Acceptable Standard 

Format and Content for 

the Material Control and 

Accounting Plan Required 

for Special Nuclear 

Material of Moderate 

Strategic Significance

Draft Report for Comment

Office of Nuclear Material Safety and Safeguards

NUREG-2159
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Legally binding regulatory requirements are stated only 

in laws; NRC regulations; licenses, including technical 

specifications; or orders, not in NUREG-series 

publications. The views expressed in contractorprepared publications in this series are not necessarily 

those of the NRC.

The NUREG series comprises (1) technical and 

administrative reports and books prepared by the staff 

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DISCLAIMER: This report was prepared as an account 

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expressed or implied, or assumes any legal liability or 

responsibility for any third party’s use, or the results of 

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its use by such third party would not infringe privately 

owned rights.
Acceptable Standard 

Format and Content for 

the Material Control and 

Accounting Plan Required 

for Special Nuclear 

Material of Moderate 

Strategic Significance

Draft Report for Comment

Manuscript Completed: June 2013 

Date Published: September 2013

Office of Nuclear Material Safety and Safeguards

NUREG-2159

 
COMMENTS ON DRAFT REPORT

Any interested party may submit comments on this report for consideration by the NRC staff. 

Comments may be accompanied by additional relevant information or supporting data. Please 

specify the report number NUREG-2159 in your comments, and send them by the end of the 

comment period specified in the Federal Register notice announcing the availability of this 

report. 

Addresses: You may submit comments by any one of the following methods. Please include 

Docket ID NRC-2013-0195 in the subject line of your comments. Comments submitted in 

writing or in electronic form will be posted on the NRC website and on the Federal rulemaking 

website http://www.regulations.gov. 

Federal Rulemaking Website: Go to http://www.regulations.gov and search for documents 

filed under Docket ID NRC-2013-0195. Address questions about NRC dockets to Carol 

Gallagher at 301-287-3422 or by e-mail at Carol.Gallagher@nrc.gov.

Mail comments to: Cindy Bladey, Chief, Rules, Announcements, and Directives Branch

(RADB), Division of Administrative Services, Office of Administration, Mail Stop: 3WFN-06-A44, 

U.S. Nuclear Regulatory Commission, Washington, DC 20555-0001.

For any questions about the material in this report, please contact: Tom Pham, Senior 

Safeguards Analyst, at 301-287-9132 or by e-mail at Tom.Pham@nrc.gov.

Please be aware that any comments that you submit to the NRC will be considered a public 

record and entered into the Agencywide Documents Access and Management System 

(ADAMS). Do not provide information you would not want to be publicly available..
iii NUREG-2159

ABSTRACT

In 2000, the U.S. Nuclear Regulatory Commission (NRC) revised the material control and 

accounting (MC&A) regulations for licensees authorized to possess and use special nuclear 

material (SNM) of moderate strategic significance. This class of material is sometimes referred 

to as a Category II quantity of material. The NRC issued such amendments as Subpart D, 

“Special Nuclear Material of Moderate Strategic Significance,” in Title 10 of the Code of Federal 

Regulations (10 CFR) Part 74, “Material Control and Accounting of Special Nuclear Material.” 

These regulations apply to licensees or applicants other than production or utilization facilities 

and waste disposal facilities.

SNM of moderate strategic significance means either of the following:

1. less than a formula quantity of strategic special nuclear material but more than 

1,000 grams of uranium-235 (contained in uranium enriched to 20 percent or more in the 

235U isotope) or more than 500 grams of uranium-233 or plutonium or in a combined 

quantity of more than 1,000 grams when computed by the equation:

grams = (grams contained 235U) + 2(grams 233U + grams plutonium), or

2. 10,000 grams or more of 235U (contained in uranium enriched to 10 percent of more but 

less than 20 percent in the 235U isotope)

This document provides a structure and information to facilitate compliance with the following 

regulations regarding the licensee or applicant preparation and implementation of material 

control and accounting (MC&A) plans and corresponding NRC review and inspection:

• 10 CFR 74.3, “General Performance Objectives”

• 10 CFR 74.41, “Nuclear Material Control and Accounting for Special Nuclear Material 

of Moderate Strategic Significance”

• 10 CFR 74.43, “Internal Controls, Inventory, and Records”

• 10 CFR 74.45, “Measurements and Measurement Control”

Such performance-based MC&A requirements, which cover all Category II quantities of 

material, replace the prescriptive approach that appeared previously in 10 CFR Part 70, 

“Domestic Licensing of Special Nuclear Material,” before the NRC consolidated these MC&A 

requirements in 10 CFR Part 74. Presented herein is the acceptable format and content for 

those MC&A plans, which address the following: 

(1) the performance objectives that must be met

(2) the MC&A program capabilities that must be achieved to meet those objectives
NUREG-2159 iv

(3) the incorporation of checks and balances to detect falsification of data and reports that 

could conceal the theft or diversion of SNM

(4) basic commitments that should be made
v NUREG-2159

CONTENTS

ABSTRACT...............................................................................................................................iii

CONTENTS............................................................................................................................... v

ACRONYMS AND ABBREVIATIONS.......................................................................................ix

1. INTRODUCTION ................................................................................................................... 1

2. GENERAL PERFORMANCE OBJECTIVES, RELATED REQUIREMENTS, 

COMMITMENTS, AND ACCEPTANCE CRITERIA............................................................... 3

3. MANAGEMENT STRUCTURE .............................................................................................. 9

3.0 Regulatory Intent............................................................................................................. 9

3.1 Corporate Organization ................................................................................................... 9

3.2 Plant or Site Organization................................................................................................ 9

3.3 MC&A Organization........................................................................................................10

3.3.1 Responsibilities and Authority..................................................................................10

3.3.2 MC&A Procedures...................................................................................................10

3.4 Training and Qualification Requirements........................................................................11

3.5 MC&A Program Description ...........................................................................................11

3.6 Material Control Boundaries ...........................................................................................12

3.7 Commitments and Acceptance Criteria ..........................................................................12

4. MEASUREMENTS...............................................................................................................15

4.0 Regulatory Intent............................................................................................................15

4.1 Measurement Points ......................................................................................................15

4.2 Measurement Systems...................................................................................................16

4.2.1 Bulk Measurement Systems ....................................................................................16

4.2.2 Analytical Measurement Systems............................................................................17

4.2.3 NDA Measurement Systems ...................................................................................17

4.2.4 Other Measurement Systems ..................................................................................18

4.3 Measurement Uncertainties............................................................................................18

4.4 Measurement Procedures ..............................................................................................18

4.5 Scrap Control .................................................................................................................18

4.6 Commitments and Acceptance Criteria ..........................................................................19

5. MEASUREMENT CONTROL SYSTEM ...............................................................................21

5.0 Regulatory Intent............................................................................................................21

5.1 Organization and Management ......................................................................................21

5.1.1 Functional Relationships..........................................................................................21

5.1.2 Procedures..............................................................................................................21

5.1.3 Contractor Program Audits and Reviews .................................................................22

5.2 Calibrations ....................................................................................................................22

5.3 Control Standards ..........................................................................................................24

5.4 Replicate Sampling ........................................................................................................25

5.5 Control Limits .................................................................................................................26

5.5.1 Measurement Control Data Analysis........................................................................27

5.5.2 Response Actions....................................................................................................27

5.6 Commitments and Acceptance Criteria ..........................................................................28

6. STATISTICS........................................................................................................................31

6.0 Regulatory Intent............................................................................................................31
NUREG-2159 vi

6.1 Determination of Measurement Uncertainties.................................................................31

6.2 Determination of Standard Error of the Inventory Difference ..........................................32

6.3 Bias Corrections.............................................................................................................32

7. PHYSICAL INVENTORIES..................................................................................................35

7.0 Regulatory Intent............................................................................................................35

7.1 General Description........................................................................................................35

7.2 Organization, Procedures, and Schedules .....................................................................35

7.3 Typical Inventory Composition........................................................................................36

7.4 Description of Typical Item Strata...................................................................................36

7.5 Conducting Physical Inventories.....................................................................................36

7.6 Inventory Difference Limits and Response Actions.........................................................39

7.7 Commitments and Acceptance Criteria ..........................................................................40

8. ITEM CONTROL..................................................................................................................43

8.0 Regulatory Intent............................................................................................................43

8.1 Organization...................................................................................................................43

8.2 General Description........................................................................................................43

8.3 Item Identity Controls .....................................................................................................44

8.4 Storage Controls ............................................................................................................44

8.5 Item Monitoring Methodology and Procedures ...............................................................44

8.6 Investigation and Resolution of Item Discrepancies........................................................45

8.7 Commitments and Acceptance Criteria ..........................................................................45

9. SHIPPER RECEIVER COMPARISONS ..............................................................................47

9.0 Regulatory Intent............................................................................................................47

9.1 Receiving Procedures ....................................................................................................47

9.2 Determination of Receiver's Values................................................................................48

9.3 Evaluation of Shipper-Receiver Differences ...................................................................48

9.4 Resolution of Significant Shipper–Receiver Differences .................................................49

9.5 Commitments and Acceptance Criteria ..........................................................................49

10. ASSESSMENT AND REVIEW OF THE MATERIAL CONTROL AND 

 ACCCOUNTING PROGRAM .............................................................................................51

10.0 Regulatory Intent..........................................................................................................51

10.1 General Description......................................................................................................51

10.2 Report of Findings and Recommendations...................................................................52

10.3 Management Review and Response to Report Findings and Recommendations.........53

10.4 Commitments and Acceptance Criteria ........................................................................53

11. TAMPER-SAFING .............................................................................................................57

11.0 Regulatory Intent..........................................................................................................57

11.1 Characteristics of Tamper-Safing Devices....................................................................57

11.2 Use of Tamper-Safing Devices.....................................................................................58

11.3 Description of Tamper-Safing Records.........................................................................58

11.4 Commitments and Acceptance Criteria ........................................................................59

12. DESIGNATION OF MATERIAL BALANCE AREAS, ITEM CONTROL AREAS, 

 AND CUSTODIANS ...........................................................................................................61

12.0 Regulatory Intent..........................................................................................................61

12.1 Material Control Boundaries .........................................................................................61
vii NUREG-2159

12.2 Custodians ...................................................................................................................61

12.3 Commitments and Acceptance Criteria ........................................................................61

13. RESOLVING INDICATIONS OF LOSS, THEFT, DIVERSION OR MISUSE 

 OF SPECIAL NUCLEAR MATERIAL.................................................................................63

13.0 Regulatory Intent..........................................................................................................63

13.1 Methods and Procedures for Identifying Indicators .......................................................63

13.2 System and Procedures for Investigating and Resolving Loss Indicators .....................63

13.3 Response Actions for Unresolved Indicators ................................................................64

13.4 Documentation Requirements ......................................................................................64

13.5 Commitments and Acceptance Criteria ........................................................................65

14. INFORMATIONAL AID FOR ASSISTING IN THE INVESTIGATION AND 

 RECOVERY OF MISSING SPECIAL NUCLEAR MATERIAL............................................67

14.0 Regulatory Intent..........................................................................................................67

14.1 Types of Information.....................................................................................................67

14.2 Information Indicating Possible Losses of SNM............................................................67

14.3 Information on Resolving Indications of Missing SNM ..................................................68

14.4 Commitments and Acceptance Criteria ........................................................................69

15. RECORDKEEPING ...........................................................................................................71

15.0 Regulatory Intent..........................................................................................................71

15.1 Description of Records .................................................................................................71

15.2 Program and Controls for Ensuring an Accurate and Reliable Record System.............72

15.3 Commitments and Acceptance Criteria ........................................................................73

16. GLOSSARY.......................................................................................................................77

17. REFERENCES ..................................................................................................................81

ix NUREG-2159

ACRONYMS AND ABBREVIATIONS

AEC U.S. Atomic Energy Commission

CFR Code of Federal Regulations

DOE U.S. Department of Energy

EI ending inventory

FKG formula kilogram

IAEA International Atomic Energy Agency

ICA item control area

ID inventory difference

MBA material balance area

MC&A material control and accounting

MOX mixed oxide

NDA nondestructive assay

NRC U.S. Nuclear Regulatory Commission

Pu plutonium

PuO2 plutonium dioxide

SEID standard error of the inventory difference

SNM special nuclear material 

SRD shipper–receiver difference 

SQ significant quantity

TID tamper-indicating device

U uranium

233U uranium-233

234U uranium-234

235U uranium-235

238U uranium-238

UO2 uranium dioxide

U3O8 urano-uranic oxide

UF6 uranium hexafluoride 

wt % weight percent

1 NUREG-2159

1. INTRODUCTION

The Atomic Energy Act of 1954, as amended, directed the U.S. Atomic Energy Commission 

(AEC) to regulate the receipt, manufacture, production, transfer, possession, use, import, and 

export of special nuclear material (SNM) to protect the public health and safety and to provide 

for the common defense and security. The Energy Reorganization Act of 1974 transferred all 

the licensing and related functions of the AEC to the U.S. Nuclear Regulatory Commission 

(NRC). 

The principal requirements for SNM licensing are found in Title 10 of the Code of Federal 

Regulations (CFR) Part 70, “Domestic Licensing of Special Nuclear Material,” and 10 CFR

Part 74 (10 CFR Part 74), “Material Control and Accounting of Special Nuclear Material.” 

Regulations in 10 CFR 70.22 (b) specify that a full description of the applicant’s program for the 

control and accounting of such SNM must be contained in a license application to show how 

compliance with the graded material control and accounting (MC&A) requirements of 10 CFR 

Part 74, Subparts B–E, will be accomplished. This document describes the standard format and 

content suggested by the NRC for use in preparing MC&A plans for facilities authorized to hold 

SNM of moderate strategic significance. 

This introduction describes the basis of the five general performance objectives of 

10 CFR 74.3,”General Performance Objectives” and the MC&A system features and capabilities

needed to meet the objectives. Chapters 3–12 address the program capabilities needed to 

maintain accurate, current, and reliable information on—and confirm the quantities and locations 

of—SNM in the licensee’s possession. Chapters 13 and 14 address the program capabilities 

needed to promptly investigate and resolve anomalies indicating a possible loss of SNM and 

provide information to aid in the investigation and recovery of missing SNM. Chapter 15

addresses recordkeeping requirements. These 13 chapters are intended to provide an outline 

for an acceptable MC&A plan for facilities authorized to hold SNM of moderate strategic 

significance. 

The acceptance criteria are for the use of applicants (or licensees) and NRC licensing 

reviewers. An application or proposed revisions that meet these criteria should be acceptable to 

the NRC staff. However, comprehensive criteria are included as examples, and each applicant 

or licensee should develop an MC&A program and plan that take into account the unique 

features of its particular operation. When additional guidance is available on particular topics, 

an appropriate reference is included in the acceptance criteria section. Recommendations in 

this document provide guidance to applicants and licensees. Licensees may use this guidance 

when making changes to their existing approved MC&A plans.

In preparing MC&A plans, applicants should keep in mind the capabilities specified in 

10 CFR 74.41, “Nuclear Material Control and Accounting for Special Nuclear Material of 

Moderate Strategic Significance,” 10 CFR 74.43, “Internal Controls, Inventory, and Records,”

and 10 CFR 74.45, “Measurements and Measurement Control.” They should also consider the 

general performance objectives specified in 10 CFR 74.3, “General Performance Objectives.” 

Because 10 CFR 74.3, 74.41, 74.43, and 74.45 are performance-oriented regulations, they do 

not contain a detailed set of technical specifications. With this flexibility, applicants and 

licensees have many alternatives for how their overall MC&A program is designed, managed, 

and operated, which permits a risk-informed, performance-based approach that focuses on 

MC&A activities most important to safeguards. Accordingly, this document does not cover all 

possible methods that a licensee might use to meet the MC&A requirements. Instead, this 
NUREG-2159 2

document provides examples of acceptable MC&A approaches that may be used. This 

guidance is intended for use by applicants, licensees, and the NRC safeguards licensing 

reviewers. Users should not regard acceptance criteria as rigid, fixed standards. That is, a 

lower effectiveness of one capability relative to a particular aspect is acceptable if there is a 

compensating system feature, or combination of features, that provides an overall effective 

safeguards system. In the final analysis, an NRC reviewer must find that the applicant’s or 

licensee’s MC&A plan provides adequate assurance that all applicable regulatory requirements 

will be met. 

The contents of an MC&A plan are discussed in Chapters 3–15 below. The body of an 

approved MC&A plan will be made a condition of license in accordance with 10 CFR 70.32(c), 

and compliance with the MC&A plan commitments and pertinent procedures will be inspectable. 

Explanations and discussions appearing in the body of the plan should be sufficiently detailed 

and precise so that NRC licensing reviewers, NRC inspectors, and licensee personnel 

responsible for developing and implementing the plan have a clear and common understanding 

of what the MC&A plan requires. 

The annex (or appendix) of an MC&A plan should provide supplementary and general 

information about the facility and the MC&A program and subsystems (e.g., copies of blank 

record forms, site map, process diagrams, an example standard error of the inventory difference 

(SEID) calculation, etc.). The annex will not be incorporated as a condition of license and will 

not be the basis for inspection. Thus, descriptions presented by the applicant or licensee to 

meet regulatory requirements must be in the plan itself, rather than the annex, and must provide 

adequate detail so as not to be largely dependent on examples or supplementary information in 

the annex for proper understanding. Procedures detailed in the annex may be changed without 

NRC approval or notification provided that the changes do not degrade plan commitments and 

capabilities. 

Preparation of an MC&A plan with this standard format will assist the NRC in evaluating the plan 

and in standardizing the licensing and review process. However, the NRC does not require 

conformance with the standard format. An applicant may use a different format if it provides an 

equal level of completeness and detail.
3 NUREG-2159

2. GENERAL PERFORMANCE OBJECTIVES, RELATED 

REQUIREMENTS, COMMITMENTS, 

AND ACCEPTANCE CRITERIA

General Performance Objectives

The five general MC&A performance objectives applicable to all NRC licensees certified under 

Title 10 of the Code of Federal Regulations (10 CFR) Part 70, “Domestic Licensing of Special 

Nuclear Material,” are set forth in Subpart A, “General Provisions,” of 10 CFR Part 74, “Material 

Control and Accounting of Special Nuclear Material.” Specifically, these appear in 10 CFR 74.3, 

“General Perfomance Objectives.” The following information discusses the basis of these 

general performance objectives, and the related requirements in Subpart D, “Special Nuclear 

Material of Moderate Strategic Significance,” of 10 CFR Part 74 (applicable to NRC licensees 

authorized to hold special nuclear material (SNM) of moderate strategic significance).

1. Maintain accurate, current, and reliable information on, and confirm the 

quantities and locations of, SNM in the licensee’s possession.

The purpose of this objective is to verify the presence of all SNM held by the licensee, and to

detect the occurrence of any significant loss, including possible theft or diversion. To maintain 

current information on all such SNM, licensees should have in place a program that provides 

timely, accurate, reliable information about the quantity and location of SNM in their possession. 

Accurate information means that item quantities for plutonium, the element uranium, and the 

isotopes uranium-235 (

235U) and Uranium-233 (233U) are based on measured values or on 

reliable information. Reliable information means that the quantity of SNM in an item and the 

location of all items are known (except for items in solutions with a concentration of less than 

5 grams of 235U per liter and items of waste destined for burial or incineration). The location 

designations must be specific enough to provide for the retrieval of the items in a prompt 

manner. Reliable information also means that the quantities and locations of all nonexempt 

SNM material, and items listed in the accounting records, are correct and verifiable.

The licensee or applicant should accurately account for all SNM that is received and shipped by 

maintaining reliable records based on accurate measurements. When a shipment is received, 

the licensee should begin monitoring movement and location of the material within the facility 

using item control procedures (1) to monitor the location and integrity of items until they are 

processed, and (2) to ensure all SNM quantities of record associated with receipts, shipments, 

discards, and ending inventory are based on measurements. Monitoring the material in process 

may involve the use of process or material control data. Licensees and applicants should 

maintain a detailed and accurate recordkeeping system for the generated data that provides 

knowledge of the material’s location in a timely manner. 

