User's manual for the NEFTRAN computer code

This document describes the NEFTRAN (NEtwork Flow and TRANsport) computer code and provides the reader with enough detailed information to use the code. NEFTRAN was developed for the assessment of ground-water flow and radionuclide transport in high-level radioactive waste repositories mined in deep saturated and fractured geologic formations. NEFTRAN is a successor to NWFT/DVM and contains several new capabilities. These are generalized flow network, matrix diffusion, leg transfer, mixing cell, and multiple chains. This document's four main sections describe the mathematical representation of ground-water flow, radionuclide transport, matrix diffusion, source term, and leg-transfer models; the program and subprograms in the code; the input to the code; and sample problems highlighting each of the new capabilities of the code. 18 refs., 22 figs., 9 tabs