Airborne Wastes

DOE-STD-1136-2004

Guide of Good Practices for Occupational Radiation Protection in Uranium Facilities

8.3.1 Airborne Wastes

Ventilation control systems within a plant are designed to move air from outside "clean" areas to

process areas and then to air-cleanup systems. Occupied area off-gas systems are also vented to the

atmosphere and may have cleanup systems of their own. Process off-gas treatment systems consist of any

or all of the following:

Wet scrubbers are generally used in dusty process off-gas situations, in which large amounts of

uranium are present. The scrubbers are capable of removing and processing large quantities and serve as a

prefilter to the remaining cleanup units.

Prefilter systems other than the wet scrubber are bag filters or other rough/coarse filters. The

prefilters are used to remove significant quantities of particulate material from the air off-gas and are

generally placed before high-efficiency particulate air (HEPA) filters in order to extend the life of the

more expensive filters.

HEPA filters generally are the final filter in the process off-gas and serve to reduce the

particulate effluent to insignificant or permissible levels. They may be placed in series to provide the

required filtering efficiency. See section 8.3.3 for disposition of HEPA filters.

8.3.2 Liquid Waste

Because liquid effluents are generally released to the environment, liquid wastes are of equal

concern with airborne wastes. Liquid effluents become available for dispersion and reconcentration in food

chains, and may otherwise result in population exposure potential. In the case of liquid wastes, the concern

for chemical pollutants is generally of equal concern to that of radiological contaminants. Liquid process

wastes are generally collected in hold tanks, monitored, processed or treated, and released.

Hold tanks are used to collect liquid effluent prior to release in order that analyses can be

performed to establish that the concentrations or total quantities are below permissible levels prior to

release. The liquid can be processed or treated to remove radioactive material or neutralize chemicals.

Settling basins are frequently used to provide a means of reducing effluents further before

releasing them to offsite areas.

Filtration is a simple method of removing insoluble particulate materials entrained in the liquid

streams. For some processes, it is an effective and inexpensive method. The particulate material collected

and filter must be periodically removed and treated as solid waste.

Ion exchange is a cleanup system for removing soluble ions from the liquid streams by collecting

the material on resin columns. The contaminants must be periodically removed by a regeneration process

and the materials processed, concentrated, etc., or by replacing the resin completely and treating it as solid

waste.

Conversion to solid forms is a function of nearly all the processes mentioned which converts the

materials removed from the liquid and airborne waste streams to more manageable forms for handling and

permanent disposal.

8-3