The fission of one atom of uranium-235 releases 202.5 MeV (3.24×10−11 J) inside the reactor. That corresponds to 19.54 TJ/mol, or 83.14 TJ/kg.[3] Another 8.8 MeV escapes the reactor as anti-neutrinos. When 235 92U nuclides are bombarded with neutrons, one of the many fission reactions that it can undergo is the following (shown in the adjacent image):
If at least one neutron from uranium-235 fission strikes another nucleus and causes it to fission, then the chain reaction will continue. If the reaction continues to sustain itself, it is said to be critical, and the mass of 235U required to produce the critical condition is said to be a critical mass. A critical chain reaction can be achieved at low concentrations of 235U if the neutrons from fission are moderated to lower their speed, since the probability for fission with slow neutrons is greater. A fission chain reaction produces intermediate mass fragments which are highly radioactive and produce further energy by their radioactive decay. Some of them produce neutrons, called delayed neutrons, which contribute to the fission chain reaction. The power output of nuclear reactors is adjusted by the location of control rods containing elements that strongly absorb neutrons, e.g., boron, cadmium, or hafnium, in the reactor core. In nuclear bombs, the reaction is uncontrolled and the large amount of energy released creates a nuclear explosion.
Nuclear weaponsedit
The Little Boygun-type atomic bomb dropped on Hiroshima on August 6, 1945, was made of highly enriched uranium with a large tamper. The nominal spherical critical mass for an untampered 235U nuclear weapon is 56 kilograms (123 lb),[4] which would form a sphere 17.32 centimetres (6.82 in) in diameter. The material must be 85% or more of 235U and is known as weapons grade uranium, though for a crude and inefficient weapon 20% enrichment is sufficient (called weapon(s)-usable). Even lower enrichment can be used, but this results in the required critical mass rapidly increasing. Use of a large tamper, implosion geometries, trigger tubes, polonium triggers, tritium enhancement, and neutron reflectors can enable a more compact, economical weapon using one-fourth or less of the nominal critical mass, though this would likely only be possible in a country that already had extensive experience in engineering nuclear weapons. Most modern nuclear weapon designs use plutonium-239 as the fissile component of the primary stage;[5][6] however, HEU (highly enriched uranium, in this case uranium that is 20% or more 235U) is frequently used in the secondary stage as an ignitor for the fusion fuel.
Energy released when those prompt neutrons which do not (re)produce fission are captured
8.8
Total energy converted into heat in an operating thermal nuclear reactor
202.5
Energy of anti-neutrinos
8.8
Sum
211.3
Natural decay chainedit
Usesedit
Uranium-235 has many uses such as fuel for nuclear power plants and in nuclear weapons such as nuclear bombs. Some artificial satellites, such as the SNAP-10A and the RORSATs were powered by nuclear reactors fueled with uranium-235.[7][8]
Referencesedit
^"#Standard Reaction: 235U(n,f)". www-nds.iaea.org. IAEA. Retrieved 4 May 2020.
^. Archived from the original on July 17, 2007. Retrieved 2009-01-18.{{cite web}}: CS1 maint: bot: original URL status unknown (link)
^. Archived from the original on 1999-05-07. Retrieved 2010-09-02.
^. Federation of American Scientists. Archived from the original on 2008-12-26. Retrieved 2016-06-04.
^Miner, William N.; Schonfeld, Fred W. (1968). "Plutonium". In Clifford A. Hampel (ed.). The Encyclopedia of the Chemical Elements. New York (NY): Reinhold Book Corporation. p. 541. LCCN 68029938.
