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Uranium-235 (235 U 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 has a half-life of 703.8 million years.
Most neutrons released by a fissioning atom of uranium-235 must impact other uranium-235 atoms to sustain the nuclear chain reaction. The concentration and amount of uranium-235 needed to achieve this is called a 'critical mass'. To be considered 'enriched', the uranium-235 fraction should be between 3% and 5%. [123]
Enriched uranium is a type of uranium in which the percent composition of uranium-235 (written 235 U) has been increased through the process of isotope separation.Naturally occurring uranium is composed of three major isotopes: uranium-238 (238 U with 99.2732–99.2752% natural abundance), uranium-235 (235 U, 0.7198–0.7210%), and uranium-234 (234 U, 0.0049–0.0059%).
Uranium-235 makes up about 0.72% of natural uranium. Unlike the predominant isotope uranium-238, it is fissile, i.e., it can sustain a fission chain reaction. It is the only fissile isotope that is a primordial nuclide or found in significant quantity in nature. Uranium-235 has a half-life of 703.8 million years.
The bond lengths are indicative of the presence of multiple bonding between the uranium and oxygen atoms. Since uranium(VI) has the electronic configuration of the preceding noble gas, radon, the electrons used in forming the U–O bonds are supplied by the oxygen atoms. The electrons are donated into empty atomic orbitals on the uranium atom ...
The fissile isotope uranium-235 fuels most nuclear reactors.When 235 U absorbs a thermal neutron, one of two processes can occur.About 85.5% of the time, it will fission; about 14.5% of the time, it will not fission, instead emitting gamma radiation and yielding 236 U. [1] [2] Thus, the yield of 236 U per 235 U+n reaction is about 14.5%, and the yield of fission products is about 85.5%.
Technetium-99 (99 Tc) is a major product of the fission of uranium-235 (235 U), making it the most common and most readily available isotope of technetium. One gram of technetium-99 produces 6.2 × 10 8 disintegrations per second (in other words, the specific activity of 99 Tc is 0.62 GBq/g). [28]
oxygen-26: 40 sodium-19: 40 oxygen-25: 50 nitrogen-24: 52 protactinium-219: 53 neon-34: 60 sodium-37: 60 protactinium-220m2: 69 actinium-217: 69 francium-215: 86 lead-196m1 <100 uranium-236m1: 100 bismuth-199m2: 100 oxygen-28: 100 curium-247m2: 100.6 actinium-218m: 103 francium-214m2: 103 bismuth-201m3: 105 lead-202m3: 107 francium-214m3: 108 ...