Congressional Research
A \Nibervice
Detection of Nuclear Weapons and Material
Trang 2tn of Nuclear Weapons and Natrae:Sienr, ecologies, Oseeatons
Summary
Desection of clear weapons and posal clear material (SNM, pteinn, snd certain sypes of uranui) i eucial wo thwarting ater proliferation and rors and tn secuting weapons afl Imuteas worldwide, Congress hax funded a portfolio of detection R&D and axuision
Prosrams, apd has mandated inspection a orign ports ofall U.S bound cams containers using tho pes ofdstestion egeipmen
Nuclear wcupons conaia SNM which praduces suspet signatures tat can he detect mits Fado, notably gars rays (high-energy photons) and nevtons SNM is dase so ic peices aight nage on 2 radiograph (a picure like a medical x13 when x-ra3s or gama nas ae hese Uueh a conan in wih i den, Using Teal a the sien alter lun fas would ake that ngs larger Nuclear weapons pre detectable signa, sch satiation or noticable image on 3 tadograph, Ober detionlehigues ate aso availabe
[Nine technologies istered detetion portfolio: (1) ae Seinllaor mstesal impr dexector performance and wer cost Ths projet as termed it Jabuary 2010 (2) GADRAS, !napplcstion using np algorithns o determine the meas in 3 eotainer by analyz
uiraray spect, I rstertals ane the “yes al eas of detectors, alot ae the “bets.” {Gy proce to snlate large numbers of experiments to inprove detection system perormunss 14,5) Two Cargo Advanced Automated Radiography Systens (CAARS) to detect hgh density ‘mitral nese onthe principle ha it becomes ess iransparet to photons of higher encry, talks other material (5) A tind CAARS ta dtct aera wih ih atomic mimber (2, momber ‘of protons nan atoms moles) based onthe pnp that Zatflets how material scatters
photons This project as ermnated in March 2009 (7) Aspstemto generate a 3D image of the ‘Contents of a eoniner based onthe principle that Za density sol ale the deste ‘wich mans a substome patie seater (8) Nile esonance Muonescence ining fo
‘densify mara bạ on he De<ru of gamma Eys a mele emits when stuck by phtons ‘of aspocfe energy (9) The Photondclear Mspection aid Threat Assesment System to detect SNNM nọ lạ L kina, walks other ystems tha operat at yey cose range I wut bea high
sry pons asian tarps to tilts fssion in SNM, prodcing characterise sgnatures ‘that muy he tet These technologies are selected noe because they ae necessarily dhe "best inthe categories, bat rather to show a varey of approaches, in illering tages of mati,
efor by ctferen type of aeanizasions, elyne on ileret pial pencils, and ‘Covering bulking blocks fester algorithms, aul) aswell as ystems, so a eave Trang poison the specim af dkteston ecnlogy development
“Tis analysis lead o sever ahservation for Congres, It is dificult pret the seeder sapbiiie of new dtestion technologies Is easier ad les costly vo aceleate a pears in R&D than in production, “Concept of eperations” ts etucial to detestion system eToys ‘Congress may wish 0 address gaps and syncaisme nthe ecology potolo Congress noe not depend solely on procedars developed by executive agencies io tes detection cchnologies,
Bút ay spect tests an agency is to conduct Ongoing inpeovemet in detection capabliies rowces tnceraimties for terorists that wil increase overtime ding dlertence beyond that of The capabilites themselves
“Ts eport will he update eeasional
Trang 3-ĐdecHơtgƒ Ngay Mapons s4 Naeiale de, Tzlmolagis OferaaHonc Contents
‘Chapter 1 Nuclear Weapons and Matefils Sjghaure ai Detexion ‘What Is Be Detect Phatons 101
‘What sgnaturcs show the presence of mclcar weapon and SN ‘Opaciy to photons
ow: Does Detection ‘ow ae signatures pathefed, processed and used? Wark T i Se a Prigiples of detection,
Means of detection
Evasion of dtetioa echnologi Curent Detection Technics Raalton "pats nn
lta portal oni
Raoetive isotope identification devies Raxhosraphic iasing systems
‘Chapter 2 Advanced Technologies Nanocomposite Sciillatos "The problem
Background
‘Teno description
TPMIENA]AdtaBatS ooececeseeoe Status, schedule, and funding
[Risks and concerns Potential gains by increased unding
Potential syneeisms and elated applications
GADRAS:A Gamma-Ray Spectrum Analysis Application Using Multiple Aigriths ‘The problem Background
‘Teehology descrip
Poteial advantages Stas, schedule, and Funding ‘Risks and concerns
Potential gains by increased funding
oven synereisms and related applications Computer Moding to Evaluate Detection Capability “The problem Background
“Technology deseripion Potential advantages 27 » Status, schedule, apd funding 20
[isis and concerns ”
Potential gains by increased funding 31 Potential synerisms and related aplieations 31 3 CAARS: A Low Risk Dual Energy Radiography System “The problem 31
Backaround
‘Testaology descrpion 5
Trang 4Dateton of Nuclear Weapons and Matera: Scone, Teo, Osroations
siti si
‘tau, sched, and unding 7
Risks and ences Potenialgains by increased funding aL »% Potential synerisms and telat applications 2 SAIC CARS: Higher Risk, Higher-Beneit Dual Enerey Ragograhy System “Technology deseripion 4 2
— oes al
‘Status, schedule, a funding 4
Risks and eoncens 4
Potenialgains by inetd funding 40 Potential synerisms and related applications + ASAE CARS: Lsing Backscattered X-Rays t» Detect Dense Matra Background 2 0
‘Tehaology descrip 31
Potential beni
‘Stas, schol, and funding
Risks and concerns Potential gains by increased funding
Potential synergism and eat applications ‘Muon Tomography “The problemen =
Background ‘Technology descrip Tlenialbsbefls
Status, schol, an funding Tids amlcủtee6 Potenialasins by increased funding Potential synerpisms and ter applications
Scanning Cao or Analyzing a Tertorst Nuclear Weapon with Neclear Resonance
Fluorescence ‘Two problens 70 70 Backemund ‘Technology dseripion 7 2
Potemial ener a
Stas, schedule, and funding 74
‘isis and concerns 75
ote gains by increased funding 7 Potential synereisms and twat applications 7 Detecting SNM at a Distance “The problem Background ‘Teno description Powel enets 2 ‘Staus, schedule, and funding
isis apd eoncens
Potential gains by increased funding
Potential synerisms and related applications a3 ‘Chapter 3 Observations ‘Observations on Progress in Detection Tecnology 3 8
Trang 5-ĐdecHơtgƒ Ngay Mapons s4 Naeiale de, Tzlmolagis OferaaHonc
‘Observations on Tecnica Progress and Congress a7 Observations on Technical Progress aml Tem 9
‘What Is to Be Decca mỊ
Background Pha Raioatit Tel ngư
Daeinn ‘Shielding and hackground ation 2 REESE sử 9 Sigratures of Paoniuns, Highly Eniched Uranium, and Nod “Atomic numer and Jeni en z 93 95 ‘Opacity to photons Presence of gamma rays beyond background levels % % Presence of neutrons beyond background levels %6 Ganma ray spcira
“Time pattern of nets a panna 395
sions tie jamais
Dats Signatur of Nock Weapon ‘Osricw: How ate siaurs gathered proces an usc? % How detector work Dating gamma rays 100 103 Dating ets tr Datetingabsotion oe satring of higher’ photos 10s Evasion of Detection Tato 3 as Figures
Figur 1, Canina Sposa Urania 235 ys Background 4 Figure 2 Canina Spe: Wapons-ade Patan ss Backsound 5
Figure 3 Gamma-Ray Spectra 91% Uranium-235 vs Background, Taken wih a PVT Detector Figure 4, Gamma-Ray Speeta of Plutonium 239
Figure 8, Rhone Csin13 Gana Ray Speen by Dison CZ
Detectors Has Inproved Over Time 0 Figure 6, How GADRAS Wnts Spoil Neckar Mati — Figure 7 ANotional Receiver Operating Characteristic (ROC) Cum 25 Figure 8, Three Notional ROC Curves, os : 26 Figure Duab-Enerey Radiography 4 Figure 10, L-3 CARS Schematic Drawings 36 Figure 11 SAIC CARS Protorype eh Figure 12 Dual-Enerey Radiography with False Colors Assigned 45 Figure 13, £2-3D™ Ditfretiates Butween Flements by Atomie Number (2) "`
ieare l4, Schemtdie Diagram of EZ-3D TeehrigMe,
Trang 6ton of Nuclear Weapons and Materia Sin, Tecnologie, Obsrations Figure 15, Scheme Drang of Muon Tormgraphy lspestion Staion Conigurations:
unael an Toy Bodom, sẽ
Trang 7
yd aerial: See, luong OfegzaHont
"ake thon for muny years spewally since /11- Nuclear detection has many
applications for coantesngeler terrorism and raclear proliferation, sch as scr rocker weapon and materials in US Russian, and other leat facies traching musias at onde erossnes an choke points, seneening maine cargo conuers, and examining actual or —
C= as boen interested in detecting nuclear weapons andthe special strils needed
Ths United States euremly uses several types of moeear detection equipment All have
siznitiant shortcomings Some work only at very shor ana: some cannot ident the material iting Fada, heh ean lena (o alse alas and atest ema: sons depend on ‘pert sil ax ay be defeated by a cher uygle ot slgpy peat: ae some fecal “efeated by sheng In effort io evercne such problems, Cones has funda pipeline of sdvanced technology ressarch, developmen, atl wcisio,
This ror sees to help Congress understand hs technology Ie seuss the eience of dksovtngnuclest weapons atl materia, describes rine advance US, technologies seketel tố ius the range ot projets in the pipeline and offers observations for Congress The report ‘docs not compare echnokgics.! The inclusion ofthe ne technologie sould ot be taken to rsa hat CRS jes thor oe he han ths hun of fers not consigcre here Te
repo does na dives he conttoversalAdkanced Spectroscopic Portal because adele iscsi oft ul da aentin fom thee techies conse hte,
The scope ofthis rp exelides the organization ofthe government for dealing with miclar lection the foe of iligence al ln enfoccrent in detecting eros nlea weap “tection of ralogical dnpersal devices (ch a Wty bombs" the role of nace Forerses in gibaing an atack to + tr, test a nackte adhe acne of 3
raion milear dct system, No does t seus possible means by wich servis mgt tejuie atin, or whether they cal make ạ honh na throwL Mạch bay heen writen on thexe ties.” Wile many wh ate enero with clear detection focus on thwarting náteur teetyieh thc reporfeeuses oa tehgology pers I avoids extensive diseussion of means ôâ our detection to avd classified in
[Nuclear dtston technology fs a dt rle in hating eros cae wtack—deteronce and defense Deterrence mss dssuasion roman action by tect of unsecepae consequences “Temnwists muy be deterze fom a nuclear stfke by onc the fe consequences unscccable © them: faite, Detection apse woul ase that sk Those system co alsa make a am
Trang 8ton of Nuclear Weapons and Materia Sin, Tecnologie, Obsrations Scie erate forthe plot would defect, Such sishs would dbappear, however, items snore given a Bomb and operating instuctons They would then pay need to mous 2 siuagling ‘eration nthat cas, da ic of macleardetston systems would change: they wouk! become the main defers
Chapter 1 Nuclear Weapons and Materials: Signatures and Detection
As hackerond for derstanding the detection lachtologiexin Chapter 2 this eater ones Inwler detection sence, The Appendix provides note deta
What Is to Be Detected?
