After about 70 years, many fission products
will have decayed away.
The fuel pellets retain most of the fission products
, while the cladding acts as a second barrier  to contain fission products
that escape from the pellets.
To study the effect of the spray system on in-containment fission product
scrubbing, the multistage methodology has been adopted.
But, in 1982, a Nuclear Regulatory Commission laboratory calculated a hypothetical accident where the fission products
are released into the air and remain suspended indefinitely in respirable form over the nearest highly populated areas.
Burk, "SPARC-90: A code for calculating fission product
capture in suppression pools," Tech.
The long-term release comes from radioactive fission products
in fuel elements caused by the heat up of the core after accidents and it is mainly decided by core temperature.
The detector's sensitivity depends directly on the mean charge deposited by fission products
in the gas .
In the Moltex design, the salt is held in vented tubes, which is possible because the fission products
form compounds a in the salt.
Driven by the decay power of the fission products
and the high temperature, the basemat concrete, which is the last barrier that prevents leakage of the radioactive products into environment in the second-generation NPPs, starts to ablate [1,2].
Depleted bundles contain small amounts of fission products
and fissile plutonium, which are dangerously radioactive.
Caesium-137, or radiocaesium, is a radioactive isotope of Caesium formed as one of the more common fission products
by the nuclear fission of Uranium-235 and other fissionable isotopes in nuclear reactors and nuclear weapons.
This radioactive nucleus, one of the fission products
resulting from the fissioning of uranium, is an effective absorber of thermal neutrons.