rimetric methods respond to whole groups of com-
produce the effectiveness of the previous designs. Cur-
pounds, such as nitroaromatics or nitramines/nitrate
rently, an HGD system, composed of a propane air
esters, they are more suitable than immunoassay kits
heater and distribution assembly, a thermal blanket (i.e.,
for screening for residues of explosives. In addition,
insulation and chicken wire) cover, thermocouples, and
these colorimeteric tests use a solvent extraction step.
data acquisition system, is being proposed for this task.
Therefore, one aliquot from a solvent extract, wipe, or
This HGD system will be able to treat a scrap pile that
may be as large as 2.4 6.1 9.1 m (h, w, l). Because
rinse sample could be used to initially screen for the
presence of the explosives (nitroaromatic, nitramine and
there are several design changes from previous tests,
nitrate esters, and ammonium picrate/picric acid), and
temperaturetime (heat soak) criteria for the decontami-
a second aliquot could be analyzed with an analyte-
nation process will have to be established. Therefore,
specific method of detection.
in addition to monitoring the temperature at several
Detailed analysis of those samples positively
locations in the scrap pile and the treatment period, QA
responding to field screening tests is necessary to
samples should be placed at strategic locations (near
specify which explosives are present. In addition, an
thermocouples) so that how completely the analyte de-
on-site analysis could help identify a suspect aggregate
composes can be assessed.
of materials as being an explosive. Unconsumed ex-
This report, therefore, addresses two separate top-
plosive materials are likely to associate with munitions
ics: first, it investigates methods for detecting and char-
that go low order (do not explode completely). There-
acterizing residues of explosives on range scrap, and,
fore, as a precaution, large pieces of debris that can be
second, it develops QA samples that can be used to
recognized as a munition should be treated with ex-
verify the performance of the HGD system. The even-
treme care. Samples taken of unexploded residues are
tual product of this effort and others is to document
likely to have concentrations in the extract that require
protocols that can be used as guidance for characteriz-
dilution prior to shipping and instrumental analysis.
ing range scrap and verifying HGD systems.
Analyte-specific analysis could be done on-site with
a field-portable gas chromatograph (GC) equipped with
MATERIALS
a thermionic detector (TID) that is selective for com-
pounds containing nitro (NO2) functional groups
Design criteria for the QA samples
(Hewitt and Jenkins 1999, Hewitt et al. 2000). The SRI
The quality assurance (QA) samples must resemble
8610C GC/TID (Torrance, California) is well suited for
the metallic materials to be treated and be spiked with
this purpose because it operates with little auxiliary
approximately 1 mg quantities of the explosives
support. A TID is an electrically heated emission source
analytes found at a given facility. Henceforth, the metal
composed of a ceramic bead impregnated with an al-
materials (plates) that were spiked will be called cou-
kali metal (Patterson 1986). When compounds contain-
pons. In addition to these coupons, pieces of range-
ing nitro functional groups, e.g., nitroaromatic,
contaminated scrap will also be used as part of the QA
nitramine, and nitrate esters, impinge on the surface of
program. These pieces of scrap should have visible signs
a TID, they are selectively ionized and measured with
of residues of explosives on their surfaces and have
a collector electrode. This instrument is very transport-
given a positive response to a screening test. Both the
able, robust, and economical (less than 00), and is
coupons and representative range scrap should be
capable of rapidly detecting all of previously mentioned
housed in a chamber that can be easily recovered from
explosives, with the exception of ammonium picrate
the materials after HGD treatment. Lastly, this cham-
and nitrocellulose (Hewitt et al. 2000). Off-site analy-
ber and the coupons must maintain their physical
sis could be done using either Method 8330 or 8095
integrity over a 6-hour period while being heated to
(U.S. EPA 1995, 1999).
1000F (538C).
HGD has been successfully demonstrated at the
Cornhusker Army Ammunition Plant, Nebraska;
Coupons
Hawthorne Army Depot, Nevada; and the Alabama
Metal coupons were made by cutting 1.5- 1.5-cm
Ammunition Plant, Alabama (Parson 1998). These tri-
squares from a 0.8-mm-thick sheet of aluminum and a
als used either existing buildings or metal bins to hold
1.6-mm-thick sheet of steel. A dimple (slight depres-
the metal scrap during thermal treatment and often in-
sion) was made in the center of each coupon with a
cluded an off-gas treatment system. Since large piles
4.8-mm center punch to hold (concentrate) the liquid
of range scrap exist at Army, Navy, and Air Force in-
aliquots used to transfer the analytes. Next, all the sur-
stallations, a HGD system that is portable and uses lo-
faces of the steel coupons were rapidly oxidized using
cally obtainable materials for the majority of its con-
dilute solutions of hydrochloric and nitric acid and aque-
struction should be more cost effective, assuming it can
2
Previous Page
