Isotopes of uranium

Actinides				Half-life	Fission products
²⁴⁴Cm	²⁴¹Pu ^f	²⁵⁰Cf	²⁴³Cm^f	10–30 y	¹³⁷Cs	⁹⁰Sr	⁸⁵Kr
²³²U ^f		²³⁸Pu	f is for fissile	69–90 y			¹⁵¹Sm nc➔
4n	²⁴⁹Cf ^f	²⁴²Am^f	f is for fissile	141–351	No fission product has half-life 10² to 2×10⁵ years
4n	²⁴¹Am		²⁵¹Cf ^f	431–898
²⁴⁰Pu	²²⁹Th	²⁴⁶Cm	²⁴³Am	5–7 ky
4n	²⁴⁵Cm^f	²⁵⁰Cm	²³⁹Pu ^f	8–24 ky
	²³³U ^f	²³⁰Th	²³¹Pa	32–160
	4n+1	²³⁴U	4n+3	211–290	⁹⁹Tc		¹²⁶Sn	⁷⁹Se
²⁴⁸Cm	4n+1	²⁴²Pu		340–373	Long-lived fission products
	²³⁷Np	4n+2		1–2 My	⁹³Zr	¹³⁵Cs nc➔
²³⁶U	4n+1		²⁴⁷Cm^f	6–23 My		¹⁰⁷Pd	¹²⁹I
²⁴⁴Pu				80 My	>7%	>5%	>1%	>.1%
²³²Th		²³⁸U	²³⁵U ^f	0.7–12 Gy	fission product yield

Uranium (U) is a naturally occurring radioactive element that has no stable isotopes but two primordial isotopes (uranium-238 and uranium-235) that have long half-life and are found in appreciable quantity in the Earth's crust, along with the decay product uranium-234. The average atomic mass of natural uranium is 238.02891(3) u. Other isotopes such as uranium-232 have been produced in breeder reactors.

Naturally occurring uranium is composed of three major isotopes, uranium-238 (99.28% natural abundance), uranium-235 (0.71%), and uranium-234 (0.0054%). All three isotopes are radioactive, creating radioisotopes, with the most abundant and stable being uranium-238 with a half-life of 4.4683×10⁹ years (close to the age of the Earth), uranium-235 with a half-life of 7.038×10⁸ years, and uranium-234 with a half-life of 2.48×10⁵ years.^[1]

Uranium-238 is an α emitter, decaying through the 18-member uranium series into lead-206. The decay series of uranium-235 (historically called actino-uranium) has 15 members that ends in lead-207. The constant rates of decay in these series makes comparison of the ratios of parent to daughter elements useful in radiometric dating. Uranium-233 is made from thorium-232 by neutron bombardment.

The isotope uranium-235 is important for both nuclear reactors and nuclear weapons because it is the only isotope existing in nature to any appreciable extent that is fissile, that is, can be broken apart by thermal neutrons. The isotope uranium-238 is also important because it absorbs neutrons to produce a radioactive isotope that subsequently decays to the isotope plutonium-239, which also is fissile.

1 Uranium-232
2 Uranium-239
3 Table
- 3.1 Notes
4 References

Uranium-232

Isotopes of uranium Full table
General
Name, symbol	Isotopes of uranium,²³²U
Neutrons	140
Protons	92
Nuclide data
Natural abundance	syn
Half-life	68.9 years
Parent isotopes	²³⁶Pu (α) ²³²Np (β⁺) ²³²Pa (β⁻)
Decay products	²²⁸Th

Actinides				Half-life	Fission products
²⁴⁴Cm	²⁴¹Pu ^f	²⁵⁰Cf	²⁴³Cm^f	10–30 y	¹³⁷Cs	⁹⁰Sr	⁸⁵Kr
²³²U ^f		²³⁸Pu	f is for fissile	69–90 y			¹⁵¹Sm nc➔
4n	²⁴⁹Cf ^f	²⁴²Am^f	f is for fissile	141–351	No fission product has half-life 10² to 2×10⁵ years
4n	²⁴¹Am		²⁵¹Cf ^f	431–898
²⁴⁰Pu	²²⁹Th	²⁴⁶Cm	²⁴³Am	5–7 ky
4n	²⁴⁵Cm^f	²⁵⁰Cm	²³⁹Pu ^f	8–24 ky
	²³³U ^f	²³⁰Th	²³¹Pa	32–160
	4n+1	²³⁴U	4n+3	211–290	⁹⁹Tc		¹²⁶Sn	⁷⁹Se
²⁴⁸Cm	4n+1	²⁴²Pu		340–373	Long-lived fission products
	²³⁷Np	4n+2		1–2 My	⁹³Zr	¹³⁵Cs nc➔
²³⁶U	4n+1		²⁴⁷Cm^f	6–23 My		¹⁰⁷Pd	¹²⁹I
²⁴⁴Pu				80 My	>7%	>5%	>1%	>.1%
²³²Th		²³⁸U	²³⁵U ^f	0.7–12 Gy	fission product yield

Uranium 232 (232
92U
140, 232
U, U-232) is an isotope of uranium. It has a half-life of 68.9 years and is a side product in the thorium cycle. It has been cited as an obstacle to nuclear proliferation using ²³³U as the fissile material, because the intense gamma radiation of ²³²U's decay products makes the ²³³U contaminated with it more difficult to handle.

