Sequence Selection - s1027cn10026

DOE-STD-1027-92

Sequence Selection

The process for selecting postulated accident sequences used in the remainder of the

accident analysis process is critical to the SAR and must receive sufficient attention in

it. Accidents presented in an accident analysis section of a SAR include design-basis

accidents and discussions of beyond-design-basis events.

This element provides a means to reduce the information generated in the previous

element to a manageable set of sequences to be used for the remainder of the

accident analysis. The objective of the sequence selection element is to choose (1)

the unique sequences which could have major effect on workers or the public, and (2)

the typical sequences which would encompass all of the principal release

mechanisms. Sequence selection is discussed in more detail in relation to each of the

hazard categories.

Engineering Analysis

Engineering analysis identifies the physical relationships among the systems,

structures, and components, and the release mechanisms for the selected sequences.

It is a critical part of the analysis because it connects the facility, the hazardous

material, and the physical conditions during the postulated accident. This step is

critical to the development of the Technical Safety Requirements for the facility.

Consequence Analysis

The final element in the accident analysis is consequence analysis. This step

evaluates the effect of the postulated accident on the workers, the public, and the

environment. It includes source term evaluation and dose calculations. For some

facilities, consequence analysis may also include health effects assessment, accident

frequency estimates, or safety goal comparisons.

Nuclear Hazard Category 3 Facilities

4.1.2.a

DEFINITION

Hazard Analysis shows the potential for only significant localized consequences.

INTERPRETATION

Facilities with quantities of hazardous material which meet or exceed Table A.1 values

This category of facilities and hazards by definition cannot release the quantities of

materials which could threaten workers at adjacent facilities, the public, or the

environment. Thus, as DOE Order 5480.23 states in paragraph 4.f.(1).(c) of the

attachment, "For facilities of little hazard, or hazards in Category 3 level, the SAR may

be simple and short. In such cases all of the topics for the SAR listed in paragraph

8b(3) of this Order will not be necessary and, with proper technical bases, some topics