As a result the number of countries possessing HEU has more than halved. The number of countries with a kilogram or more of HEU is expected to decrease further as Russia is set to take back more of the HEU that it provided and to reprocess and blend down the recovered HEU. HEU production for civil purposes largely stopped years ago.
However, Russia decided to resume producing HEU for a Chinese fast reactor that reached criticality in Thorium, as well as uranium, can be used as a nuclear fuel. Although not fissile itself, Th will absorb slow neutrons to produce uranium U i , which is fissile and long-lived.
The irradiated fuel can then be unloaded from the reactor, the U separated from the thorium, and fed back into another reactor as part of a closed fuel cycle.
Alternatively, thorium can be incorporated into the fuel salt of a molten salt reactor MSR and the U burned as it is bred. See information page on MSRs. U has higher neutron yield per neutron absorbed than U or Pu Given a start with some other fissile material U, U or Pu as a driver, a breeding cycle similar to but more efficient than that with U and plutonium in conventional thermal neutron reactors can be set up.
The driver fuels provide all the neutrons initially, but are progressively supplemented by U as it forms from the thorium. However, the intermediate product protactinium Pa is a neutron absorber which diminishes U yield.
See information page on Thorium. Specifically: Th gains a neutron to form Th, which soon beta decays half-life 22 minutes to protactinium The Pa half-life of 27 days decays into U Some U is also formed along with Th, and a decay product of this is very gamma active.
Chemical separation of the protactinium from irradiated thorium would minimize U contamination of the ultimate U Incidentally, more than about 50 ppm U in U renders it unsuitable for weapons. There are also other uses for uranium-fuelled nuclear reactors. Over small nuclear reactors power more than ships, mostly submarines, but ranging from icebreakers to aircraft carriers.
These can stay at sea for very long periods without having to make refuelling stops. In most such vessels the steam drives a turbine directly geared to propulsion. The heat produced by nuclear reactors can also be used directly rather than for generating electricity. In Russia, for example, it is used to heat buildings and elsewhere it provides heat for a variety of industrial processes such as water desalination.
In the future, high-temperature reactors could be used for industrial processes such as thermochemical production of hydrogen. See information page on Hydrogen Production and Uses. Radioactive materials radioisotopes play a key role in the technologies that provide us with food, water and good health and have become a vital part of modern life. They are produced by bombarding small amounts of particular elements with neutrons. Using relatively small special purpose nuclear reactors usually called research reactors , a wide range of radioisotopes can be made at low cost.
The use of radioisotopes has become widespread since the early s, and there are now some research reactors in 56 countries producing them. In medicine, radioisotopes are widely used for diagnosis, and also for treatment and research. Radioactive chemical tracers emit gamma radiation which provides diagnostic information about a person's anatomy and the functioning of specific organs.
Radiotherapy also employs radioisotopes in the treatment of some illnesses, such as cancer. More powerful gamma sources are used to sterilise syringes, bandages and other medical equipment.
About one in two people in Western countries is likely to experience the benefits of nuclear medicine in their lifetime, and gamma sterilisation of equipment is almost universal. See information page on Radioisotopes in Medicine. In the preservation of food, radioisotopes are used to inhibit the sprouting of root crops after harvesting, to kill parasites and pests, and to control the ripening of stored fruit and vegetables.
Irradiated foodstuffs are accepted by world and national health authorities for human consumption in an increasing number of countries.
They include potatoes, onions, dried and fresh fruits, grain and grain products, poultry and some fish. Some prepacked foods can also be irradiated. Agriculturally, in the growing crops and breeding livestock, radioisotopes also play an important role. They are used to produce high-yielding, disease- and weather-resistant varieties of crops, to study how fertilisers and insecticides work, and to improve the productivity and health of domestic animals.
Industrially, and in mining, they are used to examine welds, to detect leaks, to study the rate of wear of metals, and for on-stream analysis of a wide range of minerals and fuels. See information page on Radioisotopes in Industry. Environmentally, radioisotopes are used to trace and analyse pollutants, to study the movement of surface water, and to measure water runoffs from rain and snow, as well as the flow rates of streams and rivers.
