reference 166 - ncsp.llnl.gov

REFERENCE 166

“NUCLEAR CRITICALITY SAFETY CRITERIA FOR STEEL-PIPE INTERSECTIONS CONTAINING AQUEOUS SOLUTIONS OF FISSILE MATERIALS,” ANSUANS-8.9- 1987 (AMERICAN NATIONAL STANDARDS INSTITUTE, INC., NEW YORK, 1987).

nuclear criticality safety criteria for steel-pipe intersections containing

aqueous solutions of fissile material

ANSVANS-8.94 987 Revision of

ANSIIANS-8.94 978

American National Standard Nuclear Criticality Safety Criteria for Steel-Pipe Intersections

Containing Aqueous Solutions of Fissile Materials

Secretariat American Nuclear Society

Prepared by the American Nuclear Society Standards Committee Working Group ANS4.9

Published by the American Nuclear Society 555 North Kensington Avenue La Grange Park, Illinois 60525 USA

Approved April 3, 1987 by the American National Standards Institute, Inc.

American Designation of this document as an American National Standard attests that the

National 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

Standard been achieved.

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 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 American National Standard, in and of itself, does not preclude anyone from manufacturing, marketing, purchasing, or using products, processes, or procedures qot conforming to the standard.

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, occurring through developments 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 It may be reaffirmed, revised, or withdrawn at any time in accordance with established procedures.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 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 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 at Society Head- quarters. Action will be taken to provide appropriate response in accordance with established procedures that ensure consensus on the interpretation.

Comments on Headquarters.

this standard are encouraged and should be sent to Society

Published by

American Nuclear Society 555 North Kensington Avenue, La Grange Park, Illinois 60525 USA

Copyright 0 1987 by American Nuclear Society.

Any part of this standard may be quoted. Credit lines should read “Extracted from American National Standard ANWANS-8.9-1987 with permission of the publisher, the American Nuclear Society .” 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 a part of American National Standard Nuclear Criticality Safety Criteria for Steel-Pipe Intersections Containing Aqueous Solutions of Fissile Materials, ANSUANS-8.9-1987.)

Basic parameters and practices for nuclear criticality control outside reactors are described in American National Standard for Nuclear Criticality Safety in Operations with Fissionable Materials Outside Reactors, ANSI/AN%8.14983, and in documents referenced therein. However, for the most part, the data in that standard are single parameter limits.

In the past there has been a paucity of experimental and calculated data for geometric arrangements, such as crosses, ells, and tees, for storage and processing of aqueous solutions of fissile materials in pipes. This situation resulted in overly conservative applications which became evident soon after Work Group 8.9 undertook the drafting of a standard on this subject in 1968. Over the succeeding years, additional experimental data and advanced computational technology became available and now provide the means to reduce the conservatism in industrial practice and permit greater flex- ibility in process applications. The American National Standard Nuclear Criticality Safety for Pipe Intersections Containing Aqueous Solutions of Enriched Uranyl Nitrate, ANSUANS-8.9-1978, has been extended to include typical aqueous solutions of fissile materials and, in particular, uranium containing no more than 5 wt% 235U. Accept- able configurations are presented as standard schedule pipe sizes for a variety of parameters.

In order to facilitate the applicability of this standard allowances have been made for situations which cannot be known or controlled absolutely. The specifications given in this standard are based upon validated calculations in which consideration of an adequate margin of subcriticality included variations in chemical concentrations (kern ry 0.03), a bias in calculations of solution systems (ken ry 0.021, the influence of container materials (keff hr 0.05), and a minimum margin of subcriticality (keff - 0.05). Thus, the systems as specified have a nominal keff of 0.85. Submerged intersections have a nominal keff of 0.90. Generally, fissile and other materials will be present in addi- tion to aqueous fissile solutions contained in piping. It will be necessary for a safety specialist to evaluate their reactivity contribution to proposed pipe intersections in order to confirm compliance with requirements of the standard. It would be unusual for a design not to require review by a safety specialist.