The licensee must conduct total plant physical inventories at intervals not to exceed 9 calendar 

months, in accordance with 10 CFR 74.43(c)(7). Each physical inventory must be conducted in 

a manner so that the detection of any actual significant loss, including possible theft or 

diversion, would be assured by evaluating each inventory difference (ID) using a standard error 

of the inventory difference (SEID) that is less than 0.125 percent of the active inventory. As a 

result, the investigation and reporting of any ID that exceeds three times SEID is equivalent to a 

hypothesis test that provides 90 percent power for detecting a discrepancy as small as 

0.4 percent of active inventory at a 5 percent false alarm rate.
NUREG-2159 4

The licensee should verify the presence of all Category II SNM held under license, as 

documented in its accounting records. This verification is normally accomplished by the 

following means:

• a shutdown and cleanout of processing equipment

• measurement of cleanout materials and measurement of any materials not previously 

measured in their existing form

• visual verification (on a 100 percent basis) of the presence of all possessed SNM items 

(by means of unique item identities)

• confirming the SNM quantities associated with unencapsulated and unsealed items on 

ending inventory. 

However, a dynamic (i.e., non-shutdown) inventory of some or all processing equipment may be 

used if the measurement uncertainty associated with the total material balance (for the inventory 

period) is within the 0.125 percent of active inventory constraint specified in 

10 CFR 74.43(c)(8)(iii) and 10 CFR 74.45(c)(4). 

Chapter 7 of this document details recommendations pertaining to physical inventories. In 

summary, a total plant physical inventory involves:

(1) verifying the presence, on a 100 percent basis, of all uniquely identified SNM items listed 

in the accounting records

(2) measuring (by direct measurement or, if direct measurement is not feasible, by indirect 

measurement) all bulk SNM quantities on hand (i.e., all SNM not in item form)

(3) measuring any items not previously measured

(4) verifying the identity and integrity of all encapsulated items and items affixed with 

tamper-indicating devices

(5) measuring an SNM-related parameter for a sample of randomly selected 

unencapsulated and unsealed items, based on a statistical sampling plan, to verify the 

previously measured quantities of SNM contained in such items

The physical inventory program should be managed and maintained independent of the 

production or operations organization, but it should not be excluded from using process 

monitoring and production control data.

2. Detect, respond to, and resolve any anomaly indicating a possible loss, theft, 

diversion, or misuse of SNM has occurred.

3. Permit rapid determination of whether an actual loss, theft, diversion, or misuse

of SNM has occurred.

As discussed further in Chapter 13, to meet the requirements of 10 CFR 74.3(b)–(c), the 

licensee or applicant should have a formalized program to promptly investigate and resolve any 
5 NUREG-2159

anomaly that may indicate a possible loss of SNM. Resolution of such anomalies means that 

the licensee has made a rapid determination about if an actual loss of a significant quantity of 

SNM has occurred, including possible theft or diversion. An anomaly detected during a 

material balance closure needs to be investigated and resolved in accordance with 

10 CFR 74.43(c)(8)(iii). 

Resolution of an anomaly depends on the type of indicator. Various types of anomalies at 

plants could occur from a wide range of possible underlying scenarios (e.g., from unidentified or 

inadequately monitored loss mechanisms, simple theft, or complex diversions). The 

investigation and resolution process should begin with a thorough review of the MC&A records 

to locate obvious errors. These might include omissions of entire items, incorrect entries to 

computer programs or records, transcription errors, incorrect estimates of the amount of holdup 

in equipment, or calculation errors. A detailed examination of the MC&A records for each 

material type should identify gross errors. The next stage in the resolution process would be to 

isolate the process or storage area that appears to be causing the anomaly. Once this is done, 

all of the information that contributed to the SNM quantities for that location should be verified. 

If resolution still is not accomplished, the licensee should re-measure and sample material in the 

process or storage areas to verify quantities. If the investigation of an indicator results in a 

determination that an actual loss or theft has occurred, the loss or theft must be reported to the 

NRC in accordance with 10 CFR 74.11, “Reports of Loss or Theft or Attempted Theft or 

Unauthorized Production of Special Nuclear Material.” 

4. Provide information to aid in the investigation and recovery of missing SNM in the 

event of an actual loss, theft, diversion, or misuse.

If the NRC or other government agency deems it necessary to conduct an investigation of actual 

(or highly suspected) events concerning missing material, the licensee should provide any 

information it deems relevant to the recovery of material involved in a loss, theft, or diversion. 

The burden shall be on the licensee to provide all information that it recognizes as being 

relevant, as opposed to providing only information that the investigators request. Chapter 14

provides additional information and recommendations concerning the provision of information to 

aid in investigations.

5. Control access to MC&A information that might assist adversaries to carry out acts 

of theft, diversion, misuse, or radiological sabotage involving SNM.

The purpose of this performance objective in 10 CFR 74.3(e) is to implement the practices and 

procedures needed to provide effective material control and material accounting with respect to 

deterrence and detection of theft, diversion, misuse, or radiological sabotage involving SNM. 

Licenses should control access to MC&A information through access control, material 

containment, and material surveillance. Effective control systems should be multi-layered, and 

licensees should use redundant systems to eliminate the consequence of a single-point failure.

The licensee should implement an effective quality assurance program that minimizes the 

possibility of potential failures for the MC&A program, and these control measures can 

contribute to deterrence of material loss, theft, diversion, or misuse by providing necessary 

checks and balances. Access control involving all movements of people and materials into and 

out of the material access areas should be carefully monitored and controlled. Adequate 

containment and surveillance measures should provide assurance that the integrity of nuclear 

material values is maintained.
NUREG-2159 6

Primary attention should be given to preventing errors or mistakes by MC&A personnel and to 

preventing violations of procedures or compromise of MC&A information and data. A system of 

checks and balances should be established to ensure data accuracy, and this system should 

detect any instances of unauthorized access to data. Mistakes caused by inadequate training, 

accidents, improper equipment operation or maintenance, or any other unintentional actions can 

lead to the MC&A program losing its effectiveness.

In addition to the 10 CFR 74.3 general performance objectives focusing on the prevention of 

theft, licensees authorized to hold SNM of moderate strategic significance must, in accordance 

with 10 CFR 74.41(c), be able to detect the falsification of data that could conceal the diversion 

of SNM by: (1) a single individual, including an employee in any position, or (2) collusion 

between two individuals, one or both of whom have authorized access to SNM. 

The MC&A program and plan needs to protect against only a single insider, providing that 

individual does not have authority within the physical protection system that would permit him or 

her to participate in a conspiracy aimed at defeating the safeguards system. If an MC&A 

individual does have authority within the physical protection system, then the MC&A program 

and plan is required to protect against the coverup of a collusion of that individual with any other 

individual having MC&A authority.

This approach should relieve licensees of most of the burden that would result from requiring a 

totally redundant system while still maintaining the ability of the MC&A program and plan to 

provide an extra level of independent protection and an added measure of assurance that the 

safeguards system as a whole has not been compromised.

The licensee should analyze all positions having responsibility within the 10 CFR Part 74 MC&A 

program to determine if any such positions also have responsibility within the 10 CFR Part 73, 

“Physical Protection of Plants and Materials,” system. A safeguards manager could be an 

example of such a position. If this position includes both MC&A and physical protection 

responsibilities, licensees would have to develop procedures to ensure the following:

• When an individual in this job is performing an MC&A function, this function would be

performed in the presence of at least two other people (industry procedures often 

reference this as a “three-person rule”).

• Performance of the function would be independently checked later by a third party.

• Abuse of authority would be otherwise protected against.

To address collusion concerns, an MC&A function performed by a worker without physical 

protection system authority would need to be protected against a single insider threat. 

Commitments and Acceptance Criteria Pertaining to General Performance Objectives

In its MC&A plan, the applicant or licensee should provide definitive commitments that adhere to 

the regulatory requirements and meet the acceptance criteria for these general performance 

objectives and corresponding program capabilities. These commitments should be stated in the 

MC&A plan.

Chapters 3–5 and 7–15 list the commitments and acceptance criteria.
7 NUREG-2159

The following chapters of this document incorporate and expand on the performance objectives 

and on the MC&A program and plan capabilities specified in 10 CFR 74.3 and 10 CFR 74.41, 

“Nuclear Material Control and Accounting for Special Nuclear Material of Moderate Strategic 

Significance.” The chapters are arranged in a format and sequence to provide applicants and 

licensees an outline for the required MC&A plan.

9 NUREG-2159

3. MANAGEMENT STRUCTURE

3.0 Regulatory Intent

The intent of Title 10 of the Code of Federal Regulations (10 CFR) 74.43(b)(1) through (4) is to 

require licensees to implement a management structure that permits effective functioning of the 

material control and accounting (MC&A) system and assures that the MC&A program 

performance will not be adversely affected by the plant management structure. Documentation, 

review, and approval of critical MC&A procedures, and the assignment of the key functions to 

specific positions, eliminate ambiguities about what is to be done by whom. The management 

structure is meant to separate key MC&A functions from each other to incorporate checks and 

balances that increase MC&A system reliability and make the theft or diversion of SNM less 

likely. It is also meant to free MC&A management personnel from conflicts of interest with other 

major functions, such as production. 

Regulations in 10 CFR 74.43(b)(2) require that a single individual be responsible for the overall 

planning, coordination, and administration of MC&A functions. All licensee personnel who work 

in key MC&A positions must be trained to maintain a high level of safeguards awareness in 

accordance with 10 CFR 74.43(b)(4).

3.1 Corporate Organization

Licensees should describe the corporate structure and should identify all corporate organization 

positions that have responsibilities related to MC&A at the licensee's site. A description of the 

corporate-level functions, responsibilities, and authorities for MC&A program oversight and 

assessments should be provided. At least one corporate official should have responsibility for

the control and accounting of all SNM possessed by the licensee.

3.2 Plant or Site Organization

Licensees should provide a description of the site’s management structure emphasizing MC&A. 

The site management structure should be described to the extent that it can be clearly shown 

that the MC&A organization is independent of potentially conflicting responsibilities. This 

description should also indicate how responsibilities are assigned for the following functions:

• overall MC&A program

• SNM custodianship

• receiving and shipping of SNM

• analytical laboratories

• bulk and nondestructive assay (NDA) measurements

• sampling operations

• measurement control system

• physical inventories

• onsite SNM handling operations

A brief description should be provided for each site-level position, outside of the MC&A 

organization, that has responsibilities for MC&A activities (e.g., sampling, mass measurements, 

analytical measurements, and measurement control). For each position, licensees should 

clearly describe the functions, responsibilities, and authorities.
NUREG-2159 10

3.3 MC&A Organization

An organizational chart and position-by-position description of the entire MC&A organization 

should be provided. A licensee should designate an individual as the overall manager of the 

MC&A program, and the MC&A plan must demonstrate the assurance of independence of 

action and objectivity of decision for the MC&A manager. Two options for meeting the 

organizational independence are: (1) report directly to the plant or site manager, or (2) report to 

an individual who reports to the plant or site manager through a management chain with no 

production responsibilities.

3.3.1 Responsibilities and Authority

Licensees should provide a description that clearly indicates the responsibilities and authority of 

each supervisor and manager for the various functions within the MC&A organization. The 

description should indicate how the activities of one functional unit or individual serve as a 

control over, or checks on, the activities of other units or individuals. The MC&A plan should 

explain how coordination is achieved and maintained between the MC&A organization and other 

plant organizational groups that perform MC&A-related activities. A definitive statement should 

be made specifying how the MC&A manager assures appropriate review and approval for all 

written procedures pertaining to MC&A-related activities, and to any future revisions thereto, 

which are issued both within and outside of the MC&A organization. In addition to the MC&A 

manager function, the plan should address, at a minimum, the following functions:

• nuclear material accounting

• measurement control system 

• item control system 

• statistical applications

Whenever more than one key MC&A function is assigned to the same person, the MC&A plan 

should clearly describe the checks and balances that preclude the following:

(A) performance of accounting or record control functions by individuals who also generate

source data

(B) assignment of sole authority to any individual to overcheck, evaluate, or audit 

information for which he or she is responsible

For individuals in management or supervisory positions, some modifications to procedures, 

such as restricting unescorted access to some areas, may be necessary to provide sufficient 

assurance that the system cannot be compromised.

3.3.2 MC&A Procedures

Regulations in 10 CFR 74.43(b)(3) require that the use of written MC&A procedures that are 

critical to the effectiveness of the MC&A system be described, and the approved MC&A plan 

must identify such procedures. Critical MC&A procedures are those written procedures that, if 

not performed correctly, could result in a failure to achieve one or more of the performance 

objectives of 10 CFR 74.3, and the program capabilities of 10 CFR 74.41(c). A licensee’s 

development of its critical MC&A procedures, and any changes later made to them, should 

involve technical review by cognizant licensee personnel, be approved by line management 
11 NUREG-2159

directly affected, and also be approved by a level of management above the level responsible 

for executing the procedures. The MC&A plan should contain a definitive statement that the 

procedures will be followed. This set of critical MC&A procedures should, at a minimum, include 

procedures addressing the inventory control requirements listed in 10 CFR 74.43(c)(1)-(10),

regardless of which facility organizational group is responsible for the particular MC&A system 

being addressed. Additionally, MC&A procedures should address:

• accountability record system

• sampling and measurements

• measurement control system

• item control system

• physical inventories

• investigation and resolution of loss indicators

• determination of SEID, active inventory, and inventory difference

• providing information to aid in investigations

• MC&A recordkeeping 

• independent assessment of the effectiveness of the MC&A program

• tamper-safing

• designation of material balance areas (MBAs) and item control areas (ICAs) and 

custodial responsibilities

3.4 Training and Qualification Requirements

This section of the MC&A plan should describe the training programs to be established and 

maintained to provide qualified personnel and to provide for the continuing level of qualification 

with respect to personnel assigned to MC&A responsibilities. Training procedures and 

qualification criteria should be discussed in definitive statements. Minimum qualification 

requirements should be stated for each key MC&A position.

3.5 MC&A Program Description

The length of this section and its level of detail will depend on the information provided in the 

previous sections of this chapter. The overall MC&A organization should be described in a way

that explains how the general performance objectives of 10 CFR 74.3 and the capabilities of 

10 CFR 74.41(c) will be effectively achieved.

The individual who has responsibility for each of the following MC&A-related functions should be 

specified by title:

• overall MC&A program management (Note: This individual should have no major 

responsibilities not related to MC&A.)

• measurements (Note: Responsibility may be divided on the basis of type of 

measurements (e.g., analytical laboratory measurements, NDA measurements, bulk 

measurements, and sampling))

• measurement control

• statistics
NUREG-2159 12

• accountability records

• item control

• physical inventories

• custodial responsibilities (e.g., SNM storage and movement controls)

• investigation and resolution of indicators that suggest possible loss of SNM

• receiving and shipping of SNM

• analytical laboratories

• MC&A recordkeeping system and controls

The MC&A program description should include a description of the policies, instructions, 

procedures, duties, responsibilities, and delegation of authority in sufficient detail to 

demonstrate the separation of duties or overchecks built into the MC&A program..

3.6 Material Control Boundaries

This section of the MC&A plan should describe how the licensee establishes various material 

control boundaries to minimize the occurrence of, and facilitate resolution of, MC&A anomalies, 

such as IDs, missing items of SNM, and potential theft or diversion of SNM.

The MC&A plan should describe the establishment of MBAs and ICAs because they are the 

basis for the control and accounting for all nuclear material in the facility. An MBA or ICA should 

correlate to physical or administrative boundaries and monitored locations. The MBA or ICA 

should be designed to limit losses to a specific area, (i.e., the MBA should not be so large that it 

cannot localize inventory or process differences to a manageable level). Materials transferred 

into and out of an MBA or ICA must have quantitative measurements, as specified in the MBA 

and ICA definitions in 10 CFR 74.4, “Definitions.”

The MC&A plan should describe roles and responsibilities of nuclear material custodians for 

MBAs and ICAs. The material custodian should have direct interaction with the MC&A 

organization and should be located within the physical operations area. Custodians who are 

responsible for more than one MBA or ICA should not have the ability to make material transfers 

between MBAs or ICAs under their direct control.

3.7 Commitments and Acceptance Criteria

In its MC&A plan, the applicant or licensee should provide definitive commitments that adhere to 

the regulatory requirements and meet acceptance criteria applicable to management structure. 

A finding that the licensee’s MC&A plan for management structure is acceptable and in 

accordance with the internal control requirements of 74.43(b)(1) through (4) will be based on, 

but not limited to, the following acceptance criteria:

• The authorship, approval authorizations, and effective dates of MC&A policies and 

procedures will be documented, and will involve appropriate management and technical 

staff.
13 NUREG-2159

• The responsibilities and authorities for each position assigned a function having a 

significant impact on SNM control and accounting (including all positions authorized to 

control SNM movement, generate source data, define or implement measurement 

control requirements, and conduct data analysis) are clearly defined in a written position 

description that spells out the responsibilities for that position.

• The qualifications and experience required for each position assigned an SNM control 

and accounting function will be sufficient to permit adequate performance of the duties 

required of that position.

• The descriptions of the management structure and assignment of duties and authorities 

show that those responsible for each MC&A function will have sufficient authority to 

perform the function in the intended manner.

• The MC&A organization is separate from the production organization and also separate 

from organizations that generate source data, if practical; otherwise, independence of 

the functions is attained by suitable controls and overchecks.

• The responsibility for MC&A program management is designated to an individual at an 

organizational level sufficient to assure independence of action and objectiveness of 

decisions.

• No two key MC&A functions are assigned to the same person unless sufficient checks 

and balances are provided. As a consequence of this criterion:

o Individuals who generate source data, such as performing measurements or 

perform shipping and receiving activities do not perform any accounting or 

record control functions unless suitable overchecks are provided to prevent 

falsification of both source data and accounting records

o No individual has the sole authority to overcheck, evaluate performance, or 

audit information for which he or she is responsible

• Sufficient checks and balances are incorporated to detect falsification of data and 

reports that could conceal theft or diversion of SNM by: a single individual, including an 

employee in any position; and collusion between two individuals, one or both of whom

have access to SNM.

• The responsibility for each MC&A function is assigned to a specific position in the 

organization, and the organization is structured in a way that the key functions are 

separated or overcheck one another. The position descriptions are available in writing to 

the personnel affected.

• All current critical MC&A procedures are made easily accessible to all affected 

individuals, and are maintained to show for each procedure for the following:

• the revision number

• date issued

• person who prepared the procedure

• person approved the procedure (as indicated by signature and date signed)
NUREG-2159 14

• Management policies are established, documented, and maintained to ensure that all 

critical MC&A procedures are adhered to, including measurement procedures used for 

accountability purposes.
15 NUREG-2159

4. MEASUREMENTS

4.0 Regulatory Intent

The intent of the Title 10 Code of Federal Regulations(10 CFR) 74.45(b) measurement 

capability requirements is to ensure licensees establish, maintain, and use a system of 

measurements to ensure that all quantities of special nuclear material (SNM) (both element and 

fissile isotope) in their accounting records are based on reliable measurements. Generally, 

licensees should follow written procedures for measuring SNM. These procedures should 

incorporate the use of reference standards, instrument calibration, and sampling. Licensees 

should ensure that procedures exist for all measurement systems to be used at the facility. 

Specifically, 10 CFR 74.45(b)(1) requires licensees to establish, maintain, and use a

measurement program that is applicable to all SNM received, produced, transferred between 

internal control areas, on inventory, or shipped, discarded, or otherwise removed from inventory. 

The U.S. Nuclear Regulatory Commission (NRC) has four stated exceptions to this requirement:

(1) sealed sources that have each been determined by other means to contain less than 

10 grams of uranium-235 (235U), uranium-233 (233U), or plutonium

(2) samples that have either been received, transferred between internal control areas, or 

that are on inventory and that have each been determined by other means to contain 

less than 10 grams of 235U, 233U, or plutonium

(3) receipt of sealed sources, of any quantity, that were previously manufactured and 

shipped by the licensee, and which are returned to the licensee, provided the unique 

identity and encapsulation integrity have not been compromised and the booked receipt 

quantity equals the previously shipped quantity for the sealed sources in question

(4) heterogeneous scrap that cannot be accurately measured in its as-received form, 

provided such scrap is measured after dissolution within 18 months of receipt (the after 

dissolution measurement must include measurement of both the resulting solution and 

any undissolved residues before any co-mingling with other scrap solutions or residues)

Further, 10 CFR 74.45(b)(2) requires licensees to maintain and follow a program for the 

development and use of written measurement procedures, including the documented review 

and approval of such procedures, and any revisions thereof, before use. Regulations 

in10 CFR 74.45(b)(2) specify that these procedures must cover: (1) preparing or acquiring, 

maintaining, storing, and using reference standards, (2) calibrating measurement systems, 

performing bulk mass and volume measurements, conducting nondestructive assay 

measurements, obtaining samples, and performing laboratory analyses for element 

concentration and fissile isotope abundance, and (3) recording, reviewing, and reporting 

measurements. Section 4.4 provides guidance on measurement procedures below.

