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NEI, NRC Review of NEI 16-03, Revision 2, Guidance for Monitoring of Fixed Neutron Absorbers in Spent Fuel Pools
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Issue date:	08/31/2023
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NEI 16-03, Revision 1 Guidance for Monitoring of Fixed Neutron Absorbers in Spent Fuel Pools August 2023

NEI 16-03, 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, 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, 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

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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

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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

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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, 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.

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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.

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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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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.

NEI 16-03, Revision 1 August 2023

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.

NEI 16-03, Revision 1 August 2023

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.

NEI 16-03, Revision 1 August 2023

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

NEI 16-03, Revision 1 August 2023

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)

NEI 16-03, Revision 1 August 2023

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

NEI 16-03, Revision 1 August 2023

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.

NEI 16-03, Revision 1 August 2023

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

NEI 16-03, Revision 1 August 2023

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:

NEI 16-03, Revision 1 August 2023

44

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:

NEI 16-03, Revision 1 August 2023

45

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.

NEI 16-03, Revision 1 August 2023

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

NEI 16-03, Revision 1 August 2023

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.

NEI 16-03, Revision 1 August 2023

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, 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, 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, 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, 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, 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.

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