D Taggant and Marker Concepts
To supplement its knowledge of current taggant and marker technologies, the Committee on Smokeless and Black Powder listened to brief presentations from a variety of vendors on March 6, 1998. The paragraphs below summarize the presentations to the committee.1
Taggant Presentations
Biocode, Inc.
Biocode, Inc., uses a molecular binding pair technology; small organic chemicals are used as taggants, and code reading is accomplished by immunoassay. The material may by adsorbed to a substrate and may wash out in water. Material costs are estimated at pennies per unit, and applications to gasoline tagging are reported to be on the order of hundredths of a cent per gallon. The taggant could go in during manufacture or into the finished product. The technology has been used for clinical diagnostics and food and environmental testing. The technology has been employed in pharmaceutical, petrochemical, and agricultural industries.2
Caribbean Microparticles
Caribbean Microparticles Corp. proposed the use of uniform polymeric microbeads (2–20 microns) for tagging powders (>1,000 microns). Individual populations of physically differing taggants could be mixed to provide a specific code. Dispersion of the microbeads would be best conducted in a liquid, but could be accomplished through dry mixing. These particles are hydrophobic and adhere to the powder particles so that washing, even with surfactants, does not remove them. Since identification of the specific populations is all that is required, only a representative sample of particles need be examined. Quantitative recovery of particles is not necessary. This technology is presently used in the tagging of documents and tracing of stamps, and has undergone survivability tests in shotgun blasts.3
Innovative Biosystems, Inc.
Innovative Biosystems, Inc., proposed addition of single-strand DNA, called GenetagTM, to powders. DNA amplification would be accomplished through polymerase chain reaction (PCR) techniques. The genetic material was reported to survive temperatures of 60 °C for 1 year and to have been tested with powders through burning, simulated explosions, and shotgun blasts, with PCR amplification delivering readable codes. Company estimated costs are $500 to $ 1,000 for a 10k to 60k lb. batch with one taggant code, adding at the 7 ppm level. Cross-contamination and environmental persistence have not been fully studied.4
Isotag LLC
Isotag LLC proposed a mass enhanced molecular twin concept through isotopic substitution in explosive samples and identification with mass spectroscopy. Test explosions have been performed with 1 to 5 lb. tagged lots, and a 2,000 lb. lot of ammonium nitrate-fuel oil, tagged at ppb concentration, was exploded with reported postblast identification of codes. Analysis may be performed on dirt or debris samples. Studies have not been done using this technology with black powder. This technology has been used to tag lubricants, gasoline, and adhesives.5
Materials Research Center and Mo-Sci Corporation
The Materials Research Center of University of Missouri-Rolla and Mo-Sci Corporation proposed the addition to powders of microscopic glass spheres encapsulating inert common and rare earth elements. Identification would be achieved through scanning-electron microscopy of surviving glass microspheres recovered from bomb residue. The technology has been tested on exploded pipe bombs and is reportedly stable to 3,000 °C. Varying-density solid or hollow spheres can be manufactured at reported prices of $0.10 to $0.20 per pound. These spheres have a greater hardness than that of potassium nitrate. The technology has been used as a radiation delivery system for treating human liver cancers.6
Microtrace, Inc.
Microtrace, Inc., presented the MicrotaggantTM technology, a multilayered plastic particle. A code is created by altering the order of colors in the layers. The original technology (and associated patent) was developed by 3M in the 1970s, and has been in use in explosives (including black powder for blasting purposes) in Switzerland since 1980, as well as in other U.S. products for nonexplosive purposes. The Microtaggant TM was analyzed by the Office of Technology Assessment and Aerospace Corporation studies of 1980 (see Chapters 1 and 3). Enhancements by Dow and Eastman have reportedly increased the original code capacity 400 times.7
Marker Presentations
The following technologies were proposed to the committee to aid in the preblast detection of smokeless and black powder.
Chemical Delivery Systems, Inc.
Chemical Delivery Systems, Inc., proposed use of encapsulated frangible particles and masked detection materials as both a detection marker and identification taggant. The encapsulated samples are volatile and may be detected through odor, the specific molecule encapsulated, or by canine pheromones. Predicted cost for black and smokeless powder development was $500,000. No compatibility studies have been performed with black and smokeless powders. The technol-
ogy is used commercially in sleep aids, toothpaste, and antiperspirants, and by the U.S. Army for crowd control.8
Natura, Inc.
Natura, Inc., proposed using ''Luminate'' technology, a mixture of amino acids, metal oxides, and organic acids that are chemically attached to powders as a marking system. It is reportedly available as a water soluble or insoluble solid, liquid, or cream, and is stable to 250 °C. Detection would target luminescence or encapsulated odors. Incorporation costs are predicted to be on the order of pennies per pound. Approximately 20 companies are testing this technology, including pharmaceutical, paper and ink, and glue companies. The technology is reported to have an unlimited shelf life.9
Tracer Detection Technology Corporation
Tracer Detection Technology Corporation proposes the addition of vapor-emitting encapsulated perfluorocarbons to powders for detection and identification at the ppb level. Identification is made by use of gas chromatography equipped with an electron capture detector. There are seven compounds with a range of fingerprints. Perfluoromethyl and dimethyl cyclohexane may be used with no change in sensitivity. The microcapsule responds to external stimuli. Detection occurs in an electron capture detector. A microcantilever solid state sensor is used. The system is turnkey, with detection possible from a range of one yard. The technology has been tested on black powder with inconclusive results.10
Tim Z. Hossain (Gadolinium-157)
The use of gadolinium or a gadolinium-157 taggant was proposed for powder detection, using prompt gamma detection following excitation of the particles. This tag may be incorporated into microparticles. The proposed isotope has a large capture cross section, improving the signal-to-noise ratio, although the cost of marker addition is unresolved. The isotopes are stable, and the excitation probe as well as the prompt gamma emissions are reportedly sufficiently penetrating to detect materials concealed in high-density containers such as steel casings.11
Additional Concepts
In addition to the taggant presentations heard by the Committee on Smokeless and Black Powder, materials and presentations received by the NRC Committee on Marking, Rendering Inert, and Licensing of Explosives Materials were also reviewed. Presentations made to that committee are summarized below.
