Fission product yield

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

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. In contrast, 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 one 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%.Template:Citation needed Less often, it is stated as percentage of all fission products, so that the percentages sum to 100%.Template:Citation needed Ternary fission, about 0.2–0.4% of fissions, also produces a third light nucleus such as helium-4 (90%) or tritium (7%).Template:Citation needed

Definitions

There are several types of yields. For the most common fission reactions, the decay of the fission products preserve mass number. Thus the products form decay chains of constant mass. That makes the independent yield especially useful.Template:Rp

The independent yield is a product of three factors, Y(A) the sum yield or mass yield, $f(A,Z)$ the fractional independent yield, and R(A,Z,I) the isomeric yield ratio: $$\text{y}(A,Z,I)=\text{Y}(A)\cdot f(A,Z)\cdot R(A,Z,I)$$ Here possible product of fission can be represented by a triplet (A,Z,I), where A is the mass number, Z is the atomic number, and I is an integer for isomeric excited state, numbered from 0 for the ground state. For each decay chain (mass number A) the fractional independent yields and isomeric yield formulas sum to one: $${\mathrm{\Sigma }}_{Z}f(A,Z)={\mathrm{\Sigma }}_{I}R(A,Z,I)=1$$ and the independent yields sum to the sum yield for each chain: $$\text{Y}(A)={\mathrm{\Sigma }}_{Z,I}\text{y}(A,Z,I).$$ The independent yield excludes delayed neutron emission. The cumulative yield,, c(A,Z,I), of a nuclide (A,Z,I) is the total number of atoms produced by one fission over all time. The chain yield, Ch(A), is the sum of all the cumulative yields for one mass chain for one fission. The independent, cumulative, and chain yields are given as percent per fission, that is as the yield of products per 100 fission reaction.

Examples

The main fission products can be distinguished based on their lifetime: medium- or long-lived fission products, as presented in the two tables below.

Template:Long-lived fission products

Template:Medium-lived fission products

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]Template:Dead link.

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%
200,000 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, mostly from ternary fission or as an activation product in heavy water reactors
• activation products of neutron capture by the reactor or bomb structure or the environment
• Helium-4 from alpha decay

Fission products from U-235

Template:Cn

Yield	Element	Isotope	Halflife	Comment
6.7896%	Caesium	Template:Hs 133Cs → 134Cs	Template:Ntsh 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	Template:Hs 135I → 135Xe	Template:Ntsh 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	Template:Hs 93Zr	Template:Ntsh 1.53 My	Long-lived fission product also produced by neutron activation in zircalloy cladding.
6.1%	Molybdenum	Template:Hs 99Mo	Template:Ntsh 65.94 h	Its daughter nuclide 99mTc is important in medical diagnosing.
6.0899%	Caesium	Template:Hs 137Cs	Template:Ntsh 30.17 y	Source of most of the decay heat from years to decades after irradiation, together with Template:Chem.
6.0507%	Technetium	Template:Hs 99Tc	Template:Ntsh 211 ky	Candidate for disposal by nuclear transmutation.
5.7518%	Strontium	Template:Hs 90Sr	Template:Ntsh 28.9 y	Source of much of the decay heat together with Template:Chem on the timespan of years to decades after irradiation. Formerly used in radioisotope thermoelectric generators.
2.8336%	Iodine	Template:Hs 131I	Template:Ntsh 8.02 d	Reason for the use of potassium iodide tablets after nuclear accidents or nuclear bomb explosions.
2.2713%	Promethium	Template:Hs 147Pm	Template:Ntsh 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	Template:Hs 149Sm	Template:Ntsh Observationally stable	2nd most significant neutron poison.
0.9%	Iodine	Template:Hs 129I	Template:Ntsh 15.7 My	Long-lived fission product. Candidate for disposal by nuclear transmutation.
0.4203%	Samarium	Template:Hs 151Sm	Template:Ntsh 90 y	Neutron poison; most will be converted to stable 152Sm.
0.3912%	Ruthenium	Template:Hs 106Ru	Template:Ntsh 373.6 d	ruthenium tetroxide is volatile and chemically aggressive; daughter nuclide Template:Chem decays quickly to stable Template:Chem
0.2717%	Krypton	Template:Hs 85Kr	Template:Ntsh 10.78 y	noble gas; has some uses in industry to detect fine cracks in materials via autoradiography
0.1629%	Palladium	Template:Hs 107Pd	Template:Ntsh 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	Template:Hs 79Se	Template:Ntsh 327 ky
0.0330%	Europium, gadolinium	Template:Hs 155Eu → 155Gd	Template:Ntsh 4.76 y	Both neutron poisons, most will be destroyed while fuel still in use.
0.0297%	Antimony	Template:Hs 125Sb	Template:Ntsh 2.76 y
0.0236%	Tin	Template:Hs 126Sn	Template:Ntsh 230 ky
0.0065%	Gadolinium	Template:Hs 157Gd	Template:Ntsh stable	Neutron poison.
0.0003%	Cadmium	Template:Hs 113mCd	Template:Ntsh 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 (%)

