1、ANSI/ANS-8.12-1987 FEB I 71993 nuclear criticality control and safety of L.-t:!1i!E.-“lutonium-uranium fuel mixtures outside reactors ( ANSI/ANS-8.12-1987 Revision of ANSI/ANS-8.12-1978 American National Standard for Nuclear Criticality Control and Safety of Plutonium-Uranium Fuel Mixtures Outside R
2、eactors Secretariat American Nuclear Society Prepared by the American Nuclear Society Standards Committee Working Group ANS8.12 Published by the American Nuclear Society 555 North Kensington Avenue La Grange Park, Illinois 60525 USA Approved September 11, 1987 ANSIIANS by the American National Stand
3、ards Institute, Inc. American National Standard Designation of this document as an American National Standard attests that the principles of openness and due process have been followed in the approval procedure and that a consensus of those directly and materially affected by the standard has been a
4、chieved. This standard was developed under the procedures of the Standards Committee of the American Nuclear Society; these procedures are accredited by the American National Standards Institute, Inc., as meeting the criteria for American National Standards. The consensus committee that approved the
5、 standard was balanced to assure that competent, concerned, and varied interests have had an opportunity to participate. An American National Standard is intended to aid industry, consumers, govern mental agencies, and general interest groups. Its use is entirely voluntary. The existence of an Ameri
6、can National Standard, in and of itself, does not preclude anyone from manufacturing, marketing, purchasing, or using products, processes, or procedures not conforming to the standard. By publication of this standard, the American Nuclear Society does not insure anyone utilizing the standard against
7、 liability allegedly arising from or after its use. The content of this standard reflects acceptable practice at the time of its ap proval and publication. Changes, if any, occurring through developments in the state of the art, may be considered at the time that the standard is subjected to periodi
8、c review. It may be reaffirmed, revised, or withdrawn at any time in accord ance with established procedures. Users of this standard are cautioned to deter mine the validity of copies in their possession and to establish that they are of the latest issue. The American Nuclear Society accepts no resp
9、onsibility 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 at Society Head quarters. Action will be taken to provide appropriate response in accordance with established procedu
10、res that ensure consensus on the interpretation. Comments on this standard are encouraged and should be sent to Society Headquarters. Published by American Nnclear Society 555 North Kensington Avenue, La Grange Park, Illinois 60525 USA Copyright 1987 by American Nuclear Society. Any part of this sta
11、ndard may be quoted. Credit lines should read “Extracted from American National Standard ANSIIANS-8.12-1987 with permission of the publisher, the American Nuclear Society.“ Reproduction prohibited under copyright convention unless written per mission is granted by the American Nuclear Society. Print
12、ed in the United States of America Foreword (This Foreword is not a part of American National Standard for Nuclear Criticality Control and Safety of Plutonium-Uranium Fuel Mixtures Outside Reactors, ANSIIANS-S.12-1987,) This standard provides guidance for the prevention of criticality accidents in t
13、he han dling, storing, processing, and transporting of plutonium-uranium fuel mixtures out side reactors and is applicable to all operations involving mixtures of plutonium and natural uranium. It constitutes an extension of the American National Standard for Nuclear Criticality Safety in Operations
