Oxidation of Depleted Uranium (DU) Rods at Elevated Temperatures in a Fire

DOE-HDBK-3010-94

4.0 Solids; Metals

Carter and Stewart performed experiments to measure characteristics of airborne uranium

from molten metal under static (no metal movement) and dynamic (free-fall drop) conditions.

The experimental apparatus and procedures were covered in Subsection 4.2.1.1.4. The mean

and 95% confidence level ARF x RFs from the oxidation of static molten metal with airflow

around and over the metal were 1.1E-4 and 3.6E-4 respectively.

A . O xid ation of D ep leted U ran iu m (D U ) R od s at E levated T em p eratu res in a

F ire. Elder and Tinkle (December 1980) performed a series of experiments on DU

rods used as penetrators in armor-defeating weapons. The rods were made of

staballoy (beta-stabilized uranium, 99.25% uranium + 0.75% titanium) with a

nominal diameter of 25.9-mm (~ 1 inch), a length of 0.345 m (13.6 inches), and

weighing 3355 +/- 3 grams. The rods were subjected to oxidizing conditions (heat

+ air or air-carbon dioxide atmospheres) with a test configuration for each set of

conditions. The various testing configurations are shown in Figure A.25 and A.26 in

Appendix A. The rods were heated in a rack in an upflow of air. In the first three

tests, the heat was generated from either ignited uranium turnings or munitions

propellant. In the fourth test (burn 4), heat was supplied by 10 batches of packing

materials (wood and paper). Observations indicated that the rods in the first three

tests under went very little if any oxidation. From 42% to 47% of the three rods

tested in Burn 4 were oxidized greatly exceeding the largest value for fraction

oxidized in the laboratory study (30%) and was attributed to the spalling of the oxide

coat from the temperature fluctuations resulting from introduction of the 10 batches of

fuel. Individual 5-min air samples taken during portions of four fuel additions show

apparent airborne concentrations ranging from 4.2 to 783 mg U/m3 with fractions

<10 m AED from 20% to 62%. The times during the oxidation process when the

samples were extracted are not reported and the great variation in the mass airborne

concentrations makes determining the ARF difficult.

The oxidation rate and airborne release were measured during thirteen laboratory

experiments in air or 50% air - 50% carbon dioxide at temperatures from 500 to

1000 oC. In twelve of the tests, a gas velocity of 2.23 m/s (5 mph) was passed around

the oxidizing rod. In one experiment (air at 700 oC), the test was performed under

static conditions (no gas flow). No self-sustained reaction was observed under any of

the test conditions. The fractions oxidized under these conditions ranged from 6.0% to

30.2% (original data tables reproduced as Table A.32 in Appendix A). The total

aerosol mass (summation of the high volume filter sample, precutter and cascade

impactor stages + back-up filter) are shown in Figure 4-9 reproduced from the

reference document. It is difficult to ascertain if the presence of carbon dioxide has

any discernable effect upon the airborne release due to experimental scatter and

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