A bit of history

Originally, the access routines, called ndf access routines, were a set of LLLTRAN routines, it is claimed, built into a library named libndf.a. LLLTRAN was a version of FORTRAN, with extensions, developed at Lawrence Livermore National Laboratory and dates back to at least the 1970s. The ndf routines were incomplete in that some essential knowledge of the data could not be obtained through the access routines; it had to be known or guessed by the code developer. For example, the routine ndfistab returns a list of all targets and the number of targets. Memory for the target list is allocated by the calling routine. If memory for the target list is insufficient a memory overwrite will occur. In the old routines there was no way to determine the number of targets prior to calling ndfistab so that appropriate memory could be allocated. Starting sometime in the late 1990's, routines have been added to overcome any deficiencies. For example, a routine ndfnistab as been added which returns the number of targets in the opened ndfy_{$\bf i$} file. C-wrapper routines have also been added and a C-header file ndf.h exist for C programming. The FORTRAN routines have the prefix ndf and the C-wrapper routines have the prefix ndfc.

Some of the concepts and equations used to calculate the data can also be found in reference [1], in particular chapters VI and VII, and in reference [2].

The data in the ndfy_{$\bf i$} files is a "processed" form of the data from three nuclear databases developed at LLNL. One database contains information about neutron incident on various targets and is called ENDL (Evaluated Neutron Data Library). Another database contains information about the 5 supported transportable charged particles (p, d, t, ³He, and $\alpha$) incident on various targets and is called ECPL (Evaluated Charged Particle Library). The last database contains information about gammas ($\gamma$s) incident on various targets and is called EGDL (Evaluated Gamma Data Library). These databases represent the data in point-wise form. For example, cross-section data is given as 2-column data where the first column is the incident energy in MeV and the second column is the cross-section in barns; as the following lines demonstrate,

 1.2510000E+01  0.00000E+00
 1.4000000E+01  2.00000E-02
 2.0000000E+01  2.00000E-02

This data is converted from point-wise data into grouped data (see Section 4) to form the ndfy_{$\bf i$} files and is then called processed data. In the future, the LLNL Nuclear Computations Group may make evaluated data from other databases (e.g., the ENDFB5 database from Brookhaven National Laboratory) available as ndfy_{$\bf i$} files.

The acronym ENDL as two derivations. At times it will derive from Evaluated Neutron Data Library. At other times it will derive from Evaluated Nuclear Data Libraries. In this latter version, nuclear implies all three databases (ENDL, ECPL and EGDL). Hopefully, the appropriate meaning for this acronym will be clear when it is used at various places in this document.