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DOE-HDBK-3010-94
4.0 Solids; Metals
4.2.1.1.2 O xid ation at E levated T em p eratu res B elow I gn ition T em p eratu re.
Stewart (1963) reported on oxides from heating small pieces (less than 13 g) of unalloyed and
delta-alloy plutonium metal to various temperatures in various atmospheres. Two shapes
were used: billets (cylinder 0.7 cm diameter by 1.0 cm long) and swarf (turnings). Various
experimental configurations were needed for different experimental conditions. The pertinent
data are tabulated in Table 4-1 with source data from the referenced document reproduced in
Tables A.28, A.29a, A.29b, and A.30 in Appendix A. The size distributions of airborne
materials are shown in Figures A.23 and A.24 in Appendix A.
Table 4-1. M easured ARFs During Oxidation of Unalloyed and
Delta-Phase Plutonium at Elevated Tem peratures in Air
(Tables 3, 5 and 7 - Stewart 1963)
M etal
M ass
Hum idity
Tem perature
m g H2O/l air
ARF
Phase
Specim en (g)
123 oC
delta
7.483
0.03
1.5E-3
(0.033 oxidized)
113 oC
delta
7.344
1.50
3.2E-5
(0.054 oxidized)
123 oC
delta
8.602
16.0
4.8E-6
(0.035 oxidized)
beta
11.021
0.03
1.4E-6
(0.57 oxidized)
beta
10.802
8.0
1.1E-6
(1.0 oxidized)
beta
7.191
8.0
3.3E-6
(0.76 oxidized)
113 oC
alpha
9.397
16.0
1.3E-6
(0.21 oxidized)
123 oC
beta
11.265
16.0
5.6E-7
(0.17 oxidized)
beta
8.154
16.0
1.0E-6
(0.65 oxidized)
*
Mass Median Diameter in m Aerodynamic Equivalent Diameter.
At temperatures below the ignition temperature (experiments performed at 113 and 123 oC),
the unalloyed and alloyed metal behave differently. The oxidation rate for the delta-phase
alloy is stepwise and two orders of magnitude less than for the unalloyed metal. The
difference is attributed to the formation of a protective oxide film (the crystalline matrix
spacing for delta-phase metal and the dioxide are very similar and the dioxide adheres to the
metal surface). The film must crack and fall away before additional oxidation can occur.
The particle size distribution of the bulk oxide generated is very wide (0.1 to 300 m Dg).
The oxidation and release rate experimentally observed were continuous during the oxidation
of unalloyed metal. Except for a single anomalous high release value measured for delta-
phase metal at 123 oC in low humidity air with a very low fraction oxidized (1.5E-3), the
ARFs for both types of metal phases are bounded by a release of 3E-5 (also very low
fraction oxidized) and ranging to a value of 6E-7. The measured size distribution as
Page 4-19


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