Regulatory Guide 5.13

Conduct of Nuclear Material Physical Inventories

ML003740048
Person / Time
Issue date:	11/30/1973
From:	Office of Nuclear Regulatory Research
To:
References
RG-5.13
Download: ML003740048 (13)

November 1973 U.S. ATOMIC ENERGY COMMISSION

REGULATORY GUIDE

DIRECTORATE OF REGULATORY STANDARDS

REGULATORY GUIDE 5.13 CONDUCT OF NUCLEAR MATERIAL

PHYSICAL INVENTORIES

TABLE OF CONTENTS

Page

A. INTRODUCTION

............................................................. 5.13.3

B. DISCUSSION

................................................................ 5.13-3

1. Measured Physical Inventory ................................................. 5.13-3 a. Inventory Measurements ................................................. 5.13.3 b. Acceptability of Previous Measurements ............. 5.13.4 c. In-Process Measurements ............................ 5 .13.5

2. Inventory Organization and Planning ..................................... 5.13-7 a. Assignment of Responsibilities ............................................ 5.13.7 b. Cutoff Procedures ...................................................... 5.13.7 c. Inventory Instructions .................................................. 5.13-7

C. REGULATORY POSITION

..................................................... 5.13.7

1. Measured Physical Inventory ................................................. 5.13.7 a. Inventory Measurements ................................................. 5.13.7 b. Acceptability of Previous Measurements ..................................... 5.13.8 c. In-Process Measurements ................................................. 5.13-9

2. Inventory Organization and Planning ........................................... 5.13-9 a. Assignment of Responsibilities ............................................ 5.13-10

b. Cutoff Procedures ...................................................... 5.13-10

c. Inventory Instructions .................................................. 5.13-11 d. Preliminary Inspection and Review ......................................... 5.13-12

3. Conduct of Inventory ...................................................... 5.13-13

4. Post-inventory Activities .................................................... 5.13-13 a. List and Tag Accuracy Check ............................................. 5.13-13 b. Cutoff Verification ..................................................... 5.13-13 c. Inventory Summary and Reconciliation ..................................... 5.13-13 d. Final Report .......................................................... 5.13-14 REFERENCES .................................................................. 5.13-14 USAEC REGULATORY GUIDES Copla of rqb6dNd guk. ,my 1Wobtlned by rurnuest th dhlom OidWmlq dusirmd so Ow US. Atomic ECm*ry C,,omfmibon. Waiungtoln. Dr.. 20545.

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REGULATORY GUIDE 6.13.

CONDUCT OF NUCLEAR MATERIAL

PHYSICAL INVENTORIES

A. INTRODUCTION

into or out of an area, e.g., receipts, shipments, and discards, should be measured. These componentsvare not Part, 70 of Title 10 of the Code of Federal within the scope of this guide except as they affect the Regulations requires licensees authorized to possess remaining material balance component, i.e., that more than 350 grams of contained U.235, U-233, or material remaining on inventory at the close of an plutonium to conduct a physical inventory of all special acdbunting period.

nuclear material In his possession at intervals not to exceed 12 months. Licensees authorized to possess more (1) Precision and Accuracy. Constraints are than one effective kilogram of special nuclear material specified in 10 CFR Part 70 for the limits of error of the are required to conduct measured physical inventories of miterial balance. The limits of error of the respective their 1special nuclear materials more frequently than components of the material balance combine to produce annually depending on the materials. Further, these the total material balance limits of error, or limits of licensees are required to conduct their nuclear material error of material unaccounted for (LEMUF). The physical inventories in compliance with specific precision and accuracy needed for specific inventory requirements set forth In Part 70. licensees possessing m~asurements can be determined only in the context of material for use in the operation of a nuclear reactor, as a Specific plant, process, or material balance relative to4 sealed sources, or as reactor-irradiated fuels involved in the LEMUF limits specified in 10 CFR. Part 70. If the research, development, and evaluation programs in inventory limits of'error are large in relation to the other facilities other than irradiated fuel reprocessing plants component limits of error, their effect on the LEMUF

are exempted from these latter requirements. for the total balance will be greater. Consequently, to meet the LEMUF limits specified In' I0 CFR Part 70,

This guide describes measured physical inventory some of the random and systematic errors associatea procedures which arc acceptable to the Regulatory staff with the inventory measurements may need to be with respect to compliance with the physical inventory relatively smaller for inventory quantities which make requirements set forth in 10 CFR Part 70. up relatively large portions of the total. Similarly, the measurement of a portion of the inventory with a

B. DISCUSSION

relatively small special nuclear material content may be less precise than a portion having a relatively large I. Measured Physical Inventory special nuclear material content. For example, the inventory measurement of the residual material in a a. Inventory Measurements. Assurance against piece of cleaned-out equipment can be less precise than undetected loss or diversion of special nuclear material the inventory measurement of the material In the same can be achieved only by a measured physical inventory. piece of equipment that has not been cleaned out for Various systems of physical protection can be employed inventory and still contains a significant quantity of to protect against, deter, or detect theft or diversion of special nuclear material.

special nuclear material. Various systems of material control and accounting can be employed to accoudt for fhe accuracy of inventory measurements the material. However, a material balance based on a may not affect the limits of error of the material balance measured physical. inventory that provides conclusive but can affect the 4MUF, i.e., whether a balance Is evidence of the physical presence of the material is the achieved. The effect of the accuracy of inventory only means for assuring that the physical protection and measurements will depend on the quantity involved and material control and accountability systems have been the magnitude of the inaccuracy. To carry this to the effective and that no significant losses or diversions have extreme, a quantity of material that is not measured and gone undetected. not included in the balance can be considered to bl totally inaccurate. If such a quantity of material were It is only when all significant components of large, the MUF thus would be increased significantly and the material balance are measured that the balance has might exceed the LEMUF. If such a quantity were small, meaning in assuring that material has not been lost or for example, the residue in a cleaned-out piece of stolen. For a material balance to be a credible indication equipment, the effect on MUF might not be significant.

