OMB Control No.: 3150-0231 

ML16097A169 

UNITED STATES 

NUCLEAR REGULATORY COMMISSION 

OFFICE OF NUCLEAR REACTOR REGULATION 

OFFICE OF NUCLEAR MATERIAL SAFETY AND SAFEGUARDS

WASHINGTON, DC 20555-0001 

April 7, 2016 

NRC GENERIC LETTER 2016-01: MONITORING OF NEUTRON-ABSORBING MATERIALS 

IN SPENT FUEL POOLS 

ADDRESSEES 

All nuclear power reactors with a license issued under Title 10 of the Code of Federal 

Regulations (10 CFR) Part 50, “Domestic Licensing of Production and Utilization Facilities,” 

except those that have permanently ceased operations with all reactor fuel removed from onsite 

spent fuel pool (SFP) storage. 

AND 

All holders of an operating license for a non-power reactor (research reactor, test reactor, or 

critical assembly) under 10 CFR Part 50 who have a reactor pool, fuel storage pool, or other wet 

locations designed for the purpose of fuel storage, except those who have permanently ceased 

operations with all reactor fuel removed from onsite wet storage. 

PURPOSE 

The U.S. Nuclear Regulatory Commission (NRC) is issuing this generic letter (GL) to address 

degradation of neutron-absorbing materials in wet storage systems for reactor fuel at power and 

non-power reactors. The primary focus of this GL is on the credited use of these materials at 

power reactors; however, the NRC staff is aware of the use of neutron-absorbing materials in 

similar applications at some non-power reactors for which the staff needs additional information. 

In the context of this GL, “credited” means that the neutron-absorbing material is necessary to 

limit the maximum effective multiplication factor (keff), under optimum conditions of moderation 

and reflection, to less than that assumed in the licensing and design basis (e.g., criticality safety 

analysis, accident analysis, and technical specifications (TS) limit). 

Specifically, the NRC is issuing this GL for two purposes: 

(1) To request that addressees submit information, or provide references to previously 

docketed information, which demonstrates that credited neutron-absorbing materials in 

the SFP of power reactors and the fuel storage pool, reactor pool, or other wet locations 

designed for the purpose of fuel storage, as applicable, for non-power reactors, are in 

compliance with the licensing and design basis, and with applicable regulatory 

requirements; and that there are measures in place to maintain this compliance. 

(2) To collect the requested information and determine if additional regulatory action is 

required. 
GL 2016-01 

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Under 10 CFR 50.54(f), addressees are required to submit a written response to this GL.

BACKGROUND 

Maintaining subcriticality—i.e., conditions that do not allow self-sustaining fission reactions—is 

an important safety consideration for nuclear fuel storage. The NRC requires power reactor 

license holders to maintain SFP subcriticality in accordance with 10 CFR 50.68, “Criticality 

accident requirements,” General Design Criterion (GDC) 62, “Prevention of Criticality in Fuel 

Storage and Handling,” in Appendix A, “General Design Criteria for Nuclear Power Plants,” to 

10 CFR Part 50, and other equivalent regulatory criteria. The NRC has a similar requirement 

included in the TS for non-power reactors. 

The license holder usually documents the nuclear criticality safety (NCS) analyses in the 

updated final safety analysis report (UFSAR). The NCS analyses form the basis for 

demonstrating compliance with plant TS, compliance with NRC regulations, and adequate 

subcriticality for both normal operating conditions and design-basis events. In many SFP NCS 

analyses, neutron-absorbing materials are credited for maintaining subcriticality in the SFP, with 

assumptions on dimensions and boron-10 (10B) areal density. Hence, these materials must be 

able to perform their safety function during both normal operating conditions and design-basis 

events. 

Unidentified, unmitigated, and unmonitored degradation or deformation of the credited neutronabsorbing materials may reduce the safety margin and potentially challenge the subcriticality 

requirement, especially when these materials are subjected to additional stressors during and 

following design-basis events. Many license holders use integrated defense-in-depth design 

features to account for the neutron-absorbing material’s degradation. For example, some 

pressurized-water reactors have been approved to take credit for the soluble boron in the SFP 

water. 

Neutron-absorbing materials are composed of a neutron-absorbing component, generally 10B as 

boron carbide, in a matrix. Both metal matrix and nonmetal matrix materials have been used. 

Different neutron-absorbing materials used in U.S. nuclear power plants include: 

• boron carbide in a silicone polymer (e.g., Boraflex) 

• boron carbide in a phenol formaldehyde resin matrix (e.g., Carborundum, Tetrabor®) 

• metal matrix composites, such as a cermet of boron carbide and aluminum (e.g., Boral®) 

• a metal matrix of an aluminum and boron carbide (e.g., MetamicTM) 

• borated stainless steel 

In the 1980s, Boraflex was the first neutron-absorbing material to exhibit significant degradation, 

as documented in Information Notice (IN) 1987-43 (Reference 1), IN 1993-70 (Reference 2), 

IN 1995-38 (Reference 3), and GL 1996-04 (Reference 4). The NRC staff documented 

additional concerns regarding monitoring and mitigating degradation of Boraflex in IN 2012-13 

(Reference 5). Several license holders identified instances of degradation or deformation of 

Carborundum and Boral® neutron-absorbing materials in SFPs, such as that documented in 

IN 1983-29 (Reference 6) and IN 2009-26 (Reference 7). 

Surveillance of neutron-absorbing material degradation can involve the use of monitoring 

methods to assess or measure degradation of the material and computer codes to model and 

predict the condition of the materials used in the SFP. For Boraflex, a combination of the 
GL 2016-01 

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RACKLIFE computer code and the Boron Areal Density Gauge for Evaluating Racks (BADGER) 

in-situ measurement tool has been employed to manage degradation. The RACKLIFE 

computer code was developed in the mid-1990s to track and predict the loss of Boraflex and to 

manage the storage patterns of spent fuel in the SFP. The BADGER system was originally 

designed, assembled, and tested in the early to mid-1990s by Northeast Technologies 

Company (now a subsidiary of Curtiss–Wright) as a nondestructive scoping tool to evaluate 

neutron-absorbing materials placed in spent fuel racks. Although BADGER was designed and 

is employed primarily to measure the degradation of Boraflex, it is theoretically applicable to any 

neutron-absorbing material and has been used for Carborundum and Boral®. Other surveillance 

methods include testing of representative coupon samples. These tests may include 

dimensional, neutron attenuation, and weight tests. 