section focuses on weapons athe mielear materials tha fel them Weapons xn be sl by ‘he Cold War, he United States bul heh yield weapons several feat Tons tome demolition ‘moniions that a solder could cary, and clea anilery shel Á toi weapon woud Probably be lrzer
[Nuclear weapons rire ile material, atoms of which cam sion (split) when struck by fst oF slow acutroas': pieces ofthis wateral an support nuclear chain resetion The si atrial tse in nuvi weapons are uranium, isotope 235 (U-238) and patniun isotope 239 (29) The Atomic Energy Act of 54 designates thom as "spocal nace mara (SNM) Uraniom iernaur is 09.3% U2 and 7% L-235: U-235 must be concerns “tc” Ura
erica to 208 1-285 i ered highly enriched ura, ot HEU, bat lear weapons Iypially use uranium enriched o 906 so, bis reports HEU refers this weapons-grade érrichmeat level, Weapos-rae plutonium, oF WGP, ao a Mixa sakes a lept 93% Pa 230, Accondng to ane scout hy ive ntclear weapon seientsts from Los Alans National Laboratory it would take 26 kg of HEU or Sky of WGPu to fuel a hom.” amounts that ould it into cubes 1 emo 6 cm rexpectively on a side
Photons 101
[Nuclear dotcton makes extensive use of phon, packs oF emery with mo est rss a no lecl charge Bkeeomsgneti enation east of pons, ad nay he sass
‘wavelength frequency, or energy; for cotieteney túc DA ses only energy expressed in units ‘of clxton volts (eV) Levels of enemy commonly use in lea dtetion ae thousands 0
Trang 9
tn of Nuclear Weapons and Natrae:Sienr, ecologies, Oseeatons nillions of eleeton vot, keV anal MeV; respectively The electromagnetic specs ranges fom Tao Save (sone of whi hav pow energies of 19” eV) cough visible lt (a fw eV) to hisher-enengy xrays (10 KeV and up) and gaa rays (mostly 1 keV and
Xray phos and garom-say photons ofthe same energy are ietial, However, they ate generate in diferent ways Gama rays originate in processes nan tom's aves Each Fatouctive isotope that eis gama rays docs so ina ung energy spect asin Figure 1 ‘vic ste ony way ta deny a step pase a abortion, A tector witha form of
"identify" on "spect is rae, sch as Advanee Specimen Portal ot radoaetie isotope Hentiieatin deve, idelfies chops by their gammy spectra X-rays originate in ieractions with an atoms estan, Many detection systems use ay beans, which ext have Iiher energies than gaưnnh ray am th ae nore penetrating Xray sas ae fe genet Muugh the Drensratang proces, German fr “braking radiation,” which works s follows, AN stecelertor crestor magnetic fel that soselrates charged particles, such as cevtons, which Slam ina tape of heavy sata When they slow or change diretion asa fel of iterations ‘vith atoms they ease energy as nays whose cnerayTevels ave cite ron nar 7a lơ the energy ofthe cleeton eam, They donot exhibit spectral peas he gamma rc
‘What signatures show the presence of nuclear weapons and SNM?
For purposes of this ep, signature isa peopety by which a substance (in particular, SNM) nay he daecte or kdetijeL The segion presents several signaurs The Appendis al ‘Chaptee 2 discuss hors
Atomic number and density
‘one name, sbbesited "7," the mber of pron in sn ato miles Is a property ‘Finivideal atoms Te cones, desig 3 bulk propery expressed as mass per st volun In ener the densest material afe dase of gh Z These propertics may be used detect uratigm,
plutonium, Uranium isthe densest and hishest-Zclemes found i zur eter than in race ‘quantities: plutonium has slightly higher xighly kexthan Hạt rang, Some dtctionmatds casei Cape 2 sic as Z (04), an its density saris from shay aoe to
tfletive Z make use of Z, an som, sc as radoerighy a non tomography, make se of Z and density combined
Opacity to photons
A ojos pacity toa phokn beAm depenð on ts Z adept, he moun af mati in the Path ofthe beam, au he emery ofthe pons, Camana ays and rays can pera more tater thin can loner photons, bt dense high-Z teil absorbs or eaters thom Thos ‘vay to detect an jet, sch som conn so em in ayo eam ays La te a nosranh an oly map) Hea medial xinh,
Radioactivity
Ragoactve atone are unstable and give off various types of radiation the types of use for rnclear detection are gan 1 and neon
Trang 10Datetion of Nutcar Ws
Sconce, Tectloges, Obsereations
Garam vay -Ganraray spesten are well characterized for each isotope, Figure fad Figure 2 show spectra for HEU and WGPu Each point onthe spectrum shows the numberof photons ‘mitted (vertical ais at each energy level horizontal axis) Background ubigotous Since many materials, including SNM, emit gamma radiation, elevated levels of garnma radiation s
amma radiation may or may ot indicate the presence of SNM, but careful analysis of the total ‘eumma-ay spectrum, as discussed in Chapter? under GADRAS may reveal the presence of SNM Of particular invert, uranium that hs Been though ascleae reactor picks up a very Sill anwunt of uraium232, which decays though intermediate steps to thal 208, The later has a allie of 3 inte, ands decay produces a gamma ray of 2.614 MEV (as sosen in
Figure 1), one of the highest-enegy gamma rays Asa resis ditinetive as well a highly enacting, faitating detection,
Figure 1 Gamma-Ray Spectra: 90% Uranium-235 vs acground HEU 90% 1kg livesets) 2400 18 104 10 tới 10! Counts / keV 1ơ| tơ sort 1ø? 500 Teco 1860 T36 T560 3000 Energy (keV)
Soure: Lawrence Livermore Nao bert
Notes: Spars ner nen witha hihpunty gear dtctor at stance of | mand comguted with he [GADRAS norm sce elm: Urs relied bru ie Te re ne et per ine mrad sera * For fern on ye srry nn a wel ashing wl ion of wou, 6 ‘Bernd Plas Compr sf See ean Pane Canina ay Dec Met Teeevlae
visti eplcubshreestervie yrogmneP SDI 90162 SHDN gaye -aleKpicseRfismml T Lemley eta "Contrary Messer fr Ueno ser egos by Tết Reuvie Cammy Sperone RCS" Brune Nem Latency, BNL 635%, ay 8,19,
mm."
Trang 11
Datetion of Nutcar Ws Figure 2 Gamma-Ray Spectra: Weapons-Grade Plutonium, ‘vs Background WGPu 1kg tơ 108 0 10! live-timets)= 2400 10 Counts / keV tứ 10! w ` w NO 1500 2000 2500 ~~ 3000 Energy (keV) Sourea rans Lemar Nin Lb
Notes: Spacra were sen with hp gern decor stance of | mand compute with GADUS Pesan mana gene are Termin stars her nna) [Neurons Atoms of some heavy clement fission Ofte naturally occurring elements, only U- 238 spontaneously fissions at an appecable at Fission releases neon U-235 emis few eutons, ut because U-238, the ther main component of HEU, emis some 1 ky of HEU emits 3 neutrons per second.’ soit provides a weak signature Plutonium emits onthe order of 60.000, rcatons per hg per scond depending on the mix of plaonim steps," Unlike gama a rneatons donot havea characteristic energy spectrum by which an isotope canbe ited
How Does Detection Work?
How are signatures gathered, processed, and used?
