Fission product yield

Long-lived fission products

Nuclide	t1⁄2	Yield	Q	βγ
	(Ma)	(%)	(keV)
99Tc	0.211	6.1385	294	β
126Sn	0.230	0.1084	4050	βγ
79Se	0.327	0.0447	151	β
135Cs	1.33	6.9110	269	β
93Zr	1.53	5.4575	91	βγ
107Pd	6.5	1.2499	33	β
129I	16.14	0.8410	194	βγ

Medium-lived
fission products

	t½ (year)	Yield (%)	Q (keV)	βγ
155Eu	4.76	0.0803	252	βγ
85Kr	10.76	0.2180	687	βγ
113mCd	14.1	0.0008	316	β
90Sr	28.9	4.505	2826	β
137Cs	30.23	6.337	1176	βγ
121mSn	43.9	0.00005	390	βγ
151Sm	88.8	0.5314	77	β

Nuclear fission splits a heavy nucleus such as uranium or plutonium into two lighter nuclei, which are called fission products. Yield refers to the fraction of a fission product produced per fission.

Yield can be broken down by:

1. Individual isotope
2. Chemical element spanning several isotopes of different mass number but same atomic number.
3. Nuclei of a given mass number regardless of atomic number. Known as "chain yield" because it represents a decay chain of beta decay.

Isotope and element yields will change as the fission products undergo beta decay, while chain yields do not change after completion of neutron emission by a few neutron-rich initial fission products (delayed neutrons), with half-life measured in seconds.

A few isotopes can be produced directly by fission, but not by beta decay because the would-be precursor with atomic number one less is stable and does not decay (atomic number grows by 1 during beta decay). Chain yields do not account for these "shadowed" isotopes; however, they have very low yields (less than a millionth as much as common fission products) because they are far less neutron-rich than the original heavy nuclei.

Yield is usually stated as percentage per fission, so that the total yield percentages sum to 200%. Less often, it is stated as percentage of all fission products, so that the percentages sum to 100%. Ternary fission, about 0.2–0.4% of fissions, also produces a third light nucleus such as helium-4 (90%) or tritium (7%).

Mass vs. yield curve

Fission product yields by mass for thermal neutron fission of U-235, Pu-239, a combination of the two typical of current nuclear power reactors, and U-233 used in the thorium fuel cycle

If a graph of the mass or mole yield of fission products against the atomic number of the fragments is drawn then it has two peaks, one in the area zirconium through to palladium and one at xenon through to neodymium. This is because the fission event causes the nucleus to split in an asymmetric manner, as nuclei closer to magic numbers are more stable.

Yield vs. Z - This is a typical distribution for the fission of uranium. Note that in the calculations used to make this graph the activation of fission products was ignored and the fission was assumed to occur in a single moment rather than a length of time. In this bar chart results are shown for different cooling times (time after fission).

Yield vs Z. Colors indicate fluoride volatility, which is important in nuclear reprocessing: Blue elements have volatile fluorides or are already volatile; green elements do not but have volatile chlorides; red elements have neither, but the elements themselves are volatile at very high temperatures. Yields at 10^0,1,2,3 years after fission, not considering later neutron capture, fraction of 100% not 200%. Beta decay Kr-85→Rb, Sr-90→Zr, Ru-106→Pd, Sb-125→Te, Cs-137→Ba, Ce-144→Nd, Sm-151→Eu, Eu-155→Gd visible.

Because of the stability of nuclei with even numbers of protons and/or neutrons the curve of yield against element is not a smooth curve. It tends to alternate.

In general, the higher the energy of the state that undergoes nuclear fission, the more likely a symmetric fission is, hence as the neutron energy increases and/or the energy of the fissile atom increases, the valley between the two peaks becomes more shallow; for instance, the curve of yield against mass for Pu-239 has a more shallow valley than that observed for U-235, when the neutrons are thermal neutrons. The curves for the fission of the later actinides tend to make even more shallow valleys. In extreme cases such as ²⁵⁹Fm, only one peak is seen.

Yield is usually expressed relative to number of fissioning nuclei, not the number of fission product nuclei, that is, yields should sum to 200%.

