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Fission product yield

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Fractions of products of nuclear fission
Long-lived fission products
Nuclide t1⁄2 Yield Q βγ
(Ma) (%) (keV)
Tc 0.211 6.1385 294 β
Sn 0.230 0.1084 4050 βγ
Se 0.327 0.0447 151 β
Cs 1.33  6.9110 269 β
Zr 1.53  5.4575 91 βγ
Pd 6.5   1.2499 33 β
I 16.14   0.8410 194 βγ
  1. Decay energy is split among β, neutrino, and γ if any.
  2. Per 65 thermal neutron fissions of U and 35 of Pu.
  3. Has decay energy 380 keV, but its decay product Sb has decay energy 3.67 MeV.
  4. Lower in thermal reactors because Xe, its predecessor, readily absorbs neutrons.
Medium-lived fission products
t½
(year) 		Yield
(%) 		Q
(keV) 		βγ
Eu  4.76 0.0803  252 βγ
Kr 10.76 0.2180  687 βγ
Cd 14.1  0.0008  316 β
Sr 28.9  4.505   2826 β
Cs 30.23 6.337   1176 βγ
Sn 43.9  0.00005 390 βγ
Sm 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:

  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 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 Fm, 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 .

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.:

  • Xe capturing a neutron and becoming nearly stable Xe, rather than decaying to Cs which is radioactive with a half-life of 2.3 million years
  • Nonradioactive Cs capturing a neutron and becoming Cs, which is radioactive with a half-life of 2 years
  • Many of the fission products with mass 147 or greater such as Pm, Sm, Sm, and Eu 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

