The Evaluated Nuclear Data File (ENDF) system was developed for the storage and retrieval of evaluated nuclear data to be used for applications of nuclear technology. These applications control many features of the system including the choice of materials to be included, the data used, the formats used, and the testing required before a library is released. An important consequence of this is that each evaluation must be complete for its intended application. If the required data are not available for some particular reactions, the evaluator should supply them by using systematics or nuclear models.
The ENDF system is logically divided into formats and procedures. Formats describe how the data are arranged in the libraries and give the formulas needed to reconstruct physical quantities such as cross sections and angular distributions from the parameters in the library. Procedures are the more restrictive rules that specify what data types must be included, which format can be used in particular circumstances, and so on. Procedures are, generally, imposed by a particular organization, and the library sanctioned by the Cross Section Evaluation Working Group (CSEWG) is referred to as ENDF/B. Other organizations may use somewhat diﬀerent procedures, if necessary, but they face the risk that their libraries will not work with processing codes sanctioned by CSEWG.