Operating Experience 

In October 2003, the licensee for Seabrook, LLC, reported a condition involving Boral® SFP test 

coupons (Reference 8). The licensee reported that the inspection of test coupons revealed 

bulging or blistering of the aluminum cladding. Boral® test coupons had been placed in the SFP 

as monitoring specimens to assess the performance of similar Boral® neutron-absorbing 

material incorporated in the SFP racks. The licensee measured the 10B areal density in the 

Boral® coupons by neutron-attenuation testing. The licensee reported that the areal density 

results were within specification and that there was no loss of 10B material. Furthermore, the 

licensee stated that the impact of the Boral® blistering on the flux trap racks was determined to 

be small and within the bounds of the NCS analyses. Thus, the Boral® maintained its safety 

function. As a result of this event, the licensee developed a Boral® Monitoring Program and 

added a blistering allowance in the SFP criticality curves to account for the potential bulging or 

blistering of the material in the SFP racks. 

In July 2008, the licensee for Palisades Nuclear Plant (Palisades) identified severe degradation 

of the SFP neutron-absorbing material Carborundum. Palisades performed blackness testing1

to determine if the Carborundum neutron-absorbing material in the racks remained capable of 

performing its safety function. The testing revealed that several Carborundum panels were so 

severely degraded that only approximately one-third of its original 10B remained. As a result, the 

licensee was unable to demonstrate that the SFP satisfied the subcriticality requirements in 

accordance with NRC regulations and plant TS (Reference 7). Because the licensee had not 

performed routine surveillance of the neutron-absorbing capacity of the material, the time of 

degradation onset and the degradation rate were unknown. The issue was resolved when the 

NRC approved a license amendment that removed credit for the Carborundum material as a 

neutron absorber in the SFP and restricted the pattern of the fuel assemblies in the pool. 

In January 2009, the licensee for Beaver Valley Power Station, Units 1 and 2 submitted 

supplemental information identifying Boral® degradation in the SFP during review of its license 

renewal application (Reference 9). The licensee stated that inspections conducted in 2007 of 

the Boral® neutron-absorbing material coupons identified numerous blisters of the aluminum 

cladding, while only a few small blisters were identified in 2002. This degradation posed a 

potential safety concern because blisters may displace water from the flux trap between the 

deformed cladding and the boron-containing core in certain fuel storage racks that challenge the 

dimensional assumptions used in the NCS analyses. Based on these inspections, the licensee 

determined that the Boral® aluminum cladding blistering was an aging effect requiring 

 

1 This is an in-situ testing technique with a neutron source and detector that measures the presence of 

neutron-absorbing material.
GL 2016-01 

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management. The licensee proposed to credit the existing Boral® Surveillance Program for 

managing this aging effect in its license renewal application. As a result, the licensee has 

enhanced its monitoring programs to confirm that safety margins are maintained in the SFP. 

In September 2009, the licensee for Turkey Point Nuclear Generating Station, Unit 3 informed 

the NRC that Unit 3 would be unable to fully implement license amendment No. 234 because of 

procurement challenges with MetamicTM neutron-absorbing material inserts. In this amendment, 

the NRC approved the replacement of Boraflex with a combination of rod cluster control 

assemblies, MetamicTM rack inserts, and administrative controls that required mixing storage of 

higher reactivity fuel with lower reactivity fuel. As a result of the procurement challenges with 

MetamicTM rack inserts and the continued Boraflex degradation, the NRC issued three violations, 

including a civil penalty (Reference 10). The licensee implemented compensatory measures, 

including increasing soluble boron concentration levels, to ensure that the SFP remained 

subcritical, as the NRC acknowledged in a confirmatory action letter (Reference 11). To provide 

a long-term solution for this issue, the licensee requested and the NRC approved a license 

amendment that included new spent fuel storage patterns and updated licensing-basis 

information demonstrating compliance with criticality requirements. 

To address Boraflex degradation in 2010, the licensee for Peach Bottom Atomic Power Station, 

Units 2 and 3 performed an operability determination (OD) based on the RACKLIFE surveillance 

program that concluded it would maintain sufficient margin to criticality in its SFP until 2014. 

However, the NRC’s review of the OD concluded that the licensee did not accurately project the 

rate of Boraflex degradation and used several nonconservative assumptions in the analysis. 

The licensee performed a re-analysis and determined that several Boraflex panels had 

degraded below TS requirements. As a result, the licensee declared multiple cells in the SFP 

inoperable, relocated spent fuel assemblies to maintain appropriate margin, and established 

additional administrative controls to govern use of affected cells. The NRC issued a violation 

associated with the licensee’s failure to implement corrective actions to prevent the Boraflex 

panels from degrading below the TS requirements (Reference 12). To provide a long-term 

solution for this issue, the licensee requested and the NRC approved a license amendment that 

included installation of rack inserts and removal of credit for Boraflex as a neutron-absorbing 

material. 

NRC Actions 

The operating experience coupled with regulatory actions (e.g., plant site inspections and 

reviews of license renewal applications and license amendments) indicated a gap in the NRC 

regulatory knowledge base of neutron-absorbing materials. In addition, the NRC determined 

that existing regulatory guidance did not adequately address the management of the effects of 

aging on the neutron-absorbing materials. Subsequently, the NRC developed license renewal 

interim staff guidance (Reference 13) for an aging management program for neutron-absorbing 

materials. This regulatory guidance on aging management of neutron-absorbing materials was 

incorporated into NUREG-1801, Revision 2, “Generic Aging Lessons Learned (GALL) Report,” 

(Reference 14). 

The NRC also prepared two technical letter reports (TLRs) (References 15 and 16) discussing 

some of the methods that license holders use to monitor the degradation of neutron-absorbing 

materials. The NRC commissioned these reports to gather more information on surveillance 

methodologies for neutron-absorbing materials employed in SFPs. These TLRs also identify 

uncertainties in the methodologies employed to monitor the performance of neutron-absorbing 

materials. The reports provide a generic overview on the use of the RACKLIFE computational 
GL 2016-01 

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tool and the BADGER in-situ measurement technique. The reports discuss the reliability of 

these methodologies for certain applications. Some license holders use these surveillance tools 

to demonstrate compliance with their TS and NRC regulations. 

