**
1. NAME AND TITLE**

ROLAIDS-CPM: Code System to Calculate Group-Averaged Cross Sections Using the Collision Probability Method.

**AUXILIARY ROUTINES:**

PIR: Produce Input Library ROLAIDS-CPM

**2. CONTRIBUTOR**

Netherlands Energy Research Foundation, Petten, The Netherlands.

**3. CODING LANGUAGE AND COMPUTER**

FORTRAN 77 on DEC Alpha and SUN (P00353/SUN04/00).

**4. NATURE OF PROBLEM SOLVED**

This program calculates group-averaged cross sections for specific zones in a one-dimensional geometry. ROLAIDS-CPM is an extension of ROLAIDS from the PSR-315/AMPX-77 package. The main extension is the capability to use the collision probability method for a slab- or cylinder-geometry rather than the interface-currents method. This new version allows slowing down of neutrons in the energy range where the scattering is elastic and upscattering does not occur. The scattering sources are assumed to be flat and isotropic in the different zones. The extra assumption of cosine currents at the interfaces of the zones (interface currents method) is not necessary for the collision probability method.

**
5. METHOD OF SOLUTION**

Collision probabilities in cylindrical geometry are calculated according to the Carlvik Method using a Gauss integration.

**6. RESTRICTIONS OR LIMITATIONS**

The maximum number of zones is 30 for collision probability method.

**7. TYPICAL RUNNING TIME**

The run time on a SUN Sparcstation 10 was 27.86 minutes with 5 Gauss-points, 12 zones and 40214 energy points. Run time is about proportional to the number of Gauss-points, the number of energy-points and the square of the number of zones.

**8. COMPUTER HARDWARE REQUIREMENTS**

The program runs on a SUN or DEC workstation.

**
9. COMPUTER SOFTWARE REQUIREMENTS**

A FORTRAN 77 compiler is required on a Unix-based operating system. ROLAIDS-CPM is not a stand-alone program and users may substitute ROLAIDS-CPM for the original version distributed with AMPX. As of this release date, there is no workstation version of AMPX-77 in the RSIC collection; and because of this ROLAIDS-CPM was not tested by RSIC.

**
10. REFERENCES**

**
a. Included in document:**

W.J.M. de Kruijf, "Updates in ROLAIDS-CPM: 16 up to 25," (1 page)(January 24, 1995).

W.J.M. de Kruijf, "ROLAIDS-CPM: A Code for Accurate Resonance Absorption Calculations," ECN-R-93-013 (August 1993).

W.J.M. de Kruijf, "Benchmark Calculations on Resonance Absorption by 238U in a PWR Pin- Cell Geometry," ECN-R-93-016 (December 1993).

**b. Background information:**

**
** I. Carlvik, "A Method for Calculating Collision Probabilities in General Cylindrical Geometry
and Applications to Flux Distribution and Dancoff Factors," International Conference on the Peaceful
Use of Atomic Energy 3, P/681, (1964)

**11. CONTENTS OF CODE PACKAGE**

The referenced documents and 1 DC6150 tape cartridge written in compressed tar format are included. The compressed tar file contains FORTRAN 77 source files, sample input and output, and an information file.

**12. DATE OF ABSTRACT**

August 1995.

** KEYWORDS**: MULTIGROUP CROSS SECTION PROCESSING; NEUTRON CROSS
SECTION PROCESSING; COLLISION PROBABILITY; SELF
SHIELDING; WORKSTATION