We performed theoretical research on radon escape effect on activity of its progenies in 232Th, 228Ra, 238U, and 226Ra decay series. Based on the research results, we predicted that radon escape does not affect activity of its progenies in 232Th and 228Ra series. However, radon escape does affect the activity of its progenies, except for 210Pb, 210Bi and 210Po, in 238U and 226Ra decay series. The theoretical research was based on the Bateman equation. Correspondingly, we conducted experiments to validate the results obtained from the theoretical research on 232Th, 228Ra, and 226Ra decay series. Experiments on radon escape effect on its progenies in 238U series were not conducted due to unavailability of adequate 238U samples. Data obtained from the experiments validated the theoretical predictions for 232Th, 228Ra, and 226Ra series. The information obtained from the study could be useful for an effective NORM waste treatment. Findings of the study may provide a foundation for applying gamma-ray spectrometry to accurately determine the activity of those decay series.

ABSTRACT:After some consumer products indicated elevated levels of 232 Th progeny by gamma-ray spectrometry, a microwave digestion and inductively coupled plasma-mass spectrometry (ICP-MS) procedure was implemented for the direct assay of 232 Th content to ensure compliance with Federal regulations and guidelines. Levels of 232 Th were determined by ICP-MS based on standard calibration using a 205 Tl internal standard. The method had a method detection limit (MDL) of 0.15 Bq g -1 and a lower limit of quantification (LLOQ) of 0.65 Bq g -1 for 232 Th, making it a suitable confirmatory method following gamma-ray spectrometry. The 232 Th activity concentration calculated from the ICP-MS results ranged from 2.0-3.4 Bq g -1 for the kinesiology tape samples and 20 Bq g -1 for the silicone ion bracelet. The VARSKIN+1.0 software program was used to calculate the shallow dose equivalent of ionizing radiation from 232 Th and its progeny from the ICP-MS results. The skin dose to the consumer wearing the kinesiology tape ranged from 0.48-1.6 mSv y -1 . The skin dose to the consumer with constant wear of the silicone ion bracelet was estimated to be 17 mSv y -1 . Although 232 Th may be determined indirectly by assay of high abundance gamma rays produced by its progeny, the US Code of Federal Regulations (CFR) requires the direct assay of 232 Th for confirmatory analysis. We found this ICP-MS method to be a rapid 232 Th confirmatory technique compared to a chemical separation followed by alpha spectrometry procedure.

A method for determining activity of 89Sr and 90Sr in a sample where 90Sr and 90Y are not in equilibrium is presented. The method consists of an experimental design and equations for accurately calculating activity of 89Sr and 90Sr based on 90Y β particle counts and the total counts of β particles emitted from 89Sr, 90Sr, and 90Y in a sample. The equations are derived based on chemical separation sequences, β particle counting sequences, and the Bateman equation. The presented method allows simultaneously obtaining the activity of 89Sr and 90Sr in a non-equilibrated 90Sr/90Y system without the need of Cerenkov counting.

A method for determining activity of 89 Sr and 90 Sr in a sample where 90 Sr and 90 Y are not in equilibrium is presented. The method consists of an experimental design and equations for accurately calculating activity of 89 Sr and 90 Sr based on 90 Y β particle counts and the total counts of β particles emitted from 89 Sr, 90 Sr, and 90 Y in a sample. The equations are derived based on chemical separation sequences, β particle counting sequences, and the Bateman equation. The presented method allows simultaneously obtaining the activity of 89 Sr and 90 Sr in a non-equilibrated 90 Sr/ 90 Y system without the need of Cerenkov counting.

A rapid analytical method for quantifying 90Sr in infant formula prior to secular equilibrium is presented. The approach is dependent on the use of two separations of 90Sr from 90Y, with the first providing an 90Y ingrowth start point and the second providing an 90Y ingrowth end point. Data were obtained at activity concentrations of approximately 6 Bq/kg and 160 Bq/kg, the latter of which is representative of the US Food and Drug Administration (FDA) Derived Intervention Levels (DIL). Experiments were designed to collect data from ingrowth periods ranging from 16 h to 2 weeks. Activities obtained with a separation interval as low as 16 h ranged from 92.7 to 109.4% of the known value. When 90Y ingrowth was allowed to occur for 24 h or longer, the activities ranged from 93.2 to 106.2% of the known value and the precision of this group improved from 5.2 to 3.1%. The limit of quantification (LOQ) was 0.5 Bq/kg using 250 g sample portions.

Based on the original work of Rutherford (Radio-activity, 1905) and Bateman (Proc Camb Philos Soc 15:423–427, 1910), the authors designed two schemes consisting of explicit equations as simple methods for accurately obtaining activity of 90Sr and 90Y before they reach secular equilibrium. Application of the methods to the 90Sr/90Y system where 90Sr and 90Y are not in equilibrium will substantially reduce the time needed for determining activity of 90Sr because neither sequential measurements of 90Sr or 90Y (up to about 2 weeks) nor waiting for 90Sr and 90Y to reach equilibrium (more than 3 weeks) will be needed. We also implemented the explicit equations for decay/ingrowth correction of progeny’s activity and applied them to the 95Zr/95Nb system. Using the equations, the authors corrected activity concentrations of 95Nb to a designated reference time from the activity concentrations measured from samples at different times, for instance, 2, 8, 15, and 29 days after a reference time. During those measurement times, 95Nb and 95Zr were not in equilibrium. The corrected 95Nb activity concentrations were within an accuracy of − 10%.

Cerium bromide (CeBr3) scintillators are useful room temperature gamma-ray detectors that provide the robustness of a scintillator with improved resolution over traditional sodium iodide (NaI) detectors. This makes them attractive for field deployment or emergency response operations especially when combined with the power of Monte-Carlo based efficiency determinations. This work documents the characterization of CeBr3 detectors and the efficiency determination of a portable CeBr3 detector based gamma-ray detection system for food measurements.

A portable CeBr3 based gamma-ray detection system was designed and built for rapid turnaround, high throughput, real-time, and in situ sample analysis. The new technique allows automated data transmission from the field unit to a central laboratory controller to ensure laboratory quality of the data collected by field users without gamma-ray spectroscopy expertise. The method validation data indicates that the system's data quality objectives are adequate for radiological or nuclear emergency response or targeted surveillance programs where gamma-ray analysis is needed.

Measurement capability and data comparability are essential for emergency response when analytical data from cooperative laboratories are used for risk assessment and post incident decision making. In this study, the current capability of food emergency response laboratories for the analysis of 210 Po in water was evaluated using a proficiency test scheme in compliance with ISO-43 and ILAC G13 guidelines, which comprises a test sample preparation and verification protocol and an insightful statistical data evaluation. The results of performance evaluations on relative bias, value trueness, precision, false positive detection, minimum detection limit, and limit of quantification, are presented.