4.1 Measurement Points

The material control and accounting (MC&A) plan should identify and describe each 

measurement that is used for accounting purposes. Measurements (1) establish the quantities 

in each custodial area, material balance area (MBA), or item control area (ICA) and in the facility 

as a whole, and (2) contribute to the desired capability to localize losses and to generate and 
NUREG-2159 16

assess alarms. Measurement points or sampling stations should be selected to provide 

quantitative information about material flows and inventories that will permit detection and 

localization of any loss or diversion or to confirm that no theft or diversion has occurred. 

Typically, three functional types of MBAs and ICAs are present: (1) processing, (2) storage, and 

(3) receiving and shipping. 

Typical processing MBAs include: (1) processing areas, (2) decontamination and recovery 

areas, (3) laboratory areas, and (4) feed and product sampling and transfer areas. The NRC 

requires identification and definition of measurement points for processing MBAs because of the 

physical or chemical changes of the nuclear materials that occur in these MBAs. The storage 

and the receiving and shipping areas are typically ICAs. 

4.2 Measurement Systems

The MC&A plan should describe in detail each measurement system used for nuclear material 

accounting purposes. The principal elements and operations involved in the measurement 

systems for MC&A encompass mass (or weight) or volume determination; sampling; chemical 

analyses for element and isotope; and nondestructive assay (NDA). Each measurement 

system also should be defined or identified by its unique set of the following parameters: 

(1) measurement device or equipment used, (2) standards used for calibration, and 

(3) standards used for control. Additionally, for analytical laboratory measurements, the 

following should be identified as well: (1) sampling technique and equipment used, (2) sample 

aliquoting technique, and (3) sample pretreatment methodology. Chapter 5 describes elements 

of the measurement control program (e.g., standards traceable to a national system) used for 

validating and determining control limits, precision, and accuracy levels for each measurement 

system used for accountability.

The MC&A plan should provide descriptions for each measurement system associated with 

bulk, analytical, and NDA measurements, and should identify, where applicable, any other 

measurement systems used for accounting purposes that do not fall within these categories. 

These descriptions should provide sufficient information to demonstrate how the systems are 

implemented to ensure the licensee’s capability to meet the precision and accuracy limits. The 

following sections provide examples of the types of information necessary for selected 

measurement systems.

4.2.1 Bulk Measurement Systems

For each weighing system, the applicant or licensee should specify the type of weighing device, 

the type of container(s) weighed, material within the containers being weighed, capacity of the 

weighing device (e.g., capacity not to exceed X kilograms), range to be used, sensitivity of the 

device (e.g., sensitivity is +/- Y grams), and the calibration frequency. 

For each volume measurement system, the MC&A plan should identify the vessel (e.g., tank, 

column), capacity of the vessel to which the measurement applies (e.g., capacity not to exceed 

X liters), the material being measured, the volume measuring device and instrumentation, the 

sensitivity of each device and system (e.g., sensitivity is +/- Y milliliters), the range of operation 

or calibration (or both), and the calibration frequency. 
17 NUREG-2159

4.2.2 Analytical Measurement Systems

For each analytical measurement system, the MC&A plan should specify the following:

• type of material or chemical compound (e.g., plutonium oxide (PuO2), plutonium metal or 

alloy, PuO2-uranium dioxide (UO2), uranium hexafluoride (UF6), uranium alloy, UO2, 

uranyl nitrate solution) being sampled and measured

• sampling technique(s)

• sample handling (i.e., pre-analysis sample storage and treatment)

• analytical method used

• characteristics measured (e.g., grams of uranium or plutonium per gram sample, or 235U 

or 233U isotopic concentration)

• measurement interferences

• expected measurement uncertainty

• types of calibration standard(s) and calibration frequency

4.2.3 NDA Measurement Systems

For each NDA measurement system, the MC&A plan should identify the following:

• the NDA equipment package (i.e., type and size of detector and type of associated 

electronics and computer interface, as appropriate)

• the type of container measured

• SNM material type within container

• sampling technique(s), if applicable

• attribute measured

• measurement configuration (including source to detector distance)

• calculation method

• expected measurement uncertainties
NUREG-2159 18

4.2.4 Other Measurement Systems

If applicable, the MC&A plan also should identify any other measurement systems used for 

accounting purposes that do not fall within the three categories covered by subsections 4.2.1, 

4.2.2, and 4.2.3. 

4.3 Measurement Uncertainties

Licensees should provide the expected measurement uncertainties of the described 

measurement systems. Variance components for calibration, sampling, random, and 

systematic error for each measurement system should be stated. Licensees should clearly 

identify the units in which the errors are expressed.

4.4 Measurement Procedures

The licensee or applicant should define how it ensures that it establishes, approves, and 

maintains measurement procedures (i.e., methods). It can accomplished this by (1) making a 

definitive statement it establishes and maintains an approved measurement procedures 

(i.e., method) manual, or set of approved manuals, (2) stating which organizational units are 

responsible for the preparation, revision, and approval of measurement procedures, and 

(3) defining the requirements for periodic review of the procedures.

Licensees and applicants should make a clear statement defining how their facilities ensure that 

a measurement procedure cannot be used for accountability purposes without documented 

approval. Each procedure should be approved by the overall MC&A manager and by the 

manager of the organizational unit responsible for performing the measurement. Measurement 

procedures also should be approved by the measurement control program manager.

The MC&A plan should provide a definitive statement that all SNM quantities in the material 

accounting records are based on measured values and that measurement systems are 

maintained for the measurement of SNM associated with the following:

• additions to inventory (e.g., receipts)

• removals from inventory (e.g., shipments and measured discards)

• material on ending inventory

For receipt of material, the licensee may use shipper's measured values rather than its own 

measurements, provided that (1)a shipper–receiver comparison, based on attributes or 

confirmatory measurements, shows no significant shipper–receiver difference (SRD) (as defined 

by 10 CFR 74.43(b)(7)), (2) in the case of a significant difference between shipper and receiver, 

no significant difference exists between the shipper's value and the umpire value used to 

resolve the difference, or (3) the material in question is exempted from shipper–receiver 

comparison requirements (e.g., sealed sources and samples). However, when booking 

shipper's values, a licensee should use the shipper's measurement uncertainty when 

determining standard error of the inventory differences (SEID).

4.5 Scrap Control

Heterogeneous scrap that cannot be accurately measured in its received form need not be 

measured until after dissolution within 18 calendar months of receipt. In accordance with 

regulations in 10 CFR 74.45(b)(1)(iv), the after-dissolution measurement must include 
19 NUREG-2159

measurement of both the resulting solution and any undissolved residues before any 

co-mingling with other scrap solutions or residues. In the meantime, a licensee should use the 

shipper’s value or an appropriate factor-based value for inventory purposes.

4.6 Commitments and Acceptance Criteria

In its MC&A plan, the applicant or licensee should provide definitive commitments that adhere to 

the regulatory requirements and meet the acceptance criteria applicable to measurements. For 

the NRC to find that a licensee’s MC&A plan for assuring that all quantities of SNM are based 

on reliable measurements is acceptable and in accordance with 10 CFR 74.45(b), its decision 

will be based on, but not limited to, the following acceptance criteria:

• A program of measurement procedures and methods is maintained for all SNM receipts, 

removals, and inventory items, and the licensee has based all quantities of SNM in the 

material accounting records on measured values.

• The licensee will identify measurement systems that are the key contributors to the total 

measurement standard error. It will review the list annually and update it as necessary. 

These are considered key measurement systems, and their standard deviations should 

be monitored and controlled by the measurement control program.

• A basic description or summary of each key measurement system that is used to 

generate SNM values for accountability purposes is provided. A measurement system is 

defined as any instrument or device, or combination of devices, used to derive (1) an 

element concentration, (2) an isotope quantity, (3) an 235U enrichment or isotopic 

distribution, (4) a bulk material mass (weight), or (5) a bulk material volume. This 

system can be characterized by its random and systematic error components.

• The set of key measurement systems, based on recent (or anticipated) measurement 

control data and modes of process operations, is expected to account for at least 

90 percent of the total measurement uncertainty contribution to the SEID.

• The recalibration frequency for each measurement system is compatible with its 

expected stability. Recalibrations for all measurement systems should be performed at 

frequencies compatible with widely established, or licensee demonstrated, stability for 

each particular system.

• All calibrations are made with the use of primary standards or primary reference 

materials (certified and issued by the National Institute of Standards and Technology,

New Brunswick Laboratory, or equivalent organization) or with reference standards 

traceable to primary standards. The standards used for calibrations need not be 

representative of the unknowns to be measured by the system, unless they are to be 

regarded as a bias-free system that is calibrated during each time of use, in which case 

the calibrations standards must be representative.

When determining an SNM quantity by weighing, sampling, and analyses, the net weight of 

material in each item within a uniform material batch (or lot), such as blended plutonium oxide 

PuO2 or UO2 powder, plutonium metal, or sintered UO2 pellets must be determined by direct 

mass measurement. However, the element or isotope concentrations for the batch need not be 

determined for each container, but instead may be derived by sampling procedures, including:
NUREG-2159 20

• Analysis of composite samples or measurements of representative items, objects, or 

samples selected by statistical sampling

• Use of concentration or enrichment factors determined from historical averages, 

controlled input specifications values, or empirical relationships where such values or 

relationships are periodically tested, their uncertainties or bounds have been determined 

to be within 2 percent of the factor value, and where diversions with material substitution 

are improbable.
21 NUREG-2159

5. MEASUREMENT CONTROL SYSTEM

5.0 Regulatory Intent

The intent of the measurement control requirements in Title 10 of the Code of Federal 

Regulations (10 CFR) 74.45(c) is to ensure that measurement systems (described in Chapter 4) 

used to establish special nuclear material (SNM) accountability quantities be controlled by a 

formal measurement control system that results in a total measurement standard error within 

0.125 percent of the active inventory quantity. In terms of a 95 percent confidence level, twice 

the standard error associated with a material balance total material control and accounting

(MC&A) measurement uncertainty (for uranium-235 (235U), plutonium, or uranium-233(233U)) 

must be less than 0.25 percent of the active inventory. The U.S. Nuclear Regulatory 

Commission (NRC) also intends that the system provide bias estimates for licensees to use for 

adjusting inventory difference (ID) results and correcting shipper-receiver measurements for 

significant measurement biases.

5.1 Organization and Management

The organization and management of the measurement control system should be described in 

sufficient detail to show how licensees assign the measurement quality assurance function and 

how independence from the analytical laboratory and other units performing either sample 

taking or measurements is maintained. The measurement control system manager should be at 

a management level that is sufficiently high to ensure objectivity and independence of action. 

Thus, the measurement control system manager could either report directly to the overall MC&A 

manager or, if in a different organizational unit, be on the same level as the MC&A manager.

The licensee's measurement control system should be properly managed to ensure adequate 

calibration frequencies, sufficient control of biases, and sufficient measurement precision to 

achieve the capabilities required by 10 CFR 74.45(c).

5.1.1 Functional Relationships

The relationship and coordination between the measurement control system manager, the 

analytical laboratory, and other measurement performing groups needs to be clearly defined. 

Adequate assurance should be provided so that the measurement control system manager has 

the authority to enforce all applicable measurement control requirements.

5.1.2 Procedures

The measurement control system procedures should be established and maintained in a 

manual that the licensee keeps current and readily available. This manual should contain all the 

currently applicable written procedures on measurement control and measurement quality 

assurance. The licensee should specify who has responsibility for preparation, revision, and 

approval of manual procedures. Individual measurement control procedures should have 

documented approval by the measurement control system manager. The procedures should 

address the following:

• calibration frequencies and methods

• standards used for calibration (i.e., description and storage controls)
NUREG-2159 22

• standards used for control (i.e., method of obtaining or preparation, and traceability)

• control standard measurements

• replicate sampling and replicate measurements

• verification of process control instrumentation through comparison with other process 

instruments

• generation and collection of control data

• control limits and control responses

• recordkeeping controls and requirements

5.1.3 Contractor Program Audits and Reviews

If measurement services are provided by an outside contractor or offsite laboratory, the review 

program used to monitor the offsite measurements must be described in accordance with 

10 CFR 74.45(c)(2). The licensee should ensure that the contractor or offsite laboratory 

performing such reviews has an acceptable measurement control system to the extent that use 

of the contractor's measurements will not compromise the licensee's ability to meet any 

measurement or measurement control requirement in its MC&A plan. An initial review of the 

contractor's measurement control system should be conducted before licensee use of 

measurements performed by the contractor or offsite laboratory.

All contractor or offsite laboratory assessment findings and recommendations should be 

documented and submitted to both the measurement control system manager and the overall 

MC&A manager within 30 days of completion of the review. The two managers should arrive at 

an agreement on corrective actions to take based on their evaluation of the report, and they 

should transmit these findings to the contractor or offsite laboratory in writing. The licensee 

should not use measurements performed by such contractors or offsite laboratories until it has

verified that the corrective actions have been instituted.

The persons who conduct a contractor review need not be employed by the licensee; but they 

should not be employed by, or in any way associated with, the contractor or offsite laboratory so 

that the independence of the conclusions may be maintained.

5.2 Calibrations

The MC&A plan should summarize the licensee's calibration program and confirm that the 

licensee has written procedures covering the following topics:

• calibration frequency for each measurement device or system

• identification of the standards used for calibration of each measurement device or 

system
23 NUREG-2159

• protection and control of standards used to calibrate measurement systems to maintain 

the validity of their certified or assigned values

• the range of calibration for each measurement device or system and the minimum 

number of calibration runs (observations) needed to establish a calibration

Unlike control standards, standards used for calibrating measurement systems need not be 

representative of the process material or items to be measured by the calibrated device or 

system. If practical, the standard used during the calibration process should be subjected to all 

the steps involved in the measurement process that the process unknowns are subjected to 

(e.g., sample pretreatment), but this need not always be the case. It is the primary 

measurement device, not necessarily the entire measurement system, that needs to be 

calibrated, especially when the primary measurement device is common to two or more 

measurement systems. 

For example, the Davies & Gray titrimetric method is often used to analyze samples for uranium 

concentration of two or more different material types (e.g., UF6, UO2, uranyl nitrate hexahydrate

solutions). In this case, more than one measurement system is involved because different 

sampling and sample pretreatment methods and different control standards are used. The 

potassium dichromate (K2Cr2O7) titrant, however, is common to the systems; thus, the titrant is 

what is calibrated (or standardized) with a primary reference material such as certified K2Cr2O7, 

certified U3O8 or certified uranium metal.

In the case of nonconsumable standards used to calibrate measurement systems (e.g., weight 

standards), the frequency of recertification of assigned values should be specified. The 

recertification frequency should depend on how often the standards are handled, the standard's 

stability, and the adequacy of the controls used to maintain the integrity of the standards. The 

NRC usually considers biennial recertification of such standards to be acceptable. 

The MC&A plan should contain a definitive statement that no SNM accountability value is based 

on a measurement that falls outside the range of calibration. The MC&A plan also should 

identify those measurement systems that are point-calibrated. A point-calibrated measurement 

system is one in which the following are true:

• The entire measurement system is calibrated with a standard or set of standards that is 

representative of the process unknowns that the system measures. That is, the 

representative calibration standard(s) undergoes all the measurement steps, and in the 

same manner, that the unknowns undergo.

• One or more calibration standards are processed and measured along with each 

unknown or set of unknowns measured. That is, the system measures both the 

standard(s) and unknown(s) during the same general time interval, with the same 

individual measuring methods.

• The measurement values assigned to the process unknowns are derived from the 

measurement response observed for the standard(s) that was measured along with the 

unknown(s).

• The measurement response for each unknown should fall within plus or minus 

10 percent of the response for a standard measured at the same time as the unknown, 
NUREG-2159 24

or, as in the case of a low concentration unknown, the difference between the unknown's 

response and the standard's response should be less than four times the standard 

deviation associated with the standard's response.

5.3 Control Standards

For those measurement systems that are not point-calibrated, a defined method for the periodic 

measurement of control standards should be established and followed. Control standard 

measurements serve the dual purpose of (1) monitoring the stability of a previously determined 

calibration factor, and (2) estimating the average system bias over a period of time (e.g., an 

inventory period). Licensees need to specify the minimum total number of control standard 

measurements during the time period, as well as the typical frequency, for each measurement 

system. Generally speaking, for each key measurement system, a minimum of two control 

standard measurements should be made during each week that the system is in use. For those 

key systems that are used infrequently during a given material balance period, more than two 

control standard measurements per week of system use may be necessary to provide a 

measurement system performance that is controlled such that the SEID will not exceed 

0.125 percent of the active inventory.

The measurement control system should produce data that are representative of actual 

operating conditions and all errors that impact ID. The larger uncertainty estimates that 

collectively contribute 90 percent or more to the SEID estimator will be based on a minimum of 

15 standard or replicate process material measurements, as appropriate.

Included within the set of key measurement systems should be any system used to measure an 

SNM quantity (during an inventory period) greater than 25 percent of the active inventory, 

regardless of its contribution to SEID. The minimum number of control standard measurements 

for any system used to measure an SNM quantity (during an inventory period) greater than 

25 percent of the active inventory should be determined based on the system’s characteristics, 

use, and frequency of control standard measurements. In any case, it should be greater than 

eight (i.e., the minimum number of control standard measurements may need to be set at a 

higher number than eight to ensure proper performance). The minimum number of control 

standard measurements is eight for nonkey measurement systems that measure from 10 to 

25 percent of the active inventory, and the minimum number of control standard measurements 

can be reduced to four, respectively, for those nonkey systems used to measure less than 

10 percent of the active inventory quantity.

Key measurement systems for the current inventory period are any set of designated 

measurement systems (of the licensee’s choosing) that, based on the most recent previous 

period, account for at least 90 percent of the total measurement variance contribution to SEID. 

Included within the set of key measurement systems should be any system used to measure an 

SNM quantity (during an inventory period) greater than 25 percent of the active inventory, 

regardless of its contribution to SEID. 

Control standards should be representative of the process material or items being measured. 

To be representative, the standards need not always be identical to the process unknowns; but 

any constituent of the process material, or any factor associated with a process item, that 

produces a bias effect on the measurement should be present to the same degree in the control 

standards. For scales used to weigh very large items, the control standard weights should be 

artifact standards (e.g., both empty and full containers) of certified mass to avoid a bias effect 

caused by buoyancy or point loading.
25 NUREG-2159

For each measurement system that is not point-calibrated, the control standards licensees 

should use for control standard measurements should be identified and described. Along with 

material composition and matrix factors, biases also can be induced by changes in (among 

other things) temperature, humidity, line voltage, and background radiation. Biases also can be 

operator or analyst induced. Therefore, the scheduling of control standard measurements 

should be based on the following considerations:

• Does the variation between analysts or operators need to be considered and monitored?

• Can environmental variables contribute to measurement bias?

• Is bias likely to vary with respect to the time of day?

• Is a particular bias likely to be long-term, short-term, or cyclic in nature?

• Is bias a function of the process measurement values over the range of calibration 

(i.e., is the relative percent bias nonuniform over the range of calibration)?

• What controls or procedures are needed to ensure that sampling or aliquoting of the 

control standard is representative of the sampling or aliquoting of the process material?

• To estimate the bias for each measurement system, how much alike—in terms of 

chemical composition, uranium concentration, density, homogeneity, and impurity 

content—should the control standards be relative to the process unknowns?

