Doesn't generated _fort.72 file

I work with the next .inp file during one month.
photonuc.inp (1.3 KB)
The only value I changing all the time was value of incident photons energy. Today program stopped generates _fort.72 file. I absolutely can’t understand the reason. What is the problem ? Here are .f file too.
mgdraw.f (10.2 KB)

Dear user,

If you run your input file with just 1 particle and look in the output file for a table with the header “Inelastic scattering length for PHOTON at beam energy” you’ll see that your 30-MeV photons in NITROGEN undergo a photonuclear interaction on average once every 4300 cm.

Your LAM-BIAS card is unfortunately ineffective: you’re biasing the photon mean free path for photonuclear processes with a factor 1, which leaves it intact. For your 0.1 cm slab you’d need to run a copious amount of primaries (above some ~40000) to begin seeing photonuclear events.

Put a factor a la 1e-3 or 1e-4 in your LAM-BIAS card and you’ll start populating your *_fort.72 file even with moderate number of primaries. Note, that produced secondaries will now carry a statistical weight different than one, which you can pick up from array WEI(:), see include/