The table in the next section ("Ordered by yield") gives yields for notable radioactive (with half-lives greater than one year, plus iodine-131) fission products, and (the few most absorptive) neutron poison fission products, from thermal neutron fission of U-235 (typical of nuclear power reactors), computed from [1].

The yields in the table sum to only 45.5522%, including 34.8401% which have half-lives greater than one year:

t½ in years	Yield
1 to 5	2.7252%
10 to 100	12.5340%
2 to 300,000	6.1251%
1.5 to 16 million	13.4494%

The remainder and the unlisted 54.4478% decay with half-lives less than one year into nonradioactive nuclei.

This is before accounting for the effects of any subsequent neutron capture; e.g.:

• ¹³⁵Xe capturing a neutron and becoming nearly stable ¹³⁶Xe, rather than decaying to ¹³⁵Cs which is radioactive with a half-life of 2.3 million years
• Nonradioactive ¹³³Cs capturing a neutron and becoming ¹³⁴Cs, which is radioactive with a half-life of 2 years
• Many of the fission products with mass 147 or greater such as ¹⁴⁷Pm, ¹⁴⁹Sm, ¹⁵¹Sm, and ¹⁵⁵Eu have significant cross sections for neutron capture, so that one heavy fission product atom can undergo multiple successive neutron captures.

Besides fission products, the other types of radioactive products are

• plutonium containing ²³⁸Pu, ²³⁹Pu, ²⁴⁰Pu, ²⁴¹Pu, and ²⁴²Pu,
• minor actinides including ²³⁷Np, ²⁴¹Am, ²⁴³Am, curium isotopes, and perhaps californium
• reprocessed uranium containing ²³⁶U and other isotopes
• tritium
• activation products of neutron capture by the reactor or bomb structure or the environment

Fission products from U-235

Yield	Element	Isotope	Halflife	Comment
6.7896%	Caesium	133Cs → 134Cs	2.065 y	Neutron capture (29 barns) slowly converts stable 133Cs to 134Cs, which itself is low-yield because beta decay stops at 134Xe; can be further converted (140 barns) to 135Cs.
6.3333%	Iodine, xenon	135I → 135Xe	6.57 h	Most important neutron poison; neutron capture converts 10–50% of 135Xe to 136Xe; remainder decays (9.14h) to 135Cs (2.3 My).
6.2956%	Zirconium	93Zr	1.53 My	Long-lived fission product also produced by neutron activation in zircalloy cladding.
6.1%	Molybdenum	99Mo	65.94 h	Its daughter nuclide 99mTc is important in medical diagnosing.
6.0899%	Caesium	137Cs	30.17 y	Source of most of the decay heat from years to decades after irradiation, together with 90 Sr.
6.0507%	Technetium	99Tc	211 ky	Candidate for disposal by nuclear transmutation.
5.7518%	Strontium	90Sr	28.9 y	Source of much of the decay heat together with 137 Cs on the timespan of years to decades after irradiation. Formerly used in radioisotope thermoelectric generators.
2.8336%	Iodine	131I	8.02 d	Reason for the use of potassium iodide tablets after nuclear accidents or nuclear bomb explosions.
2.2713%	Promethium	147Pm	2.62 y	beta decays to very long lived Samarium-147 (half life>age of the universe); has seen some use in radioisotope thermoelectric generators
1.0888%	Samarium	149Sm	Observationally stable	2nd most significant neutron poison.
0.9%	Iodine	129I	15.7 My	Long-lived fission product. Candidate for disposal by nuclear transmutation.
0.4203%	Samarium	151Sm	90 y	Neutron poison; most will be converted to stable 152Sm.
0.3912%	Ruthenium	106Ru	373.6 d	ruthenium tetroxide is volatile and chemically aggressive; daughter nuclide 106 Rh decays quickly to stable 106 Pd
0.2717%	Krypton	85Kr	10.78 y	noble gas; has some uses in industry to detect fine cracks in materials via autoradiography
0.1629%	Palladium	107Pd	6.5 My	Long-lived fission product; hampers extraction of stable isotopes of platinum group metals for use due to chemical similarity.
0.0508%	Selenium	79Se	327 ky
0.0330%	Europium, gadolinium	155Eu → 155Gd	4.76 y	Both neutron poisons, most will be destroyed while fuel still in use.
0.0297%	Antimony	125Sb	2.76 y
0.0236%	Tin	126Sn	230 ky
0.0065%	Gadolinium	157Gd	stable	Neutron poison.
0.0003%	Cadmium	113mCd	14.1 y	Neutron poison, most will be destroyed while fuel still in use.

