In contravention of the Non-Proliferation Treaty, weapons grade nuclear materials have been sold to countries which are secretly developing nuclear weapons.
In 1942, some three years before the USA had tested its first atomic bomb, Manhattan Project officials were negotiating covert purchase agreements with the Congo, India, Brazil, and other nations in a surreptitious attempt to obtain a post-war USA monopoly over the world's known uranium supplies. In 1988, German and Belgian officials are thought to have accepted bribes to conceal and falsify documentation of shipments of radioactive material. The British government admitted that shipments of civilian plutonium to the US for military purposes. India is thought to receive heavy water from China for use in building a nuclear arsenal.
Nuclear smuggling has become an increasingly lucrative business for professional dealers. Several countries are known to be circumventing supplier-country restrictions on importation of nuclear weapons material manufacturing facilities by means of purchasing such components piece by piece through a series of dummy trading companies, anonymous purchasing agents, and falsified intent of means statements. Clandestine trade has played a central role in advancing the nuclear weapons capability of Argentina, Brazil, India, Iraq and Pakistan. In 1992, German authorities seized quantities of caesium 137 and strontium 90 destined for sale on the black market. They announced that 20 kilos of weapons-grade uranium was missing. In 1994 security forces in western and eastern Europe were combining their efforts in response to the growing menace of smuggling of nuclear materials from countries of the former USSR. Interpol in 1994 was treating 30 nuclear smuggling cases as extremely serious.