Production of ²³³U (through the irradiation of ²³³Th) invariably produces small amounts of ²³²U as an impurity, because of parasitic (n,2n) reactions on uranium-233 itself, or on protactinium-233:

²³²Th (n,γ) ²³³Th (β−) ²³³Pa (β−) ²³³U (n,2n) ²³²U

²³²Th (n,γ) ²³³Th (β−) ²³³Pa (n,2n) ²³²Pa (β−) ²³²U

The decay chain of ²³²U quickly yields strong gamma radiation emitters:

²³²U (α, 68.9 years)

²²⁸Th (α, 1.9 year)

²²⁴Ra (α, 3.6 day, 0.24 MeV) (at this point, the decay chain is identical to that of ²³²Th)

²²⁰Rn (α, 55 s, 0.54 MeV)

²¹⁶Po (α, 0.15 s)

²¹²Pb (β−, 10.64 h)

²¹²Bi (α, 61 s, 0.78 MeV)

²⁰⁸Tl (β−, 3 m, 2.6 MeV)

²⁰⁸Pb (stable)

This makes manual handling in a glove box with only light shielding (as commonly done with plutonium) too hazardous, (except possibly in a short period immediately following chemical separation of the uranium from thorium-228, radium-224, radon-220, and polonium) and instead requiring remote manipulation for fuel fabrication.

Unusually for an isotope with even mass number, ²³²U has a significant neutron absorption cross section for fission (thermal neutrons 75 barns (b), resonance integral 380 b) as well as for neutron capture (thermal 73 b, resonance integral 280 b).

Lighter: uranium-231	Isotopes of uranium is an isotope of uranium	Heavier: uranium-233
Decay product of: plutonium-236 (α) neptunium-232 (β⁺) protactinium-232 (β⁻)	Decay chain of Isotopes of uranium	Decays to: thorium-228 (α)

Uranium-239

Isotopes of uranium Full table
General
Name, symbol	U-239,²³⁹U
Neutrons	147
Protons	92
Nuclide data
Natural abundance	syn
Half-life	23.45 mins
Decay products	²³⁹Np
Decay mode	Decay energy
Beta decay 20%	1.28 MeV
Beta decay 80%	1.21 MeV

Uranium-239 is an isotope of uranium. It is usually produced by exposing ²³⁸U to neutron radiation in a nuclear reactor. ²³⁹U has a half-life of about 23.45 minutes and decays into neptunium-239 through beta decay, with a total decay energy of about 1.29 Mev.^[2]. The most common gamma decay at 74.660 kev accounts for the difference in the two major channels of beta emission energy, at 1.28 and 1.21 Mev.^[3]

²³⁹Np further decays to plutonium-239, in a second important step which ultimately produces fissile ²³⁹Pu (used in weapons and for nuclear power), from ²³⁸U in reactors.

Lighter: Uranium-238	Isotopes of uranium is an isotope of Uranium	Heavier: Uranium-240
Decay product of: Protactinium-239 (β-)	Decay chain of Isotopes of uranium	Decays to: Neptunium-239 (β-)

