General Safety Design Guidance

DOE-HDBK-6004-99

General Safety Design Guidance

The confinement system design should establish the features which minimize the spread of both

gaseous and particulate contamination throughout the facility. The confinement systems discussed

here are those that are beyond the boundary of the vacuum vessel and its ancillary systems.

In order to establish the confinement areas for the facility outside the vacuum vessel, a safety analysis

considering normal and accident conditions should be performed. The resultant safety classification

of confinement zones from the safety analysis should be the basis for determining the ventilation

system design requirements as well as the architectural/structural requirements for the respective

confinement areas. (Burchsted 76)

The confinement systems should be divided into the following confinement systems as necessary to

support the safety analysis:

1. The ex-vessel primary confinement system should consist of structural barriers and process

enclosures such as gloveboxes, piping, tanks and any associated ductwork and their associated

ventilation and air cleaning systems that are required to prevent the release of hazardous material

to areas beyond the confinement boundary. In addition, credible breaches in the primary

confinement barrier should be compensated for by provision of adequate inflow of air or safe

collection of hazardous material that escapes the confinement. This is accomplished by multistage

HEPA filtration of the exhaust or by an equivalent filtering capability. The exhaust ventilation

system must be sized to ensure adequate inflow of air in the event of the largest credible breach

of confinement.

2. The secondary confinement system should consist of the walls, roofs and associated ventilation

systems that confine any potential release of hazardous materials from the primary confinement

system. This system includes the operating area boundary and the ventilation system and any

associated air cleaning systems serving the operating area. The ventilation system should be

designed to ensure proper airflow direction and velocity to counteract the largest credible breach

in secondary confinement barrier. Penetrations of the secondary confinement barrier should be

provided with positive seals to prevent migration of contamination out of the secondary

confinement area.

3. The tertiary confinement system should consist of the walls, floor, roof and associated exhaust

system of the process facility. It is the final barrier to release of hazardous material to the

environment. This level of confinement should be provided for the space bounding the secondary

confinement which is not expected to become contaminated.

Potential System Safety Functions

The confinement systems along with their associated HVAC systems should be designed to provide

the following functions for the facility:

1. Normal Operation:

a) Prevent and control the spread of gaseous and particulate contamination. This is

accomplished by controlling confinement zone differential pressures as well as