We have developed accessible methods to demonstrate fundamental statistics in several phenomena, in the context of teaching electronic signal processing in a physics-based college-level curriculum. A relationship between the exponential time-interval distribution and Poisson counting distribution for a Markov process with constant rate is derived in a novel way and demonstrated using nuclear counting. Negative binomial statistics is demonstrated as a model for overdispersion and justified by the effect of electronic noise in nuclear counting. The statistics of digital packets on a computer network are shown to be compatible with the fractal-point stochastic process leading to a power-law as well as generalized inverse Gaussian density distributions of time intervals between packets.

A comprehensive study of the efficiency calibration and calibration verification of Ge gamma-ray spectrometers was performed using semi-empirical, computational Monte-Carlo (MC), and transfer methods. The aim of this study was to evaluate the accuracy of the quantification of gamma-emitting radionuclides in complex matrices normally encountered in environmental and food samples. A wide range of gamma energies from 59.5 to 1836.0keV and geometries from a 10-mL jar to 1.4-L Marinelli beaker were studied on four Ge spectrometers with the relative efficiencies between 102% and 140%. Density and coincidence summing corrections were applied. Innovative techniques were developed for the preparation of artificial complex matrices from materials such as acidified water, polystyrene, ethanol, sugar, and sand, resulting in the densities ranging from 0.3655 to 2.164gcm−3. They were spiked with gamma activity traceable to international standards and used for calibration verifications. A quantitative method of tuning MC calculations to experiment was developed based on a multidimensional chi-square paraboloid.

The results are described of an upgrade of the low-background gamma-ray spectrometry laboratory at New York State Department of Health by acquiring sensitivity to low-energy gamma rays. Tuning of the spectrometer and its low-energy response characteristics are described. The spectrometer has been applied to monitor the environment by measuring aerosols and water in New York State contaminated by the 2011 Fukushima accident plume. In addition, the spectrometer has been used to monitor radioactivity in food by performing a study of cesium in Florida milk.

An air-sampling network that operates continuously as part of New York State’s environmental surveillance program collected radionuclides emitted as a result of the Fukushima nuclear accident. Samples were collected, typically for 7 days each, by drawing ~600 m3 of air through a particulate-collecting filter followed in series by a canister containing activated charcoal. Additional air sampling was implemented at ~3-day intervals at two locations. Gamma-ray spectroscopy was used to confirm the detection of 131I, 137Cs, 134Cs, and 7Be in the particulate phase at all sites, with maximum concentrations near 1,260, 160, 160, and 5,200 μBq/m3, respectively. Gas-phase 131I, collected on activated charcoal, exhibited a maximum concentration of 3,400 μBq/m3 at the sites. Assessment of radionuclide levels in the air samples suggests that there were minimal health impacts from the airborne radionuclides as the activities contributed an insignificant amount to the annual human dose.

A low-background γ-ray spectrometer for environmental surveillance, emergency response, and environmental health research has been constructed. It consists of a 132% efficient HPGe detector, graded lead shielding, and muon-rejection shielding, as well as external steel and building shielding. Detailed operation of the γ spectrometer and all of its components is described. Cosmic-ray muon and cosmic–neutron-induced background was accurately measured, and is discussed. We have achieved an overall background reduction by a factor of 9436 relative to the ambient level. Our integrated background rate in the γ energy range of 50–2700keV was measured as 2.3 counts per min, corresponding to 15countsks−1kg−1 Ge. Future directions in low-background γ spectroscopy at our facility are described.

In counting of radioactivity, using for example gas proportional (GP) or liquid scintillation (LS) counters, one can set up two or more electronic windows, which can measure two or more radiation components. In this work, we derived general equations for n-window counting in matrix notation, including mutual crosstalk between the windows using both the ratio (not normalized) and the fraction (normalized) methods. A solution for n radiation components is presented. For the two-window measurements, we report complete statistical analysis of the results including propagation of all uncertainties. The decision-level and the detection-limit equations were derived including crosstalk correction, uncertainties of the variables, Gaussian continuity correction, interference correction, and the overdispersion correction. Numerical verifications of the two-window systems are presented, including conditions for the detection of a minor component in the presence of a major component. In addition, limited experimental verifications of the two-window systems using LS counting are reported.

The manufacture of carbon nanotubes (CNTs) relies on the use of transition metal catalysts. The presence of metals in CNTs has been shown to critically affect the physical, chemical and surface properties of the material for applications in areas such as gas sensors and microcolumns. Once CNTs are released into the environment, the bioavailability of the metals is of concern, in the context of potential human toxicity. In the present study, methods were developed to determine the metals' concentrations in single-walled and multiwalled CNTs (SWCNT and MWCNT, respectively). The metals' concentrations in the SWCNT and MWCNT were determined by inductively coupled plasma optical emission spectrometry (ICPOES) and mass spectrometry (ICPMS), after the CNTs had been pretreated with one of the three extraction/digestion methods: water extraction, dilute acid (1% HNO(3)) extraction, and microwave acid digestion. The total metal concentrations were determined by instrumental neutron activation analysis (INAA). The metals in CNTs were found to have poor solubility in water and dilute acid, suggesting that the role of CNT metals in cytotoxicity may be limited due to their limited bioavailability, and that metals encapsulated in the CNTs could have potential use as tracers for CNTs, in biological or toxicological studies. Microwave acid digestion can achieve a near-complete extraction of metals from the CNTs, and thus is a suitable cleaning method, when high-purity CNTs are desired. Microwave acid digestion followed by ICPOES analysis produced results closer to those obtained by INAA than to those obtained by ICPMS; the latter method was subject to nonspectral interference induced by carbon residues in the sample solution.

Several older and recent reports provided evidence for the oscillatory character of the exponential decay law in radioactive decay and attempted to explain it with basic physics. We show here that the measured effects observed in some of the cases, namely in the decay of 226Ra, 32Si in equilibrium, and 36Cl, can be explained with the temperature variations.

Nondestructive gamma-ray and neutron techniques were used to characterize the irradiation exposures of irradiated fuel assemblies. Techniques for the rapid measurement of the axial-activity profiles of fuel assemblies have been developed using ion chambers and Be(..gamma..,n) detectors. Detailed measurements using high-resolution gamma-ray spectrometry and passive neutron techniques were correlated with operator-declared values of cooling times and burnup.