Product	Thermal fission yield	Fast fission yield	14-MeV fission yield
Template:Nuclide	0.00171 ± 0.00018	0.00269 ± 0.00044	0.00264 ± 0.00045
Template:Nuclide	0.00084 ± 0.00015	0.00082 ± 0.00012	0.00081 ± 0.00012
Template:Nuclide	0.0108 ± 0.0004	0.0108 ± 0.0004	0.0174 ± 0.0036
Template:Nuclide	0.0108 ± 0.0004	0.0108 ± 0.0004	0.0174 ± 0.0036
Template:Nuclide	0.1702 ± 0.0049	0.17 ± 0.0049	0.1667 ± 0.0088
Template:Nuclide	1.304 ± 0.012	1.309 ± 0.043	1.64 ± 0.31
Template:Nuclide	0.000285 ± 0.000076	0.00044 ± 0.00016	0.038 ± 0.012
Template:Nuclide	0.286 ± 0.021	0.286 ± 0.026	0.47 ± 0.1
Template:Nuclide	1.303 ± 0.012	1.307 ± 0.043	1.65 ± 0.31
Template:Nuclide	5.73 ± 0.13	5.22 ± 0.18	4.41 ± 0.18
Template:Nuclide	6.502 ± 0.072	6.349 ± 0.083	5.07 ± 0.19
Template:Nuclide	0.00000042 ± 0.00000011	2.90±0.770 × 10−8	0.00004 ± 0.000015
Template:Nuclide	6.498 ± 0.072	6.345 ± 0.083	5.07 ± 0.19
Template:Nuclide	0.0702 ± 0.0067	0.0686 ± 0.0071	0.0548 ± 0.0072
Template:Nuclide	0 ± 0	0 ± 0	0 ± 0
Template:Nuclide	8.70 × 10−10 ± 3.20 × 10−10	0 ± 0	6.20 × 10−8 ± 2.50 × 10−8
Template:Nuclide	0.00042 ± 0.00015	0.000069 ± 0.000025	0.0033 ± 0.0015
Template:Nuclide	6.132 ± 0.092	5.8 ± 0.13	5.02 ± 0.13
Template:Nuclide	6.132 ± 0.092	5.8 ± 0.13	5.02 ± 0.13
Template:Nuclide	3.103 ± 0.084	3.248 ± 0.042	3.14 ± 0.11
Template:Nuclide	0.41 ± 0.011	0.469 ± 0.036	2.15 ± 0.59
Template:Nuclide	0.41 ± 0.011	0.469 ± 0.036	2.15 ± 0.59
Template:Nuclide	0.00106 ± 0.00011	0.0039 ± 0.00091	0.142 ± 0.023
Template:Nuclide	0.000000366 ± 0.000000098	0.0000004 ± 0.00000014	0.00193 ± 0.00068
Template:Nuclide	0.000089 ± 0.000021	0.000112 ± 0.000034	0.027 ± 0.01
Template:Nuclide	0.026 ± 0.0014	0.067 ± 0.011	1.42 ± 0.42
Template:Nuclide	4.276 ± 0.043	4.639 ± 0.065	3.85 ± 0.16
Template:Nuclide	0.706 ± 0.032	1.03 ± 0.26	1.59 ± 0.18
Template:Nuclide	2.878 ± 0.032	3.365 ± 0.054	4.11 ± 0.14
Template:Nuclide	6.59 ± 0.11	6.61 ± 0.13	5.42 ± 0.4
Template:Nuclide	6.39 ± 0.22	6.01 ± 0.18	4.8 ± 1.4
Template:Nuclide	0 ± 0	0 ± 0	0.00108 ± 0.00048
Template:Nuclide	0.000038 ± 0.0000098	0.000152 ± 0.000055	0.038 ± 0.014
Template:Nuclide	0.0313 ± 0.003	0.0365 ± 0.0031	0.047 ± 0.0049
Template:Nuclide	6.6 ± 0.11	6.61 ± 0.13	5.57 ± 0.41
Template:Nuclide	0.189 ± 0.015	0.19 ± 0.015	0.281 ± 0.049
Template:Nuclide	6.61 ± 0.22	6.32 ± 0.18	6.4 ± 1.8
Template:Nuclide	1.22 ± 0.12	1.23 ± 0.13	2.17 ± 0.66
