**1. NAME AND TITLE**

STRAINT: One-Dimensional Multigroup Neutron Transport Discrete Ordinates Code System.

**AUXILIARY ROUTINES**

ASCOT: Data Generator.

MCORE: Utility Code.

STRAINT was originally written for the IBM 7030 (STRETCH) computer in S2 FORTRAN (a
dialect of FORTRAN) (AWRE 0-12/63). Several variations and modifications have since been
incorporated. It was translated into FORTRAN IV (IBM 360/370) in 1971. Some tape usage has
been replaced by disc, thus reducing the machine time, and some errors in the program have been
isolated and corrected. The AWRE peripheral codes, GALAXY, which prepares multigroup
nuclear data tapes (AWRE 0-56/73), and DUNDEE, which can be used to process output perturbation functions (AWRE 0-36/73), are not packaged in RSIC.

**2. CONTRIBUTOR**

AWRE, Aldermaston, Reading, Berkshire, England.

**3. CODING LANGUAGE AND COMPUTER**

FORTRAN IV and Assembler language; IBM 360/370.

**4. NATURE OF PROBLEM SOLVED**

The multigroup stationary transport equation in plane or spherical geometry is solved for
neutron or gamma fluxes by the Carlson Sn method (discrete ordinates, LA-1891). The equation
may be homogeneous or inhomogeneous (imposed source present), and neutron scatter can be
isotropic or anisotropic. Neutrons from fission are assumed to be emitted isotropically. The
homogeneous equation may be solved to determine whether a system is subcritical or supercritical,
or some parameter may be varied until the system is critical. Such a parameter may determine the
geometry of the system, the time constant, or the nuclide proportions. The imposed source may be
a distributed source emitting neutrons isotropically, a shell source emitting neutrons radially or a
parallel beam source moving through the system. The latter may be used to simulate a shell source
of any angular emission.

**5. METHOD OF SOLUTION**

STRAINT employs the Carlson S_{n} (discrete ordinates) method.

**6. RESTRICTIONS OR LIMITATIONS**

Total storage available is the only limiting factor on the problem size. The basic program
occupies approximately 180 K of storage, but all common arrays are dimensioned dynamically and
so this figure is increased according to the size of the problem. As a rough guide, a calculation
using 10 neutron groups and 3 materials each with 10 mesh points will require a total of approximately 200 K of storage, while one using 32 neutron groups and 5 materials each with 10 mesh
points will require approximately 400 K of storage. Few problems will require more than 600 K.

**7. TYPICAL RUNNING TIME**

On the 370/185 the two problems mentioned above took approximately 6 seconds and 3 1/2 minutes CPU time, respectively. Few problems will require more than 7 minutes CPU time.

The packaged sample problem ran as follows: ASCOT10 minutes on the IBM 360/75;
STRAINT7 minutes on the IBM 360/91.

**8. COMPUTER HARDWARE REQUIREMENTS**

STRAINT is operable on the IBM 360/370 computers, using eleven storage media, three of
which are direct access. ASCOT requires 122 K; STRAINT uses 420 K. Clock is sampled.

**9. COMPUTER SOFTWARE REQUIREMENTS**

A FORTRAN IV compiler is required. MCS4 routine is in Assembler language.

**10. REFERENCE**

K. Dugan and J. A. Price, "A FORTRAN IV Version of the AWRE One-Dimensional
Multigroup Neutron Transport S_{n} Program STRAINT," AWRE 042/73 (1973).

**11. CONTENTS OF CODE PACKAGE**

Included are the referenced document and one (1.2MB) DOS diskette which contains the source
code and sample problem input and output.

**12. DATE OF ABSTRACT**

August 1975.

**KEYWORDS: ** MULTIGROUP; NEUTRON; DISCRETE ORDINATES; ONE-DIMENSION