of the effectiveness of a material control system, the Static material, i.e., material which has not quantities of material on inventory must be measured for the balance or assurance provided that prior been processed or remeasured during a material balance measurements remain valid. The components of a interval does not affect the LEMUF of the material material balance involving the movement of material balance for that interval. The requirements as stated in

5.13-3

10 CFR Part 70 set limits on the LEMUF only for that original materials or the final mixture had been lost or material that was "in process"' during a material diverted. There is no way to determine this by balance interval. Any covariance effects of that "in calculation. It can be determined only by measuring the process" inventory, such as measurement uncertainties actual mixture on inventory. Conversely, if there is a of static Inventory, would be eliminated from the measured quantity introduced into a process vessel and a LEM UF calculations. It is beyond the scope of this guide measured quantity is removed from the vessel the to deal with covariance. This will be treated in other calculated remainder is the correct value only if there regulatory guides with respect to inventory as well as to has been no other removal or loss. Again, the absence of other components of the material balance. Other removal or loss cannot be determined by calculation, only by measurement of the remaining

(2) Measurement Control and Quality material. On the other hand, calculated values derived Assurance. Control of measurements made specifically from a representative sample of a weighed quantity of for inventory purposes is necessary to assure valid material negate the possibility that a loss or theft of measurements and to permit determination of the limits material has gone undetected.

of error associated with such measurements. Many inventory measurements will be so controlled because (4) Scrap and Other Heterogeneous Material.

they will have been made prior to the inventory as Special nuclear material inventory in scrap or other routine material accounting measurements. The use of heterogeneous material not amenable to sampling or prior measurements is discussed in section B.l.b. other conventional measurement techniques often is a major contribution to an unacceptable LEMUF or MUF

(3) Factors, Nominal Values, and Calculated for a material balance. This is mostly because scrap and Values. By their nature, factors such as the special waste measurements normally are less precise and less nuclear material content of a process intermediate, accurate than other special nuclear material nominal values such as the stoichiometric value for a measurements. Keeping the quantities of scrap and waste compound or the target isotopic composition of a on inventory small will assist in minimizing the effect of process material, and calculated values such as these imprecise measurements. A scrap recovery by-difference values or values based on mixing campaign just prior to the physical Inventory is one way calculations depend on steady-state or normal to accomplish this. Routine continuous recovery of operations. Perturbations such as unknown losses, scrap probably would be better.

substitution of materials, or diversion invalidate the use of factors, nominal values, and calculated values as b. Acceptability of Previous Measurements. The accurate representations of special nuclear material measured physical inventory will consist of measured element and isotopic values for purposes of a measured values of many types and from many different sources.

physical inventory. Previous measurements may be used for special nuclear material inventory valueL .The source of such data, the Measurement precision for factors controls imposed on the generation of the data, and the normally produce limits of error that are somewhat wide controls imposed on the material to which the data so that the use of factors and their associated limits of apply will determine the integrity of the data as error may result in exceeding the limits for the material acceptable inventory values.

balance as specified iti 10 CFR Part 70.

Nominal values are not the result of Integrity of the data means that the data measurements sufficient to be acceptable as physical correctly reflects the quantity of special nuclear material inventory measurements. Limits of error for nominal involved. A primary means for assuring the integrity of values cannot be determined because of the lack of the prior measurement data for a quantity of special nuclear material.is tamper-saflng. It is defined in 10 CFR

sufficient measurements.

Part 70 as:

While calculated values usually result from the combination of one or more measured values, there "...the use of devices on a container or vault In a often is an unmeasured component that invalidates the manner and at a time that ensures a clear indication calculated value.-For example, two measured quantities of any violation of the integrity of previously made are mixed to provide a batch of material. The calculated measurements of special nuclear material within the special nuclear material values would be the sum of the container or vault."

two mixed quantities provided none of either of the The requirements for tamper-safing in

10 CFR Part 70 are intended to assure against the undetected occurrence of such things as unauthorized or

'As defined In IOCFl Part 70, Material in Procen means unrecorded removal of portions of material from a any special nuclear matezial posessed by a licensee except In container, removal of containers or items containing unopened tecelp^ sealed sources, and ultimate product special nuclear material from a vault, or substitution of maintained under tamper-safin&. items or quantities of different materials which would

5.134

cause prior measurement data to be incorrect. absence of a significant amount of special nuclear Tamper-safing is not intended to prevent such material in such equipment is not verified.

occurrences but to give a clear indication that such an occurrence might have taken place and that a previously (2) Dynamic *Inventories. To eliminate, or

~ measured special nuclear material value may no longer minimize, the disruptive effect of shutdown and be correct. cleanout or draindown inventory procedures, dynamic inventory techniques could be considered. Such Tamper-safing can be used to reduce techniques include any inventory procedures which inventory measurement of in-process intermediates in permit the process to continue to run during inventory, storage at inventory time when process measurements i.e., remain in a dynamic state. Some techniques m:ay provide a valid measure of the element and isotopic require changes in processing procedures which will content of such material. When it is expected that such result in reduction of process throughput but not to the intermediates will be in storage at the end of a material extent of cleanout or draindown. Four techniques are balance period they can be placed in storage under described here. Specific application will depend on the tamper-safe conditions using the appropriate process facility and process. Other regulatory guides will measurements and identification. consider some of the specifics of these techniques.

c. In-Process Measurements. The extent to which (a) Process Blank. This technique i0

a process must be shut down, drained down, or-cleaned particularly applicable to batch-type processes where it out to measure inventory quantities of special nuclear is feasible to separate batch flow and insert a blank, i.e..

material will depend on the quantity of special nuclear a batch containing no SNM (batch blank) or to clean out material in the equipment at any stage of operation,' the equipment slepwise as the process procerd%

cleanout, shutdown, etc. and the precision and accuracy (cleanout blank). The technique also could be applied 1;)

with which such material can be measured. The critical a continuous-flow process. but the introduction of the parameter is the limit of error of the process quantity blank and maintaining segregation of the blank from the measurement, in absolute terms, and its effect on the normal process flow are more difficult.