Yields at 10^0,1,2,3 years after fission, probably of Pu-239 not U-235 because left hump is shifted right, not considering later neutron capture, fraction of 100% not 200%. Beta decay Kr-85→Rb, Sr-90→Zr, Ru-106→Pd, Sb-125→Te, Cs-137→Ba, Ce-144→Nd, Sm-151→Eu, Eu-155→Gd visible.

Cumulative fission yields

Cumulative fission yields give the amounts of nuclides produced either directly in the fission or by decay of other nuclides.

Cumulative fission yields per fission for U-235 (%)

Product	Thermal fission yield	Fast fission yield	14-MeV fission yield
1 1H	0.00171 ± 0.00018	0.00269 ± 0.00044	0.00264 ± 0.00045
2 1H	0.00084 ± 0.00015	0.00082 ± 0.00012	0.00081 ± 0.00012
3 1H	0.0108 ± 0.0004	0.0108 ± 0.0004	0.0174 ± 0.0036
3 2He	0.0108 ± 0.0004	0.0108 ± 0.0004	0.0174 ± 0.0036
4 2He	0.1702 ± 0.0049	0.17 ± 0.0049	0.1667 ± 0.0088
85 35Br	1.304 ± 0.012	1.309 ± 0.043	1.64 ± 0.31
82 36Kr	0.000285 ± 0.000076	0.00044 ± 0.00016	0.038 ± 0.012
85 36Kr	0.286 ± 0.021	0.286 ± 0.026	0.47 ± 0.1
85m 36Kr	1.303 ± 0.012	1.307 ± 0.043	1.65 ± 0.31
90 38Sr	5.73 ± 0.13	5.22 ± 0.18	4.41 ± 0.18
95 40Zr	6.502 ± 0.072	6.349 ± 0.083	5.07 ± 0.19
94 41Nb	0.00000042 ± 0.00000011	2.90±0.770 × 10−8	0.00004 ± 0.000015
95 41Nb	6.498 ± 0.072	6.345 ± 0.083	5.07 ± 0.19
95m 41Nb	0.0702 ± 0.0067	0.0686 ± 0.0071	0.0548 ± 0.0072
92 42Mo	0 ± 0	0 ± 0	0 ± 0
94 42Mo	8.70 × 10−10 ± 3.20 × 10−10	0 ± 0	6.20 × 10−8 ± 2.50 × 10−8
96 42Mo	0.00042 ± 0.00015	0.000069 ± 0.000025	0.0033 ± 0.0015
99 42Mo	6.132 ± 0.092	5.8 ± 0.13	5.02 ± 0.13
99 43Tc	6.132 ± 0.092	5.8 ± 0.13	5.02 ± 0.13
103 44Ru	3.103 ± 0.084	3.248 ± 0.042	3.14 ± 0.11
106 44Ru	0.41 ± 0.011	0.469 ± 0.036	2.15 ± 0.59
106 45Rh	0.41 ± 0.011	0.469 ± 0.036	2.15 ± 0.59
121m 50Sn	0.00106 ± 0.00011	0.0039 ± 0.00091	0.142 ± 0.023
122 51Sb	0.000000366 ± 0.000000098	0.0000004 ± 0.00000014	0.00193 ± 0.00068
124 51Sb	0.000089 ± 0.000021	0.000112 ± 0.000034	0.027 ± 0.01
125 51Sb	0.026 ± 0.0014	0.067 ± 0.011	1.42 ± 0.42
132 52Te	4.276 ± 0.043	4.639 ± 0.065	3.85 ± 0.16