5.4 Replicate Sampling

For systems involving sampling, duplicate measurements performed on single samples or 

measurements of replicate samples are necessary to estimate the combined analytical plus 

sampling random error. For nonsampling measurement systems such as nondestructive 

assay(NDA) and weight measurement systems, the random measurement variance component 

can be derived either from (1) replicate measurements performed on process items, or (2) the 

data generated from the measurement of control standards.

The licensee should ensure that replicate samples are independent of one another. The 

number of replicate samples measured for each analytical measurement system should be 

described. The number of replicate samples measured for each analytical measurement 

system during an inventory period should be equal to at least one of the following: 

(1) 100 percent of the accountability batches sampled (when less than 15 batches) 

(2) the greater of 15 samples or 15 percent of the accountability batches sampled 

(3) 50 samples (when 15 percent of the batches is greater than 50) 
NUREG-2159 26

For nonkey analytical measurement systems, the minimum number of replicate samples to be 

measured during an inventory period should be equal to one of the following:

(4) 100 percent of the accountability batches sampled (when less than eight batches)

(5) the greater of eight samples or 10 percent of the accountability batches sampled

(6) 25 samples (when 10 percent of the batches is greater than 25)

For each measurement system involving sampling and analysis, the MC&A plan should indicate 

(1) how many samples are taken and measured for each accountability batch measurement, 

and (2) how many analyses are performed on each accountability sample. If two or more 

samples are used and the licensee performs one or more analyses per sample for each 

accountability batch measurement, replicate requirements are automatically met. If, however, 

one sample per batch is normally used for accountability purposes, the replicate program should 

include a periodic taking of a second (i.e., replicate) sample. 

For NDA and mass (weight) measurement systems, replicate data can be obtained either from 

the repeat measurements on production items or by using the data generated from the control 

standard program. That is, each consecutive pair of control standard measurements (for a 

given NDA or mass system) can be regarded as a replicate pair. The minimum number of 

replicate measurements performed during an inventory period for a given key NDA or mass 

system should be as given in items 3.3 (1), (2), or (3), above, except that the numbers or 

percentages are in terms of items measured, rather than batches sampled. Likewise, for 

nonkey NDA and mass measurement systems, the minimum number of replicate 

measurements should be as given in items 3.3 (4), (5), or (6) above. 

The scatter in the repeat measurements is used to estimate the random error variance using a 

statistical technique known as the one-way analysis of variance. (The NRC recommends the 

statistical methods described in “Statistical Methods for Nuclear Material Management,”

NUREG/CR-4604, for satisfying the statistical requirements of 10 CFR 74.45, “Measurements 

and Measurement Control”; see also Chapter 6 of this document.) Replication not only 

improves the precision of results obtained from the statistical analysis of the measurement data, 

it also can detect gross errors in the data. 

5.5 Control Limits

The licensee should establish both 0.05 (warning) and 0.001 (out-of-control) limits to use for 

control standard measurements for those measurement systems used for nuclear material 

accountability in accordance with 10 CFR 74.45(c)(10). Out-of-control limits are also to be used

for replicate measurements and measurement of replicate samples. However, warning limits 

are optional for the replicate program. For point-calibrated systems, the assigned value of the 

standard(s) measured along with the unknown(s) is assumed to be valid. If the standard's true 

value could change because of factors such as evaporation, moisture pickup, or oxidation, the 

value of the standard should be checked periodically. Therefore, control limits for the 

verification measurements associated with such standards should be established. This is 

especially true for those point-calibrated systems that use a single standard, or aliquots from a 

single standard, over any extended period of time. 

When a system generates a control measurement that falls beyond an out-of-control limit, the 

system should not be used for accounting purposes until it has been brought back into control 

(i.e., within the upper and lower warning limit). 
27 NUREG-2159

Control limits should be recalculated at a predetermined frequency and modified, if required. 

The MC&A plan should clearly explain how control limits are established and the frequency for 

redetermining them.

5.5.1 Measurement Control Data Analysis

Licensees should plot measurement control data, such as control standard measurement 

results, and the differences between measurement values of replicate pairs for generation of 

control charts. All control charts should be reviewed at least once every 2 weeks unless a 

measurement system was not used during that period. The review should assess the frequency 

of control data exceeding either the warning or the out-of-control limits and also provide an 

evaluation for any significant trends.

5.5.2 Response Actions

Either the analyst or the operator performing a control measurement or his or her supervisor 

should have the responsibility for promptly reporting any control measurement that exceeds an 

out-of-control limit. Such reporting should be made to the measurement control program 

manager (or his or her designee), who should have the responsibility and authority to carry out 

or direct the necessary response and corrective actions.

Minimum response and minimum corrective action requirements should be clearly defined. In 

addition, the measurement control manager (or his or her designee) should be responsible for, 

and have the authority for, determining and executing additional response and corrective 

actions, as deemed appropriate.

The minimum response to a reported incident of a control measurement exceeding an 

out-of-control limit should consist of the following:

(1) Verifying that the measurement system in question has been taken out of service with 

respect to accountability measurements.

(2) Documenting the occurrence of the event.

(3) Performing at least two additional control measurements.

(4) Performing additional control measurements, if results of item 3 do not show the system 

to be back in control, using a different control standard or different replicate sample (as 

appropriate), recalibrating the measurement system, or making any necessary system 

repairs.

(5) Reviewing measurements performed on the system in question since the last incontrol 

run to determine if there is a need to remeasure any items.

For those measurement systems that make a significant contribution to the SEID, the response 

to an out-of-control condition also should include the remeasurement of any samples (or items) 

the licensee measured before the out-of-control condition but after the last within-control 

measurement. The validity of the previous measurements may be established without a 

complete remeasurement of all the samples (or items) involved if remeasurement on a “last in, 

first out” basis is used. That is, the last sample (or item) measured before the out-of-control 

measurement should be the first to be re-measured, and review should continue in reverse 
NUREG-2159 28

order until two consecutive re-measurements are found to be in agreement with their initial 

measurement at the 95 percent confidence level.

5.6 Commitments and Acceptance Criteria

In its MC&A plan, the applicant or licensee should provide definitive commitments that adhere to 

the regulatory requirements and meet the acceptance criteria applicable to the measurement 

control program. A finding that the licensee’s MC&A plan for maintaining measurement quality 

and estimating measurement uncertainty values is acceptable and in accordance with 

10 CFR 74.45(c), will be based on, but not limited to, the following acceptance criteria:

• A measurement control system is followed by which all measurement biases associated 

with key measurement systems are estimated and any significant biases are eliminated 

from ID values and shipper or receiver differences.

• The measurement control system produces data that are representative of actual 

operating conditions and all errors that impact the ID estimate. The larger uncertainty 

estimates that collectively contribute 90 percent or more to the SEID will be based on a 

minimum of 15 standard or replicate process material measurements, as appropriate.

• The method to be used for estimating the SEID for the typical material balance, as 

shown in the annex, meets the following criteria:

o All reasonable and probable sources of measurement error for the key 

measurement systems affecting IDs are included.

o The selection of the key measurements whose variances are to be included in 

calculating the standard error is justified by an analysis of the relative magnitudes 

of the variance components of a typical ID and their comparative effect on the 

SEID.

o Any measurement error standard deviations not actually determined by the 

measurement control program are shown to be reasonable, either by comparison 

with published state-of-the-art measurement performance in similar applications: 

(see such sources as NUREG-2078,

1 “Handbook of Nuclear Safeguards 

Measurement Methods,” dated September 1983, or with records of past 

performance data from the licensee’s facility. Records showing these data must 

be available to the NRC.

o The total measurement uncertainty is controlled so that the SEID for each 

material balance period will be less than 0.125 percent of the active inventory for 

the material balance period. The calculation of the measurement contributions to 

SEID are traceable to the appropriate measurement error data and to the 

calibration standards used.

 1 For example, NUREG-2078 cites a performance relative standard deviations of 0.65 percent for 

random error and 0.018 percent for systematic error using the Davies and Gray titrimetric method for 

measuring TRIGA alloy process material. For the determination of plutonium (Pu) by redox (oxidationreduction reactions) titremetry, the relative standard deviations were 0.38 percent for random error and 

0.038 percent for systematic error in the measurement of Pu metal.
29 NUREG-2159

o The calculation of the SEID is performed in accordance with a recognized error 

propagation method. Such methods have been published in the recommended 

NUREG/CR-4604, Statistical Methods for Nuclear Material Management, dated

December1988, as well as in TID-26298, “Statistical Methods in Nuclear 

Materials Control,” 1973, and the IAEA statistics handbook (1989).

o Program data on the performance of each measurement system is used during 

the current material balance period, including estimates of bias, variance 

components for calibration, sampling, and replicate measurements (of the same 

sample).

• The approach used for bounding the total measurement standard error for a typical 

material balance period meets the following criteria:

o All reasonable and probable sources of measurement error affecting inventory 

difference are included.

o Any assumed measurement standard deviations are shown to be reasonable. 

They may be shown to be reasonable by comparison to either records of the 

licensee’s past performance data or to published measurement performance in 

similar applications. 

o The calculation of the total measurement standard error is performed in 

accordance with a recognized error propagation method. Such methods have 

been published in the recommended NUREG/CR-4604 (1988), as well as in 

TID-26298 (1973) and the IAEA statistics handbook (1989).

• The measurement systems have adequate calibration frequencies, sufficient control of 

biases, and sufficiently small standard deviations to achieve the requirements of 

10 CFR 74.41(c). A measurement control program is used—by both in-house activities 

and any contractor who performs MC&A measurement services for the licensee—to 

ensure that the quality of the measurements is maintained on a level consistent with the 

NRC requirements.

• The licensee should confirm that the accountability measurements provided by a 

contractor are controlled by a measurement control program, and the licensee should 

confirm that the contractor's measurement control program is adequate by conducting 

audit and assessment reviews of the contractor’s program at intervals not to exceed 

18 months.

31 NUREG-2159

6. STATISTICS

6.0 Regulatory Intent

Proper use of statistics is important to ensuring that the regulatory requirements in Title 10 of 

the Code of Federal Regulations (10 CFR) 74.41 (“Nuclear Material Control and Accounting for 

Special Nuclear Material of Moderate Strategic Significance”), 10 CFR 74.43 ( “Internal 

Controls, Inventory, and Records,” and 10 CFR 74.45 (“Measurements and Measurement 

Control”),are met. An effective statistical program will ensure measurement systems perform 

within control limits, measurement uncertainties are calculated and propagated, the

inventory difference (ID) and standard error of the inventory difference (SEID) are properly 

determined, and significant shipper-receiver differences are identified. For example, 

10 CFR 74.43(c)(8)(i) requires licensees to calculate the ID and SEID for the material balance 

period terminated by each physical inventory. Proper use of statistics is important to correctly 

propagate the uncertainties from all measurements into an accurate SEID value.

6.1 Determination of Measurement Uncertainties

To achieve the objectives and capabilities of 10 CFR 74.3 and 74.41, each licensee or applicant 

should institute a statistical program that evaluates the measurement control and accounting 

(MC&A) data to ensure that (1) the measurement data are analyzed in a rigorous manner and 

(2) statistical tests and inferences concerning the status of the nuclear material possessed are 

appropriately tested. The NRC sponsored the development of a comprehensive reference that 

specifically addresses the statistical treatment of MC&A data. The statistical methods described 

in NUREG/CR-4604, as well as in TID-26298 and the IAEA statistics handbook (1989), are 

recommended by the NRC for satisfying the statistical requirements of 10 CFR 74.41, 74.43,

and 74.45. 

The MC&A plan should cover the following:

• Contain a detailed discussion of the procedures and methodologies for estimating 

measurement variance components.

• Discuss how biases are determined and how bias corrections are applied, including:

o how often biases are estimated

o how the effect of the bias on the measured quantity of material in an item is 

determined

o when and how bias corrections to items are made

o how their effect on ID is determined

o when and how bias corrections are applied to the ID

• Describe the procedure and means for determining active inventory.

• Provide all relevant information regarding the determination of the SEID.

• Specify the methodology for determining ID threshold values as required by 10 CFR 

74.43 (c)(8)(iii). (See Chapter 7 for additional information on inventory difference limits 

and response actions.)
NUREG-2159 32

6.2 Determination of Standard Error of the Inventory Difference

As defined in 10 CFR 74.4, the “standard error of inventory difference” means the standard 

deviation of an inventory difference that takes into account all measurement error contributions 

to the components of the ID. For special nuclear material (SNM) of moderate strategic 

significance, licensees should not include nonmeasurement contributors to the ID in the SEID 

calculation. Including only measurement uncertainty, SEID (for either uranium, 235U, plutonium 

or 233U, as applicable) can be expressed as follows:

SEID = 

where

k = number of measurement systems

Gi = total grams uranium (or 235U) measured during inventory period by 

measurement system i

(σi)s = systematic error standard deviation for measurement system i

(σi)r = random error standard deviation for measurement system i

n = number of batches (items) measured by measurement system i

In theory, SEID provides the uncertainty, at the 67 percent confidence level, of the ID estimate.

The MC&A plan should provide all relevant information on the determination of SEID. 

Licensees should also commit to having at least two individuals independently verify the 

accuracy of the SEID calculation for each total plant material balance. If the SEID value is 

calculated by a computer, the verification by two or more persons involves a checking for 

correctness of the input data used by the computer to calculate SEID.

6.3 Bias Corrections

From a statistical perspective, biases that are not statistically significant (at the 95 percent 

confidence level) should never be applied as adjustments (corrections) to the accounting 

records. To obtain the best estimate of the true inventory difference value, such insignificant 

biases should be applied as a nonaccounting adjustments to the initially calculated inventory 

difference (as obtained from the ID equation: ID = BI + A - R - EI). Such practice is not deemed 

necessary, however, for material balances pertaining to SNM of moderate strategic significance, 

and is thus optional.

For biases that are statistically significant (at the 95 percent confidence level), it is common 

practice to adjust the accounting values for individual items if the bias effect (as grams element 

and grams isotope) on the item is more than the rounding error for that item, and if less than the 

rounding error, to apply the bias as a nonaccounting adjustment to the ID. Under a 

well-designed and well-managed measurement control system, bias corrections to the 

accounting records should seldom, if ever, be necessary under the above mentioned approach. 

Although the effect on an individual item from a statistically significant bias should be negligible, 

the effect of that bias across hundreds or thousands of items (whose SNM values were derived 

from the biased measurement system) could have a very significant impact on the ID value.

Nevertheless, in view of the very large quantity of SNM of moderate strategic significance that is 

of a safeguards significance, the NRC acceptance criteria does not normally call for applying 
33 NUREG-2159

bias corrections to either the accounting records or as an adjustment to ID unless the effect of a 

single significant bias or the net sum of all significant biases is unusually large.

As a minimum, to meet NRC acceptance criteria, a bias correction for a single key 

measurement system should be considered “significant,” and thus applied either as corrections 

to the accounting records or as an adjustment to the inventory difference if (1) such bias is 

statistically significant at the 95 percent confidence level, and (2) either or both of the following 

are also true:

• applying the correction would cause the ID to exceed three times SEID

• the bias is greater than 0.01 percent relative

Additionally, the net algebraic sum (expressed as grams SNM) of all statistically significant 

(95 percent confidence level) biases from key measurement systems not defined as bias-free, 

that have not been applied as a correction or adjustment under either or both condition above is 

considered to be “significant” and is to be applied as a net adjustment to the ID if applying such 

correction would cause the ID to exceed three times the SEID.

35 NUREG-2159

7. PHYSICAL INVENTORIES

7.0 Regulatory Intent

The requirements of Title 10 of the Code of Federal Regulations (10 CFR) 74.43(c)(1)-(10)

pertain to the need to maintain inventory control by conducting periodic physical inventories to 

confirm that a loss, theft, or diversion of a significant quantity of special nuclear material 

(SNM) of moderate strategic significance has not occurred. Licensees are required by 

10 CFR 74.43(c)(7) to conduct physical inventories at intervals not to exceed 9 calendar 

months. The principal method of confirming the presence of SNM is to establish and maintain 

inventory control and to periodically perform a physical inventory and compare it to the book 

(record) inventory. If all SNM is included, the expected difference between the book inventory 

and the physical inventory is zero plus or minus the measurement uncertainty associated with 

both the physical and book inventories. In any actual case, the size of the inventory difference 

(ID) and its uncertainty depends on measurement errors, as well as on various 

nonmeasurement contributors, such as recording errors, unmeasured losses, unmeasured 

residual holdup (see the glossary for definition of “residual holdup”). Licensees must maintain 

and follow the physical inventory procedures and instructions in 10 CFR 74.43(c)(5)-(9). 

7.1 General Description

The applicant or licensee should provide a general description of how physical inventories of 

the plant will be planned, conducted, assessed, and reported. 

The material control and accounting (MC&A) plan should contain a definitive statement that 

physical inventory functions and responsibilities are reviewed comprehensively with the 

involved individuals before the start of each physical inventory. 

The applicant or licensee should generate a book inventory listing, derived from the MC&A 

record system, just before the actual start of each physical inventory. Such listing shall 

include all SNM that the records indicate should be possessed by the licensee at the inventory 

cutoff time. 

The licensee must report inventory difference and related information associated with each 

physical inventory of moderate strategic significance, pursuant to 10 CFR 74.17, “Special 

Nuclear Material Physical Inventory Summary Report.,” on an NRC Form 327. In addition, if 

any material associated with material codes 20-E3 and 20-E4 (i.e., high-enriched uranium), 

70 (

233U), 50 (plutonium), or 83 (plutonium-238) is possessed by the licensee, such material is 

subject to the physical inventory requirements. The licensee should report each material code 

inventory difference and associated information on separate NRC 327 Forms.

7.2 Organization, Procedures, and Schedules

The MC&A plan should explain the makeup and duties of the typical physical inventory 

organization. The individual having responsibility for the coordination of the physical inventory 

effort should be identified by position title. The MC&A plan also should indicate how the 

preparation and modification of inventory procedures are controlled. 

The MC&A plan should contain a definitive statement that specific inventory instructions are 

prepared and issued for each physical inventory.
NUREG-2159 36

7.3 Typical Inventory Composition

Licensees should specify the typical expected in-process inventory within the equipment for 

plutonium, uranium, 235U, and 233U at the time of the physical inventory. A typical composition 

of SNM as stored items at the time of a physical inventory also should be presented. Plants

may be divided into a number of MBAs and ICAs to reflect the functional activities as follows: 

Processing—An MBA in which occurs (1) routine transfers of nuclear material from 

one container to another, (2) changes in chemical assay, or (3) changes in chemical or 

physical form. Various measurements are required to define materials flows through 

the process and to perform physical inventories so that periodic material balances can 

be completed for the MBA. Because these measurements have associated 

uncertainties, a processing MBA will normally have a nonzero ID for each inventory. 

Of the total plant MBAs and ICAs, a relatively small number might be processing 

MBAs. Examples are the decontamination and recovery operations; analytical 

laboratory; and material rebatching, blending, and sampling operations. Physical 

inventories for the decontamination and recovery operations are the most complex and 

involve the most coordination and careful timing. 

Storage—ICAs in which all materials are within containers with measured values and 

are being stored for future processing or shipment. Some minor sampling of 

containers can occur in a storage ICA. Because nuclear materials in a storage ICA 

are primarily accounted for on an item basis, a true storage ICA typically will have a 

zero ID for each inventory period when all items are accounted for and their integrity 

and previously documented measured values are confirmed. 

Receiving and shipping—An ICA from which materials are shipped or into which 

materials are received from offsite and normally serves as an interim storage area. 

This type of ICA will normally see more activity (i.e., changes in current inventory) than the 

typical storage ICA. At some facilities, sampling and rebatching of items may occur in this 

type of ICA.

7.4 Description of Typical Item Strata

The MC&A plan should describe the expected item population in terms of the following:

• type(s) of item (i.e., stratum)

• expected range of the number of items within each stratum

• average elemental and isotopic content of the items within each stratum

• the expected rate of item generation and consumption for each stratum

7.5 Conducting Physical Inventories

Licensees should present a description of the methodology, including cutoff and inventory 

minimization procedures, and they should identify all measurements (including sampling) 

sufficient to meet the requirements of 10 CFR 74.43(c)(7). The MC&A plan should contain 

sufficient information to show how licensees obtained the total in process inventory for both 

elemental and isotopic content.
37 NUREG-2159

The means for measuring or estimating residual process material should be addressed in 

detail. The change or variation in such deposited holdup from one physical inventory to the 

next should also be discussed. This information is important to ensure that no SNM held 

under license (except for waste materials assigned to holding accounts in accordance with the 

exception provided in 10 CFR 74.43(c)(6) and U.S. Department of Energy/NRC Form 741 

instructions) will be omitted, and no quantity will be counted more than once.