Detection involves using detector elements to obain data, converting data to usable information| ltwough algorithms, and ating on that information though concep of operations, or CONOPS,
‘nn 08 9.38 ơn
Trang 12tn of Nuclear Weapons and Natrae:Sienr, ecologies, Oseeatons Desectrs, slgorithns and CONOPS ate he ees ad eas rains and hands of nuclear deteton: effective detection ries al hee
Since photons and neutrons have no eetrcal charg, their enti converte to electrical Pues that can be menue This he task of detectors suse ext The ples are fe 0 gorithms A algorithm, suchas 2 compaer program, is fit et of logical steps for salsing a Problem For mileur detction, an algorithm mast process dita io ueable information fast, fnoigh to be of use to an oper Irons data fom a detects arvare, sch as pasos reprsenting the tie ad emer ofeach photon aiving tthe detector, Kt cnet he phe loa, Format tata usr ean derstand, ie® s* ổnplayng a garana Fy spectrum oe Hashing “ern” ery detector uses one a move alvin provements algartins ca cone asm as hardware improvement to detector capably,
‘CONOPS may be divide imo two pats, One spss ho a detection units tobe operate 0 ‘obtain data Pements include: How any containers mast the nit ses per hoa? Hote cone ‘would a detstor be k' eontsines? Sal the uit screen cara ina single pass sal it he used
For primary serening with suspicious eargo seat for amore dale secondary seeing? A sccond pat details ow the data are to be used, Elements include: What happens the eabipmsnt leet possible heat? Which alarms ate to be solved onsite upd which ate to be referred 9 ‘offsite expens? Uinde what sitcumsanoes ener, ho isthe low of data managed in bet drctions?”" What types of intelligence won port or boner crossing he clase? Mare
Feormation o iRpeeevs teite, and hot do data fom detection stems ot Feral, tae, loa ca For analysis acto?” While this epot das ot Toes a CONOPS cane is ota technology fan essential par oF maces? deci,
Principles of detection
Detectors fet sgna-to-tsse ratio high enough oper detsstion Tha i hey’ mst evel th re signal (such a a gamma nay specu fom mse (sh as spurious iefis ‘suse by Background ration) Twa coneapl ae cena W gaanaay detest septs) “ksection effeieney ad spectral resolution FMieeney refers tothe anu of signal a detector
records Ration imensty (eg, mer of phsons per unit fate) dininishs with stare: Since lamp of SNM enn rciation inal rstions, using «descr thf larger tht ‘lost to the SNM iczeass the faction of acto Ire suave that impinges onthe ‘dicctor und therehy inercases efficiency Another aspect the ration of the ratation striking the detector dst creas detestable signal A mone eficint detector collects dats lstr, sd
Ih time to seen a cargo amano Spectral rsoaton efor to the shames of pou in a gemm-ray spectrom A perf tector ‘would roca spectra as vertical “mows” becuse ach roast ope felcascs gn Fays oly at spetie erie Since detectors are not ple each energy pet rome a 4 hei cuve, The parower sein eatin detectors thal eh be Felden re sets at 1 est i eit ut Ps Poe he curve, the mre ussite data Psi taene (PVT), a plistic
‘soln It can deta adaton, bu peaks fom ganna rays of dieret energies Bur toed ‘wich can ke tinal oidndy an stop Figure 3 shows the spciea of 0% (V235 and background rataton a eco hy a PVT detector In cones high-parygermsnivm "pe nt was of itp oe CRS Rep RUD, avo by
Trang 13Datetion of Nutcar Ws
(HHP produces sharp peak, permiting clear identification of specifi isotopes Mase detectors ae expensive heavy, havea smal detector area, and must be cooled to extemly Tw
lemperatures with guid nitrogen ora mechanical system, making them less than ideal or use in the el Figure 4 shows the spectrum of Pu-239 as recorded by detectors wit beter resolution than PVT, Figure 3 Gamma-Ray Spectra: 90% Uranium-235 vs Background, Taken with a PVT Detector HEU 90% 1kg lvestime(s)= 2400 tớ tú tú ‘Counts / keV Energy (keV) Soure Lawrence vermer Nao abort mm {hehe cg dre The ure tn rah pre fas,
Trang 14Datetion of Nutcar Ws Figure 4 Gamma-Ray Spectra of Plutonium-239 Counts (log scale) 0 50 100 150 200 250 300 350 400 450 Energy (keV)
Source: Lo Atmos Natal abort
Nota: Taare pt of 6 plaun98 Thy are aan tng re etc tro ham (Shean mrss on phon toau oe mad pa) th an xara T2hyiec =dndvn oivide mì sư Evnerve Th ees ened sone ear a ow any “———.-
Sensitivity can be improved (1) One ype of detector is eadnium>-zine telluride (CZ) ental Batter c7ysals anal better ways to overcome thet intations have improved sensi The peak ‘onthe right ofeach spectrum ia Figure shows th cesium I37 spectrum taken with CZT
“eo tt, forthe years indicated, were at the igh end of sentivty (2) Detectors build radiography inages of gamma-ray spectra ever ine With more tine, a detector ean collect more ‘tain the formof gama rays or noutrons, More data improve scparatin of signal from noise tnd reduce false alarms Longer scan ines improve accuracy but impede the ow of commerce, ‘ontng money, 0a alance sought between these two opposed gos, (3) Tncreasing Ue spatial resoltion of a detector improves sensitiv:
Trang 15Detection of clear Weapons and ates Sin, Tecnologie, Obsrsations “Thsisesly demonstrated inthe example oa sik ses unser Unilin dct se cnt orto psig on tl ens i dex,
‘hares etc Fe view can fe coll, ad backround ation loves rede, ofthc tro atl orig bukround adie, 8 dang cng fnernsng he inal ise to or th dete in he eto he tee i”
Trang 16Datetion of Nutcar Ws Mater Figure 5 Resolution of the Ceslum-137 Gamma-Ray Spectrum by Different CZT Detectors Has Improved Over Time 8000 13% 1995-1988 2000) ¡ mm—— Ả | 8000) 6000 2000-2003 Counts 2000, 8000) 2008 ‘6000 2000, 0 200 400 600 800 Energy (keV) Src: boat Nao Libro m”m fered hee nti og cd pee psa nr ceca
{ones seroma sd) woh sn dst At Stns the APN ry Means of detection
[Nuclear detection uses neutrons and photons i various ways Because either neutrons or photons ‘an rely pentate most materials, they are the main forms of radiation sed to detect
Trang 17tn of Nuclear Weapons and Natrae:Sienr, ecologies, Oseeatons Fadontive materia passively, sbch 3s by sensing eaiaton coming out of a cargo eosin ‘Gana rays and cays through radiograph which erates an Xzay-type image: Neus of any energy level an can be we ina active mao poe a conan for dense material
rihtons shove about $6 MeV, cat he hears int 2 conainrfo nace fission in SNM, Fission reset the emission of ners a anna ys, which ean be de ai
Detecting gamma rays
‘Gamyna cays do not have an electrical charge, hu an oleic sig is needed wo measure thera ‘There revo mai was osu a ganna ray ino electrical energy One is with a seiner rater, such as PVT When sarin ray ntrats with this mati ets my Tower foray photons of visible fight, A phtomuliper the convert them a ckextzons, ten miles the eran to generate a mstsoable pls of eectrcty whose voltage propeional to the rune af lowe energy photons, which in rs propotonal tthe emery deposited 9 tha fans fay AM lactone dovce called a mache analyzer sorte pls io “i Alepending on its energy a ieveases the uber of cousin ha in by ons Asotware puckoge draws histopram with enerey on the frontal ais alerts onthe verte axis, The
Fstop isthe pare ay spectrum fr tal iotpe, In vont, a semsvadctor material, such Aas HPGe tun gama rays dtl to an elxlddl signal propo to te gamna-39 Energy deposited A volage i apple amos the mata, with onesie ofthe atrial he Prsitne elec ad the other the negative elt, Whe ganna ay smectite Intel knocks cocttns lose fromthe semicondctors crystal latce The voge sweeps them to the postive elects, Mir mation proces an else current whose voltage is proportional to the energy ofeach gama, ach pe of currents then sere ia in Aspeing on its voage ak the spectrum fs computed as deseried above Detecting neutrons
‘common aeutondstetar is tube of lum gas Finke toa power supply: wth positively tnd negatively charged plates irs in be Iuhe T9 r4 giữ chen canne pass tough the htians cause aes 3h an isultor When 4 loa: net nentton passes thang the ue, a hotiun3 atom sbavbs , pralkine energetic charg pats a ose Heit ener 9 Kaveking electro off ether helium atoms, Posively charged particles move tthe negative Plate; clacitons move tthe postive ple, Since eletee curren he aovement of charged Tel the paile generate a tiny cletre cen this ote Neuron count i a Figoram way to ris SNM hecause SNM and U-23 emt neurons spontancodsy ia significant nutbers, Few oer sources do, Neutron spot are of ite vale for idenilying isso, They do ot have ines represen discrete ences, ae etn love ee a thi ‘olde with low materi urs thet spectra, However, sin hs boson ete Scarce and naan detection systems fr inna souriy would Regie so rach of tat
