Table 4-5. Measured ARFs During the Self-Sustained Air Oxidation of Large Specimens of Unalloyed and Delta Plutonium Metal

DOE-HDBK-3010-94

4.0 Solids; Metals

variations for the measurements would be a factor of ~ 20. The fraction of the residual

powder 20 m AED and less was <3.1E-4. The material was friable and the value may

represent some fraction of material fragmented during sieving.

Mishima (November 1966) reported the ARFs and RFs from the self-sustained air oxidation

of four large specimens of delta-phase and unalloyed plutonium metal. The three unalloyed

pieces ranged in mass from 455.5 g to 1770 g. The single delta-stabilized specimen was

997 g. The metal specimen was placed within a ring made of insulating material set upon a

sheet of insulating material (the metal would not sustain ignition in the absence of the

insulating material due to heat transfer to the metal enclosure). The top surface of the metal

specimen was ignited with a heliarc torch. Air was drawn into a quartz chimney placed

within one inch of the metal surface at a nominal velocity of 525 cm/s through the 2.685-in.

(68-mm) i.d. chimney. Airborne material was collected on a glass fiber filter sealing the end

of the chimney. Air was drawn through a side arm at 550 to 800 cm/s to collect airborne

materials on a membrane filter for size distribution analysis by transmission electron

microscopy. The experimental apparatus is shown in Figure A.16 and the results reproduced

in Table A.25 in Appendix A. The size distribution measured for material airborne during

oxidation of the largest metal specimen, considered representative of all measurements, is

reproduced as Figure A.17 in Appendix A. Pertinent data are listed in Table 4-5.

Table 4-5. Measured ARFs During the Self-Sustained Air Oxidation

of Large Specimens of Unalloyed and Delta Plutonium Metal

(Table II - Mishima November 1966)

Total Sampling

Weight Metal (g)

Time (min)

Form

ARF

569.8

Unalloyed

4.9E-4

1770

Unalloyed

1.4E-4

997

Delta

3.4E-5

455.5

Unalloyed

3.9E-6

With the limited data base, the ARFs do not appear to correlate with any measured

parameter (mass, form) but Haschke (July 1992) reports that the airborne release is time-

dependent. The largest ARF, ~ 5E-4, is in the range of but exceeds the 95% confidence

level value (1E-4) specified by Carter and Stewart (1970). Although the masses are larger,

the duration required for complete oxidation to self-extinguishment appear to be much less

than required for much smaller specimens used by Mishima (December 1965) and the ARFs

are two to four orders of magnitude larger. The principal differences between the conditions

under which these measurements and the previous measurements were made are the specimen

masses (larger) and air flow patterns (up and around at higher nominal velocities).

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