Uranium - h3010v10123

DOE-HDBK-3010-94

4.0 Solids; Metals

up to 0.5 m in diameter. The AMAD of the aggregates was 1 to 2 m with geometric

standard deviations of ~ 1.5. The size distribution of the airborne material from free-fall of

a 400-m drop as determined by the spiral centrifuge is reproduced as Figure A.22

(Appendix A).

Chatfield (1969) reported results of exploding wire experiments primarily to determine the

morphology and solubility of the particulate materials generated. Plutonium wire, 0.75-mm,

or plutonium wire encased in 2-mm sodium metal tubing were placed in heavy current

electrodes in the side of a 2.5-liter vessel. Energy of 4000 J accumulated in a capacitor bank

was discharged at 10 kV vaporizing the wire at a very high temperature (peak temperature

~ 50,000 oK). The fume formed by the condensation was collected directly on carbon-

coated electron microscope grids with the remainder exhausted through a membrane filter.

All the Pu or Pu-Na involved was made airborne. The Pu fume was composed of linear

aggregates of generally spherical particles <0.2 m in diameter. It was observed that in

some cases only particles of similar size appeared to form aggregates. The MMD of the

aggregate was 1.4 m with a very narrow distribution. The size distribution of the aerosol is

plotted in Figure 4-7 reproduced from the referenced source and, since the diameters plotted

are Geometric Diameters, indicates that essentially all of the airborne material is in the

respirable fraction.

On the basis of the experimental data presented, the ARF and RF is either 5E-1 and 1.0 or

1E+0 and 0.4. Based on a combination of values from these experiments, the bounding

ARF and RF values assessed for this handbook are 1E+0 and 0.5.

4.2.1.2

U ran iu m

Mishima, et al. (March 1985) reviewed the published literature on uranium behavior under

fire conditions. For natural or depleted uranium or uranium with 235U enrichment <10%,

the toxic hazard of uranium as a heavy metal is of greater concern than the radiological

hazard. The toxicological hazard from uranium results from transport of inhaled, soluble

uranium compounds to the kidneys. For non-volatile (soluble and non-soluble) materials to

be an inhalation hazard, the size of the particles/aggregates must be 10 m AED (more

probably 3 m AED) or less. For normal and depleted uranium, the materials must be

soluble. For uranium with enrichments >10%, the radiological hazard is of concern and the

solubility of the uranium in interstitial lung fluids determines the critical organ. Fire is a

phenomenon that could subdivide uranium metal by conversion to the oxides.

Due to the similarity in matrix spacing, hyperstoichiometric uranium dioxide formed at the

metal-atmosphere interface is adhering and limits oxygen availability. At temperatures

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