Fission Products that come from the MCNP output?

[Aly_19f]

TL;DR Summary

What are the most important fission products?

What are the most important fission products should I include/care about that comes out from the MCNP output?

 

[Alex A]

This depends so much on what question you want to ask MCNP. X and 6 can calculate some forms of depletion but I don't know if they simulate poisoning and every fission product.

Iodine-135 and it's decay to Xenon-135 are especially relevant to reactor operation, but all fission products start as the double humped curve mess you see in textbooks.

https://en.wikipedia.org/wiki/Iodine_pit

If this doesn't help, tell us more about what the problem is.

 

[Astronuc]

Certainly, Iodine-135 and it's decay to Xenon-135 are two important radionuclides. Samarium-149 (σ = 74,500 b) is another important poison, and to a lesser extent Promethium-147.
See - https://en.wikipedia.org/wiki/Neutron_poison#Transient_fission_product_poisons and following section.

For verifying burnup calculations, one would also look at Rh-103, -106; Cs-134/Cs-137; and Nd-143,145, and possibly Nd-146, -148.

 

[rpp]

The answer is also going to depend strongly on what type of system you are modeling. The most important fission products for a thermal system are much different from the most important fission products in a fast system.

For example, Xe-135 is extremely critical in a thermal spectrum, but only modestly important in a fast spectrum.

In practice, the list of "important" fission products is usually tuned for each reactor type.