The Comprehensive Nuclear-Test-Ban Treaty Organization (CTBTO) is an
international organization
An international organization, also known as an intergovernmental organization or an international institution, is an organization that is established by a treaty or other type of instrument governed by international law and possesses its own le ...
that will be established upon the entry into force of the
Comprehensive Nuclear-Test-Ban Treaty
The Comprehensive Nuclear-Test-Ban Treaty (CTBT) is a multilateral treaty to ban nuclear weapons test explosions and any other nuclear explosions, for both civilian and military purposes, in all environments. It was adopted by the United Nati ...
, a Convention that outlaws nuclear test explosions. Its seat will be in
Vienna
Vienna ( ; ; ) is the capital city, capital, List of largest cities in Austria, most populous city, and one of Federal states of Austria, nine federal states of Austria. It is Austria's primate city, with just over two million inhabitants. ...
, Austria. The organization will be tasked with verifying the ban on
nuclear tests
Nuclear weapons tests are experiments carried out to determine the performance of nuclear weapons and the effects of Nuclear explosion, their explosion. Nuclear testing is a sensitive political issue. Governments have often performed tests to si ...
and will operate therefore a worldwide monitoring system and may conduct on-site inspections.
The Preparatory Commission for the CTBTO, and its Provisional Technical Secretariat, were established in 1997 and are headquartered in Vienna, Austria.
Status
The
Comprehensive Nuclear-Test-Ban Treaty
The Comprehensive Nuclear-Test-Ban Treaty (CTBT) is a multilateral treaty to ban nuclear weapons test explosions and any other nuclear explosions, for both civilian and military purposes, in all environments. It was adopted by the United Nati ...
will
enter into force 180 days after the Treaty has been
ratified
Ratification is a principal's legal confirmation of an act of its agent. In international law, ratification is the process by which a state declares its consent to be bound to a treaty. In the case of bilateral treaties, ratification is usuall ...
by 44 States, listed in Annex 2 of the Treaty, which were designated to have a nuclear reactor or at least some advanced level of nuclear technology. As of November 2023, 41 of these Annex 2 states have signed the treaty and 35 have ratified.
India
India, officially the Republic of India, is a country in South Asia. It is the List of countries and dependencies by area, seventh-largest country by area; the List of countries by population (United Nations), most populous country since ...
,
North Korea
North Korea, officially the Democratic People's Republic of Korea (DPRK), is a country in East Asia. It constitutes the northern half of the Korea, Korean Peninsula and borders China and Russia to the north at the Yalu River, Yalu (Amnok) an ...
and
Pakistan
Pakistan, officially the Islamic Republic of Pakistan, is a country in South Asia. It is the List of countries and dependencies by population, fifth-most populous country, with a population of over 241.5 million, having the Islam by country# ...
have not signed or ratified the treaty;
China
China, officially the People's Republic of China (PRC), is a country in East Asia. With population of China, a population exceeding 1.4 billion, it is the list of countries by population (United Nations), second-most populous country after ...
,
Egypt
Egypt ( , ), officially the Arab Republic of Egypt, is a country spanning the Northeast Africa, northeast corner of Africa and Western Asia, southwest corner of Asia via the Sinai Peninsula. It is bordered by the Mediterranean Sea to northe ...
,
Iran
Iran, officially the Islamic Republic of Iran (IRI) and also known as Persia, is a country in West Asia. It borders Iraq to the west, Turkey, Azerbaijan, and Armenia to the northwest, the Caspian Sea to the north, Turkmenistan to the nort ...
,
Israel
Israel, officially the State of Israel, is a country in West Asia. It Borders of Israel, shares borders with Lebanon to the north, Syria to the north-east, Jordan to the east, Egypt to the south-west, and the Mediterranean Sea to the west. Isr ...
and the
United States
The United States of America (USA), also known as the United States (U.S.) or America, is a country primarily located in North America. It is a federal republic of 50 U.S. state, states and a federal capital district, Washington, D.C. The 48 ...
have signed but have not ratified; while
Russia
Russia, or the Russian Federation, is a country spanning Eastern Europe and North Asia. It is the list of countries and dependencies by area, largest country in the world, and extends across Time in Russia, eleven time zones, sharing Borders ...
signed and ratified the treaty but subsequently withdrew its ratification prior to its entry into force.
The organization's scientific reporting claims 2.4 million persons will eventually die from cancers developed as a result of atmospheric atomic tests conducted between 1945 and 1980.
Preparatory Commission
The Preparatory Commission was established in 1997 and is tasked with making preparations for effective implementation of the Treaty, in particular by establishing its verification regime. The main task is establishing and provisionally operating the 337-facility International Monitoring System (IMS), including its International Data Centre (IDC) and Global Communications Infrastructure (GCI). The Commission is tasked also with the development of operational manuals, including a manual to guide conduct of on-site inspections.