The MC&A plan also should contain adequate commitments to ensure that each physical 

inventory will be organized and coordinated so that all involved persons are instructed in the 

use of uniform procedures for checking SNM quantities and recording observations. The 

means for conducting the inventory should ensure that any SNM held under license (except 

for waste materials, as noted above) is properly inventoried.

A detailed inventory notice should be prepared for each physical inventory. The notice should 

be issued to all involved parties and should contain instructions that define the timing and 

performance of various inventory steps and conditions under which the inventory is to be 

taken. The notice should identify specific sampling points throughout the process and 

instructions on data submission to the accountability organization. The instructions should 

highlight any required deviation from normal inventory procedures contained in the plant’s 

operating procedures. 

A description of the procedures and methodologies associated with performing physical 

inventories should be provided in sufficient detail to demonstrate that valid physical 

inventories are conducted. Such description should include a general outline of the following:

• organization and separation of functions

• assignment of inventory teams and their training in the use of uniform practices

• obtainment, verification, and record of source data

• control of inventory forms

• assurance that item counts verify the presence of each item while preventing any item 

from being counted more than once

• implementation of cutoff and material handling procedures 

Decontamination and recovery is a complex operation involving the disassembly and 

decontamination of failed pieces of process equipment and recovery of uranium from various 

types of scrap materials. The basic inventory procedure should involve establishing a cutoff of 

movement of materials into the area and processing all materials to a measurable form, such 

as containers of solution or oxide. Except for a decontamination enclosure in which inprocess solutions are mixed, sampled, and measured volumetrically, the inventory process 

should involve emptying and flushing of process systems and piping, which then could be 

measured using nondestructive assay (NDA) techniques to establish levels of residual holdup, 

if such holdup is significant. 

Licensees also should describe special item storage and handling or tamper-indicating 

methods, which are used to ensure that the previously measured and recorded SNM content 
NUREG-2159 38

values can be used for inventory purposes without remeasurements. In addition, the MC&A

plan should provide a description of how item identities are verified and how tampering with 

the contents of items will be detected or prevented. 

Items that are not encapsulated, affixed with tamper-indicating device (TIDs), or otherwise 

protected to ensure the validity of prior measurements need special attention. Licensees 

should present the basis for determining which items are to be measured at physical inventory 

time and the justification of any proposed alternatives to measurement of any SNM included in 

the inventory. If statistical sampling is proposed as an alternative method to 100 percent 

verification, the MC&A plan should describe the sampling plan. Such description should 

include the following:

• the method of stratifying the types of items to be sampled (i.e., selected for 

remeasurement)

• the procedure for calculating the sample size (i.e., the number of items) for each 

stratum

• the parameter to be measured (e.g., gross weight or total 235U content) 

• the quality of the measurement methods used to verify original measurement values 

(for the parameter being measured)

• the procedure for reconciling discrepancies between original and remeasurement 

values and for scheduling additional tests and remeasurements

• the basis for discarding an original SNM value and replacing it with a remeasurement 

value

One acceptable means for establishing the number of items (to be randomly selected for 

remeasurement) from a given stratum to give the required 90 percent power of detecting a 

loss of a significant quantity is given by the following equation:

n = N [1  (0.10)x/g]

where

n = number of items to be remeasured

N = total number of items in the stratum

x = maximum SNM content per item (kilograms)

g = SQ = significant quantity for statistical sampling plans, which is 

either one formula kilogram of strategic SNM or 10,000 grams of 

235U contained in uranium enriched to 10 percent or more, but 

less than 20 percent

When using such a statistical sampling plan to confirm the validity of prior measurements, the 

remeasurement value obtained for each item (among the n items remeasured) must be 

compared to its original value. If the difference for a given item exceeds some pre-determined 

limit (usually three times the standard deviation of the measurement, or 3 sigma), that item is 

designated as a “defect.” To achieve the 90 percent power of detection capability for 
39 NUREG-2159

detecting a loss as small as a significant quantity (SQ), there must be at least a 90 percent 

probability that one or more “defects” will be encountered among the items remeasured 

across all involved strata if an actual loss of an SQ has occurred. 

If, across all strata, the licensee encounters one or more defects, a second set of n randomly 

selected items (or all remaining items if n is greater than 0.5 N) from each stratum should be 

remeasured. If one or more defects are encountered (across all item strata) while performing 

any second round of remeasurements, the licensee should remeasure all unsealed and 

unencapsulated items not yet remeasured. Any item, regardless of if there are any defects, 

whose remeasured value differs from its original measurement by more than two sigma (2σ) 

should have its accounting value revised to reflect its remeasured quantity.

The MC&A plan also should contain a definitive statement that all items on ending inventory 

that have not been previously measured are measured for inventory purposes. 

Licensees should present in the MC&A plan their reason for determining when the element 

and isotope factors for items, objects, or containers are measured directly for inventory and 

when they may be based on other measurements. For example, if the 235U contained in liquid 

waste batches is derived by applying an average enrichment factor to the measured uranium 

element content, the rationale for such practice (as opposed to measuring each batch for both 

uranium and 235U content) should be discussed, and the plan should describe the method for 

establishing the average enrichment factor.

If the content of items is established through prior measurements and those items are sealed 

with TIDs or access to them is controlled, the SNM quantity in those items may be based on 

those measured values. Otherwise, verification of SNM content can be achieved by 

reweighing either (1) all items within a given stratum or (2) randomly selected items from the 

stratum based on a statistical sampling plan. The NRC will not accept a statistical sampling 

plan if there is any likelihood of any significant change in the elemental concentration (or 

weight fraction) or in the isotopic distribution because of such factors as oxidation, change in 

moisture content, commingling with materials of different enrichments, or different 

compositions.

7.6 Inventory Difference Limits and Response Actions

Each licensee should have a well-defined system for evaluating total plant IDs and for taking

actions when IDs exceed certain predetermined thresholds. As a minimum, there should be 

two response levels for excessive IDs. The following would be an acceptable approach for 

two increasing levels of response actions with respect to material balances closed by physical 

inventories:

Warning-level ID

 235U ID ≥ 1.7(SEID) + (300 grams of 235U or 200 grams of plutonium or 233U), or

 U ID ≥ 1.7 (SEID) + 10 kg U

Significant ID problem

 U, Pu, 235U or 233U ID ≥ 3(SEID)
NUREG-2159 40

All of the above limits are expressed in terms of absolute values of ID without regard for 

algebraic sign. The minimum response for a warning-level ID should be a documented 

licensee investigation conducted by the MC&A organization. Such an investigation should 

provide a conclusion for the probable cause of the excessive ID and give recommendations 

for avoiding recurrences. When a warning-level ID is positive, licensees should regard it as 

being equivalent to an indicator of a possible loss that requires investigation and resolution. 

For a significant ID problem, a licensee should conduct an extensive investigation. If a 

significant ID problem cannot be satisfactorily explained, a reinventory may be needed to 

resolve such an anomaly.

The NRC considers a significant positive ID (loss) problem to be a serious condition that calls 

for corrective action.

The MC&A plan should fully describe in definitive statements the minimum response actions 

for each ID action level.

7.7 Commitments and Acceptance Criteria

In its MC&A plan, the applicant or licensee should provide definitive commitments that adhere

to the regulatory requirements and meet the acceptance criteria applicable to the physical 

inventories. A finding that the licensee’s MC&A plan for conducting physical inventories is 

acceptable and in accordance with 10 CFR 74.43(c), will be based on, but not limited to, the 

following acceptance criteria:

• An MC&A system will be maintained that is capable of confirming, at intervals not to 

exceed 9 calendar months, the presence of all SNM expected to be present (at a given 

time) based on accurate, current, and reliable information. 

• Unless otherwise required by facility attachments that satisfy 10 CFR Part 75, 

“Safeguards on Nuclear Material—Implementation of US/IAEA Agreement,” physical 

inventories will be performed at least every 9 calendar months and will be used as the 

basis for reconciling and adjusting the book inventory, which is done within 

60 calendar days after the start of each physical inventory.

• For each physical inventory, inventory procedures are clearly written and are reviewed 

and approved by the individual responsible for the conduct of the physical inventory.

• The individual responsible for the conduct of the physical inventory is either free from 

potential conflicts of interest or is overchecked sufficiently to prevent compromising the 

validity of the physical inventory.

• Each physical inventory listing will include all SNM possessed (on the inventory date), 

with the possible exception of waste materials assigned to holding accounts (in 

accordance with U.S. Department of Energy (DOE)/NRC Form-741 instructions), and 

that all such listed SNM quantities shall be based on measurements.

• Within 60 calendar days after the start of each physical inventory, the inventory 

difference will be determined. Any ID that exceeds three times SEID and 300 grams of 
41 NUREG-2159

235U or 200 grams of plutonium or 233U will be reported to the appropriate NRC 

safeguards organizational units. 

• Discrepancies in the identity, quantity, or location of items, objects, or containers of 

SNM that are detected during a physical inventory will be corrected.

• Inventory difference values will be corrected for (1) accounting adjustments resulting 

from prior period activity, and (2) significant biases that have not previously been taken 

into account. (NOTE: See the definition of “significant bias” in Chapter 6 of this plan).

• Adjustments made to reconcile the book inventory to the physical inventory are in 

accordance with standard accounting practices and are traceable and auditable in the 

MC&A records.

• Whenever a finalized ID (after applying any appropriate bias corrections and prior 

period adjustments) exceeds three times SEID and 300 grams of 235U or 200 grams of 

plutonium or 233

U, and is not resolved within the 60-day reconciliation period, all SNM 

processing should be halted unless otherwise authorized by the NRC. (NOTE: This 

applies to both positive and negative ID values.)

• The results of all physical inventories and of investigations and resolution actions 

following any excessive ID are recorded and auditable. An excessive ID is one 

(regardless of the algebraic sign) that exceeds both three times SEID and 300 grams 

of 235U or 200 grams of plutonium or 235

U.

• The licensee may propose alternatives to remeasurement. The MC&A plan should 

describe the circumstances under which each proposed alternative may be used. The 

proposed alternatives should satisfy at least one of the following criteria:

o SNM content is verified by statistical sampling and measurement of 

representative items, objects, or samples of the material. The total overall 

sampling plan shall support the capability for detecting any loss in excess of 

the pertinent SQ with 90 percent (or better) probability.

o The previous measurement results are accepted because the items are stored 

in a controlled access enclosure that provides protection equivalent to 

tamper-safing.

o Residual holdup in significant amounts which remains after cleanout or 

draindown may be estimated if the estimate is based on previously measured 

values and it is periodically verified or validated.

o For material whose SNM content has been previously measured, and there is 

no likelihood of any significant change in the uranium concentration (or weight 

fraction) or in the uranium enrichment because of such factors as oxidation, 

change in moisture content, commingling with materials of different enrichment 

or different composition, etc., the previously determined SNM content may be 

accepted without verification—provided the gross weight or net weight of all 

items within the population is confirmed by (1) a 100 percent reweighing of all 

such items, or (2) reweighing an adequate number of randomly selected items 
NUREG-2159 42

(based on a statistical sampling plan) to provide a 90 percent (or better) 

probability of detecting a loss equal to or greater than the current SQ.

• As an additional alternative to re-measurement (of unsealed SNM) at physical 

inventory time, a program of routine process monitoring will be acceptable when the 

combination of the process monitoring program and the inventory procedures will 

achieve the same level of loss detection capability as that provided by a physical 

inventory in which all unencapsulated items are either tamper-safed or remeasured.

• Any previously measured, but unsealed (or unencapsulated) SNM that is on hand at 

the time of the physical inventory, and which is to be introduced into subsequent 

processing steps before inventory reconciliation should be re-measured or have its 

prior measurement value confirmed (by an acceptable alternative) before the 

subsequent processing is initiated.

• The SQ for statistical sampling plans will be one formula kilogram of strategic SNM or 

10,000 grams of 235U contained in uranium enriched to 10 percent or more, but less 

than 20 percent.

• The MC&A plan should state that the threshold of three times SEID for identifying an 

excessive ID will result in a 90 percent (or better) probability of detecting a discrepancy 

equal to or greater than 0.4 percent of the active inventory for the inventory period in 

question. In general, a licensee may assume the ID distribution approximates a 

normal distribution. Acceptable methodology for calculating the measurement error 

contribution to the SEID by error propagation is found in NUREG-4604, TID-26298,

and the IAEA statistics handbook (1989). Special attention is given to inclusion of all 

measurable sources of error to avoid underestimating the SEID.

• In addition to the three times SEID ID limit required by 10 CFR 74.43(c)(8), there is an 

excessive ID warning level limit that, when exceeded, will require an investigative 

response action. The resources and level of effort a licensee should commit to the 

investigation of an excessive ID will be proportional to the magnitude and material type 

and enrichment of the ID, and it will be sufficient to reassess the results of the physical 

inventory, the accounting records, and the measurement control program data; to 

confirm the relevant calculations and data analysis; and, when necessary, to carry out 

searches for unmeasured inventory such as residual holdup and measurement 

discards. Investigations are to be completed within 60 calendar days after initiating the 

inventory (except when additional time is granted by the NRC for extenuating 

circumstances).
43 NUREG-2159

8. ITEM CONTROL

8.0 Regulatory Intent

The intent of Title 10 of the Code of Federal Regulations (10 CFR) 74.43(b)(5) and (6) is to 

require licensees to establish, document, and maintain an item control system to protect against 

unauthorized and unrecorded removal of items, or of material from items, and to enable timely 

location of items. Items, as defined in 10 CFR 74.4,”Definitions,” mean any discrete quantity or 

container of special nuclear material or source material, not undergoing processing, having an 

unique identity and also having an assigned element and isotope quantity. Examples of items 

are known quantities of special nuclear material (SNM) in well-defined and uniquely identified 

containment such as cans, drums, and canisters, or fixed units such as fuel assemblies. 

Uncontainerized solid SNM, such as uranium metal ingots or buttons, are also items if they are 

uniquely identified. To promptly locate a given item, licensees must record sufficient current 

information. 

8.1 Organization

The material control and accounting (MC&A) plan should identify the individual responsible for 

overseeing the item control system by position title. Positions of those individuals who have 

significant item control system responsibilities also should be identified.

8.2 General Description

The applicant or licensee should state that the overall MC&A system maintains a record of all 

SNM items, regardless of quantity or duration of existence. In addition, the item control system

should provide current knowledge of the location, identity, and quantity of all SNM contained in 

all items that are not exempt from item control. Items that can be exempt from item control 

system coverage are: 

• containers of waste (designated for burial or incineration)

• containers of solutions in which the plutonium,uranium-235 ( 233U) or uranium-233 (235U)

concentration is less than 5 grams per liter.

Each item that is not exempt from the item control system should be stored and handled in a 

manner that enables detection of, and provides protection against, unauthorized or unrecorded 

removals of SNM. All items, whether or not they are subject to item control system coverage, 

should have a unique identity. For items subject to the item control system, the following are 

acceptable means for providing unique identity:

• a unique alpha-numeric identification on a tamper-indicating device (TID) applied to a 

container of SNM

• a unique alpha-numeric identification permanently inscribed, embossed, or stamped on 

the container or item itself

• a uniquely pre-numbered (or bar-coded) label applied to each item having good 

adhesive qualities such that its removal from an item would preclude reuse of the label
NUREG-2159 44

Location designations shown by the MC&A records need not be unique, but location 

designations should be specific enough so that any item may be located within 1 hour. Longer 

times may be acceptable but should be further justified in the MC&A plan. The MC&A record 

system should be controlled in such a manner that the record of an item's existence cannot be 

destroyed or falsified without a high probability of detection. 

8.3 Item Identity Controls

Descriptions should be provided of the item records showing how items are identified for each 

material type and each type of container. If the unique number on a TID is the basis for 

providing unique item identity, the MC&A plan should:

• Describe the type of TID used.

• Describe how the TIDs are obtained and what measures are implemented to ensure that 

duplicate (counterfeit) TIDs are not manufactured.

• Describe how the TIDs are stored, controlled, issued, and accounted for.

• Describe how TID usage and disposal records are maintained and controlled.

Licensees should provide similar information for other methods of unique item identity 

(e.g., labels). 

8.4 Storage Controls

The MC&A plan should full describe item storage areas and controls. In particular, controls that 

are used as the basis for ensuring the values of prior measurements, as opposed to 

remeasuring the item at inventory time, should be discussed in detail and the rationale for 

accepting prior measurements explained. Any controls used to ensure the validity of prior 

measurements should be equivalent to the protection provided by tamper-safing, which is 

defined by 10 CFR 74.4 as the use of devices on containers or vaults in a manner and at a time 

that ensures a clear indication of any violation of the integrity of previously made measurements 

of the SNM in the container or vault.

Both administrative controls (e.g., custodian assignments and limiting authorized access to 

storage areas) and physical controls (e.g., locked or alarmed doors) should be identified.

8.5 Item Monitoring Methodology and Procedures

As part of the item control system, a licensee should maintain a system of item monitoring that

achieves the following:

• verifies that items shown in the MC&A records are actually stored and identified in the 

manner indicated in the records

• verifies that generated items and changes in item locations are properly recorded in the 

MC&A record system in a timely manner

• detects, with high probability, any real loss of items or uranium from items. 
45 NUREG-2159

The item monitoring system should conduct the following activities at least every 2 weeks for 

strategic SNM and on a monthly basis for 235U contained in uranium enriched to 10 percent or 

more, but less than 20 percent:

• For each item inventory stratum, compare the actual storage status to the recorded 

status of a sufficient sample of randomly selected items from the item control program 

records.

• For each item inventory stratum, check the accuracy of the MC&A records for a sufficient 

sample of randomly selected items from each storage area.

• Check the accuracy of a sufficient sample of randomly selected production records of 

created and consumed items

The actual frequency of the above activities, and the size of the random sample, should be a 

function of the expected discrepancy rate based on prior observations. The MC&A plan should 

specify (1) minimum monitoring frequencies associated with each storage area, (2) discrepancy 

rates that trigger more frequent monitoring frequencies, and (3) commitments for resolving 

discrepancies.

8.6 Investigation and Resolution of Item Discrepancies

The applicant or licensee should provide definitive statements of the procedures and controls 

that will ensure that all incidents involving missing or compromised items or falsified item 

records will be investigated. A compromised item is (1) an item displaying evidence of 

tampering or (2) an unencapsulated and unsealed item assigned to a controlled, limited-access 

storage area that is found outside its documented location.

If any unencapsulated and unsealed item is located after having been determined to be missing, 

or if an item is found to be compromised, its contents should be reestablished by measurement 

(e.g., by NDA or by weighing, sampling, and analysis). Licensees should follow 

recommendations on resolution of indicators (Chapter 13) of this document to resolve item 

discrepancies.

8.7 Commitments and Acceptance Criteria

In its MC&A plan, the licensee should provide definitive commitments that adhere to the 

regulatory requirements and meet the acceptance criteria applicable to maintaining current 

knowledge of items and detecting unauthorized removals. A finding that the licensee’s MC&A 

plan for the item control system is acceptable and in accordance with 10 CFR 74.43(b)(5) and 

(6), will be based on, but not limited to, the following acceptance criteria:

• The item control system uses statistical sampling, as an alternative to 100 percent

verification, at least every 2 weeks for strategic SNM, and on a monthly basis for 235U 

contained in uranium enriched to 10 percent or more but less than 20 percent.

• The licensee’s item record system uniquely identifies items. The records include 

information on the chemical form, quantity of material (element and isotope), physical 

description, identification label or number, and location. The system provides 
NUREG-2159 46

reasonable assurance of detecting falsification or destruction of records of an item’s 

existence.

• In its MC&A plan, a licensee may propose that certain groups of items that are 

produced, stored, processed, or otherwise handled together as a unit, such as a batch or 

sublot of material, may be uniquely identified and stored as a separate group under 

conditions such that group identity, composition, and quantity will be maintained 

constant.

