Regulatory Guide 5.26
| ML003740041 | |
| Person / Time | |
|---|---|
| Issue date: | 04/30/1975 |
| From: | Office of Nuclear Regulatory Research |
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| References | |
| RG-5.26 Rev 1 | |
| Download: ML003740041 (7) | |
Revision 1 April 1975 U.S. NUCLEAR REGULATORY COMMISSION
REGULATORY GUIDE
OFFICE OF STANDARDS DEVELOPMENT
REGULATORY GUIDE 5.26 SELECTION OF
MATERIAL BALANCE AREAS AND ITEM CONTROL AREAS
A. INTRODUCTION
of the plant so that the investigation can be more effective and the loss or theft mechanism more easily Section 70.58, "Fundamental Nuclear Material Con identified and corrected or counteracted.
trols," of 10 CFR Part 70, "Special Nuclear Material," 2. The assignment of responsibility to a single desig requires certain licensees authorized to possess more nated individual for the control of the material or the than one effective kilogram of special nuclear material to items in each area could provide more vigilant and establish Material Balance Areas (MBAs) or Item Control effective control in each area and thus in the total plant.
Areas (ICAs) for the physical and administrative control 3. The capability for detecting the loss or theft of of nuclear materials. This section requires that: material may be improved by taking smaller material balances.
1. Each MBA be an identifiable physical area such that the quantity of nuclear material being moved into Number of MBAs and ICAs or out of the MBA is represented by a measured value.
2. The number of MBAs be sufficient to localize The number of MBAs and ICAs established at a nuclear material losses or thefts and identify the plant will depend on considerations that are specific to mechanisms.
the individual plants. Such considerations will have a
3. The custody of all nuclear material within an bearing on the definition of the word "sufficient" in the MBA or ICA be the responsibility of a single designated Part 70 requirement that the number of MBAs and ICAs individual.
be sufficient to localize losses or theft
s. It is not the
4. ICAs be established according to the same number of MBAs or ICAs per se that will be sufficient to criteria as MBAs except that control into and out of localize losses but the division of the plant into MBAs such areas would be by item identity and count for and ICAs using bases for such division that will permit previously determined special nuclear material quanti identification and location of losses. Among the most ties, the validity of which must be ensured by tamper significant considerations for establishing MBAs are safing unless the items are sealed sources.
detection capability, physical boundaries, and the This guide describes bases acceptable to the NRC organizational structure to provide administrative con staff for the selection of material balance areas and item trol in each area. Other factors that may pertain include control areas. material types, processes and process layout, and func tional locations such as laboratories, shipping and
B. DISCUSSION
receiving areas, or storage areas.
The division of a nuclear plant into material balance Each of these factors will affect the selection of areas and item control areas can provide improved MBAs and ICAs and the effectiveness of such selection material control and accounting as follows: to control material and items and to identify losses
1. A loss or theft of material or of an item or items within an area. For example, if an MBA is selected to can be identified as having occurred in a particular part 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
- Lines indicate substantive changes from previous issue. in identifying to which enrichment a MUF should be USNRC REGULATORY GUIDES Comments should be sent to the Secretary of the Commission. U.S. Nuclear Regulatory Commission. Washington. D.C. 20555. Attention: Docketing and Regulatory Guides are issued to describe and make available to the public Service Section.
methods acceptable to the NRC staff of implementing specific parts of the Commission's regulations, to delineate techniques used by the staff in evalu, The guides are issued in the following ten broad divisions:
ating specific problems or postulated accidents, or to provide guidance to appli.