Most household smoke detectors use a radioisotope americium derived from the plutonium formed in nuclear reactors. These alarms save many lives. Every tonne of natural uranium produced and enriched for use in a nuclear reactor gives about kg of enriched fuel 3. The balance is depleted uranium tails U, typically with 0. This major portion has been depleted in its fissile U isotope and, incidentally, U by the enrichment process.
It is commonly known as DU if the focus is on the actual material, or enrichment tails if the focus is on its place in the fuel cycle and its U assay.
DU tails are either stored as UF 6 or especially in France and now also Russia and the USA deconverted back to U 3 O 8 , which is more benign chemically and thus more suited for long-term storage. It is also less chemically toxic. Every year over 50, tonnes of depleted uranium joins already substantial stockpiles in the USA, Europe and Russia. World stock is about 1. This weapons-grade material is diluted about with depleted uranium, or with depleted uranium that has been enriched slightly to 1.
Some, assaying 0. Potentially DU can be used as fuel in future generations of fast neutron reactors. In the long-term perspective it thus needs to be seen as a resource. Other uses depend on the metal's very high density 1. Hence, where maximum mass must fit in minimum space, such as aircraft control surface and helicopter counterweights, yacht keels, etc, it is often well suited.
Until the mid s it was used in dental porcelains. In addition it is used for radiation shielding in hospital and industrial radiography, being some five times more effective than lead in this role in Australia some 6 tonnes is used thus, in about 60 items of equipment. Also because of its density, it is used as solid slugs or penetrators in armour-piercing projectiles, alloyed with abut 0.
Depleted uranium is not classified as a dangerous substance radiologically, though it is a potential hazard in large quantities, beyond what could conceivably be breathed. Its emissions are very low, since the half-life of U is the same as the age of the Earth 4. There are no reputable reports of cancer or other negative health effects from radiation exposure to ingested or inhaled natural or depleted uranium, despite much study. However, uranium does have a chemical toxicity about the same as that of lead, so inhaled fume or ingested oxide is considered a health hazard.
Most uranium actually absorbed into the body is excreted within days, the balance being laid down in bone and kidneys. Its biological effect is principally kidney damage. This is about eight times our normal background intake from natural sources. Standards for drinking water and concentrations in air are set accordingly. Like most radionuclides, it is not known as a carcinogen, or to cause birth defects from effects in utero or to cause genetic mutations.
Radiation from DU munitions depends on how long since the uranium has been separated from the lighter isotopes so that its decay products start to build up. Decay of U gives rise to Th, Pa beta emitters and U an alpha emitter k.
Like the natural uranium ore, DU is radioactive. DU mainly emits alpha particle radiation. Alpha particles don't have enough energy to go through skin.
As a result, exposure to the outside of the body is not considered a serious hazard. However, if DU is ingested or inhaled, it is a serious health hazard.
Alpha particles directly affect living cells and can cause kidney damage. In the s, the U. DU was also used to create armor for tanks and as weights to balance aircrafts.
The U. DU is still used to make bullets and mortar shells. DU contamination of spent shells and shell fragments is a hazard at some military firing ranges. Avoid facilities that use or process DU: DU is dangerous when it is inside your body. Avoid internal exposure: If DU gets inside the body the hazards increase. Minimize your risk of internal exposure by limiting your proximity to uranium manufacturing plants and firing ranges that continue to use DU in ammunition. They provide DU education programs as part of soldier training.
Military Health System Information on Environmental Exposures to Depleted Uranium Learn more about environmental exposure to depleted uranium, including health hazards to members of the military.
The NRC regulates and oversees the civilian uses of nuclear materials in the United States by licensing facilities that possess, use, or dispose of nuclear materials; establishing standards; and inspecting licensed facilities.
This includes uranium used at nuclear power plants. Military public health authorities knew about this contamination and took on-site corrective measures. Veterans at K-2 are eligible for DU testing. DU is a potential health hazard if it enters the body, such as through embedded fragments , contaminated wounds, and inhalation or ingestion.
Simply riding in a vehicle with DU weapons or DU shielding will not expose a service member to significant amounts of DU or external radiation. Inhaled DU particles are likely cleared from the lungs over several years.
DU fragments may remain for many years. Older studies show high exposures to U may especially affect the kidneys. So far, no health problems associated with DU exposure have been found in Veterans exposed to DU in friendly fire events.
Researchers and clinicians continue to monitor the health of these Veterans.
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