Airborne Effluents cont'd

DOE-HDBK-1132-99

Airborne effluents from confinement areas should be exhausted through a

ventilation system designed to remove hazardous particulate material, vapors,

or gases. ALARA should be implemented to minimize effluent concentrations

and quantities released for hazardous materials. Isokinetic sampling should be

provided for effluent streams that are expected to contain particulate

radionuclides. After HEPA filter installations, anisokinetic sampling may be

satisfactory, due to the small particle sizes in the effluent.

Consideration should be given to including process confinement off-gas

treatment systems to preclude the accumulation of potentially flammable

quantities of hydrogen generated by radiolysis or chemical reactions within

process equipment. Vent streams with the potential of containing significant

quantities of radioactive material should be processed by an off-gas cleanup

system before being exhausted to the environment.

The following additional features should be considered in off-gas systems:

providing vents from liquid components with traps and drains to prevent

inadvertent flooding of off-gas systems;

neutralizing corrosive gases and particles from vats, scrubbers, and

similar equipment in gloveboxes before they reach the HEPA off-gas

filters;

equipping vent streams containing UF 6 with chemical traps to remove

radionuclides from the gases before they are vented to the atmosphere.

The following vents are typically equipped with traps:

purge cascade,

cold recovery,

buffer seal exhaust stations, and

wet-air evaluation stations.

I-44