Release of FLUKA 4-3.3

Dear FLUKA users,

It is our pleasure to announce that a new minor release of the FLUKA code, version 4-3.3, has been issued and can be downloaded from the Official CERN FLUKA website

See the release notes at the bottom of this message for a detailed account of all novelties, among which we highlight an updated package for JEFF-3.3 pointwise interactions of neutrons below 20 MeV, now embedding improved S(a,b,T) thermal scattering law tabulations. This new package (which supersedes the package offered hitherto) must be explicitly downloaded from:

For consistency, please update to the latest version of Flair.

With our kindest regards,

The FLUKA developer team at CERN and Collaborating Institutes

=== Fluka-4.3.3 ===


  • The JEFF-3.3 package for point-wise neutron interactions below 20 MeV has been updated to include new S(a,b,T) thermal scattering law tabulations. The latter feature a better energy and angle resolution, and now account for 58 binding environments (instead of 20 in the previous version). This new JEFF-3.3 package supersedes the old one, and must be downloaded as usual from

  • The erroneous decay products branchings of 99Tc have been corrected, thus addressing the issue in this forum thread.


  • Fixed a crash (kindly reported by BNL colleagues), whereby a low-energy 197Au+56Fe collision via the BME complete fusion module yielded a transuranic residual nucleus with Z>100 above transport threshold, whose reaction cross section in hydrogen failed to evaluate.

  • Fixed a bug which led to Gaussian energy broadening erroneously applied after events with no energy deposition.

  • Point-wise neutron interactions:

    • For events involving the combined emission of neutrons as well as charged particles, the neutron is now sampled first, thus assuring a more faithful adherence to the inclusive neutron emission spectra of the database.

    • Improved sampling from energy/angle tabular distributions for channels containing different interpolation schemes for various energy intervals.

    • Fixed a bug affecting the Kalbach-Mann slope calculation when not available in the database.