Can you own uranium

This means that it is barely radioactive, less so than many other radioisotopes in rocks and sand. Uranium has a specific radioactivity of When the nucleus of a U atom is split in two by a neutron c , some energy is released in the form of heat, and two or three additional neutrons are thrown off.

If enough of these expelled neutrons split the nuclei of other U atoms, releasing further neutrons, a chain reaction can be achieved. When this happens over and over again, many millions of times, a very large amount of heat is produced from a relatively small amount of uranium. It is this process, in effect 'burning' uranium, which occurs in a nuclear reactor. In a nuclear reactor the uranium fuel is assembled in such a way that a controlled fission chain reaction can be achieved.

The heat created by splitting the U atoms is then used to make steam which spins a turbine to drive a generator, producing electricity. Whereas the U atom is 'fissile', the U atom is said to be 'fertile'. This means that it can capture a neutron and become indirectly plutonium, which is fissile. Pu is very much like U, in that it can fission following neutron capture, also yielding a lot of energy d. Both uranium and plutonium were used to make bombs before they became important for making electricity and radioisotopes.

But the type of uranium and plutonium for bombs is different from that in a nuclear power plant. This amounts to over billion kWh, as much as from all sources worldwide a few decades ago. It comes from about nuclear reactors with a total output capacity of about , MWe operating in 32 countries plus Taiwan. Over 50 more reactors are under construction and about another are planned 2.

A typical megawatt MWe reactor can provide enough electricity for a modern city of close to one million people, about 8 billion kWh per year. Germany and Japan have derived a similar amount of their electricity from uranium in the past. Nuclear power stations and fossil-fuelled power stations of similar capacity have many features in common. Both require heat to produce steam to drive turbines and generators.

In a nuclear power station, however, the fissioning of uranium atoms replaces the burning of coal or gas. The chain reaction that takes place in the core of a nuclear reactor is controlled by rods which absorb neutrons. They are inserted or withdrawn to set the reactor at the required power level. The fuel elements are surrounded by a substance called a moderator to slow the speed of the emitted neutrons and thus enable the chain reaction to continue e.

Water, graphite and heavy water are used as moderators in different types of reactors. Uranium is widespread in many rocks, and even in seawater. However, like other metals, it is seldom sufficiently concentrated to be economically recoverable.

Where it is, we speak of an orebody. Uranium is fairly soluble and uranium oxide precipitates from uranium-bearing groundwaters when they enter a reducing environment. It can be mobilised re-dissolved in situ from such placer deposits by oxygenated leach solution. In defining what is ore, assumptions are made about the cost of mining and the market price of the metal. Known uranium resources are therefore calculated as tonnes recoverable up to a certain cost.

Many more countries have smaller deposits which could be mined. See information page on Supply of Uranium. Uranium is sold only to countries which are signatories of the Nuclear Non-Proliferation Treaty, and which allow international inspection to verify that it is used only for peaceful purposes.

See information page on Safeguards. Uranium ore can be mined by underground or open-cut methods, depending on its depth. After mining, the ore is crushed and ground up. Then it is treated with acid to dissolve the uranium, which is then recovered from solution. Uranium may also be mined by in situ leaching ISL , where it is dissolved from the orebody in situ and pumped to the surface. Before it can be used in a reactor for electricity generation, however, it must undergo a series of processes to produce a useable fuel.

For most of the world's reactors, the next step in making a useable fuel is to convert the uranium oxide into a gas, uranium hexafluoride UF 6 , which enables it to be enriched f.

Enrichment increases the proportion of the U isotope from its natural level of 0. This enables greater technical efficiency in reactor design and operation, particularly in larger reactors, and allows the use of ordinary water as a moderator. This, largely U, has potential use in fast neutron reactors. After enrichment, the UF 6 gas is converted to uranium dioxide UO 2 which is formed into fuel pellets. These fuel pellets are placed inside thin metal tubes which are assembled in bundles to become the fuel elements for the core of the reactor.