cants Regulatory Guides are not substitutes for regulations, and compliance 1. Power Reactors 6. Products with them is not required Methods and solutions different from those set out in 2. Research and Test Reactors 7 Transportation the guides will be acceptable if they provide a basis for the findings requisite to 3 Fuels and Materials Facilities 8 Occupational Health the issuance or continuance of a permit or license by the Commission. 4. Environmental and Siting 9 Antitrust Review Comments and suggestions for improvements in these guides are encouraged 5 Materials and Plant Protection 10 General at all times, and guides will be revised, as appropriate, to accommodate cow mtents and to reflect new information or experience This guide was revised as a Copies of published guides may be obtained by written request indicating the result of substantive commerts received from the public and additional staff divisions desired to the U.S Nuclear Regulatory Commission. Washington. 0 C
review 20555. Attention. Director. Office of Standards Development
applied. If each process (probably in separate rooms in of which is the validity of the LEMUF itself. The the building) is established as an MBA, MUFs for each LEMUF provides the limits that define the threshold process could be identified, and losses or thefts from quantity for a detectable loss or theft. A LEMUF that each process could be evaluated and investigated as has been inflated, either intentionally or inadvertently, needed. In this case, the process and the material type can mask a loss or theft by indicating that a MUF is not provided a definition of the MBA. It would not be statistically significant, i.e., the MUF is the result only of necessary for different types of material to be used in the measurement error of the system, when in fact the the two processes for them to be established as separate MUF includes a significant loss or theft. The ramifica MBAs. Two parallel processes using the same type of tions of the evaluation of MUF and the generation of material might be separate MBAs as shown in Cases II data for MUF and LEMUF are the subjects of other and V in Appendix A. Division also might be made regulatory guides. It is sufficient for the purpose of this within a process to establish MBAs that would improve guide to know that the combination of a properly detection capability for separate parts of the process. generated MUF and LEMUF provides a loss detection mechanism.
It may be possible to make the conversion step of a fuel fabrication process a separate MBA with a measured In general, the detection capability of MUF and balance around it. The remainder of the process steps LEMUF varies directly with the quality of the material (the fabrication steps, pelletizing, sphere formation, balance measurements and inversely with the quantity of alloying, and any other) could constitute another MBA material in a given balance. In this context, detection up to the point where the nuclear material is sealed in a capability means the threshold quantity of material that fuel pin, rod, etc. After sealing, the material could be the system can detect as being missing with some stated treated as an identifiable item and sent to another area probability. This capability is represented by a LEMUF
for storage or for further fabrication such as welding, value stated in terms of quantity, e.g., grams or assembly, or testing. Transfer of the items from the kilograms. This detection capability based on a measured MBA would be based on the material quantities as material balance is associated with MBAs rather than measured when the items were loaded. ICAs, since ICAs are controlled on an item basis. In an ICA, either all items are accounted for or they are not. If If the final fabrication area or storage area receives they are not, one or more missing items are indicated, fuel from more than one loading MBA or is in a separate and an investigation is required.
building on the plant site, it would be designated as an ICA using item identity and the measured quantities The selection of MBAs can affect detection capabil from the loading MBAs for control. ity by lowering the quantity of material in a material balance, thereby lowering the absolute LEMUF, since It also may be that the conversion step of the with less material there could be a smaller LEMUF and a process is not administratively separated from the rest of greater sensitivity. This assumes that only the quantity the process so that it could not be considered a separate of material is changed and not measurement quality.
MBA. This would not preclude a measured balance around that step if the product from the step were Examples showing the effect of this quantity change measurable before it went into the subsequent step of using this assumption are presented in Appendix A of the process. With proper control of the material to this guide. The examples obviously are simplified ensure that all is measured once and only once as it greatly. In real situations there would be complicating moves from process step to process step, measured factors such as discard streams, scrap removals from internal material balances can be taken around process MBAs, recycle that might cross MBA boundaries, or segments whose inputs and outputs are measurable even uneven distribution of inventory or throughput between though separate MBAs may not be established. MBAs, in addition to changes in measurement quality.
Each of these could affect the selection of MBA
Detection Capability boundaries.
The basic objectives of material balance accounting Physical Boundaries for special nuclear material are to detect the occurrence of missing material whether it be lost or stolen, and The physical boundaries of MBAs and ICAs are not conversely to provide assurance with a stated degree of specified in the proposed regulations except that they confidence that, if any material is missing, it is less than must be "identifiable physical areas." The boundaries a threshold quantity. A prime indicator for attaining could be no more than lines painted on the floor around these objectives is Material Unaccounted For (MUF). The certain parts of the process. However, if MBA or ICA
base for evaluation of a MUF value is the Limits of Error boundaries do not minimize the possibility of inter of the Material Unaccounted for (LEMUF). If a MUF mixing of materials or items from different areas, either value is within the LEMUF value, it can be stated with a intentionally or inadvertently, the balance of such an specified probability that the MUF is due to uncertain area or the item control for such an area could become ties of the measurement system. The validity of this meaningless, and the location of a loss or theft' of statement depends on a number of factors, a major one material or items might not be identifiable. Further.
