On December 22, 2011, ENDF/B-VII.1 was released. This library included hundreds of new and improved evaluations. Inevitably, it also contains a few errors. On this page we list the most serious of those issues.

Major Issues:

• SiO₂ LEAPR bug The ENDF/B-VII.1 thermal neutron scattering data for SiO₂ were generated by North Carolina State University using NJOY's LEAPR module. Unfortunately, the there was a bug in LEAPR that only affects whole-molecule files with non-1:1 stoichiometry. It seems that this was the first whole-molecule thermal library published for a material with non-1:1 stoichiometry, so no one had ever encountered this issue before. The bug was documented, a work-around was developed, and correct libraries were then generated. Using the original library version will result in cross sections that are off by 40% or more. The SiO₂ evaluation was replaced by two evaluations for alpha and beta phase SiO₂ in subversion commit #619 on 15 Nov. 2013.
• H1 covariance The ENDF/B-VII.1 neutron scattering data for ¹H were developed as part of the Neutron Standards evaluation by G. Hale at Los Alamos National Laboratory. The high fidelity covariance file that was to accompany the evaluation was not included while an older one was included. The correct covariance data was added in subversion commit #610 in 12 April 2013.
• Energy balance This is by far the most commonly reported issue in the history of the ENDF project. In ENDF/B-VII.1 alone, energy balance tracker items were added here, here, here and here. The ADVANCE continuous integration system for ENDF found that nearly 80% of the data files in the neutron sublibrary have energy balance problems of one form or another. In fact, this class of errors have been reported as early as the late 1970's (R.E. MacFarlane, "Energy Balance of ENDF/B-V", Trans. Am. Nucl. Soc. 33, 681 (1979)). One would think that such a well known issue would have been resolved by now. However, one must realize that the smallest mistake in a file (say an outgoing energy table extending 1 eV too far in E') can result in an energy or momentum imbalance. The most common cause of large imbalances is the lack of outgoing gamma data in many older evaluations. Energy imbalances are much less in newer evaluations but correcting the energy balance in older evaluations is notoriously difficult.