Used reactor fuel is removed from the reactor and stored, either to be reprocessed or disposed of in deep geological repositories. The uranium orebody contains both U and mostly U In the case of Ranger ore - with 0.

When the ore is processed, the U and the very much smaller masses of U and the U are removed. The controlling long-lived isotope then becomes Th which decays with a half life of 77, years to radium followed by radon When used fuel is reprocessed, both plutonium and uranium are usually recovered separately. This is complicated by the presence of impurities g and two isotopes in particular, U and U, which are formed by or following neutron capture in the reactor, and increase with higher burn-up levels h.

U here is largely a decay product of Pu, and increases with storage time in used fuel, peaking at about ten years. Both U and U decay much more rapidly than U and U, and one of the daughter products of U emits very strong gamma radiation, which means that shielding is necessary in any plant handling material with more than very small traces of it. U, comprising about 0. Because they are lighter than U, both U and U tend to concentrate in the enriched rather than depleted output, so reprocessed uranium RepU that is re-enriched for fuel must be segregated from enriched fresh uranium.

The presence of U in particular means that the U enrichment level needs to be a bit higher than for fresh uranium, and most reprocessed uranium can normally be recycled only once. In the future, laser enrichment techniques may be able to remove these difficult isotopes. The number of countries holding stocks of 1 kg or more of HEU stood at 29 then, but this has since fallen to About The nuclear weapon states NWS possess a combined estimated total of tonnes. Most civil HEU is used in research reactors.

Both the USA and Russia also launched 'take-back' programmes to retrieve HEU they provided to these countries for use in their nuclear programmes. 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.

Uranium Ore. Images SI amazon. This content is created and maintained by a third party, and imported onto this page to help users provide their email addresses. You may be able to find more information about this and similar content at piano. New centrifuge plants are being built in France and USA. Several plants are adding capacity. With surplus capacity, Russian plants operate at low tails assays underfeeding to produce low-enriched uranium for sale.

The feedstock for enrichment consists of uranium hexafluoride UF 6 from the conversion plant. The tails assay concentration of U is an important quantity since it indirectly determines the amount of work that needs to be done on a particular quantity of uranium in order to produce a given product assay. Feedstock may have a varying concentration of U, depending on the source.

Natural uranium will have a U concentration of approximately 0. The capacity of enrichment plants is measured in terms of 'separative work units' or SWU.

The SWU is a complex unit which indicates the energy input relative to the amount of uranium processed, the degree to which it is enriched i. The unit is strictly: kilogram separative work unit, and it measures the quantity of separative work performed to enrich a given amount of uranium a certain amount when feed and product quantities are expressed in kilograms.

The unit 'tonnes SWU' is also used. There is always a trade-off between the cost of enrichment SWU and the cost of uranium. However, especially in relation to new small reactor designs, there is increasing interest in higher enrichment levels. Some small demand already exists for research reactors. The first graph shows enrichment effort SWU per unit of product. The second shows how one tonne of natural uranium feed might end up: as kg of uranium for power reactor fuel, as 26 kg of typical research reactor fuel, or conceivably as 5.

The curve flattens out so much because the mass of material being enriched progressively diminishes to these amounts, from the original one tonne, so requires less effort relative to what has already been applied to progress a lot further in percentage enrichment. The relatively small increment of effort needed to achieve the increase from normal levels is the reason why enrichment plants are considered a sensitive technology in relation to preventing weapons proliferation, and are very tightly supervised under international agreements.

Where this safeguards supervision is compromised or obstructed, as in Iran, concerns arise. About , SWU is required to enrich the annual fuel loading for a typical MWe light water reactor at today's higher enrichment levels. Enrichment costs are substantially related to electrical energy used. In the past it has also accounted for the main greenhouse gas impact from the nuclear fuel cycle where the electricity used for enrichment is generated from coal. However, it still only amounts to 0.

The utilities which buy uranium from the mines need a fixed quantity of enriched uranium in order to fabricate the fuel to be loaded into their reactors. This is the contracted or transactional tails assay, and determines how much natural uranium must be supplied to create a quantity of Enriched Uranium Product EUP — a lower tails assay means that more enrichment services notably energy are to be applied.

