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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.
The iodine pit, also called the iodine hole or xenon pit, is a temporary disabling of a nuclear reactor due to buildup of short-lived nuclear poisons in the reactor core. The main isotope responsible is 135 Xe, mainly produced by natural decay of 135 I. 135 I is a weak neutron absorber, while 135 Xe is the strongest
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 inside the reactor transmutes much of the xenon-135 that would otherwise decay to Cs-135. Caesium-137, with a half-life of 30 years, is the main medium-lived fission product, along with Sr-90. Cs-137 is the primary source of penetrating gamma radiation from spent fuel from 10 years to about 300 years after discharge.
Xenon-136 is produced when xenon-135 undergoes neutron capture before it can decay. The ratio of xenon-136 to xenon-135 (or its decay products) can give hints as to the power history of a given reactor and the absence of xenon-136 is a "fingerprint" for nuclear explosions, as xenon-135 is not produced directly but as a product of successive ...
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.
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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.: 135 Xe capturing a neutron and becoming nearly stable 136 Xe, rather than decaying to 135 Cs which is radioactive with a half-life of 2.3 million years