Publication Date: 6/1/74
    Pages: 6
    Date Entered: 1/5/93
    Title: Selection of Material Balance Areas and Item Control Areas
    June 1974
    U.S. ATOMIC ENERGY COMMISSION
    REGULATORY GUIDE
    DIRECTORATE OF REGULATORY STANDARDS
    REGULATORY GUIDE 5.26
    SELECTION OF
    MATERIAL BALANCE AREAS AND ITEM CONTROL AREAS
A. INTRODUCTION
    Proposed (38 FR 26735) Section 70.58, "Fundamental Nuclear Materal
    Controls," of 10 CFR Part 70, "Special Nuclear Material." would require
    certain licensees authorized to possess more than one effective kilogram
    of special nuclear material to establish Material Balance Areas (MBAs)
    or Item Control Areas (ICAs) for the physical and administrative control
    of nuclear materials. This section would require that:
1. Each MBA be an identifiable physical area such that the quantity
    of nuclear material being moved into or out of the MBA can be measured.
2. A sufficient number of MBAs be established so that nuclear
    material losses, thefts, or diversions can be localized and the
    mechanisms identified.
3. The custody of all nuclear material within an MBA be the
    responsibility of a single individual.
4. ICAs be established according to the same criteria as MBAs except
    that control into and out of such areas would be by item identity and
    count for previously determined special nuclear material quantities.
    This guide describes bases acceptable to the Regulatory staff for
    the selection of material balance areas and item control areas.
B. DISCUSSION
    The division of a nuclear plant into material balance areas and
    item control areas can provide improved material control and accounting
    as follows:
1. A loss or theft of material or of an item or items can be
    identified as having occurred in a particular part of the plant so that
    the investigation can be more effective and the loss or theft mechanism
    more easily identified and corrected or counteracted.
2. The assignment of responsibility to a single designated individual
    for the control of the material or the items in each area could provide
    more vigilant and effective control in each area and thus in the total
    plant.
3. The capability for detecting the loss or theft of material may be
    improved by taking smaller material balances.
    Number of MBAs and ICAs
    The number of MBAs and ICAs established at a plant will depend on
    considerations that are specific to the individual plants. Such
    considerations will have a bearing on the definition of the word
    "sufficient" in the Part 70 requirement that the number of MBAs and ICAs
    be sufficient to localize losses or thefts. It is not the number of
    MBAs or ICAs per se that will be sufficient to localize losses but the
    division of the plant into MBAs and ICAs using bases for such division
    which will permit identification and location of losses. Among the most
    significant considerations for establishing MBAs are detection
    capability, physical boundaries, and the organizational structure to
    provide administrative control in each area. Other factors which may
    pertain include material types, processes and process layout, and
    functional locations such as laboratories, shipping and receiving areas,
    or storage areas.
    Each of these factors will affect the selection of MBAs and ICAs
    and the effectiveness of such selection to control material and items
    and to identify losses within an area. For example, if an MBA is
    selected to consist of a building in which there are two processes using
    different material types (such as two different enrichments of uranium),
    there may be some difficulty in identifying to which enrichment a MUF
    should be applied. If each process (probably in separate rooms in the
    building) is established as an MBA, MUFs for each process could be
    identified, and losses or thefts from each process could be evaluated
    and investigated as needed. In this case, the process and the material
    type provided a definition of the MBA. It would not be necessary for
    different types of material to be used in the two processes for them to
    be established as separate MBAs. Two parallel processes using the same
    type of material might be separate MBAs as shown in Cases II and V in
    Appendix A. Division also might be made within a process to establish
    MBAs that would improve detection capability for separate parts of the
    process.
    It may be possible to make the conversion step of a fuel
    fabrication process a separate MBA with a measured balance around it.
    The remainder of the process steps (the fabrication steps, pelletizing,
    sphere formation, alloying, and any other) could constitute another MBA
    up to the point where the nuclear material is sealed in a fuel pin, rod,
    etc. After sealing, the material could be treated as an identifiable
    item and sent to another area for storage or for further fabrication
    such as welding, assembly, or testing. Transfer of the items from the
    MBA would be based on the material quantities as measured when the items
    were loaded.
    If the final fabrication area or storage area receives fuel from
    more than one loading MBA or is in a separate building on the plant
    site, it would be designated as an ICA using item identity and the
    measured quantities from the loading MBAs for control.
