Frequently Asked Questions (FAQs)
Nuclear weapons tests are experiments carried out to determine nuclear weapons' effectiveness, yield, and explosive capability. Banning nuclear testing will prevent the development of nuclear weapons by countries that do not currently have them, upgrades to current nuclear arsenals or the creation of new, more advanced generations of nuclear weapons.
There are four different types of nuclear tests: (1) atmospheric tests; (2) underground tests; (3) upper atmospheric tests; and (4) underwater tests. Atmospheric testing is the process of testing a nuclear weapon in or above the atmosphere. Underground testing refers to when nuclear explosions are detonated at various levels under the Earth’s surface. Upper atmospheric testing is when a nuclear weapons test or explosion is conducted at altitudes above 30 kilometres within the Earth’s atmosphere. Underwater testing is when a nuclear test or explosion occurs underwater or close to the surface.
The “Manhattan Project” began as a small research programme in 1939. The World War II project was transferred to the authority of the United States Army and operated from 1941 to 1946.
The scientific research was directed by American physicist J. Robert Oppenheimer who was credited with developing the world’s first atomic bomb. Eventually, the Manhattan Project employed more than 130,000 people and cost nearly US$ 2 billion (equivalent to US$ 32 billion in 2022). It maintained control over the United States’ weapons production until formation of the U.S. Atomic Energy Commission in January 1947.
The Nevada Test Site in the United States was the site of the largest number of tests (over 900), followed by Semipalatinsk, Kazakhstan in the USSR with over 450 tests. Over 190 tests were conducted in French Polynesia in the South Pacific, and the Soviet test-site Novaya Zemlya in the Arctic Ocean hosted 130 tests.
Testing has also been conducted in the South Pacific’s Marshall Islands (United States), Christmas Island (United States and United Kingdom), at Lop Nur in Western China, in Australia (United Kingdom), Algeria (France) and in many other locations scattered over the globe.
South Africa began building its own nuclear-weapons arsenal in 1982 but dismantled it by June 1991. It then acceded to the 1968 NPT as a non-nuclear-weapon State in July 1991.
Belarus, Kazakhstan, and Ukraine inherited nuclear weapons from the Soviet Union (USSR). When the USSR collapsed in December 1991, its nuclear arsenal was scattered over four newly independent countries: the Russian Federation, Belarus, Kazakhstan, and Ukraine. In assuming the USSR’s legacy, including its status as a nuclear-weapon state under the 1968 NPT, Ukraine, Kazakhstan, and Belarus gave up their newly inherited nuclear weapons. Russia eventually consolidated all nuclear weapons and delivery systems on its own territory (many were voluntarily destroyed in the process).
According to the Stockholm International Peace Research Institute (SIPRI), the nine nuclear-armed weapon states – the United States, Russia, the United Kingdom, France, China, India, Pakistan, Israel and Democratic People’s Republic of Korea (DPRK) – have a total inventory of 12,705 nuclear
weapons, 9,440 of which comprises of the total stockpile of warheads intended for military use. The U.S. and Russia have the largest stockpiles of 3,708 and 4,477 warheads respectively. China has approximately 350 nuclear warheads, followed by France (290), the UK (180), Pakistan (165), India (160), Israel (90), and Democratic People’s Republic of Korea (DPRK) (20).
China adopted a universal no-first-use pledge in 1964. This is a pledge that a nuclear-weapon State will not be the first party to use nuclear weapons in a conflict or crisis.
China also provides non-nuclear-weapon States with unconditional “negative security assurances.” This is a pledge by a nuclear-weapon State that it will not use nuclear weapons against a non-nuclear-weapon State.
The announced nuclear test by Democratic People’s Republic of Korea (DPRK) on 9 October 2006 broke an eight-year-long de-facto moratorium on nuclear testing. However, it also provided the first real-life test case for the CTBTO’s global alarm system.
