Hi Subhrojit,

with the neutron flux being neutrons/cm2-s, the FM card can produce the reaction rate as follows: the microscopic cross section of the (n,p) reaction based on the ENDF-6 format is 103 (please confirm) in barns. Therefore, the F4 multiplication card FM4 should be equal to atoms/barn-cm (this is the atom density in MCNP units) of the target material. Since you are interested in the S-32 reaction rate you should create a "dummy material" that will look something like 16032.80c (for S-32). The result of the tally will be Bq/cm3 and therefore you can multiply by the density to get Bq/g (or Ci if you convert Bq -> Ci). If the dummy material is "m999", and the tally is F14, the FM card should look like this: FM14 Target material atom density (in atoms/barn-cm) 999 103.

I would suggest to do a simple calculation that you can confirm with a hand calculation to make sure the units agree. Provided you can find the cross section of the reaction you are interested in.

I think the MCNP 6.3 manual is available online and you can refer to it.

I hope this helps,

dimitris

Hi Dimitris,

Thank you so much for your answer. I have done the calculation using the method you mentioned. Reaction rates are coming nicely.