14、 with Fissionable Materials Outside Reactors, ANSI/ANS-8.1-1983. Under the prescribed five year review of ANSI/ANS-8.12-1978, the standard has been revised to include subcriticallimits for heterogeneous lattices of mixed oxide fuel pins in water. The basis for the limits for both homogeneous mixture
15、s and for lattices are calculations done by several members of the work group, which have been published in the open literature. These calculations were done by methods that have been validated by correlations with available experimental data, and an adequate margin of subcriticality was allowed. Th
16、e revised standard was prepared by Work Group ANS-8.12.1 of Subcommittee 8 of the Standards Committee of the American Nuclear Society. This work group was composed of: E. D. Clayton, Chairman, Battelle-Pacific Northwest Laboratories R. Artigas, General Electric Company C. 1. Brown, Rockwell Hanford
17、Operations H. K. Clark, Savannah River Laboratory N. Ketzlach, U.S. Nuclear RegUlatory Commission R. Kiyose, University of Tokyo R. A. Libby, Battelle-Pacific Northwest Laboratory D. R. Smith, Los Alamos National Laboratory G. Walker, u.K. Atomic Energy Authority The membership of Subcommittee ANS-8
18、, Fissionable Materials Outside Reactors, at the time of draft preparation and approval was: J. T. Thomas, Chairman, Martin Marietta Energy Systems, Inc. E. B. Johnson, Secretary, Oak Ridge National Laboratory F. M. Alcorn, Babcock m in size have been considered by experimenters to be homogeneous IV
19、. 1. NEELEY and H. E. HANDLER, “Measurement of Multiplication Con stant for Slightly Enriched Homogeneous D03-Water Mix tures and Minimum Enrichment for Criticality,“ HW-70310 Hanford Atomic Products Operations (August 1961) and v. I. NEELEY, J. A. BERBERET and R. H. MASTERSON, “koo of Three Weight
20、Per Cent 235U Enriched D03 and D02 (N03)2 Hydrogeneous Systems,“ HW-66882, Hanford Atomic Products Operations (September 1961). 1 American National Standard ANSIIANS-S.12-1987 3.3 Glossary of Terms. areal density. The total mass of fissionable ma terial per unit area projected perpendicularly onto a
21、 plane. (For an infinite, uniform slab, it is the product of the slab thickness and the concentra tion of fissionable material within the slab.) controlled parameter. A parameter that is kept within specified limits. criticality accident. The release of energy as a result of accidentally producing a
22、 self-sustaining or divergent neutron chain reaction. natural uranium. Reference throughout this standard to natural uranium shall be interpreted to mean uranium in which the concentration of the 235U isotope is equal to or less than 0.71 wt%. nuclear criticality safety. Protection against the conse
23、quences of an inadvertent nuclear chain reaction, preferably by prevention of the reaction. sub critical limit (limit). The limiting value as signed to a controlled parameter that results in a subcritical system under specified conditions. The subcritical limit allows for uncertainties in the calcul
24、ations and experimental data used in its derivation but not for contingencies; e.g., double batching or inaccuracies in analytical determinations. 4. Nuclear Criticality Safety Practices 4.1 Administrative and Technical Practices. Operations within the scope ofthis standard shall be conducted in acc
25、ordance with ANSI/ ANS-8.1-1983 1 except that the limits for plutonium uranium mixtures given herein may be utilized. Attention shall be given to credible abnormal con ditions such as those listed in the Appendix A of ANSIIANS-8.1-1983 1. 4.2 Homogeneity Control. Consideration shall be given to the
