Paths to the Bomb — Highly Enriched Uranium vs. Plutonium
If a country or sub-state actor chooses to build nuclear weapons, its design choices will be constrained by the type of fissile material that it can obtain. Today only the five Nuclear Non-Proliferation Treaty (NPT) nuclear weapon States and the countries outside the NPT have access to unsafeguarded nuclear reactors and plutonium reprocessing plants, or uranium enrichment facilities, which are needed to create new fissile material for weapons. However, several countries have at various points initiated secret programmes in an effort to develop fissile material production capability. As of 2007, there were approximately 500 tons of separated plutonium and 1400 tons of HEU stockpiled worldwide.
Plutonium allows for building lighter and more compact warheads that can be adapted to longer-range missiles.
As the mass of plutonium needed for starting a chain reaction is less than that of HEU, most countries have opted for plutonium as chemical separation (reprocessing) is easier and less energy intensive than isotope separation (enrichment). Also, plutonium allows for building lighter and more compact warheads that can be adapted to longer-range missiles. The first United States weapons were different types because HEU and plutonium production were both in very early stages and material was limited. The Soviet Union, United Kingdom, and France all tested plutonium implosion devices because of the availability of plutonium and the limited strategic value of gun-type weapons. The Soviet Union initially had a parallel program to develop a gun-type device but scrapped it as soon as its implosion test proved successful.
China’s first nuclear test in 1964 used an HEU implosion device because the country had not yet developed the means to produce plutonium.
Israel has a plutonium-producing reactor at Dimona as well as a reprocessing plant, which the International Panel on Fissile Materials estimates can handle about 40 to100 tons of spent fuel each year.
South Africa possesses significant uranium reserves and it pioneered a new uranium enrichment method, giving it a route to the bomb; its nuclear devices, which have been verifiably dismantled, all used HEU.
India misused plutonium extracted from its CIRUS heavy water reactor, supplied for energy purposes only, for conducting its first nuclear explosion 'Smiling Buddah' in 1974.
India’s 1974 nuclear explosion used plutonium extracted from its CIRUS heavy water reactor, supplied for energy purposes only (This misuse led to sanctions on India and the creation of the Nuclear Suppliers Group). Although it has now developed centrifuge enrichment capability, India claims that all HEU is intended for naval propulsion. To cope with its shortage of uranium reserves, India hopes to develop reactors that breed plutonium and to move eventually to a thorium fuel cycle.
Pakistan drew on the expertise of A. Q. Khan; and his procurement network to develop centrifuge enrichment capability. Since Pakistan did not initially have plutonium production capability, it is assumed that HEU was used for the tests it conducted in 1998. However, Pakistan’s plutonium production reactor at Khushab came online in 1998. These heavy water reactors will produce plutonium and tritium, key elements for thermonuclear weapons.
Also the Democratic People's Republic of Korea (DPRK) used plutonium for conducting its first nuclear test on 9 October 2006.