Template:Nuclide	0.0000121 ± 0.0000032	0.0000279 ± 0.0000073	0.0132 ± 0.0035
Template:Nuclide	6.221 ± 0.069	5.889 ± 0.096	5.6 ± 1.3
Template:Nuclide	6.314 ± 0.095	5.959 ± 0.048	4.474 ± 0.081
Template:Nuclide	6.315 ± 0.095	5.96 ± 0.048	4.508 ± 0.081
Template:Nuclide	5.86 ± 0.15	5.795 ± 0.081	4.44 ± 0.2
Template:Nuclide	5.474 ± 0.055	5.094 ± 0.076	3.154 ± 0.038
Template:Nuclide	5.474 ± 0.055	5.094 ± 0.076	3.155 ± 0.038
Template:Nuclide	6.30 × 10−9 ± 1.70 × 10−9	1.70 × 10−9 ± 4.80 × 10−10	0.0000137 ± 0.0000049
Template:Nuclide	5.475 ± 0.055	5.094 ± 0.076	3.155 ± 0.038
Template:Nuclide	2.232 ± 0.04	2.148 ± 0.028	1.657 ± 0.045
Template:Nuclide	2.232 ± 0.04	2.148 ± 0.028	1.657 ± 0.045
Template:Nuclide	5.00 × 10−8 ± 1.70 × 10−8	7.40 × 10−9 ± 2.50 × 10−9	0.0000013 ± 0.00000042
Template:Nuclide	0.000000104 ± 0.000000039	1.78 × 10−8 ± 6.60 × 10−9	0.0000048 ± 0.0000018
Template:Nuclide	1.053 ± 0.021	1.064 ± 0.03	0.557 ± 0.09
Template:Nuclide	0.4204 ± 0.0071	0.431 ± 0.015	0.388 ± 0.061
Template:Nuclide	0.000000149 ± 0.000000041	2.43 × 10−8 ± 6.80 × 10−9	0.0000058 ± 0.0000018
Template:Nuclide	0.000061 ± 0.000022	0.0000201 ± 0.0000077	0.00045 ± 0.00018
Template:Nuclide	0.4204 ± 0.0071	0.431 ± 0.015	0.388 ± 0.061
Template:Nuclide	0.1477 ± 0.0071	0.1512 ± 0.0097	0.23 ± 0.015
Template:Nuclide	0.4204 ± 0.0071	0.431 ± 0.015	0.388 ± 0.061
Template:Nuclide	3.24 × 10−10 ± 8.50 × 10−11	0 ± 0	3.30 × 10−8 ± 1.10 × 10−8
Template:Nuclide	0.000000195 ± 0.000000064	4.00 × 10−8 ± 1.10 × 10−8	0.0000033 ± 0.0000011
Template:Nuclide	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
Template:Nuclide	0.00408 ± 0.00041	0.00346 ± 0.00057	-
Template:Nuclide	0.00135 ± 0.00019	0.00106 ± 0.00016	-
Template:Nuclide	0.0142 ± 0.0007	0.0142 ± 0.0007	-
Template:Nuclide	0.0142 ± 0.0007	0.0142 ± 0.0007	-
Template:Nuclide	0.2192 ± 0.009	0.219 ± 0.009	-
Template:Nuclide	0.574 ± 0.026	0.617 ± 0.049	-
Template:Nuclide	0.00175 ± 0.0006	0.00055 ± 0.0002	-
Template:Nuclide	0.136 ± 0.014	0.138 ± 0.017	-
Template:Nuclide	0.576 ± 0.026	0.617 ± 0.049	-
Template:Nuclide	2.013 ± 0.054	2.031 ± 0.057	-
Template:Nuclide	4.949 ± 0.099	4.682 ± 0.098	-
Template:Nuclide	0.0000168 ± 0.0000045	0.00000255 ± 0.00000069	-
Template:Nuclide	4.946 ± 0.099	4.68 ± 0.098	-
Template:Nuclide	0.0535 ± 0.0066	0.0506 ± 0.0062	-
Template:Nuclide	0 ± 0	0 ± 0	-
