1、REAFFIRMED September 12, 2007 ANSI/ANS-8.7-1998 (R2007) REAFFIRMED February 23, 2012 ANSI/ANS-8.7-1998 (R2012) This standard has been reviewed and reaffirmed with the recognition that it may reference other standards and documents that may have been superseded or withdrawn. The requirements of this
2、document will be met by using the version of the standards and documents referenced herein. It is the responsibility of the user to review each of the references and to determine whether the use of the original references or more recent versions is appropriate for the facility. Variations from the s
3、tandards and documents referenced in this standard should be evaluated and documented. This standard does not necessarily reflect recent industry initiatives for risk informed decision-making or a graded approach to quality assurance. Users should consider the use of these industry initiatives in th
4、e application of this standard. Secretariat American Nuclear Society Prepared by the American Nuclear Society Standards Committee Working Group ANS-8.7 Published by the American Nuclear Society 555 North Kensington Avenue La Grange Park, Dlinois 60526 USA Approved December 2, 1998 by the American Na
5、tional Standards Institute, Inc. ANSI/ANs-8.7-1998 American National Standard for Nuclear Criticality Safety in the Storage of Fissile Materials American National Standard Designation of this document as an American National Standard attests that the principles of openness and due process have been
6、followed in the approval procedure and that a consensus of those directly and materially affected by the standard has been achieved. This standard was developed under procedures of the Standards Committee of the American Nuclear Society; these procedures are accredited by the Amer ican National Stan
7、dards Institute, Inc., as meeting the criteria for American National Standards. The consensus committee that approved the standard was balanced to ensure that competent, concerned, and varied interests have had an opportunity to participate. An American National Standard is intended to aid industry,
8、 consumers, governmental agencies, and general interest groups. Its use is entirely volun tary. The existence of an American National Standard, in and of itself, does not preclude anyone from manufacturing, marketing, purchasing, or using products, processes, or procedures not conforming to the stan
9、dard. By publication of this standard, the American Nuclear Society does not insure anyone utilizing the standard against liability allegedly arising from or after its use. The content of this standard reflects acceptable practice at the time of its approval and publication. Changes, if any, occurri
10、ng through develop ments in the state of the art, may be considered at the time that the standard is subjected to periodic review. It may be reaffirmed, revised, or withdrawn at any time in accordance with established procedures. Users of this standard are cautioned to determine the validity of copi
11、es in their possession and to establish that they are of the latest issue. The American Nuclear Society accepts no responsibility for interpretations of this standard made by any individual or by any ad hoc group of individuals. Requests for interpretation should be sent to the Standards Department
12、at Society Headquarters. Action will be taken to provide appropriate response in accordance with established procedures that ensure consensus on the inter pretation. Comments on this standard are encouraged and should be sent to Society Headquarters. Published by American Nuclear Society 555 North K
13、ensington Avenue La Grange Park, IDinois 60526 USA Copyright 1999 by American Nuclear Society. All rights reserved. Any part of this standard may be quoted. Credit lines should read “Extracted from American National Standard ANSI/ANS-8.7-1998 with permission of the publisher, the American Nuclear So
14、ciety.“ Reproduction prohibited under copyright convention unless written permission is granted by the American Nuclear Society. Printed in the United States of America Foreword (This Foreword is not part of American National Standard for Nuclear Criticality Safety in the Storage of Fissile Material
15、s, ANSI/ANS-8.7-1998.) As with many standards and guides, the direct solution to a specific problem may not be immediately evident in these pages. The application of some of the mass limits and allowances permitted in storage arrangements requires groups, or individuals, experienced in criticality t
16、o examine the contingencies attendant to handling massive pieces, to deviations from established procedures, or to those perturbations or mishaps commonly encountered in storage areas. This standard should be considered not as a substitute for detailed safety analyses, but rather as an integral part
17、 of the analysis for the attainment of a sound criticality safety program. This standard is an extension of American National Standard for Nuclear Criticality Safety in Operations with Fissionable Materials Outside Reactors, ANSI/ANS-8.1-1998. Attention to details of possible single-unit criticality
18、 is, therefore, presumed. The information presented in this standard is primarily directed to criticality safety and is based on validated Monte Carlo calculations. Water is adopted as a standard reflector for storage arrays; because of the variety and thicknesses of concretes that may occur in the
19、more usual conditions of storage, an unambiguous presentation of information is difficult. This standard provides an orientation and direction to nuclear criticality safety practices. Individual safety groups concerned with specific problems are encouraged to publish solutions to these problems, det
20、ailing the bases. Future reviews and revisions of this standard may make use of the information to expand the areas of applicability. Working Group ANS-8.7 of Subcommittee 8 of the American Nuclear Society Standards Committee was established in November 1967 and prepared a number of drafts of this s
