Enrichment facilities if in wrong hands can produce highly enriched uranium, basic core of fissile material for a bomb.
Reprocessing also called recycling produces uranium (96\%), which is reused in reactors, highly radioactive waste (3\%) and plutonium (1\%). All nuclear reactors produce plutonium. MOX fuel – a mixed uranium/plutonium oxide fuel- is being used in some countries in order to ruse the plutonium produced. The plutonium if diverted would give the basis for a weapon.
First, what is enrichment? The aim of enrichment is to increase the proportion of fissile uranium-235 atoms within uranium. For uranium fuel to be appropriate for a nuclear reactor it must be enriched to contain 2-3\% uranium-235. Weapons-grade uranium must contain 90\% or more U-235. A common enrichment method is a gas centrifuge. Another method of enrichment is known as diffusion. This last technique allows easy sequences of re- enrichment capabilities over the usual enriched fuel to 3-4\%. This is a risk if such installation is in wrong or malevolent hands.
What is reprocessing? Reprocessing is the chemical operation which separates useful fuel for recycling from nuclear waste. Used fuel rods have their metallic outer casing stripped away before being dissolved in hot nitric acid. This produces uranium (96\%), which is reused in reactors, highly radioactive waste (3\%) and plutonium (1\%). All nuclear reactors produce plutonium, but military types of reactors produce it more efficiently than others.
A reactor to produce sufficient plutonium could be housed in an ordinary-looking building. This makes extracting plutonium by reprocessing an attractive option to any country wishing to pursue a clandestine weapons program. Reprocessed plutonium is used in the manufacturing of MOX fuel which can be re-employed in the reactors. The concern is that certain types of plutonium can also be used to manufacture nuclear weapons.
To make fuel for a uranium bomb, highly-enriched uranium hexafluoride is first converted into uranium oxide, and then uranium metal ingots. This can be done using relatively simple chemical and engineering processes. Plutonium offers several advantages over uranium as a component in a nuclear weapon. Only about 4kg of plutonium is needed to make a bomb. Such a device would explode with the power of 20 kilotons. To produce 12kg of plutonium per year, only a relatively small reprocessing facility would be needed. Nuclear material transferred to a customer may not be enriched to 20 \% ¨U-235 or more. The customer’s state has implemented, or established a firm plan to develop a State System of Accounting for and Control of Nuclear Materials which is technically sound, operational, and is providing adequate authority, resources and independence.
The perceived risks are nuclear black markets (non-State actors), breakouts that is withdrawal from the NPT and disarmament slowdown (failure to fulfil obligations under the NPT).
Measures to prevent these risks would be to strengthen non-proliferation regime
(improve export controls, more information on nuclear trade etc.), minimize risk of breakout by internationalisation of key points of nuclear fuel cycle (IAEA proposal).