Template:Nuclide	3.60 × 10−8 ± 1.30 × 10−8	4.80 × 10−9 ± 1.70 × 10−9	-
Template:Nuclide	0.0051 ± 0.0018	0.0017 ± 0.00062	-
Template:Nuclide	6.185 ± 0.056	5.82 ± 0.13	-
Template:Nuclide	6.184 ± 0.056	5.82 ± 0.13	-
Template:Nuclide	6.948 ± 0.083	6.59 ± 0.16	-
Template:Nuclide	4.188 ± 0.092	4.13 ± 0.24	-
Template:Nuclide	4.188 ± 0.092	4.13 ± 0.24	-
Template:Nuclide	0.0052 ± 0.0011	0.0053 ± 0.0012	-
Template:Nuclide	0.000024 ± 0.0000063	0.0000153 ± 0.000005	-
Template:Nuclide	0.00228 ± 0.00049	0.00154 ± 0.00043	-
Template:Nuclide	0.117 ± 0.015	0.138 ± 0.022	-
Template:Nuclide	5.095 ± 0.094	4.92 ± 0.32	-
Template:Nuclide	1.407 ± 0.086	1.31 ± 0.13	-
Template:Nuclide	3.724 ± 0.078	4.09 ± 0.12	-
Template:Nuclide	6.97 ± 0.13	6.99 ± 0.33	-
Template:Nuclide	6.33 ± 0.23	6.24 ± 0.22	-
Template:Nuclide	0.00000234 ± 0.00000085	0.0000025 ± 0.0000012	-
Template:Nuclide	0.00166 ± 0.00056	0.00231 ± 0.00085	-
Template:Nuclide	0.0405 ± 0.004	0.0444 ± 0.0044	-
Template:Nuclide	6.99 ± 0.13	7.03 ± 0.33	-
Template:Nuclide	0.216 ± 0.016	0.223 ± 0.021	-
Template:Nuclide	7.36 ± 0.24	7.5 ± 0.23	-
Template:Nuclide	1.78 ± 0.21	1.97 ± 0.25	-
Template:Nuclide	0.00067 ± 0.00018	0.00115 ± 0.0003	-
Template:Nuclide	6.588 ± 0.08	6.35 ± 0.12	-
Template:Nuclide	5.322 ± 0.059	5.303 ± 0.074	-
Template:Nuclide	5.333 ± 0.059	5.324 ± 0.075	-
Template:Nuclide	5.205 ± 0.073	5.01 ± 0.16	-
Template:Nuclide	3.755 ± 0.03	3.504 ± 0.053	-
Template:Nuclide	3.756 ± 0.03	3.505 ± 0.053	-
Template:Nuclide	0.00000145 ± 0.0000004	0.00000251 ± 0.00000072	-
Template:Nuclide	3.756 ± 0.03	3.505 ± 0.053	-
Template:Nuclide	2.044 ± 0.039	1.929 ± 0.046	-
Template:Nuclide	2.044 ± 0.039	1.929 ± 0.046	-
Template:Nuclide	0.0000056 ± 0.0000019	0.000012 ± 0.000004	-
Template:Nuclide	0.0000118 ± 0.0000044	0.000029 ± 0.000011	-
Template:Nuclide	1.263 ± 0.032	1.275 ± 0.056	-
Template:Nuclide	0.776 ± 0.018	0.796 ± 0.037	-
Template:Nuclide	0.0000168 ± 0.0000046	0.000039 ± 0.000011	-
Template:Nuclide	0.00227 ± 0.00078	0.0051 ± 0.0019	-
Template:Nuclide	0.776 ± 0.018	0.797 ± 0.037	-
Template:Nuclide	0.38 ± 0.03	0.4 ± 0.18	-
Template:Nuclide	0.776 ± 0.018	0.797 ± 0.037	-
Template:Nuclide	0.000000195 ± 0.00000005	0.00000048 ± 0.00000014	-
Template:Nuclide	0.000049 ± 0.000012	0.000127 ± 0.000043	-
Template:Nuclide	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, Template:ISBN.