This standard was prepared by Work Group ANS-8.9, under the guidance of American Nuclear Society Standards Subcommittee 8. The Work Group, chaired by 3. T. Thomas, was comprised of the members of the Subcommittee 8 and J. E. Bigelow, Oak Ridge National Laboratory.

The membership of Subcommittee 8, Fissionable Materials Outside Reactors, at the time of preparation and approval of this revision was:

J. T. Thomas, Chairman, Martin Marietta Energy Systems, Inc. E. B. Johnson, Secretary, Oak Ridge National Laboratory F. M. Alcorn, Babcock and Wilcox Company H. K. Clark, Savannah River Laboratory E. D. Clayton, Battelle Pacific Northwest Laboratories D. M. Dawson, Battelle Memorial Institute M. C. Evans, British Nuclear Fuels plc N. Ketzlach, U. S. Nuclear Regulatory Commission R. Kiyose, University of Tokyo W. G. Morrison, Exxon Nuclear Zdaho Co., Inc. (Retired) D. R. Smith, Los Alamos National Laboratory G. E. Whitesides, Martin Marietta Energy Systems, Inc. F. E. Woltz, Goodyear Atomic Corporation

Consensus Committee N16, Nuclear Criticality Safety, which reviewed and approved this standard in 1985, had the following membership:

Dixon Callihan, Chairman E. B. Johnson, Secretary

AlexF.Perge ........................................ American Institute of Chemical Enginers Dixon Callihan .................................................... American Nuclear Society Ricardo Artigas ........................ American Society for Testing and Materials (Liaison only) D. Frank Cronin ................................................... .Atomic Industrial Forum Leo E. Hansen ................................................. Exxon Nuclear Company, Inc. Representative not Assigned. ........................................... Health Physics Society C. Leslie Brown .................................... Institute of Nuclear Materials Management William T. Mee, alt. William R. Waltz ................................................. Savannah River Laboratory Blake P. Brown. .................................................. U.S. Department of Energy George H. Bidinger ....................................... U.S. Nuclear Regulatory Commission Elizabeth B. Johnson, Individual Hugh C. Paxton, Individual Fred W. Sanders, Individual

Contents SeCtion Page

1. Introduction ...................................................... ..l

2. Scope ............................................................ ..l

3. Definitions ....................................................... ..l 3.1 Limitations .................................................... .l 3.2 Shall, Should, and May ........................................... 1 3.3 Glossary of Terms ............................................... 1

4. Nuclear Criticality Safety Practices ................................... .2

5. Specifications for Pipe Intersections ................................... .2 . 5.1 Reflector

5.2 Aqueous 5.3 Aqueous 5.4 Aqueous

Conditions..............................................2 Uranium Solutions. ..................................... .2 Plutonium Solutions .................................... .3 233USolutions .......................................... .

6. Application of Criteria .............................................. .3

7. References.. ....................................................... .

Tables ................................................................

Table1 ......................................................... ...5 Table 2 ......................................................... ...6 Table 3 ......................................................... ...7 Table4 ......................................................... ...7

Figures .............................................................. .

Fig. 1 Area of Intersection .......................................... .4 Fig. 2 Intermediate Reflector Condition ............................... .4 Fig. 3 Partial Reflection. ........................................... .4 Fig. 4 Prohibited Quadrant for Intermediate

Reflector Condition .......................................... .4

Nuclear Criticality Safety Criteria for Steel-Pipe Intersections Containing Aqueous Solutions of Fissile Materials

1. Introduction

This standard provides criteria and data based on criticality experiments and validated calculations’-’ which are generally applicable to homogeneous aqueous solutions of fissile materials. It includes specific information on fissile solutions containing uranium highly enriched in the 235U or 233U isotope, lutonium, and uranium solutions having a 23& content not exceeding 5 wt% of the total uranium.