129 53I	0.706 ± 0.032	1.03 ± 0.26	1.59 ± 0.18
131 53I	2.878 ± 0.032	3.365 ± 0.054	4.11 ± 0.14
133 53I	6.59 ± 0.11	6.61 ± 0.13	5.42 ± 0.4
135 53I	6.39 ± 0.22	6.01 ± 0.18	4.8 ± 1.4
128 54Xe	0 ± 0	0 ± 0	0.00108 ± 0.00048
130 54Xe	0.000038 ± 0.0000098	0.000152 ± 0.000055	0.038 ± 0.014
131m 54Xe	0.0313 ± 0.003	0.0365 ± 0.0031	0.047 ± 0.0049
133 54Xe	6.6 ± 0.11	6.61 ± 0.13	5.57 ± 0.41
133m 54Xe	0.189 ± 0.015	0.19 ± 0.015	0.281 ± 0.049
135 54Xe	6.61 ± 0.22	6.32 ± 0.18	6.4 ± 1.8
135m 54Xe	1.22 ± 0.12	1.23 ± 0.13	2.17 ± 0.66
134 55Cs	0.0000121 ± 0.0000032	0.0000279 ± 0.0000073	0.0132 ± 0.0035
137 55Cs	6.221 ± 0.069	5.889 ± 0.096	5.6 ± 1.3
140 56Ba	6.314 ± 0.095	5.959 ± 0.048	4.474 ± 0.081
140 57La	6.315 ± 0.095	5.96 ± 0.048	4.508 ± 0.081
141 58Ce	5.86 ± 0.15	5.795 ± 0.081	4.44 ± 0.2
144 58Ce	5.474 ± 0.055	5.094 ± 0.076	3.154 ± 0.038
144 59Pr	5.474 ± 0.055	5.094 ± 0.076	3.155 ± 0.038
142 60Nd	6.30 × 10−9 ± 1.70 × 10−9	1.70 × 10−9 ± 4.80 × 10−10	0.0000137 ± 0.0000049
144 60Nd	5.475 ± 0.055	5.094 ± 0.076	3.155 ± 0.038
147 60Nd	2.232 ± 0.04	2.148 ± 0.028	1.657 ± 0.045
147 61Pm	2.232 ± 0.04	2.148 ± 0.028	1.657 ± 0.045
148 61Pm	5.00 × 10−8 ± 1.70 × 10−8	7.40 × 10−9 ± 2.50 × 10−9	0.0000013 ± 0.00000042
148m 61Pm	0.000000104 ± 0.000000039	1.78 × 10−8 ± 6.60 × 10−9	0.0000048 ± 0.0000018
149 61Pm	1.053 ± 0.021	1.064 ± 0.03	0.557 ± 0.09
151 61Pm	0.4204 ± 0.0071	0.431 ± 0.015	0.388 ± 0.061
148 62Sm	0.000000149 ± 0.000000041	2.43 × 10−8 ± 6.80 × 10−9	0.0000058 ± 0.0000018
150 62Sm	0.000061 ± 0.000022	0.0000201 ± 0.0000077	0.00045 ± 0.00018
151 62Sm	0.4204 ± 0.0071	0.431 ± 0.015	0.388 ± 0.061
153 62Sm	0.1477 ± 0.0071	0.1512 ± 0.0097	0.23 ± 0.015
151 63Eu	0.4204 ± 0.0071	0.431 ± 0.015	0.388 ± 0.061
152 63Eu	3.24 × 10−10 ± 8.50 × 10−11	0 ± 0	3.30 × 10−8 ± 1.10 × 10−8
154 63Eu	0.000000195 ± 0.000000064	4.00 × 10−8 ± 1.10 × 10−8	0.0000033 ± 0.0000011
155 63Eu	0.0308 ± 0.0013	0.044 ± 0.01	0.088 ± 0.014

Cumulative fission yield per fission for Pu-239 (%)

