Uranium-235 is an isotope of uranium that differs from the element's other common isotope, uranium-238, by its ability to cause a rapidly expanding fission chain reaction, i. Uranium ( U) is a naturally occurring element with no Stable isotopes In other words all uranium is Radioactive and hence vanishing by Radioactive Uranium-238 (U-238 is the most common isotope of Uranium found in nature Nuclear fission is the splitting of the nucleus of an atom into parts (lighter nuclei) often producing Free neutrons and other smaller nuclei which may A chain reaction is a sequence of Reactions where a reactive product or by-product causes additional reactions to take place e. , it is fissile. In Nuclear engineering, a fissile material is one that is capable of sustaining a Chain reaction of Nuclear fission. It is the only fissile isotope found in any economic quantity in nature. It was discovered in 1935 by Arthur Jeffrey Dempster. Arthur Jeffrey Dempster ( August 14 1886 - March 11 1950) was a Canadian - American Physicist best known for

If at least one neutron from U-235 fission strikes another nucleus and causes it to fission, then the chain reaction will continue. This article is a discussion of neutrons in general For the specific case of a neutron found outside the nucleus see Free neutron. If the reaction will sustain itself, it is said to be critical, and the mass of U-235 required to produce the critical condition is said to be a critical mass. A critical mass is the smallest amount of Fissile material needed for a sustained Nuclear chain reaction. A critical chain reaction can be achieved at low concentrations of U-235 if the neutrons from fission are moderated to lower their speed, since the probability for fission with slow neutrons is greater. In Nuclear engineering, a neutron moderator is a medium which reduces the velocity of Fast neutrons thereby turning them into Thermal neutrons capable The neutron temperature, also called the neutron energy, indicates a free neutron's Kinetic energy, usually given in Electron volts The term A fission chain reaction produces intermediate mass fragments which are highly radioactive and produce further energy by their radioactive decay. Fission products are the atomic fragments left after a large nucleus fissions. Radioactive decay is the process in which an unstable Atomic nucleus loses energy by emitting ionizing particles and Radiation. Radioactive decay is the process in which an unstable Atomic nucleus loses energy by emitting ionizing particles and Radiation. Some of them produce neutrons, called delayed neutrons, which contribute to the fission chain reaction. In Nuclear engineering, a prompt neutron is a Neutron immediately emitted by a Nuclear fission event as opposed to a Delayed neutron which is In nuclear reactors, the reaction is slowed down by the addition of control rods which are made of elements such as boron, cadmium, and hafnium which can absorb a large number of neutrons. This article is a subarticle of Nuclear power. A nuclear reactor is a device in which Nuclear chain reactions are initiated controlled A control rod is a rod made of Chemical elements capable of absorbing many Neutrons without fissioning themselves A chemical element is a type of Atom that is distinguished by its Atomic number; that is by the number of Protons in its nucleus. Boron (ˈbɔərɒn is a Chemical element with Atomic number 5 and the chemical symbol B. Cadmium (ˈkædmiəm is a Chemical element with the symbol Cd and Atomic number 48 Hafnium (ˈhæfniəm is a Chemical element that has the symbol Hf and Atomic number 72 In nuclear bombs, the reaction is uncontrolled and the large amount of energy released creates a nuclear explosion. A nuclear weapon is an explosive device that derives its destructive force from Nuclear reactions either fission or a combination of fission and fusion. In Physics and other Sciences energy (from the Greek grc ἐνέργεια - Energeia, "activity operation" from grc ἐνεργός A nuclear explosion occurs as a result of the rapid release of energy from an intentionally high-speed Nuclear reaction.

The May 5, 1940 front-page New York Times article citing the power of uranium-235. Events 553 - The Second Council of Constantinople begins 1215 - Rebel Barons renounce their allegiance to King John Year 1940 ( MCMXL) was a Leap year starting on Monday (link will display the full 1940 calendar of the Gregorian calendar.