Additionally, the NRC recently published a third TLR that summarizes the characteristics of the 

phenolic-resin-type neutron-absorbing materials, Carborundum and Tetrabor®, the qualification 

testing results, and the operating experience pertaining to degradation (Reference 17). The 

report also describes phenolic resin degradation mechanisms and analyzes current surveillance 

methods. 

DISCUSSION 

Reactivity and, therefore, criticality is determined by local phenomena, including how far a 

neutron is expected to travel in the given environment. In the SFP environment, the minimum 

critical volume necessary to sustain a nuclear chain reaction may be as small as four fuel 

assemblies; certainly much smaller than the entire SFP. The conditions within the minimum 

critical volume will determine whether or not an inadvertent criticality event can occur and if the 

subcriticality requirements are met. The use of SFP-wide parameters, such as average 

neutron-absorbing material areal density or degradation, may not be appropriate to verify 

subcriticality requirements that are dependent on local properties. 

To ensure that the requirements of 10 CFR 50.68 and GDC 62 (or equivalent) are met, the 

appropriate parameters on a local level must be known and appropriately considered. For 

license holders who credit neutron-absorbing material in their NCS analyses, this requires that 

the present condition of the neutron-absorbing material be known and that its future condition be 

managed. Two of the aforementioned TLRs issued by the NRC identify uncertainties with tools 

commonly used in the industry to monitor the condition of the neutron-absorbing materials used 

in SFPs. As described in the Operating Experience section, some license holders have had 

difficulty managing their neutron-absorbing materials’ current condition, and in some cases, 

corrective action had to be taken to restore compliance with regulatory requirements. 

SFP neutron-absorbing materials that are credited for maintaining subcriticality must be able to 

perform their safety function during both normal operating conditions and design-basis events. 

Monitoring neutron-absorbing materials is intended to identify when degradation may affect their 

ability to perform their safety function, so that appropriate corrective action can be taken. 

Therefore, the NRC is requesting information to confirm that addressees are in compliance with 

the regulations and to determine whether additional regulatory action is necessary. 

For new reactors licensed under 10 CFR Part 52, the NRC was previously aware of the 

concerns discussed in this GL and considered them in the licensing review. The NRC obtained 

sufficient information to confirm regulatory compliance of the planned design, and imposed a 

license condition that requires 10 CFR Part 52 licensees to provide the necessary information 

on the surveillance or monitoring programs before operation. As for the additional information 

on the operation of the SFP being requested by this GL, this information would not apply to 

Part 52 licensees at this time because no 10 CFR Part 52 licensees currently have an SFP in 

operation and will not for several years. Consequently, 10 CFR Part 52 licensees are not being 

included among the addressees for this GL. 

 
GL 2016-01 

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APPLICABLE REGULATORY REQUIREMENTS 

This section presents multiple regulatory requirements that relate to the subject of this GL and 

have been referenced in licensing and enforcement documents related to neutron-absorbing 

materials. While not all requirements might apply to a specific licensee, request, or condition, 

they are presented here for context. 

The following regulatory requirements related to this GL are applicable to all reactor licensees: 

• 10 CFR 70.24, “Criticality accident requirements,” which requires license holders who 

possess nuclear material to monitor the areas where the material is stored to detect 

accidental criticality. 

• 10 CFR 50.36, “Technical specifications,” which requires licensees to develop 

administrative controls necessary to ensure safe operation. 

• 10 CFR Part 50, Appendix B, “Quality Assurance Criteria for Nuclear Power Plants and 

Fuel Reprocessing Plants,” Criterion XI, “Test Control,” and Criterion XII, “Control of 

Measuring and Test Equipment,” which establish requirements for planned and 

systematic actions necessary to provide adequate confidence that a structure, system, 

or component used to prevent or mitigate the consequences of postulated accidents will 

perform satisfactorily in service. In particular, Criteria XI and XII establish requirements 

for the testing and control of measuring or testing equipment to confirm that all 

structures, systems, or components will perform satisfactorily in service, including 

operational tests conducted during nuclear power plant operation. 

The following additional regulatory requirements related to this GL are applicable to power 

reactor licensees: 

• 10 CFR 50.68, which contains the regulations for maintaining SFP subcriticality. The 

NRC uses this regulation to develop acceptance criteria for monitoring programs for SFP 

neutron-absorbing materials. 

• 10 CFR 50.65, “Requirements for monitoring the effectiveness of maintenance at 

nuclear power plants,” which requires licensees to monitor the performance or condition 

of structures, systems, and components against licensee-established goals, in a manner 

sufficient to provide reasonable assurance that these structures, systems, and 

components are capable of fulfilling their intended functions. 

• Appendix A to 10 CFR Part 50 includes several requirements applicable to criticality 

control in fuel storage. Not all plants were licensed under the GDCs described in 

Appendix A, but they were generally licensed under similar site-specific principal design 

criteria. 

o GDC 2, “Design Bases for Protection Against Natural Phenomena,” which 

requires that structures, systems, and components important to safety be 

designed to withstand the effects of natural phenomena. 

o GDC 61, “Fuel Storage and Handling and Radioactivity Control,” which requires 

that fuel storage and handling, radioactive waste, and other systems that may 
GL 2016-01 

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contain radioactivity be designed to ensure adequate safety under normal and 

postulated accident conditions. These systems shall be designed with a 

capability to permit appropriate periodic inspection and testing of components 

important to safety. 

o GDC 62, which requires that criticality in the fuel storage and handling system be 

prevented by physical systems or processes. 

REQUESTED INFORMATION FROM POWER REACTOR ADDRESSEES 

The NRC requests information in the following five areas for use in verifying compliance: 

(1) a description of the neutron-absorbing material credited in the SFP NCS analysis of 

record (AOR) and its configuration in the SFP; 

(2) a description of the surveillance or monitoring program used to confirm that the credited 

neutron-absorbing material is performing its safety function, including the frequency, 

limitations, and accuracy of the methodologies used; 

(3) a description of the technical basis for determining the interval of surveillance or 

monitoring for the credited neutron-absorbing material; 

(4) a description of how the credited neutron-absorbing material is modeled in the SFP NCS 

AOR and how the monitoring or surveillance program ensures that the actual condition 

of the neutron-absorbing material is bounded by the NCS AOR; and 

(5) a description of the technical basis for concluding that the safety function for the credited 

neutron-absorbing material in the SFP will be maintained during design-basis events. 

