Navigation and service

Ionising radiation

Environmental Radioactivity - Medicine - Occupational Radiation Protection - Nuclear Hazards Defence

Ionisierende Strahlung

The Comprehensive Nuclear-Test-Ban Treaty (CTBT) and its implementation

  • The Comprehensive Nuclear-Test-Ban Treaty is one of the central international treaties for preventing the proliferation of nuclear weapons.
  • The CTBT was opened for signature in 1996. It contains a list of 44 states (so-called Annex 2 states) that have to ratify the treaty before it enters into force.
  • To this day, three out of these 44 states have yet to sign and ratify the treaty and five countries that have already signed, still have to ratify the treaty.
  • Although CTBT has not yet entered into force, a global measuring network for monitoring the test ban is already being set up now and operated successfully.

The Comprehensive Nuclear-Test-Ban Treaty is one of the central international treaties for preventing the proliferation of nuclear weapons. Although it has not yet entered into force, a global measuring network for monitoring the test ban is already being set up now and operated successfully.

Worldwide nuclear weapons tests 1945 to 2016 Number of nuclear weapon testsNumber of nuclear weapons experiments worldwide until 2016

Start of nuclear weapons tests and Partial Test Ban Treaty

With the so-called "Trinity" test on 16 July 1945 in the USA, a nuclear weapon was detonated for the first time in human history. One month later, it made its first military deployment in the atomic bombings of Hiroshima and Nagasaki at the end of World War II. In spite of early considerations about the international control of fissile material for the production of nuclear weapons, other nations acquired the ability to produce these weapons (Soviet Union: 1949, United Kingdom: 1952).

In the 1950s, the USA and the Soviet Union began testing so-called thermonuclear weapons (colloquially referred to as "hydrogen bombs"), which have a higher explosive yield and correspondingly produce larger amounts of radioactive fallout. Among other things, the criticism following these tests led to negotiations between the USA, the Soviet Union and the United Kingdom about banning tests in the atmosphere, under water and in outer space in 1963.

The outcome was laid down in an international treaty, the Partial Nuclear Test Ban Treaty (PTBT). France (first test in 1960) and China (first test in 1964), however, did not sign this treaty and conducted nuclear weapons tests in the atmosphere even until 1980.

From partial to comprehensive test ban

World map with measuring stations International IMS measuring networkThe International IMS measuring network Source: CTBTO

The states signatory to the PTBT complied with the rules of the treaty and thereby reduced the number of atmospheric (above-ground) tests and the entailed radioactive fallout. However, the total number of nuclear weapons tests was not reduced, only that they were then mostly carried out below the Earth's surface. More than 2000 nuclear weapons tests have been counted to date.

At the diplomatic level, after the PTBT had entered into force, a comprehensive test ban treaty was discussed and in 1976 the so-called "Group of Scientific Experts" (GSE) was established. Their task was to determine whether and how compliance with such a treaty could be verified. A reliable verification system is a crucial prerequisite for states to bind themselves to a ban under international law. The experts' opinions on the possibilities and limits of scientific verification differed widely at first.

It took until the end of the Cold War for formal negotiations to begin at the United Nations Conference on Disarmament. The consultations in which also experts from the BfS had been substantially involved, could be completed already two years later and the CTBT could be opened for signature in 1996.

The parties to the negotiations, however, wanted to ensure that the signatories of the treaty did not enter into binding commitments until all states with nuclear installations - and consequently the capability to produce nuclear weapons - have joined. This is why the document contains a list of 44 states (so-called Annex 2 states) that have to ratify the treaty before it enters into force.

The Comprehensive Nuclear-Test-Ban Treaty and its implementation

To this day, three out of these 44 states have yet to sign and ratify the treaty for it to enter into force (India, North Korea, Pakistan) and five countries that have already signed, still have to ratify the treaty (Egypt, China, Iran, Israel, USA).

Once this is achieved, the prohibitory requirements will have to be verifiable right away. For this reason, the so-called Preparatory Commission for the CTBT with its task to set up an international monitoring network with 337 monitoring stations was established in Vienna. This measuring network allows to reliably verify compliance with the treaty.

Other tasks of the CTBTO include conceptually preparing on-site inspections, developing measurement methods for the latter and performing exercises.

State of 2017.05.08

How do you rate this article?

© Bundesamt für Strahlenschutz