    It also may be that the conversion step of the process is not
    administratively separated from the rest of the process so that it could
    not be considered a separate MBA. This would not preclude a measured
    balance around that step if the product from the step were measurable
    before it went into the subsequent step of the process. With proper
    control of the material to assure that all is measured once and only
    once as it moves from process step to process step, measured internal
    material balances can be taken around process segments whose inputs and
    outputs are measurable even though separate MBAs may not be established.
    Detection Capability
    The basic objectives of material balance accounting for special
    nuclear material are to detect the occurrence of missing material
    whether it be lost or stolen, and conversely to provide assurance with a
    stated degree of confidence that if any material is missing it is less
    than a threshold quantity. A prime indicator for attaining these
    objectives is Material Unaccounted For (MUF). The base for evaluation
    of a MUF value is the Limits of Error of the Material Unaccounted For
    (LEMUF). If a MUF value is within the LEMUF value, it can be stated
    with a specified probability that the MUF is due to uncertainties of the
    measurement system. The validity of this statement depends on a number
    of factors, a major one of which is the validity of the LEMUF itself.
    The LEMUF provides the limits which define the threshold quantity for a
    detectable loss or theft. A LEMUF that has been inflated, either
    intentionally or inadvertently, can mask a loss or theft by indicating
    that a MUF is not statistically significant, i.e., the MUF is the result
    only of the measurement error of the system, when in fact the MUF
    includes a significant loss or theft. The ramifications of the
    evaluation of MUF and the generation of data for MUF and LEMUF are the
    subjects of other regulatory guides. It is sufficient for the purpose
    of this guide to know that the combination of a properly generated MUF
    and LEMUF provides a loss detection mechanism.
    In general, the detection capability of MUF and LEMUF varies
    directly with the quality of the material balance measurements and
    inversely with the quantity of material in a given balance. In this
    context, detection capability means the threshold quantity of material
    that the system can detect as being missing with some stated
    probability. This capability is represented by a LEMUF value stated in
    terms of quantity, e.g., grams or kilograms. This detection capability
    based on a measured material balance is associated with MBAs rather than
    ICAs, since ICAs are controlled on an item basis. In an ICA either all
    items are accounted for or they are not. If they are not, one or more
    missing items are indicated, and an investigation is required.
    The selection of MBAs can affect detection capability by lowering
    the quantity of material in a material balance, thereby lowering the
    absolute LEMUF, since with less material there could be a smaller LEMUF
    and a greater sensitivity. This assumes that only the quantity of
    material is changed and not measurement quality.
    Examples showing the effect of this quantity change using this
    assumption are presented in Appendix A of this guide. The examples
    obviously are simplified greatly. In real situations there would be
    complicating factors such as discard streams, scrap removals from MBAs,
    recycle that might cross MBA boundaries, or uneven distribution of
    inventory or throughput between MBAs, in addition to changes in
    measurement quality. Each of these could affect the selection of MBA
    boundaries.
    Physical Boundaries
    The physical boundaries of MBAs and ICAs are not specified in the
    proposed regulations except that they must be "identifiable physical
    areas." The boundaries could be no more than lines painted on the floor
    around certain parts of the process. However, if MBA or ICA boundaries
    do not minimize the possibility of intermixing of materials or items
    from different areas, either intentionally or inadvertently, the balance
    of such an area or the item control for such an area could become
    meaningless, and the location of a loss or theft of material or items
    might not be identifiable. Further, with boundaries that do not provide
    physical separation of materials it is more difficult to discharge the
    custodial responsibility for a given area. It is too easy for material
    to be moved without the proper documentation and appropriate transfer of
    custodial responsibility in such cases. Areas bound by walls, such as
    separate buildings or rooms within a building, or by grids, such as a
    storage crib or a room divider, are well defined and the materials and
    items can be kept within the areas more easily.
    The critical factor is not the physical boundary, but the
    identification of an area which can be administratively controlled as a
    separate area around which either measured material balance control or
    item control can be maintained. This control would be related to the
    three aspects of improved material control and accounting noted in the
    beginning of the Discussion section of this guide, i.e., loss location,
    responsibility assignment, and detection capability. The boundaries
    selected will depend on combinations of considerations of these three
    items.
