chapter 4 research and development

Chapter 4

Research and Development

INTRODUCTIONThis chapter provides an overview of current

research and development in technologies relevantto counterterrorism. The technologies are dividedinto

s●

●

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several fields:

detection of explosives and other weapons;detection of and protection against chemicaland biological agents;physical protection (e.g., alarms, barriers, ac-cess control);incident response; anddata dissemination.

Each of these functions is briefly discussed in thisintroduction and is detailed at greater length later inthe appropriate section of this chapter.

Explosives Detection

One of the most important types of detector is theexplosives detector, of great utility not only forairline security but also for the protection of fixedfacilities, such as embassies, nuclear plants, or othersensitive buildings. The last 2 years have witnessedsignificant progress in explosives detection, both incommercially available (or nearly available) prod-ucts and in R&D efforts. Another type of detector isthe weapon detector, usually thought of as a metaldetector (although this perception may change ifother, nonmetallic weapons become available in thefuture). This report will not address weapon detec-tion, which will be taken up in the final report of thisassessment.

Explosives detector designs are based on a numberof physical, chemical, and mechanical properties.One class of detectors is the “bulk’ detector, whichmeasures some of the physical or chemical proper-ties of the object to be examined. Some detectorsemploy ionizing radiation to accomplish this: exam-ples are detectors utilizing x rays, garoma rays,l orneutrons. Radiation is used to penetrate the objectand the detector measures the outgoing radiation,which contains information on the details of thecontents. This type of detector is limited in that,

although it can be used on baggage, it cannot beapplied to people because of the harmful effects ofionizing radiation at the intensities required by thewidely available techniques. Recent progress inimaging objects using ‘‘microdoses’ of x rays maychange

lis assessment. However, even if it could be

rigorous y shown that human exposure to microdoseequipment would have negligible health effects,there would still be a severe problem in overcomingpublic skepticism toward the use of this type ofequipment.

Another type of bulk detector uses nonionizingelectromagnetic (EM) radiation in the form of radiowaves. This includes high-resolution millimeter-wave radars that can search baggage or clothing forobjects, such as explosives, that would scatter themicrowaves. Also included are nuclear magneticresonance (NMR) and nuclear quadruple resonance(NQR) spectrometers. These devices expose thevolume to be searched to a pulsed radiofrequencyEM field and then “listen” for pulse echoescharacteristic of particular explosive compounds.Such detectors might be useful for consensualsearches of persons for concealed explosives if theEM fields employed are sufficiently weak.

The vapor detector, or “sniffer,” is a differentclass of detector. In this type of device, air samplesare taken and examined by rapid chemical analysistechniques for the presence of molecules of explo-sive compounds. This class of detectors may well beused to search people as well as baggage.

The original vapor-based explosives detector is,of course, the dog, which is very effective for somepurposes, but which has some serious “caninefactors” limitations. Dogs, while very sensitivedetectors, have limited attention spans, must beintegrated as a team with a particular trainer to bemost effective (thus generating high operatingcosts), and are often not consistent from day to day.They are still the best explosives detectors availablefor a wide variety of uses, such as a sweep of awell-defined area in the wake of a bomb threat.However, for many purposes, such as routine

IGaroma rays are, like x rays, elec~magnetic radiation characterized by very short wavelengths, but unlike x rays, they are generated by nuclear,rather than atomic interactions. Gamma- ray wavelengths are generally shorter (equivalently, of higher energy) than x-ray wavelengths, but there is anoverlap between the two types.

–31–

32 ● Technology Against Terrorism: The Federal Effort

baggage inspection on airlines, dogs are not appro-priate.

A host of factors, such as temperature, soak time(time between the placement of the bomb in thecontainer and the attempted detection), amount ofventilation, and operator expertise, dramaticallyaffect the performance of sniffers. Defining uniform,consistent, and realistic threat scenarios is critical tothe development of minimum performance stand-ards and objective evaluation criteria for vapordetectors.

Remote (or, in military jargon, “stand-off”)detection of vapors is quite a challenging task. Itcould be particularly useful for examining, at adistance, vehicles suspected of containing a largeamount of explosives. A laser beam, tuned to thecorrect wavelength, can be used to stimulate themolecules of a particular species of chemical vapor,for example, an explosive. These molecules thenmay absorb or emit light at well-defined wave-lengths. These phenomena could form the basis of aremote detection scheme. The characteristic wave-lengths of explosive chemical compounds wouldhave to be systematically measured to provide adatabase for the detector. This type of technology isbeing developed for the detection of chemicalwarfare agents (see app. D). However, a relativelylarge amount of vapor would be needed in order tomake explosives detection feasible. While the poten-tial theoretically exists for applying this technologyto the remote detection of explosives, small bombsin suitcases would not likely be easily detectableunless observed at very short range. However, thereare other cases in which remote detection by laserabsorption or excitation might be a possibility.

Another explosives detection mission, for differ-ent scenarios, is to look for buried explosives. Workis proceeding on the development of ground-penetrating radar that could find buried objects. Thiscapability would have useful applications for anumber of counterterrorist tasks, from finding buriedarms caches to detecting mines.

Chemical and Biological Agents

A terrorist attack using chemical or biological(CB) agents has not yet occurred, but might happenin the near future (see ch. 3). The fact that such

attacks have not yet taken place at a serious level (ina terrorist context) may explain the low prioritygiven to efforts to analyze and deal with sucheventualities. One exception to the general lowpriority given to this topic is the work undertaken bythe interagency Technical Support Working Group(TSWG).

Sometimes referred to as “poor man’s atombombs,’ chemical or biological munitions requirefar less technical sophistication than nuclear weap-ons. However, they, too, can qualify as weapons ofmass destruction. It should be noted that classicalchemical munitions and delivery technology wereused effectively in World War I, some 75 years ago,and were further developed by several nations by thetime of World War II. Some biological weaponstechnology is available, in principle, to any nationthat can brew beer. Chemical or biological agentscould be ideal for attacking targets such as embas-sies, perhaps through water or air supply systems.

Defense against terrorist CB attacks requires acombination of early detection and diagnosis, evacu-ation of endangered individuals, appropriate vac-cines for preventing spread of infectious agents,antibiotics and antidotes for treatment, means ofprotection, and decontamination. An important ele-ment of defense against CB attack would be theability to learn rapidly of the approach of suchagents, either through air or water. Laser-basedsystems show some promise for early detection.Other areas of interest lie in the development ofportable or miniaturized means of protection. Thereis some, but not much, activity in this area in theFederal sector. Some attempts to develop detectionand protective capabilities applicable to terrorismhave been made, notably by the TSWG.

Physical Protection

Physical protection includes the timely detectionof attacks, delays forced on attackers (includingarmor and hardening of targets), and the response toattacks.2 This section discusses alarms, barriers,access control to sensitive areas, blast protection,and hardening against projectiles. Detection andresponse are covered in other sections.

For example, physical protection for commercialairline security can include access control, applied

zSan&a Natio~ ~boratories, Designing the Physical Protection System, vol. II of Physical Protection of Nuclear Facilities ati Mate~”ak, meNinth Intermtional Training Course (Albuquerque, NM: Sandia National Laboratones, 1989).

-.

Chapter 4--Research and Development 33

both to passengers and site workers (this couldamount to as little as a few locked doors with asecurity force able to respond rapidly); metal detec-tors; and, possibly, explosives detectors. A fullyintegrated system would also include perimeterdesign; division of the airport into different securityareas, each with its own access control; closedcircuit TV; various types of alarms; and barriers. Inaddition, aircraft could be modified or retrofitted tomitigate the effects of inflight explosion. Finally,human factors technology and related psychologicalresearch data could be employed, along with themechanical components and defined system pro-cedures.

General fixed-site security includes incorporatingresistance to explosive blasts in architecture andengineering design, stand-off pedestrian barriers,and well-designed vehicle barriers. Further, as withairports, entrance procedures and access control forthe public and on-site workers can present obstaclesto a terrorist trying to introduce explosives into abuilding. In addition, external and internal barriersand protection devices are options for preventingovert assaults on a building.

Incident Response

Incident response covers those technologies use-ful in dealing with hostage-taking, an assault on afreed site, or other criminal undertakings that maybeinterrupted by appropriate response force actions.Incident response includes disruption of the attack;defending targets, where possible; aiding the in-jured; protecting or evacuating those endangered;rescuing hostages; and apprehending the attackers.Coordinating different response forces (which maybe from different agencies for a domestic incident orfrom different countries for an international case) isa key aspect of incident response.

There are many areas where technology or socialscience can help resolve the problem. For example,in some scenarios, pre-positioned sensors would behelpful in aiding rescue attempts. Human factorstechniques, particularly applied to hostage negotia-tions, are vital in dealing with ongoing terroristincidents. And software, ranging from checklists tosophisticated decision aides, would help. Incapaci-tating agents, riot control agents, or weapons thatdisable but do not permanently damage exposedindividuals, might be of use in some cases. Possible

techniques might involve chemical agents or exoticweapons using other physical principles.

The development of technology to aid variousincident response tasks will be discussed in greaterdetail in the final report of this assessment.

Data Dissemination

Institutional and, occasionally, legal barriers pre-vent the free flow of information among Federalagencies, and among Federal, State and local lawenforcement officials. This difficulty applies evenwhere terrorist threats and time-critical informationon terrorist activities are concerned. There are alsosome technical barriers to the rapid and securediffusion of such information. On another level, itappears that even up-to-date R&D information is notalways easily available to agencies that need it.Resolving this problem often requires modifying thebehavior of institutions, although some technicaldevelopments could be useful in mitigating the sit-uation.

This chapter deals with all of the above issues. Ingeneral, the information contained is not exhaustive,but provides an overview of the relevant technicalwork underway, along with an estimate of how nearto field deployment the more promising technolo-gies are. More details will be provided in thecomprehensive final report of this study.

DETECTING EXPLOSIVES

Introduction

The detection of small quantities of explosives isoften difficult but is by no means impossible.Advanced nuclear techniques and vapor detectors,as well as those based on other principles, have beenrefined to a point where simple detection is no longerthe key issue: the question is rather whether thestringent demands of many applications can be met.

For example, there are several difficulties relatedto explosives detection for protecting commercialaviation. First, for screening baggage, the rate andvolume of the load to be processed are daunting.U.S. airlines handle close to a billion pieces ofbaggage a year, and U.S. passenger traffic is over 40percent of the total world volume. Therefore, thedetection system must have a high throughput. TheFederal Aviation Administration (FAA) requires aminimum rate of 600 bags/hour (6 seconds/bag) foran explosives detection system, but airlines would


like a screening rate at twice that speed for a givenflight (a Boeing 747 typically ingests approximately700 to 800 pieces of checked luggage). The idealplacement of a detection system for checked luggagewould be at the check-in counter, where the passen-ger and bag are together, and where significantlymore than 6 to 12 seconds are needed anyway forticket processing.