26、possibility of preferential sep aration of plutonium from uranium. Neither the limits for homogeneous systems nor those for het erogeneous systems apply unless the plutonium and uranium oxides remain intimately and ho mogeneously mixed. 2 5. Sub critical Limits for Uniform, Homo geneous Plutonium-Ur
27、anium Mixtures in Water Operations with the fuel mixtures specified may be performed safely by complying with anyone of the subcriticallimits given in Tables 1, 2, or 3, provided the conditions under which it applies are maintained. A limit shall be applied only when the effect of neutron reflectors
28、 and other nearby fissionable materials is no greater than that of a contiguous water reflector of effectively infinite thickness. Process specifications shall incorporate margins to protect against uncertainties in process variables and against a limit being accidentally exceeded. 5.1 Homogeneous A
29、queous Mixtures. The limits of Table 1 are applicable to homogeneous mixtures of oxides of natural uranium and plu tonium provided the plutonium oxide content of the mixture of oxides is between 3 wt% and 30 wt%. Limits are provided for three isotopic compositions of plutonium. In applying these lim
30、its, any 238Pu and 242Pu present shall be omit ted in computing the isotopic composition. All limits are valid for uranium containing no more than 0.71 wt% 235U with 239pu. 5.2 Variation of Subcritical Limits with PU02 Content. The limits of Table 1 are appropriate for criticality prevention. For gr
31、eater flexibility, plots of the subcriticallimits of Table 1 are pro vided in Figs. 1 through 5, from which values appropriate to any PU02 content in the range 3 to 30 wt% may be read. These figures give, re spectively, limits on the total mass of the oxides (PU02 + U02), on volume, on cylinder diam
32、eter, on slab thickness, and on areal density. 5.3 Dry and Damp Mixed-Oxide Powders. The limits given in Table 2 apply to dry and damp mixtures of the oxides of plutonium and natural uranium provided the concentration of 240pu ex ceeds that of 241 Pu. Because completely dry oxide may be difficult to
33、 ensure, limits are provided for damp oxides in which 0 241pu II - 240pu 15 wt% and 241pu -I z . W “ ;, “ “ “ , en Pu02 in (PU02 + U02), wt% -Table 2 Subcritical Mass Limits for Single Units of Homogeneously Mixed Oxides of Plutonium and Natural Uranium at Low Moderation The limits apply to combinat
34、ions of plutonium isotopes provided 240pu 241 Pu. 3 8 15 Mass of Mass of Mass of Mass of Mass of Mass of Mass of Plutonium, kg (PU02+ U02), kg Plutonium, kg (PU02+ U02), kg Plutonium. kg (PU02+ U02), kg Plutonium, kg lixed oxides at theoretical msity Sub critical in any amount 122 1729 47.0 355 26.1
35、 lsity of PU02 + U02) .s 11 g/cm3 Pu + VI = 0 Damp mixed oxides at theoretical nsity Isity of 236 8919 49.4 700 32.9 249 23.3 PU02 + U02) :;. 9.4 g/cm3 H:(Pu + U) 0.45 D mixed oxides with 50% voids 885 33,447 161 ,. 2282 102 771 67.9 ,sity of PU02 + U02) S. 4.7 g/cm3 H,(Pu + UI 0.45 30 Mass of (PU02
36、+ U02), 98.6 88.1 256.6 g r . I Co “ ; “ 00 “ “ Table 3 Subcritical Concentration Limits for Plutonium in Homogeneous Mixtures of Plutonium and Natural Uranium of Unlimited Massa These limits apply to combinations of plutonium isotopes provided 240pU 241 Pu. PuO. in (PuO. + UO,) Dry Mixed Oxides, H:
37、(Pu + U) = 0 Damp Mixed Oxides, 0 241 Pu I Curve II 240 241 Pu 2: 15 wt% and Pu:S 6 wt% 240 241 Curve III, Pu 25, wt n , ,P,u:S 15 wt“1 5 10 50 100 Concentration of PU02 in (PU02 + U02) Mixtures, wt% Figure 1. Limiting Mass of Homogeneous Mixtures of the Oxides of Plutonium and Natural Uranium in Wa