total material balance uncertainty. These absolute limits of error become a significant factor when there are large The technique involves' invenioryilig quantities of special nuclear material in in-process all SNM not held tinder tamper-safing and not in the inventory measured with relatively imprecise techniques. process line at a given time To. This could include raw They become less significant as the quantities of material awaiting processing, process-generated scrap oir in-process inventory decrease or the quality of the recycle, and product. The process is inermiipted measurements improve. There are several techniques for following the batch in the first step of the prm:exss ait measuring in-process inventory which involve various time To either to clean out the first step of the process combinations of measurements and inventory quantities. or to introduce a batch containing no SNM. In a dry process the technique probably would call for cleanouit (I) Process Draindown and eanout. Process of the step (cleanout blank). In a liquid process the draindown and- cleanout are relative terms which technique could include introduction of all (it' the indicate degrees of removal of special nuclear material ingredients of the batch except the SNM (batch blank i.

from process equipment. Draindown implies moving the Separation between the batch blank and the precedinig bulk of the special nuclear material to measurable points and the following batches is maintained to avoid in the process but not necessarily cleaning out the off-specification product and to permit measuring process equipment. Cleanout implies a more rigorous residual SNM in the equipment after the batch blank.

effort to remove the material from the process equipment so that it may be considered to contain no As the process proceeds, each separable residual special nuclear material. Whatever the degree of step of the process is treated by cleanout blank or batch removal, the procedure is essentially the same. The blank processing. Raw material previously inventoried at special nuclear material is moved from its normal process time To can be introduced into the -process after location to a location and form in which it can be equipment in the first process step has been cleaned out measured. The location may be a calibrated process or the batch blank has cleared the step. If either case the vessel or it may be bottles or containers separate from residual SNM in the equipment is measured, either after the process. cleanout or after the batch blank has passed, to assure that the equipment is clean or to add the SNM quantity Residual quantities in equipment under to th**ý inventory. As discussed in section B.lc.(l), such draindown conditions, rather than cleanout conditions, residual quantities of SNM involved will be small in normally will be larger and will require measurement relation to the total balance.

with better precision and accuracy than smaller cleanout residues. While equipment that has been cleaned out As the blank proceeds through the process, could be considered to contain no special nuclear there may be SNM-bearing material generated as scrap or material, there is the danger of inflating the MUF if the recycle material. Such material generated in front of and

5.13-5

during the blank processing and after time To is calculations show how much of each type of material is segregated from such material generated in the process present until the output becomes entirely the second before time To and from such material generated after type. The inventory that was in the process when the the blank. The SNM content of these materials generated second type was introduced can then be calculated.

In front of and during the blank processing and after References I and 2 discuss the results of two time To is measured and added to the inventory taken as experiments using minor isotope ratios for in-process of time To. Measurement of such material could be in inventory in a chemical reprocessing plant.

the form of a short scrap recovery campaign immediately following the inventory. If the isotopic ratios do not or cannot be varied to provide the step function of two As processing proceeds, product is identifiably and measurably different materials, a tracer generated until the blank reaches the end of the process may be added to the second type of material. The and the last step of the process sees the cleanout or additive will depend on the process and subsequent use batch blank at time T1 . Such product is measured and of the product. A tracer that would be removed in added to the inventory taken at time To. Product, scrap, subsequent treatment or a tracer that would be and recycle generated in front of and during the blank acceptable in the finished product could be used. For processing from time To to time T, is kept segregated example, a volatile tracer that would be removed in a from such material inventoried at time To to ensure that subsequent calcining step or a tracer that would not no quantity of material is inventoried more than once. precipitate or extract with the SNM could be used.

Tamper-sating and inventory identification tags can be used to accomplish such segregation if it cannot be done (c) Counter-Current Inventory. The basic by actual physical segregation. principle of this technique involves movement of the inventory-taking team counter-current to the process The inventory at time To thus would flow. As.the material moves past the inventory team, or consist of: vice versa, the inventory is measured, counted, recorded, etc. This technique is best applied to processes or parts i. SNM in raw material, scrap, recycle, and of processes in which the SNM is contained in discrete product on inventory but not in the process items, such as fuel pins, pellets, or containers of material line at time To. such as furnace trays or bottles of process intermediates.

ii. SNM in scrap, recycle, and product generated in (d) Process Parameter Measures. This type front of and during the blank processing of inventory involves measuring the special nuclear between time To and time TI, including the SNM content of the batch blank, if any; and material essentially in situ in the process with little or no interruption of the process. Application of this K)

technique depends on plant and equipment design iii. Residual SNM in each step of the process considerations for equipment calibration, process flow equipment after the blank has passed and control, and instrumentation for measuring process before the following SNM is introduced. parameters such as temperature, flow rate, concentration, specific gravity, and those related to (b) Tracer or Step Function. To avoid the various radiometric nondestructive assay techniques.

necessity of shutdown and cleanout or even the Other regulatory guides will address some of the introduction of a blank, the introduction of a tracer or specifics of such design considerations.

step function is particularly suitable for liquid continuous processes such as the recovery of SNM from The ultimate for this technique would spent reactor fuel or a scrap recovery process. The be a fully instrumented process with a series of in-line technique involves displacing the SNM inventory in the Instruments and gauges. Readings from such process with SNM identifiably and measurably different instrumentation would be taken at a given time or over a from thatin the process. It may not be the SNM that is specified time interval in an appropriate sequence. The different but the solvent or an addition of tracer to the inventory at the specified time would then be calculated solution. The" displaced material can be measured from the recorded parameters. While the ultimate would quantitatively in the subsequent output and product be to apply this technique to an entire process, the from the process along with the displacing material until practical would be to select parts of the process the inventory has all been displaced as evidenced by the amenable to the technique, especially those most output measurements. difficult to shut down and start up. While the technique employs more advanced technology and requires design One application of this technique has considerations, it could eliminate, or at least reduce, been tested in a reprocessing plant by displacing the costly plant shutdown or draindown.

in-process inventory of known minor isotope ratios with another batch of material having different minor isotope Flow measurements through an ratios. From the minor isotope ratios of the output, isolatable step of the process coupled with some measure

