1. NAME AND TITLE

DASQHE: Calculates Dancoff Corrections Factors.

2. CONTRIBUTORS

Aktiebolaget Atomenergi, Stockholm, Sweden, through OECD Nuclear Energy Agency Data Bank, Gif-sur-Yvette France.

3. CODING LANGUAGE AND COMPUTER

Fortran; VAX 8810.

4. NATURE OF PROBLEM SOLVED

DASQHE produces Dancoff corrections for an infinite array of circular rods placed in a square or hexagonal lattice in a moderator. The Dancoff correction is the relative reduction in the in-current of resonance neutrons into the fuel in a closely packed lattice, compared to the in-current into a single fuel rod in an infinite moderator, due to the shadowing effect of adjacent rods. The calculation may be done for a series of moderator cross sections if desired.

5. METHOD OF SOLUTION

A collision probability method is used. The trapezoidal rule is used for the integration of the Dancoff correction double integral, the linear and angular variables being discretized. Instead of considering a series of pairs of rods, a straightforward ``chopper'' method is utilized that disregards rods after a certain distance. The effects of the fuel can (and gas coolant channel) is approximated by the homogenization of a gap surrounding each rod.

6. RESTRICTIONS OR LIMITATIONS

The neutron path is followed through 100 rows of rods if no intersection is found, that is the Dancoff correction is calculated for the central rod in an array of 201 x 201 rods. Even for the smallest moderator cross section used in the calculations, the distance to the nearest disregarded rod is 10 mean free paths.

7. TYPICAL RUNNING TIME

About 2 seconds per Dancoff factor are required on a VAX 8810 computer. NEA-DB ran the test case included in this package in about 40 minutes of CPU time.

8. COMPUTER HARDWARE REQUIREMENTS

DASQHE is a Fortran IV development of the code DANCOFF-5 which was written in Autocode for the Ferranti Mercury computer of AB Atomenergi. Previous Mercury Autocode programs were DANCOFF-2 and DANCOFF-4. NEADB tested DASQHE on a VAX 8810.

9. COMPUTER SOFTWARE REQUIREMENTS

DASQHE needs to be called from another program, or run with a simple user-written main routine. The VMS V5.0-1 operating system was used at NEADB.

10. REFERENCES

E. Sartori, "Dancoff Corrections and Factors from DASQHE," Informal documentation from NEADB (1989).

I. Carlvik, "Dancoff Correction in Square and Hexagonal Lattices," AE-257 (1966).

11. CONTENTS OF CODE PACKAGE

Included are the referenced document and one (1.2MB) DOS diskette which includes an information file, sources, sample problem input and output.

12. DATE OF ABSTRACT

June 1990.