1. NAME AND TITLE OF DATA LIBRARY

RITTS: 121-Group Coupled Neutron and Gamma-Ray Cross-Section Data for Transport Codes.

2. NAME AND TITLE OF DATA RETRIEVAL PROGRAMS

JRMACRO: A Program for Converting Microscopic, Multigroup, P_n Expansion Cross-Section Data into Corresponding Macroscopic Data for Mixtures or Compounds.

3. CONTRIBUTORS

Oak Ridge National Laboratory, Oak Ridge, Tennessee.

Computing Technology Center, Union Carbide Corporation, Nuclear Division, Oak Ridge, Tennessee.

4. HISTORICAL BACKGROUND AND INFORMATION

The RITTS library was developed during the course of investigations by J. J. Ritts and others at Oak Ridge National Laboratory. JRMACRO is a mixing code which was developed by Ritts with assistance from Computing Technology Center personnel. Further refinements were implemented by the RSIC staff.

5. APPLICATION OF THE DATA

DLC-11/RITTS data is suitable for neutron, gamma-ray, or coupled neutron and gamma-ray transport calculations. It is intended for use in multigroup discrete-ordinates or Monte Carlo transport codes which treat anisotropic scattering by Legendre expansion up to order P₃.

6. SOURCE AND SCOPE OF DATA

DLC-11/RITTS is a collection of multigroup cross-section data which were compiled by J. J. Ritts for use in depth-dose calculations in anthropomorphic phantoms. For convenience, the data are grouped as follows:

1. A coupled 121-group (100 neutron, 21 gamma-ray) set of data for the eleven elements, H, C, O, N, Na, Mg, P, S, Cl, K, and Ca. This set includes P₃ coupled 121-group microscopic cross-sections plus 121-group kerma factors for the eleven elements.

2. A 100-group set of neutron cross sections for the eleven elements.

3. A coupled 121-group set of macroscopic cross sections for nine organic materials including 11-element standard man, 4-element standard man, skin, bone, tissue, brain, lung, red marrow, and muscle.

The neutron multigroup cross sections were generated at the Computing Technology Center. The basic data sources were ENDF/B for H, C, N, O, Na, and Mg, the CCC-17/O5R library for Ca, S, and K, the GAM-II library for Cl and an evaluation by Ritts for P. A "1/E" spectrum was assumed for averaging the top 99 groups and a Maxwellian for averaging the thermal group values.

The gamma-ray cross sections were computed from DLC-3/HPIC using MUG.

The neutron-to-gamma-ray group transfer cross sections were generated, using PSR-11/POPOP4, with account being taken for neutron capture, inelastic scattering, and other neutron reactions.

The 100-group neutron kerma factors were generated by DLC-10/AVKER and the 21-group gamma-ray kerma factors by MUG.

The DLC-11/RITTS cross sections represent a P₃ approximation to elastic (or Compton) scattering angular distributions. The 100 neutron groups cover an energy range from 14.92 MeV to thermal. For gamma rays, 21 energy groups cover the range from 14.0 to 0.01 MeV.

7. DISCUSSION OF THE DATA RETRIEVAL PROGRAM

The retrieval program is called JRMACRO and is used to read microscopic, multigroup, Pn expansion cross-section data, "mix" this data into macroscopic cross-section data as needed, and write the resulting set in a suitable output format. The cross-section data considered here is of the general type used by particle transport computer codes such as CCC-42/DTF-IV, CCC-82/ANISN-CEA, CCC-89/DOT, AND CCC-127/MORSE. JRMACRO manipulates DLC-11/RITTS such that it conforms to the input requirements of the aforementioned codes.

JRMACRO accepts input cross sections by means of cards, tape written in card image format, an unformatted tape (binary), or a combination of the above. Formatted input (cards or card image tape) is first read and stored on a tape or disk before any mixing of cross-section data is performed.

The output cross-section data may be in the form of a card image tape, an unformatted tape, or both.

JRMACRO was used to convert unformatted library tapes for CCC-82/ANISN-CEA into the card image format in which DLC-11/RITTS is distributed.

8. DATA FORMAT AND COMPUTER

BCD card images; IBM 360/370. The data is written in the special format used for card input to the ANISN-CEA code.

9. TYPICAL RUNNING TIME

The sample problem runs in approximately 45 s cpu time, 230 s total time, on an IBM 360/91 computer. The problem involves reading the 100-group neutron data for C, Na, and K, multiplying all data by 1.0, and writing the result on an unformatted tape (a way, although inefficient, to convert from card image tape to unformatted tape).

10. REFERENCES

J. J. Ritts, R. W. Roussin, and I. J. Brown, "JRMACRO: A Program for Converting Microscopic, Multigroup, Pn Expansion Cross Section Data into Corresponding Macroscopic Data for Mixtures or Compounds," ORNL-TM-3052 (March 1970).

J. J. Ritts and R. W. Roussin, "121 Group Coupled Neutron and Gamma-Ray Cross-Section Library for Transport Codes (100 Neutron, 21 Gamma-Ray Groups)," Informal note.

R. W. Roussin, "Using ANISN to Reduce the DLC-2 100 Group Cross-Section Data to a Smaller Number of Groups," ORNL-TM-3049 (May 1969).

J. J. Ritts, M. Solomito, and P. N. Stevens, "The Calculation of Neutron-Induced Physical Doses in Human Tissues," ORNL-TM-2991 (May 1970).

11. CONTENTS OF LIBRARY

Included are the referenced documents and one tape cartridge in TAR format which contains the library and the retrieval program source code, sample problem input, plus output from the retrieval program.