Trang 18tn of Nuclear Weapons and Natrae:Sienr, ecologies, Oseeatons Detecting dense material
Photons of high crow e.rEy can penetrlesolidcồjst bạt sự scattered or absorb hy dense hjetstor3 suffidem tieknexs of ew-dese tesa), Thies the hai for ratios: Por ‘avo scanning, a9 earns ay ave Beara thvouh a conn, aa detector onthe ther side records thệ định of phates ecived in each piel An algo then eats an opacity imap of the contents, Wile a hom would presen sizable mage, dese abject 4 snaitir inh task apse of SNM
Evasion of detection technologies
An enemy cowl we varios means in a lft to defeat ctcton systems One sch mane Shielding, Canna rays may sel sy fx tush sich low: mera as ood, fo, aa Phi, ba high Z neteal absorbs and defects them Covers, low mate abs an Scatter patrons, bat they pass more ted Hough higher 7Z- wate, Dire ipauts of natal are noted to aenoat gamana rays depending on tei quay and energy level ‘Gam cays from WGPu ae suiiorly enrgstic and pen that they are fcuk o shih wile ayer of lead woud shield gamma fay fom HEU), especially if thal ot been th reactor and, in consequence had no picked iso practical significance Pres epons inate hat ras using eearuges fo eaich ura up uraniun-232, as aiscussed above This dstintion
fom chemical forms derive rom rani ore, which have not ben meh a react
Sources of ration other than SNM complicate detection ackgroucd raion fom mately ‘cettine ranactve mgtefil, sìc ae (hofom and urns present everyhere often nce "outs, Cosy ras generat low levels of nentfons, Some commercial soos conta
Fate mera sich a evn (wie ay contain uri) aa it ie (hich may s0yain hi and raniom), Other rete stapes are widely used in maine aul industry
[Enemy stomps o defeat one ype of atection system may complicate a plat oF make ¢ more setae (1) fisher to deat systems that detect muliple phenom than a syste ‘set one phenomenon only For example shildiag a bomb with ead to atenvate gam rays would cea a large opague image on a radiagraph For this reason, Congress manatd tha
[US bound eomainers led in foreign por’ he "scam by ponimrusive insging equipment sn adation detection equipo a frei port before it was aad on vessel (3) Am “oy could allem salvage Turing, which would detonate ep tha senses leans 1 ‘tet ise 8 wah photon eam, oF loop it, However, salvage fein coal donate 2 ‘weapon hy acide i it were seaed overseas o inv U.S pot, here it ul do ac ess
Trang 19ton of Nuclear Weapons and Materia Sin, Tecnologie, Obsrations
Current Detection Technologies
The United States deploy varios technologies, such as the Following to detest nucle weapons ‘oP SNM, They ate aailable ha ave importa dewsbacks,
Radiation “pagers”
Tese deviees, out the size and shape ofa pager can detect radiation a else distance to alert inva othe prescnee of elevate level of rabaton, They ny tse any of several types of ‘exector aerial They ate lighsweight sid inexpensive, Du ean enti Hh material eausing an alam,
Ra
mn portal monitors
“Many ofthese devices use lap sets of plate scnilatr material such as PVT to detect, Fastin coming from a vsele RPMs wore deployed soon aftr 9/1 hers they were
fable meuefate cos, However, PVT sana enti the source a raaton, Yc many’ items ineveryday commerce contin rachoactive mitral, Asa resi, some RPMs price nay false alan, which ay equi considerable effort To solve delaying the tow of eomimerce, Newer ‘estos have some isotope deniiation espahiiy
Radioactive isotope identification devices
“These devices are typically hand-held, They have sofware hat cn siya raisotepe by is eamnsray speci The mos capable o These devies se a esta of hil piy sere, a semicoictor Materials ate considered the "gold sada al identeation devs Such devies are heavy and delicate, ar nus be ele with gui nttgen by mechanical ‘means iting thee usability in he fel Thy havea elavely shor range for cect dation sours with fo roasts stably shied HEU walking them unsuitable as the Primary mith of scroning cargo contains,
Radiographic imaging systems
Tiwse devices so igh-eney photons dough cage coniners to erate a eaingranhic nse ofthe contess, Te raograp is seamed, either autonatialy or by ah petty, eae fe tucker weapons, contraband, stowaways and othr Met ergo While nuclear weapon would show ap as @ white or black) inuge on the radiograph and would be elcary visble f dden in a shipment of low-2 masa ike ood or pape an operuor might overiook iit were in shipment of ther age dense objects oud tems of various sizes an dejdee Ä mail ove of SNM migh als be overlooked
Chapter 2 Advanced Technologies
‘Many ice detection tchaolosy pst ae under way in the ite States an elem hove “Tis section discusses ine US technologies selected to incl ilferet (I) agencies, sponsorins projects (he Defense Theat Radon Agency (DTRAY, ah agerey ofthe
Department of Deferse DOD}; the Domestic Nuclear Detection Office (DNDO} a ageney of
Trang 20
tn of Nuclear Weapons and Natrae:Sienr, ecologies, Oseeatons ‘he Deparwnen of Homeland Secutty (DHS): an the National Nielear Set Adminjxraion (NNSA) am agency ofthe Department of Energy (DOE) (2) organisations performing the work (oationalahorstores,idstyniversitcs, an ollahoraons hese thet) (3) pe a tecinologs (matrals, algorithms, sinalation, systems), (8) pyscal principles (cm
lemerapi radiography lina emission of ration, nck Reonance Muorescence, (3 dlisioncex between the delete aa he oj bene see (eal fa, ad (6) eve of Imari Gin use for any yes hut coastal update, near ckployment, an ciated to be
svalable for deployment in several years), This section does nx onside tachnokies in the tarlest stages of development becase fs tao soon to tel haw they wll pan ou, Te session ‘of each sechoalogy inludes Several categorie: + The problem that dhe technolgy aes 1+ Technology background + Description of de leehnelogy Pose hones shat the technology ofers "`
‘Scion, engineering, cost and schedule and operational sks + Posen sain by increased funding
"`
The ls shee eatogories rege some explanation
Risks: The discussion presents potential Benois ofthe tecolegies Ides no set “sos “That would be premature ocnsse development progrant aes problems Ite sóc section is risk, There sre sever eateeris of rth Seine poms may thar [Eve its scientifically sound my be bat eo engnees oto a workable system, Exe Ht ca a technolo hoenginesrd, i my he unaffordable or uke to log to devel Even iit ean suena these ude, problems encountered in fed use may render i unatracive
Potential gains by ineeasel funding: In preliminary discussions, project managers asserted they would, iF given more funds, ase the ale Tun to solve pfnbiemh or exphit opportunities ‘ERS therfore as snags of lane veshnolocs considered i hs report how they woul spend more money as 2 wat peobe for priblems and opportunities with ter peojxs Would
they pare several pmmising es toa technology nse of pursuing only one at theo? Would hey hay more equipment so they could sped up tn ork? Would they hire res sal?
This analysis apis only the nine technologies seuss in dis port es mt intent fens aahorization oe appeopaion consideration solely on them ther tehnolges nat consider hee might aie larger (or smaller o mo) gait Ueoueh increase anne,
Potential ynergisms: As the echnoldey desrpions sow, may systems have common elem, sich ay cern ype of aero alorthns and Work enone teshnooey ny “connate hase appations beyonce pas
This report mow discuss tc of the nine technologies using the above for
Trang 21tn of Nuclear Weapons and Natrae:Sienr, ecologies, Oseeatons
Nanocomposite Scintillators*
As of January 2010, DTRA ans! PNDO terniate the naconpsite silo projet Ts Seetion, defor, will ot be update further, ht conknues a hs repre Because i eons ‘alubleinormeion on mca doctor Two stall parts of the prot, bos desesibed blow ‘fe conimng as separte projects the developmsat of aplication specific integrated sires for ‘secting “thermal” (ery ow enegy) neutrons and idetlying gamma-ray spec Simlkancously, and an elfor to use nandcomposite silat material for ncuron detection,
‘The problem
Siniltor materials are used wo dete, and in some eases ent gan ras ighet=
Performance seimillas ate none expensive, harder towers at eae eto tat te escort alate, and more rages oller hee péformance Asse: cathe sirable qualities cach ype be comnned to aehicvs heise perormnce a ower Cost?
