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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.
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 ...
It has a half-life of about 9.2 hours and is the most powerful known neutron-absorbing nuclear poison (having a neutron absorption cross-section of 2 million barns [21]). The overall yield of xenon-135 from fission is 6.3%, though most of this results from the radioactive decay of fission-produced tellurium-135 and iodine-135.
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.
Cs-134 has a half-life of 2 years and may be a major source of gamma radiation in the first 20 years after discharge. Caesium-135 is a long-lived fission product with much weaker radioactivity. Neutron capture inside the reactor transmutes much of the xenon-135 that would otherwise decay to Cs-135.
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 ...
Xenon-135 accumulation can be controlled by keeping power levels high enough to destroy it by neutron absorption as fast as it is produced. Fission also produces iodine-135, which in turn decays (with a half-life of 6.57 hours) to new xenon-135. When the reactor is shut down, iodine-135 continues to decay to xenon-135, making restarting the ...
The radioactive decay can produce a stable nuclide or will sometimes produce a new unstable radionuclide which may undergo further decay. Radioactive decay is a random process at the level of single atoms: it is impossible to predict when one particular atom will decay.