What is the difference between u 235 and u 238

A natural fission chain will end with Thorium, which is a stable element. The fission of one U atom releases The major uses of U include the applications in nuclear weapons and nuclear power plants.

U is an isotope of Uranium, which is composed of 92 protons and neutrons in its nucleus. It is the most abundant isotope of Uranium element. It is non-fissile, which means, U does not undergo any chain reaction of nuclear fission. However, they can be made to become fissile by bombardment of a high-speed neutron. Therefore, it is called a fertile material.

But even with this bombardment, the probability of becoming fissile is very low. When the nucleus catches a neutron, it forms unstable U isotope. This U isotope is fissile and starts a chain reaction of radioactive decay. The half-life of U is about 4. The molar mass of this isotope is about This isotope also tends to alpha decay.

Apart from that, uranium has a neutron-capture cross-section that is about barns for thermal neutrons and about barns for the resonance integral the average neutrons having a range of intermediate energies. When we use uranium in a nuclear reactor, we can observe that both uranium and tend to capture a neutron, followed by conversion into uranium and plutonium , respectively. The conversion of uranium into uranium occurs at a greater rate than the conversion of uranium to plutonium Uranium is an isotope of uranium heavy metal, having 92 protons and neutrons.

When considering its natural abundance, it is about 0. This isotope is fissile , and it can sustain a fission chain reaction. Moreover, this is the only fissile isotope that occurs naturally as a primordial nuclide.

The half-life of this isotope is about This substance was discovered by Arthur Jeffery Dempster in This was developed in the early s in the Manhattan Project to make the highly enriched uranium used in the Hiroshima bomb, but was abandoned soon afterwards. However, it reappeared as the main thrust of Iraq's clandestine uranium enrichment program for weapons discovered in EMIS uses the same principles as a mass spectrometer albeit on a much larger scale. Ions of uranium and uranium are separated because they describe arcs of different radii when they move through a magnetic field.

The process is very energy-intensive — about ten times that of diffusion. Two aerodynamic processes were brought to demonstration stage around the s. One is the jet nozzle process, with demonstration plant built in Brazil, and the other the Helikon vortex tube process developed in South Africa. They depend on a high-speed gas stream bearing the UF6 being made to turn through a very small radius, causing a pressure gradient similar to that in a centrifuge. The light fraction can be extracted towards the centre and the heavy fraction on the outside.

Thousands of stages are required to produce enriched product for a reactor. It is based on Helikon but pending regulatory authorisation it has not yet been tested on UF6 - only light isotopes such as silicon. However, extrapolating from results there it is expected to have an enrichment factor in each unit of 1. One chemical process has been demonstrated to pilot plant stage but not used. In some countries used fuel is reprocessed to recover its uranium and plutonium, and to reduce the final volume of high-level wastes.

The plutonium is normally recycled promptly into mixed-oxide MOX fuel, by mixing it with depleted uranium. Where uranium recovered from reprocessing used nuclear fuel RepU is to be re-used, it needs to be converted and re-enriched. This is complicated by the presence of impurities and two new isotopes in particular: U and U, which are formed by or following neutron capture in the reactor, and increase with higher burn-up levels.

U is largely a decay product of Pu, and increases with storage time in used fuel, peaking at about ten years. Both 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 is a neutron absorber which impedes the chain reaction, and means that a higher level of U enrichment is required in the product to compensate.

For the Dutch Borssele reactor which normally uses 4. Being lighter, both isotopes tend to concentrate in the enriched rather than depleted output, so reprocessed uranium which is re-enriched for fuel must be segregated from enriched fresh uranium. The presence of U in particular means that most reprocessed uranium can be recycled only once - the main exception being in the UK with AGR fuel made from recycled Magnox uranium being reprocessed.

U is also present in RepU, but as an alpha emitter it does not pose extra problems. Traces of some fission products such as Tc may also carry over. All these considerations mean that only RepU from low-enriched, low-burnup used fuel is normally recycled directly through an enrichment plant. Much smaller quantities have been used elsewhere, in France and Japan. Some re-enrichment, e.

It assayed about 0. Recycling of MDU was discontinued in due to economic factors. A laser process would theoretically be ideal for enriching RepU as it would ignore all but the desired U, but this remains to be demonstrated with reprocessed feed. Tails from enriching reprocessed uranium remain the property of the enricher. Some recycled uranium has been enriched by Tenex at Seversk for Areva, under a ten-year contract covering about tonnes UF 6.

French media reports in alleging that wastes from French nuclear power plants were stored at Seversk evidently refer to tails from this. Early enrichment activities often left depleted uranium tails with about 0. With the wind-down of military enrichment, particularly in Russia, there was a lot of spare capacity unused.

Consequently, since the mid s some of the highest-assay tails have been sent to Russia by Areva and Urenco for re-enrichment by Tenex. These arrangements however cease in , though Tenex may continue to re-enrich Russian tails. Tenex now owns all the tails from that secondary re-enrichment, and they are said to comprise only about 0. The enriched UF 6 is converted to UO 2 and made into fuel pellets — ultimately a sintered ceramic, which are encased in metal tubes to form fuel rods, typically up to four metres long.

A number of fuel rods make up a fuel assembly, which is ready to be loaded into the nuclear reactor. See Fuel Fabrication paper. With the minor exception of reprocessed uranium, enrichment involves only natural, long-lived radioactive materials; there is no formation of fission products or irradiation of materials, as in a reactor.

Feed, product, and depleted material are all in the form of UF 6 , though the depleted uranium may be stored long-term as the more stable U 3 O 8.

Uranium is only weakly radioactive, and its chemical toxicity — especially as UF 6 — is more significant than its radiological toxicity. The protective measures required for an enrichment plant are therefore similar to those taken by other chemical industries concerned with the production of fluorinated chemicals. Uranium hexafluoride forms a very corrosive material HF — hydrofluoric acid when exposed to moisture, therefore any leakage is undesirable. Heriot, I. Kehoe, R. Urenco, Marlow UK.

Wilson, P. The Nuclear Fuel Cycle — from ore to wastes. Uranium Enrichment Updated September Most of the commercial nuclear power reactors operating or under construction in the world today require uranium 'enriched' in the U isotope for their fuel. The commercial process employed for this enrichment involves gaseous uranium in centrifuges.

An Australian process based on laser excitation is under development. Both the isotopes are radioactive, although they have different half-lives. Nuclear fuel that is used in reactors of the nuclear power plant contains both the isotopes in varying proportions. However, only U participated in fission, while the other one remains intact.

Differences between U and U Uranium Uranium An electrically neutral uranium isotope contains 92 electrons, 92 protons and neutrons i. So its atomic number is 92 and mass number is An electrically neutral uranium isotope contains 92 electrons, 92 protons and neutrons i.

Even though uranium is abundantly available on Earth, the uranium isotope has low abundancy only about 0. Uranium isotope is most common isotope of uranium found on Earth about Its atomic mass is about It is slightly lighter than U This mass difference is used for enriching purposes gaseous diffusion and gas centrifuge.

It is slightly heavier than U It has higher probability of alpha-decay and thus it is less stable.