Fission product yield

Long-lived fission products
v
t
e
Nuclide	t_1⁄2	Yield	Q^{[a 1]}	βγ
	(Ma)	(%)^{[a 2]}	(keV)
⁹⁹Tc	0.211	6.1385	294	β
¹²⁶Sn	0.230	0.1084	4050^{[a 3]}	βγ
⁷⁹Se	0.327	0.0447	151	β
¹³⁵Cs	1.33	6.9110^{[a 4]}	269	β
⁹³Zr	1.53	5.4575	91	βγ
¹⁰⁷Pd	6.5	1.2499	33	β
¹²⁹I	16.14	0.8410	194	βγ
^ Decay energy is split among β, neutrino, and γ if any. ^ Per 65 thermal neutron fissions of ²³⁵U and 35 of ²³⁹Pu. ^ Has decay energy 380 keV, but its decay product ¹²⁶Sb has decay energy 3.67 MeV. ^ Lower in thermal reactors because ¹³⁵Xe, its predecessor, readily absorbs neutrons.

Medium-lived fission products
v
t
e
	t_½ (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	94.6	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:

Individual isotope
Chemical element spanning several isotopes of different mass number but same atomic number.
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,^[1] as nuclei closer to magic numbers are more stable.^[2]

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).

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]^{[permanent dead link‍]}.

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

t_½ 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%^[3]	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.

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 (%)^[4]
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 (%)^[4]
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.

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^[5]
Nuclide	Half-life	Decay mode	Branching fraction	Source	Notes
⁸⁵ ₃₅Br	2.9 ± 0.06 m	β⁻	1.0	^[6]	^[a]
⁸⁵ ₃₆Kr	10.752 ± 0.023 y	β⁻	1.0	^[7]
^85m ₃₆Kr	4.48 ± 0.008 h	IT	0.214 ± 0.005	^[6]
^85m ₃₆Kr	4.48 ± 0.008 h	β⁻	0.786 ± 0.005	^[6]
⁹⁰ ₃₈Sr	28.8 ± 0.07 y	β⁻	1.0	^[8]
⁹⁵ ₄₀Zr	64.032 ± 0.006 d	β⁻	1.0	^[8]
⁹⁴ ₄₁Nb	(7.3 ± 0.9) × 10⁶ d	β⁻	1.0	^[9]
^95m ₄₁Nb	3.61 ± 0.03 d	β⁻	0.025 ± 0.001	^[8]	^[b]
