[ RadSafe ] DU

[Earley, Jack N]

I don't recall anyone referencing DOE-HDBK-3010-94 in the DU discussion, and I apologize if this has already been addressed, but since I'm doing some (non-DU) atmospheric modeling I thought this might be useful to some who haven't seen it.
 
B. Review of Experimental Studies on Airborne Release From Depleted Uranium 

Munitions. Jette et al. (August 1989) reviewed the published information available on the characteristics of the DU particles suspended during testing (firing of kinetic energy rounds against hard targets, burn tests during hazard classification of rounds prior to deployment) of the munitions and one study on the characteristics of the aerosols from the explosive ejection of molten metal droplets. Many studies have been performed on the DU particles formed by the impact of penetrators against hard targets (Gilchrist and Nicola, January 1979; Glissmeyer and Mishima, November 1979; Chambers et al., October 1982; Sutter et al., January 1985; Wilsey and Bloore, May 1989; Parkhurst et al., April 1990; Jette, Mishima and Hadlock, August 1990). Generally, a substantial portion of the mass of DU in the penetrator becomes airborne by the impact against hard targets (armor) of sufficient thickness to expend most of the energy of the kinetic round (up to 80%). The size of the airborne material is very fine with fractions in the 10 μm AED and less range of 0.34 to 1.0. The airborne materials are predominantly U3O8. Up to 50% of the particles in the respirable fraction may be "D" class (dissolution halftime <10 days).

The other large group of studies providing information on the potential behavior of uranium under accident conditions are the hazard classification test conducted on munitions prior to deployment (Gilchrist, Parker and Mishima, March 1978; Hooker et al., March 1985; Haggard et al., July 1986; Parkhurst et al., March 1990). A predetermined number of boxes of munitions are subjected to an intense wood-fuel oil fire. The distance large fragments (pieces of munitions components and cases, packing) are ejected and the thermal and blast levels are determined to establish the exclusion area requirements in the event of accidents in transport and storage. In all cases, no airborne DU was collected in the air samplers set downwind at various distances downwind of the fire. Size distributions of the residual oxide powders (predominantly U3O8) were determined and estimates of the respirable fraction are based on the presence of particles of 10 μm and less AED in the residual oxide. The size distributions measured show less than 0.01 of the residual oxides are in the respirable size range. The material in the respirable fraction is much less soluble than the airborne oxide from impact tests ranging from 96% to 100% in the "Y" class.

>From the data reproduced in Figure 4-11 from Carter and Stewart (1970), a geometric mean ARF x RF of 1E-4 was reported. The 95% confidence level ARF x RF of 4E-4 reported by Carter and Stewart (1970) is exceeded by the ARF and RF estimated for tests performed by Elder and Tinkle (December 1980), where the gas flow and temperatures used exceeded those used by Carter and Stewart (1970). Six of nine ARF x RF values obtained are less than 1E-3, with the greater values at the higher temperatures (900 oC). The ARF and RF values of 1E-3 and 1.0 are assessed to be bounding for this thermal stress configuration. The value for the lung solubility class is assumed to be that determined for the sintered oxides collected from wood-oil fires involving DU rods in munitions (i.e., >95% "Y" class with the remainder being "D" class uranium). This value is assessed to be bounding for the issue of lung solubility class.

 
Jack Earley
Health Physicist
509.372.9532