5.26-2
with boundaries that do not provide physical separation out of, and within the area can be maintained to the of materials, it is more difficult to discharge the custodial extent that material assigned to a given area is kept responsibility for a given area. It is too easy for material separate from material assigned to any other area.'.The to be moved without the proper documentation and boundaries of the MBAs must be established so that the appropriate transfer of custodial responsibility in such quantity of material moving into or out of an area can cases. Areas bounded by walls, such as separate buildings be represented by a measured value. The boundaries of or rooms within a building, or by grids, such as a storage ICAs must be established so that items moving into or crib or a room divider, are well defined and the materials out of an area can be controlled by identity, count, and and items can be kept within the areas more easily. a previously measured valid special nuclear material content.
The critical factor is not the physical boundary, but the identification of an area that can be administratively Detection Capability controlled as a separate area around which either Material flows and inventories and the quality of the measured material balance control or item control can be maintained. This control would be related to the measurement of such flows and inventories should be three aspects of improved material control and account given primary consideration in establishing material ing noted in the beginning of the Discussion section of balance areas. Model material balances similar to those this guide, i.e., loss location, responsibility assignment, of Appendix A should be prepared to evaluate the and detection capability. The boundaries selected will effects of the selection of various MBAs. Such model depend on combinations of considerations of these three balances should include all of the material flow, inven items. tory, and measurement factors that will affect the balance. Such factors would include recycle, discards, Item Control Areas (ICAs) scrap inventory, random and systematic error effects, common measurements and their covariant effect, and ICAs are differentiated from MBAs to simplify and changes in measurement or inventory quality as a result improve the control and accountability of identifiable of division of flows or inventories.
items. Control into and out of ICAs is required to be by item identity and count and previously determined Material balance areas should provide the maximum special nuclear material quantities. This excludes items practicable detection capability consistent with other that do not have an identity that will differentiate them factors such as physical boundaries or process operation from other similar items, e.g., loose fuel pellets or and layout. To improve detection capability, considera unsealed, unlabeled containers of SNM. Such items tion should be given to changes in such things as process could be substituted for other similar items of different layout or process operations, physical boundaries, SNM content or the SNM content changed so that measurement techniques, and inventory techniques.
control of the material would not be maintained. Consideration also should be given to establishing Loaded and sealed fuel rods or tamper-safed sealed procedures for material balances around process seg containers of SNM that have been numbered or in some ments internal to MBAs.
way uniquely identified provide assurance that the quantity of contained SNM remains as previously Number of MBAs and ICAs measured. ICAs for the handling and storage of such items provide control without the need for making The number of MBAs and ICAs established in a additional measurements for material balances. Storage specific plant should be based on considerations of areas for finished fuel rods or assemblies, process detection capability and the physical and functional intermediates, or irradiated fuel assemblies could be aspects of the plant and material that would assist in ICAs. Shipping and receiving areas could be considered identifying and localizing material losses or thefts.
ICAs if item integrity is maintained in those areas.
Different material should be processed in separate
C. REGULATORY POSITION
MBAs.
A variety of factors that are specific for individual The establishment of separate processes as separate plants and processes pertain to the establishment of MBAs should be considered. Although detection capabil MBAs and ICAs. The effectiveness of the MBAs and ity may not thereby be improved, the identification and ICAs in enhancing nuclear material control should be location of losses or thefts would be. Even when evaluated for each situation. The factors presented separate processes are not maintained as separate MBAs, below should be considered in the selection and estab separate material balances should be taken around each lishment of MBAs and ICAs. process to identify and locate losses and possibly to enhance detection capability.
Physical Boundaries Functional areas such as laboratories, receiving and Physical boundaries of MBAs and ICAs should be shipping areas, and warehouses or storage vaults should established so that control of the material moving into, be separate MBAs or ICAs. Receiving and shipping areas
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may be established as ICAs provided the material is not differentiate them from other similar items and are processed or subdivided and is identifiable by item and therefore not acceptable for control in ICAs.
in a sealed, tamper-safed condition. Warehouses and storage vaults should be considered ICAs since all
D. IMPLEMENTATION
material in storage should be identifiable by item and in a sealed, tamper-safed condition. This section provides information to applicants and licensees regarding the NRC staff's plans for using this regulatory guide.
