Tertiary Confinement

DOE-HDBK-1132-99

The use of stack-vented rupture disks, seal pots, or bubbler traps should

be considered to prevent overpressurization and potential explosive

disruption of the secondary confinement system.

When a pipe is used as the primary confinement barrier for materials,

and the pipe exits a secondary confinement, the secondary confinement

should be provided by a double-walled pipe of other encasement. In

areas within the facility, the use of double-walled pipe should be

considered. Leakage monitoring should be provided to detect leakage

into the space between the primary pipe and the secondary confinement

barrier. (See Resource Conservation and Recovery Act requirements in

40 Code of Federal Regulations (CFR) 264.193, Containment and

Detection of Releases, and 40 CFR 265.193, Containment and

Detection of Releases.)

When primary confinement includes ductwork, the considerations in the

previous bullet should be applied to the ductwork. Transition from

primary to secondary confinement typically occurs downstream of air

cleaning devices, such as high-efficiency particulate air (HEPA) filters

and adsorbers.

Tertiary Confinement. Tertiary confinement is provided by the building or outer

1.1.5

structure of the facility. For some accidents, it represents the final barrier to

release of hazardous material to the environment; for others, it is a barrier that

protects other parts of the facility from damage.

ALARA concepts should be incorporated in tertiary confinement system design

to minimize exposure to operators, the public, and the environment.

1.1.6

Confinement Ventilation Systems. The design of a confinement ventilation

system ensures the desired airflow at all times and specifically when personnel

access doors or hatches are open. When necessary, air locks or enclosed

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