Although only partially completed and operating in test mode, the CTBTO’s Verification Regime proved that it was capable of meeting expectations. Over 20 International Monitoring System (IMS) seismic stations throughout the world detected the explosion. Data on the time, location, and magnitude of the event was transmitted to all Signatory States within two hours.
A detailed analysis was provided by the International Data Centre (IDC) within two days. Within two weeks of the test, the radionuclide noble gas station at Yellowknife, Canada was able to detect elevated amounts of Xenon 133 in the atmosphere. Only radionuclide findings can provide ultimate proof that an explosion is nuclear in nature. By applying atmospheric transport models to backtrack the gas dispersion, its registration was found to be consistent with the hypothesized release from the DPRK’s announced test.
All the data and analyses were provided to Signatory States, enabling them to make their own judgements.
India conducted two sets of underground tests, code-named “Shakti (Power) ‘98”, on 11 and 13 May 1998 at its Pokhran underground testing site. In contrast to its initial nuclear test in 1974, there were
no claims that these were “peaceful tests.” Pakistan responded 15 days later when it conducted two sets of underground tests at its Ras Koh range on 28 and 30 May 1998, respectively.
Following the Hiroshima and Nagasaki bombings in 1945, peace organizations became highly active in protesting against nuclear weapons. By the time the United Kingdom conducted its first hydrogen bomb test in 1957, nuclear testing was considered an important public issue.
The international peace movement played an essential role throughout the Cold War in keeping the public informed on disarmament issues, while pressuring governments to negotiate arms control treaties. This movement was instrumental in various attempts to negotiate a comprehensive nuclear-test-ban. It was particularly active around the negotiations of the 1968 Treaty on the Non-Proliferation of Nuclear Weapons (NPT), the 1991 Partial Test Ban Treaty amendment conference, the NPT Review Conferences in 1995 and 2000, and finally the 1996 CTBT.
The first such meeting of scientific experts from Canada, France, Poland, Romania, the Soviet Union, the United Kingdom, and the United States was organized by the United Nations in 1958 to analyze the problems associated with nuclear test ban verification.
In 1958, the UK, U.S., and USSR started negotiations, with the aim to establish a comprehensive test-ban-treaty to prevent all nuclear explosions, everywhere. The question of implementing a verification system continuously came up and posed challenges to the negotiations based on political will to conclude a treaty.
On 31 March 1958, the USSR passed a decree to ban nuclear tests, and urged the U.S. and UK to sign it. Former U.S. President Dwight Eisenhower agreed to a temporary testing suspension and proposed to form a “Group of Experts” (GSE) which resulted in the Conference of Experts to Study the Possibility of Detecting Violations of a Possible Agreement on Suspension of Nuclear Tests, also known as the “Conference of Experts”. Comprised of specialists from Canada, Czechoslovakia, France, Poland, Romania, the UK, the U.S., and the USSR, the Conference of Experts discussed and provided the first UN report on establishing a nuclear-test-ban verification regime. Against the backdrop of the Cold War, the GSE spent twenty years designing and testing elements of a verification system that has now been implemented by the Comprehensive Nuclear-Test-Ban Treaty Organization (CTBTO).
Following the October 1962 Cuban Missile Crisis, the signing of the Partial Test Ban Treaty (PTBT) marked the first time the world witnessed real progress on negotiations for a nuclear- test-ban.
Signed by the U.S., UK and the Soviet Union on 5 August 1963 in Moscow, the PTBT banned nuclear testing in the atmosphere, underwater and in space, stating that Signatory States could not “carry out any nuclear weapon explosion, or any other nuclear explosion…in the atmosphere; beyond its limits, including outer space; or underwater, including territorial waters or high seas.” Although it signalled progress towards a comprehensive test ban treaty, the main effect of the PTBT was that environmental issues were addressed rather than a decrease in testing activities: testing went underground, which was not prohibited by the PTBT.
On 1 July 1968, the Nuclear Non-Proliferation Treaty (NPT) opened for signature. It was signed that same day by the United States, the United Kingdom, the Soviet Union and 58 other countries. At present, 191 States have joined the NPT.