Second, the threat is so diffuse. In 1989, only sixbaggage bombs were placed aboard aircraft (unlessthere were others that went undetected). It is notcurrently possible to err on the safe side by increas-ing detector sensitivity because too many falsealarms would result, and the delays involved inresolving them would snarl the whole air trafficsystem.

Finally, many believe that explosives detectionequipment must be automated (i.e., the decision toselect a suspicious bag for further investigation isperformed without human intervention), becauseinspecting many pieces is a repetitive and boringtask of which humans (and even dogs) quickly tire,becoming inefficient. Still, in the end, the effective-ness of even the most highly automated securitysystem will depend on the training and motivation ofhuman beings-those individuals who perform fur-ther investigations.

While airline security involves searches of hand-held bags or packages, checked baggage, mail, andmaterials carried by individuals, other applicationsfor explosives detection have different require-ments. Inspection of vehicles, as well as packages orcargo, is a prime concern for other secure locations,such as U.S. embassies abroad. Searches must berapid, cost effective, noninvasive, and nondestruc-tive. There are a variety of techniques that can meetat least some of these criteria for some types ofsearches and produce a usable signal when encoun-tering explosives.

Many techniques utilize ionizing radiation thatpenetrates the item to be searched. The radiationinteracts with the nuclei of the examined object toproduce absorption, secondary radiation, or both.These effects are then detected. Recent attention hasfocused on detection of nitrogen nuclei throughnuclear techniques: nitrogen is found in high propor-tion in most explosives. There are various advanced

versions of the common airport x-ray systems, aswell as some chemical sniffers, each of which hasspecific capabilities and shortcomings. There arealso techniques being investigated that utilize laserdetection, infrared radiation, ultrasound, micro-waves, and other methods that are not yet suffi-ciently developed to evaluate realistically.

This raises an important factor that differentiatesamong detection concepts: the relative state of theirdevelopment. Experimental measurements havebeen made for a large number of different concepts.Laboratory systems based on some of these conceptshave been used to demonstrate feasibility. A stillsmaller number have advanced to the prototypestage and have undergone actual airport experience.There are also some devices that are modificationsof commercially available hardware systems andhave new capabilities. Each of these categories mustbe viewed from a different vantage point withrespect to their utility for the detection problem.

In general, devices that are in the research stagewill be 5 to 10 years away from commercial avail-ability, especially if they are based on new, complextechnology. Worse yet, even this sluggish pace ispremised on the assumption that adequate levels offederal support are forthcoming. A 2- to 3-yearperiod may be expected for a successful researchphase; a feasibility demonstration may well take 2more years; a prototype program can easily last 2 to3 more years; and, finally, any test at a customer sitecan take another 2 years.3 Consequently, the statusof each development program must be looked atcarefully to assess where the concept stands in thedevelopment cycle. Hardware based on modifica-tions of previously utilized products, which issometimes possible with devices or systems used inother industries for other purposes, may shorten thiscycle. As a rule, the simpler the device, the shorterthe development time.

The Explosive Threat

There are literally hundreds of different types ofexplosives, varying from black powder used in pipebombs (still a favorite of domestic bombers), todynamite sticks, and from blocks of TNT to plasticexplosives that can be molded into diverse forms,including thin sheets. A dozen or so of the mostnotable explosives, including most of those used by

3For example, the current thermal neutron analysis (TNA) technology is approximately 10 years old, with early research at Westinghouse Pr*t~gthe 1985-90 Scientific Applications International Corp. (SAIC) TNA program.

Chapter 4--Research and Development ● 35

terrorists, are described in table 4-1. Of particularnote are the explosives RDX and PETN which,together withmany plasticSEMTEX.

plastic and other fillers, composeexplosives such as Detasheet and

History

Efforts to detect explosive materials have beenongoing for many years. Before applications forairline security were considered important, otherapplications (e.g., military security, security atnuclear weapons and nuclear power plants, securityat the U.K. Houses of Parliament) stimulated interestin the development of explosives detection tech-niques. The use of dogs to sniff explosives has beencommon for over a decade, but there has been asimultaneous desire in the law enforcement commu-nity to find technical means of doing what dogs cando, doing it better, and doing it more consistentlywithout the difficulties arising from canine factors,such as boredom, distraction, chemical maskers,mood, etc. Dogs as sniffers will be discussed furtherin the final report.

In general, detection techniques can be dividedinto two main categories: vapor detectors (relying onaccurate identification of trace airborne samples ofexplosives) and bulk detectors (relying on an inter-action between some kind of penetrating radiationand the hidden explosive). A list of various types ofexplosives detection strategies is presented in table4-2 and a more detailed discussion is provided bothlater in this chapter and in appendixes A through C.A brief history of the development of these applica-tions is presented below.

The first noncanine explosives detector, designedto sense dynamite vapor, was developed in the early1970s by Analytical Instruments of the UnitedKingdom and its affiliate, Ion Track Instruments ofBurlington, MA. In the two decades since then,progress has been great, and many competingtechniques have been developed.

Interest in applying explosive vapor detectors toprotecting commercial aviation increased after sev-eral terrorist incidents in the early 1980s, and FAAbegan sponsoring more research into sniffers in1982. In 1984, the FAA funded Thermedics, Inc. ofWoburn, MA to develop vapor detection technology

in a direction that could prove useful for airportsecurity. This work was aimed at producing awalk-through portal monitor. In 1986, the StateDepartment also funded work at Thermedics todevelop similar technology to detect explosives inpackages. Earlier sniffer technologies were able todetect only those explosives with higher vaporpressures (1 to 100 parts per million), such asdynamite and nitroglycerine. Some manufacturersnow claim that their products have been refined tothe point where it is possible to detect TNT underrealistic conditions. However, at least until recently,plastic explosives, which have far lower vaporpressures (as low as parts per trillion), were beyonddetection by vapor means under conditions thatwould prevail in the field (i.e., at security portals orin airports). This situation has changed.

Researchers realized that detection of low vaporpressure explosives by sniffing techniques would beextremely difficult. Therefore, the FAA also fundedefforts in researching nuclear techniques of detec-tion, beginning with Westinghouse in the late 1970sand then, in 1985, also with a contract to ScienceApplications International Corp. (SAIC). This latterwork led to the development of the Thermal NeutronAnalysis (TNA) device that is currently the subjectof much interest and controversy. The principalcontract with SAIC on TNA was concluded in 1987and 1988 with a series of ‘acceptance’ tests at theSan Francisco and Los Angeles airports; SAIC wasthen awarded a contract to build five (later increasedto six) TNA machines for installation and testing atvarious airports.

The TNA device is intended only for inspection ofchecked baggage, since it involves irradiating a testobject with an intense “bath” of neutrons. Inprinciple, it could also be applied to carry-onbaggage, but, so far, cost and size problems, alreadya serious difficulty for the checked baggage applica-tion, have been cited as arguments against utilizingTNA for inspecting hand-carried baggage. In at leastone foreign country, however, the feasibility ofusing smaller, less accurate, but cheaper TNAdevices for this purpose is being explored.4

The problem of developing useful explosivesdetectors for commercial aviation security has in-creased in urgency and political visibility in the

4SiII@ c~+n bags USually have less mass than checked baggage, it should be easier for a bulk detector, such as TNA, to see a small explOSive ina carry-on item amidst the background generated by the rest of the luggage.


Table 4-l—Some Common Explosivesa

TRADE OF POPULAR CHEMICAL NAME, FORMULA, COMMENTSNAME(S) AND STRUCTURE

AN, Ammo-Nite Ammonium nitrate

(NHJ (N03)-

Black powder

Composition B

Dynamite

EGDN

HMX,Octogen

Nitrocellulose,gun cottonb

Ethylene glycol

H2C– ONO2

H2C– ON02

dinitrate

Cyclotetra-methylene tetranitramine;1,3,5,7-Tetranit ro-1 ,3,5,7-tetrazacyclooctane

N 02

IN — C H2

/ \CHZ N— NOZ

IOZN — N CHP

\C H2— N

/

N 02

0 2N 0 O N 02

I I

iH C[— CH —.

\ 7H 0

CH o

ICHZ — ONOZ

Also commonly used as a fertilizer. Frequentlymixed with fuel oil to make explosive calledANFO.

Mixture of potassium or sodium nitrate, sulfur,and charcoal. Explosive most commonly usedin terrorist bombs in the United States.

60:40:1 mixture of RDX:TNT:wax

Compositions have varied over the years. Theexplosive components of modern dynamites areprincipally EGDN and NG absorbed ontocombustible pulp (e.g., wood meal, starch, ryef I our),

One of the main components of dynamite.Quite volatile, making detection by “sniffers”relatively easy.

A military plastic explosive.

Main component of smokeless powder.

n


N GNitroglycerine

PETN

Picric Acid

RDX,Research Division X,Formula X, CycloniteHexogen

SEMTEX

Table 4-1--Some Common Explosivesa--Continued

Glycerol trinitrate

H#-0N02

H! CONOZ

HZC– ON02

Pentaerythritol tetranitrate

0 2 N O C H2 — C- CHZON02

Trinitrophenol

OH

0 2N

o

\N02

/

N02

A plastic explosive available in bulk form or,with modifications, in sheet form under tradename“Detasheet.”Unusually low nitrogen density for a plasticexplosive: 18 percent by weight (compare with RDX).

Cyclotrimethylenetrinitramine; Primary ingredient of military plastic explosives1,3,5-Trinitro-l ,3,5-triazacyclohexane known as C-3 and C-4. 38 percent nitrogen by weight.

N02

I

/ N \C H2 CHZ

I Io2N”N\ /N~N02

CHZ

A Czechoslovakian-made explosive composed ofa mixture of varying proportions of RDX andPETN along with binder and plasticizer.


Tetryl, Tetralite

TNT

Table 4-l-Some Common Explosivesa--Continued

2,4,6, N-Tetranitro-N-methylanaline; Most common military booster.2,4,6-TrinitrophenyI-methyl nitramine

CH3 N02\#

02N&‘ N02

yN02

Trinitrotoluene A castable explosive.

CH3

02N

N02

NOTES:

wake of the Lockerbie crash, in December 1988.There had been previous bombings of aircraft, butmost attacks on U.S. airliners, although causingsome fatalities, had not brought down an aircraft.There had been several bombings that had destroyednon-U.S. commercial aircraft, the best known beingthe 1985 bombing on an Air India flight fromMontreal to London, in which 329 were killed.However, none of these had the impact on theAmerican public and Congress that the Lockerbiecrash did. Table 4-3 shows major commercialaircraft bombings since 1980.

Following Lockerbie severe pressure was broughton the U.S. Government to take immediate action toprevent repetitions of this tragedy. The FAA, byvirtue of its responsibilities and mission, bore thebrunt of criticism and pressure for action. Inaddition, the media, some elected officials, andvarious private groups, such as the Victims of PanAm 103, expressed the opinion that information

constituting a sufficiently specific prior warning hadbeen made available to some personnel in govern-ment agencies, while being concealed from thetraveling public. This resulted in much publiccriticism of both the FAA and the Department ofState.

