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Uranium-231

Properties and data of the isotope 231U.

 

Uranium-231 is the short-lived radioisotope of the element Uranium, whose atomic nucleus has 139 neutrons in addition to the element-specific 92 protons, resulting in a mass number of 231: 231U.

See also: list of Uranium isotopes.

 

General data

Name of the isotope:Uranium-231; U-231Symbol:231UMass number A:231Atomic number Z:92 (= number of protons)Neutrons N:139Isotopic mass:231.0362923(29) u (atomic weight of Uranium-231)Nuclide mass:230.9858296 u (calculated nuclear mass without electrons)Mass excess:33.80606 MeVMass defect:1.888033968 u (per nucleus)Nuclear binding energy:1758.69231299 MeV (per nucleus)
7.61338664 MeV (average binding energy per nucleon)
Separation energy:SN = 5.880(5) MeV (first neutron)
SP = 5.657(4) MeV (first proton)
Half-life:4.2(1) dDecay constant λ:1.910127812389 × 10-6 s-1Spin and parity:(5/2-)Year of discovery:1949

 

Radioactive Decay

Half-life T½ = 4.2(1) d respectively 3.62880 × 105 seconds s.

Decay modeDaughterProbabilityDecay energyγ energy
(intensity)
α227Th0,004(1) %5,5763(17) MeV
EE231Paca. 100 %0,382(3) MeV

 

Uranium-231 radioactive decay cascade

 

Parent Nuclides

Direct parent isotopes are: 235Pu, 231Np.

 

Radiation Protection

The German Radiation Protection Ordinance, for example, specifies the following limit values for the isotope Uranium-231 (exemption limits, clearance values and other values as a radioactive or highly radioactive source of radiation (HASS)):

Isotope:U-231Exemption level:107 BqExemption level per gram:100 Bq/g
Unrestricted handling of solids and liquids.
Surface contamination:10 Bq cm-2Half-life:4.2 d

 

Isotones and Isobars

The following table shows the atomic nuclei that are isotonic (same neutron number N = 139) and isobaric (same nucleon number A = 231) with Uranium-231. Naturally occurring isotopes are marked in green; light green = naturally occurring radionuclides.

 

OZIsotone N = 139Isobar A = 231
83222Bi
84223Po
85224At
86225Rn
87226Fr231Fr
88227Ra231Ra
89228Ac231Ac
90229Th231Th
91230Pa231Pa
92231U231U
93232Np231Np
94233Pu231Pu
95234Am231Am
96235Cm
97236Bk
98237Cf

 

External data and identifiers

CAS:15700-08-0InChI Key:JFALSRSLKYAFGM-NOHWODKXSA-NSMILES:[231U]PubChem:ID 177622Adopted Levels, Gammas:NuDat 231U

 


Category: Isotopes

Last update: 26.11.2022



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