Background,
Scioto are materials that, hen struck by photons of higher energy, sue as gana ey, ‘spane this enemy apd release eas pons of lower enetsy usally vibe lig The meri Should capeare as mụch o he energy ofeach photon striking it as posible in oer to bull an
sccuate photon energy spestum and this idea the mateialemtng the photons Welly, a photon shoal dopo ful energy in the seinillatr material «scaled al nergy
Feteraction Isao important ha the dept chee be elicit env into photons of ‘sible ih, which ate ten csc to deters enc
Thee are two main types of similar, Inga scinillators hose not containing carbon) are Iypiclly sine cet, sch sso inde (Nal witha stal anwount of clin aed The rofl of fll enray nerasion increases sharply with amie ier (2) of the sina Inara and is high fr inorganic crystals, The mote emery fom each photon ä sznNatu ahsotbs and then gives of, te beter the coreationbetvcen energy input an caput and the ‘more pre dhe spoctrum hat ca be construc A3 esl, a device Using at inrgatie cyst has a good ability to identify the eaiactve material producing a gana spectrum Teze are scveral drawbacks, The asa ofa detector thi sensitive to panna rays small (Lind othe Stee oa crystal, so the deertor ast be close tothe object to he seared or mst sca fot longer ting sn it can recive more gama rays, They at frais; droping one can lesiay i ‘Many ionsinic crystals absorh water a are sensitive t igh, so they mst be protected from
enviromental conttions, Nal crystals ae easy to grow, bu cost about S3pereubie centimeter ce) of erystal Other, higher resolution seins ate harder to grow, are mae ests, A ate Snsiive to svistre For Na ight output varies stongly with semperatne, so he temperatre Inst be sabze othe dita Corete
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tn of Nuclear Weapons and Natrae:Sienr, ecologies, Oseeatons ‘Onzarie seniors have the egposie st of properties They ean be mae of psi, seh as VT As sch they are easy aa cheap to make, and are much les fragile than crystals They ean ‘he produce in bulk making them sultabefor deployment in large sheets, such 35 fr sadiation posal monitors On the ther hun since they are commpsed rnsty of hydrogen an carbon, best
Ney ke Z clement they ate very inelficient at absorbing he total neta of gana ays As 8 resi as Figure 3 shots pak in PVTepredaced panama ray spectra te inti tbe
making such spectra of litle or no vale To ei ying enosetop,
Technology description
“Aesearch project under way at Los Alamos National Labortoy, the Nanocomposite Seinilator Project, seks to combine the advantages of both tyes of sitar materials overcome the slstdvartages of cach The principle is that “nanocrystals.” erystas 2 to § nanometers in diameter {UP namneter =| billionth a «meter of certain ofthe energy from photons, thus ofering ney the petocnce of single large estas if inorganic silver materials cạtcapttre mat
eke dorsely ens in psi, The sung mintteaso asthe dsieble fates of pase ‘The cxystals ae ann oid mised with ero, ot cen bromide The made polystyrene plas is a eller materia ov increases the enw of energy comvcrtedto a deectble signa
tn operation, when a gamma-ray photon strikes this materi ts energy is absorbed by runserystal and the plist raising some aloms tou higher energy evel These wows give olf this energy as phone in the wsile and ae sie repons ofthe electromagnetic specrm ‘optical pts") Aphotolectr, an electronic component that gencrates many eletrns hr
cach photon it recives amplifies the signal and convert frown an optical signa oa cletaic Signal hat ean De eanie The her af opel pins peneated coresponc 0 the eer) level of the photon stiking the material Arat-chanaelanayecr count he optical photons, “dserminss the eeray level ofthe pn skin the maria increases the exh of pons
‘tar charg Level by one, by this proces teding s giưnnn-ray Jeetum
award MeKigaes, the principal investigator, eleves thas aanocompanite enilaor materi willbe able wocsetiminate beeen telfus and gama nays, He set tát im lvdos Suppor this case The projet has obtain ata foun expeinens sig the plastic without runserystas and nanoerstas without the pst, an rom the crate, and as ul hese date insinuations Base physisealelations also suppor this case Neutors poncrate patos when Thy se hệ pha, an gamma rays generate electrons The plastic sponds differed to rons adn sloetons the same is re ofthe nanocrystals However, of August 2008 the Proje fad not condi experinentsdesonstaing the ability ofthe merit dese autos ado diffremiate herwecn them an gamma 9s,
Potential advantages
MeKigney suites that because key are in owing tems ot dificult ad is mc ess ‘xsl than growing large whe crystals of these raters The material esti wal, he say, fvter rec cot, He estimates at hi material potentially oles can be fabricate at |
the performance of $30/ce material eg, lananan bromide) as erst of 80) cee Becaise ‘heater aes 96a psi, ts mgd aa es, al ean be mae ange shoes acsoning to Mekigney increasing the semiiiy of detector using i I would pets at anion lenperlafes
Trang 23
tn of Nuclear Weapons and Natrae:Sienr, ecologies, Oseeatons Status, schedule, and funding,
The prujet has several componcas The lrg! it develop manvcompitesciillstor masa Ther are several spaller components: proves sleeker tones develope; deter lesan base research fr me vances materi The hadest forthe ee prec i a Follows, Esly research stated in 2008, Lo Alans provi $68,000 in intial Tim FZ
The lhoratory ann DNDO provide S.2 millon for FY20N6 and $1.6 nlion fe FY207 Los ‘mos, DNDO and DTRA provided $4.6 milion for FY2008 and ae projected to provide $3.5 tnillion fr FY2009 The projet seeks to deliver a sal ender (iach in iamater sal Lach hh) of the mera a! characterizes perforce, by December 2008, Anerpted costs ae $4 milion for FY2009 for the anocomposite calla eomponet- The gal for the end of FY2009 is to bac ái scale demonstrat of he snr mtr ant tat rarsecrng itstenolgy te indir This mstral would be opined fr gamma-ray detection, As of Fay 209, the shed To ths densostaton ad lined by 6 0 12 months,
Risks and concerns
Scientific risks and concerns
Fabrication ofthis materia egutes nding chemicals that ean oat the suriee of the
ratoceystal 0 they ean isptse properly ia the plastic while opinizing eter properties" The hunaerystals mist he packed densely fate past increase sensitivity and x*oluion Ác of May’ 2008 researchers had reached a packing lve of 6% (hy volume) ith a goal of 0% Te Femuine to he seen if they can mst the aval Packing crystals denslyin plastic wil change sone rote the pst, so care must We taken to mize this problem Ansber source of sk Í hạt as of Aut 2008, the projet fd no each high enough packing eves wo allow Tor measurement (0 decmine he sharps a eamnay peaks pct generted bị this itera The projet pas to conduct experiments on this pot by December 2008, Sul Imegsurement ae expected 0 euce scenic sk, However, unexpected nanoscale pes ‘ould impair energy fesoltion Te tha ese the patel tactze would Rave tobe egincered to initiate the effets at worst, se effects night degrade performance
Engineering risks and concems
Trang 24tn of Nuclear Weapons and Natrae:Sienr, ecologies, Oseeatons ad cereal engineering solutions have been inplemented for decades A concerns whether 3 Solution can he devised for pt seale production
Cost and schedule risks and concerns
“The pmjct soc mature enh to provide firm etimate ofthe cost ofthe material pode ‘oman insti scle The cost esinate etd aon is based onthe cox of procurina the ra Imaceras nd assumes ha the ener cost for processing is low Inlaton it enemy woul bot be
‘expected 0 inrease cost shal ut east of the pci sensitive to the cost of cerium 3 are tah clement, The manufacturing processes are pro the usod for such consumes good as Fahri softeners and dsposable plastic water tes, s nit est argualy shoal met he ih, However the cos estinte exces the cost of tne infrastrctus: bow that wld ako unit cost depends on inrastcture cost athe aber of units prodced Transfersing the technology toa commer parts bythe end of FY 2009 depends on sung tia Scien sid engingring problems ina timely manner and tine the ht partner The peje isnot far enh long to bske frm estimate of sale bayeml PY2019,
Operational risks and concerns
In any project is posible vo devel aprotic omy to have i fail in everyday use This projet is crying to mininize this sk eis eying to design robustness into the mati seh as by (1) sing psi at so aa aber rahe dat its, (2) ens tha Ue material Wl Be effete eros he temperate ange to shih wil he exposed sad (3) ensuring tht the ‘kext and packaging are compat so hat, for example, the detector aera} wil 9 expand Somueh as 0 crak its easing
Potential gains by increased funding
Tis pj's otal budget is shout 855 lion pe year MeKigney states that he could “esefully employ 3 tsa badge of up Wo S12Misear co tabs the tine to deploy men af these Teehnoloses” inseveral ways 1) The projets rs, with about one hind ois tra Tending, a separate Tse teseatch po to develop in) tr nhfeflappyoaehids the eoluôon of Bh pity sermaniam detec wih the eos ad pressing caraersies of pasie, More fr cule secelerate this proj, according to MeKigney He cautions tat his project mht take a decade ‘or mre and has mmc greater scenic sk tha i cure nanocomposite snl root {2)"The project uses equipment available at Los Alums, hut esas that staf could save ime if they ha their os cpa" (3) ‘em sie by 20 em tick by 9m he) of eestor mae Forte pel seymente ens It would be eile fabricate single age panel (e880
Trang 25tn of Nuclear Weapons and Natrae:Sienr, ecologies, Oseeatons chip and se scinslaor material concurrently, ving time Recognizing this leverage, BTR provided about $150.00 for this purpose spread over 2° years beginning ip May 2008 MeKigney states tat aditons funding would accelerate this schedule 1) Hiring more chemists elctcal enginoors, and hers would accelerate these poojoss, acon Mega,
Potential synergisms and related applications
(1) This material fers the greatest heft in tector tha use large panels of sniator nutri, suchas some under developmet as discussed Pelow: (2) By offering greater sexsi and greater resolution, this material could provide beer data for algritis to process, Pesmitting the development of simpler, mere capable algorithms (3) Nanocompesit scimiltor materia mye ale to measure neutron and gama ray energies As sue tight he possible to gs ina detection spate send separate nears of dteting ac patie ype) Some “onipanis ate considering syste ha vse bes ill with ele 3 eas ode? Neos, However elim i seas, au thee may not he erg to supp lggeseae use of these
Tubes, Namcompesite senior materi rig bệ an aleelit for neato desi,
GADRAS: A Gamma-Ray Spectrum Analysis Application Using Multiple Algorithms?
‘The problem
{ns eal coool laboratory envinynmant, «raison can be wedi deni by itching is gamma ray spetram wo one ina Ubrary of specs Ata porto border exosing & spstrum would he complies by ration foi many soures an by atenuation caused by ‘arp and her tera At ss: How ean he signal from SNM he carats fons sani
Fay spot, an how can this capability bem?