Methods of Explosives Detection

All detection techniques depend on sensing prop-erties that are shared by explosive compounds andare relatively unique to them. Fortunately, there areseveral physical, nuclear, and chemical characteris-tics of common explosives that are helpful to thisend. Unfortunately, these compounds also shareproperties that make their detection difficult. Thechallenge to the designers of detection equipment isto create a system that can make use of the helpfulproperties and compensate for those that causedifficulties.


Table 4-2—Explosives Detection Technologies

Bulk detectors:Using ionizing radiation

Nuclear—Thermal Neutron Analysis—Fast Neutron Analysis—Nuclear Resonance Absorption of Gamma Rays—Associated Particle Production—Pulsed Fast Neutron Analysis—Pulsed Fast Neutron Backscatter-Nitrogen-1 3 Production with Positron Emission

TomographyX-ray

—Transmission-Backscatter—Dual- or Multi-Energy-Computerized Tomography

Using non-ionizing radiationNuclear Magnetic ResonanceElectron Spin ResonanceNuclear Quadrupole Resonance

Vapor or residue detectors:DogsGas Chromatography (GC)/ChemiluminescenceGC/Electron CaptureIon Mobility SpectrometryMass Spectrometry (two-stage)BioluminescenceSOURCE: Office of Technology Assessment, 1991.

The characteristics generally common to explo-sive

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●

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●

compounds are:

high nitrogen content and nitrogen density;the frequent presence of nitrogen as a nitro(-NO2) group;

high oxygen content, low carbon and hydrogencontent;relatively high density (about 1.5 times thedensity of water);extremely low vapor pressure;5

high polarity (also called electronegativity);6

low thermal stability;7

frangibility; 8 andadsorptivity.

Some nonexplosive materials have similar densi-ties or percentage nitrogen content, but only a very

small subset of materials has the high nitrogendensity of explosives. Almost no nonexplosivematerials have both the high nitrogen and oxygendensities that characterize most explosives.9 Asystem that could reliably measure the nitrogendensity distribution in a bag with good spatialresolution (probably one or two centimeters in eachdimension or better), should be able to detect mostexplosives with few false alarms. One that couldmeasure the distribution of nitrogen, oxygen, andcarbon within a bag should provide detection withalmost no false alarms.

Figures 4-1 through 4-4 illustrate this. Densityalone, which is what the simple x-ray scannermeasures, does not distinguish explosives fromplastics and other common materials (see figure4-l). Because certain fabrics contain a large weightfraction of nitrogen, the fraction of a bag’s contentsthat is nitrogen is also not a good indicator ofexplosives (see figure 4-2). However, figure 4-3shows that if the nitrogen density distribution can bemeasured locally within a bag, then only a very fewmaterials will mimic explosives. Unfortunately,among these materials are melamine, leather, andsolid nylon, none of which is particularly rare. Thesesubstances can cause false alarms if only nitrogendensity is measured. Figure 4-4 shows how explo-sives could be identified uniquely by adding anoxygen measurement. Explosive detectors usingnuclear techniques all utilize the above hierarchy ofphenomena.

Nuclear Methods of Explosives Detection

One family of explosives detection devices de-pends on ionizing radiation, such as neutrons orhigh-energy photons (gamma or x rays), to penetratethe object to be inspected. The interaction of thesepenetrating types of radiation with the elements inthe luggage produces signatures that can identify anexplosive: the degree of uniqueness depends on theparticular technique. The level of specificity of the

5~ ~ lmge ~omt of liq~d or ~~lid is pl~~~ ~ a ~lose.d con~er, the ~t~ will evapo~te UII~ WI ~lditium (dSo kIIOWll aS SahKdiOIl) hestablished. Thereafter, the rate at which molecules escape into the gas phase will be equal to the rate at which molecules in the gas phase return to thecondensed phase. The pressure generated by the gas phase molecules under these conditions is characteristic of the material and varies only withtemperature. The more reluctant a substance is to evaporate, the lower tbe vapor pressure.

6Even ~ou~ a molec~e my ~, ovm~, elec~c~y neu~~, atom or ~oups of atoms wi~ tie molecule may be electidly polti~d ~d havethe power to attract electrons. This is called electronegativity. The -NOZ groups typic~ of modem explosives possess ~s ProW~.

7This mea tit tie molecules easily breakup when their temperature is raised.8Fr@bili~ is tie tendency of a mol~tie to break apart when it SldCeS Or iS hit by ano~er obj=t.

%ere area few non-nitrogen-based explosives, such as perchlorates. These, however, are relatively unstable and run the danger of exploding whenthe terrorist would rather they did not. To date, these have not been widely used in attacks on aircraft although there is the possibility that if authoritieswere able to detect the nitrogen-based compounds, terrorists might turn to some of them.


Table 4-3--Airline Crashes Caused by Terrorist Bombs, 1982-89

Date Airline/aircraft type Route Deaths

September 1983 Gulf Air/737 Karachi to Abu Dhabi 112June 1985 Air lndia/747 Montreal to London 329November 1987 Korean Airlines/707 Baghdad to Seoul 115March 1988 BOP Air (South Africa)/ Phalaborwa to Johannesburg, South

Bandeirante Africa 17December 1988 Pan Am/747 London to New York 270September 1989 UTA/DC-10 Ndjamena, Chad to Paris 171November 1989 Avianca/727 Bogota to Cali 101

SOURCE: Federal Aviation Adminietration, The Washington Post Counter-Terrorism and Sewity Intelligence, Reportof the President’s Commission on Aidine SeoMtyand Twrotism, 1990.

identification is an inherent limitation on the useful-ness of the concept. Other limits are the level ofengineering development and the projected cost.The net utility of each method depends on itsstatistical probability of detecting hidden explosivesof all sorts and on its potential for false alarms,which must be kept at a very low level (preferablyless than 5 percent) to avoid disruption of normaloperations.

TNA is unquestionably the most advanced of thecurrent generation of Explosives Detection Systems(EDS), and, by virtue of the experience being gainedat various airports, will also be the most tested.Nevertheless, the current SAIC TNA system, theonly operational one, is, at best, a marginal EDS. Itmeasures the presence of nitrogen by means of theinteraction of thermalized neutrons (from a radioac-tive californium source) with the nitrogen nuclei.This interaction produces high-energy gamma radia-tion of a characteristic energy that is then detected.

The numbers for detection probability and false-alarm rate vary, depending on several alternativedetails of the integrated detection system. Adding anx-ray device to TNA (utilizing and correlatinginformation from both systems) and retrying suspectbags both change performance. Performance alsovaries with the type of baggage (defined by season,destination, and originating airport) being inspected.Its performance for detecting lesser quantities ofexplosives is poorer: the probability of detection islower and the false-alarm rate higher. The FAAarranged for an outside group of experts to retest theSAIC TNA at more sensitive detection limits inearly May 1990. See appendix A for a discussion ofthis test.

Checked baggage normally contains a wide rangeof nitrogen. The problem is to identify as suspiciousonly those bags with an excess of nitrogen-in anamount corresponding to the nitrogen content of a

small plastic explosive-in the presence of thisvarying background. Attempting to detect smalleramounts of excess nitrogen would cause a largefalse-alarm rate. One possibility to resolve thisproblem would be to identify the location within abag of any nitrogen excess. The current TNA has alimited spatial resolution, capable of giving only avague idea of wherein a bag a suspiciously elevatednitrogen content is found, so its capacity for falsealarm reduction is similarly limited. If TNA were tobe applied to carry-on baggage, which usually hasless mass than checked baggage, the backgroundwould be less and presumably the false-alarm ratefor a given detection probability would be lower.

One of the unique features of TNA is that it is anautomated system, i.e., one with no operator in thego/no go decision process. The system has someoperational problems in that it does require signifi-cant shielding (built into the system) it is large andheavy, and is very expensive (about $1 millioneach). A more detailed discussion of the TNAconcept is given in appendix A.

Beyond TNA, there are a number of nuclear-basedsystems that are in the laboratory demonstrationstage. Several hold the promise of improving onsome of TNA’s shortcomings. One avenue ofapproach is to use faster neutrons, which allows thedetection of elements other than nitrogen, such asoxygen and carbon, thus potentially reducing false-alarm rates considerably. The measurement of allthree elements simultaneously would produce aneffective and specific explosives discriminationprocess, as discussed above. Both steady and pulsedbeam versions of Fast Neutron Analysis (FNA) areunder investigation. Some concepts would greatlyimprove spatial resolution, as well as yield informa-tion on several elemental constituents of explosives.More energetic neutron systems require more com-plex sources, such as accelerators, which are not

Chapter 4--Research and Development . 41

c(a

,,,

,

I,,,,

,,,,I,

a(ja>‘ns

I

-r

c-0<z

,,,I

,,I

,,,,,$

I —

—

N

o

Figure 4-2—Nitrogen Percentage of Various Materials

-1 Common plast ics

+----------------------------------------------------- -------------------------------------------- ----

/ / / ~ / / / / / / / / / / H / / / / / / / / / / / / ~ / / / / / / / A///////////////////////////4

/////////////////////////&I I

Clothing

---- ----- ----- . . . . . ----- -

Explosives

---- ----- ----

0 1 0 20 3 0 40 50 60Percent ni trogen, by weight

SOURCE: L. Grodzins, 1990.

Figure 4-3—Nitrogen Density of Various Materials

k/// /A

A few common mater iais

._. ..-_ -__-------- .. ----- . -------------- —-------

Common plasticsF~//////////zZZ3

////////////////////////////////////////////~//////H~/////~////////////////////-

/ / / / / / / / / / / 2------------------------------------------------------------------------

i ------------------------------------------------------------------------

-----------------------------------------

Clot h i ng,Densi ty of 0 .2 g/cm 3

/ / / / / / / / /2z2z%z////// / / / / / / / / / / / / / / / / / / / / / / / / / / /A//// / / / / /%/22//// / /2

Ex p Ios i ves

/////2332//////==///////H/////////////#////////////////////HY///Y/~/////////4/ / / / / / / / / i d / 3 z / / / / / z//////////~/////////////m

I

o 0 . 2 0 . 4 0 . 6 0 . 8 1

Densi ty of n i t rogen, in glcma

SOURCE: L. Grodzins, 1990.


Figure 4-4-Correlation Between Oxygen and Nitrogen Densities in Explosives and Other Materials

c’ala*xo

1.5 “

1.4

1.3

1.2

‘1.1

1.0

0.9

0.8

0.7

0.6

0.5

0.4

0.3

0.2

0.1

0.0

Sand

EXPLOSIVES

❑ PETN

❑ NitroglycerineAmmonium nitrate

❑

Water ❑ o ❑

Sugar❑

Dynamite ❑TNT

❑❑

I ❑ Black powder

HMX❑

C-3 o ❑ C-4

❑ Polyurethane

Cocaine

D Nylon, Solid

Silk❑

❑ Melamine~ I I I I I 1 I

0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8

Density of the nitrogen, g/cm3

SOURCE: L. Grodzins, 1990,

available commercially and require development.Such devices will probably be larger, more expen-sive, and require more shielding than TNA. Appen-dix A discusses the FNA systems.