    Item Control Areas (ICAs) ICAs are differentiated from MBAs to simplify and improve the
    control and accountability of identifiable items. Control into and out
    of ICAs is required to be by item identity and count and previously
    determined special nuclear material quantities. This excludes items
    that do not have an identity that will differentiate them from other
    similar items, e.g., loose fuel pellets or unsealed, unlabeled
    containers of SNM. Such items could be substituted for other similar
    items of different SNM content or the SNM content changed so that
    control of the material would not be maintained. Loaded and sealed fuel
    rods or tamper-safed sealed containers of SNM that have been numbered or
    in some way uniquely identified provide assurance that the quantity of
    contained SNM remains as previously measured. ICAs for the handling and
    storage of such items provide control without the need for making
    additional measurements for material balances. Storage areas for
    finished fuel rods or assemblies, process intermediates, or irradiated
    fuel assemblies could be ICAs. Shipping and receiving areas could be
    considered ICAs if item integrity is maintained in those areas.
C. REGULATORY POSITION
    A variety of factors that are specific for individual plants and
    processes pertain to the establishment of MBAs and ICAs. The
    effectiveness of the MBAs and ICAs in enhancing nuclear material control
    should be evaluated for each situation. The factors presented below
    should be considered in the selection and establishment of MBAs and
    ICAs.
    Physical Boundaries
    Physical boundaries of MBAs and ICAs should be established so that
    control of the material moving into, out of, and within the area can be
    maintained to the extent that material assigned to a given area is kept
    separate from material assigned to any other area. The boundaries of
    the MBAs must be established so that the quantity of material moving
    into or out of an area can be represented by a measured value. The
    boundaries of ICAs must be established so that items moving into or out
    of an area can be controlled by identity, count, and a previously
    measured valid special nuclear material content.
    Detection Capability
    Material flows and inventories and the quality of the measurement
    of such flows and inventories should be given primary consideration in
    establishing material balance areas. Model material balances similar to
    those of Appendix A should be prepared to evaluate the effects of the
    selection of various MBAs. Such model balances should include all of
    the material flow, inventory, and measurement factors that will affect
    the balance. Such factors would include recycle, discards, scrap
    inventory, random and systematic error effects, common measurements and
    their covariant effect, and changes in measurement or inventory quality
    as a result of division of flows or inventories.
    Material balance areas should provide the maximum practicable
    detection capability consistent with other factors such as physical
    boundaries or process operation and layout. To improve detection
    capability, consideration should be given to changes in such things as
    process layout or process operations, physical boundaries, measurement
    techniques, and inventory techniques. Consideration also should be
    given to establishing procedures for material balances around process
    segments internal to MBAs.
    Number of MBAs and ICAs
    The number of MBAs and ICAs established in a specific plant should
    be based on considerations of detection capability and the physical and
    functional aspects of the plant and material that would assist in
    identifying and localizing material losses or thefts.
    Different material should be processed in separate MBAs.
    The establishment of separate processes as separate MBAs should be
    considered. Although detection capability may not thereby be improved,
    the identification and location of losses or thefts would be. Even when
    separate processes are not maintained as separate MBAs, separate
    material balances should be taken around each process to identify and
    locate losses and possibly to enhance detection capability.
    Functional areas such as laboratories, receiving and shipping
    areas, and warehouses or storage vaults should be separate MBAs or ICAs.
    Receiving and shipping areas may be established as ICAs provided the
    material is not processed or subdivided and is identifiable by item and
    in a sealed, tamper-safed condition. Warehouses and storage vaults
    should be considered ICAs since all material in storage should be
    identifiable by item and in a sealed, tamper-safed condition.
    Item Control Areas
    Areas designated as ICAs should contain only items that are
    identified to differentiate them from other similar items and are in a
    sealed tamper-safed condition that assures the integrity of prior
    measurements. Such items as loose fuel pellets or unsealed, unlabeled
    containers of SNM do not have identities that will differentiate them
    from other similar items and are therefore not acceptable for control in
    ICAs.