Fission products from U-235

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

1H
 0.00171 ± 0.00018 0.00269 ± 0.00044 0.00264 ± 0.00045

1H
 0.00084 ± 0.00015 0.00082 ± 0.00012 0.00081 ± 0.00012

1H
 0.0108 ± 0.0004 0.0108 ± 0.0004 0.0174 ± 0.0036

2He
 0.0108 ± 0.0004 0.0108 ± 0.0004 0.0174 ± 0.0036

2He
 0.1702 ± 0.0049 0.17 ± 0.0049 0.1667 ± 0.0088

35Br
 1.304 ± 0.012 1.309 ± 0.043 1.64 ± 0.31

36Kr
 0.000285 ± 0.000076 0.00044 ± 0.00016 0.038 ± 0.012

36Kr
 0.286 ± 0.021 0.286 ± 0.026 0.47 ± 0.1

36Kr
 1.303 ± 0.012 1.307 ± 0.043 1.65 ± 0.31

38Sr
 5.73 ± 0.13 5.22 ± 0.18 4.41 ± 0.18

40Zr
 6.502 ± 0.072 6.349 ± 0.083 5.07 ± 0.19

41Nb
 0.00000042 ± 0.00000011 2.90±0.770 × 10 0.00004 ± 0.000015

41Nb
 6.498 ± 0.072 6.345 ± 0.083 5.07 ± 0.19

41Nb
 0.0702 ± 0.0067 0.0686 ± 0.0071 0.0548 ± 0.0072

42Mo
 0 ± 0 0 ± 0 0 ± 0

42Mo
 8.70 × 10 ± 3.20 × 10 0 ± 0 6.20 × 10 ± 2.50 × 10

42Mo
 0.00042 ± 0.00015 0.000069 ± 0.000025 0.0033 ± 0.0015

42Mo
 6.132 ± 0.092 5.8 ± 0.13 5.02 ± 0.13

43Tc
 6.132 ± 0.092 5.8 ± 0.13 5.02 ± 0.13

44Ru
 3.103 ± 0.084 3.248 ± 0.042 3.14 ± 0.11

44Ru
 0.41 ± 0.011 0.469 ± 0.036 2.15 ± 0.59

45Rh
 0.41 ± 0.011 0.469 ± 0.036 2.15 ± 0.59

50Sn
 0.00106 ± 0.00011 0.0039 ± 0.00091 0.142 ± 0.023

51Sb
 0.000000366 ± 0.000000098 0.0000004 ± 0.00000014 0.00193 ± 0.00068

51Sb
 0.000089 ± 0.000021 0.000112 ± 0.000034 0.027 ± 0.01

51Sb
 0.026 ± 0.0014 0.067 ± 0.011 1.42 ± 0.42

52Te
 4.276 ± 0.043 4.639 ± 0.065 3.85 ± 0.16

53I
 0.706 ± 0.032 1.03 ± 0.26 1.59 ± 0.18

53I
 2.878 ± 0.032 3.365 ± 0.054 4.11 ± 0.14

53I
 6.59 ± 0.11 6.61 ± 0.13 5.42 ± 0.4

53I
 6.39 ± 0.22 6.01 ± 0.18 4.8 ± 1.4

54Xe
 0 ± 0 0 ± 0 0.00108 ± 0.00048

54Xe
 0.000038 ± 0.0000098 0.000152 ± 0.000055 0.038 ± 0.014

54Xe
 0.0313 ± 0.003 0.0365 ± 0.0031 0.047 ± 0.0049

54Xe
 6.6 ± 0.11 6.61 ± 0.13 5.57 ± 0.41

54Xe
 0.189 ± 0.015 0.19 ± 0.015 0.281 ± 0.049

54Xe
 6.61 ± 0.22 6.32 ± 0.18 6.4 ± 1.8

54Xe
 1.22 ± 0.12 1.23 ± 0.13 2.17 ± 0.66

55Cs
 0.0000121 ± 0.0000032 0.0000279 ± 0.0000073 0.0132 ± 0.0035

55Cs
 6.221 ± 0.069 5.889 ± 0.096 5.6 ± 1.3

56Ba
 6.314 ± 0.095 5.959 ± 0.048 4.474 ± 0.081

57La
 6.315 ± 0.095 5.96 ± 0.048 4.508 ± 0.081

58Ce
 5.86 ± 0.15 5.795 ± 0.081 4.44 ± 0.2

58Ce
 5.474 ± 0.055 5.094 ± 0.076 3.154 ± 0.038

59Pr
 5.474 ± 0.055 5.094 ± 0.076 3.155 ± 0.038

60Nd
 6.30 × 10 ± 1.70 × 10 1.70 × 10 ± 4.80 × 10 0.0000137 ± 0.0000049

60Nd
 5.475 ± 0.055 5.094 ± 0.076 3.155 ± 0.038

60Nd
 2.232 ± 0.04 2.148 ± 0.028 1.657 ± 0.045

61Pm
 2.232 ± 0.04 2.148 ± 0.028 1.657 ± 0.045

61Pm
 5.00 × 10 ± 1.70 × 10 7.40 × 10 ± 2.50 × 10 0.0000013 ± 0.00000042

61Pm
 0.000000104 ± 0.000000039 1.78 × 10 ± 6.60 × 10 0.0000048 ± 0.0000018

61Pm
 1.053 ± 0.021 1.064 ± 0.03 0.557 ± 0.09

61Pm
 0.4204 ± 0.0071 0.431 ± 0.015 0.388 ± 0.061

62Sm
 0.000000149 ± 0.000000041 2.43 × 10 ± 6.80 × 10 0.0000058 ± 0.0000018

62Sm