International Monitoring System (IMS) and Communications infrastructure

The IMS, when completed, will consist of
*50 primary and 120 auxiliary
seismic
Seismology (; from Ancient Greek σεισμός (''seismós'') meaning "earthquake" and -λογία (''-logía'') meaning "study of") is the scientific study of earthquakes (or generally, quakes) and the generation and propagation of elastic ...
monitoring stations.
*11 hydro-acoustic stations detecting acoustic waves in the oceans.
*60
infra-sound stations using
microbarographs (acoustic pressure sensors) to detect very low-frequency sound waves.
*80
radionuclide
A radionuclide (radioactive nuclide, radioisotope or radioactive isotope) is a nuclide that has excess numbers of either neutrons or protons, giving it excess nuclear energy, and making it unstable. This excess energy can be used in one of three ...
stations using air samplers to detect radioactive particles released from atmospheric explosions and/or vented from underground or under-water explosions.
*16 radionuclide laboratories for analysis of samples from the radionuclide stations.
Data from all stations are transmitted to the CTBTO International Data Centre (IDC) in Vienna through a global private data network known as GCI, which is largely based on
satellite
A satellite or an artificial satellite is an object, typically a spacecraft, placed into orbit around a celestial body. They have a variety of uses, including communication relay, weather forecasting, navigation ( GPS), broadcasting, scient ...
(
VSAT
A very-small-aperture terminal (VSAT) is a two-way satellite ground station with a satellite dish, dish antenna that is smaller than 3.8 meters. The majority of VSAT antennas range from 75 cm to 1.2 m. Bit rates, in most cases, range from 4 ...
) links.
States Parties will have equal and direct access to all IMS data, raw or processed, for verification as well as civilian uses.
The Preparatory Commission has started the building and verification of the system of which about 90% was operational.
Consultation and Clarification (C&C)
States Parties to the Treaty are encouraged to conduct a Consultation and Clarification process (C&C) before requesting an on-site inspection. The state that has concerns about an ambiguous event should, whenever possible, make any effort to clarify it through consultations with the state in whose territory this event occurred, either directly or through the Organization.
On Site Inspection (OSI)
If an event detected by the IMS (or by other means) raises concerns about violation of the basic obligations of the CTBT, an OSI may be conducted to clarify whether a nuclear explosion has taken place. Such an inspection could take place only after entry into force of the Treaty, and would require agreement by at least 30 of the 51 members of the CTBTO's Executive Council. An inspection area of up to 1000 square kilometres would be searched by a team of inspectors (up to 40). Only State Parties to the Treaty may submit a request for an OSI.
When conducting an OSI, a number of detection techniques can be used. These techniques include position finding, visual observation, passive seismic measurements and radioactivity measurements including gamma radiation and radioactive noble gases such as
argon-37
Argon (Ar) has 26 known isotopes, from Ar to Ar, of which three are stable (Ar, Ar, and Ar). On Earth, Ar makes up 99.6% of natural argon. The longest-lived radioactive isotopes are Ar with a half-life of 268 years, Ar with a half-life of 32.9 ye ...
and
isotopes of xenon
Naturally occurring xenon (54Xe) consists of seven stable isotopes and two very long-lived isotopes. Double electron capture has been observed in 124Xe (half-life ) and double beta decay in 136Xe (half-life ), which are among the longest measured ...
for an initial period of up to 25 days. Further, for a continuation period of up to 60 days, more intrusive measurements can be used on-site including active and resonance seismic measurements as well as
ground penetrating radar
Ground-penetrating radar (GPR) is a geophysical method that uses radar pulses to image the subsurface. It is a non-intrusive method of surveying the sub-surface to investigate underground utilities such as concrete, asphalt, metals, pipes, cables ...
, gravity, and electric and magnetic field mappings. Argon-37 field measurement is a unique technology specially developed for the purpose of OSI. Drilling to obtain radioactive samples from a suspected underground explosion site is also allowed. Data collected from various methods have to be fused and interpreted for decision making purposes. An important task of the CTBTO is to explore how recent scientific and technical advances in these technologies can be applied to an OSI.
Confidence-building measures
In addition to the IMS, C&C and OSI, the verification regime of the CTBT includes also the fourth element of Confidence-Building Measures. This requires States Parties to the treaty to notify the Organization, if possible in advance, of any chemical explosion using 300 tonnes or greater of
TNT-equivalent blasting material to be detonated. This is required in order to contribute to the timely resolution of any compliance concerns and to assist in the calibration of IMS stations.
See also
*
Global Security Institute
The Global Security Institute (GSI) is a largely private (though partly bipartisan), non-governmental international organization with a mission to eliminate nuclear weapons through international cooperation and security. It aims to influence nati ...
References
External links
* {{Official website, https://www.ctbto.org/
Intergovernmental organizations established by treaty
Comprehensive Nuclear-Test-Ban Treaty
International organisations based in Austria