Industrial Hazards

DOE-STD-1136-2004

Guide of Good Practices for Occupational Radiological Protection in Uranium Facilities

2.6 INDUSTRIAL HAZARDS

The principal industrial hazards associated with uranium are fires, hydrogen generation, generation

of oxides of nitrogen, and associated mechanical hazards characteristic of heavy objects, i.e., back injuries

from lifting, dropping heavy parts on feet, etc. Hydrogen fluoride (HF) and oxides of nitrogen (NOx) are

by-products or reactants of common chemical processes. Hydrogen (H2) can be generated by reaction of

water with uranium metal, and finely divided uranium or uranium chips with a large surface area to

volume ratio can ignite spontaneously.

2.6.1 Hydrogen Fluoride

Hydrogen fluoride is an extremely corrosive acid that is relatively volatile in its anhydrous form.

Anhydrous HF is a reactant for the production of UF4 from UO3, a by-product of the production of UF4

from UF6, and is generated whenever UF6 is released to the atmosphere (H20 in air + UF6 → UO2F2 and

HF). External contact with HF results in chemical burns of the skin, while exposure to airborne HF causes

chemical burns/irritation of the eyes, nose, and throat. Significant inhalation can result in pulmonary

edema. Chronic exposure to excessive fluoride concentrations results in increased radiographic bone

density and may eventually cause fluorosis (osteosclerosis). In general, individuals can smell HF at levels

of 0.02-0.2 mg/m3, much lower than the TLV of 2.5 mg/m3. The TLV was set based primarily on the

irritation of eyes and mucous passages rather than on permanent damage. Because an airborne

concentration of 10 mg/m3 is intolerable, personnel exposed to such levels will evacuate the area if they are

able to do so. Exposure for as little as 15 minutes to an airborne concentration of 20-30 mg/m3 may prove

fatal (pulmonary edema). The AIHA Emergency Response Planning Guides (ERPGs) for HF are as

follows: ERPG-3, 42 mg/m3; ERPG-2, 17 mg/m3; and ERPG-1, 4 mg/m3. The NIOSH IDLH value is 25

mg/m3.

2.6.2 Nitric Compounds

Nitric acid is widely used for digesting uranium metal and uranium- bearing compounds and for

"pickling" metal products to inhibit oxidation. Concentrated nitric acid gives off fumes that cause

irritation to eyes, mucous membranes, and skin. Significant inhalation can result in pulmonary edema.

The ACGIH TLV-TWA and TLV-STEL values for nitric acid are 2 ppm and 4 ppm, respectively.

When uranium materials, especially metal, are dissolved in nitric acid, oxides of nitrogen (NO x)

are generated. The term NOx is applied to mixtures of nitric oxide (NO) and nitrogen dioxide (NO2). The

ACGIH TLV-TWA and STEL are 25 ppm and 35 ppm, respectively. Exposure to NO2 can cause eye

irritation, coughing, mucoid frothy sputum, shortness of breath, chest pain, pulmonary edema, cyanosis,

tachypnea (abnormal rapid breathing), and tachycardia (abnormal rapid heartbeat).

2.6.3 Hydrogen Gas

Hydrogen gas (H2) is used as a reactant in the production of UF4 from UF6 and in the reduction of

UO3 to UO2, an intermediate step in the production of UF4 from UO3. The H2 is usually generated by

dissociating ammonia, so associated ammonia rather than hydrogen is frequently identified as the reactant

in those processes. Any facility where H2 is used as a reactant should include design features (e.g., H2

monitors, roof vents, etc.) to ensure that hydrogen accumulations do not occur. Generally, H2 hazards and

control features are identified in facility Documented Safety Analyses. Hydrogen can also be generated

when moisture contacts uranium metal, especially finely divided uranium metal such as

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