• The record of the status of an item can be completed or updated in sufficient time to 

allow the licensee to meet the requirements for promptly locating an item.

• For items that will not be remeasured at inventory time, the item control procedures 

provide reasonable assurance that the SNM contents stated in the records are valid and 

that unauthorized removal of SNM from the item has not occurred. Remeasurement is 

not necessary if the SNM content of the item was measured previously and the licensee 

provides reasonable assurance that the SNM content has not subsequently changed.

• A current accounting is maintained of the total quantity of SNM contained in items that 

are exempted from item control. The accounts identify the quantities by material type 

category for both controlled and exempted items.

• For items not exempted from the item control system, the licensee maintains a record 

system to provide knowledge of the current status of such items. For items subject to 

this commitment, the item control and records system provides the capability to promptly 

locate and confirm the existence of any specific item or group of items upon demand. 

The item record system is secured in such a manner that the record of an item’s 

existence cannot be destroyed or falsified by a single individual without a high probability 

of detection.

• For items not exempted from the item control system, each item is stored and handled in 

a manner that enables detection of or provides protection against unauthorized or 

unrecorded removals of SNM. Otherwise, knowledge of the SNM content is assured by 

tamper-indicating devices or by maintaining the item as a sealed source (i.e., as 

encapsulated material).

• All incidents involving missing or compromised items or falsified item records are 

investigated. A compromised item is one for which there is evidence of tampering or 

which is found outside its assigned controlled access area.

• The contents of a compromised item or an unsealed, unencapsulated item located after 

it has been missing will be redetermined by measurements (i.e., by NDA or by weighing, 

sampling, and analysis).
47 NUREG-2159

9. SHIPPER RECEIVER COMPARISONS

9.0 Regulatory Intent

The intent of Title 10 of the Code of Federal Regulations (10 CFR) 74.43 (b)(7) is to require the 

licensee to conduct and document shipper–receiver comparisons for all special nuclear material 

(SNM) receipts—on both an individual batch basis and total shipment basis—and ensure that 

any shipper–receiver difference (SRD) that is statistically significant and exceeds twice the 

estimated standard deviation of the difference estimator and 200 grams of plutonium or uranium 

-233 (233U), or 300 grams of uranium-235(

235U) is investigated and resolved. 

9.1 Receiving Procedures

The first action taken on receipt of SNM should be to verify the number of items, the item 

identities, and the integrity of individual items and of tamper-indicating devices (TIDs). All SNM 

shipments received from an external supplier are subject to shipper–receiver comparisons. 

Such comparisons involve measurement of received material by the receiver, or by the 

receiver’s contractor (who is independent of the shipper), and comparing the receiver’s total 

receipt measurement for element and isotope to that of the shipper’s. 

Previously, in approving material control and accounting (MC&A) plans, the NRC staff has 

recognized situations in which the cost of conducting and documenting shipper–receiver 

comparisons outweighs the safety benefit of doing so, and it has accordingly granted relief in 

the form of exemptions notwithstanding the 10 CFR 74.43 (b)(7) provision that the requirement 

applies to “all SNM receipts.” Examples of situations in which such relief has been granted are

as follows:

• shipments containing less than 300 grams of 235U or 200 grams of plutonium or 233U

• individual items containing less than 15 grams 235U, plutonium or 233U

• encapsulated items whose encapsulation integrity has not been compromised, and 

which are to be retained by the licensee as encapsulated items

• fuel assemblies and fuel rods previously shipped by the licensee that are being returned, 

provided that the original encapsulation has not been compromised;

• UF6 cylinders that are empty except for a heel quantity of UF6

• heterogeneous scrap that must be subject to dissolution before a meaningful 

accountability measurement can be obtained. Both shipper and receiver should agree to 

accept the “after dissolution plus residue” measurements for accounting purposes.

Should licensees in the future seek similar relief from the 10 CFR 74.43 (b)(7) requirements,

they will need to submit specific exemption requests in accordance with 10 CFR 74.7, “Specific 

Exemptions.” If the law authorizes the granting such exemption requests and doing so would 

not endanger life or property or the common defense and security and would otherwise be in the 

public interest, the NRC will consider such exemptions, to be determined on a case-by-case 

basis. 
NUREG-2159 48

For any SNM received, the licensee must provide all appropriate information on the DOE/NRC 

Form 741 that accompanies the shipment, in accordance with 10 CFR 74.15, “Nuclear Material 

Transaction Reports.” (NOTE: See NUREG/BR-0006, “Instructions for Completing Nuclear 

Material Transfer Reports (DOE/NRC Forms 741, 741A, and 740M),” Revision 7, dated 

February 2000, for instructions and requirements for completing U.S. Department of 

Energy/NRC Form 741.)

9.2 Determination of Receiver's Values

Licensees should measure SNM receipts for total quantity (mass), element concentration (such 

as for plutonium dioxide, uranium dioxide, or uranyl nitrate solutions), and fissile isotope 

abundance (235U or 233U).

The validity of the shipper’s data should be substantiated with appropriate and timely receiver 

checks and measurements, including gross weight, adequate sampling techniques, 

nondestructive assay (NDA) measurements (if appropriate), and destructive measurements 

(scrap excepted). (See Chapter 4 on measurements above.) Shipper’s values may be 

accepted and booked without receiver element or isotope measurements for encapsulated 

items, such as fuel elements or rods, if NDA measurement is not feasible.

9.3 Evaluation of Shipper-Receiver Differences

When shipper’s measurement uncertainty (or standard error) information is available, the 

following should define the estimated standard deviation of the difference estimator or combined 

standard error:

combined standard error = [(σS)

2 + (σR)2

] 1/2

where

σS = shipper’s measurement standard error

σR = receiver’s measurement standard error

If the shipper’s measurement uncertainty values are not available, the receiver can assume that 

the shipper’s measurement uncertainty is equal to (but no greater than) its own uncertainty. In 

this situation (i.e., both shipper and receiver have the same measurement uncertainty), the 

following becomes the combined measurement standard error:

combined standard error = [ 2 (σR)

2

] 1/2

= 1.414 σR

The difference between the shipper’s value and the receiver’s value (i.e., the SRD), in terms of 

the total shipment, must be regarded as significant whenever the SRD exceeds both 300 grams 

of 235U or 200 grams of plutonium or 233

U and twice the combined standard error. Licensees 

also must regard as significant an SRD in excess of both 300 grams of 235U or 200 grams of 

plutonium or 233U and twice the combined standard error with respect to an individual batch 

within the shipment.
49 NUREG-2159

9.4 Resolution of Significant Shipper–Receiver Differences

The MC&A plan should describe the steps involved with the investigation of a significant SRD 

and discuss how such difference is resolved. The plan also should present criteria for defining a 

resolved SRD. Generally, resolution of a significant SRD could involve a referee (or umpire) 

measurement of a retainer sample(s) but not of the material weight. The resolution process 

should specify whose weight value is used in the resolution process if shipper’s and receiver’s 

weights differ by more than one-half of the total combined standard error.

9.5 Commitments and Acceptance Criteria

In its MC&A plan, the licensee should provide definitive commitments that adhere to the 

regulatory requirements and meet the acceptance criteria applicable to shipper–receiver 

comparisons. A finding that the licensee's MC&A plan for conducting SRD evaluations and 

resolving significant SRDs is acceptable and in accordance with 10 CFR 74.43 (b)(7) will be 

based on, but not limited to, the following acceptance criteria:

• Each shipping container is inspected within 5 working days after receipt for loss or 

damage to the container or TIDs to determine if SNM could have been removed. If the 

integrity of a container is questionable, the presence of all items that were packaged in 

the shipping container will be confirmed within 24 hours of discovering the questionable 

integrity. Only acceptable tamper-safing methods will be used as described in 

Section 11.1 of this document and as agreed to with the receiver.

• Complete the receipt of nuclear material within 60 calendar days, except in the cases of 

scrap that cannot be representatively sampled and irradiated material (see Section 4.5).

• Conduct and document shipper–receiver comparisons for nonexempt SNM receipts, 

both on an individual batch basis and a total shipment basis, and ensure that any SRD 

that exceeds twice the estimated standard deviation of the difference estimator and 

200 grams of plutonium or 233U or 300 grams 235U is considered statistically significant, 

and is investigated and resolved within 90 days of material receipt or, if not resolved 

within that period, the unresolved difference is reported to the NRC.

• The significance of a SRD is based on statistical tests.

• Measurements of the quantity of SNM received in each shipment are performed and the 

SRD is tested for statistical significance. The element and isotopic content of SNM 

shipped or received by the licensee are based on measurements obtained from 

measurement systems subject to the measurement control program. Occurrences of 

statistically significant SRDs in excess of 300 grams of 235U or 200 grams of plutonium or 

233U, and missing items are reported to the shipper promptly.

• Measurement results for shipments and receipts are corrected for biases that are 

significant at the 0.05 level (i.e., for any bias that exceeds two times the standard error 

associated with a mean) and which impact individual items by more than their rounding 

error in terms of plutonium, 233U, 235U, or uranium content.

• Confirmatory measurements of scrap shipments are performed by the receiver to 

determine the amount of plutonium or uranium element and fissile isotope consistent 
NUREG-2159 50

with the accountability needs of the shipper. However, heterogeneous scrap that cannot 

be accurately measured in its received form need not be measured until after 

dissolution, within 18 months of receipt (see Section 4.5 of this document).

• For SNM received, SRDs that are statistically significant and also greater than 

300 grams 235U or 200 grams of plutonium or 233U on a total shipment basis (or on a 

batch basis) are detected within 30 days of receipt, except for those materials granted 

an exemption by the NRC. 

• SNM shipments for which the licensee has been granted an exemption from the 

shipper–receiver comparison requirements are clearly identified. 

• The investigation procedure for significant SRDs is sufficiently comprehensive to ensure 

that the difference will be resolved. Comprehensiveness is sufficient if the licensee 

shows the capability to verify records, resample, perform remeasurements, establish 

liaison with the shipper, provide samples to a referee laboratory, and perform the 

statistical analysis needed to evaluate the measurements.

• The documentation of shipments and receipts should be completed and transmitted 

within the time specified in NUREG/BR-0006.
51 NUREG-2159

10. ASSESSMENT AND REVIEW OF THE MATERIAL CONTROL 

AND ACCCOUNTING PROGRAM

10.0 Regulatory Intent

The intent of Title 10 of the Code of Federal Regulations (10 CFR) 74.43(b)(8) is to require 

independent assessments of the material control and accounting (MC&A) program. Licensee 

management must periodically (at least every 18 months) review and assess the performance 

of the MC&A program, evaluate its effectiveness, and document management’s action on prior 

assessment recommendations and any identified deficiencies. The NRC intends that the review 

will be performed by knowledgeable, technically competent individuals free from conflicts of 

interest and that the deficiencies will be brought to the attention of plant management so that 

they will be corrected. It should be emphasized that this review process is intended to be much 

more than a routine audit for compliance with existing procedures and commitments. The 

review must draw conclusions and make recommendations relative to overall program 

effectiveness and to the adequacy of the MC&A program—including that of any contractor who 

performs special nuclear material (SNM) measurements on the licensee’s behalf.

10.1 General Description

The capabilities, performance, and overall effectiveness of the licensee's MC&A program should 

be independently reviewed and assessed at least every 18 months. The MC&A plan should 

describe the assessment and review program in terms of:

• maximum interval between assessments

• selection procedures for the assessment team

• number of team members to be selected

• qualification and expertise of team members

• independence of individual team members from the MC&A responsibilities and activities 

they are reviewing and assessing

• maximum elapsed time and minimum actual effort to be used for completion of the 

assessment and issuance of a final team report

The licensee generally should review and evaluate the entire MC&A program during each 

assessment. When this occurs, intervals between assessments can be as much as 18 calendar 

months. However, if individual assessments only cover part of the MC&A system, individual 

subsystems should be assessed at intervals no greater than 9 calendar months. The schedule

should ensure the entire program is reviewed over the course of 18 calendar months. Thus, the 

MC&A plan should specify the type of assessment (partial or total) and the maximum interval 

between assessments. “Interval” means the elapsed time between either the start of or 

termination of successive assessments. 

The responsibility and authority for the assessment program should be at least one level higher 

in the licensee’s organizational structure than that of the MC&A manager. Such responsibility 

should include selecting the assessment team leader and initiating corrective actions. Team 
NUREG-2159 52

members may be selected from the facility staff or from outside, but an individual member 

should not participate in the assessment of the parts of the MC&A system for which that person 

has direct responsibility. Hence, the MC&A manager may not be a team member. Also, a given 

individual should not assess the parts of the system that are the responsibility of another team 

member if the other team member is assessing the given individual's area. The leader of the 

assessment team should have no responsibilities for managing any of the MC&A elements 

being assessed. 

The actual number of team members for any given assessment should depend on the 

knowledge and expertise of the team members relative to MC&A activities and their experience 

in conducting assessments. Personnel assigned to the assessment team should have 

demonstrated an understanding of the regulatory objectives and requirements of the MC&A 

program and should have sufficient knowledge and experience to be able to judge the adequacy 

of the parts of the system they review. The team should have authority to investigate all 

aspects of the MC&A system and should be given access to all necessary information.

To provide a meaningful and timely assessment, the review and evaluation process should not 

be protracted. The actual review and investigation activities should be completed in 30 calendar 

days, with an additional 15 calendar days allowed for completing and issuing a final team report.

10.2 Report of Findings and Recommendations

The areas to be reviewed should encompass the entire MC&A system, and the level of detail of 

the reviews should be sufficient to ensure the assessment team has made an adequate and 

reasoned judgment of the MC&A system effectiveness. The team report, as a minimum, should 

state findings pertaining to:

• organizational effectiveness to manage and execute MC&A activities

• management responsiveness to indications of possible losses of uranium

• staff training and competency to carry out MC&A functions

• reliability and accuracy of accountability measurements made on SNM

• effectiveness of the measurement control system in monitoring measurement systems 

and its sufficiency to meet the requirements for controlling and estimating both bias and 

SEID

• soundness of the material accounting records

• effectiveness of the item control program to track and provide current knowledge of 

items

• capability to promptly locate items and effectiveness in doing so

• timeliness and effectiveness of shipper–receiver difference (SRD) evaluations and 

resolution of excessive SRDs

• soundness and effectiveness of the inventory-taking procedures
53 NUREG-2159

• capability to confirm the presence of SNM

• capability to detect and resolve indications of missing SNM

On completion of each assessment, the evaluation team should document findings and 

recommendations for corrective action, if any. It should distribute the written report to the plant 

manager, the MC&A manager, and other managers affected by the assessment.

10.3 Management Review and Response to Report Findings and Recommendations

Management should review the assessment report and take the necessary actions to correct 

MC&A system deficiencies. The management review should be documented within 30 days 

following the submittal of the assessment team's report, and it should include a schedule for the 

correction of deficiencies. Corrective actions, if any, that pertain to daily or weekly activities 

should be initiated promptly after the submittal of the final assessment report.

The MC&A plan should address resolution and followup actions associated with concerns 

identified in the assessment report. The individuals responsible for resolving identified 

concerns, and the timeliness of such resolution, should be specified.

10.4 Commitments and Acceptance Criteria

In its MC&A plan, the licensee should provide definitive commitments that adhere to the 

regulatory requirements and meet the acceptance criteria applicable to independent 

assessments of the MC&A program. A finding that the licensee’s MC&A plan for such 

assessments is acceptable and in accordance with 10 CFR 74.43(b)(8) will be based on, but not 

limited to, the following acceptance criteria:

• The capabilities and performance of the MC&A program will be reviewed and its 

effectiveness will be independently assessed at least every 18 months. This means that

the nominal elapsed time from the completion of one review or assessment to the 

completion of the next will not exceed 18 months.

• The periodic assessments will be comprehensive and sufficiently detailed to enable the 

assessment team to rate the MC&A system accordingly. The overall assessment 

objectives are to determine that the MC&A system, as designed and implemented, are 

continuing to meet the general performance objectives, and to identify weaknesses or 

deficiencies in the system design or performance that may need correcting.

• The areas to be reviewed encompass the entire MC&A program, and the level of detail 

of the reviews is sufficient to ensure that the assessment team has adequate information 

to make reasoned judgments of the MC&A system effectiveness which includes:

o organizational effectiveness and management responsiveness to indicators of 

possible SNM losses

o staff training and competency to carry out MC&A functions

o soundness of the material accounting records
NUREG-2159 54

o capability to promptly locate items;

o timeliness and effectiveness of SRD evaluations and resolution of significant 

SRDs

o soundness of physical inventory procedures and practices

o effectiveness of the measurement control system to monitor key measurement 

systems, establish bias estimates and measurement uncertainties, and meet the 

requirements for controlling the total MC&A measurement uncertainty associated 

with ID.

o capability to confirm the presence of SNM

o capability to investigate and resolve anomalies and aid in any government-led 

investigation of missing SNM and to provide information that would aid in the 

recovery of missing SNM

• Generally accepted auditing principles are used to check each type of record in which a 

representative sample (of a sufficient number) of randomly selected records is 

examined.

• Reviews and assessments are performed either by qualified individuals from outside the 

facility or qualified individuals from inside the facility organization whose work 

assignments and positions within the organization will not impair their ability to make 

objective judgments of the MC&A program capabilities and performance. Personnel 

assigned to the assessment team will have an adequate understanding of the regulatory 

objectives and requirements of the MC&A system and will have sufficient knowledge and 

experience to be able to judge the adequacy of the parts of the system they are asked to 

review. The team will have authority to investigate any aspect of the MC&A program 

and will have access to all relevant information.

• An individual team member will not participate in the assessment of any part of the 

MC&A system for which he or she has direct responsibility. Also, an individual “A” will 

not assess any part of the system that is the responsibility of person “B” if B is assessing 

an area under the responsibility of A.

• The entire MC&A program will be reviewed and evaluated during each single 

assessment (to be completed within an elapsed time that is short relative to the time 

between changes in the MC&A system and is demonstrated to be able to include any 

such changes made during the review/assessment). Conducting two or more 

assessments during an 18-month interval, in which only part of the MC&A system is 

covered in each, is acceptable if each subsystem is covered at 9-month (or less) 

intervals. It is important to assess the MC&A program as a whole to evaluate how 

individual systems interact. Therefore, if more than one assessment is to be conducted, 

the review should include consideration of how well the other components currently 

interact. 
55 NUREG-2159

• The leader of the assessment team will have no responsibilities for performing or 

managing the functions being assessed. The assessment team leader will have no 

responsibility for managing or performing any of the MC&A functions.

• The responsibility and authority for the assessment program and for initiating corrective 

actions should be: (1) at least one level higher in the organization than the MC&A 

manager, or (2) at a level equal to that of the on-site plant manager.

• Each overall review and assessment will be conducted and completed in a time frame 

that is short with respect to the time for changes to have occurred in the MC&A program 

and will include any such changes made during the time the review or assessment is 

being conducted.

• The completion date for any review and assessment is defined as the date when the 

team submits its final written report (of findings and recommendations) to plant 

management. The start date is the first day in which one or more team members 

actually inspect records or interview MC&A personnel, and the team will document such 

start date.

• The results of the assessment and recommendations for corrective action, if any, will be 

documented and reported to the plant manager and other managers affected by the 

assessment. Management will review the assessment report and take the necessary 

actions to correct MC&A program deficiencies. Such corrective actions (if any) that 

pertain to daily or weekly activities will be initiated within 30 calendar days following the 

submittal of the review and assessment final report.

• Management's response to recommendations from the review and assessment, 

including any corrective actions ordered by management and the expected time frame 

for completing such actions, will be documented within 30 calendar days following the 

submittal of the team's report.

57 NUREG-2159

11. TAMPER-SAFING

11.0 Regulatory Intent

The intent of Title 10 of the Code of Federal Regulations (10 CFR) 74.43(c)(3) is to require 

licensees to maintain and follow tamper-safing procedures for special nuclear material (SNM)

containers and vaults, including controlling access to, and distribution of, unused seals and 

records. The intent of such procedures is to document the distribution, application, and 

destruction of tamper-safing devices, as well as routine inventory of unused tamper-safing 

devices. Licensees should retain records for at least 3 years (or longer if specifically required 

by regulations external to 10 CFR 74.41, “Nuclear Material Control and Accounting for Special 

Nuclear Material of Moderate Strategic Significance”), thereby providing a means for assessing 

the performance of the tamper-safing program and inspecting for compliance with regulatory 

requirements. 