Product	Thermal fission yield	Fast fission yield	14-MeV fission yield
1 1H	0.00408 ± 0.00041	0.00346 ± 0.00057	-
2 1H	0.00135 ± 0.00019	0.00106 ± 0.00016	-
3 1H	0.0142 ± 0.0007	0.0142 ± 0.0007	-
3 2He	0.0142 ± 0.0007	0.0142 ± 0.0007	-
4 2He	0.2192 ± 0.009	0.219 ± 0.009	-
85 35Br	0.574 ± 0.026	0.617 ± 0.049	-
82 36Kr	0.00175 ± 0.0006	0.00055 ± 0.0002	-
85 36Kr	0.136 ± 0.014	0.138 ± 0.017	-
85m 36Kr	0.576 ± 0.026	0.617 ± 0.049	-
90 38Sr	2.013 ± 0.054	2.031 ± 0.057	-
95 40Zr	4.949 ± 0.099	4.682 ± 0.098	-
94 41Nb	0.0000168 ± 0.0000045	0.00000255 ± 0.00000069	-
95 41Nb	4.946 ± 0.099	4.68 ± 0.098	-
95m 41Nb	0.0535 ± 0.0066	0.0506 ± 0.0062	-
92 42Mo	0 ± 0	0 ± 0	-
94 42Mo	3.60 × 10−8 ± 1.30 × 10−8	4.80 × 10−9 ± 1.70 × 10−9	-
96 42Mo	0.0051 ± 0.0018	0.0017 ± 0.00062	-
99 42Mo	6.185 ± 0.056	5.82 ± 0.13	-
99 43Tc	6.184 ± 0.056	5.82 ± 0.13	-
103 44Ru	6.948 ± 0.083	6.59 ± 0.16	-
106 44Ru	4.188 ± 0.092	4.13 ± 0.24	-
106 45Rh	4.188 ± 0.092	4.13 ± 0.24	-
121m 50Sn	0.0052 ± 0.0011	0.0053 ± 0.0012	-
122 51Sb	0.000024 ± 0.0000063	0.0000153 ± 0.000005	-
124 51Sb	0.00228 ± 0.00049	0.00154 ± 0.00043	-
125 51Sb	0.117 ± 0.015	0.138 ± 0.022	-
132 52Te	5.095 ± 0.094	4.92 ± 0.32	-
129 53I	1.407 ± 0.086	1.31 ± 0.13	-
131 53I	3.724 ± 0.078	4.09 ± 0.12	-
133 53I	6.97 ± 0.13	6.99 ± 0.33	-
135 53I	6.33 ± 0.23	6.24 ± 0.22	-
128 54Xe	0.00000234 ± 0.00000085	0.0000025 ± 0.0000012	-
130 54Xe	0.00166 ± 0.00056	0.00231 ± 0.00085	-
131m 54Xe	0.0405 ± 0.004	0.0444 ± 0.0044	-
133 54Xe	6.99 ± 0.13	7.03 ± 0.33	-
133m 54Xe	0.216 ± 0.016	0.223 ± 0.021	-
135 54Xe	7.36 ± 0.24	7.5 ± 0.23	-
135m 54Xe	1.78 ± 0.21	1.97 ± 0.25	-
134 55Cs	0.00067 ± 0.00018	0.00115 ± 0.0003	-
137 55Cs	6.588 ± 0.08	6.35 ± 0.12	-
140 56Ba	5.322 ± 0.059	5.303 ± 0.074	-
140 57La	5.333 ± 0.059	5.324 ± 0.075	-
141 58Ce	5.205 ± 0.073	5.01 ± 0.16	-
144 58Ce	3.755 ± 0.03	3.504 ± 0.053	-
144 59Pr	3.756 ± 0.03	3.505 ± 0.053	-
142 60Nd	0.00000145 ± 0.0000004	0.00000251 ± 0.00000072	-
144 60Nd	3.756 ± 0.03	3.505 ± 0.053	-
147 60Nd	2.044 ± 0.039	1.929 ± 0.046	-
147 61Pm	2.044 ± 0.039	1.929 ± 0.046	-
148 61Pm	0.0000056 ± 0.0000019	0.000012 ± 0.000004	-
148m 61Pm	0.0000118 ± 0.0000044	0.000029 ± 0.000011	-
149 61Pm	1.263 ± 0.032	1.275 ± 0.056	-
151 61Pm	0.776 ± 0.018	0.796 ± 0.037	-
148 62Sm	0.0000168 ± 0.0000046	0.000039 ± 0.000011	-
150 62Sm	0.00227 ± 0.00078	0.0051 ± 0.0019	-
151 62Sm	0.776 ± 0.018	0.797 ± 0.037	-
153 62Sm	0.38 ± 0.03	0.4 ± 0.18	-
151 63Eu	0.776 ± 0.018	0.797 ± 0.037	-
152 63Eu	0.000000195 ± 0.00000005	0.00000048 ± 0.00000014	-
154 63Eu	0.000049 ± 0.000012	0.000127 ± 0.000043	-
155 63Eu	0.174 ± 0.03	0.171 ± 0.054	-