The Treaty defined nuclear-weapon States (NWS) as those five countries that tested nuclear weapons before 1968: China, France, the Soviet Union, the United Kingdom and the United States —and defined all others as non-nuclear-weapon States (NNWS).
The NPT is built upon three “pillars”: nuclear non-proliferation, nuclear disarmament and the peaceful use of nuclear energy. It is also based upon a so-called “grand bargain”; namely, that the non-nuclear-weapon states agreed to not develop nuclear weapons, and in return, the nuclear-weapon states agreed to disarm their nuclear weapons. The non-nuclear weapon states would also receive assistance in developing nuclear power for peaceful purposes.
The Peaceful Nuclear Explosions Treaty (PNET) was negotiated and signed by the Soviet Union and the United States in 1976, but not ratified until 1990, to address the challenge of peaceful nuclear explosions (PNEs). The PNET obligated these two states parties inter alia not to carry out any individual nuclear explosions with a yield exceeding 150 kilotons.
The purpose of the PNET was to regulate the peaceful nuclear testing that was being carried out by both the Soviet Union and the United States for economic reasons during the 1970s and 1980s. For example, during this period, the Soviet Union used a nuclear test to create a dam, while the United States considered, but did not implement, using several hydrogen bombs to create an artificial harbour at Cape Thompson, Alaska.
The Comprehensive Nuclear-Test-Ban Treaty (CTBT), Signature and Ratification
The Nuclear Non-Proliferation Treaty (NPT) lays the foundation of the international nuclear non-proliferation regime. When it was being negotiated in the late 1960s, a permanent ban on nuclear testing was seen as an important element of such a regime.
The CTBT was a part of the package when the NPT was extended indefinitely in 1995. States Parties to the NPT agreed to achieve a comprehensive test ban treaty no later than the end of 1996 in exchange for the NPT being extended indefinitely. The CTBT was also part of the agreement to pursue nuclear disarmament at the 2000 NPT Review Conference in 2000.
The NPT and the CTBT are complementary regarding the control and limitation of nuclear arms activities and relevant technologies. With the NPT as its legal basis, the IAEA monitors the “upstream” dimension of nuclear weapons development (i.e. uranium enrichment, plutonium reprocessing and fuel fabrication), while the CTBT is meant to monitor the “downstream” final proof of a State’s intention to develop nuclear weapons, the nuclear test explosion.
By signing the Treaty, States underscore their support for a world free of nuclear testing and explosions. Signatory States become members of the CTBTO Preparatory Commission where they make decisions pertaining to the work and activities of the Commission. Signatory States may benefit from the establishment of IMS facilities and National Data Centres (NDCs) on their territories
International Data Centre (IDC) in Vienna. They may also benefit from the scientific and technological research opportunities provided by IMS’s verification data. Read more in Membership Benefits.
A ratifying State shows that it is committed to the CTBT and its entry into force. Its ratification demonstrates that it is dedicated to achieving a world free of nuclear testing, while contributing to the global nuclear disarmament and non-proliferation regime.
Only a ratifying State, together with a majority of other ratifying States, can request that conferences on facilitating the entry into force of the CTBT be convened. After entry into force of the Treaty, only the ratifying States, the so-called States Parties, are full members of the CTBTO and can participate in the decision-making processes related to the mandate and the activities of the organization.
The Preparatory Commission for the Comprehensive Nuclear-Test-Ban Treaty Organization (CTBTO) is an international organization. It was established on 19 November 1996. The CTBTO exists to prepare for the Treaty’s entry into force. It has two main tasks:
- promoting universal recognition of the Treaty; and
- building up the CTBT verification regime to ensure no nuclear explosion can go undetected.