2. Scope This standard is applicable to the storage, trans- fer, and processing of homogeneous aqueous solutions of uranium and plutonium in intersecting schedule 10, or heavier, steel pipes. No information is included on specific chemical and mechan- ical technology, on fluid dynamics, or on other engineering fundamentals also required in safe design of process equipment.

3. Definitions

3.1 Limitations. The definitions given be1 .ow are restricted to the purposes of this standard. Other

1J. T. Thomas, “Reflectors, Infinite Cylinders, Intersecting Cylinders, and Nuclear Criticality,” Nucl. Sci. Eng., 67,279 (1978). 2N. F. Cross, G. E. Whitesides, and R. J. Hinton, “Monte Carlo Analysis of Experimentally Critical Pipe Intersections,” Trans. Am. Nucl. Sot., 17, 268 (1973).

Qeanne Dickinson, “Calculations for Pipe Intersections Con- taining Fissile Solution, ” RFP-1499, Dow Chemical U.S.A., Rocky Flats Division (1970). 4B. B. Ernst and C. L. Schuske, “Empirical Method for Calculating Pipe Intersections Containing Fissile Solutions,” RFP-1197, Dow Chemical U.S.A., Rocky Flats Division (1968).

55. K. Fox, L. W. Gilley, and D. Callihan, “Critical Mass Studies, Part IX, Aqueous 235U Solutions,” ORNL-2367, Oak Ridge National Laboratory (1958). SE. B. Johnson, “The Nuclear Criticality of Intersecting Cylinders of Uranyl Fluoride Solutions,” Y-DR-129, Oak Ridge Y-12 Plant (1974).

specialized terms are defined in the Glossary of Terms in Nuclear Science and Technology [1].7

3.2 Shall, Should, and May. The word “shall” is used to denote a requirement, the word “should” to denote a recommendation, and the word “may” to denote permission, neither a requirement nor a recommendation. To conform with this standard, all operations shall be per- formed in accordance with its requirements but not necessarily with its recommendations.

3.3 Glossary of Terms

area of intersection. The area of the solution within an arm which intersects a plane tangent to the column at the point where the axis of the arm intersects the surface of the column. (See Fig. 1.)

arm. Any pipe intersecting a column.

column. The pipe of largest diameter in a system of intersecting pipes.

environmental factors. Conditions of the envi- ronment, usually not directly related to the process, that may affect the margin of subcriticality of a system and that could be subject to change.

full reflector. A closely fitting, effectively infinite thickness of water, or its equivalent, sur- rounding the system of pipes.

intermediate reflector. A neutron reflector that contributes reactivity to a column with intersecting arms not exceeding that reactivity corresponding to the presence of a concrete wall in con- tact with the column and arms in a 2-m-square room having 30-cm-thick concrete walls and floor. (See Fig. 2.)

7Numbers in brackets tion 7, References.

refer to corresponding numbers in Sec-

American National Standard ANSVANS-8.9-1987

partial reflector. A neutron reflector that contributes reactivity to a column with intersecting arms not exceeding that reactivity corresponding to the presence of a 2-m-square room having 30-cm-thick concrete walls and floor, in which the fissile material is more than 30 cm from any concrete surface. (See Fig. 3.)

nuclear criticality safety. Protection against the consequences of an inadvertent nuclear chain reaction, preferably by prevention of the reaction.

quadrant. The region on the surface of a section bounded by any two perpendicular planes intersecting along the axis of the section.

section. Any arbitrary 0.5-m length of a column.

validated computational technique. A calcula- tional method that satisfies the requirements in American National Standard for Nuclear Criti- cality Safety in Operations with Fissionable Ma- terials Outside Reactors, ANWANS-8.1-1983 [2].

