TheComprehensiveTestBanTreaty(CTBT)
Introduction
The Comprehensive Test Ban Treaty (CTBT)isa
multilateralagreementthatprohibitstheexplosivetesting
ofnuclearweapons.TheCTBTopenedforsignatureson
September24,1996,buttheagreementisstillinthe
ratificationstage.TheUnitedStateshassigned,buthas notyetratifiedthetreaty.
TheUnitedStatesconductedtheworld’sfirstsuccessful
nuclearweaponstestonJuly16,1945.TheSovietUnion
testedtheirfirstnuclearweapononAugust29,1949. Thesetestsjump-startedadecades-
longarmsrace betweenthetwosuperpowers.Over2,000testshave
beendetectedonEarthorinEarth’satmosphere.
TheLimitedTestBanTreaty(1963),amultilateraltreaty
banningallnucleartestingexceptforunderground
(atmospheric,outerspace,andunderwater),andthe
ThresholdTestBanTreaty(1974),abilateraltreaty
betweentheUnitedStatesandSovietUnionbanning
nucleartestsof150kilotonsormore(tentimesthesizeof
theHiroshimabombing),addressedconcernsaboutthe
safetyandenvironmentalimpactofnucleartesting,and
aimedtoquellrisingtensionsbetweennuclear-armed
states.TheComprehensiveTestBanTreatyisthe
culminatingstepinbanningallexplosivenucleartesting.
OftheCTBT’s183signatories,164haveratifiedthetreaty.
TheCTBTrequiresthatall44“nuclearcapable”states
(alsoknownas“AnnexII”states)ratifythetreatybeforeit
mayenterintoforce.EightAnnexIIstateshaveyetto
ratifytheCTBT:theDemocraticPeople’sRepublicof
Korea(NorthKorea),India,andPakistanhaveneither
signednorratified,andtheUnitedStates,China,Egypt,
Iran,andIsraelhavesignedbuthaveyettoratify.The
UnitedStatesSenatefailedtoratifytheCTBTin1999with avoteof51-
48,butthelegislativebodycanstillratifythe treatyinthefuture.
TheComprehensiveTestBanTreatyOrganization(CTBTO)
PreparatoryCommission,whichwascreatedbythetreaty
andensuresitspartialimplementation,hasestablished
verificationssystemsoverthelast20yearstodetect
nuclearexplosionsanywhereintheworld.Oncethetreaty
entersintoforce,theCTBTOwillbeofficiallyestablished.
WhattheTreatyDoes
Zero-yield:TheCTBTprohibitsstatesfromexploding
nuclearmaterialregardlessofwhetherthepurposesare weapons-
relatedorpeaceful.Thetreatydoesnotincludea
technicalexplanationofactivitiesthatareallowedornot
allowed,effectivelybanningallexplosivenuclearactivity.
Thetreatybecomeslegallybindingwhenitentersinto force–
whichrequiresall44“nuclearcapable”statesto signandratifytheagreement.
TheInternationalMonitoringSystem(IMS):TheCTBT
establishesaglobalsystemofmonitorsdesignedto
detectnuclearexplosions.TheCTBTOisconfidentthat
“theirsystemcandetectandidentifyanymilitarilyrelevant
nucleartestanywhereontheplanet.”TheIMSisexplained indetailbelow.
EnvironmentalImpact:Theexplosivetestingofnuclear
weaponsreleasesradioactiveparticles(nuclearfallout),
whichcausecelldamageinlivingorganisms.Whilethe
banonatmospherictestinglimitedtheimpactofsome short-
livedradioactivematerials,largeamountsofother
harmfulmaterialswerereleasedunderground.The
ratificationoftheCTBTwouldprovidelegalprotections
againstfurtherdamagetotheenvironmentandhumanity bynucleartesting.
TheComprehensiveTestBanTreatyOrganization
(CTBTO):TheCTBTOPreparatoryCommissionisbasedin
Vienna.Theorganizationpromotestheratificationofthe
treaty,andimplementstheverificationregime(seebelow)
sothatitisfullyoperationalwhenthetreatyentersinto force.
Verification
TheInternationalMonitoringSystem
TheIMSfeaturesanetworkof337monitoringfacilities
andusesfourtypesofmonitoringmechanismstodetect
possiblenuclearexplosionsglobally.Thedatacollectedat
monitoringstationsinvariouscountriesaroundtheworld
issenttotheInternationalDataCenterattheCTBTO
PreparatoryCommissionheadquartersinVienna,whereit
isprocessedandsenttomemberstates.TheIMSis90% operationaltoday.
Seismic:50primaryand120auxiliarystationsdetect
shockwavesintheearth.Thesestationsprimarilypickup
dataonearthquakes,buttheyalsodetectman-made explosions.
Hydroacoustic:11stationsdetectsoundwavesinthe
oceans.Thesoundwavesfromnucleardetonationscan traveldeepunderwater.
Infrasound:Nuclearexplosionsemitultra-lowfrequency
soundwavesthatareinaudibletothehumanear.60 infrasoundstationsdetectthesesoundwaves.
Radionuclide:80stationsdetectradioactiveparticlesin
theatmosphere.40ofthesestationsdetectnoblegases,
whichcanbetterconfirmwhetheradetonationwas
nuclear.Thereare16supportiveradionuclidelaboratories.
On-SiteInspections
On-siteinspectionsareconductedattherequestofa
StatePartytotheCTBT.Therequestmustbeapproved
by30oftheExecutiveCouncil’s51members.Theparty
beinginspectedcannotrefuseaccesstoasuspectedsite.
Theinspectionteammustarrivewithinsixdaysofa
requestbeingfiled,andareportissubmittedwithin25 daysoftherequest’sapproval.
