Review of System Safety Classification and Accident Analysis Data

DOE-STD-1021-93

3.4

Review of System Safety Classification and Accident Analysis Data

For the purpose of the NPH performance categorization process, a typical facility is assumed to

consist of:

Several systems, each consisting of many components and each performing a major and

distinct safety-related and/or mission-related function, and/or

One or more buildings that house one or more systems, or part of a system (a building may

also act as a shield or barrier, or as part of a confinement/containment system), and/or

One or more structures (such as a stack or a tank), inside or outside the facility buildings,

that perform a major function, sometimes distinct and sometimes in support of another

system.

For the purpose of performance categorization using the procedures outlined here, a facility will be

considered to consist of systems, and systems will be considered to consist of components. Also,

when a building or a structure performs a major and distinct function, either by itself or together with

other components, it will be referred to here as a "system."

From a review of the pertinent documents, identify and list the systems that constitute the entire

facility under consideration. In general, this list will consist of safety systems (as defined in Sections

2.2 and 2.3) and other systems. Frequently, not all the safety systems are essential for NPH

mitigation. For example, even though certain SSCs are required for maintaining operating

parameters within safety limits during normal operations and anticipated operational occurrences,

these may not be essential for NPH mitigation.2

For systematic performance categorization, the facility systems can be represented in a matrix by

letters of the alphabet, and "safety" functions can be represented by numbers (see Table 3-1). Entries

in this matrix should be alphanumeric. The alphabet part of the entry will represent the system that

is essential for the function represented by the numeric part of the entry. Thus, in the example matrix

of Table 3-1, entry D1 shows that System D is essential for confinement/containment (Function

No.1), and entry D3 shows that System D is also essential for providing radiation protection

(Function No.3). The components in System D that are essential for confinement/containment may

not be the same as the components that are essential for radiation protection, although some

components may contribute to both functions.

Entries in the safety system-function matrix will identify the safety systems (including buildings or

structures that perform a distinct function) that are essential for mitigating NPH-related accidents

only. Thus, if an entire system column is without any entry, that system is not essential for NPH

mitigation (e.g., System G in Table 3-1).

The Safety Analysis Report of the facility shall be used extensively in categorizing the

SSCs.

3-3