The purpose of this study is to verify the feasibility of applying GEANT4 (version 10.01) in neutron dose calculations in radiation protection by comparing the calculation results with MCNP5. The depth dose distributions are investigated in a homogeneous phantom, and the fluence-to-dose conversion coefficients are calculated for different organs in the Chinese hybrid male phantom for neutrons with energy ranging from 1 × 10(-9) to 10 MeV. By comparing the simulation results between GEANT4 and MCNP5, it is shown that using the high-precision (HP) neutron physics list, GEANT4 produces the closest simulation results to MCNP5. However, differences could be observed when the neutron energy is lower than 1 × 10(-6) MeV. Activating the thermal scattering with an S matrix correction in GEANT4 with HP and MCNP5 in thermal energy range can reduce the difference between these two codes.

Radioiodine thyroid ablation therapy is a common method for treatment of felines exhibiting hyperthyroidism. Due to the high gamma-ray emission rate of radioiodine (I), patients following treatment must be held in isolation for several days before release to prevent unnecessary dose to owners and members of the public. Dose rate measurement on the external surface of the patient of ≤ 20 μSv h is maintained as the patient release criterion without regard to residual activity. However, the Texas Department of State Health Services regulatory guide recommends a release limit of 3.7 MBq to households with non-pregnant women and children over the age of 18 y, and a limit of 925 kBq to households of pregnant women and children who can be supervised. In this paper, Monte Carlo computational radiation transport techniques are employed to predict and standardize the patient isolation time at the clinic by correlating the thyroid burden and surface dose rates of felines. Measurements of patient dose rate as a function of time are used to determine the patient-specific effective half-life experimentally and to validate the model results. Results show that an average holding time of 8 to 9 d is sufficient to reduce the residual activity to 3.7 MBq levels. Additionally, contact dose rate measurements of 20 μSv h or less correlate to residual activity levels of approximately 925 kBq. Based on the model and measurements, a protocol was developed for clinical use at Texas A&M University Veterinary Medical Teaching Hospital to allow estimation of residual activity following injection. This in turn confirms that the surface dose rates used as the release criteria follow the release limits recommended in the regulatory guide.

Accurate determination of the calibration constant is essential for the reliable determination of indoor radon air concentrations using alpha-track detectors. One possible source of error in the application of this method of radon assay is an effect of air density on the calibration factor. Such an effect, if present, could contribute to systematic errors in radon measurements where the calibration facility and the location measured were at different altitudes above sea level. To investigate this question, cellulose nitrate alpha-track detectors were exposed to known air concentrations of 222Rn over a range of air pressure in a systematic study of the effect of simulated altitude on the calibration constant (track density)/(integrated radon exposure). The values obtained for the calibration constant at known air-pressure values were used to establish correction factors as a function of equivalent altitude for this alpha-track method of radon assay. This correction may then be applied to compensate for the effect of altitude on radon-in-air determinations by this method. Altitude effects were evaluated for two detector configurations (the closed-can geometry and the open, or bare-detector geometry). The calibration constants (tracks cm-2) (kBq h m-3)-1 obtained exhibit an inverse relationship with air pressure (i.e., vary directly with altitude). The results indicate (as an example) that for an increase in altitude of approximately 1,000 m above sea level, the calibration constant for Kodak LR 115 II detectors increases by 28% for the closed-can geometry. For an altitude of 1,500 m above sea level, the calibration constant increases by 41% for closed detectors and by 63% for the open (bare) detectors.

Implementing a laser safety program within a University setting encompassing a wide variety of Class 3b and Class 4 lasers with varied potential uses introduces many challenges. Texas A&M University (TAMU) currently has over 310 laser units that are registered with the Texas Department of State Health Services (TDSHS). One primary task in maintaining the laser registration is to have a program that identifies the regulatory responsibilities of the registrant. The Radiological Safety Staff, a part of Environmental Health and Safety (EHS), administers the use of both ionizing and non-ionizing radiation. The Radiological Safety Officer (RSO)/Laser Safety Officer (LSO) maintains the laser registration. This article outlines key elements that were put forth in the development and implementation of the laser safety program at TAMU.

Coincident counts can be observed in experimental radiation spectroscopy. Accurate quantification of the radiation source requires the detection efficiency of the spectrometer, which is often experimentally determined. However, Monte Carlo analysis can be used to supplement experimental approaches to determine the detection efficiency a priori. The traditional Monte Carlo method overestimates the detection efficiency as a result of omitting coincident counts caused mainly by multiple cascade source particles. In this study, a novel "multi-primary coincident counting" algorithm was developed using the Geant4 Monte Carlo simulation toolkit. A high-purity Germanium detector for ⁶⁰Co gamma-ray spectroscopy problems was accurately modeled to validate the developed algorithm. The simulated pulse height spectrum agreed well qualitatively with the measured spectrum obtained using the high-purity Germanium detector. The developed algorithm can be extended to other applications, with a particular emphasis on challenging radiation fields, such as counting multiple types of coincident radiations released from nuclear fission or used nuclear fuel.