Introduction

This document describes the routines, provided by the LLNL Computational Nuclear Physics Group, that access the data stored in the ndfy_{$\bf i$} files where y_i is a token to be replaced by a 1, 2, 3, 4, 5, 6 or 7 (e.g., ndf1). These files contain nuclear (y_i = 1 to 6) and atomic gamma-ray (y_i = 7) data required by deterministic transport codes. Such codes transport particles through a composite material as particles are destroyed and created through interactions with the composite material. The various ndfy_{$\bf i$} files contain data so that the particles listed in Table 1, called transportable particles, can be transported through various composite materials. Within a ndfy_{$\bf i$} file is a list of targets (also called isotopes) for which there are data for reactions induced by its transportable particle. A composite material is a combination of one or more of these targets. For each target there is a list of nuclear reactions (or atomic gamma-ray reactions for the ndf7 file) for which there are data for that target. Section 5 describes the type of data stored in a ndfy_{$\bf i$} file for each target.

For example, consider a material composed of only Uranium 238, ²³⁸U, for which one would like to transport neutrons. Since only neutrons are being transported, only the ndf1 file needs to be accessed. The ndf1 file may contain ²³⁸U with data for the nuclear reactions listed in Table 2. Various data, like total cross-section, fission spectrum, etc., are stored for the ²³⁸U target. The last reaction listed in the Table 2, capture, creates a $\gamma$ particle. The energy and angular distribution information about the created $\gamma$s are available in the ndf1 file (i.e., transport matrix and deposited energy). In order to transport $\gamma$s the ndf7 file would need to be access.

In this document, an incident transportable particle is labeled y_i and an outgoing (appearing on the right-hand-side of the reaction equation) transportable particle is labeled y_o. Some reactions may have more than one type of outgoing transportable particle (e.g., (n,p $\alpha$) has a proton and an alpha as outgoing particles).

Table 1: Transportable particles and their corresponding y_i and file name.

yi	File name	Transportable particle name
1	ndf1	Neutron (n)
2	ndf2	proton (p)
3	ndf3	Deuteron (d)
4	ndf4	Triton (t)
5	ndf5	Helium 3 (3He)
6	ndf6	Helium (4He) also called alpha ($\alpha$)
7	ndf7	gamma ($\gamma$)

Table 2: Example of reaction data for ²³⁸U in a ndf1 file.

n +  238U $\rightarrow$ n +  238U	! Elastic scattering
n +  238U $\rightarrow$ n' +  238U	! Inelastic scattering
n +  238U $\rightarrow$ n + n +  237U	! (n,2n)
n +  238U $\rightarrow$ n + n + n +  236U	! (n,3n)
n +  238U $\rightarrow$ n + n + n + n +  235U	! (n,4n)
n +  238U $\rightarrow$ various neutrons + fission fragments	! Fission
n +  238U $\rightarrow$ $\gamma$ +  239U	! Capture