**1. NAME AND TITLE**

PRE-ANISN: A Preprocessing Code
for ANISN and Other Radiation Transport Codes.

**2. CONTRIBUTOR**

National Accelerator Centre, Republic
of South Africa.

**3. CODING LANGUAGE AND COMPUTER**

An interactive, personal computer-based
preprocessing code, PRE-ANISN, was developed to automate the task of preparing
source term and response conversion factor input for several radiation
transport and transport related codes. The code prepares multigroup source
spectra for SORREL, and multigroup volume distributed fixed source arrays
for the 1-dimensional discrete ordinates transport codes ANISN and
XSDRNPM. It prepares multigroup fluence rate to response conversion
factors for AXMIX, (a cross-section preprocessing code for ANISN and DOT
3.5), ANISN and DOT 3.5. PRE-ANISN also prepares source terms and response
conversion factors for adjoint transport calculations.

**4. NATURE OF PROBLEM SOLVED**

See PRE-ANISN documentation for details.

**5. METHOD OF SOLUTION**

Preparing a multigroup spectrum:

If a built-in or user-supplied source spectrum is selected, multigroup source-spectra are determined by numerically integrating the chosen spectrum function over the energy partition. (Integration scheme: Simpson's method.) If a tabular source spectrum is supplied, a linear function is formed by linear interpolation between the supplied (Energyital i,Spectrumital i) data points. Integration then proceeds as above.

Preparing a 1-dimensional multigroup volume-distributed fixed source:

It is assumed that the energy & spatial dependence of the source term is separable, i.e. Bold ITAL Q (Bold ITAL E,ital x) alpha Bold ITAL N(Bold ITAL E) Bold ITAL P(ital x). The 1-D volume-distributed fixed source isBold ITAL Q sub ital {gi} = Bold ITAL N sub ital g Bold ITAL P (x bar sub ital i), where Bold ITAL N sub ital g is the multigroup energy spectrum calculated in the previous step, and x bar sub ital i is the midpoint of the ital i'th spatial interval. The spatial power distribution function ITAL P(ital x) is formed by linearly interpolating between relative power values specified at certain locations inside the source region.

Preparing a multigroup response function:

The response function is evaluated
at the midpoint of every energy group. Linear interpolation is used between
the data pairs of tabular response functions.

**6. RESTRICTIONS OR LIMITATIONS**

Maximum number of energy groups: 130

Maximum number of spatial intervals: 1000

Maximum length of spectrum table
or response function table: 1500 data pairs. The assumption is made that
the energy and spatial dependence of the source term is separable.

**7. TYPICAL RUNNING TIME**

One to five minutes on a 33 MGz
80406DX PC. The numerical integration required to evaluate the spectrum
integrals takes about 75% of this time.

**8. COMPUTER HARDWARE REQUIREMENTS**

An 80ital x86 PC with ital x >=
3, a hard disk and at least 4 MBytes of RAM. A 1 MByte ramdisk speeds up
I/O considerably. A math-coprocessor is necessary for use with the supplied
executable. There are no special graphics as printing capabilities, therefore
a CGA or better with a dot matrix lineprinter is sufficient.

**9. COMPUTER SOFTWARE REQUIREMENTS**

The Lahey F77L-EM/32 version 5.01
was used to compile the PRE-ANISN source code. PharLap DOS Extender was
used to link the PRE-ANISN object file to extended memory managers. The
executables requires an external error file "F77L3.EER" to be present when
running PRE-ANISN under supplied with the distribution diskette.

**10. REFERENCE**

Van Rooyen, T.J., "PRE-ANISN, A
Preprocessing Code for ANISN and Other Radiation Transport Codes," NAC
Report NAC/91-06 (December 1991).

**11. CONTENTS OF CODE PACKAGE**

Included are the referenced document
and a 5.25-in. DS/HD (1.2MB) diskette which includes source program, executable,
sample input and output files in compressed mode.

**12. DATE OF ABSTRACT**

March 1993.

**KEYWORDS:** MULTIGROUP; ANISN; PREPROCESSING;
CODE; SPECTRUM; SOURCE TERM; RESPONSE; CONVERSION FACTOR; VOLUME DISTRIBUTED
FIXED SOURCE; RADIATION TRANSPORT CALCULATIONS; DOSE RATE