A somewhat different approach, based on thephenomenon of resonance absorption of garoma raysin nitrogen, has been explored and demonstrated inthe laboratory and is now at the prototype develop-ment stage. In this approach, gamma rays (createdthrough the absorption of a proton beam by a carbontarget) are utilized to produce a gamma-ray absorp-tion image that is specific to nitrogen content. The

process has fairly good spatial resolution and issensitive to small amounts of nitrogen, both advan-tages over the current TNA. However, OTA esti-mates that this concept is at least 3 years away froma prototype demonstration (if fully funded) of thesort currently being done for TNA. This approach isalso described in more detail in appendix A.

There are several other nuclear-based explosivesdetection schemes, some of which are discussed inappendix A; a few other similar ones are not specifi-cally mentioned. These concepts are all in thelaboratory research stage.

Chapter 4--Research and Development . 45

Accelerator Technology

All nuclear techniques have a common problem inthat they require means of generating neutrons orother energetic particles in order to produce thepenetrating radiation with which they probe objectsto be examined. All of the proposed techniques, withthe exception of the current SAIC TNA machine thatemploys a radioactive californium source,10 requiresome form of accelerator. Some general discussionof accelerator technology is thus useful to emphasizetheir common advantages and problems.

Although accelerator technology is a well-advanced science, work in accelerators has beenprimarily in support of laboratory experiments. Bothsmall and very large machines are operated through-out the world, but generally by highly trainedscientists, usually physicists or electrical engineers.An exception to this generality is in the area ofsemiconductor processing and medicine, whereaccelerators have been employed in industrial proc-esses and where some success has been achieved inreducing their complexity and their costs of opera-tion and maintenance. Fortunately, the acceleratorsneeded for explosives detection are similar to thoseexploited for these applications.

Accelerators have common characteristics thatcomplicate their use in industrial applications. First,they are complex, highly sophisticated machines,involving very high voltages (100,000 to 1,000,000volts). Second, they are relatively large and take upa significant volume. Third, many produce neutrons,which must be stopped by shielding; further, mostmaterials used to attenuate or isolate these neutronsare also activated and require their own shielding.The higher the energy and intensities of the pro-duced neutrons, the greater the activation andshielding problem.

Another problem is that all accelerators requiresome source of ions or electrons, and these sourceswear out. In general, the high current requirementand prolonged continuous operation of explosivesdetector applications tax the state of the art of thesesources. Finally, all accelerator concepts that havebeen suggested for explosives detection will be

considerably more expensive than the isotopicsources; accelerators would usually cost $100,000and more.

Several different types of accelerators have beenbuilt or tested with an eye to eventual use forexplosives detection. Early SAIC experiments forthe FAA used a sealed source produced for industrialapplications. This source was based on the D-Dreaction, i.e., it accelerated a heavy hydrogenisotope, deuterium, to collide with a deuteriumtarget. This source had a very poor lifetime (of theorder of 100 hours). Later, under FAA sponsorship,an electrostatic accelerator was built (by NationalElectrostatic Corp.) and used at SAIC to replace theCf-252 source in the TNA. It was judged too big,complex, and expensive ($200,000) by comparisonwith the isotopic source, but it has been successfullydemonstrated as an alternative TNA source.ll

The FAA and TSWG have also sponsored thedevelopment of another type of accelerator, the radiofrequency quadruple (RFQ), which is currentlyunder test by ACCSYS Technology, Inc. Thissystem is a development based on Los AlamosNational Laboratory technology (that had beenadvanced through funding under the Strategic De-fense Initiative). The system was transferred to asmall private company, which is continuing thisresearch via a Small Business Innovative Researchgrant. Like all accelerators, the RFQ has theadvantage of being switchable (i.e., it can be turnedon and off at will). However, it is a pulsed system,which creates some electronic problems for TNA. Itis unlikely that the RFQ accelerator can competewith the isotope source in cost, size, or simplicity.

Nuclear systems other than TNA require moreenergetic particles. Fast neutron analysis requiresenergetic neutrons. These are, in practice, usually of14 MeV energy, generated from D-T reactions (inthis case the deuterium target is replaced by a tritiumone--tritium is a radioactive isotope of hydrogen).Although so-called electronic tubes to produce thesereactions have been available for scientific and someindustrial applications (e.g., for well-logging in theoil industry) for years, their development for explo-sives detection is still in prototype testing stages

l~e c~iforfim.252 somce @ in he SAIC TNA WaS a judicio~ choice horn several points of view: it is used extensively in the medid fieldand in other industrial applications; it is well developed and industrially qualifix highly tested models are available; it is ve~ small compared to mostaccelerators; its shielding requirements are well know and it is relatively inexpensive ($10,000 to $20,000). However, its radioactivity introduces itsown set of problems and concerns, which have been discussed.

1lw. WW, FM Techni~ Center, personal comrnticatio~ 1990.


(e.g., at SODERN in France). The operating charac-teristics of such devices have not yet been assessed.Such systems are being developed to support boththe continuous and pulsed version of fast neutronanalysis.

Other techniques, such as nuclear resonance absorp-tion (NRA) of garoma rays, have special acceleratorrequirements. In the NRA case, a relatively lowenergy (1.75 MeV) proton beam is required. Thiseases the shielding requirements because few nucleiwill be rendered radioactive by such a low energyproton beam. However, the systems requirements,particularly in terms of beam current (the number ofprotons produced per second), do strain the state ofthe art of this type of accelerator. Electrostaticaccelerators, similar to laboratory Van de Graaffhigh-voltage machines, can support early NRAexperiments by extending the present current-carrying performance of the systems and sources bya factor of 2 to 5 (to about 0.5 milliamperes (mA)).It is believed that a final system would requirecurrents beyond this capability (2 to 5 mA). Otheraccelerator candidates are available, based on con-cepts that have been used in industrial ion implanta-tion machines, but the development and industriali-zation of such accelerators has been a time-consuming, multimillion dollar program.

Still another class of accelerator under considera-tion is the electron accelerator needed for theNitrogen-13 production concept. In this case, aradiofrequency (RF) linear accelerator (LINAC) isthe prime candidate. Production of a 13.15 MeV RFLINAC of sufficient current is not a great challengeto the technology. The issue is one of size, shielding,industrialization, and cost. From current experience,it is not likely that such a system will be small, easyto shield with minimal structure, or cheap.

X-Ray Technologies

Existing commercial x-ray scanners are capableof giving high resolution images of the interior ofobjects. They have been used for many years tocheck hand-carried baggage and, more recently,checked luggage. During the last 5 years, majorstrides have been made in x-ray technology. Newmodels are far more capable than those in generaluse at airports today. Some of these new systems cannow differentiate between materials composed oflight or heavy elements, and some have very good

resolution with three-dimensional imaging capabil-ity. However, so far, no x-ray system has beenautomated to make autonomous decisions (in orderto satisfy FAA requirements for acceptable explo-sives detection systems), although several vendorsare working on such modifications. In general, x-raysystems are under development by large- or mid-sized established commercial manufacturers andthese systems are modifications of their currentproducts. New x-ray systems can therefore bebrought to the market much more rapidly than mostof the other devices discussed earlier in this section.

The most important new developments in x-raysystems are in the areas of dual- or multi-energysystems, backscattered x rays, and computerizedx-ray tomography (CT). Dual- or multi-energysystems are able to distinguish between low and highZ (or atomic number-the number of protons in agiven nucleus) elements to a degree and can presentthe viewer with two or more images that emphasizethe different materials (e.g., by color differentia-tion). Commercial devices with this capability areproduced by EG&G Astrophysics and Siemens-Heimann.

A somewhat different approaches the Z-Technology(a trademark), or back-scatter x-ray system devel-oped by American Science& Engineering (AS&E).In this case, the low Z image is created by a differentprocess, i.e., detection of Compton backscatterradiation. Commercial Z-Scan systems exist and themanufacturer is now attempting to develop anautomated pattern recognition approach that willmeet the FAA's EDS requirements. Discriminationbetween high and low Z, although useful, does notspecifically and uniquely identify explosives.

Another x-ray system under development is basedon the application of medical computerized to-mography (CT) technology to explosives detection.One company, Imatron, is close to having a proto-type unit on the market able to produce three-dimensional images of suspicious items within asuitcase using CT processing. Through analysis ofthe data, they claim to be able to determine densityto a high degree of precision. This provides a strongclue for detecting explosives. The demanding com-puting requirements of this system limit the speed atwhich it can operate, thus affecting throughput. Allthe above x-ray systems are discussed in appendix B.


Explosives Detection by Magnetic Resonance andNuclear Quadruple Resonance

Bulk explosives may also be detected by magneticresonance methods-both nuclear magnetic reso-nance (NMR) and electron spin resonance (ESR).The general technique is to place a sample in auniform magnetic field and to expose it to a radio-frequency (RF) electromagnetic field. Then, theprocedure requires varying the frequency (or themagnetic field strength) and noting the frequencies(or magnetic field strengths) at which the sampleabsorbs or emits RF energy.

The nuclear quadruple resonance (NQR) methodemploys a similar procedure but does not require auniform magnetic field. It has been used to detectboth non-nitrogenous and nitrogenous explosives inthe laboratory.

The feasibility of detecting bulk explosives byNMR, ESR, and NQR in operational contexts hasbeen studied for several years in the United Statesand the United Kingdom. For detecting sheet explo-sives containing nitrogen or chlorine, NQR appearsespecially promising. The final report of this assess-ment will discuss in greater detail the detection ofbulk explosives by these three techniques.

Vapor Detection by Chemical Means

Man-made vapor detectors must perform threegeneral steps. First, a sufficiently large sample ofmolecules must be collected. Second, interferingmaterials and impurities must be removed, thesample must be concentrated, or both. Finally, theremaining material must be tested in a way that willrespond uniquely to the presence of explosivecompounds.

The extremely low vapor pressure of many of thematerials listed in table 4-1 makes the first step--collection of an adequately large sample of mol-ecules-a serious challenge (see figure 4-5). EGDNhas the highest vapor pressure among the commonexplosives and will be present in a saturated volumeof room temperature air at the relatively highconcentration of 1 part per 10,000. Chemically,EGDN is similar to the antifreeze commonly used inautomobiles, differing only in that it contains twonitro (-NO2) groups. Like its antifreeze cousin, bulkquantities of EGDN exposed to the air are rather

easily detected even by that relatively insensitivedetection device, the human nose.

A saturated vapor of DNT (dinitrotoluene, acommon contaminant in TNT--trinitrotoluene) ornitroglycerine (NG) will contain about one moleculeof target compound per million molecules of diluent.Ammonium nitrate (AN) and TNT itself will bepresent at a concentration of about 1 part in 100million (108). The plastic explosives RDX andPETN are even less volatile, being present in asaturated volume of air at standard temperature andpressure at a concentration of one part in one millionmillion (or trillion—1012). This concentration iscomparable to one shot glass of whiskey in LochNess, about 30 cents out of the national debt or1 second out of 32,000 years.12 HMX is, by a factorof about 60, even less volatile. These concentrationsrepresent saturation, a condition unlikely to beencountered in the field. Thus, in all likelihood,substantially less material than suggested here willbe available for capture.