 0.000061 ± 0.000022 0.0000201 ± 0.0000077 0.00045 ± 0.00018

62Sm
 0.4204 ± 0.0071 0.431 ± 0.015 0.388 ± 0.061

62Sm
 0.1477 ± 0.0071 0.1512 ± 0.0097 0.23 ± 0.015

63Eu
 0.4204 ± 0.0071 0.431 ± 0.015 0.388 ± 0.061

63Eu
 3.24 × 10 ± 8.50 × 10 0 ± 0 3.30 × 10 ± 1.10 × 10

63Eu
 0.000000195 ± 0.000000064 4.00 × 10 ± 1.10 × 10 0.0000033 ± 0.0000011

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

1H
 0.00408 ± 0.00041 0.00346 ± 0.00057 -

1H
 0.00135 ± 0.00019 0.00106 ± 0.00016 -

1H
 0.0142 ± 0.0007 0.0142 ± 0.0007 -

2He
 0.0142 ± 0.0007 0.0142 ± 0.0007 -

2He
 0.2192 ± 0.009 0.219 ± 0.009 -

35Br
 0.574 ± 0.026 0.617 ± 0.049 -

36Kr
 0.00175 ± 0.0006 0.00055 ± 0.0002 -

36Kr
 0.136 ± 0.014 0.138 ± 0.017 -

36Kr
 0.576 ± 0.026 0.617 ± 0.049 -

38Sr
 2.013 ± 0.054 2.031 ± 0.057 -

40Zr
 4.949 ± 0.099 4.682 ± 0.098 -

41Nb
 0.0000168 ± 0.0000045 0.00000255 ± 0.00000069 -

41Nb
 4.946 ± 0.099 4.68 ± 0.098 -

41Nb
 0.0535 ± 0.0066 0.0506 ± 0.0062 -

42Mo
 0 ± 0 0 ± 0 -

42Mo
 3.60 × 10 ± 1.30 × 10 4.80 × 10 ± 1.70 × 10 -

42Mo
 0.0051 ± 0.0018 0.0017 ± 0.00062 -

42Mo
 6.185 ± 0.056 5.82 ± 0.13 -

43Tc
 6.184 ± 0.056 5.82 ± 0.13 -

44Ru
 6.948 ± 0.083 6.59 ± 0.16 -

44Ru
 4.188 ± 0.092 4.13 ± 0.24 -

45Rh
 4.188 ± 0.092 4.13 ± 0.24 -

50Sn
 0.0052 ± 0.0011 0.0053 ± 0.0012 -

51Sb
 0.000024 ± 0.0000063 0.0000153 ± 0.000005 -

51Sb
 0.00228 ± 0.00049 0.00154 ± 0.00043 -

51Sb
 0.117 ± 0.015 0.138 ± 0.022 -

52Te
 5.095 ± 0.094 4.92 ± 0.32 -

53I
 1.407 ± 0.086 1.31 ± 0.13 -

53I
 3.724 ± 0.078 4.09 ± 0.12 -

53I
 6.97 ± 0.13 6.99 ± 0.33 -

53I
 6.33 ± 0.23 6.24 ± 0.22 -

54Xe
 0.00000234 ± 0.00000085 0.0000025 ± 0.0000012 -

54Xe
 0.00166 ± 0.00056 0.00231 ± 0.00085 -

54Xe
 0.0405 ± 0.004 0.0444 ± 0.0044 -

54Xe
 6.99 ± 0.13 7.03 ± 0.33 -

54Xe
 0.216 ± 0.016 0.223 ± 0.021 -

54Xe
 7.36 ± 0.24 7.5 ± 0.23 -

54Xe
 1.78 ± 0.21 1.97 ± 0.25 -

55Cs
 0.00067 ± 0.00018 0.00115 ± 0.0003 -

55Cs
 6.588 ± 0.08 6.35 ± 0.12 -

56Ba
 5.322 ± 0.059 5.303 ± 0.074 -

57La
 5.333 ± 0.059 5.324 ± 0.075 -

58Ce
 5.205 ± 0.073 5.01 ± 0.16 -

58Ce
 3.755 ± 0.03 3.504 ± 0.053 -

59Pr
 3.756 ± 0.03 3.505 ± 0.053 -

60Nd
 0.00000145 ± 0.0000004 0.00000251 ± 0.00000072 -

60Nd
 3.756 ± 0.03 3.505 ± 0.053 -

60Nd
 2.044 ± 0.039 1.929 ± 0.046 -

61Pm
 2.044 ± 0.039 1.929 ± 0.046 -

61Pm
 0.0000056 ± 0.0000019 0.000012 ± 0.000004 -

61Pm
 0.0000118 ± 0.0000044 0.000029 ± 0.000011 -

61Pm
 1.263 ± 0.032 1.275 ± 0.056 -

61Pm
 0.776 ± 0.018 0.796 ± 0.037 -

62Sm
 0.0000168 ± 0.0000046 0.000039 ± 0.000011 -

62Sm
 0.00227 ± 0.00078 0.0051 ± 0.0019 -

62Sm
 0.776 ± 0.018 0.797 ± 0.037 -

62Sm
 0.38 ± 0.03 0.4 ± 0.18 -

63Eu
 0.776 ± 0.018 0.797 ± 0.037 -

63Eu
 0.000000195 ± 0.00000005 0.00000048 ± 0.00000014 -

63Eu
 0.000049 ± 0.000012 0.000127 ± 0.000043 -

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 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