    APPENDIX A
    EFFECT OF MBA SELECTION ON LEMUF AND DETECTION CAPABILITY
    To show the effect of MBA selection on the LEMUF and the detection
    capability, several examples are presented. The examples are given for
    a simplified plant consisting of two conversion lines and two
    fabrication lines. The plant may be represented by the following
    diagram:
    (Due to database constraints, this equation is not included. Please
    contact LIS to obtain a copy.) where:
    C(1) & C(2) = Conversion lines 1 and 2
    F(1) & F(2) = Fabrication lines 1 and 2
    The MBAs used in the example will be:
    Total Plant - All lines in one MBA
    Parallel MBAs - MBA 1 = C(1) + F(1)
    - MBA 2 = C(2) + F(2) Series MBAs - MBA 1 = C(1) + C(2)
    - MBA 2 = F(1) + F(2) The examples will consider these configurations for both
    inventory-dominated and throughput-dominated processes. The following
    parameters are common to all examples:
1. Throughput is in 2-kg batches (Cases I, II, and III) or 20-kg
    batches (Cases IV, V, and VI) each of which is measured to Plus or Minus
    0.25% (Plus or Minus 5 grams and Plus or Minus 50 grams, respectively).
2. For simplification it is assumed that there are no discards and
    that there is 100% yield in the form of product batches equal in size to
    the input batches and measured to Plus or Minus 0.25%.
3. The inventory interval is two months.
4. Beginning and ending inventories are the same size but do not
    contain any common items or material.
5. The total plant inventory is measured to Plus or Minus 0.2% and
    distributed so that when one-half is measured in a single MBA, it is
    measured to about Plus or Minus 0.28%.
6. For simplification, only random errors have been considered. In a
    real situation both systematic and random errors would need to be
    considered.
7. For simplification it has been assumed that there are no common
    measurements contributing covariance effects. In real situations such
    covariance effects would need to be considered.
    Case I--Inventory-Dominated Process, Total Plant MBA
    Beginning and Ending Inventories each:
    250 kg Plus or Minus 500 g
    Input and Output each:
    30 batches @ 2 kg Plus or Minus 5 g = 60 kg Plus or Minus
    27.4 g
    (Due to database constraints, this equation is not included. Please
    contact LIS to obtain a copy.) The single total plant MBA detection capability is therefore Plus
    or Minus 708 grams.
    Case II--Inventory-Dominated Process, Parallel MBAs.
    For each MBA:
    Beginning and Ending Inventories each:
    125 kg Plus or Minus 354 g
    Input and Output each:
    15 batches @ 2 kg Plus or Minus 5 g = 30 kg Plus or Minus
    19.5 g
    (Due to database constraints, this equation is not included. Please
    contact LIS to obtain a copy.) The detection capability has been improved from 708 grams for the
    single total plant MBA to 501 grams for each MBA. That is, a loss or
    theft of 501 grams in either MBA would have the same probability of
    being detected as a loss of 708 grams in the single total plant MBA.
    The total plant LEMUF for the two parallel MBAs would be Plus or
    Minus 501 Square Root of 2 = Plus or Minus 708 grams, the same as the
    single total plant MBA LEMUF. This is because no additional
    measurements were made, none of the measurements were improved by
    dividing the plant into two MBAs, and there were no common transfers
    between the MBAs.
    Case III--Inventory-Dominated Process, Series MBAs.
    For each MBA:
    Beginning and Ending Inventories each:
    125 kg Plus or Minus 354 g
    Input and Output each:
    30 batches @ 2 kg Plus or Minus 5 g = 60 kg Plus or Minus
    27.4 g
    (Due to database constraints, this equation is not included. Please
    contact LIS to obtain a copy.) The detection capability for Case III is essentially the same as
    for the individual parallel MBAs (Case II). This would be expected
    because the inventory dominates and it is divided in half in each case.
    The total plant LEMUF does not change, even though there have been
    additional measurements made, i.e., for the transfer between MBAs. This
    transfer measurement is assumed to be the same for both MBAs. That is,
    the output measurement of MBA 1 is the input measurement of MBA 2. When
    the uncertainties of the two MBAs are combined to obtain the total plant
    MBA uncertainty, this transfer measurement is common and drops out of
    the equation for the total plant.
    The assumption in this case was that the transfer measurement is
    as good as the input and product measurements. To the extent that this
    is not true, the individual MBA LEMUF is increased and the detection
    capability decreased. This effect becomes more pronounced as the
    absolute uncertainty of the transfer measurement increases. For
    example, if the uncertainty of the transfer measurement were the same as
    that of the inventory, i.e., 60 kg Plus or Minus 354 grams (3% instead
    of the previously used 0.25%) the LEMUF of the individual MBAs would be
    Plus or Minus 614 grams. There would still be some advantage in
    dividing the plant into the series MBAs but not as much as when the
    transfers between MBAs could be measured with a precision approaching
    that of the input and product measurements.
