Safety-significant structures, systems, and components

DOE-STD -3009-94

control systems). Appendix A provides guidance for implementing the Evaluation

Guideline to classify SSCs as safety-class SSCs.

Safety-significant structures, systems, and components. This category of SSCs is

provided to ensure that important SSCs will be given adequate attention in the DSA and

facility operations programs. Safety-significant SSCs are those of particular importance

to defense in depth or worker safety as determined in hazard analysis. Control of such

SSCs does not require meeting the level of stringency associated with safety-class

SSCs.

The Evaluation Guideline is not used for designating safety-significant SSCs.

Safety-class SSCs are designated to address public risk, which makes a dose

guideline at the site boundary a useful tool. Safety-significant SSCs address risk

for all individuals within the site boundary as well as additional defense in depth

for the public, making a dose guideline at any one point an artificial distinction

distorting the process of systematically evaluating SSCs.

TSRs covering SSCs ensuring defense in depth should generally correlate with

safety-significant SSC designation for defense in depth, but exact one -to-one

correlation is not required.

Specific administrative controls . This category of ACs is provided to ensure

that controls important to safety that are needed to prevent or mitigate an

accident scenario will be given equivalent attention in the safety basis

documents had that safety function been provided by a safety-class or safety-

significant SSC. Safety analyses shall establish the identification and functions

of SACs and the significances to safety of the functions of the SAC. The

established hierarchy of hazard controls requires that engineering controls with

an emphasis on safety-related SSCs be preferable to ACs or SACs due to the

inherent uncertainty of human performance. SACs may be used to help clarify

and implement an AC.

HA Z A R D AN A L Y S I S

The initial analytical effort for all facilities is a hazard analysis that systematically

identifies facility hazards and accident potentials through hazard identification and

hazard eva luation. The focus of the hazard analysis is on thoroughness and requires

evaluation of the complete spectrum of hazards and accidents. This largely qualitative

effort forms the basis for the entire safety analysis effort, including specifically

addressing defense in depth and protection of workers and the environment. Basic

industrial methods for hazard analysis, its interface with more structured quantitative

evaluations, and the basis for both have been described in references such as the

American Institute of Chemical Engineers Guidelines for Hazard Evaluation

Procedures (1992). OSHA has accepted these guidelines as the standard for

analytical adequacy in characterizing commercial chemical processes that perform the

same type of unit operations conducted at DOE nonreactor nuclear facilities.

Appropriately applied, they help fulfill the requirements of DSAs for Hazard Category

2 and 3 facilities as specified in 10CFR830.

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