4. Nuclear Criticality Safety Practices

Operations within the scope of this standard shall be conducted in accordance with American Na- tional Standard for Nuclear Criticality Safety in Operations with Fissionable Materials Outside Reactors, ANSI/ANS-&l-1983. Section 4 of ANS-8.1 discusses administration and technical practices to be followed, and the Appendix lists some credi- ble abnormal operating conditions that should be considered. This standard supplements ANS-8.1 by providing acceptable configurations for pipe intersections containing homogeneous aqueous solutions of fissile materials. All dimensions shall be interpreted as nominal values of schedule 10 or heavier standard steel pipe. Only single columns with intersections are considered in this standard. Multiple columns or columns in the vicinity of other fissile materials and the influence of their environmental factors shall be investigated by experiment or by a validated computational technique. It is emphasized that appropriate precau- tions to help assure quality in installation and operation of equipment and for control of moder- ators and of nearby fissile materials shall be established to prevent the invalidation of any of the stipulated parameters upon which nuclear criticality safety is dependent.

5. Specifications for Pipe Intersections

Acceptable pipe intersections utilizing standard schedule 10, or heavier, steel pipe are presented in Tables 1 through 4 for several fissile materials and neutron reflector conditions.8 Since no limit is imposed on the length of a column or on the number of sections containing arms, a column containing an unlimited number of sections would be subcritical.

5.1 Reflector Conditions. Specifications for pipe intersections shall be made on the basis of the reflector condition. Selection of the reflector condition for a column shall be based upon an evaluation of its location and on environmental factors.

5.1.1 Sections shall meet the appropriate specifications of dimensions, quadrants per section permitted to contain arms, and number of arms per quadrant presented in Tables 1 through 4 for the selected reflector condition.

5.1.2 A column located a distance of 30 cm or less from a wall shall satisfy the intermediate reflector specifications.

5.1.3 Arms shall not intersect a column, under the intermediate reflector condition, in the quadrant bisected by a plane containing the column axis and the shortest distance from the column surface to the wall (see Fig. 4).

5.1.4 Full-reflector specifications shall be applied to a column that is either submerged or that has hydrogenous materials between the arms.

5.1.5 A column located a distance of more than 30 cm from a wall should satisfy the partial reflector condition.

5.2 Aqueous Uranium Solutions. The specifications of Tables 1 through 3 apply to uranium of any 2WJ content in aqueous solutions, provided that the 233U content does not exceed 1 wt% of the uranium content. The specifications of Table 4 may be used in lieu of Tables 1 through 3 for uranium solutions in which the 2WJ content of the uranium does not exceed 5 wt%, and the 233U content of the uranium does not exceed 0.05 wt% of the total uranium.

spipe intersections meeting the reflector conditions of Tables 1 through 4 were evaluated by the method described in the reference of Footnote 2 and had neutron multiplication factors not exceeding 0.85 for the partial and intermediate reflector conditions and not exceeding 0.90 for the full reflector.

2

American National Standard ANSI/ANS-8.9-1987

5.3 Aqueous Plutonium Solutions. The specifications of Tables 1 through 3 shall apply to aqueous solutions of plutonium not exceeding a con- centration of 400 g Pu/L. The a% content of the plutonium shall not exceed the 240Pu content.

5.4 Aqueous mu Solutions. The specifications df Tables 1 through 3 shall apply to aqueous solutions of uranium or thorium havin tion of 233 U not exceeding 500 g B

a concentra- 33U/L.

6. Application of Criteria

Appropriate to the fissile material and evaluated reflector condition of a column, the following requirements shall be verified for pipe intersections to which the specifications of Tables 1 through 4 are applied.

6.1 The reactivity contribution to a column from environmental factors in process operations shall be confirmed not to exceed the contribution of the selected reflector condition.g Pipe dimensions should be selected to satisfactorily compensate for possible changes in reflector conditions.

6.2 The maximum area of intersection per quadrant, i.e., the sum of the areas intersected by all arms, specified in Tables 1 through 4 shall not be exceeded. The tabulations represent orthogonal intersections. The angle between column and arm

axes may range between 30 and 90 degrees. It may be necessary to reduce the number of arms per quadrant or, in the case of a single arm, to reduce the arm diameter in order to satisfy the specified maximum permissible area of intersection.

