Potential Sources of Airborne Contamination

DOE-STD-1136-2004

Guide of Good Practices for Occupational Radiological Protection in Uranium Facilities

Potential Sources of Airborne Contamination

Virtually every work site has at least one of the fundamental mechanisms for the generation and

suspension of particulate material. The following descriptions of some of the basic mechanisms of

aerosol generation are intended to help radiation safety personnel recognize processes which have

inherently higher risk:

a. mechanical fragmentation, i.e., grinding, abrasive saws, sandblasting.

b. combustion, burning materials producing smoke, fumes, etc.

c. heating - many materials produce aerosols when heated, without actually igniting.

d. formation from bubbles, foams, or highly agitated liquids - fine solid aerosol particles can form

from larger, evaporating liquid droplets.

e. condensation of liquid or solid particles from the gas phase.

formation of particles from the products of gas-phase reactions, e.g., UF6 + 2 H2O → UO2F2 + 4

HF.

g. formation of solid, radioactive nuclides from gaseous parent nuclides - these radionuclides

usually attach to existing, nonradioactive aerosol particles.

h. adsorption of gaseous, radioactive nuclides on non-radioactive aerosols.

The program designer should be familiar with the routines and working habits of workers, especially

those in situations where there is a greater potential for generating locally high concentrations of airborne

contamination. This will assist in planning for exposure prevention and in selecting suitable sampling

a. Worker location and mobility - If the worker stays in a fixed location, fixed breathing- zone

sampling may be useful for individual exposure estimation. This sampling may be performed

using moderate flow-rate pumps (30 to 90 L min-1) which can be located within a few feet of the

worker. Mobile workers should be surveyed using PAS to obtain a breathing-zone sample.

b. Direct versus remote handling of radioactive material - Remote-handling facilities such as hot cells

or caves usually restrict the workers to a fixed location. Well- located fixed sampling heads may be

adequate for breathing-zone sampling at these work areas, provided that they have been properly

located. As previously noted in this section, determining the proper sampling points for fixed

breathing- zone sampling at fume hoods, glove boxes, etc., is not a straightforward exercise, and

PAS may be the most expedient means for sampling a worker's true breathing zone.

Direct-handling is commonly performed on material with relatively low intrinsic hazard, e.g.,

uranium metal or compounds. This sort of material may be moved around the work site and

directly manipulated at a number of locations. Fixed breathing- zone samplers usually will be

unsatisfactory in these situations, and PASs would be required for estimating an individual

worker's exposure in DAC-hours.

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