Nuclear Critically Safety

DOE-STD-1128-98

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NUCLEAR CRITICALITY SAFETY

This chapter will emphasize present-day criticality concerns from the standpoint of what

health physics personnel need to know to ensure that the DOE mission is accomplished in a

safe and cost effective manner. It provides an overview of the administrative and technical

elements of current nuclear criticality safety programs. It does not provide a definitive

discourse on nuclear criticality safety principles or repeat existing guidance. For health

physics personnel who require a greater understanding of nuclear criticality safety, the

references contained here provide a source of such detailed requirements and information.

Nuclear criticality safety issues at DOE facilities historically have been concerned with

manufacturing plutonium, processing plutonium into weapon components, and storing

weapon components and weapons in safe arrays. With DOE's newly identified mission of

concluding much of the plutonium production and decommissioning of production reactors

and processing facilities, today's nuclear criticality safety concerns have changed. While the

historic nuclear criticality safety issues remain with the storage of weapons and associated

components, current concerns include the disassembly of weapons, processing, and

disposition of unique plutonium materials (commonly referred to as "legacy materials"),

and decommissioning of production reactors and processing facilities.

Radiation protection personnel should understand nuclear criticality principles and the

impact of these principles on radiological conditions that result from the processing,

handling, and storage of fissionable materials. Radiation protection personnel provide an

additional knowledgeable resource to help recognize workplace situations that might lead

to the violation of a nuclear criticality control parameter that could contribute to an

inadvertent nuclear criticality event. There have been occasions in the history of the nuclear

industry when radiation protection personnel have observed and stopped unsafe actions by

facility personnel that, if allowed to continue, might have resulted in an inadvertent nuclear

criticality. Radiation protection personnel must also be aware of the potential impact of

actions that may be routine for normal radiation protection practice, but which could result

in the violation of a nuclear criticality control parameter. Finally, radiation protection

personnel provide significant support in emergency response actions should an inadvertent

nuclear criticality occur. These actions include use of emergency instrumentation, accident

dosimetry, radiological dose assessment, and recovery.

This chapter reviews (1) nuclear criticality safety regulations and standards applicable to

DOE facilities, (2) criticality control factors, (3) past criticality accidents and associated

lessons learned, (4) roles, responsibilities, and authorities of health physics staff with regard

to nuclear criticality safety, (5) the content of an acceptable nuclear criticality safety

program, and (6) a summary of the criticality safety issues identified in DOE/DP-0123T,

Assessment of Plutonium Storage Safety Issues at Department of Energy Facilities (DOE,

1994a).

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