Cannot process some nuclides in the JEFF-3.3 decay library due to malformatted MF=1, MT=451.

[cjosey]

This is an issue with JEFF-3.3 not following the ENDF-6 format, rather than an issue with ENDFtk, but it's worth keeping track of these.

Consider the decay file JEFF33RDD0506_0.ASC, as downloaded from https://www.oecd-nea.org/dbdata/jeff/jeff33/index.html -> Radioactive Decay Data in 3852 files. In the File 1 MT=451 dataset, the data is written as:

[...]
         diff. nuclear             -6.1026 keV      -0.0587 %      506 1451   45
                                                                   506 1451   46
 0.00000+00 0.00000+00          1        451         53          0 506 1451   47
 0.00000+00 0.00000+00          8        457         35          0 506 1451   48
                                                                   506 1  099999
                                                                   506 0  0    0

According to the ENDF-6 format, the first two 0.00000+00 values should not be there. ENDFtk attempts to parse them as an integer and fails.