The NRC will accept responses based on a categorization, as follows: 

• Category 1: Power reactor addressees that do not credit neutron-absorbing materials 

other than soluble boron in the AOR. In some cases, no neutron-absorbing material is 

present in the spent fuel storage racks, and in other cases, credit for the 

neutron-absorbing material has been removed through a regulatory action 

(e.g., approved license amendment). Those addressees may submit a response letter 

confirming that no neutron-absorbing materials are currently credited to meet NRC 

subcriticality requirements in the SFP. 

• Category 2: Power reactor addressees that have an approved license amendment to 

remove credit for existing neutron-absorbing materials and that intend to complete full 

implementation no later than 24 months after the issuance of this GL. Licensees may 

request extensions to this implementation timeframe if there are extenuating 

circumstances. Those addressees may submit a response letter affirming that they will 

implement the approved license amendment request within the specified time. However, 

they must still provide information equivalent to Category 3 or Category 4 for any other 

neutron-absorbing material credited in the SFP criticality AOR after the license 

amendment has been fully implemented. 

• Category 3: Power reactor addressees that have incorporated their neutron-absorbing 

material monitoring programs into their licensing basis through an NRC-approved TS 
GL 2016-01 

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change or license condition. Those addressees may submit a response letter 

referencing their approved TS change or license condition and affirming that no change 

has been made to their neutron-absorbing material monitoring program, as described in 

the referenced license amendment request. If a change has been made since NRC 

approval of the reference, the response letter should also describe any such changes. 

(Licensees with a monitoring program approved as part of a license amendment request 

or license renewal application that was not incorporated as a TS change or license 

condition are considered to belong in Category 4.) 

• Category 4: All other power reactor addressees. The NRC seeks information in five 

areas depending upon the type of neutron absorber material used by the licensee in the 

SFP. A detailed discussion of the five areas of information can be found in Appendix A. 

Table 1, below, contains the areas of information to be provided by the licensee with 

respect to each type of neutron absorber material. 

Table 1. Areas of Information by Neutron Absorber Material Types 

Areas of Requested Information 

(described in Appendix A of GL-2016-XX) 

Neutron-Absorbing Material 

Type (1) (2) (3) (4) (5) 

Boraflex 

Carborundum 

Tetrabor 

x x x x x 

Boral x x* x 

Borated stainless steel 

Metamic 

Boralcan 

Other metallic matrix 

composites 

x x* 

 * Except for 2(b)(iii). 

Previously-docketed information may be referenced (including license renewal applications and 

license amendment requests) if the addressee affirms that the information remains applicable 

and provides any updated or missing information. In all cases, the NRC is asking licensees to 

provide information available, based on a reasonable search of plant records, docketed 

information, and licensing basis. 

The NRC is not requiring any new analyses, new programs, or new research to be developed or 

implemented in response to this GL. Licensees should maintain the information being 

requested in accordance with provisions found in Appendix B of 10 CFR Part 50 requiring the 

existence of a quality assurance program that appropriately characterizes each component 

(Criterion VII, “Control of Purchased Material, Equipment and Services,” and Criterion VIII, 

“Identification and Control of Materials, Parts, and Components”), that provides for appropriate 

testing to demonstrate satisfactory inservice performance of components (Criterion XI), and that 

ensures that sufficient records will be maintained to furnish evidence of such activities in an 

identifiable and retrievable form (Criterion XVII, “Quality Assurance Records”). 

 
GL 2016-01 

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REQUESTED INFORMATION FROM NON-POWER REACTOR ADDRESSEES 

The NRC requests that each non-power reactor addressee provide the following information for 

use in determining the reliance on neutron-absorbing materials for NCS of reactor fuel or spent 

fuel in storage contained within reactor pools, fuel storage pools, or other wet locations 

designed for the purpose of fuel storage, as applicable: 

(1) Are neutron-absorbing materials used in a reactor pool, fuel storage pool, or other wet 

locations designed for the storage of reactor or spent fuel? 

(2) If neutron-absorbing materials are used, is their use credited in the licensing or design 

basis (i.e., criticality safety analysis) for the storage of reactor fuel or spent fuel in a 

reactor pool, fuel storage pool, or other wet locations, as applicable? 

(3) If neutron-absorbing materials are credited in the facility licensing or design basis for the 

storage of reactor or spent fuel in a reactor pool, fuel storage pool, or other wet 

locations, as applicable, then provide a description of, and technical basis for, any 

surveillance or monitoring programs used to confirm continued acceptable performance 

of the neutron-absorbing materials over time.

REQUIRED RESPONSE 

In accordance with 10 CFR 50.54(f), an addressee must respond as described below: 

Within 210 days of the date of this GL, each addressee is requested to submit a written 

response consistent with the information requested above, and for power reactors, as described 

in Appendix A. 

If an addressee cannot meet the requested response date, the addressee must provide a 

response within 30 days of the date of this GL and describe the alternative course of action that 

it proposes to take in place of providing this information, the basis for the acceptability of the 

proposed alternative course of action, and the estimated completion dates. 

The required written response, signed under oath and affirmation, should be addressed 

“ATTN: Document Control Desk, U.S. Nuclear Regulatory Commission, 

Washington, DC 20555-0001,” in accordance with 10 CFR 50.4, “Written communications.” In 

addition, addressees should submit a copy of the response to the appropriate regional office 

and NRC resident inspector. 

REASON FOR INFORMATION REQUEST

The NRC is authorized under Section 182.a of the Atomic Energy Act of 1954, as amended, and 

10 CFR 50.54(f) to require the addressees of this GL to submit to the NRC the information 

described in “Requested Response.” The NRC staff has determined that the information 

collection and reporting burden to be imposed on nuclear power plant and non-power reactor 

license holders by this GL is justified in view of the potential safety significance issue concerning 

degradation of neutron-absorbing materials in the SFP of nuclear power plants and the reactor 

pool, reactor tank, or fuel storage pool of non-power reactors. Unidentified and unmitigated 

degradation of these materials may challenge the subcriticality margin of the SFP for nuclear 

power plants and the reactor pool, reactor tank, or fuel storage pool for non-power reactors 
GL 2016-01 

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required by the existing regulations. The existing regulatory criteria for subcriticality margin are 

designed to prevent an inadvertent criticality event. If local conditions in the SFP are such that 

criticality is achieved, the local heat generation is likely to increase from power generation 

through fission. Such an event could challenge the ability of the credited SFP structures, 

systems, and components to maintain adequate cooling of the fuel. 