21、tandard. One draft underwent a one-year trial use and comment period in 1973. This standard was approved by the American National Standards Institute in 1975 as ANSI N16.5-1975 and was reaffirmed in 1987 as ANSI/ANS-8.7-1975 (R1987). This revision includes several textual enhancements and tabulated
22、changes resulting from confirmatory evaluations by Working Group members Kimball and Vessard, and by individuals in industry: Russell L. Bowden ofBNFL Consultancy Services, David Hanlon of AEA Technology, E. Fitz Trumble of Westinghouse Savannah River Company, and M. Wesley Waddell of the Oak Ridge
23、Y-12 Plant. These researchers determined that uncertainties associated with the calculated values were larger than previously evaluated. Therefore, this revision includes removal ofTable 5.12, Unit Mass Limit in Kilograms ofUranium-233 per Cell in Water-Reflected Storage Arrays, for oxides with HIU
24、3, 10, and 20, and the removal oflimited portions of Tables 5.2, 5.5, and 5.6, Unit Mass Limit in Kilograms of Uranium per Cell in Water-Reflected Storage Arrays, for oxides at 93.2 wt-%, 50 wt-%, and 30 wt-%. Members of Working Group ANS-8. 7 were: C. M. Hopper, Chaimw.n, Oak Ridge National Laborat
25、ory J. J. Bazley, Parallaz Inc. E. C. Crume, Jr., Individual K. D. Kimball, Nisys Corporation B. L. Koponen, Individual J. S. Philbin, Sandia National Laboratories J. T. Thomas, Individual H. Totfer, Safe Sites of Colorado S. G. V essard, Los Alamos National Laboratory D. W. Williams, Westinghouse E
26、lectric Corporation 1-This standard was prepared under the direction of Subcommittee 8, Fissionable Materials Outside Reactors, of the Standards Committee of the American Nuclear Society. Members of ANS-8 at the time of draft preparation and approval were: T. P. McLaughlin, Chairman, Los AlaTTWs Nat
27、ional Laboratory J. A. Schlesser, Secretary, Los AlaTTWs National Laboratory F. M. Alcorn, The Babcock this reduction is sufficient to include the effect of concrete as a reflector. The conditions specified in the tables apply to individual storage areas as follows: Two vaults that are separated by
28、a distance not less than the smallest dimension of the facing surfaces of the arrays stored within the vaults may be considered as individual arrays. Two subarrays separated by not less than the smallest dimension of the facing surfaces of the subarrays may be evaluated as individual reflected array
29、s. 5. 7 Reduction Factors. The mass reduction factors called for in 5.3 through 5.6 are multi plicative. If the application of these limits pro duces an undesirably conservative result, then calculations specific to the system of interest should be performed through the use of a vali-3 American Nati
30、onal Standard ANSI/ANS-8. 7-1998 dated computational technique. Consideration should be given to the precision and any bias in the calculational technique used in determining that the recommended ketr of 0.95 is not exceeded. Increases in cell size to effect reduction factors may be more desirable t
31、han decreases in the mass limits. 5.8 Aisles. Aisles may be provided in the arrays specified in Tables 5.1 through 5.11 by removing units from the array or by increasing the total array volume to provide space. The margin of safety is adequate to permit personnel within the resultant storage area. 5
32、.9 Fissile Material Containment and Shelv ing Materials. The specified limits allow for thicknesses of steel less than 12.7 mm (0.5 in.) as shelving or as close-fitting containers in contact with the fissile material or spaced to less than 26 mm ( -1.0 in.) from the fissile material (see Reference 1
33、). Effects of greater thicknesses of steel or of other materials shall be investigated experimentally or by applying validated compu tational techniques. 5.10 Unit Subcriticality. The contents of each storage cell shall be subcritical if fully reflected with water. 5.11 Unit Spacing. Unit surface se
34、parations shall be at least 152 mm (6 in.) where flooding is credible. 5.12 Unit Shape. The mass limits may be ap plied to units of any shape. 6. Other Applications The tabulated limits are not directly applicable to all systems of interest. When the provisions of Section 5 are satisfied, applicatio
35、n of the tabulat ed mass limits may be extended as described in this section. 6.1 Commingling of Dissimilar Cells. Each cell within any array described in Tables 5.1 through 5.11 is assigned an index equal to the quotient of 100 and the number of cells in the array (see Reference 11). Commingling, i
36、n one array, of any of the cells is permitted if the aggregate of the indices of all the cells within the resultant array does not exceed 100. 6.2 Interpolation. Interpolation may be made among mass limits, number of cells, and hydro-4 gen content. Interpolation of 235U enrichment is permitted. Line
37、ar interpolation is not necessarily appropriate. 6.3 Noncubic Cells. Any tabulated mass limit may be applied to a noncubic cell equal in volume to that tabulated containing a near-equilateral unit if the largest dimension of the cell does not exceed the smallest by more than a factor of 2.5 (see Ref
38、erence 11). The tabulated values may be applied to other than near-equilateral units in noncubic cells if the unit and cell volumes are maintained and if the ratio of the dimensions that characterize the shape of the unit is approximately equal to the ratio of the corresponding dimensions of the cel
39、l. 6.4 Position of Unit in Cell. Units placed in noncubic cells shall be centered to within 10% of the smallest cell dimension. This restriction may be relaxed to permit freedom of horizontal po sition if the mass limit is reduced to 60% of the tabulated value (see Reference 11). If this re duced va
40、lue exceeds 20% of the unreflected spherical critical mass of the material, the minimum edge-to-edge separation between units shall be 152 mm (6 in.). 6.5 Array Shape. The tabulated limits may be applied to arrays of any shape. 6.6 Plutonium-238. The tabulated mass limits for plutonium containing 5.