Background
[Nuclear detection haravate receives much tesion hs da fom the hardware, poles of ‘aogs crepes fom gammu rare uninelisile unl proceso hy software nces, Software inthe ươm algo ete "rains ofa tet An algontn,such sa computer Prosram, isa finite st of logical steps for soving a problem For mice deco ap algo Ist process da in sable forman fst enough io he of use to an oper
Trang 26tn of Nuclear Weapons and Natrae:Sienr, ecologies, Oseeatons algorithm, Gana ys Jose energy’ they iteraetwih mater,erng their spect depending ‘oaths type and thiskss ofthe musta they pass through, add inal enerey of «gama Tay, Ramlom fidtustions in the ramber of cous n cach ganvne-ray cnerey hin crate statistical
teri, especially if the nomhr of counts sf The composition ad thickness of mater tect the radiation ster and the det (car, shicldne, enka wall, st te.) isnot known The esations may nol exactly represent he detector dimensions oe shielding ‘configuration hecase approximations ate nee oFdice complex environments 8 set of fxgatons that eap be more ely compute
Technology description
‘Dean Mitchell of Sandia Naina Lahortoris hs develope en applications package, “Gamma Detector Response and rayss Software,” of GADRAS.”" Devens of GADRAS start in 088 for ane nthe Rese Atnspherte Menioring Paaject (RAMP), whic ws low esoavon sectors analyze one raioniides.* Begining i 1996, auomatedisofope dewfeuion ‘was developed within GADRAS to process spetroscopic data llc land cosines ta Suppor insertion of ratinctive materias.” Work onthe current version of GADRAS state in 2001 Inearle versions it Was Seen a acceptable fo spend a month analyzing an individual Spsctrunt inthe wae of 9/1, nord ob of vale for sreeing enmnaerce GADRAS hid to ho mic to proces data quickly while minimizing fale positives sn ake negatives As of April 2010, the GADRAS application inked si raat sms algoflhm, em yard sion detector response lietions, sl sport for adatom inept caetions
To idemify radioactive surees creating a gamma-ray speetrar GADRAS mutchss an extre it ray sec against one or mone wn spc, Figure 6 ilistats this approach, Many “he algo facas on pts in pana Fay poeta oeause they ae the ost obs Keates, In cont, GADIRAS analy the Fl pociut or several reasons, (1) Peaks ay op,
‘making soutes kent anbigdous.(2) Most counts n3 gan ray actum at pRe ‘outside the peaks, in ich ase using wey peak data Would ignore mest of the data For ‘evample, ess than 3 ofthe cousin 2 spectrum For U-238 occur inthe 1.01 MEV peak, the ‘ost posinent feature ofits svt (3) Couns ous the psaks lp characterize the “competion and thickness of intervening material, Since gai rap tract wih these tater, cracsrizna the materials nmves the accuracy wih which the ganma-tay
Spectrum as real hy a elector can he inked back othe gain-ay scarce Avnet a olin ‘sites witha te data increases confine inthe res) The absence of eons na region ofa spactamy Spectrum lps analyze data fom scinlsiors having low energy resoiton because low ean he lve athe identity of radioactive materials 5) Using the enite
Trang 27Datetion of Nutcar Ws Figure 6 How GADRAS Identifies Special Nuclear Material "= Background wu a5 Courts keV Energy keV)
Source Fig Den Meal Sis Nstoral abortanes Api 200
"Nota: Thi ere shows Now GADRAS cin iy vari tr et on) dpe cara Fate Th bt se shows grey erin hue tro aks ea ee ee ơn ‘abe gua core ch a lar Ba tr per ele ren Fw Sot Saas pre gran ee even herein) Oona
(Bronte eenean gn ras pub Stree eters 9200 grea om one soba i een toa OLN ges foe meth neared tacked ode mự hữa vay Fests rams mater frre A count genara msg aeaar mp adie so he
[GADRAS ania the etre per to terine nich combiaon mtr ight produit thi ‘rang GAORA tà rr frcoran rae tn) nd rome Genres oom ‘em backround dion en top anh Te ky poet aces th respec pes a at tore scant nhc maar natin a wel aang yy ese TT nơ he mod nệm pearum sede po or mange rea E fea ot Ta on aur crys ey ai art hero gry secrun P an 9 pth
ty an seramule eran eat ene er
‘GADRAS also uses neutron fx data Since neurons pass more readily through high material and gamma rays pass more readily though low-7 material differen materia, such as in a ‘container, will et the toa aiacon output diferely Asa result using bath gama ray and reason data inproves the analysis
‘GADRAS fas heen in use since 1986, Since 9/1, more operators have use iin wider range of applications In esponse, the softwares continuly upgraded to suppor new types of Faiation| Serors, provide new capabilities, an meet new performance requirements According 0
Mitchel, “One of the new features isthe aby (0 suppor the analysis of data tha i eollected ‘ith retron muipiity counters, This capability enables inclusion al ofthe data elected hy
Trang 28tn of Nuclear Weapons and Natrae:Sienr, ecologies, Oseeatons samow-ray detectors sml da types of neutron detectors at a uni analysis algorithm "” ‘npn i fo mutke GADRAS moge automate o that less sil err to operate Another oa to ake it fase Acurent lft oetkes on mgtevin sensi to SNM and rec the false alarm rts, Inthe past, some sacrifices were nade to fidelity of he analysis inom toi tin sped no, wi scr computers, t should Be posse to improve the analyse while tncresine spook his approach is eine invetiated, Another apprach io rec Fe ales isto examine ration sensor daa collect i 2005 on ers ene the Liteon Tunnel between New York City and Nev Jersey Acooing to Mitchel the dts included 50 to 60 false ala “Mitchel snd thor vsearchers at Sau aze trying to determine what eased the false alarms i ‘order 1 my GADRAS to corect or these problems.”
The nin application of GADRAS isto support “ThageReachbach” analysis Aeatation ict operator nthe il, sch asx Customs ax Borde Protection (CTP) oer, nds a vehile o cargo conaier tat presents a suspicious raation signature tht cannot be exsily
esol, can send the detection data (wuch as agama ray specu) to de Laboratories and Scientific Services section of CBP fora mre cetaiel analyss” That analysis sss GADRAS, Sin that service is wl to resale the mate, cụt sen the ata Wo 8 secon Reachack al the mleat weapons Iboraores, which aso se GADRAS,
Potential advantages
‘By analyzing a complete gamma ray spectrum GADRAS increases the accuracy of determining ether a ergo container or her team scaring SNM edcing the Hsk of fle positives as False negatives, Using nto count data ination to gam ray spt her proves cap,
Status, schedule, and funding
‘GADRAS has heen used for caro inspection snes 1998, Software upgrades are release every two months of Theres ao ine om for GADRAS development Mitchel estimates that Sands spending perhaps $610,000 in FY2010 t conti to develop GADRAS, DTRA state in 2008, "Te DURA in concent with NNSA is cotrenty proposing development of the tet fsneration of GADRAS a pat of «potential (memoranda of undersanding] between the
‘oraanizations, The ello wold emphasize the revs alarms, pda to Visa compliant Sovttre and inetesing portability fr Feld se
Flair cn spp asics du semlcn pcg an fsenog nro ets, inh cout
> fr fe normain ee US DeprmHanSseiy, Csi rds Pron “La
Trang 29
tn of Nuclear Weapons and Natrae:Sienr, ecologies, Oseeatons Risks and concerns
Scientific risks and concerns
Since uparaes are ongoing, developers fae sue scientific problems as hw improve sation: to characterize the response ofdetovtr enti t raaton, Sh problens are mt a Imajr sk to coninoed developmen of GADRAS Michell states, Another risks hat the isin fom shielded HEU may’ s ow that even ohh quay algor cannot identi the HEU
Engineering risks and concerns
‘The major risk to GADRAS development comes frm the progromming language thats used for the raphicl use intrface (GUD, Te GUL To the curent version of GADRAS swan in “Micros language called Vsval Basic Version (V0), V6 functions under cvernt version of Window, including the most rvent, Vista, Mito Gowever, no anger tans VES, s0 ts rot necessary compatible with new compilers” often leaving sơ efecixe psrdde ph ly hệt !nplication prope like GADRAS, User Teabackindeats that some GADRAAS eomponcns ‘Snot Fueton peoperly in Vista, While minor changes may resolve de lter problem the tment GUT may oe fun under a ate version of Windows, GADRAS is lage program, aad
arent ning does nec support he efor that woul be eutel Zo uate
Cost and schedule risks and concerns
Since upersting GADRAS is low Feqiremenis impose signet schedule aks, However it wollte oe Nn Years ese seii9 Lenai is at sk, No nearer the GUL Making this resision in avanos ofa eange of operating stems wkd enable users Uo tse GADRAS without iteription when they site to dhe ne operating system,
Operational risks and concems
Trang 30ton of Nuclear Weapons and Materia Sin, Tecnologie, Obsrations Potential gains by increased funding
