Nuclear Test Ban Treaties

There are two agreements that regulate nuclear testing. The first is the Partial Nuclear Test Agreement (PTBT) and the second is the Comprehensive Test Ban Treaty (CTBT). While PTBT banned nuclear tests in the atmosphere, underwater and in space so CTBT bans nuclear tests above and below ground, underwater, in space and test explosions for peaceful purposes. The latter agreement has not yet entered into force, but stay in the test explosions of nuclear weapons accepted by all nuclear weapons states except North Korea.

Partial Test Ban Treaty

Indian Prime Minister Nehru brought the issue of nuclear testing to the UN in 1954, calling for a global ban on nuclear testing. As early as 1958, attempts were made to negotiate a treaty to halt nuclear testing. Initially the US and the UK declared a one-year moratorium on nuclear testing. The Soviet Union joined just a few days later.

This first attempt was abandoned in 1961 due to political tensions and military developments. The Soviet Union resumed nuclear testing, and was quickly followed by the US.

Around the world, people began to see the risks posed by radioactive contamination from nuclear tests and public pressure forced states engaged in nuclear testing to address the problem. In 1963 the Soviet Union, the US, and the UK negotiated the Partial Test Ban Treaty (PTBT), which prohibited nuclear testing in the atmosphere, under water, and in outer space. France and China did not join the PTBT.

The PTBT failed to prohibit underground nuclear testing and the development of new types of nuclear weapons. Underground testing can also cause radioactive contamination, as the explosions often burst through the surface and release radioactive particles. The PTBT also failed to prevent increases in existing nuclear stockpiles. In fact, the US and the Soviet Union increased the number of nuclear tests after 1963, and their nuclear arsenals doubled in size between 1963 and 1970.

Comprehensive Test Ban Treaty

To come to terms with the development of new nuclear weapons by the nuclear-weapon states, to strengthen the NPT regime, and to complete the work of banning all forms of nuclear testing, a stronger treaty than the PTBT was necessary. In 1996, the Comprehensive Test Ban Treaty (CTBT) was adopted by the UN, after lengthy negotiations that began in the Geneva-based Conference on Disarmament (CD).

The CTBT prohibits all forms of nuclear testing, including tests for so-called peaceful purposes. The treaty allows, however, for “subcritical” nuclear tests, in which no self-sustaining chain reaction occurs. An International Monitoring System (IMS) was etablished to make sure no nuclear testing could take place undetected. The CTBT also allows for short-notice, on-site inspections of nuclear facilities.

In order to enter into force and become part of international law, the CTBT must be signed and ratified by the 44 nuclear-capable states (i.e., states with nuclear power or research facilities) that participated in negotiations. As of November 2014, five of these states (China, Egypt, Iran, Israel, and the US) have signed the CTBT but have not ratified it; three others (India, Pakistan and North Korea) have not signed the Treaty. In total, 183 of the world’s 195 states have signed the CTBT and 163 have ratified.

It seems hard to convince the remaining eight states, whose ratification is needed for the CTBT to enter into force, to complete this task. But even if the CTBT does not enter into force in the near future, there still seems to be an understanding among states about the cessation of nuclear testing. The test moratoria declared by most nuclear-weapon states is a sign of this common understanding.

Even if all states were to declare nuclear testing moratoria, the entry into force of the CTBT would still be important. Under the Treaty, the prohibition against testing nuclear weapons becomes legally binding on all States, rather than a voluntary and reversible policy of individual nuclear weapons states. The CTBT is considered a constructive step towards nuclear disarmament and nonproliferation, as it makes development of new nuclear weapons more difficult. The Treaty also hinders the qualitative arms race—enhancements to the technical capacity and sophistication of nuclear weapons systems, as distinct from numbers of warheads. The CTBT does not prohibit nuclear research, but it is difficult to develop new nuclear weapons without testing.

The US is one of the States that has to ratify the CTBT before it can enter into force. Former President Bill Clinton signed the treaty in 1996, but the US Senate voted against ratification in 1999. President George W. Bush expressed a wish to withdraw the US signature from the Treaty, but Congress prevented him from doing so. President Obama promised to resubmit the CTBT to the Senate during his presidential campaigns, but has not done so because rejection of the Treaty by a Republican-controlled Senate is a certainty.

Comprehensive Test Ban Treaty Organization (CTBTO)

The Comprehensive Test Ban Treaty Organization (CTBTO) verifies Member State compliance with the CTBT. A preparatory commission for the CTBTO is now working to facilitate entry into force of the treaty and to assure smooth operation of the IMS as soon as the Treaty enters into force. The verification system consists of the IMS, short-notice on-site inspections, and confidence-building measures among States.

The International Monitoring System (IMS) comprises a network of hundreds of monitoring stations and several radionuclide laboratories that monitor the Earth for evidence of nuclear explosions. The system uses four verification methods, utilizing the most modern technology available. Seismic, hydroacoustic, and infrasound stations are employed to monitor the underground, underwater, and atmospheric environments, respectively. Radionuclide stations can detect radioactive debris from atmospheric explosions or vented by underground or underwater nuclear explosions.

Today, before the entry into force of the CTBT, the IMS has about 200 active monitoring stations that submit important information used to evaluate seismic activities (earthquakes, tsunamis etc.) and determine whether these are nuclear explosions.

Last update: August 24, 2015