**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.

**KEYWORDS:** REACTOR PHYSICS; REACTOR PHYSICS