I. Tsorxe, “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 and in situ-measurements 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 and in-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.