This GL requests information from the addressees so that the NRC can determine if the 

degradation of the neutron-absorbing materials in the SFP for nuclear power plants and the 

reactor pool, reactor tank, or fuel storage pool for non-power reactors is being managed to 

maintain reasonable assurance that the materials are capable of performing their safety 

function, and to verify that the addressees are in compliance with the regulations. The level of 

detail required to perform this determination is not found in documents readily available to the 

NRC, such as the final safety analysis reports. The NRC is not requiring any new analyses or 

new programs to be developed and implemented. Accordingly, the burden on licensees is 

estimated to be no more than 170 hours per unit for all but two power reactors, and no more 

than 20 hours per site for non-power reactors to collect the information from documents 

available to the licensees and submit a final response to the NRC. Two power reactor licensees 

credit more than two neutron-absorbing materials to meet regulatory requirements, so they may 

take up to 250 hours. 

RELATED GENERIC COMMUNICATIONS 

Document 

Number Document Name 

Agencywide 

Documents 

Access and 

Management 

System 

(ADAMS) 

Accession No.

IN 2012-13 Boraflex Degradation Surveillance Programs and 

Corrective Actions in the Spent Fuel Pool 

ML121660156 

IN 2009-26 Degradation of Neutron-Absorbing Materials in the Spent 

Fuel Pool 

ML092440545 

GL 1996-04 Boraflex Degradation in Spent Fuel Pool Storage Racks ML031110008 

IN 1995-38 Degradation of Boraflex Neutron Absorber in Spent Fuel 

Storage Racks 

ML031060277 

IN 1993-70 Degradation of Boraflex Neutron Absorber Coupons ML031070107 

IN 1987-43 Gaps in Neutron-Absorbing Material in High-Density 

Spent Fuel Storage Racks 

ML031130349 

IN 1983-29 Fuel Binding Caused by Fuel Rack Deformation ML14043A291

GL 1978-11 Review and Acceptance of Spent Fuel Storage and 

Handling Application 

ML031280383 

BACKFITTING AND ISSUE FINALITY DISCUSSION 

This GL requests information from holders of 10 CFR Part 50 operating licenses, including 

licensees who have submitted the certification under 10 CFR 50.82(a)(1) that they have 

permanently ceased reactor operations, unless they have removed all fuel from the SFP. This 
GL 2016-01 

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GL is also applicable to non-power reactors, if they have fuel on site in wet storage in a fuel 

storage pool, reactor pool, or reactor tank. The NRC is requesting information to determine if 

neutron-absorbing materials in the SFP of power reactors and the fuel storage pool, reactor 

pool, or reactor tank, as applicable, for non-power reactors are in compliance with the licensing 

and design bases, as well as with applicable regulatory requirements, and if there are measures 

in place to maintain this compliance. 

Based upon this information, the NRC will determine if additional regulatory action is required. If 

the NRC imposes regulatory action on holders of 10 CFR Part 50 operating licenses for nuclear 

power plants with respect to neutron absorbers in SFPs as a result of the NRC’s evaluation of 

the information submitted in response to this GL, then the NRC will address the requirements of 

the Backfit Rule, 10 CFR 50.109, “Backfitting,” no later than the time it imposes the regulatory 

action. 

In addition, the information requested by the NRC in this GL is not required, solely as a result of 

the NRC’s request, to be included or reflected in the UFSAR under 10 CFR 50.71(e). If the 

NRC takes regulatory action to require that the information submitted in response to this GL be 

treated by the licensee as a legally binding requirement for that licensee’s facility, then the NRC 

will address the requirements of the Backfit Rule, no later than the time it requires the licensee 

to treat the submitted information as a legally binding requirement. 

For these reasons, the NRC concludes that the GL does not effectively constitute backfitting for 

holders of 10 CFR Part 50 operating licenses. Therefore, the NRC staff has not performed a 

backfit analysis. 

This GL is not addressed to holders of combined licenses under 10 CFR Part 52, for the 

reasons set forth in the Discussion Section. Therefore, the issuance of this GL is not 

inconsistent with the issue finality provisions applicable to those combined license holders in 

10 CFR 52.98, “Finality of combined licenses; information requests.” 

Holders of licenses for non-power reactors are not subject to the Backfit Rule and are not 

licensed under 10 CFR Part 52. Therefore, this GL may be issued to non-power reactor 

licensees without consideration of backfitting or issue finality under 10 CFR Part 52. 

FEDERAL REGISTER NOTIFICATION 

A notice of opportunity for public comment on this GL was published in the Federal Register

(79 FR 13685) for a 60-day posting period on March 11, 2014. The NRC received 11 sets of 

comments, all from the nuclear industry or vendors associated with the nuclear industry. The 

NRC staff’s evaluation of the comments is publicly available in ADAMS under Accession No. 

ML14181B130. 

A notice of opportunity for public comment regarding the burden on respondents was published 

in the Federal Register (80 FR 31930) on June 4, 2015, as part of the process for obtaining 

clearance from the Office of Management and Budget to issue this GL. The NRC staff’s 

evaluation of the comments related to burden is publicly available in ADAMS under Accession 

No. ML15222A005. 

CONGRESSIONAL REVIEW ACT 

This GL is not a rule as defined in the Congressional Review Act (5 U.S.C. 801–808).
GL 2016-01 

Page 12 of 15 

PAPERWORK REDUCTION ACT STATEMENT 

This GL contains information collection requirements that are subject to the Paperwork 

Reduction Act of 1995 (44 U.S.C. 3501 et seq.). This information collection was approved by 

the Office of Management and Budget, approval number 3150-0231, with an expiration date of 

March 31, 2019. This collection of information is authorized under the provisions 

of Section 182a of the Atomic Energy Act of 1954, as amended, and issued pursuant to 

10 CFR 50.54(f). 

The burden on the public for this information collection is estimated to be no more than 

170 hours per unit for all but two power reactor units licensed under 10 CFR Part 50 and no 

more than 20 hours per response for non-power reactors, including the time for reviewing 

instructions, searching existing data sources, gathering and maintaining the data needed, and 

completing and reviewing the information collection. Two power reactor licensees credit more 

than two neutron-absorbing materials to meet regulatory requirements, so they are expected to 

take up to 250 hours per unit. 