ýIlj

5.13.6

of concentration such as specific gravity or gamma removed from process. This will facilitate calculations of absorption could provide a measure of the SNM in that the separate in-process material balance required by step. Cutoff procedures are employed to assure that 10 CFR Part 70. Material types such as high-enrichment material in one such part of the process does not flow to uranium and low-enrichment uranium could be listed the next, which could cause it to be inventoried twice or separately, as could plutonium and U-233. This may be not be inventoried. Cutoff could be based on mechaniral automatic because the different materials are in different valving or other physical isolation procedures or on a MBAs, but it is possible, for example, in a mixed oxide time factor for equilibrium conditions for completion of fuel fabrication plant, to have plutonium and a given process step. low-enrichment uranium in the same MBA. Other separations may be desirable, such as sealed sources

2. Inventory Organization and Planning listed separately from tamper-safed material.

Even though the most accurate and precise methods Detailed written inventory instructions provide are used for inventory measurements, the procedures the means to coordinate the complex activities of the used in the conduct of the inventory can have a inventory to produce a valid acceptable result.

significant effect on the results. The techniques and procedures used to obtain inventory data and to process them to obtain inventory values for specific material

C. REGULATORY POSITION

type balances, material balance areas (MBAs), or total plant balances will determine the validity of the It is recognized that a variety of combinations of resultant balances. the techniques and procedures described in this guide can pertain to any given plant or material balance area.

a. Assignment of Responsibilities. Clearly defined Such combinations would need to be evaluated as to responsibilities, duties, and authorities together with their effectiveness in each such situation. Acceptable proper orientation of personnel and assurance that each techniques and procedures are not limited to those person understands his place in the inventory program described in this guide. It is expected that additional will materially assist in more rapid, trouble-free conduct inventory mechanisms will be developed as the nuclear of physical inventories. industry progresses. Combinations ofthe techniques and procedures described in this guide and that conform to b. Cutoff Procedures. A major factor in planning a the following are generally acceptable to the Regulatory physical inventory is establishing the timing of and staff for use in the conduct of a measured nuclear

, controlling the various cutoffs necessary for accurate material physical inventory.

inventories. Cutoffs or cutoff procedures are so called because, at the specified time, activities such as 1. Measured Physical Inventory movement of material or posting to the records are stopped or cut off. Each physical inventory is the ending a. Inventory Measurements. The requirements for inventory for one material balance interval and the physical inventories in 10 CFR Part 70 specify that the beginning inventory for the next material balance quantity of special nuclear material associated with each interval. The timing of the material and records cutoff is item on inventory be a measured value of the special critical to assure definition of the inventory interval for nuclear material.

given processes, material types. or material balance areas.

(I) Precision and Accuracy. Inventory c. Inventory Instructions. Nuclear material measurements should be made with precision and physical inventories are complex and involve the accuracy appropriate to the significance of the inventory interaction of many persons and activities. Not all quantities to the material balance.

materials will be inventoried at the same time. Material balance areas may be inventoried in sequence or in (2) Measurement Control and Quality parallel. For example, three plutonium MBAs may be Assurance. Inventory measurements should be subject to inventoried In sequence by one team for a material quality controls as are other special nuclear material balance inteirval of two months while three measurements. Planning for inventory measurements low-enrichment uranium material balance areas may be should include planning for the determination of the Inventoried simultaneously using three teams for a quality of such measurements. Measuring devices such as material balance interval of six months. scales and balances, measuring tanks or vessels, and nondestructive analysis (NDA) instruments should be Certain ways of preparing inventory lists may calibrated in accordance with plant quality assurance make subsequent data handling easier and more rapid. procedures. Sampling plans and procedures should be The inventories may provide for separate sheets to be supported by data showing that Inventory samples are'

used for different types of material and inventory valid and representative of the material. Analytical categories. Material that is in process as defined in methods should be those for which quality control data SIOCFR Part 70 could be listed separately from material are available for use in determining the quality of the that has been tamper-safed and considered to have been measurements.

5.13-7

(3) Factors, Nominal Values, and Calculated numbers, sample numbers, and analytical results or Values. Factors should be determined on the basis of tracing lots, containers, or items to nondestructive assay measurements, their continued validity monitored (NDA) log books. Container or item labels should through a measurements quality assurance program, and Include:

the limits of error of the factor determined through such (a) Special nuclear material quantity data, measurements. Supporting data for such factors should i.e., element and/or isotope;

be documented and verified by additional measurements (b) Lot identification;

during the inventory In a manner similar to that used to (c) Bulk quantity data, i.e., gross, tare, verify prior measurements that have not been protected and net weights or volume data; and by tamper-safing. The limits of error of each factor (d) Sample identification or NDA log should be included in the calculations of the LEMUF for book reference.

the material balance.

If such data are not included on the Nominal values are not acceptable as measured container or item label, a unique identifying number or inventory values. symbol should be affixed to each container or item, which number or symbol should be traceable to the Calculated values in which there are unknown and appropriate data as listed above. All such quantity and unmeasured components are not acceptable as inventory identification data which provides for validation of values. previously made measurements should be tamper-safed so that there is a clear indication of any changes made to

(4) Scrap and Other Heterogeneous Material. the data or identifying information.

Quantities of special nuclear material in scrap and waste should be kept relatively small. Process and inventory (2) Tamper-safing. To be acceptable, schedules should give consideration to the need for tamper.safing must be applied immediately upon recovery campaigns prior to inventories. Solving the completion of the operations which establish the special scrap measurement problem, however, should not be left nuclear material content of an item. Such operations until inventory time. A continuing scrap and waste may include the nondestructive analysis of fuel elements management and control program should be maintained. or rods that have been sealed and identified or of a series Such a program should have the primary objective of of rods or pellets which are then stored in containers or reducing the, effect of the uncertainty of scrap in a vault under tamper-saflng. They alpo may include measurement on the material balance. The objective can sampling, packaging, and weighing a lot of mgterial into be attained by: a number of containers, each of wlich is sealed with a (a) Eliminating or reducing to a minimum tamper-safe seal. Analyses may be performed later but the amount of special nuclear material on inventory in the integrity of the sample also must be protected.

such scrap or heterogeneous material;

(b) Treating, segregating, compositing, and Shipper's dta may be used for inventory packaging such material so that the special nuclear of unopened receipts provided the shipper's tamper-safe material content can be measured with precision and seals are intact, or if any items were sampled, they were accuracy appropriate to the quantity involved; or immediately tamper-safed, i.e., resealed with a (c) An appropriate combination of(a) and tamper.safe seal or placed in a tamper-safed vault.