6.3 Regardless of the total area of intersection in a quadrant, the specified number of arms per quadrant in the Tables shall not be increased.

6.4 The minimum separation of multiple arms within a quadrant shall be no less than the separation of the maximum permissible number when equally spaced. This separation shall not be reduced for continued extension of arms.

7. References

[l] American National Standard Glossary of Terms in Nuclear Science and Technology, Nl.l-1976 (ANS-9). American Nuclear Socie- ty, LaGrange Park, IL.

[23 American National Standard for Nuclear Cri- ticality Safety in Operations with Fissionable Materials Outside Reactors, ANWANS-8. l- 1983. American Nuclear Society, LaGrange Park, IL.

Only the standards explicitly referred to in this document qualify as references. Subsequent revi- sions of these standards shall not be substituted.

The system should have a k,u < 0.85 for the partial and intermediate reflector condition, and d 0.90 for the full reflector condition.

3

Reflector wall uadr axia

ant

I , I #C’ N I ' I

=‘,8'

s?' ' e

$6 I * Area of intersection I ’ I ' - . * Plane tangent to I

I column surface I I I 9 Column I I I

Column axh

Fig. 1. Area of intcr8ection

Concrete v

230 cm

CT

w--w

*0.3 In

r -c-s I I I I I I I I I .

+2m+ I I

Pig. 3. Partial reflection

- -s

I

2m

I --

Fig. 2. Intermediate reflector condition

Concrete

Column

1 0.3 m

a m e

I

2m

I --

+2m+ I I

r Reflector wall

Shortest distance

Bisecting plane

Area of intersection

Tangential plane

Fig. 4. Prohibited quadrant for intermediate reflector condition

Table 1. Specifications for Steel Pipe Intersections Containing Aqueous Solutions of Uranium or Plutonium in Standard Schedule 10 Pipe Under Partial Reflector Conditions

Maximum permissible 235~8 or 239pUb 233uc

Maximum permissible

area of intersection

per arm (cm21

235~1 or 230pub 233~~

Permissible number of Standard pipe schedule 10 or

heavier. Nominal size (in.)

wlumn arm

Standard pipe schedule 10 or

heavier. area of 1 Permissible number of 1 Permissible number of Permissible number of

quadrants arms per per section quadrant with arms

intersection quadrants per section witb arms

arms per quadrant

quadrants per section with arms


arms per quadrant Nominal size (in.)

l-i arm

6 4 3

2.5

2

1.5 5 5

4

3.5

3

2.5

2

4 4

3.5

3

per arm (cm21

91.94 1 1 4 2.5 35.16 1 4

5 3

1 4 2 3 3 2

53.87

35.16

1 2

2 1

2 23.55 1 4 4 3 I 3 1 2 3

2 1 1

1.5 5 3 2 1

1 2 3

3 2 1

3.5 3.5 1 2 3

3 2 1

23.55

3 53.87 1 1 4 3 2

2 4 3 2 4 1 1 3 4 4 2 3 4 4 2

14.32 4 1 3x-++ 142.06 1 1 4 3

2.5 91.94 1 3

2 1

1 1 I I

2 1

3 2 1 2

4 3 2 1

3 2 3 2

23.55 I

1 4

5 4

2 71.61 1 2 4

3 2 1

1 2

1.5 5

+

++-

53.87 2 3 4

3 2 1

1 2 3

3 3 3

2.5

2

1.5 2.5 2.5

3 2

3 4 3

35.16 3 4

35.16 3 4

23.55 4

1 14.32 4 , 35.16 4 , 23.55 4

23.55 4 2 1 3

4

1 2

5 4 ~~ I 5 91.94 1 2 3

3

~ : 4 4 I 4

2 5 4 I 5 2 3

3 2 I- 3 2

1 2

71.61 1.5 14.32 4 5 4 5

53.87 3 4

2 3

1 I

*Aqueous uranium solutions: applicable to any 23sU content of the uranium, provided the 233U content does not exceed 1 wt% of the total uranium. bAqueous plutonium solutions: applicable to plutonium concentrations not exceeding 400 g/L and containing more 2’?% than 241Pu.