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 (Template:Asterisk), while decays with a half-life longer than a hundred million years are marked with two asterisks (Template:AsteriskTemplate:Asterisk).

Yield	Isotope
0.0508%	style="background:Template:Element color" | selenium-79→*	style="background:Template:Element color" | bromine-79
0.2717%	style="background:Template:Element color" | krypton-85→	style="background:Template:Element color" | rubidium-85
5.7518%	style="background:Template:Element color" | strontium-90 →	style="background:Template:Element color" | yttrium-90→	style="background:Template:Element color" | zirconium-90
6.2956%	style="background:Template:Element color" | zirconium-93 →*	style="background:Template:Element color" | niobium-93
6.0507%	style="background:Template:Element color" | technetium-99→*	style="background:Template:Element color" | ruthenium-99
0.3912%	style="background:Template:Element color" | ruthenium-106→	style="background:Template:Element color" | rhodium-106→	style="background:Template:Element color" | palladium-106
0.1629%	style="background:Template:Element color" | palladium-107→*	style="background:Template:Element color" | silver-107
0.0003%	style="background:Template:Element color" | cadmium-113m→	style="background:Template:Element color" | cadmium-113 (essentially stable)→**	style="background:Template:Element color" | indium-113
0.0297%	style="background:Template:Element color" | antimony-125→	style="background:Template:Element color" | tellurium-125m→	style="background:Template:Element color" | tellurium-125
0.0236%	style="background:Template:Element color" | tin-126 →*	style="background:Template:Element color" | antimony-126→	style="background:Template:Element color" | tellurium-126
0.9%	style="background:Template:Element color" | iodine-129→*	style="background:Template:Element color" | xenon-129
2.8336%	style="background:Template:Element color" | iodine-131→	style="background:Template:Element color" | xenon-131
6.7896%	style="background:Template:Element color" | caesium-133 →	style="background:Template:Element color" | caesium-134→	style="background:Template:Element color" | barium-134
6.3333%	style="background:Template:Element color" | iodine-135 →	style="background:Template:Element color" | xenon-135 →	style="background:Template:Element color" | caesium-135→*	style="background:Template:Element color" | barium-135
6.3333%	style="background:Template:Element color" | iodine-135 →	style="background:Template:Element color" | xenon-135 →	style="background:Template:Element color" | xenon-136 (essentially stable)→**	style="background:Template:Element color" | barium-136
6.0899%	style="background:Template:Element color" | caesium-137→	style="background:Template:Element color" | barium-137
2.2713%	style="background:Template:Element color" | promethium-147→	style="background:Template:Element color" | samarium-147 (essentially stable)→**	style="background:Template:Element color" | neodymium-143
1.0888%	style="background:Template:Element color" | samarium-149
0.4203%	style="background:Template:Element color" | samarium-151
0.0330%	style="background:Template:Element color" | europium-155 →	style="background:Template:Element color" | gadolinium-155
0.0065%	style="background:Template:Element color" | 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
Template:Nuclide	2.9 ± 0.06 m	β−	1.0		Template:Efn
Template:Nuclide	10.752 ± 0.023 y	β−	1.0
Template:Nuclide	4.48 ± 0.008 h	IT	0.214 ± 0.005
		β−	0.786 ± 0.005
Template:Nuclide	28.8 ± 0.07 y	β−	1.0
Template:Nuclide	64.032 ± 0.006 d	β−	1.0
Template:Nuclide	(7.3 ± 0.9) × 106 d	β−	1.0
Template:Nuclide	3.61 ± 0.03 d	β−	0.025 ± 0.001		Template:Efn
		IT	0.975 ± 0.001
Template:Nuclide	34.985 ± 0.012 d	β−	1.0
Template:Nuclide	(2.111 ± 0.012) × 105 y	β−	1.0
Template:Nuclide	39.247 ± 0.013 d	β−	1.0
Template:Nuclide	1.018 ± 0.005 y	β−	1.0
Template:Nuclide	30.1 ± 0.3 s	β−	1.0
Template:Nuclide	55 ± 5 y	β−	0.224 ± 0.02
		IT	0.776 ± 0.02
Template:Nuclide	2.7238 ± 0.0002 d	EC	0.0241 ± 0.0012
		β−	0.9759 ± 0.0012
Template:Nuclide	60.2 ± 0.03 d	β−	1.0
Template:Nuclide	2.7584 ± 0.0006 y	β−	1.0
Template:Nuclide	(5.89 ± 0.23) × 109 d	β−	1.0
Template:Nuclide	8.0233 ± 0.0019 d	β−	1.0
Template:Nuclide	20.87 ± 0.08 h	β−	1.0		Template:Efn
Template:Nuclide	6.57 ± 0.02 h	β−	1.0
Template:Nuclide	11.930 ± 0.016 d	IT	1.0
Template:Nuclide	5.243 ± 0.001 d	β−	1.0
Template:Nuclide	2.19 ± 0.01 d	IT	1.0
Template:Nuclide	9.14 ± 0.02 h	β−	1.0
Template:Nuclide	15.29 ± 0.05 m	β−	0.003 ± 0.003		Template:Efn
		IT	0.997 ± 0.003
Template:Nuclide	2.063 ± 0.003 y	EC	0.000003 ± 0.000001		Template:Efn
		β−	0.999997 ± 0.000001
Template:Nuclide	30.05 ± 0.08 y	β−	1.0
Template:Nuclide	12.753 ± 0.004 d	β−	1.0
Template:Nuclide	1.67850 ± 0.00017 d	β−	1.0
Template:Nuclide	32.508 ± 0.010 d	β−	1.0
Template:Nuclide	285.1 ± 0.6 d	β−	1.0
Template:Nuclide	17.28 ± 0.05 m	β−	1.0
Template:Nuclide	10.98 ± 0.01 d	β−	1.0
Template:Nuclide	2.6234 ± 0.0002 y	β−	1.0
Template:Nuclide	41.29 ± 0.11 d	IT	0.042 ± 0.007
		β−	0.958 ± 0.007
Template:Nuclide	5.368 ± 0.002 d	β−	1.0
Template:Nuclide	2.2117 ± 0.0021 d	β−	1.0
Template:Nuclide	1.1833 ± 0.0017 d	β−	1.0
Template:Nuclide	90 ± 6 y	β−	1.0
Template:Nuclide	1.938 ± 0.010 d	β−	1.0
Template:Nuclide	(4.941 ± 0.007) × 103 d	β−	0.279 ± 0.003		Template:Efn
		EC	0.721 ± 0.003
Template:Nuclide	(3.1381 ± 0.0014) × 103 d	EC	0.00018 ± 0.00013		Template:Efn
		β−	0.99982 ± 0.00013
Template:Nuclide	4.753 ± 0.016 y	β−	1.0