^95m ₄₁Nb	3.61 ± 0.03 d	IT	0.975 ± 0.001	^[8]	^[b]
⁹⁵ ₄₁Nb	34.985 ± 0.012 d	β⁻	1.0	^[9]
⁹⁹ ₄₃Tc	(2.111 ± 0.012) × 10⁵ y	β⁻	1.0	^[6]
¹⁰³ ₄₄Ru	39.247 ± 0.013 d	β⁻	1.0	^[9]
¹⁰⁶ ₄₄Ru	1.018 ± 0.005 y	β⁻	1.0	^[9]
¹⁰⁶ ₄₅Rh	30.1 ± 0.3 s	β⁻	1.0	^[9]
^121m ₅₀Sn	55 ± 5 y	β⁻	0.224 ± 0.02	^[6]
^121m ₅₀Sn	55 ± 5 y	IT	0.776 ± 0.02	^[6]
¹²² ₅₁Sb	2.7238 ± 0.0002 d	EC	0.0241 ± 0.0012	^[6]
¹²² ₅₁Sb	2.7238 ± 0.0002 d	β⁻	0.9759 ± 0.0012	^[6]
¹²⁴ ₅₁Sb	60.2 ± 0.03 d	β⁻	1.0	^[6]
¹²⁵ ₅₁Sb	2.7584 ± 0.0006 y	β⁻	1.0	^[9]
¹²⁹ ₅₃I	(5.89 ± 0.23) × 10⁹ d	β⁻	1.0	^[9]
¹³¹ ₅₃I	8.0233 ± 0.0019 d	β⁻	1.0	^[7]
¹³³ ₅₃I	20.87 ± 0.08 h	β⁻	1.0	^[8]	^[c]
¹³⁵ ₅₃I	6.57 ± 0.02 h	β⁻	1.0	^[6]
^131m ₅₄Xe	11.930 ± 0.016 d	IT	1.0	^[7]
¹³³ ₅₄Xe	5.243 ± 0.001 d	β⁻	1.0	^[6]
^133m ₅₄Xe	2.19 ± 0.01 d	IT	1.0	^[6]
¹³⁵ ₅₄Xe	9.14 ± 0.02 h	β⁻	1.0	^[6]
^135m ₅₄Xe	15.29 ± 0.05 m	β⁻	0.003 ± 0.003	^[6]	^[d]
^135m ₅₄Xe	15.29 ± 0.05 m	IT	0.997 ± 0.003	^[6]	^[d]
¹³⁴ ₅₅Cs	2.063 ± 0.003 y	EC	0.000003 ± 0.000001	^[9]	^[e]
¹³⁴ ₅₅Cs	2.063 ± 0.003 y	β⁻	0.999997 ± 0.000001	^[9]	^[e]
¹³⁷ ₅₅Cs	30.05 ± 0.08 y	β⁻	1.0	^[9]
¹⁴⁰ ₅₆Ba	12.753 ± 0.004 d	β⁻	1.0	^[7]
¹⁴⁰ ₅₇La	1.67850 ± 0.00017 d	β⁻	1.0	^[7]
¹⁴¹ ₅₈Ce	32.508 ± 0.010 d	β⁻	1.0	^[8]
¹⁴⁴ ₅₈Ce	285.1 ± 0.6 d	β⁻	1.0	^[9]
¹⁴⁴ ₅₉Pr	17.28 ± 0.05 m	β⁻	1.0	^[6]
¹⁴⁷ ₆₀Nd	10.98 ± 0.01 d	β⁻	1.0	^[6]
¹⁴⁷ ₆₁Pm	2.6234 ± 0.0002 y	β⁻	1.0	^[6]
^148m ₆₁Pm	41.29 ± 0.11 d	IT	0.042 ± 0.007	^[6]
^148m ₆₁Pm	41.29 ± 0.11 d	β⁻	0.958 ± 0.007	^[6]
¹⁴⁸ ₆₁Pm	5.368 ± 0.002 d	β⁻	1.0	^[6]
¹⁴⁹ ₆₁Pm	2.2117 ± 0.0021 d	β⁻	1.0	^[6]
¹⁵¹ ₆₁Pm	1.1833 ± 0.0017 d	β⁻	1.0	^[6]
¹⁵¹ ₆₂Sm	90 ± 6 y	β⁻	1.0	^[6]
¹⁵³ ₆₂Sm	1.938 ± 0.010 d	β⁻	1.0	^[9]
¹⁵² ₆₃Eu	(4.941 ± 0.007) × 10³ d	β⁻	0.279 ± 0.003	^[9]	^[f]
¹⁵² ₆₃Eu	(4.941 ± 0.007) × 10³ d	EC	0.721 ± 0.003	^[9]	^[f]
¹⁵⁴ ₆₃Eu	(3.1381 ± 0.0014) × 10³ d	EC	0.00018 ± 0.00013	^[9]	^[f]
¹⁵⁴ ₆₃Eu	(3.1381 ± 0.0014) × 10³ d	β⁻	0.99982 ± 0.00013	^[9]	^[f]
¹⁵⁵ ₆₃Eu	4.753 ± 0.016 y	β⁻	1.0	^[9]

