"Baseline Measurements of Natural Radioactivity at the Texas A&M Engineering Extension Service- Disaster City,"
M.S. Thesis, Health Physics, Texas A&M University, College Station, TX (2017).
"Disaster City" is a 52-acre mock city that serves as a training
facility for emergency responders. Emergency responders from
distant locations come to Disaster City (DC) for search and rescue
training and exercises. The facility has also been used by Texas
A&M's Nuclear Security Science & Policy Institute (NSSPI)
for several radiological emergency training activities.
Periodically, sealed radioactive sources are used at DC to train
emergency responders and students to become more familiar with
radiation dose rates and field detection equipment. One of the
radiological emergency training exercises that is being considered
currently is to prepare for potential short-lived radiological
contamination using unsealed radioactive sources. Contamination
control and monitoring are important elements of using unsealed
radioactive sources in the environment. It is paramount, therefore,
to document the present environmental conditions of the DC site in
order to help scientists assess future effects caused by human
activities. The measurement of naturally occurring radiation to
establish baseline levels is a normal part of security and
emergency preparedness. As a result, this research involved the
conduct of a preliminary survey of gamma radiation background from
terrestrial sources at the DC site to provide a baseline for the
site prior to the startup of radiological contamination. This
research involved a ground based radiation survey using a 4"x4"x16"
thallium-doped sodium iodide (NaI (Tl)) ORTEC search system (ORTEC
NaI-SS). In addition, soil samples, water samples andin
situmeasurements were analyzed using a high-purity germanium (HPGe)
detector. Aliquot water samples were counted using liquid
scintillation counter (LSC).
All data collected were reviewed to identify any radiological
anomalies. The ORTEC NaI-SS measured count rates that ranged from
656 to 2321 s-1. The highest average count rate of 1625±63.2 s-1
was observed in the "Rubble Pile 2 area." Second by second spectral
data was summed in areas of where the count rates exceeded 1564 s-1
to attempt to identify the reason for the higher count rates. The
analysis showed only increased levels of 40K and 232Th. Similarly,
collected laboratory samples andin-situHPGe spectra were reviewed.
This review showed specific radionuclides in the 238U chain, 232Th
chain, and 40K. For the LSC analysis of water samples, the results
indicate no detectable radioactivity. In summary, the results
of this project indicated the presence of only natural background
and no-man-made radiation sources were discovered.