^Schmidt, Glen (February 2011). "SNAP Overview – radium-219 – general background" (PDF). American Nuclear Society. Retrieved 27 August 2012.
uranium, redirects, here, world, submarine, german, submarine, 235u, isotope, uranium, making, about, natural, uranium, unlike, predominant, isotope, uranium, fissile, sustain, nuclear, chain, reaction, only, fissile, isotope, that, exists, nature, primordial,. U 235 redirects here For the World War II submarine see German submarine U 235 Uranium 235 235U or U 235 is an isotope of uranium making up about 0 72 of natural uranium Unlike the predominant isotope uranium 238 it is fissile i e it can sustain a nuclear chain reaction It is the only fissile isotope that exists in nature as a primordial nuclide Uranium 235 235UUranium metal highly enriched in uranium 235GeneralSymbol235UNamesuranium 235 235U U 235Protons Z 92Neutrons N 143Nuclide dataNatural abundance0 72 Half life t1 2 703800 000 yearsIsotope mass235 0439299 DaSpin7 2 Excess energy40914 062 1 970 keVBinding energy1783 870 285 1 996 keVParent isotopes235Pa235Np239PuDecay products231ThDecay modesDecay modeDecay energy MeV Alpha4 679Isotopes of uranium Complete table of nuclidesUranium 235 has a half life of 703 8 million years It was discovered in 1935 by Arthur Jeffrey Dempster Its fission cross section for slow thermal neutrons is about 584 3 1 barns 1 For fast neutrons it is on the order of 1 barn 2 Most neutron absorptions induce fission though a minority result in the formation of uranium 236 citation needed Contents 1 Fission properties 1 1 Nuclear weapons 2 Natural decay chain 3 Uses 4 References 5 External linksFission properties edit nbsp Nuclear fission seen with a uranium 235 nucleusThe fission of one atom of uranium 235 releases 202 5 MeV 3 24 10 11 J inside the reactor That corresponds to 19 54 TJ mol or 83 14 TJ kg 3 Another 8 8 MeV escapes the reactor as anti neutrinos When 23592 U nuclides are bombarded with neutrons one of the many fission reactions that it can undergo is the following shown in the adjacent image 10 n 23592 U 14156 Ba 9236 Kr 3 10 n Heavy water reactors and some graphite moderated reactors can use natural uranium but light water reactors must use low enriched uranium because of the higher neutron absorption of light water Uranium enrichment removes some of the uranium 238 and increases the proportion of uranium 235 Highly enriched uranium HEU which contains an even greater proportion of uranium 235 is sometimes used in the reactors of nuclear submarines research reactors and nuclear weapons If at least one neutron from uranium 235 fission strikes another nucleus and causes it to fission then the chain reaction will continue If the reaction continues to sustain itself it is said to be critical and the mass of 235U required to produce the critical condition is said to be a critical mass A critical chain reaction can be achieved at low concentrations of 235U if the neutrons from fission are moderated to lower their speed since the probability for fission with slow neutrons is greater A fission chain reaction produces intermediate mass fragments which are highly radioactive and produce further energy by their radioactive decay Some of them produce neutrons called delayed neutrons which contribute to the fission chain reaction The power output of nuclear reactors is adjusted by the location of control rods containing elements that strongly absorb neutrons e g boron cadmium or hafnium in the reactor core In nuclear bombs the reaction is uncontrolled and the large amount of energy released creates a nuclear explosion Nuclear weapons edit The Little Boy gun type atomic bomb dropped on Hiroshima on August 6 1945 was made of highly enriched uranium with a large tamper The nominal spherical critical mass for an untampered 235U nuclear weapon is 56 kilograms 123 lb 4 which would form a sphere 17 32 centimetres 6 82 in in diameter The material must be 85 or more of 235U and is known as weapons grade uranium though for a crude and inefficient weapon 20 enrichment is sufficient called weapon s usable Even lower enrichment can be used but this results in the required critical