Dear Razieh,
I would recommend you to use LTRACK and ATRACK, which give you the information about the generation number and the age of the projectile neutron, respectively. Its reaction products can be found in the secondary stack (genstk.inc), where neutrons are identified by KPART(I)=8 with I=1,NP.
More general information about what a stack is, you can find in this post. More detailed use of the stacks is explained here.
Please let us know if you have any other questions.
Cheers,
Barbara