In addition to the vapor pressure of the purecompound, several factors affect the concentrationof detectable vapor in the vicinity of an explosive. Ifan explosive device is contained within a more orless enclosed small. volume, after an extended time(on the order of hours or days) the concentration ofexplosive molecules within the enclosed space willbuild up towards equilibrium conditions. Air fromsuch a suitcase or drawer or other container wouldcontain near the maximum possible number ofmolecules. If the nearly saturated air could then bereleased and sampled, the probability of detectionwould be enhanced.

Another factor is the presence or absence ofrelatively higher vapor pressure contaminants,which are often introduced or created during themanufacturing process. While in many cases thesecontaminants have not even been identified, theynevertheless will cause some of the detectors toalarm. The concentration of these contamin ants inthe air surrounding a sample of explosive is afunction of their concentration on the surface of thepiece. Thus, they are most easily detected around afreshly broken piece. As they evaporate from thesurface, their concentration near the explosive’ssurface declines. Molecules of the contaminant will,over time, diffuse to the surface from within the bulk

l~o~e~ of Frank Conrad, Sandia National Laboratory.


Figure 4-5-Relative Volatilities of Some Common Explosives

c.-

1 in 1015

1 in 1014

1 in 1013

1 in 1012

1 in 1011

1 in 1010

1 in 109

1 in 108

1 in 107

1 in 108

1 in 105

1 in 104

1 in 103

1 in 102

1 in 101

o

HMX●

. ——— — — — —— — — —— — — —— —— — — — ————— —

1 ppt

RDX●

1 ppbTNT.— — ————— —— ——— — — —— — —

● —— —— — ——— - — — — —

N H4N 03

●

1 ppm

I I I

DNT●

N G●

EGDN●

I I I100 300200

Molecular weight of explosive

SOURCE: Sandia National Laboratories, 1990.


of the explosive but this is a relatively slow process.Therefore, while such contaminants can be a benefitto the detection process, their presence cannot berelied on.

Finally, the presence or absence of physicalcarriers will have a profound effect on the motilityof explosives molecules. Many researchers nowsuspect that most sniffers are not responding tomolecules of the explosive compound in the purevapor state, but rather to molecules attached to smallcarriers such as dust specks.

The relatively high electronegativity of theseexplosive compounds is a mixed blessing. It causesthe molecules to be “sticky,” rather in the way thatstatic electricity makes balloons cling to a wall. Thiselectronegativity is helpful for detection in that itmakes the explosive compounds rather uniqueamong organic molecules in their ability to attractand retain electrons, thereby forming negativelycharged species (anions). The formation of anions isused by several detection schemes in testing for thepresence of explosive in a sample. But this sameproperty also causes difficulties for detection be-cause the molecules bind to surfaces so strongly thatshaking them loose in order to sweep them into adetector is not easy. Further, this affinity of themolecules for surfaces further depletes their concen-tration in the air sample. These twin effects formboth the basis and the bane of many devices used toincrease the concentration and number of moleculesat the detector part of a sniffer.

The first stage of a sniffer will usually sample theincoming air by drawing it over a surface onto whichthe sticky explosive molecules attach themselves. Inthis manner, the molecules contained in a largevolume of air maybe captured. Later, on heating thesurface, the molecules are driven off. By performingthis heating step in a stream of gas of much smallervolume than the originally sampled air stream, theconcentration of the explosive molecules is en-hanced. Unfortunately, not all (or even most) of themolecules are actually shaken loose from the adsorp-tive surface by the heating step. Thus, while theresulting stream contains a greater concentration ofexplosive molecules, there is, nevertheless, a de-crease in the absolute number of molecules availablefor detection.

The thermal instability of these compounds is aproblem because the same aggressive efforts @eat-ing) sometimes needed to separate a sample of theexplosive from a substrate, so that it may bechanneled to a detector, can also cause the com-pound to degrade into smaller fragments that gounrecognized by the detection equipment.

On the other hand, some detection techniquesactually depend on a related property, the frangibil-ity (fragmentation) of these compounds. On impactwith the proper targets (70 eV electrons or atoms ofan inert gas, for example), these molecules willfragment. Under the right conditions, the kind andnumber of fragments into which the explosivemolecules break down is predictable. In this manner,the presence of an explosive compound in the testedvapor may be confirmed. The two-stage mass-spectroscopy device described in appendix C takesadvantage of this property.

The capture of a sufficiently large number ofmolecules of the explosive compounds probablyconstitutes the most difficult step for the sniffers.The explosive compounds do not shed many mol-ecules into the air on account of their low volatility,and, consequently, successful vapor detectors mustbe sensitive to the presence of pico- or evenfemtogram quantities of material (10-12 and 10-15

gram respectively). The performance of vapor detec-tors can also be degraded by the presence ofinterfering materials and impurities, which can bothtrigger false alarms and lower the sensitivity of theequipment to real explosives. Finally, the effective-ness of the system is dependent on matching thedetection strategy to the properties of the specificexplosive compound present.

In the United States, until very recently, testsconducted on sniffers did not yield very favorableresults. In March 1988, the FBI examined theperformance of four commercially available explo-sives vapor detectors under realistic conditions.While most of the instruments could easily andreliably detect pure samples of the higher vaporpressure materials (EGDN and NG) under laboratoryconditions, results in real world scenarios, includingsearches of suitcases and cars, were disappointing.The authors concluded:

13’ ‘Explosive Detector Evaluation%’ FBI Laboratory, Forensic Science Research amd Training Center, FBI Academy, Mar. 21-24, 1988, p. 65.A limited distribution report. Registered copies for ofllcial use are available by writing on letterhead to the FBI Academy, Quant.ice, VA 22135.


[T]he challenge still remains to find a small hand-held detector able to reliably detect inorganic andplastic-based explosives in operational scenarios.13

In tests conducted by the FAA in 1989, another kindof sniffer, a chemiluminescent device (see app. C),also did not perform well. Results of this test havenot been published. On the other hand, severalforeign countries have found considerable promisein more advanced chemiluminescent units recentlytested in a number of applications, including somebaggage screening for airline security. In late 1990,the FAA ran tests on several vapor detection devices.The results of these tests have not yet been madepublic.

Vapor detection schemes do have certain advan-tages. They seem to be more amenable to automationbecause the typical output of the machine is a fairlysimple electronic signal that can be satisfactorilyinterpreted by a microprocessor. No complicatedpattern recognition is involved. Further, by gener-ally avoiding the use of large radioactive sources andtheir attendant public relations problems, shippingand exporting these machines is a simpler matter.For the same reason, unlike detectors using largeamounts of ionizing radiation, they can be used toscreen radiation-sensitive subjects, such as humans.Also, because they generally do not require anyshielding, they can be smaller and more portable andthereby more versatile than bulk detectors. Forexample, they are available as hand-held units thatcan be carried around a test object by a single person.They are much cheaper, usually by a factor of 10 andsometimes even by a factor of 50 or more, thannuclear-based devices. Finally, techniques are beingdeveloped to compensate for the low volatility of theexplosive compounds. For example, some expertshave had success using a swab to wipe down asuspected person or object, then testing the swab forresidues. These detectors are being used in a varietyof search scenarios.

A discussion of some of the different techniquesand devices under development for explosives vapordetection may be found in appendix C.

Taggants

Given the difficulties in detecting small butdeadly amounts of explosives, either by vapordetection or nuclear techniques, alternative possibil-ities need to be explored. A suggestion to this end,which has been discussed for years, is to place someagent in the explosive during manufacture thatwould make detection far easier. In the past, theprincipal goal of tagging explosives was for forensicpurposes, that is, to try to aid in discovering themanufacturing origin and procurement path of anexploded bomb by careful examination of theresidues of the explosive at the scene. Manypossibilities were suggested and analyzed in an OTAreport in 1980.14 Suggestions for incorporatingtaggants in explosives were strongly opposed bymanufacturers and by the National Rifle Associationfor several cited reasons: unacceptable added cost,complication to the manufacturing process, reducedperformance (particularly of ammunition), and lackof effectiveness for detection, since foreign or clandes-tine manufacturers would not use the taggants.

However, in response to recent terrorist attacks oncivil aviation, there has been a renewal of interna-tional interest in adding taggants to explosives. TheInternational Civil Aviation Organization (ICAO)has organized a technical group to study this matter,and research is centering on a small number ofpossible chemical additives. Of particular interest isthe fact that former Eastern bloc countries, includingCzechoslovakia, have expressed strong interest incooperating in this endeavor, doing so even prior tothe recent accession of President Havel and anoncommunist government. The cooperation ofCzechoslovakia would be particularly valuable be-cause it is the manufacturer of SEMTEX, a favoriteplastic explosive of Middle Eastern terrorists thatwas apparently used in the downing of Pan Am 103.Further, Czechoslovakia and the United Kingdomhave cooperated in a joint United Nations effort todevelop an international agreement on tagging. Thelikelihood of an international convention that man-dates the inclusion of a chemical taggant duringmanufacture of all plastic and sheet explosivesappears far more promising than it did some yearsago.

13~~Explosive Detector EvdtMtioQ’ FBI Laboratory, Forensic Science Research amd Training Center, FBI Academy, Mar. 21-24, 1988, p. 65.A limited distribution report. Registered copies for official use are available by writing on letterhead to the FBI Academy, Quantico, VA 22135.

14u.s. Conmss, Ofim of T~~olo~ Assessment T’ggant~ in Explosives, OTA.ISC-116 (Sprin@eld, VA: Natior@ Technieal r.UfOImtitiOnService, 1980).


The principle of a chemical taggant is to introduceinto all manufactured explosives a particular type ofmolecule that is easily detectable by vapor detectors.There are several requirements for such a taggant. Itmust be cheap and usable in small amounts, notunduly complicate the manufacturing process, andbe easily available, nontoxic, safe, and easilydetectable. A multinational working group is inves-tigating several compounds. All are explosivesthemselves with relatively high vapor pressures,which would aid detection with sniffers. Othercompounds are also being investigated. The feelingamong the participating officials is that the interna-tional group may agree on a single compound in thenear future. Efforts would then be made to arrive atan international manufacturing convention.

The only United States participation in taggingresearch is being carried out under a small contractwith the U.S. Army Armament Development Com-mand at Picatinny Arsenal in New Jersey (about$35,000 in fiscal year 1989 and a like amount infiscal year 1990) with funding provided by theTSWG.

Another approach, pursued only on a theoreticallevel thus far, has been suggested. The conceptconsiders the possibility of doping all explosivesduring manufacture with a minute amount of aradioactive isotope. Taggant concentrations as lowas 10-12 grams per kilogram of explosive shouldallow one to detect a signal above ambient, naturalradioactive background. Passengers and baggagewould be screened by detectors that look for thecharacteristic radioactive emission at entry-ways inairports, similarly to current practice with x rays forcarry-on baggage and with metal detectors forpassengers. Unlike the chemical additives case,detection would not rely on the presence of vapor.Attempts by a terrorist to shield the gamma rayswould be detected because of the large amount ofheavy metal required.