    It can be seen from Cases I, II, and III that striking a balance
    around portions of the inventory will increase the detection capability
    for each portion, but not for the total plant.
    In Case I, if an actual loss of 708 grams had occurred, it would
    be expected that the MUF would exceed the LEMUF of Plus or Minus 708
    grams part of the time. The probability of the MUF exceeding the LEMUF
    in this case could be calculated. When the MUF exceeds the LEMUF, an
    alarm is sounded and the high MUF is investigated as occurring somewhere
    in the total plant.
    In Cases II and III the balance is taken around smaller areas so
    that the detection capability is improved to 502 grams for each area.
    If a loss or theft of 708 grams were to occur in either area, it would
    have a higher probability of detection since the LEMUF is only Plus or
    Minus 501 grams. In addition, if such a loss did occur, the area in
    which it occurred would be shown by the high MUF in that MBA so that the
    investigation could be confined to the smaller area. In order for a
    person to steal 708 grams of material with the same probability of
    success, i.e., being undetected, as in a single total plant MBA,
    portions of the material would have to be removed from two different
    MBAs or over a longer period of time in the same MBA. This would expose
    the thief to an increased probability of detection by the physical
    protection surveillance and alarm systems.
    If a person were to steal 501 grams from each MBA of Case II or
    III the detection capability would be the same for each MBA as for theft
    of the 708 grams from the single total plant MBA. The total quantity
    stolen, however, would be so large that the total theft would have a
    higher probability of detection upon calculation of the balance for the
    entire plant. In the example, the combined LEMUF for the two MBAs would
    be Plus or Minus 708 grams but the MUF (i.e., material stolen) would be
    1002 grams and probably would trigger an investigation. The location of
    the loss within the plant in this case may no be known because the MUF
    of the individual MBAs may not have exceeded the LEMUF.
    Case IV--Throughput-Dominated Process, Total Plant MBA
    Beginning and Ending Inventory each:
    50 kg Plus or Minus 100 g
    Input and Output each:
    30 batches @ 20 kg Plus or Minus 59 g = 600 kg Plus or Minus
    274 g
    (Due to database constraints, this equation is not included. Please
    contact LIS to obtain a copy.)Case V--Throughput-Dominated Process, Parallel MBAs
    For each MBA:
    Beginning and Ending Inventories each:
    25 kg Plus or Minus 71 g
    Input and Output each:
    15 batches @ 20 kg Plus or Minus 50 g = 300 kg Plus or Minus
    194 g
    (Due to database constraints, this equation is not included. Please
    contact LIS to obtain a copy.) The individual MBA detection capability has been improved from 412
    grams to 292 grams. The total plant LEMUF will not change (Plus or
    Minus 292 Square Root of 2 = Plus or Minus 413) because no additional
    measurements were made nor were any improvements made in the measurement
    of any of the balance components.
    Case VI--Throughput-Dominated Process, Series MBAs
    For each MBA:
    Beginning and Ending Inventories each:
    25 kg Plus or Minus 71 g
    Input and Output each:
    30 batches @ 20 kg Plus or Minus 50 g = 600 kg Plus or Minus
    274 g
    (Due to database constraints, this equation is not included. Please
    contact LIS to obtain a copy.) There has been little gain in the detection capability over a
    total plant MBA because the throughput is the same for each of the two
    series MBAs as for a single total plant MBA. The little gain that is
    realized is due to the gain obtained by dividing the inventory in half.
    In addition, if the transfer measurement between MGAs in Case VI is not
    as good as the input and product measurements there may be a loss of
    detection capability. For example, if the precision of the transfer
    measurement for each batch is Plus or Minus 0.5% instead of Plus or
    Minus 0.25%, the uncertainty of this total transfer measurement becomes
    600 kg Plus or Minus 547 grams and the LEMUF for each MBA becomes Plus
    or Minus 780 grams. This is a poorer detection capability than the 412
    grams for the single total plant MBA. The effect of this transfer
    measurement is more pronounced here than in Case @@ where the inventory
    dominated.
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