Table

nuclide symbol	historic name	Z(p)	N(n)	isotopic mass (u)	half-life	decay mode(s)^[4]^{[n 1]}	daughter isotope(s)^{[n 2]}	nuclear spin	representative isotopic composition (mole fraction)	range of natural variation (mole fraction)
nuclide symbol	historic name	excitation energy			half-life	decay mode(s)^[4]^{[n 1]}	daughter isotope(s)^{[n 2]}	nuclear spin	representative isotopic composition (mole fraction)	range of natural variation (mole fraction)
²¹⁷U		92	125	217.02437(9)	26(14) ms [16(+21-6) ms]			1/2-#
²¹⁸U		92	126	218.02354(3)	6(5) ms	α	²¹⁴Th	0+
²¹⁹U		92	127	219.02492(6)	55(25) ms [42(+34-13) ms]	α	²¹⁵Th	9/2+#
²²⁰U		92	128	220.02472(22)#	60# ns	α	²¹⁶Th	0+
²²⁰U		92	128	220.02472(22)#	60# ns	β⁺ (rare)	²²⁰Pa	0+
²²¹U		92	129	221.02640(11)#	700# ns	α	²¹⁷Th	9/2+#
²²¹U		92	129	221.02640(11)#	700# ns	β⁺ (rare)	²²¹Pa	9/2+#
²²²U		92	130	222.02609(11)#	1.4(7) ms [1.0(+10-4) ms]	α	²¹⁸Th	0+
²²²U		92	130	222.02609(11)#	1.4(7) ms [1.0(+10-4) ms]	β⁺ (10⁻⁶%)	²²²Pa	0+
²²³U		92	131	223.02774(8)	21(8) ms [18(+10-5) ms]	α	²¹⁹Th	7/2+#
²²⁴U		92	132	224.027605(27)	940(270) ms	α	²²⁰Th	0+
²²⁵U		92	133	225.02939#	61(4) ms	α	²²¹Th	(5/2+)#
²²⁶U		92	134	226.029339(14)	269(6) ms	α	²²²Th	0+
²²⁷U		92	135	227.031156(18)	1.1(1) min	α	²²³Th	(3/2+)
²²⁷U		92	135	227.031156(18)	1.1(1) min	β⁺ (.001%)	²²⁷Pa	(3/2+)
²²⁸U		92	136	228.031374(16)	9.1(2) min	α (95%)	²²⁴Th	0+
²²⁸U		92	136	228.031374(16)	9.1(2) min	EC (5%)	²²⁸Pa	0+
²²⁹U		92	137	229.033506(6)	58(3) min	β⁺ (80%)	²²⁹Pa	(3/2+)
²²⁹U		92	137	229.033506(6)	58(3) min	α (20%)	²²⁵Th	(3/2+)
²³⁰U		92	138	230.033940(5)	20.8 d	α	²²⁶Th	0+
						SF (1.4×10⁻¹⁰%)	(various)
						β⁺β⁺ (rare)	²³⁰Th
²³¹U		92	139	231.036294(3)	4.2(1) d	EC	²³¹Pa	(5/2)(+#)
²³¹U		92	139	231.036294(3)	4.2(1) d	α (.004%)	²²⁷Th	(5/2)(+#)
²³²U		92	140	232.0371562(24)	68.9(4) y	α	²²⁸Th	0+
						CD (8.9×10⁻¹⁰%)	²⁰⁸Pb ²⁴Ne
						CD (5×10⁻¹²%)	²⁰⁴Hg ²⁸Mg
						SF (10⁻¹²%)	(various)
²³³U		92	141	233.0396352(29)	1.592(2)×10⁵ y	α	²²⁹Th	5/2+
						SF (6×10⁻⁹%)	(various)
						CD (7.2×10⁻¹¹%)	²⁰⁹Pb ²⁴Ne
						CD (1.3×10⁻¹³%)	²⁰⁵Hg ²⁸Mg
²³⁴U^{[n 3]}^{[n 4]}	Uranium II	92	142	234.0409521(20)	2.455(6)×10⁵ y	α	²³⁰Th	0+	[0.000054(5)]^{[n 5]}	0.000050- 0.000059
						SF (1.73×10⁻⁹%)	(various)
						CD (1.4×10⁻¹¹%)	²⁰⁶Hg ²⁸Mg
						CD (9×10⁻¹²%)	¹⁸⁴Hf ²⁶Ne ²⁴Ne
^234mU		1421.32(10) keV			33.5(20) ms			6-
²³⁵U^{[n 6]}^{[n 7]}^{[n 8]}	Actin Uranium Actino-Uranium	92	143	235.0439299(20)	7.04(1)×10⁸ y	α	²³¹Th	7/2-	[0.007204(6)]	0.007198- 0.007207
						SF (7×10⁻⁹%)	(various)
						CD (8×10⁻¹⁰%)	¹⁸⁶Hf ²⁵Ne ²⁴Ne
^235mU		0.0765(4) keV			~26 min	IT	²³⁵U	1/2+
²³⁶U		92	144	236.045568(2)	2.342(3)×10⁷ y	α	²³²Th	0+
²³⁶U		92	144	236.045568(2)	2.342(3)×10⁷ y	SF (9.6×10⁻⁸%)	(various)	0+
^236m1U		1052.89(19) keV			100(4) ns			(4)-
^236m2U		2750(10) keV			120(2) ns			(0+)
²³⁷U		92	145	237.0487302(20)	6.75(1) d	β^-	²³⁷Np	1/2+
²³⁸U^{[n 6]}^{[n 4]}^{[n 7]}	Uranium I	92	146	238.0507882(20)	4.468(3)×10⁹ y	α	²³⁴Th	0+	[0.992742(10)]	0.992739- 0.992752
						SF (5.45×10⁻⁵%)	(various)
						β^-β^- (2.19×10⁻¹⁰%)	²³⁸Pu
^238mU		2557.9(5) keV			280(6) ns			0+
²³⁹U		92	147	239.0542933(21)	23.45(2) min	β^-	²³⁹Np	5/2+
^239m1U		20(20)# keV			>250 ns			(5/2+)
^239m2U		133.7990(10) keV			780(40) ns			1/2+
²⁴⁰U		92	148	240.056592(6)	14.1(1) h	β^-	²⁴⁰Np	0+
²⁴⁰U		92	148	240.056592(6)	14.1(1) h	α (10⁻¹⁰%)	²³⁶Th	0+
²⁴¹U		92	149	241.06033(32)#	5# min	β^-	²⁴¹Np	7/2+#
²⁴²U		92	150	242.06293(22)#	16.8(5) min	β^-	²⁴²Np	0+

