Uranium-235
(Redirected from
U235
)Decay mode Decay energy (MeV) | | |
| Alpha | 4.679 | |
|---|---|---|
| Isotopes of uranium Complete table of nuclides | ||
Uranium-235 (235U or U-235) is an
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
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
]
Fission properties
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 nuclei are bombarded with neutrons, one of the many fission reactions that it can undergo is the following (shown in the adjacent image):
research reactors and nuclear weapons
.
If at least one
nuclear bombs, the reaction is uncontrolled and the large amount of energy released creates a nuclear explosion
.
Nuclear weapons
The
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 energy released [MeV][3] |
|---|---|
| Instantaneously released energy | |
| Kinetic energy of fission fragments | 169.1 |
| Kinetic energy of prompt neutrons | 4.8 |
| Energy carried by prompt γ-rays | 7.0 |
| Energy from decaying fission products | |
| Energy of β− particles | 6.5 |
| Energy of delayed γ-rays | 6.3 |
| 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 chain
![{\displaystyle {\begin{array}{r}{\ce {^{235}_{92}U->[\alpha ][7.038\times 10^{8}\ {\ce {y}}]{^{231}_{90}Th}->[\beta ^{-}][25.52\ {\ce {h}}]{^{231}_{91}Pa}->[\alpha ][3.276\times 10^{4}\ {\ce {y}}]{^{227}_{89}Ac}}}{\begin{Bmatrix}{\ce {->[98.62\%\beta ^{-}][21.773\ {\ce {y}}]{^{227}_{90}Th}->[\alpha ][18.718\ {\ce {d}}]}}\\{\ce {->[1.38\%\alpha ][21.773\ {\ce {y}}]{^{223}_{87}Fr}->[\beta ^{-}][21.8\ {\ce {min}}]}}\end{Bmatrix}}{\ce {^{223}_{88}Ra->[\alpha ][11.434\ {\ce {d}}]{^{219}_{86}Rn}}}\\{\ce {^{219}_{86}Rn->[\alpha ][3.96\ {\ce {s}}]{^{215}_{84}Po}}}{\begin{Bmatrix}{\ce {->[99.99\%\alpha ][1.778\ {\ce {ms}}]{^{211}_{82}Pb}->[\beta ^{-}][36.1\ {\ce {min}}]}}\\{\ce {->[2.3\times 10^{-4}\%\beta ^{-}][1.778\ {\ce {ms}}]{^{215}_{85}At}->[\alpha ][0.10\ {\ce {ms}}]}}\end{Bmatrix}}{\ce {^{211}_{83}Bi}}{\begin{Bmatrix}{\ce {->[99.73\%\alpha ][2.13\ {\ce {min}}]{^{207}_{81}Tl}->[\beta ^{-}][4.77\ {\ce {min}}]}}\\{\ce {->[0.27\%\beta ^{-}][2.13\ {\ce {min}}]{^{211}_{84}Po}->[\alpha ][0.516\ {\ce {s}}]}}\end{Bmatrix}}{\ce {^{207}_{82}Pb_{(stable)}}}\end{array}}}](https://wikimedia.org/api/rest_v1/media/math/render/svg/da2e321e70c54cd68c88b0abb6a8286b29b18b5a)
Uses
Uranium-235 has many uses such as fuel for nuclear power plants and in nuclear weapons such as
References
- ^ "#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.
{{cite web}}: CS1 maint: unfit URL (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.
- 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
- Table 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