The Comprehensive Nuclear-Test-Ban Treaty (CTBT) was adopted by the UN General Assembly on 10 September 1996 and opened for signature on 24 September 1996. The UN Secretary-General is the Depositary of the Treaty, and upon the request of a majority of ratifying States, convenes the conferences on facilitating the entry into force of the Treaty (the so-called Article XIV Conferences after the article in the Treaty which stipulates they should be held every two years).
The CTBTO is an independent international organization with its own membership and budget, but it has had a Relationship Agreement with the United Nations since 2000 which provides a framework for cooperation between the two organizations. For example, the Commission may participate in UN meetings in the same capacity as the International Atomic Energy Agency (IAEA), which is also not part of the UN Economic and Social Council (ECOSOC).
The CTBTO and the UN can also cooperate and maintain close working relationships on matters of mutual interest and concern.
Regarding financial matters, the CTBTO uses the UN scale of assessed contributions as a basis for how Member States pay their scaled annual dues to the organization. The CTBTO is located at the Vienna International Centre where all UN organizations in Vienna also have their offices.
Once the Treaty enters into force, several things will occur. Most importantly, the verification regime will become fully operational and ready to be used for verification purposes as foreseen in the Treaty.
On an organizational level, the Preparatory Commission for the Comprehensive Nuclear-Test-Ban Treaty Organization (CTBTO) as it is currently known will cease to exist, and the Comprehensive Nuclear-Test-Ban Treaty Organization (CTBTO) will be established in its place. Ratifying States will become States Parties to the Treaty, the Provisional Technical Secretariat (PTS) will become the Technical Secretariat, and the Executive Secretary will become a Director-General.
The PTS is mainly a technical organization because up to 80% of its budget is allocated to the establishment of the global verification regime.
As the PTS is primarily technical in nature, it employs mostly staff with scientific and technical skills. Examples of technical PTS jobs include work as seismologists, engineers, computer analysts, data analysts, infrasound, radionuclide and hydroacoustic officers and methodology officers, as well as an array of technicians.
Since 2005, the CTBTO’s budget has been administered through a split currency system. The split currency system was introduced as a measure to mitigate the adverse effects of currency fluctuations. Therefore, State Signatories’ assessed contributions are now split between U.S. dollars and euros in accordance with the projected expenses of the Commission in each of these currencies. The CTBTO’s total budget is the combination of the euro and US dollar amounts.
What are the main criteria for working at the PTS? In addition to possessing the required educational qualifications, one has to be a national of a State that has signed the Treaty. Besides having a well-balanced personality and good communication skills, experience in a cross-cultural work environment is always considered an asset. Knowledge of German is an additional asset because the PTS is based in Vienna, Austria.
The working language of the CTBTO is English, while the official languages are Arabic, Chinese, English, French, Russian and Spanish, just as in the United Nations. The working language means that the daily work of the CTBTO is performed in English while reference to the official languages means
that formal proceedings are conducted in all those languages. Additionally, the Treaty and other key documents are available or will be provided in all the official UN languages.
The International Monitoring System (IMS)
Once the Treaty enters into force, three additional components of the verification regime will be activated: consultation and clarification, on-site inspections and confidence-building measures.
The consultation and clarification process is intended to clarify and resolve matters concerning possible non-compliance with the Treaty’s basic obligations. On-site inspections are used to determine whether a nuclear-weapon test or any other nuclear explosion has been carried out and to collect evidence that might assist in identifying any potential violator of the Treaty.
Confidence-building measures help resolve compliance concerns arising from possible misinterpretation of verification data relating to chemical explosions (e.g. large mining explosions) and assisting in the calibration of stations that are part of the IMS.
Seismologists can tell the difference between naturally occurring earthquakes and man-made explosions with some key indicators. Most earthquakes are straightforward “shear dislocations”, meaning that geological stress causes the rock to fracture along its plane of weakness. The earthquake generates “P” and “S” waves on certain planes in a recognisable four-lobed pattern. The timeframe depends upon the strength of the earthquake, but usually takes several seconds to propagate over the entire fault plane.