(b) depending on the quantities involved and the measurement capabilities available. Devices to be used for. tamper-safing are the subject a separate regulatory guide.

of Regulatory Guide 5.1 I, "Nondestructive

,Assay of Special Nuclear Material Contained in Scrap (3) Remeasurement. If tamper-safing is. not and Waste," discusses the use of NDA for material employed to assure the integrity of prior measurements, accounting measurements of scrap and waste 10 CFR Part 70 requires remeasurement of the material.

components of inventory. Remeasurement, either in total or of a sample, may include weight or volume, element, and Isotope for each b. Acceptability of Previous Measurements. item remeasured. It may include use of an NDA method Quantities of special nuclear material on inventory for for each item or the selected samples of items. In any which there are previous measurement data of case the measurement must be such as to assure the total acceptable quality need not be remeasured provided the element and/or isotopic content of the items measured.

integrity of. the previous data can be assured and the For example, check-weighing of a series of containers is data are identified with the material in question. not considered sufficient verification of prior data without elmnent and/or isotopic analyse

s. Various

(1) Identification. There should be means of statistical sampling plans and statistical tests of identifying the material with the measurement data for hypotheses or tests of significance may be used to assure such data to be considered acceptable. Material that prior measurements are valid within limits of error identification 'should provide means for tracing lot applicable to the original measurements.

K)J

5.134

The application of such statistical. removed from the process after inventory so that it methodology to material control and accounting," might be inventoried a second time in a storage location, including inventory verification, is the subject of and (4) material which has already been inventoried as a separate regulatory guides. raw material or process intermediate in storage is not introduced into the process.

c. In-Process Measurements. The combination of the quantity of special nuclear material in process and (a) Process Blank Inventory. In using the quality with which such material can be measured either the batch blank or cleanout blank inventory should be considered for each process or material technique, measurements should be made to assure that balance in relation to the effect on the LEMUF for the there is no significant residue of special nuclear material balance. Combinations of in-process inventory in the equipment after the blank or, if there is %uch a techniques and measurement methods should be selected residue, to provide a measure of the quantity to be to obtain measurement limits of error as low as included in the inventory. If experience with specific practicable. The acceptability of the respective inventory procedures for a given process has shown that the techniques will depend on the procedures employed in equipment will be clean, it may not be necessary to using the techniques. verify this fact.

(I) Process Draindown and aeanout. Process (b) Tracer or Step Function Inventory.

equipment from which material has been removed Any tracer used should be homogeneously distributed in should not be considered "clean." i.e., to contain no the batch of material and should be in a concentration special nuclear material, unless measurements are made sufficient to be identifiable and measurable with to verify this. Measurements should either verify that the precision and accuracy appropriate to the quantity of residual quantity is not great enough to affect special nuclear material involved. A step function used significantly the material balance or should result in a for inventory should be of sufficient magnitude to be material quantity to be included in the inventory. If identifiable and measurable with precision and accuracy experience with specific cleanout procedures indicates appropriate to the quantity of special nuclear material that, if a specified procedure is followed the equipment involved.

will be clean, it may not be necessary to verify the cleanout. (c) Counter-Current Inventory. ('aution should be observed in this type of inventory that the While prior measurements and cleanout inventory teams do not bypass material moving past procedures are acceptable bases for concluding that a them or that they do not inventory material more than process residue contains no special nuclear material, such once. Tagging is not always possible in this type is not the case with draindown procedures. Draindown inventory but some procedures should by employed to procedures and prior measurements of residues should assure inventory accuracy. Such procedures may involve be used to establish expected quantities. inventory physical segregation or area tagging rather than item or factors, variations in holdup. and limits of error. The container tagging.

residual quantities should be measured for each inventory or measurements made to verify the validity I (d) Process Parameter Measures. This of any factors used. Such measurements of residual technique should be employed only where process quantities may be accomplished using NDA techniques equipment and instrumentation have been designed and which have been calibrated to the equipment by calibrated for in situ measurement of the special nuclear measurement and cleanout .tests at a prior time. Further, material. Measurements of this type should be more the special nuclear material quantity remaining in accurate and precise than those used for residual equipment should not be calculated as the difference material measurement because larger quantities of between the material put into the equipment and the special nuclear material are involved resulting in greater material taken out (see section I .a.(3)). effects on material balance uncertainties. Equipment and instrument calibrations and reliability should be Other regulatory guides deal with evaluated to provide data for calculating limits of error minimizing residual material holdup in equipment and for inventories of this type.

with the measurement of such material.

2. Inventory Organization and Planning

(2) Dynamic Inventories. Strict material handling controls and cutoff procedures for material 10 CFR Part 70 requires that physical inventories be movements and transfers are necessary for dynamic planned, organized, and conducted according to written inventories to ensure that: (I) material does not move inventory instructions prepared for each inventory. The through the process without being inventoried, (2) purpose of this requirement is to assure complete and material is not recycled during the inventory to cause it accurate coverage, no duplication, and minimum to be inventoried moMe than once, (3) material is not interference with plant operations.

