Basic Categorization Guidelines

DOE-STD-1021-93

2.4

Basic Categorization Guidelines

(d)

The basic categorization guidelines are summarized in the flow chart shown in Figure 2-1 and

described in the following paragraphs category by category. The guidelines presented here

assume that the hazard categorization/classification, accident analyses, and identification of

safety-class and safety-significant systems for facilities that store, handle, or process

radioactive and toxic materials have been performed and documented in accordance with

applicable DOE Orders and standards as listed in Subsection 2.2 and the requirements of

Subsection 2.3 above. It is also assumed that the mission and functional/performance

requirements of SSCs in facilities not covered by the above-referenced DOE Orders/standards

are known, or have been determined.

The application of the basic categorization guidelines presented here will establish the

preliminary performance category of SSCs. The preliminary performance category may not

account for system interactions, if any, that are described in Subsection 2.5 below, but shall

account for common-cause failure effects as discussed in Paragraph 2.3(c) above. It is to be

noted that the hazard categorization is based on a method for assessing risk from potential

hazards and follows the graded approach discussed in the NPH Implementation Guide for

DOE Order 420.1 (DOE G 420.1-2).

Performance Category 4: An SSC shall be placed in preliminary Performance Category 4

(b)

(PC-4) if it is a "safety-class" item as defined in STD-3009-94 (CHG-1) and Section 2.3,

above, and if its failure during an NPH event could result in off-site release consequences

greater than or equal to the unmitigated release from a large (>200 MWt) Category A reactor

severe accident. There are not expected to be many such facilities in the DOE complex. Not

all safety-class SSCs are necessarily PC-4. If the adverse off-site consequences from an NPH

event are significant enough to make them safety-class but are substantially less than those

associated with consequences from an unmitigated large Category A reactor severe accident,

the SSCs should be placed in PC-3. An SSC that does not satisfy the above criteria may also

be placed in PC-4 for improved performance if justified from cost-benefit considerations.

Performance Category 3: An SSC shall be placed in preliminary Performance Category 3

(c)

(PC-3) if it is not covered in Paragraph 2.4(b) above, and if: its failure results in adverse

release consequences greater than safety class SSC Evaluation Guidelines limits but much less

than those associated with PC-4 SSCs.

For additional applications refer to DOE-G-420.1-2.

An SSC that does not satisfy the above criteria may also be placed in PC-3 for improved

performance if justified from cost-benefit considerations. For new facilities, since it may not

cost too much more to design the facility as PC-4 instead of PC-3, it may be desirable to

design such PC-3 facilities in the conceptual design stage to PC-4 criteria, subject to funding

constraints.

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