Isotopes of zirconium

Naturally occurring zirconium (Zr) is composed of four stable isotopes (of which one may in the future be found radioactive), and one very long-lived radioisotope (⁹⁶Zr), a primordial nuclide that decays via double beta decay with an observed half-life of 2.0×10¹⁹ years; it can also undergo single beta decay, which is not yet observed, but the theoretically predicted value of t_1/2 is 2.4×10²⁰ years. The second most stable radioisotope is ⁹³Zr, which has a half-life of 1.53 million years. Twenty-seven other radioisotopes have been observed. All have half-lives less than a day except for ⁹⁵Zr (64.02 days), ⁸⁸Zr (63.4 days), and ⁸⁹Zr (78.41 hours). The primary decay mode is electron capture for isotopes lighter than ⁹²Zr, and the primary mode for heavier isotopes is beta decay.

Zirconium is the heaviest element that can be formed from symmetric fusion, from either ⁴⁵Sc, or ⁴⁶Ca producing ⁹⁰Zr (after two beta-plus decays from ⁹⁰Mo) and ⁹²Zr respectively. All heavier elements are formed either through asymmetric fusion or during the collapse of supernovae. As most of these are energy-absorbing processes, most nuclides of elements heavier than zirconium are theoretically unstable to spontaneous fission, although in many cases, the half-life for this is too long to have been observed. See list of nuclides for a tabulation.

Relative atomic mass: 91.224(2).

Zirconium-89

⁸⁹Zr is a radioisotope of zirconium with a half-life of 78.41 hours. It is produced by proton irradiation of natural yttrium-89. Its most prominent gamma photon has an energy of 909 keV.

Zirconium-89 is employed in specialized diagnostic applications using positron emission tomography imaging, for example, with zirconium-89 labeled antibodies (immuno-PET). For a decay table, see

Zirconium-93

Yield, % per fission

	Thermal	Fast	14 MeV
232Th	not fissile	6.70 ± 0.40	5.58 ± 0.16
233U	6.979 ± 0.098	6.94 ± 0.07	5.38 ± 0.32
235U	6.346 ± 0.044	6.25 ± 0.04	5.19 ± 0.31
238U	not fissile	4.913 ± 0.098	4.53 ± 0.13
239Pu	3.80 ± 0.03	3.82 ± 0.03	3.0 ± 0.3
241Pu	2.98 ± 0.04	2.98 ± 0.33	?

⁹³Zr is a radioisotope of zirconium with a half-life of 1.53 million years, decaying with a low-energy beta particle to niobium-93m, which decays with a halflife of 14 years and a low-energy gamma ray to ordinary ⁹³Nb. It is one of only 7 long-lived fission products. The low specific activity and low energy of its radiations limit the radioactive hazards of this isotope.

Nuclear fission produces it at a fission yield of 6.3% (thermal neutron fission of ²³⁵U), on a par with the other most abundant fission products. Nuclear reactors usually contain large amounts of zirconium as fuel rod cladding (see zircaloy), and neutron irradiation of ⁹²Zr also produces some ⁹³Zr, though this is limited by ⁹²Zr's low neutron capture cross section of 0.22 barns.

⁹³Zr also has a low neutron capture cross section of 0.7 barns. Most fission zirconium consists of other isotopes; the other isotope with a significant neutron absorption cross section is ⁹¹Zr with a cross section of 1.24 barns. ⁹³Zr is a less attractive candidate for disposal by nuclear transmutation than are Tc-99 and I-129. Mobility in soil is relatively low, so that geological disposal may be an adequate solution.