JEFF-3.1

Joint Evaluated Fission and Fusion File, Incident-neutron data, http://www-nds.iaea.org/exfor/endf00.htm, 2 October 2006; see also A. Koning, R. Forrest, M. Kellett, R. Mills, H. Henriksson, Y. Rugama, The JEFF-3.1 Nuclear Data Library, JEFF Report 21, OECD/NEA, Paris, France, 2006, ISBN 92-64-02314-3.

Yields at 10^0,1,2,3 years after fission, probably of Pu-239 not U-235 because left hump is shifted right, not considering later neutron capture, fraction of 100% not 200%. Beta decay Kr-85→Rb, Sr-90→Zr, Ru-106→Pd, Sb-125→Te, Cs-137→Ba, Ce-144→Nd, Sm-151→Eu, Eu-155→Gd visible.

Ordered by mass number

Decays, even if lengthy, are given down to the stable nuclide.

Decays with half lives longer than a century are marked with a single asterisk (*), while decays with a half life longer than a hundred million years are marked with two asterisks (**).

Yield	Isotope
0.0508%	selenium-79→*	bromine-79
0.2717%	krypton-85→	rubidium-85
5.7518%	strontium-90 →	yttrium-90→	zirconium-90
6.2956%	zirconium-93 →*	niobium-93
6.0507%	technetium-99→*	ruthenium-99
0.3912%	ruthenium-106→	rhodium-106→	palladium-106
0.1629%	palladium-107→*	silver-107
0.0003%	cadmium-113m→	cadmium-113 (essentially stable)→**	indium-113
0.0297%	antimony-125→	tellurium-125m→	tellurium-125
0.0236%	tin-126 →*	antimony-126→	tellurium-126
0.9%	iodine-129→*	xenon-129
2.8336%	iodine-131→	xenon-131
6.7896%	caesium-133 →	caesium-134→	barium-134
6.3333%	iodine-135 →	xenon-135 →	caesium-135→*	barium-135
6.3333%	iodine-135 →	xenon-135 →	xenon-136 (essentially stable)→**	barium-136
6.0899%	caesium-137→	barium-137
2.2713%	promethium-147→	samarium-147→*	neodymium-143
1.0888%	samarium-149
0.4203%	samarium-151
0.0330%	europium-155 →	gadolinium-155
0.0065%	gadolinium-157

