Dear @riya,
In the plot I attached above, the blue histogram from FLUKA is the output of the mgdraw, filtered on NPHEAVY=2, while the orange one is the “theoretical one”:
“In each fission event the number of neutrons emitted must be an integer. For a very large number of fissions of U-235 by thermal neutrons it is known that 2.7% of the fissions give no neutrons, 15.8% give one neutron, 33.9% give two, and so on. The average number of neutrons released per fission is denoted by v and has a value of 2.43 for thermal fission in U-235.” From: Fission Event - an overview | ScienceDirect Topics
Best,
Daniel