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
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:
buffer seal exhaust stations, and
wet-air evaluation stations.