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a. Assignment of Responsibilities b. Cutoff Procedures. The time of the inventory should be specified for each material balance so that (I) Plant Inventory Supervisor. Oneindividual a who is familiar with the areas to be inventoried and with finite material balance interval can be established. Cutoff the principles and procedures of conducting physical procedures should be established to assure that the quantity of material which results from the physical inventories of nuclear materials should be assigned inventory activity accurately represents the material primary responsibility for planning, organizing, and physically present at the specified inventory time conducting the physical inventory. and that this quantity is accurately reflected in the records at the same specified time. Material cutoff procedures The responsibilities and authority for the should be coordinated with records cutoff procedures inventory supervisor should be stated in writing to to assure that the same material balance Interval prevent misunderstanding and assist the supervisor is used for in both.

discharging his responsibilities. Specific statements should be included for the inventory supervisors authority with regard to process shutdown, startup, (I) Receipts, Shipments, and Other Removals.

interruption, and control preceding, during, For the given material type which is to be inventoried, and the inventory instructions should specify a time at following the inventory. The inventory supervisor should which not be a member of an inventory team but should material receipts, shipments, and other removals be such as available at all times during the inventory to handle waste discards are cut off. No. more material of the problems that might arise and to assure that specified type should be received into or shipped the or inventory is proceeding satisfactorily. removed from the plant after that time. 'he records for receipts, shipments, and other removals also should be

(2) Material Balance Area Inventory cut off after the last receipt and the last shipment or Supervisor. One individual in each material balance discard prior to the specified cutoff time and the books should be assigned the responsibility for the inventoryarea closed for the material balance interval: The material in cutoffs should be controlling, with the records brought that area. This person should be familiar with the up to date to the final receipts and remfovals. However, operations and material in the MBA and probably will if be data are not available for a receipt received close the material custodian for the MBA. to or after the cutoff time, such a receipt should not be included in the inventory and the records.

The responsibilities and authority of the MBA inventory supervisor should be stated in writing.

He should be responsible for all aspects of the inventory When it is necessary to make a shipment or within his assigned MBA as directed by the written take a receipt after the cutoff time and before the inventory instructions for the MBA. His authority inventory is finished, such receipts and shipments should should extend to any matters relevant to preparation be made with the approval of and under the control for of and conduct of the inventory within his MBA within the Plant Inventory Supervisor. He should maintain the a log of such items so that they are, properly reflected framework of the written inventory instructions. in the He records and in the physical inventory data. Any should not have the authority to deviate from the receipt after the cutoff should be identified and segregated written instructions without approval of the Plant so that it will not be included in the physical inventory.

Inventory Supervisor. Addition of such receipts to the records should be made for the material balance interval following the inventory.

(3) Inventory Teams. Teams for conducting If it is necessary to make a shipment after cutoff but the inventory, i.e., the actual listing, tagging, measuring, before the inventory is completed, such shipments etc., should consist of at least two persons. More people may be required on teams where material handling should be inventoried before shipment at the measured or shipment value for the material and such quantities nondestructive measurements are to be carried out included in the physical inventory. The records for during the inventory. Alternatively, nondestructive the measurement teams or material-handling teams may shipment should be shown in the following material be balance interval. Material discards should be coordinated established to assist other inventory teams as required and specified in the inventory instructions. Each with inventory schedules so that all discards have been inventory team should contain one person who made and properly recorded before the inventory cutoff is time.

familiar with the areas assigned for inventory and one person from another area or organizational unit to serve as a controller to assure accuracy and compliance with (2) Internal Transfers. Inventory instructions instructions. Inventory team instructions should be should specify the cutoff times and procedures for in each writing and should include all of the specific activities MBA. All MBAs do not need to be inventoried at the for each team for each assigned area. The inventory same time, but may be taken in sequence with or teams should have no authority to deviate from specific counter to the process or merely in sequence of instructions without approval of the MBA Inventory assignment to the inventory team. Material movements Supervisor or the Plant Invenlory Supervisor. between MBAs should be controlled prior to, during, and after the inventory to assure that all material has

5.13-10

been inventoried and that none is inventoried more thar. instructions should include a detailed description of the once. procedures to be followed in taking the inventory to assure that all items and materials are inventoried once Internal transfer cutoff times should be and not more than once. Such description should established and stated in the inventory instructions SO include instructions for listing the inventory and tagging that material is not transferred between material balance inventoried items and for control of inventory lists and areas during the inventory. MBA records cutoff should tags. Preprinted serially numbered inventory tags and be coordinated with the material transfer cutoff so that lists should be used and should be controlled' by the the records will accurately reflect the inventory of the Plant Inventory Supervisor.

MBA. Internal transfer cutoff times do not have to be the same for all MBAs. They may progress with the Inventory teams should be assigned specific inventory. blocks of numbered sheets and tags, and all such items should be accounted for by the team to the Plant When the inventory in an MBA is Inventory Supervisor. The inventory sheets should have complete, the transfer cutoff should remain in effect a column for the tag number along with other columns until the entire inventory is complete. To avoid process for the inventory data sufficient to identify each item, shutdown or to permit earlier startup, enough material record the associated quantity of SNM element and should be moved into the MBA inventory prior to cutoff isotope, and any other data pertinent for the inventory to keep the process going until the inventory is complete such as sample numbers or NDA test results or log book and transfer cutoff is lifted. references. When an item is inventoried it should be tagged and listed. The tag number should appear in the If it is necessary to make internal transfers column for tag numbers on the line for the properly before completion of the inventory, these should be identified item. Every tag number assigned to a team made on an exception basis with the approval of and should either appear on one of the lists assigned to that under the control of the Plant Inventory Supervisor. He team or be returned to the Plant Inventory Supervisor.

should maintain a log of all such transfers to permit the All Inventory sheets should be returned whether used or proper adjustments to the inventory. not. When a sheet is full, it should be initialed by both team members and any auditors or other observer, as

(3) Process. Process cutoff does not necessarily appropriate. Completed sheets should be collected by mean shutdown of the process. The process may the Plant Inventory Supervisor at frequent intervals continue to operate during inventory. Cutoff controls during listing. Sheets that are voided for some reason should be established to assure accuracy of in-process should not be destroyed but should be marked void, inventory. The various techniques for dynamic inventory initialed by the team, and returned to the Inventory require carefully controlled cutoff procedures to provide Supervisor. Any changes made on the sheets before they an accurate in-process inventory. Transfers to or from are rca:arned to the. Inventory Supervisor should be the process should be handled in a manner similar to initialed by the team members and any auditors or MBA internal transfers. Material and records cutoff fo: observer as appropriate. Multiple copy listing can be the transfers to and from material in process as defined used to provide the Plant Inventory Supervisor with an in 10 CFR Part 70 should be carefully controlled to, original control copy of the lists to check against tag permit establishing the in-process. material balance as numbers and list numbers and subsequently to maintain required by IOCFR Part 70. Inventory instructions control of any changes made to the sheets during should specify the manner in which the in-process reconciliation.

inventory is to be taken and the process cutoff controls to be used. Such controls could include: The inventory instructions should make (a) No raw material added to the process provision for anomalies and discrepancies such as the after a specified time; discovery that a tamper-proof seal has been opened. The (b) No recycle permitted after a specified inventory teams should have no discretion to deviate time; from the written instructions; therefore, the instructions (c) Transfers to and from intermediate should provide that the MBA or Plant Inventory storage cut off at a specified time; Supervisor be called to resolve any problems.

