Uranium-237

Properties and data of the isotope ²³⁷U.

Contents

General Data

Radioactive Decay

Parent Nuclides

Isotones und Isobares

Literature

Uranium-237 is a radioisotope of the chemical element uranium, which has 145 neutrons in its atomic nucleus in addition to the element-specific 92 protons; the sum of the number of these atomic nucleus building blocks results in a mass number of 237.

The first observation of the isotope ²³⁷U was reported in a 1940 publication: A uranium dioxide sample was irradiated with fast neutrons produced by bombarding lithium with 3-MeV deuterons (nuclei of hydrogen-2). In this process, the nuclide uranium-237 was formed via the reaction ²³⁸U(n,2n)²³⁷U.

After chemical separation, β-decay curves were recorded, revealing an activity with a characteristic half-life of about 6.5 days, which could be unambiguously assigned to ²³⁷U [1].

See also: List of individual Uranium isotopes (and general data sources).

General data

Name of the isotope:Uranium-237; U-237Symbol:²³⁷U or 23792UMass number A:237 (= number of nucleons)Atomic number Z:92 (= number of protons)Neutrons N:145Nucleon pairing (Z - N):even - oddNuclear ratio (N/Z ratio):1.5760869565217 (= neutron-proton ratio)Neutron excess (N-Z):53Isotopic mass:237.0487283(13) u (atomic weight of Uranium-237)Nuclide mass:236.9982656 u (calculated nuclear mass without electrons)Mass excess:45.39012 MeVMass defect:1.927587464 u (per nucleus)Nuclear binding energy:1795.53615719 MeV (per nucleus)
7.57610193 MeV (average binding energy per nucleon)Separation energy:S_N = 5.1258(5) MeV (first neutron)
S_P = 7.233(14) MeV (first proton)Half-life:6.752(2) dDecay constant λ:1.188171513868 × 10^-6 s^-1Specific activity α:3.01912920771 × 10⁺¹⁵ Bq g^-1
81598.086694946 Ci g^-1Spin and parity:
(nuclear angular momentum)1/2+Year of discovery:1940

Radioactive Decay

Half-life T_½ = 6.752(2) d respectively 5.83373 × 10⁵ seconds s.

Decay mode	Daughter	Probability	Decay energy	γ energy (intensity)
β^-	²³⁷Np	100 %	0.5185(5) MeV

Parent Nuclides

Direct parent isotopes are: ²⁴¹Pu, ²³⁷Pa.

Nuclear Isomers

Nuclear isomers or excited states with the activation energy in keV related to the ground state.

Nuclear Isomer	Excitation Energy	Half-life	Spin
^237mU	274.0(10) keV	155(6) ns	(7/2)-

Isotones and Isobars

The following table shows the atomic nuclei that are isotonic (same neutron number N = 145) and isobaric (same nucleon number A = 237) with Uranium-237. Naturally occurring isotopes are marked in green; light green = naturally occurring radionuclides.

Z	Isotone N = 145	Isobar A = 237
87	²³²Fr
88	²³³Ra
89	²³⁴Ac
90	²³⁵Th	²³⁷Th
91	²³⁶Pa	²³⁷Pa
92	²³⁷U	²³⁷U
93	²³⁸Np	²³⁷Np
94	²³⁹Pu	²³⁷Pu
95	²⁴⁰Am	²³⁷Am
96	²⁴¹Cm	²³⁷Cm
97	²⁴²Bk	²³⁷Bk
98	²⁴³Cf	²³⁷Cf
99	²⁴⁴Es
100	²⁴⁵Fm
101	²⁴⁶Md

External data and identifiers

CAS:14269-75-1InChI Key:JFALSRSLKYAFGM-BJUDXGSMSA-NSMILES:[237U]PubChem:ID 237Adopted Levels, Gammas:NuDat 237U

Literature and References

[1] - Y. Nishina et al.:
Induced β-Activity of Uranium by Fast Neutrons.
In: Physical Review, 57, 1182, (1940), DOI 10.1103/PhysRev.57.1182.

[2] - Nagao Ikeda:
The discoveries of uranium 237 and symmetric fission - From the archival papers of Nishina and Kimura.
In: Proceedings of the Japan Academy, Series B, (2011), DOI 10.2183/pjab.87.371.

[3] - Hector Francisco Valdovinos et al.:
Rapid Quantification of ²³⁷U Specific Activity for Nuclear Forensics.
In: Industrial & Engineering Chemistry Research, 63, 1, (2024), DOI 10.1021/acs.iecr.3c03247.