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Joint Evaluated Fission and Fusion (JEFF) Library version 4.0 test 1

The JEFF-4T1 nuclear data library content has been agreed upon in February 2022. It includes two sets of data containing 562 and 2813 neutron cross section evaluations, respectively.

Superseded test library

Please note that this is a superseded test library that has not been approved for formal release and has been replaced with another test library version. The latest official release remains JEFF-3.3.

Neutron cross section evaluations

The first set, as the previous versions of JEFF, includes the 562 most important isotopes for criticality calculations. The content of the library is described in the JEFF-4T1 Starter File. The second one includes the 562 isotopes of the previous set, but it is completed by the additional 2251 isotopes provided by TENDL-2021. This set is recommended for more general purposes.

Thermal scattering law data

The Thermal Scattering Law set includes 24 files, 19 of which are taken from JEFF-3.3. New evaluations are provided for H(H20), PuO2, and UO2. O(H2O) is taken from JENDL-5, while H(Lucite) is taken from ENDF/B-VIII.O. The TSL content in listed in the JEFF-4T1 Starter File.

Evaluated files

Release Format Content # files Size Download
JEFF-4T1 ENDF-6 Cross section evaluations 563 511 MB Link
JEFF-4T1 ENDF-6 Cross section evaluations 2813 2.6 GB Link
JEFF-4T1 ENDF-6 TSL evaluations 24 180 MB Link

Processed files

Release Format Code(s) used Content # files Size Download
JEFF-4T1 ACE, XSDIR, NJOY inputs NJOY Continuous energy, 293K 563 1.0 GB Link
JEFF-4T1 ACE, XSDIR, NJOY inputs NJOY H in H2O, 293K 1 40 MB Link
JEFF-4T1 HDF5 OpenMC Continuous energy, 293K 563 1.1 GB Link

Developer access

The repositories containing the evaluated data and all processing pipelines, including the containerised execution of codes that generate all processed data in the tables above, are located on the NEA GitLab.


Access to the NEA GitLab and to the JEFF Lab is restricted to JEFF delegates. Please contact for more information.