The enricher, however, has some flexibility in respect to the operational tails assay at the plant. This is known as underfeeding. In respect to underfeeding or overfeeding , the enricher will base its decision on the plant economics together with uranium and energy prices.

With reduced demand for enriched uranium following the Fukushima accident, enrichment plants have continued running, since it is costly to shut down and re-start centrifuges. The surplus SWU output can be sold, or the plants can be underfed so that the enricher ends up with excess uranium for sale, or with enriched product for its own inventory and later sale.

With forecast overcapacity, it is likely that some older cascades will be retired. Obsolete diffusion plants have been retired, the last being some belated activity at Paducah in Natural uranium is usually shipped to enrichment plants in type 48Y cylinders, each holding about These cylinders are then used for long-term storage of DU, typically at the enrichment site. Enriched uranium is shipped in type 30B cylinders, each holding 2.

The three enrichment processes described below have different characteristics. Diffusion is flexible in response to demand variations and power costs but is very energy-intensive. With centrifuge technology it is easy to add capacity with modular expansion, but it is inflexible and best run at full capacity with low operating cost. Laser technology can strip down to very low level tails assay, and is also capable of modular plant expansion.

The gas centrifuge process was first demonstrated in the s but was shelved in favour of the simpler diffusion process. It was then developed and brought on stream in the s as the second-generation enrichment technology. It is economic on a smaller scale, e.

It is much more energy efficient than diffusion, requiring only about kWh per SWU. China has two small centrifuge plants imported from Russia. China has several centrifuge plants, the first at Hanzhun with 6th generation centrifuges imported from Russia. The Lanzhou plant is operating at 3.

Others are under construction. Brazil has a small plant which is being developed to 0. Pakistan has developed centrifuge enrichment technology, and this appears to have been sold to North Korea. In both France and the USA plants with late-generation Urenco centrifuge technology have been built to replace ageing diffusion plants, not least because they are more economical to operate.

Full initial capacity of 3. In it applied for doubling in capacity to 6. It is now cancelled, and in Orano requested the NRC to terminate the licence. It was designed to have an initial annual capacity of 3. A demonstration cascade started up in September with about 20 prototype machines, and a lead cascade of commercial centrifuges started operation in March Like the diffusion process, the centrifuge process uses UF 6 gas as its feed and makes use of the slight difference in mass between U and U The gas is fed into a series of vacuum tubes, each containing a rotor 3 to 5 metres tall and 20 cm diameter.

When the rotors are spun rapidly, at 50, to 70, rpm, the heavier molecules with U increase in concentration towards the cylinder's outer edge. There is a corresponding increase in concentration of U molecules near the centre. The countercurrent flow set up by a thermal gradient enables enriched product to be drawn off axially, heavier molecules at one end and lighter ones at the other.

The Russian centrifuges are less than one metre tall. Chinese ones are larger, but shorter than Urenco's. The enriched gas forms part of the feed for the next stages while the depleted UF 6 gas goes back to the previous stage. Eventually enriched and depleted uranium are drawn from the cascade at the desired assays. To obtain efficient separation of the two isotopes, centrifuges rotate at very high speeds, with the outer wall of the spinning cylinder moving at between and metres per second to give a million times the acceleration of gravity.

Although the volume capacity of a single centrifuge is much smaller than that of a single diffusion stage, its capability to separate isotopes is much greater. Centrifuge stages normally consist of a large number of centrifuges in parallel. Such stages are then arranged in cascade similarly to those for diffusion. In the centrifuge process, however, the number of stages may only be 10 to 20, instead of a thousand or more for diffusion.

Centrifuges are designed to run for about 25 years continuously, and cannot simply be slowed or shut down and restarted according to demand. Western cascades are designed for 0. Laser enrichment processes have been the focus of interest for some time. They are a possible third-generation technology promising lower energy inputs, lower capital costs and lower tails assays, hence significant economic advantages.