The radioactive content of a bomb composed ofthe doped explosive would be less than that in ahuman body. Consequently, health hazards wouldbe essentially zero. Many more orders of magnitudeof radioactive exposure would be received by anairline crew and passengers from exposure to thenatural background during a flight than by being

surrounded for hours by explosives doped with thistaggant.

One problem with this latter approach is thepotential public opposition to anything radioactive,even if the quantities involved were so small thatexposure to a passenger carrying the explosive onhis body would be much lower than he wouldreceive, for example, from sitting next to anotherperson (industrial exposures would also be insignifi-cant). Measurements in support of this concept haveyet to be made. If background levels turn out to behigher than anticipated in an operational airportsituation, more of the taggant might be needed(although the concentrations would still be far lessthan should occasion any health concerns).

However, there are two serious problems withtagging of any kind. The first is the large amountof explosives already in the hands of terroristsand their state sponsors. 15 lt would take years,perhaps 5 to 10 or more, before this material wouldbecome unreliable. Nevertheless, one can argue thatone should start at some time to tag explosives,because eventually the material in the current worldinventory will run out.

But there is a more difficult objection, namelythat some terrorist groups now have the ability,possibly as individual groups or else throughcontacts with their state sponsors, to make theirown plastic high explosives. These illegitimatemanufacturers will, of course, not tag their explo-sives, and no international accord could guaranteethat they would. Therefore, tagging would onlyraise serious difficulties for terrorists who haveno access to illegitimate, nontagged sources and,even for them, probably not until some years inthe future.

DEFENSE AGAINST CHEMICALAND BIOLOGICAL WARFARE

(CBW) AGENTSAlthough few overt and no major events have yet

taken place, there is a consensus that a chemical orbiological (CB) terrorist threat exists. A briefdiscussion of the threat was given in chapter 3. Thelevel of technological sophistication required tomount a terrorist attack of this type is not particularly

Issee, for exanlple, The Washington ZJo~t, Mar. 23, 1990 forthereport by President Havel of Czechoslovakia% who announced tit tie previous W@ehad sold 1,000 tonnes of SEMTEX to Libya and further amounts to other terrorist-sponsoring states, such as North Kore~ Syria, IrarL and Iraq.

52 . Technology Against Terrorism: The Federal Effort

high. In fact, for some scenarios, it may be lowerthan was the case for some of the sophisticatedbombs that have been used against civilian aircraft.Further, the ability of Libya, Iraq, and Iran toproduce chemical weapons has been known fromopen sources for some time, and all of thesecountries have sponsored active terrorist groups thathave attacked civilian populations with the aim ofproducing many deaths.

However, in the absence of actual examples ofterrorist attacks employing chemical or biologicalagents, it is extremely difficult to substantiate oreven define the threat accurately. In lieu of concreteevidence, and armed with some intelligence data,planners have found it necessary to look to U.S.military programs (which are, however, designed forbattlefield applications) as a guide for devisingresponses to such events.

Research and development into the problem ofdetecting CB agents, either on the battlefield or in aterrorist situation, is not very advanced. Detection ofbiological agents and subsequent (or, frequently,concurrent) diagnosis of the agent causing thesymptoms is relatively undeveloped. As a point ofreference (that is, admittedly, 15 years old), in 1976,it took the full resources of the U.S. Government7 months to isolate the Legionnaires’ disease Le-gionella pneumophila bacterium when it was dis-covered.l6 17

The U.S. Army has primary responsibility fordetection of chemical and biological agents. It has amodest research program and a few field detectorsystems under current development. The Army alsomaintains related intelligence activities that continu-ally assess the chemical and biological threat,including the likelihood of their use by terrorists.

Biological agents are powerful; very small quanti-ties can produce serious and widespread injury.They may be divided into three classes: those thatinfect those immediately exposed, but do not easilycontaminate others who come into contact with thevictims; those that are highly contagious and maycause epidemics; and those that are not livingorganisms or viruses, but are chemicals produced byorganisms and only affect those exposed to them. Anexample of the first type is anthrax; the second type

may be exemplified by Yersinia pestis, the bacteriathat causes plague; the third type is comprised oftoxins, such as botulinum toxin.

Table 4-4 gives some typical detection goals setby the U.S. Army for several of the most commonchemical and biological agents envisioned as possi-ble threats. The quantities cited give an idea of theireffectiveness. United Nations experts have esti-mated that a person drinkin g 100 milliliters (lessthan a half cup) of untreated water from a 5 millionliter reservoir would become severely sick andperhaps die if the reservoir had been contaminatedby l/z kg of Salmonella typhi (the causative Orga-nism of typhoid fever), 5 kg of botulinum toxin (aplausible toxin warfare agent), or 7 kg of staphylo-coccal toxin (another plausible warfare toxin). Bycontrast, it would require 10 tons of potassiumcyanide (a chemical warfare agent) to contaminatethe reservoir to the same toxicity.

Chemical and Biological Agents—Point andRemote Detection

Preparation for such an ill-defined, amorphousthreat is obviously a problem. Very little workdirectly aimed at the terrorist threat has been done;more research has been aimed at the battlefieldthreat. However, some of the detection researchbeing conducted by the Army for its chemical andbiological warfare defense program has direct appli-cations to counterterrorism. There is also someresearch specifically directed at CBW counterterror-ism that is being conducted at the Army ChemicalResearch, Development and Engineering Center.

The battlefield situation differs from the terroristsituation in some aspects. In the battlefield, airborneagents would be the main, although not the onlyconcern. The role of technology is aimed at first,early detection to permit doming of protective gear;second, assessment of potentially contaminatedareas to determine if, indeed, there is contamination,and, if so, what kind there is; and third, decontamina-tion of contaminated areas.

In the terrorist case, large concentrations ofpeople or high-profile fixed facilities (e.g., embas-sies) could be targeted. Also, agents might be placedin water supplies as well as transmitted through the

16Re@o~wtive@, res~hers have establish~ that this microorganism did cause recorded disease as MIY as 1943.

IT~ere is r=ent evidence tit ~pabflities w significantly improved: the Army recently rapidly identifkd a 5* of Ebola vfis in a colonY ofmonkeys to be used for medical research in Reston, VA.


Table 4-4-Chemical and Biological AgentDetection Goals

Chemical agents Detection goals in airGB (Sarin) . . . . . . . . . . . . . . . 0.05 mg/m3

GD (Soman). . . . . . . . . . . . . 0.05 mg/m3

VX . . . . . . . . . . . . . . . . . . . . . 0.002 mg/m3

HD (a Mustard Gas) . . . . . . . 5.0 mg/m3

L (Lewisite) . . . . . . . . . . . . . . 5.0 mg/m3

SOURCE: U.S. Army, 1990.

air in aerosol form. Early detection is of importance,but to allow timely evacuation to safe locations, not(unless the targeted population has been preparedand is in a high state of alert) for donning protectiveclothing or masks. Further, large areas may have tobe monitored for long periods of time. For monitor-ing airborne agents, this would demand long-range,automated detectors with low maintenance prob-lems for adequate early warning protection. Therequirements for assessment and decontaminationafter an attack would demand similar technologies tothe battlefield case. However, in the terrorist case,time scales for action would be longer than in thebattlefield. Moreover, the areas to be covered mightbe much larger.

There are three generic types of systems underinvestigation for detecting CB agents: point detec-tors for early but relatively unspecific warning in thefield, assay systems for specific identification of theagents involved but not necessarily intended forfield use, and stand-off detectors that can monitorclouds-of chemicals or, perhaps, biological agents,from some distance. In contrast to explosivesdetection for airline security, there is no well-defined requirement that mandates exactly howdetection systems might be used. Much of thecurrent research is aimed primarily at producingdetection or assay capability that could be availablein Army field situations and in selected speciallocations, such as U.S. Army chemical and biologi-cal warfare laboratories or Public Health Servicelaboratories. Beyond detection systems, there issome portable protection equipment being devel-oped for emergency use in special highly criticalsituations.

A major difficulty in the detection of a chemicalor biological attack is the variety of possible agentsand the need to search for (often specific) knownagent signatures. This immediately limits the detec-tion process to those substances known to thedefender. A new, previously unknown substancemight well go undetected, at least for a while.Unfortunately, there are no general characteristics ofagents that one can look for. Point detection systemsare generally based on introduction of antibodies forthe specific agents, and the subsequent detection ofthe antibody/antigen reaction or resulting com-pound. The detection goals vary with the agent, asseen in table 4-4, depending on human sensitivitylevels. Generally, these goals are set at less than amilligram per cubic meter, with chemical agentsrequiring fractional milligram sensitivity and bio-logical agents usually requiring higher levels, butwith great variety. The declared battlefield require-ment for detection of botulinum toxin, for instance,demands the ability to find quantities as low as0.0007 mg/m3. Instruments usually consist of asample acquisition system (e.g., a vacuum cleaner),a sample preparation step where the antigen isintroduced, and a sensor system, which is supportedby computing equipment that displays the result orprovides an alarm.

For stand-off (remote) detection, most conceptsemploy passive optical and laser technologies. Thisfield has benefited from research performed in therelated field of environmental and atmosphericmonitoring. Optical and laser radar technologies arealso under development for a wide variety of otherapplications, including various Department of De-fense missions. The search for counterterroristtechnology in this domain often involves applica-tions or adaptation of technological developmentsfrom other fields.

Stand-off detection equipment should be smallenough to be mounted on a mobile platform, such asa van or helicopter (although there are also somefreed site applications for guarding a point site orperimeter). The goal is to observe an area with aradius (stand-off distance) usually on the order of1 to 10 km. Presumably, this range would give theintended victims enough warning time to react andtry to protect themselves. The instrument should beable to scan the critical area, detect the presence ofa cloud of dangerous vapor, determine its location,and discern its critical agents. Some of the opticaland laser systems are also called onto detect ground


contamination. Both stand-off detectors and pointdetectors need to know just what agents to look for.For remote optical detection, the emission or absorp-tion spectrum of the agent must be known in ad-vance.

Appendix D provides a discussion of researchprojects aimed at developing detection of or protec-tion against terrorist attacks using chemical andbiological agents.

PHYSICAL PROTECTIONIn this section, and for the rest of the chapter, the

bulk of the discussion will be generic rather thanspecific. However, a few illustrative projects will bediscussed in order to give a flavor of interestingavenues of research that may be appropriate andpromising.

Rather than provide a compendium of detailedbarrier information, this section describes briefly anumber of well-known, available technologies, andrefers to some documentation for further informa-tion. Development efforts in this area are usuallyengineering refinements rather than efforts to de-velop radically new technologies or techniques.

