**1. NAME AND TITLE**

DTF-IV: Multigroup Neutron Transport Discrete Ordinates Code System with One-Dimensional, Anisotropic Scattering.

**AUXILIARY ROUTINE**

GAMLEG: Photon Transport Cross-section Generator.

An early version of the code, DSN, was developed in the FLOCO language by Bengt Carlson of LASL. A revision of DSN, called DTK, was written to incorporate convergence technique and ease of operation. DTF is the FORTRAN version of DTK written by UNC and LASL personnel. DTF-IV is a complete revision of DTF. The major features of the revision are the incorporation of a general anisotropic scattering capability and the use of FORTRAN IV programming language. DTF-IV differs in other respects. An up-scatter scaling procedure was added to accelerate and improve convergence in problems with scattering from low energies to high energies. An optional point-wise convergence test was incorporated, and a neutron conserving correction routine was introduced to prevent negative fluxes.

Between 19641981, RSIC distributed the code package 58 times.

**2. CONTRIBUTOR**

Los Alamos National Laboratory, T Division, Los Alamos, New Mexico.

**3. CODING LANGUAGE AND COMPUTER**

FORTRAN IV; IBM 360/370 and CDC 6600.

**4. NATURE OF PROBLEM SOLVED**

The linear, time-independent, Boltzmann equation for particle transport is solved for the energy, space, and angular dependence of the particle distribution in one-dimensional slabs, cylinders, and spheres. Independent source or eigenvalue (multiplication, time absorption, element concentration, zone thickness or system dimension) problems are solved subject to vacuum, reflective, or periodic boundary conditions.

Given source and absorption energy dependence, GAMLEG provides group averaged cross
sections for input to the DTF or DDF codes. Up to N (N < 10) Legendre transfer coefficients for
the cross sections are prepared. Three weighting options are available: unweighted, source energy
weighting, and weighting with input flux.

**5. METHOD OF SOLUTION**

DTF-IV is designed to solve, by the methods of discrete ordinates (Carlson S_{N}), the multigroup, one-dimensional (plane, cylinder, sphere) Boltzmann transport equation. Anisotropic scattering
is represented by Legendre polynomial expansion of the differential scattering cross section. A
complete energy-transfer scattering matrix is allowed for each Legendre component of scattering
cross-section matrices.

Energy dependence is treated by the multigroup approximation and angular dependence by a general discrete ordinates approximation. Anisotropic scattering is approximated by a truncated spherical harmonics expansion of the scattering kernel. Within-group scattering and up-scattering (if any) iteration processes are accelerated by system-wide renormalization procedures.

General anisotropic scattering capability is provided in each of the three geometries, up-scattering convergence acceleration is used, and a neutron conserving negative flux correction routine is used.

GAMLEG provides cross sections for photon transport problems in a form suitable for input to
DTF-IV.

**6. RESTRICTIONS OR LIMITATIONS**

The variable dimensioning capability of FORTRAN IV has been utilized so that any combination of number of groups, number of spatial intervals, size of angular quadrature, etc., can be used
that will fit within the total core storage available to a user. The code itself requires about 8000
words, but it can be shortened by deleting certain subroutines which perform optional calculations.

**7. TYPICAL RUNNING TIME**

No current information noted.

**8. COMPUTER HARDWARE REQUIREMENTS**

The IBM 360/370 or the CDC 6600/7600 may be used. No discs or tapes are used. A clock is
used but, by removing a few program statements, this requirement can be eliminated.

**9. COMPUTER SOFTWARE REQUIREMENTS**

DTF-IV was designed for the IBM 7030 FORTRAN IV Monitor System. It has been made
operable on the IBM 360/370 series and the CDC 6600/7600 series computers.

**10. REFERENCES**

G. Duffy, "IBM 360 Conversion changes (DTF IV)," Argonne National Laboratory, Informal Notes.

K. D. Lathrop, "DTF-IV, a FORTRAN-IV Program for Solving the Multigroup Transport Equation with Anisotropic Scattering," LA-3373 (November 1965).

K. D. Lathrop, "GAMLEG: A FORTRAN Code to Produce Multigroup Cross Sections for Photon Transport Calculations," LA-3267 (April 1965).

B. G. Carlson, W. J. Worlton, W. Guber, and M. Shapiro, "DTF Users Manual," UNC
Phys/Math-3321, Vol. I and II (November 1963).

**11. CONTENTS OF CODE PACKAGE**

The package contains the referenced documents and one (1.2MB) DOS diskette on which is
writtenin separate filesthe source card deck; sample problem input; output from sample problem;
the GAMLEG source card deck, and input and output for a sample problem.

**12. DATE OF ABSTRACT**

July 1967; updated July 1981, April 1984.

**KEYWORDS: ** DISCRETE ORDINATES; ONE-DIMENSION; NEUTRON; GAMMA-RAY