38、ter as a Function of the Plutonium Oxide Content. 7 American National Standard ANSIIANS-8.12-1987 8 100 50 OJ 10 E :J o 5 Process specifications shall incorporate margins to protect against uncertainties in process variables and against a limit being accidentally exceeded. I. . I. r-i“ -. I-III . I-
39、r-r-. II . r I f-Isotopic Composition of Plutonium - Curve I 240pu 241 Pu Curve II 240 241 Pu 2: 15 wt% and Pu S 6 wt% 240 241 - Curve III Pu 2: 25 wt% and Pu S 15 wt% 5 10 50 100 Concentration of PU02 in (Pu02+U02) Mixtures, wt% Figure 2. Limiting Volume of Homogeneous Mixtures of the Oxides of Plu
40、tonium and Natural Uranium in Water as a Function of the Plutonium Oxide Content. (See Table 1, Footnote b.) American National Standard ANSIIANS-8.12-1987 38 Isotopic Composition of Plutonium , Curve I 240pU 241 Pu -34 “-240 241 Curve II Pu 2: 15 wt% and Pu :S 6 wt% _ “-Curve III 240pu 2: 25 wt% and
41、 241 Pu :S 15 wt% E () 30 “ 1ii E “ 0 26 “ 0 C “ “- . “ , r- -U . 22 c C “ . III r- -. II 18 Process specifications shall incorporate . . . _ margins to protect against uncertainties in process variables and against a limit being “-accidentally exceeded. 1-14 1 2 3 4 5 6 7 8 910 20 30 40 Concentrati
42、on of Pu02 in (Pu02 + U02) Mixtures, wt% Figure 3. Limiting Diameter of Cylinders Containing Homogeneous Mixtures of the Oxides of Plutonium and Natural Uranium in Water as a Function of the Plutonium Oxide Content. (See Table 1, Footnote b.) 9 American National Standard ANSIIANS-8.121987 E u 241 Pu
43、 . !-240 241 1-Curve II Pu 2: 15 wt% and Pu 241 Pu Curve II 240pU 2- 15 wt% and 241pu S 6 wt% 240 241 Curve III Pu 2- 25 wt% and Pu S 15 wt% OJ E OJ “-10 OJ I I 1 “ 0 “ “-I :l + OJ 0 5 :l a. . “-“ , -0 - “ -in c: OJ 0 co OJ 1 “- III “ II Process specifications shall incorporate margins to protect ag
44、ainst uncertainties in I process variables and against a limit being accidentally exceeded. 0.5 1 I I I I 1 5 10 20 30 4050 100 Concentration of Pu02 in (Pu02 +U02) Mixtures, wt% Figure 5. limiting Areal Density of Homogeneous Mixtures of the Oxides of Plutonium and Natural Uranium in Water as a Fun
45、ction of the Plutonium Oxide Content. 11 American National Standard ANSIIANS-8.12-1987 12 Ol “ N 0 :J + N 0 :J a a “ “ “ :2; 60 50 40 30 25 20 15 10 5 4 3 l . I. -, -, “ “ Process specifications shall incorporate margins to protect against uncertainties in process variables and against a limit being
46、 accidentally exceeded. “ I. “ 1 I. 1 - -I. I. r-. “, . . I. I. f. III I I-Isotopic Composition of Plutonium II-I. 2 I-Curve I 240pu 241 Pu 240 241 I-Curve II Pu 2: 15 wt% and Pu 14 12 10 8 6 4 American National Standard ANSIIANS-8.12-1987 Iotoic Copsiion of Plutoniu I Curve I 240pu 24 Pu -240 241 C
47、urve II Pu 2: 15 wt% and Pu -u . c c 14 Istopic Compoition of Plutoniu I 26 Curve I 240pU 241 Pu -24 1 Curve II 240 241 Pu :2 15 wt% and Pu :S 6 wt% 240 241 Curve III Pu :2 25 wt% and Pu :S 15 wt% 22 20 18 “ “-“ I. I-. . Do not extrapolate, “-r- see caution page 3 “-“ 1“ “ “-I“. II Process specifica
48、tions shall incorporate I- I- margins to protect against uncertainties in process variables and against a Ii mit being accidentally exceeded. I I I I I I 16 2 3 4 5 6 7 8 9 10 20 30 40 Concentration of Pu02 in (Pu02 + U02) Mixtures, wt% Figure 8. Limiting Diameter of Cylinders Containing Heterogeneo
49、us Mixtures of the Oxides of Plutonium and Natural Uranium in Water as a Function of the Plutonium Oxide Content. E - 241 Pu -Curve II 240 241 Pu 2: 15 wt% and Pu : 6 wt% -Curve III 240pu 2: 25 wt% and 241pu : 15 wt% 14 12 r- “ 10 8 “ . I. I “ Do not extrapolate, “ . . see caution page 3 “ . III “-!-. -. . . . . II I- Process specifications shall