35Br
 2.9 ± 0.06 m β 1.0

36Kr
 10.752 ± 0.023 y β 1.0

36Kr
 4.48 ± 0.008 h IT 0.214 ± 0.005
β 0.786 ± 0.005

38Sr
 28.8 ± 0.07 y β 1.0

40Zr
 64.032 ± 0.006 d β 1.0

41Nb
 (7.3 ± 0.9) × 10 d β 1.0

41Nb
 3.61 ± 0.03 d β 0.025 ± 0.001
IT 0.975 ± 0.001

41Nb
 34.985 ± 0.012 d β 1.0

43Tc
 (2.111 ± 0.012) × 10 y β 1.0

44Ru
 39.247 ± 0.013 d β 1.0

44Ru
 1.018 ± 0.005 y β 1.0

45Rh
 30.1 ± 0.3 s β 1.0

50Sn
 55 ± 5 y β 0.224 ± 0.02
IT 0.776 ± 0.02

51Sb
 2.7238 ± 0.0002 d EC 0.0241 ± 0.0012
β 0.9759 ± 0.0012

51Sb
 60.2 ± 0.03 d β 1.0

51Sb
 2.7584 ± 0.0006 y β 1.0

53I
 (5.89 ± 0.23) × 10 d β 1.0

53I
 8.0233 ± 0.0019 d β 1.0

53I
 20.87 ± 0.08 h β 1.0

53I
 6.57 ± 0.02 h β 1.0

54Xe
 11.930 ± 0.016 d IT 1.0

54Xe
 5.243 ± 0.001 d β 1.0

54Xe
 2.19 ± 0.01 d IT 1.0

54Xe
 9.14 ± 0.02 h β 1.0

54Xe
 15.29 ± 0.05 m β 0.003 ± 0.003
IT 0.997 ± 0.003

55Cs
 2.063 ± 0.003 y EC 0.000003 ± 0.000001
β 0.999997 ± 0.000001

55Cs
 30.05 ± 0.08 y β 1.0

56Ba
 12.753 ± 0.004 d β 1.0

57La
 1.67850 ± 0.00017 d β 1.0

58Ce
 32.508 ± 0.010 d β 1.0

58Ce
 285.1 ± 0.6 d β 1.0

59Pr
 17.28 ± 0.05 m β 1.0

60Nd
 10.98 ± 0.01 d β 1.0

61Pm
 2.6234 ± 0.0002 y β 1.0

61Pm
 41.29 ± 0.11 d IT 0.042 ± 0.007
β 0.958 ± 0.007

61Pm
 5.368 ± 0.002 d β 1.0

61Pm
 2.2117 ± 0.0021 d β 1.0

61Pm
 1.1833 ± 0.0017 d β 1.0

62Sm
 90 ± 6 y β 1.0

62Sm
 1.938 ± 0.010 d β 1.0

63Eu
 (4.941 ± 0.007) × 10 d β 0.279 ± 0.003
EC 0.721 ± 0.003

63Eu
 (3.1381 ± 0.0014) × 10 d EC 0.00018 ± 0.00013
β 0.99982 ± 0.00013

63Eu
 4.753 ± 0.016 y β 1.0
  1. β decay branches of 0.9982 ± 0.0002 to Kr-85m and 0.0018 ± 0.0002 to Kr-85.
  2. ENSDF branching fractions: 0.944 ± 0.007 for IT and 0.056 ± 0.007 for β.
  3. β decay branch of 0.0288 ± 0.0002 to Xe-133m.
  4. Branching fractions were averaged from ENSDF database.
  5. Branching fractions were adopted from ENSDF database.
  6. ^ Branching fractions were adopted from LNHB data.

Ordered by thermal neutron absorption cross section

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

References

  1. "fissionyield". Archived from the original on 2007-05-28. Retrieved 2007-06-10.
  2. 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.
  3. 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.
  4. ^ "Cumulative Fission Yields". www-nds.iaea.org. IAEA. Retrieved 11 November 2016.
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