What is a nuclear weapon?
• As is the case with the NPT, the TPNW does not define ‘nuclear weapons’ or ‘other nuclear explosive devices’. There is, though, a settled understanding among states of these terms.
• A nuclear explosive device is an explosive device whose effects are derived primarily from nuclear chain reactions.
• A nuclear weapon is a nuclear explosive device that has been weaponized, meaning that it is contained in and delivered by, for example, a missile, rocket, or bomb.
• Thus, all nuclear weapons are a form of nuclear explosive device but not all nuclear explosive devices are nuclear weapons.
States of concern
The Nuclear Weapons Ban Monitor continues to list Iran and Saudi Arabia as states of concern in relation to the prohibition on developing, producing, manufacturing, or otherwise acquiring nuclear weapons. They do not possess nuclear weapons, but both have latent nuclear breakout capabilities. Therefore, in the event that either state intended to become party to the TPNW, possible compliance issues would need to be addressed by a meeting of states parties or review conference.
Following the US withdrawal from the Joint Comprehensive Plan of Action (JCPOA), Iran restarted uranium enrichment beyond levels previously permitted by the agreement; as of November 2021, it was estimated that Iran had a stockpile of 113.8 kg of uranium enriched up to 20%, and 17.7 kg of uranium enriched up to 60%. This is particularly worrisome, because very little additional work is required to enrich uranium from 20 per cent to weapons-grade status. These developments have therefore effectively reduced Iran’s potential nuclear breakout time from approximately a year under the JCPOA to just a couple of months, although there is currently little public indication that Tehran intends to take that highly consequential step at this time. It is concerning, however, that since February 2021 Iran has continuously refused to allow the IAEA access to a facility where advanced centrifuge components are being produced; this could complicate a potential return to compliance with the JCPOA. At the time of writing, the United States and the remaining parties to the JCPOA were in the midst of negotiations over a potential US return to the deal (or perhaps the conclusion of a new interim deal); however, it remained to be seen whether either option would be possible in 2022.
If Iran obtained a true nuclear capability, Saudi Arabia would almost certainly follow through on its promise to acquire one as well. Although Saudi Arabia’s capabilities are much further behind Iran’s, the country possesses a sizable stockpile of mineable uranium ore; has announced an intention to build several nuclear reactors across the country; and possesses several types of ballistic missiles that could be used to deliver nuclear warheads. While these factors do not necessarily indicate the country’s interest in developing nuclear weapons at this time, Saudi Arabia’s Small Quantities Protocol exempts the country from IAEA monitoring and inspections obligations, which increases ambiguity around the country’s nuclear intentions and capabilities.
Test launches of missiles that are either specifically designed to deliver nuclear warheads or which are ‘nuclear-capable’ are often used to validate particular delivery systems or subcomponents and therefore constitute prohibited development of nuclear weapons under Article 1(1)(a) of the TPNW (unless the purpose of the launch is to test the conventional capability of the missile). Information from public reports, which may not be exhaustive, shows that seven of the nine nuclear-armed states (China, France, India, North Korea, Pakistan, Russia, and the United States) tested nuclear missiles in 2021.
For more information, see, in particular, the news section of the Missile Threat website produced by CSIS.
Fissile material — plutonium or highly enriched uranium (HEU)55 — is essential for all nuclear weapons. Both military and civilian stocks of HEU and plutonium must be secured and reduced (and further production limited) in order to achieve nuclear disarmament, halt proliferation of nuclear weapons, and ensure that terrorists do not acquire them. Production or procurement of fissile material constitutes prohibited development under the TPNW when done with the intent to produce nuclear weapons or other nuclear explosive devices.
According to the International Panel on Fissile Materials (IPFM), the global stockpile of HEU was estimated to be about 1,330 metric tonnes at the beginning of 2020, while the global stockpile of separated plutonium was about 540 tonnes, of which about 316 tonnes was civilian plutonium. Russia and the United States possess enormous quantities of both HEU and plutonium that could be used to produce tens of thousands of new nuclear weapons. Enriched uranium is also used in civilian reactor fuel. As of May 2021, 13 non-nuclear-armed states (Australia, Belarus, Belgium, Canada, Germany, Iran, Italy, Japan, Kazakhstan, Netherlands, Norway, South Africa, and Syria) had at least 1kg of HEU in civilian stockpiles, and some of them between 1 and 10 tonnes. One of these – Japan – also has a very large stockpile of 45.5 tonnes of separated plutonium, some in storage in the United Kingdom and in France, and some on its territory, theoretically sufficient for the production of thousands of nuclear weapons. However, there is currently no indication that any of these countries intends to develop a military nuclear-weapons programme.
Facilities that can produce fissile material (reprocessing plants and/or enrichment facilities) exist in 15 states (the nine nuclear-armed states plus Argentina, Brazil, Germany, Iran, Japan, and the Netherlands). Of these, production of fissile material intended for nuclear weapons appears to continue in India, Israel, North Korea, and Pakistan. China, Russia, and the United States do not currently appear to be producing new fissile material for weapons, but continue to operate at least one reprocessing plant or enrichment facility without non-proliferation safeguards attached. The remaining two nuclear-armed states, France and the United Kingdom now only possess fissile material production complexes under safeguards, as do Argentina, Brazil, Germany, Iran, Japan, and the Netherlands.