BioTraces, Inc.
BioTraces, Inc., principally makes instrumentation for detection and quantification of low levels of biomolecules. Company representatives proposed a taggant concept based on the use of multiphoton detection of appropriate biological and organic molecules.12
Cambridge Isotope Laboratories, Inc.
Cambridge Isotope Laboratories, Inc., synthesizes molecules (including some explosive compounds) tagged with stable, nonradioactive heavy isotopes. These isotopes are used mainly for biochemical and environmental trace analysis. Tagging of explosives through use of this approach was proposed.13
Centrus Plasma Technologies, Inc.
In written testimony,14 Centrus Plasma Technologies, Inc., proposed using small quantities of enriched, stable isotopes (either as bonded isotopes in a compound or as a fine powder added to an explosive)—detectable by mass spectrometry—to tag explosives. According to Centrus, the use of an admixture has the advantages of avoiding complete dispersal in a detonation of high-grade explosive and of being a clear indicator for the included tag. The small quantities of isotopes required and the fine powder admixtures are believed to minimize any adverse effects on the tagged explosive materials. Projected industry costs for this method were estimated by Centrus to be in the range of $40 million to $60 million per year.
MICOT Corporation
In written testimony,15 MICOT Corporation proposed using a taggant consisting of randomly shaped particles made from a chemically stable thermoplastic resin, encoded with a custom numerical code combination of 10 or more colored layers. MICOTTM particles are detectable with an ultraviolet lamp or magnet and come in sizes from 15 to 1,000 microns (or higher). The availability of particle sizes ranging from 5 to 8 microns with five colored layers is projected for 1998.
Micro Dot Security Systems, Inc.
In written testimony,16 Micro Dot Security Systems, Inc., proposed a self-contained, small, precision-cut polyester disk to mark or identify explosives. The Micro2219;Dot® can be coded with a variety of substrates, such as ultraviolet ink that fluoresces under black light for easy detection. It is imprinted with a 9- to 12-digit number that is a unique, one-of-a-kind sequence selected by the buyer.
Micro Tracers, Inc.
Micro Tracers, Inc., produces MicrotracersTM—colored, uniformly sized particles of iron grit, iron alloy, graphite, stainless steel, or silica gel that are analyzed through calorimetric techniques—that currently are used in animal and poultry feed and in building materials.17 They have been used in more than 300 million tons of animal and poultry feed since the 1960s at a reported cost of $0.10 per ton. The company has only limited experience in explosives mixing operations, although it believes that its general approach could be adaptable to explosives applications.
Science Applications International Corporation
In written testimony,18 Science Applications International Corporation proposed a detonator detection system based on multiphoton detection, a technique based on measurement of radioisotopic tracers whose decay is accompanied by
the emission of multiple high-energy photons. This detection system reportedly offers extreme sensitivity, rapid throughput, ease of use, and low operating costs.
Security Features, Inc.
In written testimony,19 Security Features, Inc., proposed the use of a Code-B MicroTracing System that uses highly uniform microbeads for identification. These microbeads can be of a certain precise size, a certain color or groups of colors, a specific fluorescence, and have paramagnetic qualities, and/or a combination of any of the above.
Special Technologies Laboratory
Based on a JASON report (JASON, 1994), Special Technologies Laboratory studied cobalt-60 as a radioisotope for (active) preblast detection. Experimental research has been initiated for screening baggage. The company's results indicate that the concept is valid and an effective method of detection but has not yet reached acceptable scan times.
SRI International
SRI International has proposed the use of upconverting phosphors—a class of manufactured, spherical particle materials that absorb radiation (such as from laser excitation) at a specific wavelength and then emit radiation, through luminescence, at a shorter wavelength.20 The concept has been proposed for both preblast and postblast detection of explosives and has been successfully tested by SRI on a small-scale explosive charge. A larger-scale test is planned.
Tri-Valley Research
Tri-Valley Research proposed using rare-earth (lanthanide) element mixtures to tag explosives for identification.21 Detection and analysis of these ingredients in explosives would be through x-ray fluorescence spectroscopy.
University of Strathclyde, Scotland
In written testimony,22 the University of Strathclyde, Scotland, proposed selective tagging of explosives using surface enhanced resonance raman scattering as a detection technique.
Urenco Nederland B.V., the Netherlands
In written testimony,23 Urenco Nederland B.V., the Netherlands, proposed using stable isotopes as a means of tagging explosives.