C.M. Ryan, C.M. Marianno, W.S. Charlton, A.A. Solodov, and R.J. Livesay,
"Determining the Effect of Concrete Roadways on Gamma-ray Background for Radiation Portal Monitoring Systems,"
33rd ESARDA Annual Meeting: Symposium on Safeguards and Nuclear Material Management
, May 16–20, 2011, Budapest, Hungary.
The dissolution of the Soviet Union coupled with the growing
sophistication of international terror organizations has brought
about a desire to ensure that a sound infrastructure exists to
interdict smuggled nuclear material prior to it leaving its country
of origin. To combat the threat of nuclear trafficking, radiation
portal monitors (RPMs) are deployed around the world to intercept
illicit material while in transit by passively detecting gamma and
neutron radiation. Portal monitors in some locations have reported
abnormally high background counts with little or no consistency.
The higher background data has been attributed, in part, to the
concrete surrounding the portal monitors. Higher background
increases the minimum detectable activity and can ultimately lead
to more material passing through the RPMs undetected.
This work was focused on understanding the influence of the
concrete surrounding the monitors on the total gamma-ray background
for the system. The study combined destructive and nondestructive
analytical techniques with computer simulations to form a
qantitative model that is adaptible to any RPM configuration. Six
samples were taken from three different composition concrete slabs.
The natural radiological background of these samples was determined
using a high-purity germanium (HPGe) detector in conjunction with
the Canberra In-Situ Object Counting System (ISOCS™) and Genie™
2000 software packages. The composition of each sample was
determined using neutron activation analysis (NAA) techniques. The
results from these experiments were incorporated into a Monte Carlo
N-Particle (MNCP) photon transport simulation to determine the
number of gamma-rays from the different concrete slabs detected by
Associated Project(s):Measurement and Modeling of Shielding and Attenuation Effects on Radiation Portal MonitorsSHIELD (Smuggled HEU Interdiction through Enhanced anaLysis and Detection): A Framework for Developing Novel Detection Systems Focused on Interdicting Shielded HEU