Secondary Confinement cont'd

DOE-HDBK-1132-99

material processing, the functional requirements for secondary confinement

refer to the operating area boundary and the ventilation system serving the

operating area.

Design features incorporated into the secondary confinement system should

have been proven effective by extensive experience in similar applications or by

formal prototype testing. Such design features include the following:

Continuous monitoring capability should be provided to detect loss of

proper differential pressure with respect to the process area. Operating

areas should also be continuously monitored. Commensurate with the

potential hazards, consideration should be given to the use of redundant

sensors and alarms.

Permanent penetrations of the secondary confinement (e.g., pipes,

ducts) should have positive seals or isolation valves or double closure

with controlled secondary to primary leakage on pass-through

penetrations (e.g., personnel air locks and enclosed vestibules).

Ventilation systems associated with secondary confinement should be

designed with adequate capacity to provide proper direction and velocity

of airflow in the event of the largest credible breach in the barrier.

Secondary and tertiary barriers may exist in common such as a single

structural envelope (e.g., walls, roof slab, floor slab), provided the barrier

can withstand the effects of external events, and does not contain

access ways that allow the routine transfer of personnel, equipment, or

materials directly to the exterior of the facility. Access ways into the

interior of the single structural envelope should be designed so that the

access way is entered from another level of confinement.

Special features (e.g., air locks, enclosed vestibules) should be

considered for access through confinement barriers to minimize the

impact of facility access requirements on the ventilation system and to

prevent the release of radioactive airborne materials.

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