XOQGAM - Version 1.0 Methodology and Software Routines
for Computation of

Gamma Radiation Exposures from Finite-cloud Gaussian Plumes.

**2. CONTRIBUTORS**

John N. Hamawi,
Entech Engineering.

* *FORTRAN 90/95; Linux, MacOS, and Windows (C00847MNYCP00)

XOQGAM is used to
calculate dose rates from radioactive Gaussian plumes of finite dimensions at
offsite receptors through use of the so-called gamma atmospheric dispersion
factor, referred to as the “gamma (χ/Q)”. Models and software routines are
presented for three dispersion models:
(a) the plume centerline model, where the plume is represented as a
straight-line airflow, (b) the sector average model, where the plume is assumed
to meander over time and spread uniformly within a cardinal sector, and (c) the
stationary puff model, which is applicable to intermediate steps in a
variable-trajectory plume dispersion model. The software routines documented in
the report are meant for incorporation (by interested parties) into other
software that make use of the semi-infinite cloud models and multi-year
meteorological data. As such, plume
dimensions, plume elevation, wind speed and receptor distance, as well as the
gamma radiation emitted by the plume (assumed to be monoenergetic in XOQGAM),
are provided as input to the routines, and are evaluated one case at a time. Validation
is provided for all three gamma (χ/Q) models, primarily through
comparative analyses; one set of such comparisons is between the dose rates
from a line source, a disk source, and a point source based on the gamma
(χ/Q) vs. corresponding results by a radiation shielding code.

The U.S. Nuclear Regulatory Commission’s (NRC) Advanced Notice of Proposed Rulemaking (ANPR) in) in 2015 specifically recommended that the dose conversion factors (DCFs) in Regulatory Guide (RG) 1.109 be revised as part of any effort to more closely align the NRC's regulations with International Commission on Radiation Protection (ICRP) recommendations in publication ICRP-103. Section C.2 of RG 1.109 provides a sector-average finite-cloud model for computation of annual doses at offsite receptors from noble gas releases from free-standing tall stacks. One of the limitations of this model is that embedded in the applicable equation is the dose conversion factor (DCF), and as such the model is not suitable for implementation of the ANPR (when or if approved) and of the recommended use of stand-alone updated DCFs. This limitation can be circumvented through use of the gamma (χ/Q). This has been described in Nuclear Technology (Hamawi, The Gamma Atmospheric Dispersion Factor for Finite-Cloud Radiation Dose Computations, Volume 195, pgs. 363-370, Sep. 2016) and has been implemented in XOQGAM.

The XOQGAM computer
code implements the gamma (χ/Q) analytical models for estimating dose
rates from radioactive Gaussian plumes of finite dimensions. The method of
solution involves the numerical integration of complex three-dimensional
integrals representing the spatial distribution of the radioactivity in the
plume and the transmission of radiation through air.

None noted.

**7.** **TYPICAL RUNNING
TIME**

Running
time on a single processor is directly related to problem size and host system,
ranging from a few seconds to a few minutes.

**8. COMPUTER HARDWARE REQUIREMENTS**

On many architectures, stack size limits must
be large enough to allow the placement of temporary arrays on the stack.

In addition to compilers, program building
requires Linux and MacOS systems require an up-to-date version of make. A
modern Fortran compiler is required to compile from source.

J. N. Hamawi, The Gamma Atmospheric Dispersion Factor for Finite-Cloud Radiation Dose Computations; Entech Engineering, Westborough, MA; Nuclear Technology, Volume 195, pgs. 363-370 (September 2016).

**11. CONTENTS OF CODE PACKAGE**

The entire software package, XOQGAM, is written in FORTRAN-775 and
consists of a

main program, 8 subroutines and a Block Data routine, for a total of about 800 coded lines.

July 2020

** KEYWORDS: **gamma (χ/Q) analytical models; atmospheric dispersion, radiation
exposure.