Table

nuclide symbol	Z(p)	N(n)	isotopic mass (u)	half-life	decay mode(s)	daughter isotope(s)	nuclear spin	representative isotopic composition (mole fraction)	range of natural variation (mole fraction)
	excitation energy
78Zr	40	38	77.95523(54)#	50# ms [>170 ns]			0+
79Zr	40	39	78.94916(43)#	56(30) ms	β+, p	78Sr	5/2+#
					β+	79Y
80Zr	40	40	79.9404(16)	4.6(6) s	β+	80Y	0+
81Zr	40	41	80.93721(18)	5.5(4) s	β+ (>99.9%)	81Y	(3/2−)#
					β+, p (<.1%)	80Sr
82Zr	40	42	81.93109(24)#	32(5) s	β+	82Y	0+
83Zr	40	43	82.92865(10)	41.6(24) s	β+ (>99.9%)	83Y	(1/2−)#
					β+, p (<.1%)	82Sr
84Zr	40	44	83.92325(21)#	25.9(7) min	β+	84Y	0+
85Zr	40	45	84.92147(11)	7.86(4) min	β+	85Y	7/2+
85mZr	292.2(3) keV			10.9(3) s	IT (92%)	85Zr	(1/2−)
					β+ (8%)	85Y
86Zr	40	46	85.91647(3)	16.5(1) h	β+	86Y	0+
87Zr	40	47	86.914816(9)	1.68(1) h	β+	87Y	(9/2)+
87mZr	335.84(19) keV			14.0(2) s	IT	87Zr	(1/2)−
88Zr	40	48	87.910227(11)	83.4(3) d	EC	88Y	0+
89Zr	40	49	88.908890(4)	78.41(12) h	β+	89Y	9/2+
89mZr	587.82(10) keV			4.161(17) min	IT (93.77%)	89Zr	1/2−
					β+ (6.23%)	89Y
90Zr	40	50	89.9047044(25)	Stable			0+	0.5145(40)
90m1Zr	2319.000(10) keV			809.2(20) ms	IT	90Zr	5-
90m2Zr	3589.419(16) keV			131(4) ns			8+
91Zr	40	51	90.9056458(25)	Stable			5/2+	0.1122(5)
91mZr	3167.3(4) keV			4.35(14) µs			(21/2+)
92Zr	40	52	91.9050408(25)	Stable			0+	0.1715(8)
93Zr	40	53	92.9064760(25)	1.53(10)×106 y	β−	93Nb	5/2+
94Zr	40	54	93.9063152(26)	Observationally Stable			0+	0.1738(28)
95Zr	40	55	94.9080426(26)	64.032(6) d	β−	95Nb	5/2+
96Zr	40	56	95.9082734(30)	20(4)×1018 y	β−β−	96Mo	0+	0.0280(9)
97Zr	40	57	96.9109531(30)	16.744(11) h	β−	97mNb	1/2+
98Zr	40	58	97.912735(21)	30.7(4) s	β−	98Nb	0+
99Zr	40	59	98.916512(22)	2.1(1) s	β−	99mNb	1/2+
100Zr	40	60	99.91776(4)	7.1(4) s	β−	100Nb	0+
101Zr	40	61	100.92114(3)	2.3(1) s	β−	101Nb	3/2+
102Zr	40	62	101.92298(5)	2.9(2) s	β−	102Nb	0+
103Zr	40	63	102.92660(12)	1.3(1) s	β−	103Nb	(5/2−)
104Zr	40	64	103.92878(43)#	1.2(3) s	β−	104Nb	0+
105Zr	40	65	104.93305(43)#	0.6(1) s	β− (>99.9%)	105Nb
					β−, n (<.1%)	104Nb
106Zr	40	66	105.93591(54)#	200# ms [>300 ns]	β−	106Nb	0+
107Zr	40	67	106.94075(32)#	150# ms [>300 ns]	β−	107Nb
108Zr	40	68	107.94396(64)#	80# ms [>300 ns]	β−	108Nb	0+
109Zr	40	69	108.94924(54)#	60# ms [>300 ns]
110Zr	40	70	109.95287(86)#	30# ms [>300 ns]			0+

Notes

• 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.
• 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

• Isotope masses from:
• Isotopic compositions and standard atomic masses from:
• Half-life, spin, and isomer data selected from the following sources. See editing notes on this article's talk page.

Isotopes of yttrium	Isotopes of zirconium	Isotopes of niobium
Table of nuclides