Send comments on this burden estimate or any other aspect of these information collections, 

including suggestions for reducing the burden, to the Freedom of Information Act, Privacy, and 

Information Collection Branch (T5-F53), U.S. Nuclear Regulatory Commission, Washington, 

DC 20555-0001, or to Infocollects.Resource@nrc.gov, and to the Desk Officer, Office of 

Information and Regulatory Affairs, NEOB-10202 (3150-0231), Office of Management and 

Budget, Washington, DC 20503. 

Public Protection Notification 

The NRC may neither conduct nor sponsor, and a person is not required to respond to, an 

information collection request or requirement unless the requesting document displays a 

currently valid Office of Management and Budget control number.

 
GL 2016-01 

Page 13 of 15 

REFERENCES

1. Information Notice 1987-43, “Gaps in Neutron-Absorbing Material in High-Density Spent 

Fuel Storage Racks,” September 8, 1987, ADAMS Accession No. ML031130349. 

2. Information Notice 1993-70, “Degradation of Boraflex Neutron Absorber Coupons,” 

September 10, 1993, ADAMS Accession No. ML031070107. 

3. Information Notice 1995-38, “Degradation of Boraflex Neutron Absorber in Spent Fuel 

Storage Racks,” September 8, 1995, ADAMS Accession No. ML031060277. 

4. Generic Letter 1996-04, “Boraflex Degradation in Spent Fuel Pool Storage Racks,” 

June 26, 1996, ADAMS Accession No. ML031110008. 

5. Information Notice 2012-13, “Boraflex Degradation Surveillance Programs and 

Corrective Actions in the Spent Fuel Pool,” August 10, 2012, ADAMS Accession 

No. ML121660156. 

6. Information Notice 1983-29, “Fuel Binding Caused by Fuel Rack Deformation,” 

May 6, 1983, ADAMS Accession No. ML14043A291. 

7. Information Notice 2009-26, “Degradation of Neutron-Absorbing Materials in the Spent 

Fuel Pool,” October 28, 2009, ADAMS Accession No. ML092440545. 

8. Letter from Florida Power & Light Energy Seabrook, LLC, to NRC, “Boral Spent Fuel 

Pool Test Coupons Report Pursuant to 10 CFR Part 21.21,” October 6, 2003, ADAMS 

Accession No. ML032880525. 

9. Letter from FirstEnergy Nuclear Operating Co, “Supplemental Information for the Review 

of Beaver Valley Power Station, Units 1 and 2, License Renewal Application and License 

Renewal Application Amendment No. 34,” January 19, 2009, ADAMS Accession 

No. ML090220216. 

10. Notice of Violation from NRC to Florida Power & Light Co, “Final Significance 

Determination of White Finding and Notice of Violation; Notice of Violation and Proposed 

Imposition of Civil Penalty – $70,000 (NRC Inspection Report 2010009–Turkey Point),” 

June 21, 2010, ADAMS Accession No. ML101730313. 

11. Confirmatory Action Letter [CAL-2-2010-002], “Turkey Point Unit 3 Commitments to 

Address Degraded Spent Fuel Pool Storage Rack Neutron Absorber,” February 19, 

2010, ADAMS Accession No. ML100539266. 

12. NRC Integrated Inspection Report from NRC to Pacilio, M J, “Peach Bottom Atomic 

Power Station – NRC Integrated Inspection Report 05000277/2012002 and 

05000278/2012002,” May 7, 2012, ADAMS Accession No. ML12129A016. 

13. LR-ISG-2009-01, Final License Renewal Interim Staff Guidance, “Aging Management of 

Spent Fuel Pool Neutron-Absorbing Materials Other than Boraflex,” April 27, 2010, 

ADAMS Accession No. ML100621321. 
GL 2016-01 

Page 14 of 15 

14. NUREG-1801, Revision 2, “Generic Aging Lessons Learned (GALL) Report,” 

December 2010, ADAMS Accession No. ML103490041. 

15. Technical Letter Report, “Boraflex, RACKLIFE and BADGER: Description and 

Uncertainties,” September 30, 2012, ADAMS Accession No. ML12216A307. 

16 Technical Letter Report, “Initial Assessment of Uncertainties Associated with BADGER 

Methodology,” September 30, 2012, ADAMS Accession No. ML12254A064. 

17. Technical Letter Report, “Monitoring Degradation of Phenolic Resin-Based Neutron 

Absorbers in Spent Nuclear Fuel Pools,” June 5, 2013, ADAMS Accession 

No. ML13141A182. 
GL 2016-01 

Page 15 of 15 

CONTACT 

Please direct any questions about this matter to the technical contact or the lead project 

manager listed below or to the appropriate Office of Nuclear Reactor Regulation project 

manager. 

 /RA/ 

John Tappert, Director 

Division of Decommissioning, Uranium Recovery, 

and Waste Programs 

Office of Nuclear Material Safety and Safeguards 

/RA/

Lawrence E. Kokajko, Director 

Division of Policy and Rulemaking 

Office of Nuclear Reactor Regulation 

Technical Contact: Scott Krepel, NRR/DSS 

301-302-0399 

E-mail: Scott.Krepel@nrc.gov

Lead Project Manager: Serita Sanders, NRR/DPR 

301-415-2956 

E-mail: Serita.Sanders@nrc.gov

Note: NRC generic communications may be found on the NRC public website, 

http://www.nrc.gov, under NRC Library/Document Collections. 

Enclosure: 

Appendix A
GL 2016-01 

Page 15 of 15 

CONTACT 

Please direct any questions about this matter to the technical contact or the lead project 

manager listed below or to the appropriate Office of Nuclear Reactor Regulation project 

manager. 

 /RA/

John Tappert, Director 

Division of Decommissioning, Uranium Recovery, 

and Waste Programs 

Office of Nuclear Material Safety and Safeguards 

/RA/

Lawrence E. Kokajko, Director 

Division of Policy and Rulemaking 

Office of Nuclear Reactor Regulation 

Technical Contact: Scott Krepel, NRR/DSS 

301-302-0399 

E-mail: Scott.Krepel@nrc.gov

Lead Project Manager: Serita Sanders, NRR/DPR 

301-415-2956 

E-mail: Serita.Sanders@nrc.gov

Note: NRC generic communications may be found on the NRC public website, 

http://www.nrc.gov, under NRC Library/Document Collections. 