Physical protection encompasses a wide varietyof technologies that have been aggressively devel-oped for several decades. First, the military has longhad an interest in providing physical protection forits bases and facilities, at home and abroad, duringwar and peace. Further, since the advent of nuclearweapons, the Atomic Energy Commission and itssuccessor agencies, most recently the Department ofEnergy, have devoted considerable effort to the vitaltask of protecting and maintaining control of nuclearweapons and the special nuclear material (enricheduranium and plutonium) that fuels them. Both theDepartment of Energy and the Department ofDefense have active research programs to improvelevels of physical protection around both freed andmobile sites. The Nuclear Regulatory Commissionoversees an active program of protection of civiliannuclear facilities, including specific regulatorystandards for such equipment. Finally, private cor-porations, often being the targets of terrorist attacks,have pursued physical security for many years,resulting in a thriving industry that furnishes protec-tive devices for their needs.

Much of the purely military effort takes place atFort Belvoir, at its Research, Engineering, andDevelopment Center; most of the physical protec-tion research for the nation’s nuclear weaponscomplex is directed by Sandia National Laboratory.Also, considerable efforts are funded by the DefenseNuclear Agency. Many of the technologies (e.g.,advanced barriers, perimeter detection systems,alarms) that have been developed by these agenciesare applicable in a number of counterterrorist contexts.

In the counterterrorist context, physical protectionis a function of likely target type. There are domesticfreed sites, such as government buildings, militarybases, and airports; there are overseas sites, such asembassies and, again, military bases. Buildingsbelonging to private U.S. corporations, both in theUnited States and abroad, may also be targets, asmight gathering places for U.S. citizens, such asparticular bars or theaters. Plants associated with thenuclear weapons complex are an obvious target fornuclear terrorism. Mobile targets may be military,but they may also be civilian aircraft. It is of interestto investigate whether one might harden aircraftagainst internal explosions, or protect themagainst missiles while in flight.

Concerning airline security, there currently areprograms to design security systems for airports thatwould make both hijacking and sabotage moredifficult. In this field, lessons learned in designingsecurity systems for other facilities, such as plants inthe U.S. nuclear weapons complex, may proveuseful in assembling integrated systems for airports.Of course, changes must be made in system details,but design methods and many individual technolo-gies (e.g., weapons and explosives detectors) em-ployed in the nuclear security effort maybe of use.A key question, however, is the eventual cost of suchsystems.

Sandia National Laboratory has been given therole of lead laboratory for research and developmentin physical security for the Department of Energy.For several decades, it has performed work indeveloping, testing, and evaluating barriers, sensors,alarm systems, and delaying techniques.18 Manycomponent technologies are already commerciallyavailable. Originally aimed at developing the bestpossible protection for nuclear weapons, whether

lsFor~er~d de~~ discussion of many sensor and barrier technologies, see Sandia National Laboratory, SAND87-1924 to sm87-1929, JulY1989.


under transport or at fixed sites, whether in theUnited States or abroad, Sandia’s mandate has morerecently extended to assisting other agencies, such asthe Department of State, the Secret Service, and theBureau of Engraving and Printing. Safeguardsengineering research at Sandia, under which aegismost nuclear weapons protection work is done, isfunded at about $60 million for fiscal year 1990.Most of this work is not oriented towards counter-terrorism, but the results may often be useful for thispurpose.

The principle invoked in designing security sys-tems for many physical protection problems is todivide the defense’s task into three parts: detection,delay, and response. The first part deals withdetecting an intrusion or an attack by a malefactor,and, impossible, identifying and assessing the natureof the intrusion. The second part covers barriers ofdiverse sorts that are either in place or can bedeployed rapidly (within seconds) to respond to theintrusion. The last of these three parts refers to thearrival of a military or police force to respondeffectively to an attack. Detailed discussion of thistopic is beyond the scope of the present study,although mention of technologies for assistingspecific response scenarios is made in the followingsections. Technologies for carrying out the first twotasks are of interest here. Most of these technologiesare well developed. The task of systems designers isto integrate the parts into an operationally useful andeconomically affordable system. In the area ofnuclear terrorism, this has been done, althoughupgrades are continuing.

Detectors and Alarms

Detection may be accomplished by many meth-ods, most of which are commercially available fordomestic or commercial security systems. Alarmsand detectors may be deployed along a perimeteraround a site or in isolated rooms that are normallyunoccupied. Microwave sensors emit microwaveradiation and operate either by observing the block-ing of a beam by an intruder (bistatic mode, with aseparate transmitter and receiver) or by receiving thereflected radiation of a transmitted beam from anintruder by means of a receiver that is collocatedwith the transmitter. Similar techniques can be usedat wavelengths shorter than radar, namely in theinfrared regime. Also, since most living objects ofinterest are warm (about 310 K), they emit infraredradiation at wavelengths between about 10 and 30

micrometers. Passive infrared detectors use this factto detect living objects in a protected zone. Passiveinfrared detectors are being developed by theDefense Nuclear Agency and the U.S. Army as wellas by Sandia for specific military needs. Other typesof detectors, seismic sensors, pick up the smallvibrations generated when a human or animal issimply walking nearby. Still others detect variationsin electrical fields when a passing intruder’s bodychanges the average dielectric constant in hisvicinity. One potential application of alarm technol-ogy would be to place sensors around unattendedcommercial aircraft so that persons attemptingunauthorized access would be detected and, ifpossible, identified.

Each of these techniques can, in principle, bedefeated by a variety of countermeasures. A cleverlydesigned security system makes use of severaltechniques together so that countering all of thembecomes an extremely cumbersome and complicatedtask for a would-be terrorist. Another considerationin designing a system, particularly one for outdooruse, is to employ methods and combinations oftechnologies to prevent stray animals, wind, ornaturally occurring events from triggering alarms.No system is useful when the false-alarm rate ishigh.

Another useful detector is the closed-circuit TVcamera. Sophisticated electronic and software addi-tions have been developed that can make a mundanesecurity system far more effective. By comparing,for example, a current image with an earlier one,scene changes may be highlighted or, by usingclever algorithms, the system may trigger an alarmwhen scene changes corresponding to a seriousthreat occur. The software may detect changes fromscene to scene (perhaps only seconds apart in time)that indicate a human- or vehicle-sized object movingtoward a protected zone at a rate consistent with theexpected speed of an intruder.

Barriers

Barriers may range from simple high fences (nota very good delaying technique for a determinedadversary) to very thick reinforced concrete walls.Barriers may be alarmed as well. Barrier design ischosen to be applicable to the specific site. A mobilemilitary site may have a simple fence and rely ondistant perimeter alarms to protect a central zone. Anembassy may have stand-off barriers, such as high


fences or walls that are difficult to scale. One mayemplace high berms (to deflect pressure waves froma blast and to block shrapnel) and vehicle barriersscores of meters from the defended site to helpprotect against car bombs. Very sensitive items,such as nuclear weapons, maybe protected in a vaultshielded by reinforced concrete.

Delaying techniques have been developed bySandia for use inside buildings. The range oftechnologies is diverse and impressive, not alwaysrelying on radically new, high technology engineer-ing. These may run from smoke- and liquid-foamgenerating devices that can effectively impede andslow down intruders to coils of razor wire that maybe dropped from a ceiling to fill a room.

Building Hardening

Architectural design and mechanical engineeringare two disciplines of particular use to the StateDepartment and would be of use to any entitywishing to protect its buildings against catastrophiccollapse induced by explosions. One may design or(less desirably) retrofit buildings to make them moreresistant to explosions, either nearby or within.Following the attacks on U.S. Embassies in Beirutand Kuwait in the early 1980s, the State Departmentinstituted a program to spend several billion dollarson improving security and blast resistance at itsoverseas sites. Features that should be avoidedinclude unreinforced masonry, wood frames, canti-levered elements, and heavy concrete buildingssupported by thin columns. In general, low buildingswith closely spaced ties above and below floor slabsand with relatively short unsupported spans are moreresistant. Many engineering practices useful inearthquake-resistant design are also applicable indefending against explosions. There is little that isnew here, but there is a challenge in designingbuildings that are esthetically pleasing, that retain anopenness that the United States wishes to maintainin its public buildings, and that still provide someprotection against serious sabotage. Modifying ex-isting structures to have such features is moredifficult and expensive than incorporating themfrom the beginning.

Aircraft Hardening

An area receiving new interest is the possibility ofhardening parts of aircraft to prevent, impede, ormitigate terrorist acts. If appropriate lightweightarmor could be found that would, for example,

protect the flight deck from gunfire, this would behelpful in controlling attacks on the crew. Suchattacks are infrequent, but do occur, as in the case ofa PSA flight in 1987, when a disgruntled ex-employee shot the crew and caused the aircraft tocrash, killing all aboard. Areas that might beprotected could include crew seats, the bulkheadseparating cabin from flight deck, and the cabindoor.

Another promising topic being investigated iswhether baggage containers could be constructed oflightweight, protective material that could partiallycontain an explosion, venting it in a semi-controlledmanner. Possibly, blow-out panels could be builtinto aircraft fuselages at positions corresponding toventing points of the containers. These mightprevent propagation of holes or tears in the aircraftskin that could lead to catastrophic failure. Thus, theintegrity of an aircraft might be protected duringflight. Of course, a large enough explosive would beable to breach any containment one might design,since the containment mass would have to be limitedin an aircraft. However, if the required size of anexplosive were driven up significantly, this wouldgreatly facilitate the task of explosives detectors ofall types in preventing such items from beingbrought on board.

As an example, one corporation, QSI, Inc., hasdeveloped a lightweight armor, designated QX-90,which is composed of laminates of various compos-ites. Originally designed for body armor, andsuccessful at stopping 7.62 mm armor-piercingammunition in a 7/32 inch layer, this product is beingexamined for such an application.

Further, the FAA Technical Center has a programto examine means of reducing and mitigating thevulnerability of aircraft to explosions in flight. Thesewould appear to be useful lines of research to pursue,since payoff could be very high, and (at least initial)research costs in materials research would berelatively low. Our subsequent report will examinethis topic further.

Access Control

Control of ingress to and egress from protectedareas is a necessary part of physical security formany applications. In general, the facility’s securityplan requires individuals who wish to pass a secureportal to be screened for access. Usually, theindividual will be an employee who requires access


to the area in order to perform his or her job. Also,this process permits a control center to keep track ofwho is where in the facility by means of acontinually updated database.

A potential area of utilization is airport protection.It is necessary to prevent unauthorized persons fromgaining access to critical zones, for example, thosein which aircraft are located. In busy airports, thereare thousands of employees and hundreds or eventhousands of portals. Airports are now required bythe FAA to control access to air operation areas inorder to prevent the entry of unauthorized personsand ground vehicles.19 Practical implementation ofthis rule is currently underway. About half theNation’s major airports have submitted accesscontrol and airport security plans. Some difficultieshave arisen: now that specific standards are beingaddressed and described, objections from airportoperations authorities have developed, particularlyregarding cost and operational questions.

The problem of maintaining adequate entry con-trol is complex. A successful system requiressophisticated computer control and system design aswell as devices that can automatically grant accessto legitimate requesters. More sophisticated versionswill add the ability to grant different levels of accessto persons with different levels of authorization.Some areas might be accessible to all employees andother more protected areas to only a few.

