Risk Binning Guidelines cont'd - doe-std-1120-2-20050082

DOE-STD-1120-2005/Vol. 2

RISK BINNING GUIDELINES

The following Nuclear Safety Risk Ranking Process and associated Control Selection Guidelines should

be used as a qualitative tool to supplement the safe harbor methods in DOE-STD-3009. It is advised that

the numerical guidelines are not to be construed as either risk acceptance nor compliance criteria. Table 1

identifies Consequence Levels and Evaluation Guidelines for the maximally exposed offsite individual

and maximally exposed hypothetical onsite worker. Table 2 identifies the Risk Ranking Bins. Specific

guidelines for application are summarized below.

Unmitigated hazard events shall be evaluated in accordance with the Tables 1 and 2 and guidelines

provided herein.

Risk Class I events must be protected with safety structures, systems, and components (SSCs) and

Technical Safety Requirements (TSRs). For offsite public protection, Safety Class SSCs and TSRs are

required for radiological events that challenge 25 rem TEDE offsite in accordance with Appendix A of

DOE-STD-3009, Change Notice 2. Events resulting in high offsite radiological consequences must be

moved forward into accident analysis for determination of safety classification, without consideration of

Risk Class II events must be considered for protection with TSRs and safety SSCs. The consideration of

control(s) shall be based on the effectiveness and feasibility of the considered controls along with the

identified features and layers of defense in depth (DID). Events resulting in high offsite radiological

consequence must be moved forward into accident analysis for determination of safety classification,

without consideration of frequency.

Risk Class III events are generally protected by the safety management programs (SMPs). These events

may be considered for defense in depth SSCs in unique cases.

Risk Class IV events do not require additional measures.

For facility worker protection, significant hazardous events are evaluated for appropriate controls in

accordance with DOE-STD-3009, Change Notice 2. The activity-specific controls (e.g., PPE and hot

work permit) should be developed as part of a work control process, not as a specific part of the Safety

Basis per 10 CFR 830. The actual implementation of work control process should be reviewed as part of

the annual ISMS verification. For those events identified in the hazard analysis that require a control that

is not contained in an SMP, a discrete administrative control should be established.

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