(d) Scrap and waste generated after a specified time or between specified times segregated (2) MBA Inventory Schedules. Inventory from all other scrap and waste; and instructions should include a schedule for MBA

(e) Product produced after a specified inventories which specify starting times for the time or between specified times segregated from all inventory team assignments and cutoff procedures other product. necessary for each MBA to be inventoried. All MBAs in a plant need not be inventoried at the same time nor c. Inventory Instructions during the same material balance interval. Inventory instructions should identify which MBAs are to be (I) General Instructions. Inventory inventoried and the specific timing of such inventories.

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(3) MBA Instructions. Inventory instructions inventory purposes. Inventory instructions should should be prepared for each MBA to specify in detail identify the measurement data that are to be used. These how the inventory is to be conducted in each MBA. should be the data resulting from measurements (a) The type of inventory should be performed closest to the time of the sealing or specified, i.e., shutdown, dynamic, counter-current, etc. tamper-safing that are sufficient to establish the SNM

(b) The extent of shutdown and cleanout should be specified with appropriate cutoff for quantities and associated limits of error consistent with required LEMUF limits for the material balance.

KJ

processing'and material transfers. When only a portion (h) When tamper-safing has not been used of the MBA or process is to be shut down, instructions or has been compromised, when SNM has not yet been should be given as to the equipment to remain operative, sealed, e.g., trays of fuel pellets, or when sealed items are that to be shut down, and how the interface between the not uniquely identified, e.g., unnumbered fuel rods or static and dynamic portion of the area is to be pins, the validity of previous measurements should be controlled. verified or the SNM content of the items remeasured.

(c) For equipment that is shut down, Inventory instructions should specify the extent of such instructions for cleanout, flushout, dismantling, etc.,

should be given. These instructions should include the verification or rermeasurement. Remeasurement should treatment, handling, and measurement of material be performed at a level of confidence equivalent to the removed from such equipment. original or normal measurement for the type of material in question. This may involve lot blending and sampling (d) For areas of the process not shut down, specific operating instructions should be included or pellet lot sampling equivalent to' the original sampling as to how the process will be operated to permit plans. Where tamper-safing has been compromised, the inventorying the material. Cutoff procedures should be original lot integrity and homogeneity may also have included to provide for the interface between been compromised or altered so that remeasurement inventoried and not-inventoried material associated with should be made at a higher Intensity or level of confidence than the original measurements. Inventory the operating process. Procedures for measuring the instructions should include the sampling plans, SNM content of the operating process should be remeasurement, sampling, and analytical procedures, or specified. Such procedures could include processing to NDA techniques to be used to verify prior an intermediate stage and sampling for analysis or a measurements. Such verification and remeasurement nondestructive analysis technique coupled with volume procedures should include assignment of responsibility or flow measurements. for the sampling and measurement to the appropriate (e) Where item control, either sealed plant personnel. The analytical laboratory should be sources such as fuel pins or containers or possibly vaults made aware of the expected sample load so that proper containing SNM, is used in an MBA, instructions should capability and capacity can be scheduled for prompt be included for identifying and locating all such items in analytical service.

relation to the records for the items. The inventory team could prepare a list of items as they locate, identify, and d. Preliminary Inspection and Review. Prior to the tag them. This list then could be checked against the conduct of a physical Inventory the Plant Inventory identity and location records for the Items as required in Supervisor along with each MBA Inventory Supervisor

10 CFR Part 70. Conversely, the inventory team could should conduct a preliminary inspection of the plant use a copy of the record and check each Item as it is areas to be inventoried and review inventory instructions located, identified, and tagged. The team should assure and procedures with the responsible personnel. Such that all items physically present are tagged and checked against the list and that all items on the list are located, Inspections and reviews should be made sufficiently in advance to allow time for corrective action, if needed.

identified, and tagged.

(f) Where item control includes tamper-safing of containers or vaults, inventory (1) Process Condition

s. The Plant and MBA

Inventory Supervisors should review process conditions instructions should include procedures for verifying the and status with operatinig supervision of each MBA or integrity of the tamper-safing devices. The instructions process to be inventoried. Inventory instructions should should describe the tamper-safing devices and how the be reviewed in relation to production schedules to assure inventory team can tell whether the device has been that they are compatible and that any areas to be shut compromised. Instructions should include procedures down are properly scheduled for shutdown.

for the team to follow if they find a tamper-safing device that has been compromised. The first thing to do in such (2) MRA Preparations. Preparation in each a case should be to notify the MBA and Plant Inventory MBA for inventory should be reviewed with MBA

Supervisors. custodians and MBA inventory supervisors to assure that (g) When tamper-safing has been used and each understands his instructions, duties, and for uniquely identified sealed sources (i.e., the SNM Is responsibilities during the inventory. The areas should be sealed in a tube, jacket, capsule, or other such inspected to assure that material is measured and mechanism which makes the SNM inaccessible), previous tamper-safed, packaged, labeled, stored, or otherwise measurements of the SNM content may be used for prepared for the inventory. Arrangements should be

5.13-12

made for the measurement and tamper-safmg of any items. If these tests of the inventory accuracy do not unmeasured material In the MBA that will be present show a high level of confidence, in the order of 95% or better, additional checks should be made or the area during the inventory.

reinventoried. In addition to the list and tag accuracy

(3) Records. Plant and MBA records should be checks for an area, the tags and lists assigned to the area reviewed to assure that they are current and that record team also should be accounted for. Upon completion of clerks and accountants understand the records cutoff the entire in e.ntory all tags and inventory lists should be procedures and times applicable to each set of records. accounted fur by the Plant Inventory Supervisor.

