accelerants as well as B level (PWR), and pH and conductivity.

Because no correlation between dissolved Al and Boral effectiveness has been developed to date, industry does not view Al monitoring as essential for this purpose. Measured coupon data provides more direct confirmation of Boral performance. Monitoring water chemistry for other elements or compounds is intended to enable identification of the cause and extent of

condition of any degradation that may be identified in the future. While Al monitoring may be useful it is not currently actionable for confirming the B-10 content of the Boral.

Based on the above response, no change is proposed to revise this statement in NEI 16-03.

v t e Letter Sequence Other
EPID:L-2022-NTR-0002, (Open)
Initiation Request, Request, Request, Request Acceptance, Acceptance, Acceptance, Acceptance Supplement Administration Meeting Questions 24 April 2023 24 April 2023 Answers 23 May 2023 Results Approval Other: ML24054A079
MONTHYEAR2023-12-19 [Table View]

ML24054A079

Text

Subject:

SUBJECT:

Dear Mr. Montgomery,

1.0 INTRODUCTION

3.0 TECHNICAL EVALUATION

5.0 CONCLUSION

6.0 REFERENCES

1.0 INTRODUCTION

3.0 TECHNICAL EVALUATION

5.0 CONCLUSION

6.0 REFERENCES

1.2 BACKGROUND

2.2 I-LAMP

1.2 BACKGROUND

2.2 I-LAMP

Subject:

Dear Mr. Donoghue:

Subject:

Dear Mr. Donoghue:

Subject:

Dear Ms. James:

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