^ Abbreviations:
CD: Cluster decay
EC: Electron capture
IT: Isomeric transition
SF: Spontaneous fission
^ Bold for stable isotopes, bold italics for nearly-stable isotopes (half-life longer than the age of the universe)
^ Used in uranium-thorium dating
^ ^a ^b Used in uranium-uranium dating
^ Intermediate decay product of ²³⁸U
^ ^a ^b Primordial radionuclide
^ ^a ^b Used in Uranium-lead dating
^ Important in nuclear reactors

Notes

Evaluated isotopic composition is for most but not all commercial samples.
The precision of the isotope abundances and atomic mass is limited through variations. The given ranges should be applicable to any normal terrestrial material.
Geologically exceptional samples are known in which the isotopic composition lies outside the reported range. The uncertainty in the atomic mass may exceed the stated value for such specimens.
Commercially available materials may have been subjected to an undisclosed or inadvertent isotopic fractionation. Substantial deviations from the given mass and composition can occur.
Values marked # are not purely derived from experimental data, but at least partly from systematic trends. Spins with weak assignment arguments are enclosed in parentheses.
Uncertainties are given in concise form in parentheses after the corresponding last digits. Uncertainty values denote one standard deviation, except isotopic composition and standard atomic mass from IUPAC which use expanded uncertainties.

References

^ Seaborg, Encyclopedia of the Chemical Elements (1968), page 777
^ CRC Handbook, 57th Ed. p. B-345
^ CRC Handbook, 57th Ed. p. B-423
^ http://www.nucleonica.net/unc.aspx

Isotope masses from:
- G. Audi, A. H. Wapstra, C. Thibault, J. Blachot and O. Bersillon (2003). "The NUBASE evaluation of nuclear and decay properties". Nuclear Physics A 729: 3–128. Bibcode 2003NuPhA.729....3A. doi:10.1016/j.nuclphysa.2003.11.001. http://www.nndc.bnl.gov/amdc/nubase/Nubase2003.pdf.
Isotopic compositions and standard atomic masses from:
- J. R. de Laeter, J. K. Böhlke, P. De Bièvre, H. Hidaka, H. S. Peiser, K. J. R. Rosman and P. D. P. Taylor (2003). "Atomic weights of the elements. Review 2000 (IUPAC Technical Report)". Pure and Applied Chemistry 75 (6): 683–800. doi:10.1351/pac200375060683. http://www.iupac.org/publications/pac/75/6/0683/pdf/.
- M. E. Wieser (2006). "Atomic weights of the elements 2005 (IUPAC Technical Report)". Pure and Applied Chemistry 78 (11): 2051–2066. doi:10.1351/pac200678112051. http://iupac.org/publications/pac/78/11/2051/pdf/. Lay summary.
Half-life, spin, and isomer data selected from the following sources. See editing notes on this article's talk page.
- G. Audi, A. H. Wapstra, C. Thibault, J. Blachot and O. Bersillon (2003). "The NUBASE evaluation of nuclear and decay properties". Nuclear Physics A 729: 3–128. Bibcode 2003NuPhA.729....3A. doi:10.1016/j.nuclphysa.2003.11.001. http://www.nndc.bnl.gov/amdc/nubase/Nubase2003.pdf.
- National Nuclear Data Center. "NuDat 2.1 database". Brookhaven National Laboratory. http://www.nndc.bnl.gov/nudat2/. Retrieved September 2005.
- N. E. Holden (2004). "Table of the Isotopes". In D. R. Lide. CRC Handbook of Chemistry and Physics (85th ed.). CRC Press. Section 11. ISBN 978-0849304859.

Isotopes of protactinium	Isotopes of uranium	Isotopes of neptunium
Index to isotope pages · Table of nuclides