With man-made explosions, nuclear or otherwise, the dynamics are different. “P” waves extend radially outward, generating equal force in all directions. In principle, there are no initial “S” waves. Energy release in an explosion occurs within a fraction of a second—far faster than in an earthquake.
When a nuclear explosion occurs, a great deal of energy is instantaneously released and physical products are created. The energy interacts with the environment and propagates sound vibrations through the solid earth, the ocean, or the atmosphere. Physical products (e.g. radioactive particles and/or gases) are released into the surrounding medium and can leak into the atmosphere, even if the actual explosion occurred underground or underwater.
The IMS uses the aforementioned three “wave-form technologies”—seismic, hydroacoustic and infrasound—with sophisticated sensors to detect the transient signals created when this explosive energy is released. At the same time, radionuclide stations collect and analyse air samples for evidence of the physical products created and carried by the prevailing winds. The radionuclide technology can show whether an explosion has been nuclear in nature.
CTBTO's state-of-the-art network can also identify earthquakes or other seismic events that could cause a tsunami. The data are recorded by 164 seismic and hydroacoustic stations that monitor underground and the oceans round-the-clock, using cutting-edge technologies. This information is sent in near real-time to National Tsunami Warning Centres (NTWC) of Member States to help them issue more timely and precise alerts -- saving more lives and minimizing risk. At present, 19 warning
centres in 18 countries, which are Treaty signatories, have signed a Tsunami Warning Agreement with the CTBTO.
On-Site Inspections (OSI)
The length of an on-site inspection depends on the inspection activities approved by the Executive Council. The inspection team must submit its first report within 25 days after the approval of the inspection. Unless the majority of the Executive Council decides to discontinue the on-site inspection, it can last up to 60 days.
During that second phase, which is called the continuation phase, mostly geophysical inspection techniques are used. According to Part II of the Protocol of the CTBT, on-site inspections can be further prolonged by another 70 days should the inspection team consider this extension necessary. Therefore, in total, an on-site inspection can last up to 130 days.
Each State Party has the right to request an on-site inspection in the case of a suspicious event. Such a request can be submitted independently from a consultation and clarification process. Requests for on-site inspections are simultaneously presented to the Executive Council and to the Director-General of the Technical Secretariat of the CTBTO.
An on-site inspection request should be based on information about the suspicious event that triggered the request. This information can be drawn from data gathered by the IMS, as well as from data generated by national monitoring systems. Regardless of the source, a request for an on-site inspection must contain detailed information about the event, including estimated time and location, as well as details about the probable physical environment of the event (i.e., whether it has taken place underground, underwater or in the atmosphere) and, which State Party or State Parties would be inspected. If a State Party requests an on-site inspection on another territory that is not a Party to the CTBT, the State Party must ensure that the on-site inspection is in line with the Protocol of the CTBT.
Yes. The managed-access regulation allows an inspected State Party to restrict the inspection team’s access to certain parts within the inspection area. This measure allows the inspected State Party to protect its national security interests and to prevent the disclosure of confidential information unrelated to the purpose of the inspection.
Several areas of no more than 4 km² can be subjected to the managed-access regulation, but the total cannot exceed 50 km². If the inspected State Party restricts the access to certain areas, it is required by the Treaty to provide alternatives for the inspection team to carry out its mandate.
The inspection team must submit an initial report on the on-site inspection no later than 25 days after the inspection has been approved. Based on this report, the Executive Council determines
whether the inspection will be continued. In case the inspection does continue, a final inspection report will be required following the conclusion of the inspection. This report contains all information relevant to inspection activities and the respective findings. It also gives an account of the cooperation with the inspected State Party and a description of the access provided to the inspection team.
Based on the report, the Executive Council reaches a final assessment as to whether non-compliance with the Treaty has occurred. If the Council concludes that the inspected State Party has indeed violated the provisions of the Treaty, the Council may recommend that the Conference takes measures to ensure compliance with the Treaty. The Conference and the Council both have the option to bring a case of Treaty violation to the attention of the UN Security Council.