11.1 Characteristics of Tamper-Safing Devices

The use of tamper-indicating devices (TIDs) on containers or vaults is one such level of 

protection licensees use to secure the integrity of SNM either when it is in transit or stored on 

site. The one overriding objective of TIDs is to ensure that no tampering or entry has occurred 

while the TID is on the container. Therefore, for material control and accounting (MC&A)

purposes, the degree of confidence in the selection of a TID sealing system will vary depending 

on its unique characteristics and intended use.

When selecting TIDs, licensees should consider the following:

• Intended use: the determination the TID is appropriate for the tamper-safing of the 

container and withstanding the working environment, (i.e., temperature, moisture, 

repeated handling).

• Application: the relative ease or difficulty of physically applying the TID.

• Substitution: the ability of a TID to be destructively removed and replaced by a new TID

without detection.

• Removal and reapplication: the ability of a TID to be removed and reapplied without 

detection.

• Alteration of label data : the ability to alter recorded data on the TID without the alteration 

being apparent.

• Integrity Verification: the degree of effort required to verify the TID is intact or indicates 

tampering.
NUREG-2159 58

The licensee should confirm the manufacture’s claims that the removal of a TID is not possible 

without detection by testing potential TIDs to see if they can be removed from the containers on 

which they are to be used. The licensee should confirm the results by using the manufacturer’s 

documented procedures and the samples used. The experiments should be documented, both 

with regard to what techniques the licensee used to attempt to defeat the TID and observations 

as to the degree of success in defeating the TID. In lieu of testing by the licensee, similar tests 

conducted by an independent third party may be considered acceptable.

11.2 Use of Tamper-Safing Devices

The MC&A plan may allow the use of TIDs to achieve the following:

• Ensure the long-term validity of measurement data. The application of a TID to an item 

containing measured quantities of nuclear materials may allow the licensee to maintain 

the validity of the original measurement value, thus eliminating or decreasing the 

frequency of the need to remeasure the items to verify their nuclear material content.

• Reduce the effort to conduct physical inventories or item control activities. The 

application of a TID to a container housing multiple items may allow the licensee to 

maintain the validity of container’s contents, thus minimizing the number of items 

required to be verified during a physical inventory or item control activity.

• Provide assurance of integrity of intransit material. The application of a TID to a 

shipping container may allow the licensee to maintain the validity of shipping container’s 

contents and provide assurance that the integrity of the shipment has not been violated. 

To achieve this goal, the shipper must apply the TID(s) to the shipping container, verify 

the integrity of the TID(s) shortly before departure of the shipment, and provide the 

appropriate information (i.e., shipping container serial numbers, TID(s) type(s), and 

serial number(s)) to the receiver. Upon receipt of the shipment, the receiver should 

verify the shipping container serial numbers, TID(s) type(s), serial number(s), and the 

TID(s) integrity. Any discrepancies should be considered an MC&A anomaly and be 

addressed by the facility’s MC&A resolution program.

11.3 Description of Tamper-Safing Records

The tamper-safing system should identify all records, forms, reports, and standard operating 

procedures used throughout the program. Such records should include, but are not limited to, 

the following:

• receipt of purchased TIDs

• issuance of TIDs

• identification of the person applying the TIDs

• identification of the person who verified the application of the TID

• identification of the container to which the TIDs was applied, including the TIDs serial 

identification (if applicable)

• removal and destruction of TIDs
59 NUREG-2159

• routine inventory of unused and unissued TIDs

• identification of roles and responsibilities, including:

o designation of the TID control officer(s)

o personnel approved to apply, verify, and destroy TIDs

• training of personnel in the application, verification, and destruction of TIDs.

11.4 Commitments and Acceptance Criteria

The acceptability of a TID is based on an evaluation of the attributes of the device in relation to 

time to defeat the tamper-indicating features. TIDs the NRC has already deemed acceptable 

include: Type E, pressure-sensitive, tamper-evident wire seals, fiber optic seals, and steel 

padlocks. Other TIDs may be equally acceptable. Licensees proposing to use TIDs not 

currently approved by the NRC must provide the appropriate information, including references, 

to enable licensing reviewers to assess the adequacy of the proposed TID type.

In its MC&A plan, the licensee should provide definitive commitments that adhere to the 

regulatory requirements and meet the acceptance criteria applicable to the use of tamper-safing 

devices. A finding that the licensee’s MC&A plan for tamper-safing is acceptable and in 

accordance with 10 CFR 74.43(c)(3), will be based on, but not limited to, the following 

acceptance criteria:

• Only TIDs that are controlled and accounted for are used to maintain the validity of 

previously established SNM quantities associated with items.

• Written procedures are maintained to ensure that individuals authorized to handle TIDS

are properly trained.

• Preferably, a single individual, but no more than three individuals (none of whom have 

any responsibility for seal application or destruction), is (are) designated as the 

tamper-safing device control officer(s).

• TIDs are only applied and removed by individuals authorized for that purpose.

• Unused TIDs are controlled and inventoried. Unissued tamper-safing devices are stored 

in a locked container within a room that is locked when unoccupied or in an approved 

repository. Blocks of tamper-safing devices issued to designated individuals are stored 

in a locked container within a room that is locked when unoccupied or in an approved 

repository.

• When TIDs are not in storage, they are in the possession of authorized individuals 

(i.e., the tamper-safing device control officer or person responsible for applying the 

tamper-safing device.) As a rule, the number of available seals issued to these 

individuals should be limited to a single day’s use.

• The licensee has in its possession a commitment from the seal manufacturer that plates 

and dies and production residuals are controlled and protected.
NUREG-2159 60

• Upon removal, TIDs are destroyed (i.e., crimped, flattened, or otherwise rendered 

unusable) and properly disposed.

• Records of TID application, verification, removal, and destruction are documented, and 

control measures are implemented to prevent alteration of records concerning 

containers protected by TIDs.
61 NUREG-2159

12. DESIGNATION OF MATERIAL BALANCE AREAS,

ITEM CONTROL AREAS, AND CUSTODIANS

12.0 Regulatory Intent

The intent of Title 10 of the Code of Federal Regulations (10 CFR) 74.43(b)(9) is to ensure that 

the material balance areas (MBAs) and item control areas (ICAs) designated by licensees will 

enable them to identify inventory differences and item locations on a scale smaller than that of 

the entire plant. Regulations in 10 CFR 74.43(b)(9) require licensees to designate MBAs and 

ICAs and assign custodial responsibilities for these areas to provide internal controls to deter or 

detect any diversion or misuse of special nuclear material (SNM) at the licensee’s facility. 

12.1 Material Control Boundaries

The material control and accounting (MC&A) plan should describe how the licensee establishes 

various material control boundaries to minimize the occurrence of, and facilitate resolution of, 

MC&A anomalies. Examples of such anomalies are inventory differences, missing items of 

SNM, and potential theft or diversion of SNM. 

Because MBAs and ICAs are important foundations for controlling and accounting for all SNM in 

a facility, the MC&A plan should describe the process for how their locations are chosen. An 

MBA or ICA should correlate to physical or administrative boundaries and monitored locations. 

The MBA or ICA should be designed to limit losses to a specific area, i.e., the MBA should not 

be so large that the licensee cannot localize inventory or process differences to a manageable 

level. Materials transferred into and out of an MBA or ICA must be subject to quantitative 

measurements, as specified in the definitions of MBAs and ICAs in 10 CFR 74.4, “Definitions.”

12.2 Custodians

The MC&A plan should describe the roles and responsibilities of the custodians for MBAs and 

ICAs. Each custodian should have direct interaction with the MC&A organization, and such 

individuals should be located within the physical operations area. Custodians who are 

responsible for more than one MBA or ICA should not have the authority to make material 

transfers between MBAs or ICAs that are both under their direct control.

12.3 Commitments and Acceptance Criteria

In its MC&A plan, the licensee should provide definitive commitments that adhere to the 

regulatory requirements and meet the acceptance criteria applicable to the designation of 

MBAs, ICAs, and custodians. A finding that the licensee’s MC&A plan for designating MBAs, 

ICAs, and custodians is acceptable and in accordance with 10 CFR 74.43(b)(9), will be based 

on, but not limited to the following acceptance criteria:

• MBAs and ICAs should have defined physical and administratively controlled areas that

allow for the physical and administrative control of nuclear materials such that the 

quantity of nuclear materials being moved into or out of the MBA is a 

measurement-based assigned value for element and isotope contents.
NUREG-2159 62

• MBAs and ICAs are established in such a way as to minimize the occurrence of, and 

facilitate the resolution of, MC&A anomalies.

• MBA and ICA structures are properly documented and clearly described, including 

physical boundaries and categories of material in the individual MBA or ICA. 

• Custodial responsibilities are assigned for each designated MBA and ICA.

• Custodians responsible for more than one MBA or ICA are not tasked to transfer 

material between MBAs and ICAs under their control.
63 NUREG-2159

13. RESOLVING INDICATIONS OF LOSS, THEFT, DIVERSION OR 

MISUSE OF SPECIAL NUCLEAR MATERIAL

13.0 Regulatory Intent

The intent of the general performance objectives in Title 10 of the Code of Federal Regulations

(10 CFR) 74.3(b) and (c) is that licensees be able to promptly investigate and resolve any 

indications of a possible loss, theft, diversion, or misuse of special nuclear material (SNM),

whether arising from errors or deliberate actions. 

13.1 Methods and Procedures for Identifying Indicators

The material control and accounting (MC&A) plan should discuss the means by which the 

licensee will resolve indicators of a possible loss, theft, diversion, or misuse of SNM. The 

licensee’s resolution program should address the possible indicators of missing SNM. The 

MC&A plan should enumerate all the potential indicators that can be postulated and develop 

resolution procedures for each. Any anomaly could potentially be an indicator of loss, theft, 

diversion, or misuse of SNM. An anomaly is an unusual observable condition (such as 

excessive discrepancies, missing items, broken tamper-indicating devices, or other possible 

indicators) that might result from theft, diversion, or other misuse of SNM. The terms “indicator”

and “anomaly” may be used interchangeably to describe a condition that may require further 

investigation to determine if an actual loss, theft, diversion, or misuse of SNM occurred. 

The following are examples of possible indicators of missing SNM:

• lack of agreement between a physical inventory and its associated book inventory in 

which the inventory difference (ID) is positive and exceeds three times the standard error 

of the inventory difference (SEID) and more than 300 grams of uranium-235 (235U) or 

200 grams of plutonium or uranium-233 (233U)

• determination through the item control system that one or more items are not in their 

designated locations and the actual locations are not immediately known

• discovery that an item's integrity or its tamper-indicating device (TID) was compromised

• information from the process control system indicating potential loss of material from the 

process system

• an allegation of theft or diversion

13.2 System and Procedures for Investigating and Resolving Loss Indicators

One or more MC&A procedures should address the system and practices for investigating and 

resolving loss indicators. The licensee should have well defined procedures for promptly 

investigating and resolving indications of possible missing SNM and procedures for rapidly 

determining if an actual loss of SNM has occurred. These procedures should include criteria for 

determining when to conclude an investigation of loss indicators. 

Resolving a loss indicator means that the licensee has made a determination that loss, including 

possible diversion or theft, has not occurred and is not occurring. For each type of indicator, the 
NUREG-2159 64

licensee should develop detailed resolution procedures and should describe or outline them in 

the MC&A plan. 

Any investigation of an indication of a loss or theft should provide, whenever possible, (1) an 

estimate of the quantity of SNM involved, (2) the material type or physical form of the material, 

(3) the type of unauthorized activity or event detected, (4) the time frame within which the loss 

or activity could have occurred, (5) the most probable cause(s), and (6) recommendations for 

precluding reoccurrence.

For indications that a loss or theft may have occurred, the resolution process should include 

(1) thoroughly checking the accountability records and source information, (2) locating the 

source of the problem, (3) isolating the exact reason for the problem within the area or 

processing unit, (4) determining the amounts of SNM involved, and (5) making a determination 

that the indication is or is not resolved. The licensee should prepare the resolution procedures 

in such a manner that no individual who could have been responsible for the potential loss also 

would be responsible for its resolution. If an investigation of an indicator results in a conclusion 

that the indication is true, such conclusion must be reported to the U.S. Nuclear Regulatory 

Commission (NRC) within 1 hour of its determination pursuant to 10 CFR 74.11, “Reports of 

Loss or Theft or Attempted Theft or Unauthorized Production of Special Nuclear Material.” The

MC&A plan should specify the time allowed for resolution. In general, a time not exceeding 

72 hours should be adequate.

13.3 Response Actions for Unresolved Indicators

Response actions to unresolved indicators should be clearly defined and should be on a graded 

scale appropriate to the level of potential safeguards significance. Licensees also should define

the responsibility and authority for initiating and executing such escalating levels of response 

actions.

For indicators of missing SNM, the level of safeguards concern is related to such factors as: 

• the potential quantity of SNM involved

• the material attractiveness of the potential missing uranium or plutonium (in terms of 

fabricating a nuclear explosive device) relative to its type, enrichment, composition, or 

form (e.g., U metal, U3O8, uranyl nitrate solution, UF6, scrap, or waste)

13.4 Documentation Requirements

The MC&A plan should identify all documentation requirements associated with the licensee’s 

program for the reporting, investigation, and resolution of missing SNM indicators. Review and 

approval requirements and document custodial responsibility also should be defined. As a 

minimum, the plan should include documentation of the following:

• investigation procedures

• resolution procedures

• reporting of indicator to MC&A management, including date and time the indicator was 

reported, name of individual who discovered the indicator, and description of indicator
65 NUREG-2159

• investigation findings and conclusion, including resolution status, date issued, name and 

signature of principal investigator, and approval signature of MC&A manager

• reports made to the NRC for unresolved indicators and for indicators determined to be 

real, including date and time the report was made, method of communication, and name 

of the NRC individual contacted

Section 14.3 of this document provides additional types of information that may be necessary. 

13.5 Commitments and Acceptance Criteria

In its MC&A plan, the licensee should provide definitive commitments that adhere to regulatory 

requirements and meet the acceptance criteria applicable to investigating and resolving 

anomalies indicating possible missing SNM. A finding that the licensee’s MC&A plan for 

resolving indications of loss, theft, diversion, or misuse of SNM is acceptable and in accordance 

with 10 CFR 74.3(b) and (c), will be based on, but not limited to, the following acceptance 

criteria:

• Adequate commitments are provided to ensure a high probability that any indicator of 

missing SNM will be (1) recognized as an indicator, (2) investigated, and (3) resolved.

• A prompt investigation will be conducted by the licensee for all indications of possible 

loss, theft, diversion, or misuse of SNM.

• A cause or probable cause that is based on objective evidence will be assigned to each 

indication of possible loss that is investigated by the licensee.

• Investigation and resolution procedures will provide for adequate overchecks to ensure 

that no individual who could have been responsible for a possible loss or theft of SNM 

would be the sole or primary individual responsible for resolving the indicator.

• No investigation relative to an indication of a loss or theft of SNM exceeding the current 

significant quantity (SQ) shall be declared as completed but unresolved without first 

conducting a shutdown, cleanout inventory in which all unsealed SNM is remeasured for 

element and isotope contents.

• The results of all investigations of alleged thefts, and any indications of a loss of SNM 

that remain unresolved after 30 calendar days, will be reported by the licensee to the 

appropriate NRC MC&A licensing authority.

67 NUREG-2159

14. INFORMATIONAL AID FOR ASSISTING IN THE INVESTIGATION 

AND RECOVERY OF MISSING SPECIAL NUCLEAR MATERIAL

14.0 Regulatory Intent

The intent of the general performance objective in Title 10 of the Code of Federal Regulations

(10 CFR) 74.3(d) is for licensees to have ready and provide to investigators any information 

deemed relevant to the recovery of special nuclear material (SNM) involved in a loss or theft. 

The burden is on the licensee to provide (without being asked) all information that it recognizes 

as being relevant, as opposed to only providing information that the investigators are 

knowledgeable enough to request. This objective pertains to investigations and recovery 

operations, relating to actual (or highly suspected) events pertaining to missing SNM, which 

would be conducted by the U.S. Nuclear Regulatory Commission (NRC) and other government 

agencies, such as the U.S. Federal Bureau of Investigations. 

The 10 CFR 74.3(d) performance objective states that the licensee must be able to provide, in a 

timely manner, information to aid in the investigation and recovery of missing SNM in the event 

of an actual loss, theft, diversion, or misuse.

 

14.1 Types of Information

The kinds of information that may aid the investigation and recovery effort are:

• data or observations that led the licensee to determine that a loss or theft of uranium or 

plutonium may have occurred

• data, observations, and assessments associated with attempts to resolve the indication 

of missing material 

• the time period during which the material may have left the facility

• the path and means by which the material may have left the facility

14.2 Information Indicating Possible Losses of SNM

Information indicating that a loss of uranium or plutonium may have occurred can come from 

process or production yield data, physical inventory results, item control, and shipper–receiver 

comparisons. This information could include:

• material accountability data records and reports

• inventory records

• inventory difference and propagation of error calculations

• inventory reconciliation reports

• indications of unrecorded or unauthorized removals of SNM from storage or process 

locations
NUREG-2159 68

• reports of apparent destruction or falsification of records concerning SNM 

• records of broken tamper-indicating devices (TIDs) or compromised item integrity

• indications of unauthorized entry into SNM storage areas

• reports from monthly item status inspections

• material receipt and log records

• results from shipper–receiver difference evaluations

• process quality assurance or production control records

• documentation relating to an alleged or confirmed theft

14.3 Information on Resolving Indications of Missing SNM

Chapter 13 provides information associated with resolving indications of missing. This 

information, and information that may be of aid in the recovery of missing material, would 

include the following:

• the type of unauthorized activity detected

• the interval during which the loss may have occurred

• the amount of material and form of the material involved in the loss

• results of measures to validate indicators

• results of extended measures to resolve indicators

• results from special inventories (or re-inventories) and tests performed

• audit results of the SNM accountability source data

• assessments of measurement data and measurement controls

• results from reviews of the material control and accounting program and status of 

corrective actions

• history of indicator investigation and resolution activities

• anomaly investigation and resolution procedures and conclusions

• probable cause of the loss
69 NUREG-2159

• any abnormal events that may have contributed to or caused the loss

• the names of individuals who could have been responsible for the loss

Much of the backup information necessary to assist in an investigation would be records 

maintained in the facility records system described in Chapter 15.

14.4 Commitments and Acceptance Criteria

In its material control and accounting (MC&A) plan, the licensee should provide definitive 

commitments that adhere to regulatory requirements and meet the acceptance criteria 

applicable to providing information to assist in the investigations and recovery of missing 

uranium. A finding that the licensee’s MC&A plan for providing informational aid is acceptable 

and in accordance with 10 CFR 74.3(d), will be based on, but not limited to, the following 

acceptance criteria:

• Procedures are in place for the efficient and timely gathering of relevant information to

be provided to government investigators so as to aid them in the investigation and 

recovery activities associated with missing SNM.

• Information will be provided to appropriate government authorities to aid in their 

investigation of indications or allegations of missing material and in the recovery of SNM 

in the event of a loss that could include theft or diversion.

71 NUREG-2159

15. RECORDKEEPING

15.0 Regulatory Intent

The intent of Title 10 of the Code of Federal Regulations (10 CFR) 74.43(d) is to require 

licensees to establish and maintain records that demonstrate that the general performance 

objectives of 10 CFR 74.3 and the requirements of 10 CFR 74.43, “Internal Controls, Inventory, 

and Records,” and 10 CFR 74.45, “Measurements and Measurement Control,” have been met. 

In accordance with 10 CFR 74.43(d), records must be retained for a minimum of 3 years (or 

longer if specifically required by 10 CFR Part 75, “Safeguards on Nuclear Material—

Implementation of US/IAEA Agreement,”). Note that, in accordance with 10 CFR 74.19(b), 

material control and accounting (MC&A) procedures (as documented in licensee records) must 

be retained until the Commission terminates the license. Records should include those 

documenting the following information:

• receipt, shipment, disposal, and current inventory of the special nuclear material (SNM)

held under license

• quantities of SNM added to and removed from process

• shipper–receiver evaluations associated with SNM receipts.

