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Xenon-135 (135 Xe) is an unstable isotope of xenon with a half-life of about 9.2 hours. 135 Xe is a fission product of uranium and it is the most powerful known neutron-absorbing nuclear poison (2 million barns; [1] up to 3 million barns [1] under reactor conditions [2]), with a significant effect on nuclear reactor operation.
Radioactive isotope table "lists ALL radioactive nuclei with a half-life greater than 1000 years", incorporated in the list above. The NUBASE2020 evaluation of nuclear physics properties F.G. Kondev et al. 2021 Chinese Phys. C 45 030001. The PDF of this article lists the half-lives of all known radioactives nuclides.
135 I undergoes beta decay with half-life of 6.57 hours to 135 Xe. The yield of 135 Xe for uranium fission is 6.3%; about 95% of 135 Xe originates from decay of 135 I. 135 Xe is the most powerful known neutron absorber , with a cross section for thermal neutrons of 2.6×10 6 barns , [ 1 ] so it acts as a " poison " that can slow or stop the ...
Xenon-136 is an isotope of xenon that undergoes double beta decay to barium-136 with a very long half-life of 2.11 × 10 21 years, more than 10 orders of magnitude longer than the age of the universe ((13.799 ± 0.021) × 10 9 years). It is being used in the Enriched Xenon Observatory experiment to search for neutrinoless double beta decay.
Because 95% of the xenon-135 production is from iodine-135 decay, which has a 6- to 7-hour half-life, the production of xenon-135 remains constant; at this point, the xenon-135 concentration reaches a minimum. The concentration then increases to the equilibrium for the new power level in the same time, roughly 40 to 50 hours.
Neutron capture (29 barns) slowly converts stable 133 Cs to 134 Cs, which itself is low-yield because beta decay stops at 134 Xe; can be further converted (140 barns) to 135 Cs. 6.3333%: Iodine, xenon: 135 I → 135 Xe: 6.57 h: Most important neutron poison; neutron capture converts 10–50% of 135 Xe to 136 Xe; remainder decays (9.14h) to 135 ...
In this situation it is generally uncommon to talk about half-life in the first place, but sometimes people will describe the decay in terms of its "first half-life", "second half-life", etc., where the first half-life is defined as the time required for decay from the initial value to 50%, the second half-life is from 50% to 25%, and so on.
The high short-term radioactivity of spent nuclear fuel is primarily from fission products with short half-life.The radioactivity in the fission product mixture is mostly due to short-lived isotopes such as 131 I and 140 Ba, after about four months 141 Ce, 95 Zr/ 95 Nb and 89 Sr constitute the largest contributors, while after about two or three years the largest share is taken by 144 Ce/ 144 ...