Powders - h3010v10145

DOE-HDBK-3010-94

4.0 Solids; Powders

4.4

POWDERS

For low-energy stresses, powders do not tend to significantly fragment. For high-energy

stresses considered in this document, the size fraction of powders of concern have relaxation

times on the order of fractions of a millisecond, and thus do not tend to present themselves

for fragmentation. Therefore, the amount of respirable material assumed airborne using this

handbook should not exceed the amount of respirable material originally present in the source

MAR, if that value is known. If the value is not known, and the values assessed to be

bounding specifically use as the RF the fraction of original MAR less than 10 m AED, an

RF of 0.1 can be assumed based on Ayer, et al. ( May 1988).

4.4.1 Thermal Stress

Experiments are reported by Mishima, Schwendiman and Radasch (July 1968, November

1968) covering the airborne suspension of particulate materials during the heating of various

compounds. Two types of situations are covered - the suspension of non-reactive powders

during heating in a flowing airstream and the suspension during oxidation of reactive

compounds in a flowing airstream.

Plutonium fluoride, oxalate, and air-dried oxalate powders withdrawn from production, air-

dried Pu nitrate from the low temperature drying of concentrated Pu nitrate solutions, or the

15 to ~ 150 m AED fraction from the air oxidation of Pu metal were placed in the shallow

depression of a stainless steel planchet on top of a graphite core used for induction heating.

A thermocouple in a 3.2-mm diameter well drilled into the side of the planchet measured the

temperature during the experiment. A 75-mm quartz bell that formed the bottom of a

42.2-mm i.d. quartz chimney surrounded the planchet. Air at a pre-determined flow was

drawn up and around the planchet, through the apparatus, and the entrained material was

collected on a glass fiber filter sealing the upper end of the chimney. At the flows used, the

nominal velocities through the chimney were adequate to carry particles from up to 17 m in

diameter at 0.1 m/s to ~ 300 m in diameter at a nominal velocity of 1.0 m/s. A 0.076-mm

thick mild steel liner covering the interior surface of the chimney was used to collect any

material lost to the wall during heating but analysis indicated no significant loss in any

experiment. Results from these analyses were not reported due to the uncertainty in results

created by the difficulty in the analytical separation of the high iron content from lining

dissolution solutions. The experimental apparatus is shown in Figures A.27a and A.27b in

Appendix A. The measured suspension rates during the heating of the plutonium solid

compounds are reproduced in Tables A.33, A.34, A.35, A.36 and A.37 also in Appendix A.

All sampling periods were one hour for all tests and, therefore, the ARFs are the same as the

suspension rates converted to fraction of source. The measured ARFs are the fraction of the

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