System Classification

DOE-STD-3024-98

12, the essential constituents of statements of safety

2.2 System Classification

function are:

The SDD shall state the overall classification that

The situations, and any specific accidents,

has been assigned to the system. This classification

during which the system may be called upon

should have been based on the highest ranking (most

to perform its safety function(s).

important) requirements identified for the system,

using the hierarchy presented in Section 3 of this

The specific objective of the system in its role

standard. For example, if a system were to have

of preventing, detecting, or mitigating

Safety-Significant, Mission-Critical, and General

undesirable occurrences.

requirements, but no Safety-Class requirements, it

would be classified as a "Safety-Significant"

Those performance characteristics that have

system. If a system were to have Mission-Critical

been specifically relied upon in the

and General requirements, but no Safety or

authorization basis, including the hazard

Environmental Requirements, it would be classified

analysis and accident analysis, (this may

as a "Mission-Critical" system. This part of the

include initial conditions or assumptions

section should be limited to a simple one-sentence

concerning the system or its operation).

statement such as, "This system is classified as

`Mission-Critical.'"

Statements of safety functions in the SDD shall be

consistent with the corresponding information in the

This section shall include a simple positive or

facility authorization basis and specific references to

negative statement indicating whether or not the

the authorization basis documents shall be provided.

system being described is the subject of the facility

OSRs/TSRs.

Note: A fundamental understanding of

the functions to be provided by Safety

2.3 Basic Operational Overview

SSCs is integral to maintaining the

analyzed and approved engineering

This section shall include a simplified system

basis, as well as to operations, testing,

diagram, including boundaries and interfaces.

surveillance, maintenance, and

Where subsystems exist, they shall be illustrated on

modification activities. It is important

the simplified system diagram.

that safety function statements contain

sufficient information and clarity to

This section shall include a brief discussion of how

provide the fundamental understanding

the system operates. This discussion should be

that supports the development of

limited to those operational aspects necessary to

functional requirements, identification

understand the requirements in Section 3.

of appropriate criteria, safety

assessments, evaluation of system

performance capabilities, and

Chapter 3

evaluation of changes.

Requirements and Bases

If all the system functions have been defined, then

the overall function or purpose of the system has

This section of the SDD identifies both the

been defined indirectly also. To avoid potential

requirements on the system and the bases for those

misunderstandings due to this definition being only

requirements. This section shall also present the

implicit, the SDD shall explicitly state the overall

classification of those requirements with regard to

function or purpose of the system.

importance, and shall refer to the source documents

from which the requirements and bases were

obtained.

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