The technology to support access control iswell-developed and commercially available. Themost common and simplest technique uses anidentity card combined with a Personal Identifica-tion Number (PIN) for each authorized individual.However, direct measurements of unalterable char-acteristics of the individual provide surer identifica-tion. Among more advanced technologies are four ofinterest: voice pattern recognition, fingerprint exam-ination, hand profile measurements (in which sev-eral dimensions of an individual’s hand are automat-ically measured), and retinal pattern identification.One could also simply use a TV camera-a remotelylocated security officer could compare the imagewith a photograph. Automating this process is atechnology that requires further work to achieve costreductions.

The four more advanced identification technolo-gies noted above have been evaluated by Sandia

Laboratory and all were found practical. The quick-est among the evaluated models was the hand profilemonitor, which required less than 5 seconds forexamination and had very low rates of false positivesand false negatives (less than 1 percent).

An identification technique now in the earlyresearch stage examines the pattern of an individ-ual’s iris. This is done with a TV camera that islinked to a computer employing appropriate soft-ware algorithms. The iris pattern of an individualappears to be a highly specific identifier. A computercan be taught to recognize distinctive features of theiris in a TV image and then express them in a digitalcode, which is then stored in a computer or on anidentification card. In possible border-control appli-cations, irises of those seeking entry would beimaged by a TV camera, computer-coded, andmatched by computer against the iris patterns ofthose (e.g., criminals or terrorists) on watch lists. Acentral problem in this application is obtainingdetailed images of the irises of undesirables. In anycase, many matches may have to be attempted beforeone is found, so the matching algorithms and thecomputer need to be fast.

In a more typical access-control application, irisesof those seeking entry may be matched against theirises of those authorized access.

Baltimore-Washington International (BWI)Airport Project

Sandia National Laboratory is conducting a study,funded by the FAA Technical Center, to investigatehow security might be upgraded at typical airports.This multiyear project, called the Enhanced SecurityDemonstration Project, is underway, using Piers Aand B at Baltimore-Washington International Air-port as a test-bed. Sandia is applying to airportsecurity those design techniques developed overdecades for protecting nuclear installations. Much ofthe planning is done by experts who have beenworking on physical security for years. But the effortalso uses computer programs to model the physicalsecurity system of the airport in an effort to find andclose paths that malefactor might use for hijackingor sabotage.

Currently, airports can defend themselves wellagainst one or a few disorganized hijackers. The goalof the project is to design an airport security system

1914 CFR 107.13, F* Regulations.

292-884 0 - 91 -- 3 : QL 3


that would protect the airport and aircraft against anorganized group attempting to hijack or sabotageaircraft, including the case in which there is an‘‘insider’ with access to restricted areas of theairport who colludes with the terrorists.

One technique is the use of a computer modeldeveloped by Sandia National Laboratories, calledASSESS, that tries to discern all paths by whichterrorists might introduce weapons or bombs aboardaircraft. The number of paths increases geometri-cally with the number of portals or potential pointsof access that one must defend. If one includes thecase of colluding insiders, the situation becomes thatmuch more complex. A computer can use itsenormous calculating power to find subtle vulnera-bilities not always apparent to human securityexperts.

The Sandia project is studying all aspects ofsecurity upgrading, from selection of optimal explo-sives and metal detectors to means such as installa-tion of one-way revolving doors at passenger con-courses to ensure that all individuals pass portalsonly in the authorized direction. Other concerns arethe installation of optimally placed closed-circuitTV cameras at portals, employee screening atemployee access portals, and duress alarms atportals, so that security personnel may surrepti-tiously indicate to a command post that a seriousproblem has arisen. Close attention is being paid tothe layout of the facility. If, for example, publicparking lots are close to areas where aircraft arefound, detectors and barriers should be installed toprevent someone from throwing a weapon or bombover a fence to a waiting conspirator with immediateaccess to aircraft. In addition, human factors arebeing investigated. These include motivating secu-rity personnel, making their tasks easier, and moni-toring their activities.20

Sandia intends to implement upgrades at Balti-more in the 1991 to 1992 timeframe that wouldprotect against a sophisticated hijacker threat.21

Following this, further upgrades will be aimed atpreventing well-organized terrorists from introduc-

ing bombs aboard aircraft. It remains to be seenwhen this latter aspect of the project will be finished,and what capital costs would be required to upgradethe security system accordingly at a typical airport.

Efforts to develop similar systems to designsecurity upgrades for airports are also being consid-ered by private firms. For example, Ameritec ofAlexandria, VA is trying to adapt techniques theyhave developed for designing protective systems forembassies and other fixed sites. Another firm,Aerospace Services International, of Herndon, VA,is actively engaged in the design of security up-grades at Dunes International Airport and in thedesign of security systems at the new Denver airport.

INCIDENT RESPONSEThis section deals with technologies that could be

used to deal with terrorist actions that last for asignificant length of time rather than occurringessentially instantaneously (e.g., an explosionaboard an aircraft or a car bombing). The type ofincident that is of interest is a hostage holdingsituation on an aircraft, in another vehicle, or at afreed site. There are at least two types of tools thatwould be of great potential use. One would be adetector that would allow authorities to monitorwhat was going on inside an enclosed area in whichhostages were held, so that an assault might beplanned most effectively. In the aircraft case, itwould be useful to know, for example, where theterrorists were located, especially at the moment ofassault, how they were armed, or whether anyhostages were injured.

Another useful device would be a less-than-lethalweapon that would allow authorities to disableterrorists during an assault while not permanently orseriously harming them or the hostages. A dose of anagent could be administered either through inhala-tion or through percutaneous (through the skin)penetration. Such a hypothetical agent could beintroduced into a confined area where hostages areheld to disable the terrorists but not harm the

%ecently, United Airlines installed “high-tech’ security systems at O’Hare International Airport in Chicago and Denver’s Stapleton InternationalAirport. As well as employing the latest inx-rayluggage scanners, United has looked closely at improving personnel performance throughmanagementtechniques. One example is the practice of rewarding positive performance by both monetary and professional means. Good performers are offered thepossibility of employment directly with the airline instead of remainingas “rent-a-cops” with a contracting security agency. Another example is theopen microphone at passenger entry points that permit supervisors to monitor conversations among the security persomel. Reportedly, since installationof the new system, the number of detected contraband items has signiilcantly increased. A similar system has also recently been installed at Dunes Akportin Washington.

Zlmt is, awell-org~~d gTOUp of hijack~s with advanced technical knowledge, unlike the primitive threats faced in the United S@teS tithe 1970S.


hostages. The rescue team could then free thehostages without risking lives.

There are some difficulties with this scenario. Forexample, a terrorist might wire explosives to a“dead man’s switch,” which he or she would thenhold. After being disabled, the terrorist would thenlet go and set off an explosion. This tactic has beenused, but very infrequently. Another difficulty, moregeneral and more serious in developing such agents,is that the average dose required to incapacitatemight not be sufficiently less than the average fataldose. The very young and very old, and those withserious cardiovascular or cardiopulmonary prob-lems would then be particularly at risk. Neverthe-less, one can imagine many scenarios in which itwould be very useful to have the option of using suchagents (e.g., after the elderly and infirm have beenreleased), provided the ratio of incapacitating doseto lethal dose were high enough.

Many classes of incapacitating agents have beeninvestigated in the past, from LSD and THC (theactive ingredient in marijuana) to glycolates andtranquilizers, such as chlorpromazine. Some havebeen dropped because of safety questions (e.g., rapiddepression of blood pressure or respiration rate) andothers because of lack of predictability in effect (e.g.,LSD). Ideally, one would wish an onset within a fewseconds or, at most, a minute, with effects that lastfor many minutes or a few hours.

Tests on some candidate compositions have beencarried out on animals, but not on humans. Oneproblem is extrapolating effects from animals toman. Unfortunately, it appears that as one proceedsto examine effects on higher species, the ratio offatal to incapacitating dose appears to drop. Ratiosof hundreds or thousands (which one would like) inmice and rats drop to 10s in primates, and areestimated to be on the order of 10 or less in man.Work is continuing in this area, not directly undercounterterrorist research, but having clear applica-tion thereto. Interest also comes from the NationalInstitute of Justice, which is looking for incapacitat-ing agents for law enforcement use in lieu of fire-arms.

DATA DISSEMINATIONCommunication among law enforcement, intelli-

gence, and military authorities, both domesticallyand internationally, is a vital part of counterterroristactions. There are two broad kinds of communica-

ions that are of interest. One deals with informationand databases on terrorists and terrorism, and theother concerns information on progress in researchand development of new counterterrorist tools. Thelatter sort of communication has been greatly aidedby the existence of the TSWG, although muchinformation is still not rapidly transferred. Forexample, attempts to compose a database on R&Dprogress have not yet succeeded, in part due to lackof funding.

Improvements in some facets of counterterroristcommunications can be achieved through technolo-gies. For instance, data exchange may be improvedthrough technical means, such as encrypted commu-nications and satellite links. In general, these goalsmay be accomplished without developing radicallynew technologies; it is usually a matter of designingand engineering the solution to a well-defined com-munications problem.

However, since some impediments to informationtransfer are a result of classification of information,turf battles, and legal constraints (e.g., on intelli-gence information that might be shared amongagencies with external jurisdiction and those withinternal law enforcement responsibilities), improve-ments in these areas will usually require addressingpolicy issues.

There have been some efforts to improve commu-nications among the agencies that have overlappingauthority in the counterterrorist field. Members ofcognizant interagency committees are supposed tokeep each other abreast of their own agencies’information in the field. Among other things, theexchange of R&D information is meant to avoidunnecessary duplication of research efforts by theinteragency group. OTA has not yet assessed thedegree of coordination that this process achieves,and will report on this in the future.

Another example of interagency data exchange isthe use of a “flash board” system, essentially anelectronic bulletin board among Federal intelli-gence, military, and law enforcement agencies thatallows time-urgent information to be exchanged onsecure lines in near-real time.

One major technical effort in the data dissemina-tion area about which OTA has so far receiveddetailed information is a large computer softwareand networking effort intended to assemble, update,and correlate all known information on terrorist


groups. One eventual goal is to achieve a roughpredictive capability of terrorist attacks--obviouslynot a precise prediction of target, date, and time, butrather an ability to issue plausible alerts over periodswhen attacks might be expected. Another aim wouldbe to attempt to assess the nature of a specific threat.

The fundamental concept is to arrange informa-tion by terrorist group. Information may come fromintelligence sources or simply from an open sourcesuch as press reports. It may include items such as

movements of group members, money transfers,movement of equipment, or group dynamics andpolitics. One important systems aspect is developingappropriate protocols and formatting to input theinformation in an efficient way.

The eventual goal would be to provide generalwarnings such as that a given group appears to beplanning an action, with general ideas of the type oftarget one might anticipate as the object of attack,and a timeframe for maintaining an alert.

chapter 4 research and development

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