Potential Behavior of Depleted Uranium Penetrators under Shipping and Bulk Storage Accident ...

150 Pages·2007·15.53 MB·English

PNL-5415
UC-41
424
~~ ~ ~
Potential Behavior of
Depleted Uranium
Penetrators under Shipping
and Bulk Storage Accident
Conditions
J. Mishima
M. A. Parkhurst
R. 1. Scherpelz
D. E. Hadlock
March 1985
Prepared for
the U.S. Department of the Army
under a Related Services Agreement
with the U.S. Department of Energy
Contract DE-AC06-76RLO 1830
Pacific Northwest laboratory
Operated for the U.S. Department of Energy
by Battelle Memorial Institute
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PNL- 54 15
UC-41
33679000482952
POTENTIAL BEHAVIOR OF DEPLETED URANIUM
PENETRATORS UNDER SHIPPING AND BULK
STORAGE ACCIDENT CONDITIONS
J. Mishima
M. A. Parkhurst
R. I. Scherpelz
D. E. Hadlock, Project Manager
February 1985
Prepared for
Tank Ammunition Section
Munitions System Division
Large Caliber Weapons System Laboratory
Army Armament Research and Development Center
under a Related Services Agreement
with the U.S. Department of Energy
Contract DE-AC06-76RLO 1830
.
# Pacific Northwest Laboratory
Richland, Washington 99352
.
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ABSTRACT
An investigation of the potential hazard from airborne releases of
depleted uranium (DU) from the Army's M829 munitions was conducted at the
Pacific Northwest Laboratory. The study included: 1) assessing the char-
acteristics of DU oxide from an April 1983 burn test, 2) postulating condi-
tions of specific accident situations, and 3) reviewing laboratory and
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theoretical studies of oxidation and airborne transport of DU from accidents.
Results of the experimental measurements of the DU oxides were combined with
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atmospheric transport models and lung and kidney exposure data to help estab-
lish reasonable exclusion boundaries to protect personnel and the public at an
accident site.
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EXECUTIVE SUMMARY
In accordance with the Department of Defense's hazard classification test
requirements, the Army Armament Research and Development Center conducts a
testing program of its large caliber munitions. This hazard classification
testing includes tests of the explosive hazards associated with various
munitions under accident conditions, and transport classes are assigned to the
munitions based on the test results. The Army tests the behavior of these
rounds so that an exclusion area could be established around an accident site
to protect Army personnel and members of the general public.
Previous tests have focused on the potential explosive hazards and pene-
trator ejections resulting from fires during transport or bulk storage of the
munitions. More recently there has been a great deal of interest in the radio-
logical and toxicological hazards to downwind populations from the possible
airborne release of depleted uranium. The need to further investigate the
potential hazard from airborne releases was evident after tests with the M829
rounds showed that, under severe fire conditions, the penetrators remained in
the fire and were oxidized to powder rather than being ejected undamaged from
the fire.
A study (documented in this report) to investigate the potential hazard
from airborne releases was conducted with two objectives. The first objective
was to characterize the depleted uranium oxide samples taken from an April
1983 external heat test for particle size, morphology, and lung fluid
solubility. The second was to conduct a literature search on the uranium
oxidation rates, the characteristics of oxides generated during the fire, the
airborne release as a result of the fire, and the radiological/toxicological
hazards from inhaled uranium oxides.
Results of the DU oxide sample analysis showed that about 1%o f the
uranium oxide had a least linear diameter <lo urn. Particles <lo um are
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generally considered in the respirable range. A more sensitive measure of
respirable size is the measurement of the fraction that is 4 0 um in
aerodynamic equivalent diameter (AED). From 0.2% to 0.65% of the samples
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measured <10 pm AED. The particle size and the morphology indicated that a
maximum of 0.6% by weight (0.6 wt%) of the DU oxide was i n the respirable size
fraction and could become airborne.
Measurement of the solubility o f the DU oxide i n simulated interstitial
lung fluid demonstrated that 96.5% of the sample had not dissolved within
60 days. The sample for this analysis was small because only the <10 pm AED
fraction was used, but it provided sufficient evidence to conclude that the
uranium i n the sample should be classified as being 100% i n the Y class for .
calculations of retention and dose using the ICRP lung model. The Y class
includes compounds with dissolution half-times i n the lung of more than
100 days.
In the literature search, laboratory and theoretical studies of DU
oxidation and release from accidents that result i n fire are summarized. The
reaction rates, swelling and thermal stress, and variations i n these and other
properties are discussed as well as the compounds produced, their particle
size, morphology and solubility.
Downwind transport o f airborne DU from the accident site i s evaluated i n
terms of plume characterization and plume movement. Models used to calculate
particle entrainment and atmospheric transport are reviewed, and their capabil-
ities are analyzed. The application of the atmospheric transport calculations
to the hazard analysis starts with f i r s t identifying whether the main hazard
to workers or the public downwind o f the accident i s likely to be radiological
or toxicological i n nature. Establishing this requires the knowledge of
chemical form, solubility, and particle size of the uranium produced by the
fire, or the use o f worst-case assumptions. The chemical toxicity i s the
critical l i m i t for soluble uranium compounds, and the critical organ i s the
kidney. Insoluble compounds present a hazard primarily to the lungs. Chron-
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ically exposed occupational workers are limited to 0.2 mg/m for a 40-hr week
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or 0.6 mg/m for occasional short-term exposures (ACGIH 1983). Exposures to
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20 mg/m for soluble uranium compounds or 30 mg/m for insoluble ones are
.
designated as being the maximum levels that a person could be subjected to for
a
30 minutes without impairing escape or causing irreversible health effects
(Mackison, Stricoff and Partridge 1978).
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The exposure limits for toxicity are more conservative than most of the
radiological limits and thus protect from either type of insult. None of the
limits, however, are directly applicable to the accident situation, so derived
limits to determine exclusion boundaries are reviewed and their assumptions
are examined. The derived limits are applied to results from the char-
acterization study and are used to estimate the fraction of inhaled DU
deposited and retained in,the lung versus the fraction that i s transported to
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the kidney. Although it is not clear that DU in the M829 penetrators would
consistently produce the same relative amount of respirable aerosol, the use
of actual test results coupled with the atmospheric transport and lung and
kidney exposure data allows calculation of exposure levels and provides
pertinent input to the determination of reasonable exclusion boundaries that
will protect personnel and the general public.
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