^ β⁻ decay branches of 0.9982 ± 0.0002 to Kr-85m and 0.0018 ± 0.0002 to Kr-85.
^ ENSDF branching fractions: 0.944 ± 0.007 for IT and 0.056 ± 0.007 for β⁻.
^ β⁻ decay branch of 0.0288 ± 0.0002 to Xe-133m.
^ Branching fractions were averaged from ENSDF database.
^ Branching fractions were adopted from ENSDF database.
^ ^a ^b Branching fractions were adopted from LNHB data.

Ordered by thermal neutron absorption cross section

Barns	Yield	Isotope	t_½	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

References

^ "fissionyield". Archived from the original on 2007-05-28. Retrieved 2007-06-10.
^ Möller, P; Madland, DG; Sierk, AJ; Iwamoto, A (15 February 2001). "Nuclear fission modes and fragment mass asymmetries in a five-dimensional deformation space". Nature. 409 (6822): 785–790. Bibcode:2001Natur.409..785M. doi:10.1038/35057204. PMID 11236985. S2CID 9754793.
^ Purkayastha, B. C., and G. R. Martin. "The yields of 129I in natural and in neutron-induced fission of uranium." Canadian Journal of Chemistry 34.3 (1956): 293-300.
^ ^a ^b "Cumulative Fission Yields". www-nds.iaea.org. IAEA. Retrieved 11 November 2016.
^ "Half-lives and decay branching fractions for activation products". www-nds.iaea.org. IAEA. Retrieved 11 November 2016.
^ ^a ^b ^c ^d ^e ^f ^g ^h ⁱ ^j ^k ^l ^m ⁿ ^o ^p ^q ^r ^s Evaluated Nuclear Structure Data File, http://www-nds.iaea.org/ensdf/, 26 January 2006.
^ ^a ^b ^c ^d ^e M.-M. Bé, V. Chisté, C. Dulieu, E. Browne, V. Chechev, N. Kuzmenko, R. Helmer, A. Nichols, E. Schönfeld, R. Dersch, Monographie BIPM-5, Table of Radionuclides, Vol. 2 - A = 151 to 242, 2004.
^ ^a ^b ^c ^d ^e Laboratoire National Henri Becquerel, Recommended Data, http://www.nucleide.org/DDEP_WG/DDEPdata.htm Archived 2021-02-13 at the Wayback Machine, 16 January 2006.
^ ^a ^b ^c ^d ^e ^f ^g ^h ⁱ ^j ^k ^l ^m ⁿ M.-M. Bé, V.P. Chechev, R. Dersch, O.A.M. Helene, R.G. Helmer, M. Herman, S. Hlavác, A. Marcinkowski, G.L. Molnár, A.L. Nichols, E. Schönfeld, V.R. Vanin, M.J. Woods, IAEA CRP "Update of X-ray and Gamma-ray Decay Data Standards for Detector Calibration and Other Applications", IAEA Scientific and Technical Information report STI/PUB/1287, May 2007, International Atomic Energy Agency, Vienna, Austria, ISBN 92-0-113606-4.

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.

[1] Decay energy is split among β, neutrino, and γ if any.

[2] Per 65 thermal neutron fissions of ²³⁵U and 35 of ²³⁹Pu.

[3] Has decay energy 380 keV, but its decay product ¹²⁶Sb has decay energy 3.67 MeV.

[4] Lower in thermal reactors because ¹³⁵Xe, its predecessor, readily absorbs neutrons.

[11] β⁻ decay branches of 0.9982 ± 0.0002 to Kr-85m and 0.0018 ± 0.0002 to Kr-85.

[15] ENSDF branching fractions: 0.944 ± 0.007 for IT and 0.056 ± 0.007 for β⁻.

[16] β⁻ decay branch of 0.0288 ± 0.0002 to Xe-133m.

[17] Branching fractions were averaged from ENSDF database.

[18] Branching fractions were adopted from ENSDF database.

[LNHBadopted-19] Branching fractions were adopted from LNHB data.

[5] "fissionyield". Archived from the original on 2007-05-28. Retrieved 2007-06-10.

[NatureMagicNumbers-6] Möller, P; Madland, DG; Sierk, AJ; Iwamoto, A (15 February 2001). "Nuclear fission modes and fragment mass asymmetries in a five-dimensional deformation space". Nature. 409 (6822): 785–790. Bibcode:2001Natur.409..785M. doi:10.1038/35057204. PMID 11236985. S2CID 9754793.

[7] Purkayastha, B. C., and G. R. Martin. "The yields of 129I in natural and in neutron-induced fission of uranium." Canadian Journal of Chemistry 34.3 (1956): 293-300.

[IAEA-C3-8] "Cumulative Fission Yields". www-nds.iaea.org. IAEA. Retrieved 11 November 2016.

[IAEA-D1-9] "Half-lives and decay branching fractions for activation products". www-nds.iaea.org. IAEA. Retrieved 11 November 2016.

[ENSDF-10] ^ ^a ^b ^c ^d ^e ^f ^g ^h ⁱ ^j ^k ^l ^m ⁿ ^o ^p ^q ^r ^s Evaluated Nuclear Structure Data File, http://www-nds.iaea.org/ensdf/, 26 January 2006.

[BIPM-5-12] M.-M. Bé, V. Chisté, C. Dulieu, E. Browne, V. Chechev, N. Kuzmenko, R. Helmer, A. Nichols, E. Schönfeld, R. Dersch, Monographie BIPM-5, Table of Radionuclides, Vol. 2 - A = 151 to 242, 2004.

[LNHB-13] Laboratoire National Henri Becquerel, Recommended Data, http://www.nucleide.org/DDEP_WG/DDEPdata.htm Archived 2021-02-13 at the Wayback Machine, 16 January 2006.

[IAEA-CRP-XG-14] ^ ^a ^b ^c ^d ^e ^f ^g ^h ⁱ ^j ^k ^l ^m ⁿ M.-M. Bé, V.P. Chechev, R. Dersch, O.A.M. Helene, R.G. Helmer, M. Herman, S. Hlavác, A. Marcinkowski, G.L. Molnár, A.L. Nichols, E. Schönfeld, V.R. Vanin, M.J. Woods, IAEA CRP "Update of X-ray and Gamma-ray Decay Data Standards for Detector Calibration and Other Applications", IAEA Scientific and Technical Information report STI/PUB/1287, May 2007, International Atomic Energy Agency, Vienna, Austria, ISBN 92-0-113606-4.

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