The fission of one atom of U-235 generates 200 MeV = 3. 2 × 10^-11 J, i. e. 18 TJ/mol = 77 TJ/kg. The mole (symbol mol) is a unit of Amount of substance: it is an SI base unit, and almost the only unit to be used to measure this However, approximately 5% of this energy is carried away by virtually undetectable neutrinos. Neutrinos are Elementary particles that travel close to the Speed of light, lack an Electric charge, are able to pass through ordinary matter almost [1]

The nuclear cross section for slow thermal neutrons is about 1000 barns. The nuclear cross section of a nucleus is used to characterize the Probability that a nuclear reaction will occur The neutron temperature, also called the neutron energy, indicates a free neutron's Kinetic energy, usually given in Electron volts The term A barn (symbol b) is a unit of Area. While the barn is not an SI unit it is accepted (although discouraged for use with the SI For fast neutrons it is in the order of 1 barn. The neutron temperature, also called the neutron energy, indicates a free neutron's Kinetic energy, usually given in Electron volts The term ^[1]

Only around 0. 72% of all natural uranium is uranium-235, the rest being mostly uranium-238. Natural uranium (NU refers to refined Uranium with the same Isotopic ratio as found in nature Uranium-238 (U-238 is the most common isotope of Uranium found in nature This concentration is insufficient for a self sustaining reaction in a light water reactor; enrichment, which just means separating out the uranium-238, must take place to get a usable concentration of uranium-235. See also Nuclear power "LWR" redirects here See also LWR (disambiguation A light water reactor or LWR is Enriched uranium is a kind of Uranium in which the percent composition of Uranium-235 has been increased through the process of Isotope separation. Pressurised Heavy Water Reactors, other heavy water reactors, and some graphite moderated reactors are known for using unenriched uranium. A pressurised heavy water reactor (PHWR is a nuclear power reactor, commonly using unenriched Natural uranium as its fuel that uses Heavy water ( Heavy water reactors use Heavy water as a Neutron moderator. Heavy water is Deuterium Oxide, D2O Uranium which has been processed to boost its uranium-235 proportion is known as enriched uranium, different applications require unique levels of enrichment. Enriched uranium is a kind of Uranium in which the percent composition of Uranium-235 has been increased through the process of Isotope separation.

The fissile uranium in nuclear weapons usually contains 85% or more of ²³⁵U known as weapon(s)-grade, though for a crude, inefficient weapon 20% is sufficient (called weapon(s)-usable); even less is sufficient, but then the critical mass required rapidly increases. A nuclear weapon is an explosive device that derives its destructive force from Nuclear reactions either fission or a combination of fission and fusion. A critical mass is the smallest amount of Fissile material needed for a sustained Nuclear chain reaction. However, judicious use of implosion and neutron reflectors can enable construction of a weapon from a quantity of uranium below the usual critical mass for its level of enrichment, though this would likely only be possible in a country which already had extensive experience in developing nuclear weapons. A neutron reflector is any material that reflects Neutrons Usually this term refers to the elastic scattering rather than to a Specular reflection. The Little Boy atomic bomb was fueled by enriched uranium. Little Boy was the Codename of the Atomic bomb, developed via the "Manhattan Project" which was dropped on Hiroshima, on August 6 1945 by the Most modern nuclear arsenals use plutonium as the fissile component, however U-235 devices remain a nuclear proliferation concern due to the simplicity of this nuclear weapon design. Nuclear proliferation is a term now used to describe the spread of Nuclear weapons, fissile material and weapons-applicable nuclear technology and information to nations Nuclear weapon designs are physical chemical and engineering arrangements that cause the physics package of a nuclear weapon to detonate

Uranium-235 has a half-life of 700 million years. Half-Life (computer-game page here It's already listed in the disambiguation page

See also

• Enriched uranium
• Nuclear fuel cycle
• Nuclear power
• Nuclear reprocessing
• United States Enrichment Corporation
• Uranium market

References

1. ^ Some Physics of Uranium

• Table of Nuclides
• US DOE Handbook 1019/1-93

External links

• Uranium | Radiation Protection Program | US EPA
• NLM Hazardous Substances Databank - Uranium, Radioactive