Regulatory Guide 3.43

Nuclear Criticality Safety in the Storage of Fissile Materials

ML12220A063
Person / Time
Issue date:	04/30/1979
From:	NRC/OSD, Office of Nuclear Regulatory Research
To:
References
RG-3.043, Rev 1
Download: ML12220A063 (6)

U.S. NUCLEAR REGULATORY

COMMISSION

Revision 1 April 1979 REGULATORY

GUIDE OFFICE OF STANDARDS

DEVELOPMENT

REGULATORY

GUIDE 3.43 NUCLEAR CRITICALITY

SAFETY IN THE STORAGE OF FISSILE MATERIALS

A. INTRODUCTION

Section 70.22, "Contents of Applications," of 10 CFR Part. 70, "Domestic Licensing of Special Nuclear Material," requires that applications for a specific license to own, acquire, deliver, receive, possess, use, or transfer special nuclear material contain proposed procedures to avoid accidental conditions of criticality.

This regulatory guide provides guidance for complying with this portion of the Commission's regulations by describing procedures accept-able to the NRC staff for the prevention of criticality accidents in the storage of fissile materials outside nuclear. reactors.

B. DISCUSSION

ANSI N16.5-1975, "Guide for Nuclear Criti-cality Safety in the Storage of Fissile Mate-rial," 1 1 was prepared by Subcommittee

8, Fis-sionable Materials Outside Reactors, of the Standards Committee of the American Nuclear Society. ANSI N16.5-1975 was approved by the American National Standards Committee N16, Nuclear Criticality Safety, in 1974 and sub-sequently by the American National Standards Institute (ANSI) on April 12, 1975.ANSI N16.5-1975 is applicable to the storage of fissile materials as metals and oxides. Its applicability is limited to 100 wt-% U-233, ura-nium containing more than 30 wt-% U-235, and plutonium containing more than 80 wt-% Pu-239 (all percentages based on metal content only).The standard presents tabulated mass limits of these fissile materials in storage cells of idealized water-reflected storage arrays.Caution in the use of the tabulated values in the standard is advised to ensure subcriticality

• Lines indicate substantive changes from previous issue.1 Copies may be obtained from the American Nuclear Society,'555 North Kensington Avenue, La Grange Park, Il/lnois 60525.of each storage cell and of the storage array.These tabulated values do not include the effects of moderation by hydrogenous materials contiguous

• to the fissile materials.

Evaluation of these effects by use of a validated computa-tional technique is recommended in the stand-ard. The standard also presents guidance on reduction factors to be applied to the tabulated mass limits to account for the effects of posi-tion and double batching of fissile material in a storage cell, the reflecting )properties of con-crete or other masonry construction materials used in the storage facility, and the proximity of individual storage arrays.C. REGULATORY

POSITION The nuclear criticality safety practices, limits, and conditions for the storage of fissile material and the guidance for other storage configurations contained in ANSI N16.5-1975 provide procedures generally acceptable to the NRC staff for the prevention of criticality accidents in the storage of fissile materials out-side nuclear reactors subject to the following:

1. Use of ANSI N16.5-1975 is not a sub-stitute for detailed nuclear criticality safety analyses for specific storage arrangements for fissile materials.

2. The mass limits tabulated in the standard that are marked by a superscript "a" to show that they exceed 90 percent of the critical mass of a water-reflected sphere should not be used unless it can be demonstrated that their use could not result in criticality under conditions involving errors or accidents such as double batching or water immersion.

3. The tabulated masses in the standard are not acceptable without all of the appropriate adjustments called for by the standard.

License applicants wanting to use the standard should, USNRC REGULATORY

GUIDES Commen should be sent to the Secretary of the Commission, U.S. Nucker Regulatory Guides are to nescribe and make ava.ile to the public = =C07 mission, Washington, D.C. 2060, Attention:

Docketing and methods acceptable to the NRC staff of Implementing Ieci parts of the Commission's regulations, to delineate techniques used by the staff in evalu- The guides are issued in the following ten broad divisiom.stn specific problems or postulated accidems, or to Provide guldanc to applicants, Regulatory Guides are not substitutes for regulations, and com- 1. Power Reactors 6. Products pliance with them Is not required.

Methods and eolutions dlfferent from those 2. Ree1r`h and Test Reactors 7. Trensportetion set out In the guides wil be acceptable if they provide a bead for the findings 3. Fuels asd Materials Facilities S. Occupational Health requisite to the issuance or. continance of a permit or liceNs by the 4. Environmentel and Siting 9. Antitrust and Financial Review Commis*ion.

5. Materials and PIln Protection

10. General Requests for single copies of issued guides (which may be reproduced)

or for Comments and suggestions for lmprovslentw In thme guides are encouraged at placement on an automatic distribution list for single copies of future guides all times, and guides will be revised, as appropriate, to accomrnodste com mnts In specific divisions should be made In writing to the U.S. Nuclear Regulatory end to eflect new Information or elperlnce.

This guide was revised an a reult Commission, Washington, D.C. 20B5, Attention:

Director, Division of of substentive comments received from the pubic end additional staff review. Technical Information and Document Control.

among other things, demonstrate that the re-quirements of paragraphs

5.3 through 5.6 of the standard have been met.4. Section 7 of ANSI N16.5-1975 lists addi-tional documents referred to in the standard.The specific applicability or acceptability of these listed documents will be covered separately in other regulatory guides, where appropriate.

D. IMPLEMENTATION

The purpose of this section is to provide information to applicants regarding the NRC staffIs plans for using this regulatory guide.The methods described in this guide were applied in a number of specific cases during reviews and selected licensing actions. These methods reflect the latest general NRC approach to criticality safety in the storage of certain types of fissile material outside of nuclear reactors.

Therefore, except in those cases in which the applicant proposes an acceptable alternative method for complying with specified portions of the Commission's regulations, the method described herein is being and will continue to be used in the evaluation of submittals for license applications submitted pursuant to 10 CFR Part 70 until this guide is revised as a result of suggestions from the public or additional staff review.I~.0i 5 0 , uz 0.L V z 0 00R w wJ-5 z'4 Uj z 8 UjW U'4 U00 U.->.0 1-_j 4 z W IL