Air Supply - doe-std-1128-98

DOE-STD-1128-98

C.5.1.3

Air Supply

Supply air should be appropriately filtered and conditioned in accordance

with operational requirements and with the levels recommended for

comfort.

The ventilation rate in process areas where uncontained radioactive

materials are handled should be from 12 to 60 air changes per hour

(ORNL, 1970) depending on whether the area is normally occupied by

workers, the need for removal of process or decay heat, and the need for

removal of decay fumes. A minimum of eight air changes per hour

should be provided in support facilities within the process area. Adequate

air filters should be used at the intake of the ventilation supply system to

minimize dust in the process area and to reduce the dust loading on

HEPA filters.

A downward air-flow pattern should be provided at worker locations to

direct air from any potential leak point down and away from the worker's

face. Consideration should be given to the distribution of inlet air

through a number of small ports or by slot-type distributors to decrease

the possible occurrence of "dead spots" with little air circulation.

Glove boxes, conveyors, and other systems that require a controlled

atmosphere may be equipped with a recirculating air system. All parts of

the system should operate at air pressures that are negative with respect

to the room. Process enclosures that use normal air may receive their air

supply from the room through dust-stop and HEPA filters mounted on

the glove box.

Consideration should be given to isolating process rooms from each

other during accidents. The principle of compartmentation and separation

should be extended to systems handling ventilation in working areas by

the most practicable use of individual ventilation systems. Emergency

back-up should be provided through combinations of manifolds and

damper cutovers between adjacent individual ventilation systems.

Redundancy can be minimized by the provision of a back-up unit for

each two individual systems.

C.5.1.4

Exhaust Systems

The number of required exhaust-filtration stages from any area of the

facility should be determined by analysis to limit quantities and

concentrations of airborne radioactive or toxic material released to the

environment during normal and accident conditions. Materials released

should be in conformance with applicable standards, policies, and

guidelines. In general, each exhaust filter system should consist of a

minimum of two HEPA filters for room air and three HEPA filters in

series for glove-box or hood-exhaust air. Only two stages of glove-box or

hood exhaust filters need to be equipped for in-place testing.

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