(4) Measurements. Sampling and measurement b. Cutoff Verification. Upon completion of each procedures to be used during the inventory should be MBA inventory and of the entire plant inventory, the reviewed with the responsible persons to assure that they plant and MBA cutoff procedures should be verified to understand their instructions, duties, and assure that all internal transfers were recorded in the responsibilities. Any equipment to be used in such proper MBA records and none were recorded in more procedures should be inspected and calibrated or than one area; that material was inventoried in the calibration records checked to assure that .the proper area; and that all receipts and shipments were instrumentation is ready for accurate inventory recorded properly with respect to the cutoff times for measurements. The analytical sample schedule should be the respective material movements. All transfers into or reviewed with the laboratory supervision to assure out of each MBA should be checked for a short period prompt analytical results (perhaps a day) prior to and after the cutoff time to

(5) Inventory Teams. Inventory instructions assure that the transfers were recorded in the records of should be reviewed with each inventory team in detail the MBA in which the material was inventoried.

Documentation of receipts and shipments should be for each area it is to inventory to assure that each team checked in a similar manner to assure that only those member understands his duties and responsibilities. A

tour of the areas in which each team will work should be receipts included in the material balance interval ended used to orient the inventory teams. by the inventory just taken are included in the plant records for that interval and that all shipments made

3. Conduct of Inventory before the cutoff time have been removed from the records. Documentation of measured discards also The inventory should proceed according to should be checked in a similar manner.

instructions and plans. If proper planning, inspection,

, and personnel orientation have been carried out, there c. Inventory Summary and Reconciliation. The will be a minimum of problems. Nevertheless, the Plant raw data from the inventory lists should be summarized Inventory Supervisor should not be assigned to any as soon as possible after listings are completed. Some specific activities, such as being team member, so that he MBA summaries may be prepared before the total plant can be available at any time to take care of anomalies inventory is completed. It also may be that completed and to approve deviations from planned procedures. summaries will have to wait on analytical data to provide During the inventory it may be useful for the Plant element and/or isotopic extension for some line items on Inventory Supervisor to move from area to area to the inventory sheets. Analytical scheduling should be maintain cognizance of the progress of the inventory. planned to make this delay as short as possible. The When touring the areas, he should keep in touch so that original inventory lisis and their summaries should be he is available for problems and to maintain control of maintained undei the control of the Plant Inventory tags and inventory lists. Supervisor. Copies of inventory lists and summaries should not be provided to an MBA until the Plant

4. Post-inventory Activities Inventory Supervisor's summary for the MBA has been a. List and Tag Accuracy Check. Upon prepared and reconciled to the MBA records. Such completion of the inventory in each area, before the area reconciliation should be done under the control of the is released from cutoff, the Plant Inventory Supervisor Plant Inventory Supervisor. The MBA inventories should should inspect the area with the MBA Inventory be summarized under the control of the Plant Inventory Supervisor for the area to assure that all material In the Supervisor to provide the total plant inventory.

area has been tagged with current inventory tags. A

random sample of the items in each area should be Inventory summaries must include a summary checked against the inventory lists, and a random sample of the material in process as defined in 10 CFR Part 70

of the items on the lists should be checked against the for each material type for the total plant inventory to items in the area to assure that items have been tagged permit calculation of the MUF and LEMUF for each and have been recorded accurately on the inventory such material type in accordance with requirements of sheets. It is neither practical nor necessary that these 10 CFR Part 70. Material in-process balances may be verification checks be 100%. A valid statistical sampling calculated for each MBA as an aid to management io plan should be used for the two populations, i.e., the localizing the major MUF and LEMUF contributions.

Y ) population of tagged items ind the population of listed The total plant inventory for each material type must be

5.13-13

prepared to provide data to comply with the records and Using the physical inventory data, other plant reports requirements of 10 CFR Part 70. record data, analytical data, and quality assurance data, the limits of error of the MUF (LEMUF) must be Inventory reconciliation involves comparlng *t cidculated as required by 10CFR Part 70 for the results of the physical inventory to the inveqoqs AN

stated in the records and resolving any differences to the in.process material balances. The statistical techniques extent possible by correction of errors in either set of and methodology for this calculation are beyond the data. A record should be made of all adjustments made scope of this guide and are the subjects of other during reconciliation to either the physical inventory regulatory guides.

data or to the records. Such adjustments to the Inventory data should be approved by the Plant d. Final Report. The final report of the inventory Inventory Supervisor. Adjustments to the records should should document the Inventory summaries, be approved according to established plant control respective material balances and the MUFs and LEMUFs procedures for such adjustments. The find adw~tm4n to permit facility management and the AEC, if should be the material unaccounted for (MUM wi) avpropdate, to evaluate the result

s. If MUF and LEMUF

will bring the records for the respective MDAs and the for any balances are in excess of the applicable limits total plant into agreement with the physical inventory. specified pursuant to 10 CFR Part 70 or plant-imposed This MUF adjustment should be documented and limits, additional reporting according to 10 CFR Part 70

approved for each MBA and for the total plant according requirements and possibly plant management to the established plant procedures for recording MUF. requirements would be necessary.

REFAEJNCES

1. "Evaluation of Minor Isotope Safeguard Techniques 2. "Process Inventory Determination by Isotopic (MIST) in Reactor Fuel Processing," USAEC Report Techniques," R. A. Ewing, Battelle Columbus WASH-1 154, Office of Safeguards and Materials Laboratories, 505 King Avenue, Columbus, Ohio Management, February 20, 1970. 43201, prepared for presentation to the IAEA Panel on the use of Isotopic Composition Data in Safeguards, Vienna, Austria, April 10-14,1972.

5.13.14