Criticality Safety Criteria for the Handling, Storage, and Transportation of LWR Fuel Outside Reactors: ANS-8.17-1984

G. E. Whitesides Retired

Oak Ridge National Laboratory* P.O. Box 2008

Oak Ridge, Tennessee 3783 1-6370

To be presented at 1996 ANSENS International Meeting

November 10-14, 1996 Washington, DC

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This report was prepared as an account of work sponsored by an agency of the United States Government. Neither the United States Government nor any agency thereof, nor any of their employees, makes any warranty, express or implied, or assumes any legal liability or responsibility for the accuracy, completeness, or use- fulness of any information, apparatus, product, or process disclosed, or represents that its use would not infringe privately owned rights. Reference herein to any spe- cific commercial product, proccss, or service by trade name, trademark, manufac- turer, or otherwise does not necessarily constitute or imply its endorsement, m m - mendation, or favoring by the United States Government or any agency thereof. The views and opinions of authors expressed herein do not necessarily state or reflect those of the United States Government or any agency thereof.

The potential for criticality accidents during the handling, storage, and transportation of

fuel for nuclear reactors represents a health and safety risk to personnel involved in these

activities, as well as to the general public. Appropriate design of equipment and facilities, handling

procedures, and personnel training can minimize this risk. Even though the focus of the American

National Standard, “Nuclear Criticality Safety in Operations with Fissionable Materials Outside

Reactors,” ANSUANS-8.1-1983 (ref. 1), is general criteria for the ensurance of criticality safety,

ANS-8.17-1984 (ref. 2), provides additional guidance applicable to handling, storage, and

transportation of light-water-reactor (LWR) nuclear fuel units in any phase of the fuel cycle

outside the reactor core.

ANS-8.17 had its origin in the late 1970s when a work group consisting of representatives

from private industry, personnel from government contractor facilities, and scientists and

engineers from the national laboratories was established. The work of this group resulted in the

issuance of ANSUANS-8.17 in January 1984.

The need for ANS-8.17 arose when several Standards relating to the design of he1 cycle

facilities, fuel and waste management, and shipment of fuel began incorporating sections

pertaining to nuclear criticality control. The need to have a Standard prepared by nuclear

criticality specialists that would cover the Criticality safety issues related to all of these areas

became apparent. It was also noted that a checklist of representative parameters and conditions

that must be considered needed to be compiled by specialists familiar with those parameters and

conditions that are important to criticality safety.

The intended application of the Standard focused on the criticality safety consideration of

the design and operation of any of the facilities involved in the entire fuel cycle (outside the

reactor) in which the fissile material is in the form of rods or assemblies of rods. These facilities

range fiom &el element manufacturing plants to transportation of the he1 both before and after

burning to storage both before and after burning, and to shear leach process head-end operations

in a reprocessing facility. Fuel inside the reactor core is excluded fiom consideration in this

Standard.

The standard consists of two major sections. The first section provides a general safety

criteria. This section discusses the relation of the standard to related standards, along with the

requirements specific to this standard. It hrther gives guidance and criteria for basic criticality

control, the use of neutron absorbers and control over them, the need for and use of criticality

alarms, and the allowance for verifiable presence of burnable poisons and/or he1 burnup.

The second major section provides the criteria to establish subcriticality. In performing

criticality safety evaluations, it is necessary to ensure consideration of the most reactive credible

conditions based on the he1 design parameters, storage array dimensions, fuel handling

procedures, and moderation and reflection conditions. In this section, the allowable safe maximum

calculated multiplication factor is defined in terms of the quantities that make up the calculational

and experimental uncertainties and allowances for operation variables due to normal and credible

abnormal conditions or events. Of particular note in this section is a parameter called A k . This is

an arbitrary margin that should be included to ensure the subcriticality after all other uncertainties

are considered. (These concepts for definition of Ak,,,, first outlined in this standard, are now

under consideration for inclusion in the Validation section of the ANS-8.1 standard that is now

undergoing revision.) This section also provides criteria for the direct use of experimental data,

or data derived from experiments, and in situ measurements.

Paragraph 4.4 of the standard requires that consideration be given to normal and credible

abnormal conditions and to related uncertainties, including design tolerances, associated with

are given in the Appendix to the standard.

This standard was reaffirmed in 1989, and is in the final stages of being reaffirmed again,

without change. ANS-8.17 has provided the fuel cycle industry the necessary criticality safety

guidance for the design of safe facilities for the handling, storage, and transportation of LWR fuel

outside reactors.

REFERENCES

1. Nuclear Safety in Operations with Fissionable Materials Outside Reactors, ANSUANS- 8.1-1983, American Nuclear Society (1983).

2, Criticality Safety Criteria for Handling, Storage, and Transportation of LWR Fuel Outside Reactors, ANSUANS-8.17-1984, American Nuclear Society (1984)