‘Aqueous solutions of uranium or thorium: applicable to any 233U content not exceeding 500 g 233U/L.

Table 2. Specifications for Steel Pipe Intersections Containing Aqueous Solutions of ranium or Plutonium in Standard Scheduled 10 Pipe Under’ Intermediate Reflector Conditions U

I

Permissible number of

Maximum permissible

area of Standard pipe schedule 10 or

235~1 Or 239pUb

Permissible number of intersection

per arm (cm21

quadrants arms per per section with arms

I I

quadrants quadrantd per section

with arms Nominal size (in.)

column II column 1 arm 1 (cm2) 1 with arms 1 I

with arms I

arm

4 L I 1

3.5 3.5 71.61 1 3 1 ! 2 2 2 2 1 3 1 ,

3 53.87 1 4 1 3 2 3 2 2 3 II I I I I 2 I 3 I 1

5 3.5 71.61

3 53.87

2.5 2 3

-3 3

3

4 3

-4 3

3

35.16 : I : I

2 23.55 1 3 1 2 1 4 4 91.94

: I : I 3.5 il.61

3 3

2.5

2

53.87 2 3 3 2

I I 35.16 3 4

23.55 3 4

+

3 53.87 I 1 I 4 3 3

I 1 2

2.5 35.16 1 5 1 3 4 3

23.55 3 4 2 3

14.32 3 4 2 3

2

1.5 2.5 2.5 35.16 3 3 2 4

2 23.55 3 3 3 4

‘Aqueous uranium solutions: applicable to any 23sU content of the uranium, provided the 233U content does not exceed 1 wt% of the total uranium.

bAqucous plutonium solutions: applicable to plutonium concentrations not exceeding 400 g/L and containing more 2?u than 241Pu.

CAqucous solutions of uranium or thorium: applicable to any 233U content not exceeding 500 g 233U/L.

dNote 5 1.3 and Fig. 4 for prohibited quadrants. .

American National Standard ANSUANS-8.9-1987

Table 3. Specifications for Steel Pipe Intersections Containing Aqueous Solutions of Uranium or Plutonium in Standard Schedule 10 Pipe Under Full Reflector Conditions

Maximum permissible


per arm (cm21

235~s or 239pUb 233~~

Permissible number of Permissible number of Standard pipe schedule 10 or

heavier. Nominal size (in.)


-- 1 1 2 3 4

--

2 3 4

4 --

arms per quadrant

--- I I I 1 I

1 1 1

1

column I arm

91.94 71.61 53.83 35.16 23.55

I 71.61 53.87 35.16

----

53.87

4 1 4 I 4 I

3 I

3 4

‘Aqueous uranium solutions : applicable to any 235U content of the uranium, provided the 233U content does not exceed 1 wt% of the total uranium.

bAqueous plutonium solutions : applicable to plutonium concentrations not exceeding 400 g/L and containing more ‘%A than “‘Pu.

‘Aqueous solutions of uranium or thorium: applicable to any 233U content not exceeding 500 g ‘33U/L.

Table 4. Specifications for Steel Pipe Intersections Containing Aqueous Solutions of Uraniuma with Maximum 235U Content of 5 wt%

Full reflector Number of

Parti reflector Number of

Intermedia le reflector Number of

Standard pipe schedule 10 or heavier.

Nominal size (in.) -- column arms

Maximum permissible


per arm (cm2)

IO 10 550.32

8 351.61

6 204.52

5 142.06

8 8 351.61

6 204.52

quadrants- per section with arms


arms per quadrant

arms per quadrant

‘The 233U content of the uranium shall not exceed 0.05 wt%.

bNote 5 1 3 and Fig. 4 for prohibited quadrants. . .

0

1

I

1

1

1 --

2 1

3 I

3 I

3 I

3 1 L

reference 166 - ncsp.llnl.gov

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