‘Mitel sas tat paps S400.000 a year fortwo years woul allow Sandia thir a ow Programmers who eal conver! GADRAS use caren compilers res aod ote ruption associa ith new cperaing syste, A elite ask i documentation of the Application Programs Inerice Ths dvtmaton woul eaale other ser, sich a8 eter
laborstores, 10 develop new apolieatons hat ean access capabilites tht ate isonet he Dyrnaone Link Library, whit performs mst of the computations in GADRAS This increase sccess would eve the eos al developmen ie fer ne appieatons
Potential synergisms and related applications
LU) GADRAS might improve te performance of scons tha thie Fsson and dete he resting ition 2) By gaining mute information fom the gan Fay stron might Fede the gain aye ton Mux eee ofa Tsion aa the dose reli fom ssi, thezehy increasing worker safety (3} More computation posse would permit re sophisticated trations of GADRAS to be desclopes or would pert GADRAS to rn fst oth (1 tacreaseel computation power, especial smaller and ore capable computers mish enable GADRAS to he modified fr usein the fel wih radon detection equpmnett, periting quicker reson of sspilous containers ad wshicls, Reachhack woul ea be sod only fr the hardest to resolve cass (5) GADRAS cold be mie to prove te Terformince of radioisotope ideliticaion devices (RID), DTRA sates tht itis corny nang development ofa mote patable version of GADRAS hat ede be veside on ‘ofan RIED systems, sch as findhell HPGe system proce by Ore." 46) Inprove Sciellatr atrial an he expected o provide beter daa inputs to GADRAS, enabling &
Further reduction in false negatives and false positives Universities, companies, and povernent laborstris are working to develop nach materi, Computer Modeling to Evaluate Detection Capability** ‘The problem
Developing equipment a detect eros clear weapons anal SNM rages many choices, ‘would be of gret value to evaluate bow they affect cot and performance before cmt a & System However, many combinations antes are possible, and would be probity expensive and time-consuming to run enough tals foreach to make valid comparison amg
thom Whe faced with dimiar choices, such asin dsigning& ca, conpratons typically an hoe nambers of sinter sing compoter mel ha ake signa invest Tà ddevelp Incl adetrs, and what ares ations? and raisin Asse: Haws ean computer modeling conte ta the development of
Trang 31
Datetion of Nutcar Ws Sconce, Tectloges, Obsereations
Background
‘Adetectr should maximize the probability of detecting an actal treat (a tue postive) while ‘minimizing the probability of detecting «nonexistent threat (a fae alarm, o false ‘given technology these chjctives cannot be achieved sinulansously—an improvement in positive), Por
Trang 32Datetion of Nutcar Ws
Figure 8 shows toe ROC curves illustate several concep (1) Mosing fom eure Ato ‘eve B to curve C shows te performance ofa hypothetical detector improving overtime, Perhaps a a diferent detctor materials use or an algorithm s moified The improvement an
he visualized by moving upwanl line 1), which shows an increase in the tue positive rate for a sven fae positive rate, oF hy moving fom ight 4 lt (line 2, hich shows False positive ate for a piven te positive rae, (A diagonal ine from lower right to upper elt a retin nthe
‘would shose improvement in both.) (2) A,B, and C could represent differences in petormanee of ‘one detector ‘onditons (eg Scan ime), diferent henign materials in a container (3) The eurves could use diferent conditions seh as ehanges in the background, differen operating
‘characterize the performance ofthc competing detectors Note that actual ROC curves have ‘more complex shapes than the notional curves shown, They may even cross over cach ther, indicating that onc option isnot uniformly beter than another requiring consideration of further trad Figure 8.Three Notional ROC Curves — c7 TT | line 1 08 “ “
Probability of false postive or fase alarm Sourc Prard by CRS wih he autres of Lawrence Unters Nand abort Tne Probability of true postive or detection
“Many variables affect detector performance Some are operation, such as scan tim, the ‘decector's target (container, cars tricks, tans), the distance between dtcetor an ‘environmental condition (sekground radiation, season, temperature), The detector i to detest target, and
Trang 33tn of Nuclear Weapons and Natrae:Sienr, ecologies, Oseeatons “encounter” 1 would be prbiiively expensive and time-consuming to ran many encounters for cach of thousand of combination of contllale variables but wou! eof seat vale Yo have the esuling data inode 0 compare, improve or choose hetween detection systems and thet ‘components
‘Computer modeing can elp Modeling eeates rthenatical representations of the real sol ‘ares the inputs, apd caleulites the outputs ln de case of racleae detection, the real weed Consists of controllable variables peraionl scenario dsteto, a slgorithm) ‘aan (signals fom radioactive materi, The performance ofa mrdeled detector ean be a ncontlled
istrated using ROC cures as described shove, Runnin the model to sintlate many enews foreach combination of controllable variables provides enotgh observation pois to generate @ staisicalysiemficamt ROC curv, This proses ic repeat for many combinations of variables, The resulting data sow the user hw eget vanable aff perTornanc,an pernil comparing one detector aginst anther Computer generated “dst” for miclear detection xcuters ate allay’ inperfet, as dscussodhelow As a result, the adegaaey wih which the ml represent reaby alwsyaf sus and mie! developers deve are lor 4 improv thar rpeesettion
“Moding can also he use to evaluate requirments for elements ofa detection system Foe example, mel was used oad te sexta selon (se Priepes detection” above) Fete of # detector material odstngus the gammy spectra of treat sources rom mon twat sources, Aevortig toa repr cn this projet, “Ti cape the Fang 0 gata sures ah shilling configurations found in commerce, we generated simulated potatos of 18) oF more spt each with 3M energy channels Cle it would have Deo eostly al ime ‘onsuiing 4 generat the data experimental
‘Technology description
DDO hs cstablished an ongoing pogran, Detestion Mdsling and Operational Analysis {DMOAS, ha the national laboratories std ive setor contort oe Dk mes that characterize the yvibles nated ahve, te, the operational sear, the radon sigs, the ‘kev ad the signal processing algoritm, Creating mathematical representations ofthe St thre aes an immense amouat of work becuase each i 3 complex Alemative algorithms ate Sinated as par ofthe eral deeetion performance modeling Algorithm development
Feira reat deal of work, but mot within the scope af DMOA wc focuses 02
Trang 34tn of Nuclear Weapons and Natrae:Sienr, ecologies, Oseeatons ‘The model processes data onthe operational scenario, ean signals and he detector oerete a gammray specu tha seat othe ugoithn, Te algithms does aot “hoa” the đlfrenee hsswcen a spetnum generate! inte rl world or by computer and processes both nthe sme tna Since the ference she source of the dt, the ey to simliatom i generating the gamma Fay spectra (inal pis ise eos ote algo The peter the fide with which the rel mis re-send ings, de beer i represen stem performance, Mele
Peformance, as meas hy dstestion probably a fake alae rate, ean be sumiezed in @ ROC curve inthe same way as empirically measured performance The modeling effort also inlay assessing the sensitivity of detector performance to changes in operational scenarios, dksestr hardware, ant algo
(One DMOA effort in 206 foc4sed on fr san ses 9 mpwove is mode This Fort itgstrates the work undemtaken to improve the ily of sl and how his wor uss tiled knowledge ofthe components being dled
+ Bvalution benchmarks, Providing a hass for comparing systems raquires reference st threat objects an icing Provingly a st nehdal Pisoninm, HEU, and other tras, aswell as torent fvels of shikding In BW, DMOA add new threats at siskdngs to the referee et, Hale ‘Seveloped a reference se of abjets fr dơecinp by Faloerahy
‘+ Background radiation an mica souree population characterises generally dicate and susance source modeling Aeconting © DMOA, “Background cdecdom threshold sotngs wh teint om nner lar ts, ‘Charieteiation of these Fctrs ete al to evaluating the peorreance of
radon detection systems” DMO used teal world data to develop a medel of the stihasinn of rurally occuring raioetive maria Data fom the nel vere then compare wth apa set of real-woel dts to chs the ality the mode
+ Operational analysis: DMO used eal-world data to compace the performance of ever lpi One rest wast “highlight the sensi of system petonntnce co the deletion algo ase.”