Enclosure: 

Appendix A 

DISTRIBUTION: 

RidsNrrDss Resource RidsNrrDpr Resource RidsNrrDe Resource 

RidsOeMailCenter Resource SKrepel, NRR/DSS/SNPB SSanders, NRR/DPR/PGCB 

SStuchell, NRR/DPR/PGCB RidsOIS Resource NrrDlr Resource 

RidsNmssDuwp Resource RidsNrrDorl Resource RidsOGCMailCenter Resource 

ADAMS Accession No.: ML16097A169 *via e-mail TAC MF0581

OFFICIAL RECORD COPY 

OFFICE NRR/DSS/ 

SRXB 

NRR/DE/ 

ESGB 

NRR/DSS/ 

SRXB Tech Editor NRR/DPR/LA NRR/DLR 

NAME SKrepel MYoder* KWood* JDougherty* ABaxter* 

w/comments AHiser* 

DATE 08/25/15 08/27/15 08/27/15 08/28/15 08/25/15 08/28/15 

OFFICE NMSS/DUWP/ 

RDB/BC 

NRR/DPR/PRLB/

BC 

NRR/DSS/ 

SRXB/BC 

NRR/DE/ 

ESGB/BC NRR/DSS/D NRR/DE/D 

NAME BWatson* AAdams* KWood for 

CJackson* GKulesa* TMcGinty* MRossLee 

for JLubinski*

DATE 8/31/15 8/31/15 8/31/15 9/1/15 9/1/15 9/2/15 

OFFICE NRR/ 

DORL/D NMSS/DUWP/D NRR/ PMDA OIS OE OGC 

NAME ABoland* LCamper* LHill* TDonnell TMarenchin* GMizuno 

DATE 9/2/15 9/1/15 9/8/15 9/14/15 9/8/15 12/14/15 

OFFICE NRR/DPR/PG

CB:LA 

NRR/DPR/ 

PGCB:PM 

NRR/DPR/ 

PGCB:BC 

NRR/DPR/ 

DD NRR/DPR:D 

NRR/DPR:D 

(final 

signature) 

NAME ELee SSanders SStuchell AMoheni LKokajko LKokajko 

DATE 0915/15 09/17/15 09/21/15 12/15 /15 12/18/15 4/7/16 
Enclosure 

Appendix A 

Guidance for Category 4 Responders to Generic Letter 2016-01 

This appendix describes the level of detail for the information requested in Generic Letter (GL) 

2016-01 from Category 4 responders. The list of information herein is provided as guidance on 

responding to this GL. The U.S. Nuclear Regulatory Commission (NRC) recognizes that 

addressees may find that site-specific considerations make it necessary to deviate from this 

guidance, but any such deviations should be justified. Licensees are encouraged to discuss 

any potential deviations with the NRC before making their formal responses. If a specific 

section or item of this appendix is neither applicable nor part of the licensee’s licensing basis, a 

response to that effect is sufficient. If an addressee has additional information relevant to the 

question of regulatory compliance, such items should be included in the GL response letter. 

The information that each power reactor addressee should provide varies, depending on the 

neutron-absorbing materials credited by each licensee and known susceptibility to degradation. 

The table below summarizes the type of information that should be provided for each type of 

neutron-absorbing material. 

 Areas of Requested Information 

Neutron-Absorbing Material 

Type (1) (2) (3) (4) (5) 

Boraflex 

Carborundum 

Tetrabor 

x x x x X 

Boral x x* x 

Borated stainless steel 

Metamic 

Boralcan 

Other metallic matrix 

composites 

x x* 

* Except for 2(b)(iii). 

Areas of Requested Information 

1) Describe the neutron-absorbing material credited in the spent fuel pool (SFP) nuclear 

criticality safety (NCS) analysis of record (AOR) and its configuration in the SFP, including 

the following: 

a) manufacturers, dates of manufacture, and dates of material installation in the SFP; 

b) neutron-absorbing material specifications, such as: 

i) materials of construction, including the certified content of the neutron-absorbing 

component expressed as weight percent; 

ii) minimum certified, minimum as-built, maximum as-built, and nominal as-built areal 

density of the neutron-absorbing component; and 
GL 2016-01 

Appendix A 

Page 2 of 5 

iii) material characteristics, including porosity, density, and dimensions; 

c) qualification testing approach for compatibility with the SFP environment and results 

from the testing; 

d) configuration in the SFP, such as: 

i) method of integrating neutron-absorbing material into racks (e.g., inserts, welded in 

place, spot welded in place, rodlets); and 

ii) sheathing and degree of physical exposure of neutron-absorbing materials to the 

SFP environment; 

e) current condition of the credited neutron-absorbing material in the SFP, such as: 

i) estimated current minimum areal density; 

ii) current credited areal density of the neutron-absorbing material in the NCS AOR; 

and 

iii) recorded degradation and deformations of the neutron-absorbing material in the SFP 

(e.g., blisters, swelling, gaps, cracks, loss of material, loss of neutron-attenuation 

capability). 

2) Describe the surveillance or monitoring program used to confirm that the credited 

neutron-absorbing material is performing its safety function, including the frequency, 

limitations, and accuracy of the methodologies used. 

a) Provide the technical basis for the surveillance or monitoring method, including a 

description of how the method can detect degradation mechanisms that affect the 

material’s ability to perform its safety function. Also, include a description and technical 

basis for the technique(s) and method(s) used in the surveillance or monitoring program, 

including: 

i) approach used to determine frequency, calculations, and sample size; 

ii) parameters to be inspected and data collected; 

iii) acceptance criteria of the program and how they ensure that the material’s structure 

and safety function are maintained within the assumptions of the NCS AOR; 

iv) monitoring and trending of the surveillance or monitoring program data; and 

v) industry standards used. 

b) For the following monitoring methods, include these additional discussion items. 

i) If there is visual inspection of inservice material: 

(1) describe the visual inspection performed on each sample; and 
GL 2016-01 

Appendix A 

Page 3 of 5 

(2) describe the scope of the inspection (i.e., number of panels or inspection points 

per inspection period). 

ii) If there is a coupon-monitoring program: 