Item Control Areas Except in those cases in which the applicant or Areas designated as ICAs should contain only items licensee proposes an alternative method for complying that are identified to differentiate them from other with specified portions of the Commission's regulations, similar items and are in a sealed tamper-safed condition the methods described herein will be used in the that ensures the integrity of prior measurements. Such evaluation . of submittals for license applications or items as loose fuel pellets or unsealed, unlabeled amendments to existing licences docketed after publi containers of SNM do not have identities that will cation of this guide.
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APPENDIX A
EFFECT OF MBA SELECTION ON LEMUF AND DETECTION CAPABILITY
To show the effect of MBA selection on the Case I-Inventory-Dominated Process, Total Plant MBA
LEMUF and the detection capability, several examples are presented. The examples are given for a simplified Beginning and Ending Inventories each:
plant consisting of two conversion lines and two 250 kg +/- 500 g fabrication lines. The plant may be represented by the Input and Output each:
following diagram: 30 batches @2 kg +/- 5 g = 60 kg +/- 27.4 g LEMUF = V 2(27.4) 2 + 2(500)2 = +/-708 g The single total plant MBA detection capability is therefore +/-708 grams.
Case II-Inventory-Dominated Process, Parallel MBAs.
For each MBA:
Beginning and Ending Inventories each:
where:
125 kg +/- 354 g C1 & C2 = Conversion lines 1 and 2 Input and Output each:
F 1 & F 2 = Fabrication lines I and 2 15 batches @2 kg +/- 5 g = 30 kg +/- 19.5 g The MBAs used in the example will be: LEMUF = V/2(19.5)2 + 2(354)2 = +/-501 g Thtal Plant - All lines in one MBA The detection capability has been improved from
708 grams for the single total plant MBA to 501 grams Parallel MBAs- MBA I = C1 + F, for each MBA. That is, a loss or theft of 501 grams in
-MBA2=C 2 +F 2 either MBA would have the same probability of being detected as a loss of 708 grams in the single total plant Series MBAs - MBA 1 = CI + C2 MBA.
-MBA2=Fl +F 2 The total plant LEMUF for the two parallel MBAs The examples will consider these configurations for would be +/-501 Vr2'= +/-708 grams, the same as the single both inventory-dominated and throughput-dominated total plant MBA LEMUF. This is because no additional processes. The following parameters are common to all measurements were made, none of the measurements examples: were improved by dividing the plant into two MBAs, and there were nocommon transfers between the MBAs.
1. Throughput is in 2-kg batches (Cases I, II, and IHI) or 20-kg batches (Cases IV, V, and VI) each of Case Ill-Inventory-Dominated Process, Series MBAs.
which is measured to +/-0.25% (+/-5 grams and +/-50 grams respectively). For each MBA:
2. For simplification, it is assumed that there are no Beginning and Ending Inventories each:
discards and that there is 100% yield in the form of 125 kg +/- 354 g product batches equal in size to the input batches and Input and Output each:
measured to +/-0.25%. 30 batches @ 2 kg +/- 5 g = 60 kg +/- 27.4 g
3. The inventory interval is two months.
4. Beginning and ending inventories are the same LEMUF = /2(27.4)2 + 2(354)2 = 502 g size but do not contain any common items or material.
5. The total plant inventory is measured to +/-0.2% The detection capability for Case III is essentially and distributed so that when one-half is measured in a the same as for the individual parallel MBAs (Case II).
single MBA, it is measured to about +/-0.28%. This would be expected because the inventory domi
6. For simplification, only random errors have been nates and it is divided in half in each case. The total considered. In a real situation, both systematic and plant LEMUF does not change, even though there have random errors would need to be considered. been additional measurements made, i.e., for the transfer
7. For simplification, it has been assumed that between MBAs. This transfer measurement is assumed to there are no common measurements contributing covari be the same for both MBAs. That is, the output ance effects. In real situations, such covariance effects measurement of MBA 1 is the input measurement of would need to be considered. MBA 2. When the uncertainties of the two MBAs are
5.26-5
combined to obtain the total plant MBA uncertainty, grams and probably would trigger an investigation. The this transfer measurement is common and drops out of location of the loss within the plant in this case may not the equation for the total plant. be known because the MUF of the individual MBAs may not have exceeded the LEMUF.
