Emax is the maximum neutron energy and Elim is the boundary separating implicit and analogue capture: below Elim, capture is analogue (i. e. a true capture) and above it is implicit (the weight of neutrons is reduced). In the latter case, the CUT card is useful to specify a minimum neutron weight before killing them.

PRDMP card

When an MCNP calculation is run, a lot of information and the tally results are written in an ‘o’ file, which is easy to read for a human being, but less so for a computer (lots of text). The PRDMP card is useful to save tally results in an ‘m’ file, which has a pretty standard format and is easier to read with a

computer; in addition, MCNP can read the ‘m’ file and plot some results. To produce such a file, the following example is pretty good:

PRDMP 2j -1

(2j means jump the first two entries, and -1 is to write the ‘m’ file).