41、2 wt-% 240Ju (see Table 5.9) may be applied to the storage of units of any non-fissile 238pu content (see Reference 13). The footnote to Tables 5.7 through 5.10 regarding 90% of the water-reflected critical spherical mass is appropriate for 238Pu (see Reference 14). 7. References 1 Thomas, J. T., “C
42、ritical Three-Dimensional Arrays ofU(93.2)-Metal Cylinders,“ Nuclear Science and Engineering 52, 350 (1973) 2 Kolar, 0. C., Finn, H., and Provost, N. L., “Livermore Plutonium Array Program: Experiments and Calculations,“ Nuclear Technology 29, 57 (1976) 3 Thomas, J. T., ed., Nuclear Safety Guide, TI
43、D-7016, Revision 2, NUREG/CR-0095 (1978) 4 Paxton, H. C., and Pruvost, N. L., Critical Dimensions of Systems Containing 235U, 239Pu, and 233U, 1986 Revision, LA-10860-MS (1987) 5 Paxton, H. C., Criticality Control in Op erations with Fissile Material, LA-3366, Rev. 1 (1972) 6 American National Stand
44、ard for Safety in Conducting Subcritical Neutron Multipli cation Measurements In Situ, ANSI/ANS-8.6-1983 (R1995) 7 American National Standard for Nuclear Criticality Safety in Operations with Fis sionable Materials Outside Reactors, ANSI/ ANS-8.1-1998 8 American National Standard Criticality Ac cide
45、nt Alarm System, ANSI/ANS-8.3-1997 9 Thomas, J. T., The Criticality of Cubic Ar rays of Fissile Materials, Y-CDC-10 (1971) 10 Lloyd, R. C., and Clayton, E. D., “The Criti cality of High Burnup Plutonium,“ Nuclear Science and Engineering 52, 73 (1973) 11 Thomas, J. T., Uranium Metal Criticality, Mont
46、e Carlo Calculations and Nuclear Criticality Safety, Y-CDC-7 (1970) 12 Thomas, J. T., “Double-Batching Cell Load ings in Storage Arrays,“ Transactions of the American Nuclear Society 15, 807 (1972) American National Standard ANSI/ANS-8.7-1998 13 Stubbins, W. F., Barton, D. M., and Lona dier, F. D.,
47、“The Neutron-Production Cross Section of 2li8pu in a Fast Spectrum,“ Nu clear Science and Engineering 25, 377 (1966) . 14 American National Standard for Nuclear Criticality Control of Special Actinide Ele ments, ANSI/ANS-8.15-1981 (R1995) When any of the American National Standards referred to in th
48、is document is superseded by a revision approved by the American National Standards Institute, Inc., the revision shall apply. The references above are available from the following sources: American Nuclear Society 555 N. Kensington Avenue LaGrange Park, IL 60526 1, 2, 6, 7, 8, 10, 12, 13, 14 Los Al
49、amos National Laboratory Los Alamos, NM 87545 4, 5 National Technical Information Service Springfield, VA 22161 3 Y-12 Plant Lockheed Martin Energy Systems P.O. Box 2009 Oak Ridge, TN 37831 9, 11 5 American National Standard ANSI/ANS-8.7-1998 Table 5.1 Unit Mass Limit in Kilograms of Uranium per Cell in Water-Reflected Storage Arrays: Metal Number of Units in Minimum Dimension of Cubic Storage Cell (mm) Cubic Storage Arrays 254 305 381 457 508 (H/U 0.01; 100 wt-% 235U; U density 18.7 glcm3) 64 8.8 11.5 15.2 18.5 2