+ Dsietorresolaton study DMOA sad the rslaton neds to distinguish Heats fom ther sours of ration, The alysis though preliinar, ound tac there sa beneic hy having batter resolution than ha were by son) ied, ot that improving resoltion heyonds eran pine would oer marin Ngon,
Potential advantages
‘Modeling offers adsantages compare te oainng ta fom he real wold (1) A made permis omsniction of statist significant ROC curves [ist Uns ote + Fae An fate of one ep thousand require huneds of dosands or nllions af expesimens, woul be costly and time-consoning or lower, tistical validation of performance at ths Tevel would to conduct eld ras using single combination of arable in ord to bud one stately Significant ROC cure, le lone conducting fick ti for houses of combinations of variablss
> Ths pac bse en i,
Trang 35tn of Nuclear Weapons and Natrae:Sienr, ecologies, Oseeatons ‘har represen dhe range of conditions Andel permits running many thousands of snl
{sounds i les than Inodel ss been constructed, validated an implemented the cos oF these comptes rs is very a cy to explore the ange of encounters dco my acs One the low (2) A model ana test program ae complementary The tet program generates data fo the tml and the node an ler the est prea inca what teste woul Be feral “tle for provi the predictive power othe mode (3) A madel permits exploration of {caters al mig aut in the fel world ba that eval tt be eodte eens of 0s Safiy, or oiTiculy For example, i would Bo useable w place mlear weapon ia ‘commercial trai to est detvtors, the only facies where such testing could he done, notably the Neva Test Site, have charactrsies very diffrent than those of ports or hase “rossngs As unr example mish he desirable see what &protrcta psi heat ot high humidity wold ips hay detector would function, ut would he mh easier to
replicate such conditions trough modeling (4) A model permits comparison of components ofan counter suchas which algorithm better processes the dts for a given gamma-ray specu (5) ‘inde pets alysis of alerts ae canton of tks hetore commiting 4 ‘pose dese helping inform bilinear decison
Status, schedule, and funding,
MOA is an ongoing prognim When DNDO wat established, DMOA became un explicit clement within the System Architect program has be Fae with ha peti at pituxiwalsly 32 mien pee your, THe mow Hand Hy all DDO ices oa Felted detection tmaeling son the wer of tive mes that ofthe Arshitecone program Other dtetios mneling do for other pposes by othe offices within DNDO, as well s by DOE ane DOD However, singe modeling seis af inherently eoss-cuting and support many technology development an assesinet pons is cou to estimate ol spending on eating in he (eleral hse
Risks and concerns
Scientific risks and concems
Wiite no mel can he petit, the ey isk sha the mets output er example smi ay spc thatthe mel generates) might ler significantly fom data tt would have Been ‘hand rom etal fe als Pat of this risk concer madeline the underying science, Some aspects ae knw in det, sch as the tadation spectrom of U-23S But there ate uncertaites,
HEU is ox pre U-235, so he specu ll be somewhat erent fom ha of U-238, Same shiektng canbe modeled passively sich sa centimeter of a Buc the defense the modeing <esign team) does act kao what sbielding if any the atacker might use A cargo container hokd many types of ears, cach ol which iirleres wth ration trarspon ciferenly iter ean
rangcienis of the cargo place ferent ams and typos of mera tcc sear an ‘sector affecting gamuna fay spocea Any model makes approximations and simplifications, Somsines tallow the simulans orn faster oe simply hesause more iy for eran
Trang 36tn of Nuclear Weapons and Natrae:Sienr, ecologies, Oseeatons Engineering risks and concerns
‘Models are complex mathematica approximations of lity Yet real-word ata aren limited phap covering tow narow a range of ents DMO uses statistical mets Yo transform a el-world data se nto dala frien tector tnd cantons, As DMOA report sfaes,“LUNL [Lastence Livermore National Lorton] has develped a proce foe
seer a satisial mel of a mbisatee source popution dsl on messed dal The sical nuodel developed provides a basis for sulting a walmed ruber a random Samples in msisance surees tor 3 population assed whe sini to that wnderiyine the measured data" Adc is i validating the model Various istapes case background Faation, and DMO ohserves that "heres simple stand procedure to compare ‘arate populations.“
Modis may abo manips data by ating in, of “injstng” soca fom well-charateried radtion sources lke MIEU or WGPu to computed speci oi cargo typical of normal commerce tesco how well an leo can da ưeot mati in ego, Hosver that epproch ray he aninadeguate represensation of reality tis arsubly unlikely tat teroriss would include a
hele weapon of SNM ita ram ego conainer i thy eve that vector: father, hey might rage te cago lo elp evade detection Silation develapers have ot mated sich
ehiberatearrgements of ears hoa that woul ae inking about how o made Gversary behavior, someting ouside thie experts Ing he gestae to have tetris fxperts fy some injections to reflect adversary hehavir
Cost risks and concems
‘Most fins spent on MOA are fr af salaries, 4 the tksihoo of wasoiipate cos inceaies pears lw However, this assumes at eomputing hadare raged to ra he sods gui Isley paid foe
Schedule risks and concerns
{enone plated to bring mule weap of SNM int the Unio Sates they wuld rest ry tv evade deri, ling ta a offense- dense compton I soul be ‘Sse fo his nation vo tay ahead That sk involves tnieh effort hy way ents, Foe ‘dling, dhe task wuld be to upersd means a evasion elude in the model nme say shu ofthe deat This would leper in part on apts fom ateligence services, sch asta ‘specific zat, bu also on vances in characterizing background radiation developing "gorithms, developing sastica! means of tasformingorvlting data a thee The
Trang 37ton of Nuclear Weapons and Materia Sin, Tecnologie, Obsrations Operational risks and concerns
Law enforcement and commercial intesests ee intolrat of fas alarms, The fake alarm rate ‘often dives detector sting and coe of dtction system, an increasing he trae pie rate alkoinereases the false psitive false lary rate, Whilea model can espore de tad as ‘optim balance heiseen ime a aus positive rates, ark is tha systematic eo, ncemest ‘ta tansformuios, and incomplete gectunting for background radiation would cause the nel to generate a seting tha is ess than optimal, In som eas, his problem can be overcome by
making adsense eld, but i othe eases, such sth eee of det wei gst may not be possible
Potential gains by increased funding
A presen, the DMO efforts the nation borates and private Sector comatose fstibued eughout tei oreanizatons Most staff nether who work on ifogion nediding ‘do soonly par time Sou mowing tos simulation codes, datahass, an alorthns) on 9 besomewhat inform, developed by variate groups for specific nse Acco to Richa
‘Wheeler Lead for Homeland Security Analysis, Global Sceuriy Directors, Lawrence Liseroze National Laboratory ade fupaing inthis area coal enable the designation of al time stall, development of sanardized mods ing ool, seston of dedicated computing resources, cstablahment of rigorous post review of the mks, oral coordination of eat or sponsor hy DOE, DOD, atl ber avers, and generation of ne dates essertak fo mod vlaton, Whileanalsic f detector performance agaist realistic dats sensitive ‘or classifod many advances in modeling a modsing tools could be made in an open "tvinninn, eli the academic community Wheeler sates that nace fds could sappont a
tors subst engagetnont of univer sesarchts
Potential synergisms and related applications
Silaton doesnot tet anything hy isl, huis by is nstre synergistic with thr aspects oF relat detcton tas is papas improving many element of deletion syste, whaler ployed or under developments helping to negra hrsate an sorevane into spe ‘omtimicing ssteme and CONOPS: an informing dcisons on the most cost-effective mix of sates to acguc
L-3 CAARS: A Low-Risk Dual-Energy Radiography System" ‘The problem
‘Curren ravgraphy systens have inpodtane initations in thei ity to detet SNM in care opines Sm aman of dense material my be iaconspicbous i shipped ina ertaines led with dense or raion objets SNM oul als be pla inside dense bests for
Trang 38tn of Nuclear Weapons and Natrae:Sienr, ecologies, Oseeatons ave A sae: Can raography take advantage offre chatacters of SNM to dss it in cargo? And cana system evaluate radiograpiue images automatically to reduce dependence p8 ‘operator judgment? nan effort oversone these lnitations, DNDO is comlustng RAD on advanced eaigraphy systems unser the Cargo Advanced Abtomuted Raciography System (CAARS) program CARS involves tree technical approaches to radiograph, cach with acillereetcomactor (AS noted holo DNDO termina! the contact forthe American Seienee and Engincering, In, sytem in
‘Moreh 2008.) This section athe neat css these systems tm eps a the ‘ser that these ster ate une develapet, As es, no deplable CARS sssens "xis, 9 agen ad performs spesiietons preset in thse sets must be ewe ae fost ate yet tobe demonstrated in eomynerealy available equipment Customs a Benet Protaction (CBP) raises several concerns abou CARS, as descrhod unr “operational sks and eancers" below: CBP a component ofthe Deparusent of Homsland Secu « foa-ine tgsney whose ofiers perform sch missions ts operating host erssins and imspecting cate ersering the United States a seaports, rps, an and crossings
Background,
‘Two types of commercially available equipment for seaning ego containers have been widely used sine 2002." One type, adaton portal uniter, passively detects radiation coming fom a ‘container Aner tsp, radiogsuphy equip, creates 139-4 mages of contin
{examples neue the Rapiscan Cassie Eagle un the SAIC VACIS.” This ype is mere evant {ls CAARS, Radiograiy equipment works as follows cargo containers driven betcen voi orsponents of ths equipment oF the egepment moves over a stationary conta One
Trang 39tn of Nuclear Weapons and Natrae:Sienr, ecologies, Oseeatons sisfereatebeeween ferent ype of material an eannet pik out Heats fom eater: While ‘compete maclear weapon might or might note need, detection probabil decreases as the thre objet hoor salle sot wo be elf for cute radiography systems to detet |
small picce of HELL
-Acitfcent physicat prinsple enables a radiogapty ssstem to search for materials with high ‘omic nambcr (2), Boh he L-3 and SAIC CAARS syste le íc principle, They use one ‘orto incr accelerators to generate MeV electrons an x-ray with energies fran (06 MW Anh n(he site mandp rye wth eersies fom 109 MeV ahve in this seston as
(MeV xrays and 9 MeV xray, The forme have the reaest mer of phos a stun 2 [Mes he ate, a about 8 MEV (The hed CARS stem utilizes ferent principle
Trang 40
Detection of Nuclear Weapons and Materia Szmeg Todmglogis, Olseriatone Figure 9 Dual-Energy Radiography Drug Ta ars eo HỆ
‘Source The gs ware an onary 2006 wih i SAIC proof conc bro poke ge Ingres cos VACI2: Gunn of gh Maal i Cage The VACIS2 crac vas Rca ‘he Hoplnd Sere Aarne’ Rasch Pec Ago el he parma Horalad Sau ough 2 ent presnns ONDO (ohh ws erable A 205) The cones mane &NAI7S604.C
“00, gored under Teo Spr Worn Group (FONG) Bene Agcy Arurcemere DAAD 3 Tông tre love on FAVE te hp heeceeogEed, [Note:The gap ho tre dopo thr jer: (Altrevtir: DU, epi uranan le, ‘rl unearth nowt umole evaded bares meres sve rte Psd [smn Wg HE char High wpe) The to rage at hon gba ptr ‘is sin rey of 6MV Te ie rage rows ply pa Ne rao a BV and v6 ‘ado ph Hig Zsocs re mare op to pean hears up to MeV ants tha wh Serge up 1 6V, ns plo sch bec are rapeanad marr clr The boa man show ny ‘SehghZ rte rom he mse rape wy woe ssn peers ar nan mape the re elem oes nd unpre somes ene
‘The 3 and SAIC CARS exploit this itfrence to ereae a so-called dual-energy adograph in whi each piel represents the ratio of opacity ofthat pixel to 9-MeV and 6 MeV x-rays To reat the radiograph, an algorithm assigns efferent colors to ferent ratios in the mide panel ‘ot Figure 9, het li xe ate darker, Pixels with rates above a certain vale indicate hình Z ‘material While there is no absolute psa theeshold between medium and high material,
CCAARS uses 2>72 asthe threshold for highZ material" elements with 7572 inclode tungsten, gold, lead, uranium, and platonium" Pixels of such material could be presented in separa Fadograph, as in the bottom panel of Figure 9 However these data by themselves are not,