mass rapidly increasing Use of a large tamper implosion geometries trigger tubes polonium triggers tritium enhancement and neutron reflectors can enable a more compact economical weapon using one fourth or less of the nominal critical mass though this would likely only be possible in a country that already had extensive experience in engineering nuclear weapons Most modern nuclear weapon designs use plutonium 239 as the fissile component of the primary stage 5 6 however HEU highly enriched uranium in this case uranium that is 20 or more 235U is frequently used in the secondary stage as an ignitor for the fusion fuel Source Average energyreleased MeV 3 Instantaneously released energyKinetic energy of fission fragments 169 1Kinetic energy of prompt neutrons 4 8Energy carried by prompt g rays 7 0Energy from decaying fission productsEnergy of b particles 6 5Energy of delayed g rays 6 3Energy released when those prompt neutrons which do not re produce fission are captured 8 8Total energy converted into heat in an operating thermal nuclear reactor 202 5Energy of anti neutrinos 8 8Sum 211 3Natural decay chain editU 92 235 7 038 10 8 y a Th 90 231 25 52 h b Pa 91 231 3 276 10 4 y a Ac 89 227 21 773 y 98 62 b Th 90 227 18 718 d a 21 773 y 1 38 a Fr 87 223 21 8 min b Ra 88 223 11 434 d a Rn 86 219 Rn 86 219 3 96 s a Po 84 215 1 778 ms 99 99 a Pb 82 211 36 1 min b 1 778 ms 2 3 10 4 b At 85 215 0 10 ms a Bi 83 211 2 13 min 99 73 a Tl 81 207 4 77 min b 2 13 min 0 27 b Po 84 211 0 516 s a Pb stable 82 207 displaystyle begin array r ce 235 92 U gt alpha 7 038 times 10 8 ce y 231 90 Th gt beta 25 52 ce h 231 91 Pa gt alpha 3 276 times 10 4 ce y 227 89 Ac begin Bmatrix ce gt 98 62 beta 21 773 ce y 227 90 Th gt alpha 18 718 ce d ce gt 1 38 alpha 21 773 ce y 223 87 Fr gt beta 21 8 ce min end Bmatrix ce 223 88 Ra gt alpha 11 434 ce d 219 86 Rn ce 219 86 Rn gt alpha 3 96 ce s 215 84 Po begin Bmatrix ce gt 99 99 alpha 1 778 ce ms 211 82 Pb gt beta 36 1 ce min ce gt 2 3 times 10 4 beta 1 778 ce ms 215 85 At gt alpha 0 10 ce ms end Bmatrix ce 211 83 Bi begin Bmatrix ce gt 99 73 alpha 2 13 ce min 207 81 Tl gt beta 4 77 ce min ce gt 0 27 beta 2 13 ce min 211 84 Po gt alpha 0 516 ce s end Bmatrix ce 207 82 Pb stable end array nbsp Uses editUranium 235 has many uses such as fuel for nuclear power plants and in nuclear weapons such as nuclear bombs Some artificial satellites such as the SNAP 10A and the RORSATs were powered by nuclear reactors fueled with uranium 235 7 8 References edit Standard Reaction 235U n f www nds iaea org IAEA Retrieved 4 May 2020 Some Physics of Uranium UIC com au Archived from the original on July 17 2007 Retrieved 2009 01 18 a href Template Cite web html title Template Cite web cite web a CS1 maint bot original URL status unknown link a b Nuclear fission and fusion and neutron interactions National Physical Laboratory Archive FAS Nuclear Weapons Design FAQ Archived from the original on 1999 05 07 Retrieved 2010 09 02 Nuclear Weapon Design Federation of American Scientists Archived from the original on 2008 12 26 Retrieved 2016 06 04 Miner William N Schonfeld Fred W 1968 Plutonium In Clifford A Hampel ed The Encyclopedia of the Chemical Elements New York NY Reinhold Book Corporation p 541 LCCN 68029938 Schmidt Glen February 2011 SNAP Overview radium 219 general background PDF American Nuclear Society Retrieved 27 August 2012 RORSAT Radar Ocean Reconnaissance Satellite daviddarling info External links editTable of Nuclides DOE Fundamentals handbook Nuclear Physics and Reactor theory Vol 1 Archived 2017 07 31 at the Wayback Machine Vol 2 Archived 2016 12 20 at the Wayback Machine Radionuclide Basics Uranium US EPA NLM Hazardous Substances Databank Uranium Radioactive The Miracle of U 235 Popular Mechanics January 1941 one of the earliest articles on U 235 for the general public Lighter uranium 234 Uranium 235 is an isotope of uranium Heavier uranium 236Decay product of protactinium 235neptunium 235plutonium 239 Decay chain of uranium 235 Decays to thorium 231 Retrieved from https en wikipedia org w index php title Uranium 235 amp oldid 1188517231, wikipedia, wiki, book, books, library,
