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The vast majority of uranium produced today is destined for use in civilian power plants. In 2014, nuclear energy generated around 11% of the world’s electricity.
After yellowcake is safely transported and converted, it is ready to be used as a source for nuclear power via fuel fabrication or enrichment. For nuclear weapons, additional processing or enrichment is required to make the material weapons-grade. Whether the path is ‘ore to bomb’ or ‘ore to electricity’, the process is long, challenging and requires sophisticated technologies.
Types of Enrichment
The majority of nuclear power reactors use uranium which is enriched to 3 to 5 percent of U235, the only isotope existing in nature that can sustain a chain reaction, or is “fissile.” Uranium enriched to less than 20 percent or greater is considered “low enriched uranium” (LEU) while highly enriched uranium (HEU) has a greater than 20 percent concentration of U235. Fissile uranium used in nuclear weapons is usually enriched to 90 percent or more U235, known as weapons-grade.
Plutonium also has fissile isotopes — mostly human-made as a byproduct in nuclear reactors where some of the neutrons released by the fission process convert U238 into plutonium. Weapons-grade plutonium contains around 90-95 percent plutonium239 (Pu239) while the range of 50-60 percent is known as reactor-grade plutonium. Any plutonium that does not fission before the fuel is removed from the reactor remains in spent fuel, which some countries reprocess to extract plutonium and uranium to make new fuel.
Plutonium does occur naturally in very small amounts from uranium ore called “pitchblende,” or uraninite, which is one of the primary mineral ores of uranium. While pitchblende can contain 50-80 percent of uranium, it only contains one part per trillion of natural plutonium.
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The nuclear weapon dropped on Hiroshima, Japan on 6 August 1945, code-named “Little Boy,” was made from HEU. The “Fat Man” bomb dropped on Nagasaki three days later was a plutonium fission bomb. At the time, the United States was the only country to have developed nuclear weapons.
The World’s Uranium and Plutonium Stockpile
According to the International Panel on Fissile Materials, the global stockpile of HEU is estimated to be around 1390 tonnes as of January 2013 with the stockpile of separated plutonium about 490 tonnes, of which approximately 260 tonnes is in civilian custody.
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The five recognized nuclear weapons states (NWS) under the Nonproliferation of Nuclear Weapons Treaty (NPT) – China, France, Russia, UK and US – have been exercising a voluntary moratorium on the production of fissile material for use in nuclear weapons since the 1990s. Of the three states that never signed on to the NPT (India, Israel and Pakistan), India and Pakistan continue to produce fissile material for use in nuclear weapons. Israel still operates its Dimona reactor, but it is believed to be producing tritium rather than plutonium. North Korea has the capability to produce weapon-grade plutonium and HEU.

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France, India, Japan, Russia and the UK operate civilian reprocessing facilities that separate plutonium from spent fuel of power reactors. China is currently operating a pilot civilian reprocessing facility. In total, 12 countries – Argentina, Brazil, France, Germany, India, Iran, Japan, the Netherlands, Pakistan, Russia, UK and US – operate uranium enrichment facilities. North Korea is also believed to have an operational uranium enrichment plant.
Between 1945 and 1996 when the Comprehensive Nuclear-Test Ban Treaty (CTBT) opened for signature, more than 2,000 nuclear tests were carried out all over the world. Since 1996, France, Russia and the UK have ratified the CTBT while China and the US have not; but the two continue to hold moratoriums on testing. India conducted two tests in 1998 as did Pakistan. Of the 190 states that have joined the NPT, North Korea is the only one to have acceded in 1985 and then announced its withdrawal in 2003. North Korea conducted its first nuclear test on 9 October 2006, followed by a second one on 25 May 2009, and a third on 12 February 2013.
The International Atomic Energy Agency (IAEA), which promotes peaceful uses of nuclear energy, verifies NPT compliance among member states.