Release of FLUKA 4-3.1

Dear FLUKA users,

It is our pleasure to announce that a new minor release of the FLUKA code, FLUKA 4-3.1, has been issued and can be downloaded from here.

See the release notes at the bottom of this message for a detailed account of all novelties. Many thanks to all users who reported the issues here addressed.

For consistency, please update to the latest version of Flair, available from here

Please note that low-energy neutron libraries, previously downloaded for enabling point-wise interactions, do not need to be downloaded again.

With our kindest regards,

The FLUKA developer team at CERN and Collaborating Institutes


=== Fluka-4.3.1 ===


  • Reworked sampling of the target nucleus thermal motion for the elastic scattering of thermal neutrons, correcting an artifact that led to neutron fluxes slightly skewed towards energies lower than kT, affecting in particular light target nuclei.

  • The parametrized reaction cross section of protons on deuterium below 5.5 MeV was refined to better reproduce experimental data available from EXFOR for the (p,g) and (p,n) channels, removing an unphysical rise below few MeV.


  • Nuclear recoils with the same atomic and mass number as the target isotope  now contribute to RESNUCLEi scoring only when reaching a different geometry region.

  • Kshort and Klong scorings now also include the respective contribution of K0 and K0bar, and viceversa.

  • A simplified version of mgdraw (mgdraw_empty.f) is now offered for convenience, in addition to the original mgdraw.f.


  • Fixed a bug affecting point-wise fission events by low-energy neutrons, removing the spurious survival of the projectile.

  • Fixed a bug whereby deuterium content was suppressed from natural hydrogen when requesting thermal scattering via the S(a,b) treatment.

  • Two bugs were addressed in the crystal channeling module concerning the volume acceptance region: fixed a misbehavior in the limit case of straight crystals + fixed a spurious decrease of the nuclear interaction rate.

  • Fixed a rare bug manifesting when the code was trying to recover a geometry tracking failure and parentheses were used in the region description, addressing this forum post

  • Fixed an error introduced in v4-3.0 affecting the scoring of the restricted NIEL (RES-NIEL).

  • Fixed improper account of optical photon sensitivity for local energy depositions, addressing the issue reported in this forum post

  • Fixed unintended passage through scoring routines after unsuccessful (i.e. rejected during sampling) electronuclear event, addressing the issue reported in this forum post

  • Fixed numerical excursion into negative kinetic energies in electric field tracking when particles reach a turning point, addressing the issue reported in this forum post and fixing an index out of bounds.