Nuclear Facility Safety Analysis

DOE-STD-1136-2004

Guide of Good Practices for Occupational Radiation Protection in Uranium Facilities

Procedures should exist that address the determination and posting of nuclear criticality safety

parameters. These procedures should include a description of how the limits are to be determined and

how workstations are to be posted as to form, geometry controls, mass limits, moderator limits, etc.

Management should provide fire-fighting guidelines to ensure fire-fighting techniques do not violate a

criticality control limit that might lead to an inadvertent nuclear criticality event. These guidelines should

include the posting of specific rooms with acceptable fire-suppression techniques that can be used for a

specific location or the use of notations on facility fire pre-plans (operating procedures) located at fire

stations.

Recovery procedures should be in place to provide for the recovery from a nuclear criticality control

limit violation. A limit violation involves exceeding the fissionable material mass limit or the moderator

liquid limit, or violating any other criticality control in an operations procedure. This process should

separately address both static and dynamic cases, as

responses to these violations may be quite different.

Management should develop and implement nuclear criticality safety training plans and procedures

for all personnel working with or near fissionable materials, as required by ANSI/ANS-8.20 and DOE-

STD-1136-99 Guidance for Nuclear Criticality Safety Engineer Training and Qualification (DOE 1999n).

This program and its associated procedures describe the program, training requirements, recordkeeping,

content, responsibilities, and objectives of a facility nuclear criticality safety program.

Inspections and audits are performed to assess the success of the nuclear criticality safety program.

Qualified individuals who are independent of the operation should perform the inspections and audits.

The audits and inspections should verify that operating procedures and other safety standards are being

followed and identify any weaknesses in the nuclear safety program. Deficiencies should be formally

addressed, tracked, reported, and resolved.

7.2.3.4 Nuclear Facility Safety Analysis

Documented Safety Analyses (DSA) document the analysis and potential consequences of accidents

and abnormal occurrences at nuclear facilities. Per 10 CFR 830.204 (DOE 2001d), with respect to a

nonreactor nuclear facility with fissionable material in a form and amount to pose a potential for criticality,

the DSA defines a criticality safety program that: ensures that operations with fissionable material remain

subcritical under all normal and credible abnormal conditions, identifies applicable nuclear criticality safety

standards, and describes how the program meets applicable nuclear criticality safety standards.

7.3 CRITICALITY ACCIDENT EXPERIENCE

Criticality accidents, sometimes called criticality excursions, can either be single pulse, multiple

pulse, or "steady state" (continuous) excursions.

7.3.1 Types of Criticality Accidents

In a pulse-type criticality accident, there is an initial pulse of 10 16-1018 fissions over a short time-

period (less than 1 second), sometimes followed by additional lower-intensity pulses. In a fissionable

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