Self-sustained Oxidation Above th e Ignition Temperature cont'd

DOE-HDBK-3010-94

4.0 Solids; Metals

gasoline fire in a chimney). The ARF for the two trials (the plutonium metal was

incompletely oxidized in one of the two experiments and the results are normalized for the

fraction oxidized) were 1E-2 and 3E-2 with RFs of 0.01 and 0.008 respectively. The

resultant ARF x RF values would be 1E-4 and 3E-4.

Eidson and Kanapilly (February 1983) measured the airborne release from heating small

specimens of delta-stabilized Pu metal in various gas mixtures. The atmospheres were air,

inert (argon), reducing (hydrogen or hydrogen-nitrogen in argon) and gas mixture from the

decomposition of fuel or Insensitive High Explosives. Pu metal pieces 0.5 g and 1.0 g were

placed in a tantalum crucible with a boat underneath to collect any powder residue that fell

out of the crucible. A heated reaction atmosphere was introduced into the stainless steel foil-

lined quartz tube surrounding the crucible-boat and passed into a foil-lined aerosol chamber.

The particulate materials passing through the apparatus were collected on filters sealing the

apparatus and exhaust. Airborne release was the summation of the activity collected on the

filters and estimates of deposition based upon the activity collected on the foil samples

extrapolated to the entire surface area of the tube and aerosol chamber. In later experiments,

the entire tube and chamber were lined and provided estimates of deposition that appeared to

be lower than estimates used in the earlier experiment. The size distribution and morphology

of the airborne material are based upon transmission electron microscopy of material

collected in the aerosol chamber. A schematic drawing of the system is reproduced as

Figure A.18 and the experimental results are reproduced in Table A.26 in Appendix A. The

pertinent experimental data and measured ARFs reported are shown in Table 4-6.

The ARFs appear to be in reasonable agreement (order of magnitude) with the ARFs

specified by Carter and Stewart (1970) for Pu metal burning in air or melting. The

maximum measured ARF is ~ 5E-3 exceeding Carter and Stewart's 95% confidence level

value (1E-4), and that measured by Mishima (November 1966) (5E-4). The bounding ARF

measured is from the values determined during the initial experiments and, according to the

authors, may well be overestimated due to accounting for material that may not have been

related to airborne release. The median ARF is 3E-5 with an average value of ~ 3E-4.

The size distribution of the residual powder was determined by a combination of 320 mesh

sieve (~ 62 m LLD - the sieves are vibrated during use to cause the particle to bounce on

the sieve screen and the material passing through the screen indicates that the non-spherical

particles have at least one dimension of the size of the opening) and sedimentation

measurements. The range of residual powder in the less than 62 m LLD was 18% to 41%

with MMDs from 5.7 to 7.5 m geometric diameter (Dg). The material was primarily PuO2

(x-ray diffraction) with some unburned metal particles. The authors conclusions were that

1) atmosphere and temperature affected the formation of the powder residue but did not

affect aerosol formation, and 2) mass-to-surface ratio did not have a discernible affect on

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