(1) provide a description and technical basis for how the coupons are representative 

of the material in the racks. Include in the discussion the material radiation 

exposure levels, SFP environment conditions, exposure to the SFP water, 

location of the coupons, configuration of the coupons (e.g., jacketing or 

sheathing, venting bolted on, glued on, or free in the jacket, water flow past the 

material, bends, shapes, galvanic considerations, and stress-relaxation 

considerations), and dimensions of the coupons; 

(2) provide the dates of coupon installation for each set of coupons; 

(3) if the coupons are returned to the SFP for further evaluation, provide the 

technical justification for why the reinserted coupons would remain representative 

of the materials in the rack; and 

(4) provide the number of coupons remaining to be tested and whether there are 

enough coupons for testing for the life of the SFP. Also provide the schedule for 

coupon removal and testing. 

iii) If RACKLIFE is used: 

(1) note the version of RACKLIFE being used (e.g., 1.10, 2.1); 

(2) note the frequency at which the RACKLIFE code is run; 

(3) describe the confirmatory testing (e.g., in-situ testing) being performed and how 

the results confirm that RACKLIFE is conservative or representative with respect 

to neutron attenuation; and 

(4) provide the current minimum RACKLIFE predicted areal density of the neutronabsorbing material in the SFP. Discuss how this areal density is calculated in 

RACKLIFE. Include in the discussion whether the areal densities calculated in 

RACKLIFE are based on the actual as-manufactured areal density of each panel, 

the nominal areal density of all of the panels, the minimum certified areal density, 

the minimum as-manufactured areal density, or the areal density credited by the 

NCS AOR. Also discuss the use of the escape coefficient and the total silica rate 

of Boraflex degradation in the SFP. 

iv) If in-situ testing with a neutron source and detector is used (e.g., BADGER testing, 

blackness testing): 

(1) describe the method and criteria for choosing panels to be tested and include 

whether the most susceptible panels are chosen to be tested. Provide the 

statistical sampling plan that accounts for both sampling and measurement error 

and consideration of potential correlation in sample results. State whether it is 
GL 2016-01 

Appendix A 

Page 4 of 5 

statistically significant enough that the result can be extrapolated to the state of 

the entire pool; 

(2) state if the results of the in-situ testing are trended and whether there is repeat 

panel testing from campaign to campaign; 

(3) describe the sources of uncertainties when using the in-situ testing device and 

how they are incorporated in the testing results. Include the uncertainties 

outlined in the technical letter report titled “Initial Assessment of Uncertainties 

Associated with BADGER Methodology,” September 30, 2012 (Agencywide 

Document Access and Management System Accession No. ML12254A064). 

Discuss the effect of rack cell deformation and detector or head misalignment, 

such as tilt, twist, offset, or other misalignments of the heads and how they are 

managed and accounted for in the analysis; and 

(4) describe the calibration of the in-situ testing device, including the following: 

(a) describe how the materials used in the calibration standard compare to the 

SFP rack materials and how any differences are accounted for in the 

calibration and results; 

(b) describe how potential material changes in the SFP rack materials caused by 

degradation or aging are accounted for in the calibration and results; and 

(c) if the calibration includes the in-situ measurement of an SFP rack “reference 

panel,” explain the following: 

(i) the methodology for selecting the reference panel(s) and how the 

reference panels are verified to meet the requirements; 

(ii) whether all surveillance campaigns use the same reference panel(s); and 

(iii) if the same reference panels are not used for each measurement 

surveillance, describe how the use of different reference panels affects 

the ability to make comparisons from one campaign to the next. 

3) For any Boraflex, Carborundum, or Tetrabor being credited, describe the technical basis for 

determining the interval of surveillance or monitoring for the credited neutron-absorbing 

material. Include a justification of why the material properties of the neutron-absorbing 

material will continue to be consistent with the assumptions in the SFP NCS AOR between 

surveillances or monitoring intervals. 

4) For any Boraflex, Carborundum, Tetrabor, or Boral being credited, describe how the 

credited neutron-absorbing material is modeled in the SFP NCS AOR and how the 

monitoring or surveillance program ensures that the actual condition of the 

neutron-absorbing material is bounded by the NCS AOR. 

a) Describe the technical basis for the method of modeling the neutron-absorbing material 

in the NCS AOR. Discuss whether the modeling addresses degraded neutron-absorbing 
GL 2016-01 

Appendix A 

Page 5 of 5 

material, including loss of material, deformation of material (such as blisters, gaps, 

cracks, and shrinkage), and localized effects, such as non-uniform degradation. 

b) Describe how the results of the monitoring or surveillance program are used to ensure 

that the actual condition of the neutron-absorbing material is bounded by the SFP NCS 

AOR. If a coupon monitoring program is used, provide a description and technical basis 

for the coupon tests and acceptance criteria used to ensure the material properties of 

the neutron-absorbing material are maintained within the assumptions of the NCS AOR. 

Include a discussion on the measured dimensional changes, visual inspection, observed 

surface corrosion, observed degradation or deformation of the material (e.g., blistering, 

bulging, pitting, or warping), and neutron-attenuation measurements of the coupons. 

c) Describe how the bias and uncertainty of the monitoring or surveillance program are 

used in the SFP NCS AOR. 

d) Describe how the degradation in adjacent panels is correlated and accounted for in the 

NCS AOR. 

5) For any Boraflex, Carborundum, or Tetrabor being credited, describe the technical basis for 

concluding that the safety function for the credited neutron-absorbing material in the SFP 

will be maintained during design-basis events (e.g., seismic events, loss of SFP cooling, fuel 

assembly drop accidents, and any other plant-specific design-basis events that may affect 

the neutron-absorbing material). 

a) For each design-basis event that would have an effect on the neutron-absorbing 

material, describe the technical basis for determining the effects of the design-basis 

event on the material condition of the neutron-absorbing material during the design-basis 

event, including: 

i) shifting or settling relative to the active fuel; 

ii) increased dissolution or corrosion; and 

iii) changes of state or loss of material properties that hinder the neutron-absorbing 

material’s ability to perform its safety function. 

b) Describe how the monitoring program ensures that the current material condition of the 

neutron-absorbing material will accommodate the stressors during a design-basis event 

and remain within the assumptions of the NCS AOR, including: 

i) monitoring methodology; 

ii) parameters monitored; 

iii) acceptance criteria; and 

iv) intervals of monitoring.