**1. NAME AND TITLE**

XSDRN: Multigroup One-Dimensional Discrete Ordinates Spectral Averaging Neutron Transport Code System.

AUXILIARY ROUTINES

BX: Produces XSDRN Data from GAM-II/THERMOS Data.

JUANITA: Cross Section Data Converter (BCD to Binary).

SUP: Cross Section Data Library Update Code.

SECS: Cross Section Data Library Edit Code.

FUNCTION SUBROUTINES: ICLOCK, ICOMP, REPLACE, ITIME, MODEL.

DATA LIBRARY

XSDRN Cross Sections.

XSDRN was originally packaged as CCC-123 in 1971 with major updates in 1975 (CDC version) and 1983 (IBM version). Later development, renamed XSDRNPM, is packaged as a module of PSR-63/AMPX-II, PSR-112/MAME, PSR-117/MARS, and CCC-450/SCALE.

**2. CONTRIBUTOR**

Oak Ridge National Laboratory, Oak Ridge, Tennessee.

**3. CODING LANGUAGE AND COMPUTER**

FORTRAN IV; IBM 360 (C00123I036000) and CYBER-73 (C00123C007300).

**4. NATURE OF PROBLEM SOLVED**

XSDRN uses the Nordheim integral treatment, narrow resonance, or infinite mass approximation to process resonance data on a master cross section library and thus obtain microscopic fine-group cross sections for a large number of nuclides. It then uses these cross sections in an independent calculation to solve for fluxes, eigenvalues, critical dimensions, etc., using discrete ordinates, diffusion, or an infinite medium theory calculation. The fine-group fluxes thus obtained can then be used to collapse the fine-group cross section data to a more tenable broad-group structure for use in several independent computer codes.

**5. METHOD OF SOLUTION**

The principal calculations performed by XSDRN (resonance calculation and flux calculation) both employ numerical finite-difference techniques. For the resonance calculation, this involves a Simpson's integration to solve for the collision density in the resonance range. The flux calculations employ a multigroup energy structure, an arbitrary spatial structure, and a mechanical angular quadrature, all of which must be used in the various integration and differencing schemes in the code system. A flexible dimensioning scheme allows optimal use of core storage. A unique method of storing cross sections is employed which eliminates impossible and/or zero transfer cross sections.

The packaged master data library for XSDRN was produced by BX. Cross sections can be generated from this library for input to ANISN, DOT, CITATION, ROD, or EXTERMINATOR-II.

**6. RESTRICTIONS OR LIMITATIONS**

The principal restriction is the availability of adequate core storage to build required arrays. The code is flexibly dimensioned which means that array sizes are set for the particular problem at execution time. Present 123 group cross section library tapes need the 512K byte storage for efficient execution, but could be made to operate on a smaller machine through various out-of-core storage capabilities.

**7. TYPICAL RUNNING TIME**

Resonance calculations: Typical running times on the IBM 360/75 have been on the order of one half to one minute per nuclide. Flux calculation: It is difficult to assign accurate times for the flux calculation since it depends on number of energy groups, number of space points, geometry, calculational option, cross section order, angular quadrature, convergence criteria, and even on out-of-core storage allocation. A typical problem (S4P3, 25 space points, 123 energy groups, cylinder, k-calculation, reduce cross sections, 4 resonance nuclides) generally runs on the order of ten to twelve minutes (total time). A fixed source calculation for the same system would take approximately the same time. Estimated running time of the packaged sample problem on the IBM 360/91: 17 minutes. Time for the CDC version was not noted.

**8. COMPUTER HARDWARE REQUIREMENTS**

XSDRN was designed to use computers in the IBM 360 series with a 512K byte directly-addressable storage. It may be run on IBM 360 or CDC with approximately 90K words of directly addressable core storage available for the program. The various calculational options require from four to thirteen input-output devices, depending on the problem. At least one direct access device must be available.

**9. COMPUTER SOFTWARE REQUIREMENTS**

XSDRN was made operable on the IBM OS 360 with FORTRAN H compiler and on the CYBER-73 system.

The code system consists of approximately 80 subroutines on 6600 source cards. It is presently used in a four level overlay structure consisting of fourteen separate links.

**10. REFERENCES**

N. M. Greene and C. W. Craven, Jr., "XSDRN: A Discrete Ordinates Spectral Averaging Code," ORNL-TM-2500 (July 1969).

K. Laughan, D. Keeton and N. M. Greene, "BX: The Before-XLACS Code," Informal User's Manual (1969).

N. M. Greene, "JUANITA: Instructions for Master Cross Section Library Converter Program," Informal Notes (January 1971).

N. M. Greene, "SUP: Input Requirements for XSDRN Master Cross Section Library Update Program," Informal Notes (January 1971).

N. M. Greene, "SECS: Instructions for Master Cross Section Library Listing Code," Informal Notes (January 1971).

L. L. Bennett, "Recommended Fission Product Chains for Use in Reactor Evaluation Studies," ORNL-TM-1658 (September 1966).

M. L. Tobias and G. W. Cunningham, III, "A Simple Method for Listing Data Sets in Readable Form," ORNL-CF-72-7-32 (July 1972).

**11. CONTENTS OF CODE PACKAGE**

Included are the referenced documents and five DS/HD 3.5-in. (1.44 MB) diskettes in self-extracting compressed DOS files, which contain the source codes, data library, and sample problem input and sample problem output written in list format.

**12. DATE OF ABSTRACT**

August 1971; revised December 1984.

**KEYWORDS:** CROSS SECTION PROCESSING; DISCRETE ORDINATES; ONE-DIMENSION; NEUTRON; MULTIGROUP