Half lives, decay modes, and branching fractions

Half-lives and decay branching fractions for fission products

Nuclide	Half-life	Decay mode	Branching fraction	Source	Notes
85 35Br	2.9 ± 0.06 m	β−	1.0
85 36Kr	10.752 ± 0.023 y	β−	1.0
85m 36Kr	4.48 ± 0.008 h	IT	0.214 ± 0.005
		β−	0.786 ± 0.005
90 38Sr	28.8 ± 0.07 y	β−	1.0
95 40Zr	64.032 ± 0.006 d	β−	1.0
94 41Nb	(7.3 ± 0.9) × 106 d	β−	1.0
95m 41Nb	3.61 ± 0.03 d	β−	0.025 ± 0.001
		IT	0.975 ± 0.001
95 41Nb	34.985 ± 0.012 d	β−	1.0
99 43Tc	(2.111 ± 0.012) × 105 y	β−	1.0
103 44Ru	39.247 ± 0.013 d	β−	1.0
106 44Ru	1.018 ± 0.005 y	β−	1.0
106 45Rh	30.1 ± 0.3 s	β−	1.0
121m 50Sn	55 ± 5 y	β−	0.224 ± 0.02
		IT	0.776 ± 0.02
122 51Sb	2.7238 ± 0.0002 d	EC	0.0241 ± 0.0012
		β−	0.9759 ± 0.0012
124 51Sb	60.2 ± 0.03 d	β−	1.0
125 51Sb	2.7584 ± 0.0006 y	β−	1.0
129 53I	(5.89 ± 0.23) × 109 d	β−	1.0
131 53I	8.0233 ± 0.0019 d	β−	1.0
133 53I	20.87 ± 0.08 h	β−	1.0
135 53I	6.57 ± 0.02 h	β−	1.0
131m 54Xe	11.930 ± 0.016 d	IT	1.0
133 54Xe	5.243 ± 0.001 d	β−	1.0
133m 54Xe	2.19 ± 0.01 d	IT	1.0
135 54Xe	9.14 ± 0.02 h	β−	1.0
135m 54Xe	15.29 ± 0.05 m	β−	0.003 ± 0.003
		IT	0.997 ± 0.003
134 55Cs	2.063 ± 0.003 y	EC	0.000003 ± 0.000001
		β−	0.999997 ± 0.000001
137 55Cs	30.05 ± 0.08 y	β−	1.0
140 56Ba	12.753 ± 0.004 d	β−	1.0
140 57La	1.67850 ± 0.00017 d	β−	1.0
141 58Ce	32.508 ± 0.010 d	β−	1.0
144 58Ce	285.1 ± 0.6 d	β−	1.0
144 59Pr	17.28 ± 0.05 m	β−	1.0
147 60Nd	10.98 ± 0.01 d	β−	1.0
147 61Pm	2.6234 ± 0.0002 y	β−	1.0
148m 61Pm	41.29 ± 0.11 d	IT	0.042 ± 0.007
		β−	0.958 ± 0.007
148 61Pm	5.368 ± 0.002 d	β−	1.0
149 61Pm	2.2117 ± 0.0021 d	β−	1.0
151 61Pm	1.1833 ± 0.0017 d	β−	1.0
151 62Sm	90 ± 6 y	β−	1.0
153 62Sm	1.938 ± 0.010 d	β−	1.0
152 63Eu	(4.941 ± 0.007) × 103 d	β−	0.279 ± 0.003
		EC	0.721 ± 0.003
154 63Eu	(3.1381 ± 0.0014) × 103 d	EC	0.00018 ± 0.00013
		β−	0.99982 ± 0.00013
155 63Eu	4.753 ± 0.016 y	β−	1.0

Ordered by thermal neutron absorption cross section

Barns	Yield	Isotope	t½	Comment
2,650,000	6.3333%	135I → 135Xe	6.57 h	Most important neutron poison; neutron capture rapidly converts 135Xe to 136Xe; remainder decays (9.14 h) to 135Cs (2.3 My).
254,000	0.0065%	157Gd	∞	Neutron poison, but low yield.
40,140	1.0888%	149Sm	∞	2nd most important neutron poison.
20,600	0.0003%	113mCd	14.1 y	Most will be destroyed by neutron capture.
15,200	0.4203%	151Sm	90 y	Most will be destroyed by neutron capture.
3,950 60,900	0.0330%	155Eu → 155Gd	4.76 y	Both neutron poisons.
96	2.2713%	147Pm	2.62 y	Suitable for radioisotope thermoelectric generators with annual or semi-annual refueling.
80	2.8336%	131I	8.02 d
29 140	6.7896%	133Cs → 134Cs	∞ 2.065 y	Neutron capture converts a few percent of nonradioactive 133Cs to 134Cs, which has very low direct yield because beta decay stops at 134Xe; further capture will add to long-lived 135Cs.
20	6.0507%	99Tc	211 ky	Candidate for disposal by nuclear transmutation.
18	0.6576%	129I	15.7 My	Candidate for disposal by nuclear transmutation.
2.7	6.2956%	93Zr	1.53 My	Transmutation impractical.
1.8	0.1629%	107Pd	6.5 My
1.66	0.2717%	85Kr	10.78 y
0.90	5.7518%	90Sr	28.9 y
0.15	0.3912%	106Ru	373.6 d
0.11	6.0899%	137Cs	30.17 y
	0.0297%	125Sb	2.76 y
	0.0236%	126Sn	230 ky
	0.0508%	79Se	327 ky

External links

• HANDBOOK OF NUCLEAR DATA FOR SAFEGUARDS: DATABASE EXTENSIONS, AUGUST 2008
• The Live Chart of Nuclides - IAEA Color-map of yields, and detailed data by click on a nuclide.