Chemical Versus Radiological Hazards

DOE-STD-1136-2004

Guide of Good Practices for Occupational Radiological Protection in Uranium Facilities

This listing is intended to provide general guidance only, as a given material's transportability will

depend upon a number of parameters including its processing history. It is recommended that each facility

determine the transportability of materials it handles using one of the accepted techniques. Physical form

influences potential hazards since non-dispersible forms generally do not constitute an ingestion or

inhalation hazard.

Because inhalation of uranium potentially poses both radiological and toxic hazards, one must

determine which hazard is most limiting and whether or not either hazard can be ignored under certain

circumstances. When radiological hazards are limiting, chemical hazards can generally be neglected,

except in overexposure situations. When chemical hazards are limiting, radiological hazards can be

neglected only if radiation doses are below regulatory concern. Radiological monitoring is required by

DOE for individuals who are likely to exceed 100 millirem CEDE in a year. Therefore, it is prudent to

calculate organ doses and CEDE for all confirmed intakes, since additional exposures in the same year

may result in a total dose exceeding the mandatory individual monitoring threshold. Even in low-potential

exposure level situations, a comprehensive dosimetry/control program can prove invaluable in public

relations concerning possible future legal litigation.

The limiting hazard (chemical or radiological) depends on the transportability (solubility in body

fluids), enrichment, and duration of exposure (acute or chronic). As discussed in Section 2.4, the "no

effect" value of intake corresponds to a kidney burden of 0.337 mg. The 0.337 mg kidney burden and

ICRP Publication 30 metabolic models are used in the following examples to determine the relative

hazards for acute exposure situations.

The 0.337 mg kidney burden corresponds to a chronic exposure of 0.07 mg/m3. OSHA exposure

limits for uranium are 0.05 mg/m3 for soluble forms and 0.25 mg/m3 for insoluble forms. These exposure

limits are used to determine the relative hazards for chronic exposure situations. For radiological

considerations, soluble forms of uranium are considered to be Class D and insoluble forms, Classes W and

To determine which hazard is limiting for an acute exposure, the intake corresponding to "no

effect" kidney burden is first calculated and appropriate annual limit on intake (ALI) determined. The

formula for specific activity is solved in order to determine the enrichment at which the "no effect"

intake is equal to one ALI. For chronic exposure scenarios, the OSHA exposure limit and appropriate

derived air concentration (DAC) are used. The formula for specific activity is solved to determine the

enrichment at which the DAC is equal to the OSHA limit. These enrichments form the "dividing line"

between chemical and radiological effects as the limiting hazard. Exposures to higher enrichments are

limited by radiological effects; exposures to lower enrichments by chemical effects.

Example 3a provides the methodology for determining the "dividing line" enrichment for the acute

exposure scenario. Example 3b provides the methodology used for the chronic exposure scenario. The

following variables are used in these examples:

fb = fraction of inhaled uranium that promptly enters the bloodstream

fk = fraction of uranium in bloodstream that enters kidneys

SA = specific activity of uranium in microCi/g obtained from ALI/intake or DAC/concentration

Br = breathing rate for standard man = 2,400 m 3/year

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