The assumption in this case was that the transfer Case IV-Throughput-Dominated Process, Total Plant measurement is as good as the input and product MBA
measurements. To the extent that this is not true, the individual MBA LEMUF is increased and the detection Beginning and Ending Inventory each:
capability decreased. This effect becomes more pro 50kg_+/- lO0g nounced .as the absolute uncertainty of the transfer Input and Output each:
measurement increases. For example, if the uncertainty 30 batches @ 20 kg +/- 59 g = 600 kg +/- 274 g of the transfer measurement were the same as that of the inventory, i.e., 60 kg +/- 354 grams (3% instead of the LEMUF = /2(274)2 + 2(100)2 = +/-413 g previously used 0.25%), the LEMUF of the individual MBAs would be +/-614 grams. There would still be some Case V-Throughput-Dominated Process, Parallel MBAs advantage in dividing the plant into the series MBAs, but not as much as when the transfers between MBAs could For each MBA:
be measured with a precision approaching that of the Beginning and Ending Inventories each:
input and product measurements. 25 kg-+/-71 g Input and Output each:
It can be seen from Cases I, II, and III that striking a 15 batches @ 20 kg +/- 50 g= 300 kg +/- 194 g balance around portions of the inventory will increase the detection capability for each portion, but not for the +292 g total plant. LEMUF = f2(194)2 + 2(71)2 The individual MBA detection capability has been In Case I, if an actual loss of 708 grams had improved from 413 grams to 292 grams. The total plant occurred, it would be expected that the MUF would LEMUF will not change (+/-292 Vr-= +/-413) because no exceed the LEMUF of +/-708 grams part of the time. The probability of the MUF exceeding the LEMUF in this additional measurements were made, nor were any improvements made in the measurement of any of the case could be calculated. When the MUF exceeds the balance components.
LEMUF, an alarm is sounded and the high MUF is investigated as occurring somewhere in the total plant.
Case VI-Throughput-Dominated Process, Series MBAs In Cases II and III, the balance is taken around For each MBA:
smaller areas so that the detection capability is improved Beginning and Ending Inventories each:
to 502 grams for each area. If a loss or theft of 708
25 kg +/-71 g grams were to occur in either area, it would have a Input and Output each:
higher probability of detection since the LEMUF is only
30 batches @ 20 kg +/- 50 g = 600 kg +/- 274 g
+/-501 grams. In addition, if such a loss did occur, the area in which it occurred would be shown by the high LEMUF = f2(274)2 + 2(71)2 = +/-400 g 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 There has been little gain in the detection capability success, i.e., being undetected, as in a single total plant over a total plant MBA because the throughput is the MBA, portions of the material would have to be same for each of the two series MBAs as for a single total removed from two different MBAs or over a longer plant MBA. The little gain that is realized is due to the period of time in the same MBA. This would expose the gain obtained by dividing the inventory in half. In thief to an increased probability of detection by the addition, if the transfer measurement between MBAs in Case VI is not as good as the input and product physical protection surveillance and alarm systems.
measurements, there may be a loss of detection capabil If a person were to steal 501 grams from each MBA ity. For example, if the precision of the transfer of Case II or III, the detection capability would be the measurement for each batch is +/-0.5% instead of +/-0.25%,
same for each MBA as for theft of the 708 grams from the uncertainty of this total transfer measurement the single total plant MBA. The total quantity stolen, becomes 600 kg +/- 547 grams and the LEMUF for each however, would be so large that the total theft would MBA becomes +/-780 grams. This is a poorer detection have a higher probability of detection upon calculation capability than the 412 grams for the single total-plant of the balance for the entire plant. In the example, the MBA. The effect of this transfer measurement is more combined LEMUF for the two MBAs would be +/-708 pronounced here than in Case III where the inventory dominated.
grams but the MUF (i.e., material stolen) would be 1002
5.26.6
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