Ordered by thermal neutron absorption cross section

Barns	Yield	Isotope	t½	Comment
Template:Nts	6.3333%	Template:Hs 135I → 135Xe	Template:Ntsh 6.57 h	Most important neutron poison; neutron capture rapidly converts 135Xe to 136Xe; remainder decays (9.14 h) to 135Cs (2.3 My).
Template:Nts	0.0065%	Template:Hs 157Gd	∞	Neutron poison, but low yield.
Template:Nts	1.0888%	Template:Hs 149Sm	∞	2nd most important neutron poison.
Template:Nts	0.0003%	Template:Hs 113mCd	Template:Ntsh 14.1 y	Most will be destroyed by neutron capture.
Template:Nts	0.4203%	Template:Hs 151Sm	Template:Ntsh 90 y	Most will be destroyed by neutron capture.
Template:Nts 60,900	0.0330%	Template:Hs 155Eu → 155Gd	Template:Ntsh 4.76 y	Both neutron poisons.
Template:Nts	2.2713%	Template:Hs 147Pm	Template:Ntsh 2.62 y	Suitable for radioisotope thermoelectric generators with annual or semi-annual refueling.
Template:Nts	2.8336%	Template:Hs 131I	Template:Ntsh 8.02 d
Template:Nts 140	6.7896%	Template:Hs 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.
Template:Nts	6.0507%	Template:Hs 99Tc	Template:Ntsh 211 ky	Candidate for disposal by nuclear transmutation.
Template:Nts	0.6576%	Template:Hs 129I	Template:Ntsh 15.7 My	Candidate for disposal by nuclear transmutation.
Template:Nts	6.2956%	Template:Hs 93Zr	Template:Ntsh 1.53 My	Transmutation impractical.
Template:Nts	0.1629%	Template:Hs 107Pd	Template:Ntsh 6.5 My
Template:Nts	0.2717%	Template:Hs 85Kr	Template:Ntsh 10.78 y
Template:Nts	5.7518%	Template:Hs 90Sr	Template:Ntsh 28.9 y
Template:Nts	0.3912%	Template:Hs 106Ru	Template:Ntsh 373.6 d
Template:Nts	6.0899%	Template:Hs 137Cs	Template:Ntsh 30.17 y
	0.0297%	Template:Hs 125Sb	Template:Ntsh 2.76 y
	0.0236%	Template:Hs 126Sn	Template:Ntsh 230 ky
	0.0508%	Template:Hs 79Se	Template:Ntsh 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 clicking on a nuclide.