**1. NAME AND TITLE**

QADMOD-G: Point Kernel Gamma-Ray Shielding Code.

**2. CONTRIBUTOR**

Radiation Research Associates, Fort Worth, Texas.

**3. CODING LANGUAGE AND COMPUTER**

Fortran IV, Assembler language; IBM 3033/3081.

**4. NATURE OF PROBLEM SOLVED**

QAD is the generic designation for a series of point-kernel computer programs designed for estimating the effects of gamma-rays and neutrons that originate in a volume-distributed source. QADMOD is a modified version of the QAD P-5 point-kernel computer program designed to consider only gamma-ray sources. QADMOD-G has new geometry routines, additional source routines, and internal library data which make the program easier to use. Gamma-ray dose rates, energy depositions, and uncollided fluxes may be calculated. Surfaces, defined by quadric equations, are used for a three-dimensional description of the configuration.

**5. METHOD OF SOLUTIONS**

QADMOD-G calculates gamma-ray fluxes, dose rates, or heating rates at discrete locations within a complex source-geometry configuration by representing a volume-distributed source by a number of point isotropic sources and computing the distances through all regions traversed by the line-of-sight from the source points to a desired receiver point. From these distances and the characteristics of the materials within them, energy-dependent exponential attenuation factors and energy-dependent buildup factors for gamma-rays are applied to calculate the direct gamma-ray dose and the gamma-ray dose with buildup. The responses to individual source points are summed into source-energy groups and recorded. Input data consists of the source distribution and intensity, the physical geometry, and may include tabulations of attenuation coefficients, buildup factor coefficients, and conversion factors.

Each source may be represented by a volume-distributed source or a series of up to 27 000 point sources. The source spectra are assumed to be constant for all volumes. The source may be defined in terms of a cylindrical, a cartesian, or a spherical-geometry coordinate system.

As many as 500 point isotropic sources defined in terms of a spatial position and power density may be used in point source calculations. Each point source is represented by the same specified energy spectrum.

Shield configurations are represented in terms of a three-dimensional model which is made up of a series of material and void regions. Each region is defined by a previously-described set of surfaces.

**6. RESTRICTIONS OR LIMITATIONS**

The radiation source is represented by a series of individual point isotropic sources. For gamma-ray calculations, the direct beam component is calculated exactly. The scattered component is calculated using buildup factors. The code is restricted to using dose buildup factors for a single material.

The program limitations include: a single source spectrum, one source volume with up to 30 subvolumes along each major axis or up to 500 point sources, 30 source energy groups, 30 materials, 100 compositions, 250 surface boundaries, 300 shield geometry regions, 15 boundaries per region, and one set of dose buildup factors. There is no limit on the number of detectors per problem. However, only 100 may be saved for stacked problems.

**7. TYPICAL RUNNING TIME**

On the IBM 3033, sample problem 1 took 8.13 seconds and sample problem 2 took 8.19 seconds. In both cases, the time is a total of the compilation, linkage, and go steps.

**8. COMPUTER HARDWARE REQUIREMENTS**

QADMOD-G is operable on the IBM 3033 and 3081 computers.

**9. COMPUTER SOFTWARE REQUIREMENTS**

A Fortran IV compiler is required. An Assembler language ORNL-written subroutine called TIME is part of the package. The user may choose to write a routine for TIME.

**10. REFERENCE**

J. H. Price and W. G. M. Blattner, "Utilization Instructions for QADMOD-G," RRA-N7914 (December 1979).

**11. CONTENTS OF CODE PACKAGE**

Included are the referenced document and one DS/DD 5.25-inch diskette (360 K) which contains the source codes and sample problem input plus output from the sample problems; total records 2972.

**12. DATE OF ABSTRACT**

February 1982; updated December 1983; February 1991.

**KEYWORDS: ** KERNEL; GAMMA-RAY; COMPLEX GEOMETRY