Records provide a means for assessing the performance of the MC&A system and inspecting 

for compliance with regulatory requirements. 

15.1 Description of Records

The MC&A plan should identify all records, forms, reports, and standard operating procedures 

that show compliance with the requirements of 10 CFR Part 74, “Material Control and 

Accounting of Special Nuclear Material.” Such records should include, but are not limited to, the 

following:

• documents that define changes in the MC&A management structure or changes 

in responsibilities relating to MC&A positions

• procedures pertaining to any accountability-related measurement or sampling 

operation

• forms used to record or to report measurement data and measurement results, 

including source data

• forms and notebooks used to record calibration data associated with any 

accountability measurement system

• forms and notebooks used to record quantities, volumes, and other data 

associated with the preparation of standards, both calibration and control, used in 

connection with accountability measurement systems

• forms and official memos used to record or report measurement control program 

data, control limit calculations, and out-of-control investigations

• forms listing and providing instructions associated with physical inventories
NUREG-2159 72

• forms and formal worksheets used in the calculation of standard error of the 

inventory difference (SEID), inventory difference (ID), and active inventory values

• ledgers, journals, and computer printout sheets associated with the accountability 

system

• ledgers, journals, and computer printout sheets associated with the item control 

program, including tamper-indicating device(TID) usage and “attesting to”

records

• U.S. Department of Energy/U.S. Nuclear Regulatory Commission (NRC) Forms 

741 and 742 and NRC Form 327

• forms, memos, and reports associated with identification of, investigation of, and 

resolution of significant shipper–receiver differences (SRDs)

• loss indication and alleged theft investigation reports

• investigation reports related to excessive IDs

• official reports containing the findings and recommendations of MC&A system 

assessments and any letters or memos on response actions to assessment team 

recommendations

• forms used for recording data associated with the item monitoring program

• monitoring program status or summary reports

• records of training sessions, including date given, topics covered, name of 

instructor(s), names and signatures of those attending

• training, qualification, and requalification reports and records

Licensees should list examples of MC&A forms to be retained in the MC&A plan annex or 

appendix. The retained records and reports should contain sufficient detail to enable NRC 

inspectors to determine that the licensee has implemented the program and plan capabilities of 

10 CFR 74.43 and 10 CFR 74.45 and has met the general performance objectives of 

10 CFR 74.3.

15.2 Program and Controls for Ensuring an Accurate and Reliable Record System

The MC&A plan should describe the controls used to ensure that records are accurate and 

reliable.

The record system also should provide a capability for easy traceability of all SNM transactions 

from source data to final accounting records.
73 NUREG-2159

The following topics should be addressed:

• the auditing system or program to verify the correctness and completeness of 

records

• the overchecks and balances for preventing or detecting missing or falsified data 

and records

• the plan for reconstructing lost or destroyed SNM records

• the access controls used to ensure that only authorized persons can update and 

correct records

• the protection and redundancy of the record system such that any act of record 

alteration or destruction will not eliminate the ability to provide a complete and 

correct set of SNM control and accounting information needed to achieve the 

performance objectives of 10 CFR 74.3.

15.3 Commitments and Acceptance Criteria

In its MC&A plan, the licensee should provide definitive commitments that adhere to the 

regulatory requirements and meet the acceptance criteria applicable to recordkeeping. 

A finding that the licensee’s MC&A plan for recordkeeping is acceptable and in accordance with 

10 CFR 74.43(d), will be based on, but not limited to, the following acceptance criteria:

• Access to MC&A information will be controlled to provide deterrence and detection of 

theft, diversion, misuse, or radiological sabotage involving SNM.

• A record retention system is maintained for those records necessary to show that the 

MC&A system requirements of 10 CFR 74.43(d) have been met. Licensees should 

retain such records for at least 3 years, unless a longer retention time is specified by 

10 CFR 74.15(b), by 10 CFR Part 75 or by a specific license condition. The records 

referred to in 10 CFR 75.22, “Accounting Records,” and 75.23, “Operating Records,” and 

generated during any period in which the facility is under International Atomic Energy 

Agency (IAEA) safeguards will be retained for at least 5 years. Licensees will retrain 

and maintain current versions of the following records for at least 3 years:

o management structure, MC&A job descriptions, and MC&A policies and 

procedures

o accounting source data records (Accounting source data normally consist of 

shipping and receiving forms, physical inventory forms, and the forms used for 

initially recording measurement and measurement control data. After an item is 

destroyed, the item location record needs to be retained for an additional 

14 calendar days but then may be destroyed.)

o records of shipments and receipts and investigations of significant 

shipper–receiver difference, plus the information used to resolve them

o measurement data for receipts, shipments, discards, and inventory 
NUREG-2159 74

o calibration of measurement systems, measurement control data, bias estimates, 

and the statistical analyses of the measurement control data

o data used to demonstrate that the measurement system performance achieves 

the SEID limits required by 10 CFR 74.45(c)(4) 

o physical inventory listings and inventory work sheets

o calculations of detection thresholds for excessive IDs of a safeguards 

significance (i.e., any ID that exceeds three times SEID and specified minimal 

quantities)

o calculations of the standard error of the ID and information used to reconcile an 

excessive ID

o reports of investigations and resolution of indications of loss of SNM

o the results of independent assessments and management action taken to correct 

any deficiencies identified 

• In accordance with 10 CFR 74.19(b), MC&A procedures (as documented in licensee 

records) must be retained until the Commission terminates the license.

• Sufficient protection and redundancy of the record system is provided so that an act of 

record alteration or destruction will not eliminate the capability to provide a complete and 

correct set of SNM control and accounting information that could be used to confirm the 

presence of SNM, resolve indications of missing material, or aid in the investigation and 

recovery of missing material.

• All SNM transactions, from source data to final accounting records, will be readily 

traceable.

• The source data will be retained in its original form until the physical inventory and any 

subsequent ID investigations have been completed. After this time, any readable 

facsimile is acceptable for the remainder of the required retention period. All other 

records may be retained as hard copy, microfiche, permanent computer readable forms, 

or other permanently readable forms.

• The records will be retrievable, sufficiently complete and detailed to permit auditing all 

parts of the MC&A system, and traceable back to original source data.

• The records of the data that are the basis of the calculated SEID will permit traceability 

to the sources of the variances caused by calibrations, bias adjustments, and random 

effects in the measurements. These records may be summaries of calibrations, bias 

tests, and variance monitoring data or control charts.

• The record system will have sufficient redundancy to enable reconstruction of lost or 

missing records so that knowledge of the SNM inventory is always available. The 

primary records, as contrasted with duplicate or backup records, will be provided 
75 NUREG-2159

security against computer failure, fire or water damage, vandalism, and access by 

unauthorized persons.

• All retained MC&A records are to be readily accessible to meet time restraints relative to 

their use. In general, the record retention system is to possess the capability to retrieve 

records used for measurement control or accountability within 24 hours if the record was 

generated within the past 12 months, and within 7 calendar days if generated more than 

12 months ago. Licensees must make physical inventory available within 24 hours for 

the latest two physical inventories. Item control records are to be retrievable in time to 

satisfy the criteria in Section 8.7.

• Overchecks or other controls, including access controls for updating and correcting 

records, are provided so as to prevent or detect errors in the records that would affect 

inventory difference and item location.

• Checks and balances are incorporated that are sufficient to detect falsification of data 

and reports that could conceal diversion of SNM, as required by 10 CFR 74.41 (c).

77 NUREG-2159

16. GLOSSARY

The following terms are defined in the context of (1) their usage in this document or (2) how they 

should be used if contained in the material control and accounting (MC&A) plans submitted 

pursuant to 10 CFR 74.41, “Nuclear Material Control and Accounting for Special Nuclear 

Material of Moderate Strategic Significance.”

ADDITIONS TO INVENTORY—Quantities of SNM, of a given material type code, added to a 

“plant” inventory and which, before such addition, were not part of the plant’s total possessed 

quantity for the material type code in question.

ANOMALY—An unusual observable condition (such as excessive discrepancies, missing items, 

broken tamper-indicating devices or other possible indicators) that might result from theft, 

diversion, or other misuse of special nuclear material (SNM).

ARTIFACT STANDARD—A container or item, of certified mass, having a size, shape, and mass 

that is representative of a particular type of process-related item or container. Weighing error 

caused by buoyancy is eliminated by the use of artifact standards for scale calibrations. 

ASSIGNED VALUE—A value for mass, volume, SNM concentration, SNM quantity, etc., 

assigned to a standard weight, standard material, etc., used for calibrating or controlling a 

measurement device or system. An assigned value may not necessarily be a certified value, 

but if it is not, it should be traceable to a certified standard. In any event, assigned value is the 

best estimate of the standard’s true value.

CERTIFIED STANDARD—A standard weight, material, device, or instrument having an 

assigned value that is guaranteed to be within specified limits by a nationally or internationally 

recognized organization (e.g., bureau, laboratory, etc.) that issues or certifies standards.

CHECK STANDARD (BENCH STANDARD, WORKING STANDARD)—A standard, not 

necessarily traceable to a primary standard, that is used routinely (e.g., daily or weekly) 

to check (or verify) the reliability of a measurement device, instrument, etc. (including those of 

accountability measurement systems). Such standards are not, however, used for the actual 

calibration or control of accountability measurement systems.

COMBINED STANDARD ERROR—An error band derived from the respective standard error 

values associated with each of two measurements (usually independent of each other) 

performed on a given material quantity. For both measurement values (of the pair) to be 

regarded as being in agreement, they must not differ from each other by more than the 

calculated combined standard error, which is normally calculated by taking the square root of 

the sum of squared individual standard errors. That is:

Combined S.E. = [(σ1)

2 + (σ2)2

] 2

CONFIRMATORY MEASUREMENT—A measurement that confirms (within measurement 

uncertainty at the 95 percent confidence level) a previously established parameter, such as net 

weight, enrichment, etc., associated with an SNM item (or SNM quantity), but which does not 

thoroughly verify the previously established element or isotope quantity assigned to such item. 

Confirmatory measurements are sometimes used as the basis for concluding that previous 
NUREG-2159 78

measurement values for plutonium, uranium (U), and 235U or 233U (or element and isotope) 

quantities are still valid.

CONTROL STANDARD—A standard that (1) is representative of the process material being 

measured, and (2) is itself measured periodically to monitor for and to estimate any bias 

associated with the measurements of the process material in question. A control standard must 

be traceable to a primary standard or to a primary reference material.

CRITICAL MATERIAL CONTROL AND ACCOUNTING (MC&A) PROCEDURES—Those 

written procedures that, if not performed correctly, could result in a failure to achieve one or 

more of the five general performance objectives of Title 10 of the Code of Federal Regulations 

(10 CFR) 74.3 and the program and plan capabilities of 10 CFR 74.41(c).

DEPLETED URANIUM—Any uranium-bearing material whose uranium isotopic distribution can 

be characterized as being (1) less than 0.700 weight percent (wt %) in combined 233U plus 235U,

and (2) at least 99.200 wt % 238U.

ENDING INVENTORY(EI)—The total-itemized quantity of SNM of a given material type code 

possessed by a “plant” at the end of a material balance period, as determined by a physical 

inventory. The EI quantity for any given material balance period is (by definition) exactly equal 

to the beginning inventory quantity for the next period.

ENRICHED URANIUM—Any uranium-bearing material that does not qualify as natural or 

normal uranium, and whose combined 233U plus 235U isotopic content is 0.725 percent or higher 

by weight, relative to total uranium element content.

INVENTORY RECONCILIATION—The adjustment of the book record quantity of both element 

and fissile isotopes to reflect the results of a physical inventory. In the broad sense, inventory 

reconciliation also includes the activities of calculating (1) the inventory difference (ID) for the

material balance period in question, (2) the uncertainty (i.e., SEID) value associated with the ID, 

(3) the active inventory for the period, and (4) any bias adjustment or prior period adjustment 

associated with the ID value.

KEY MEASUREMENT SYSTEM—Any set of designated measurement systems (of the 

licensee’s choosing) which, based on the most recent previous period, account for at least 

90 percent of the total measurement variance contribution to SEID. Included within the set of 

key measurement systems should be any system used to measure an SNM quantity (during 

inventory period) greater than 25 percent of the active inventory, regardless of its contribution to 

SEID.

MATERIAL BALANCE PERIOD—The time span to which a material balance or physical 

inventory relates.

MEASURED DISCARD—A batch or quantity of waste whose SNM content has been 

determined by measurement that (1) has been shipped to a disposal site, released to the 

environment, or stored on site, and (2) has been taken off the accounting ledgers as part of the 

current inventory of possessed SNM.

MEASUREMENT CONTROL PROGRAM—A managed program for monitoring and controlling 

both accuracy and precision of SNM accountability measurements.
79 NUREG-2159

NATURAL URANIUM—Any uranium-bearing material whose uranium isotopic distribution has 

not been altered from its naturally occurring state. Natural uranium is nominally 99.283 wt % 

238U, 0.711 wt % 235U, and 0.006 wt % 234U. However, the terms “natural uranium” and “normal 

uranium” are practically used interchangeably for nuclear materials management and 

safeguards system purposes in the use of material code 81 for source material other than 

thorium.

NORMAL URANIUM—Any uranium-bearing material having a uranium isotopic distribution that 

can be characterized as being (1) 0.700 wt % to 0.724 wt % in combined 233U plus 235U and 

(2) at least 99.200 wt % in 238U. (NOTE: All natural uranium having a 235U isotopic abundance 

in the range of 0.700 wt % to 0.724 wt % is normal uranium, but not all normal uranium is 

natural uranium.) (see NATURAL URANIUM.)

POINT-CALIBRATED MEASUREMENT SYSTEM—A measurement system in which the 

measurement value assigned to an unknown measured by the system is derived from the 

response obtained from the measurement of a representative calibration standard(s) that was 

measured along with (i.e., at the same time as) the unknown. The standard(s) must undergo all 

the measurement steps (e.g., aliquoting, sample pretreatment, etc.), and in the same manner, 

as the unknown. Point-calibrated measurement systems can be regarded as bias free, provided 

that adequate controls are in place to ensure the validity of the standard’s assigned value.

PRIMARY STANDARD—Any device or material having a characteristic or parameter (such as 

mass, uranium concentration, uranium isotopic distribution, etc.) whose value is certified (within 

a specified uncertainty) by a nationally or internationally recognized bureau, laboratory, etc., that 

issues or certifies standards.

PRIOR PERIOD ADJUSTMENT—Any correction (i.e., adjustment) to an ID value because of a 

correction applied to a component of beginning inventory after the inventory period started. 

Such corrections may be because of resolution of a shipper–receiver difference (SRD) on 

material received during a prior inventory period, correction of a recording error, etc. Because 

these types of corrections have nothing to do with current period losses or errors, and because 

the official beginning inventory value is not adjusted, an adjustment to the ID value (derived 

from the ID equation) is necessary to obtain an ID that reflects only current period activity.

RESIDUAL HOLDUP—Any depleted uranium, safeguards material, or SNM that remains within 

processing equipment (including ventilation filters and ductwork) after system draindown or 

cleanout. If, at the time of physical inventory, the total quantity of residual holdup is significant, 

such holdup must be measured (or estimated on the basis of partial measurements and 

engineering calculations) and included in the physical inventory listing. The uncertainty 

associated with a total measured or estimated residual holdup quantity must be included in the 

calculation of the SEID.

RESOLUTION OF AN INDICATOR—A definitive determination (with auditable evidence) by the 

licensee that an indicated possible theft or loss of uranium or plutonium was a false indicator.

SHIPPER–RECEIVER DIFFERENCE (SRD)—The difference between what a sending facility 

(i.e., shipper) claims was contained in a shipment (of SNM) and what the receiving facility 

claims was received, where both shipper's and receiver's values are based on measurement.

SIGNIFICANT QUANTITY (SQ) OF SNM OF MODERATE STRATEGIC SIGNIFICANCE—More 

than 1 formula kilogram (FKG) of strategic SNM, or 10,000 grams or more of 235U contained in 
NUREG-2159 80

uranium enriched to 10 percent or more, but less than 20 percent in the 235 U isotope. (Note: 

For statistical sampling plans, however, SQ is conservatively set to 1 FKG for strategic SNM 

and 10,000 grams 235U for Category II amounts of low-enriched uranium.)

STANDARD—See definitions for CERTIFIED STANDARD, CHECK STANDARD, CONTROL 

STANDARD, PRIMARY STANDARD, and STANDARD REFERENCE MATERIAL.

STANDARD DEVIATION—The random error (at the 67 percent confidence level) associated 

with a single value of a data set, which in turn is also a measure (or indication) of the precision 

relating to a set of measurements (or set of data) concerning the same item or sample of 

material. Standard deviation is calculated as follows:

standard deviation = S = 

where

n = number of measurements performed

xi = the value obtained for the i th measurement for i = 1, 2, 3 

.......n

 ̄x =the average value for all n measurements

STANDARD ERROR—The random error (at the 67 percent confidence level) associated with 

the average, or mean, value of a data set derived from repetitive determinations on the same 

item or sample. Mathematically, standard error is the standard deviation divided by the square 

root of the number of individual measurements used to derive the mean value.

STANDARD REFERENCE MATERIAL—A material or substance that qualifies as a primary 

standard and whose concentration with respect to a nuclide or isotope, a chemical element, or 

chemical compound is certified within a specified uncertainty.

SYSTEMATIC ERROR—A unidirectional error that affects all members of a data set. The terms 

“bias” and “systematic error” are often interchanged. However, any determined bias (i.e., a bias 

estimated from control standard measurements) has an uncertainty value associated with it. 

Thus, after correcting for any estimated bias, the uncertainty of that bias can be regarded as a 

systematic error. If an estimated bias is not applied as a correction, the combination of the bias 

plus its uncertainty should be regarded as the systematic error.

VERIFICATION MEASUREMENT—(1) A nondestructive assay (NDA) measurement of an item 

conducted to verify that a previous NDA measurement value for isotope content of that item is 

still valid. (2) The re-weighing and re-sampling of an item, batch, lot, or sublot and performing 

chemical assays of the re-sample for element and isotope concentrations so as to verify a 

previously measured value for element and isotope content of the item (batch, lot, or sublot). 

Verification is achieved if the original and verification measurement values (for element and 

isotope quantities) agree within the range of measurement uncertainty (at the 95 percent 

confidence level).
81 NUREG-2159

17. REFERENCES

International Atomic Energy Agency (IAEA), IAEA Safeguards Statistical Concepts and 

Techniques, 4th revised edition, 1989, Vienna, Austria.

NUREG/BR-0096, “Instructions and Guidance for Completing Physical Inventory Summary 

Reports (NRC Form 327),” October 1992.

NUREG/BR-0006, “Instructions for Completing Nuclear Material Transfer Reports (DOE/NRC 

Forms 741, 741A, and 740M),” Revision 7, February 2000.

NUREG/BR-0007, “Instructions for the Preparation and Distribution of Material Status Reports 

(DOE/NRC Forms 742, and 742C),” Revision 6, February 2000.

NUREG/CR-2078, “Handbook of Nuclear Safeguards Measurement Methods,”

September 1983.

NUREG/CR-4604, “Statistical Methods for Nuclear Material Management,” December 1988.

NUREG/CR-5550, “Passive Nondestructive Assay of Nuclear Materials,” March 1991.

NUREG/CR-0602, “Active Nondestructive Assay of Nuclear Materials,” January 1981.

TID-26298, “Statistical Methods in Nuclear Material Control,” 1973.

Title 10 of the Code of Federal Regulations (10 CFR) Part 74, “Material Control and Accounting 

of Special Nuclear Material,” Subpart D, “Special Nuclear Material of Moderate Strategic 

Significance.”




UNITED STATES 

NUCLEAR REGULATORY COMMISSION

WASHINGTON, DC 20555-0001

--------------------

OFFICIAL BUSINESS
NUREG

-2159

Draft

Acceptable Standard Format and Content for the Material Control and 

Accounting Plan Required for Special Nuclear Material of Moderate

Strategic Significance