Gas-flow Proportional Counter Research Articles

Design and construction of a proportional gas flow meter with application in Mössbauer spectroscopy

The design, construction and operation parameters of a gas flow proportional counter are presented in order to implement the integral conversion electron mossbauer spectroscopy technique (ICEMS). The detector works with the support of a multi-channel detection system and a source of highenergy radiation of 57Co. A constant gas flow of a mixture of 5% CH4 in He was used as a multiplier gas, which increased the signal intensity, and protected the sample´s surface of electric shocks. An internal filter for low energy X-rays was considered during the design to achieve a lower background noise and optimize the volume of gas consumed. With this built-in ICEMS detector it is feasible to characterize efficiently the magnetic properties and oxidation states (hyperfine interactions) of both bulk materials and thin films. The calibration of the device was performed by using an iron sample synthesized by powder metallurgy. It was successfully identified the presence of a distinctive sextet of the α-Fe phase with a hyperfine field of 330 kOe and an isomer shift of 0.312 mm / s. The great usefulness of the equipment was verified by solving the magnetic hyperfine interactions of the Mossbauer spectrum associated to a commercial stainless-steel washer.

Natural Radioactivity in Groundwater in Phra Nakhon Si Ayutthaya Province

This research aims to study the specific activity of natural radioactivity in groundwater samples taken in the area of Phra Nakhon Si Ayutthaya Province, Thailand. Totally, sixty groundwater samples collected from wells in eight districts were monitored and determined for radionuclides 226Ra, 232Th and 40K and gross alpha and beta were determined using high resolution gamma spectrometer and Canberra Tennelec Series 5 gas flow proportional counter, respectively. Most of the sixty wells serve for water consumption and some other wells for agricultural. The results showed that the average activity concentrations of the gross alpha and beta were 0.01±0.007 and 0.15±0.02 Bq L-1 and the specific activity of 226Ra, 232Th and 40K were averagely 0.77±0.13, 1.03±0.19 and 15.56±1.28 Bq L-1, and respectively. The activity concentrations of the gross alpha and beta and the specific activity of the radionuclides in these samples exhibited quite low as compared to the recommended reference level for human consumption reported by World Health Organization (WHO).

English

Gross alpha and beta activity concentrations in soil, cassava and fluted pumpkin (leaf and stem) were investigated using a gas flow proportional counter. The gross alpha activity concentrations for the fluted pumpkin were between 3.55 and 13.95 Bq/Kg and 3.53 and 3.61 Bq/Kg for the leaves and stems, respectively. The gross alpha activity concentrations for cassava and soil samples ranged from 0.07 to 0.60 Bq/Kg and 0.35 to 0.53 Bq/Kg, respectively while the gross beta activity concentrations ranged from 0.43 to 0.89 Bq/Kg and 0.46 to 1.04 Bq/Kg for the cassava and soil samples, respectively. The gross alpha and beta activity concentrations in cassava, fluted pumpkin and soils samples have been determined using alpha/beta spectroscopy. The result of thestudy showed that the Iva-valley coal mine area has lower gross alpha and beta activity concentrations compared to other areas of the country. This shows that the coal mining activities in the area may not have increased the radiation burden of the area. Key words: Gross, alpha, beta, concentration, activity, food, crop.

Radiological hazard assessment of natural gross radioactivity in some cosmetic products

ABSTRACTMany kinds of cosmetic products were analyzed to determine gross radioactivity. In this study, gross alpha/beta radioactivity concentrations in 51 cosmetic samples were determined. The examined cosmetic products consist of blusher, eye shadow, lipstick, nail polish, shampoo, hand cream, cellulite cream, baby powder, soap, and toothpaste. The gross alpha–beta activity concentrations were measured with a nuclear spectroscopic system which contains gas-flow proportional counters. The highest gross alpha/beta activity concentrations were found in eye shadow samples of 1.621Bq g−1 for alpha and 6.471Bq g−1 for beta. The total effective doses due to gross radioactivity for skin were calculated. Although the effective dose of eye shadow samples had the highest value, the effective doses due to gross radioactivity concentrations in this study were found to be lower than the radiological limits given by the authorities.

A new life for the wavelength-dispersive X-ray spectrometer (WDS): incorporation of a silicon drift detector into the WDS for improved quantification and X-ray mapping

The wavelength-dispersive X-ray spectrometer (WDS) has been around for a long time and the design has not changed much since its original development. The electron microprobe operator using WDS has to be meticulous in monitoring items such as gas flow, gas purity, gas pressure, noise levels of baseline and window, gas flow proportional counter (GFPC) voltage levels, count rate suppression, anode wire contamination and other detector parameters.Recent development and improvements of silicon drift detectors (SDD’s) has allowed the incorporation of a SDD as the X-ray detector in place of the proportional counter (PC) and/or gas flow proportional counter (GFPC). This allows minimal mechanical alteration and no loss of movement range.The superiority of a WDS with a SDD, referred to as SD-WDS, is easily seen once in operation. The SD-WDS removes many artefacts including the worse of all high order diffraction, thus allowing more accurate analysis. The incorporation of the SDD has been found to improve the light and mid element range and consequently improving the detection limit for these elements. It is also possible to obtain much more reliable results at high count rates with almost no change in resolution, gain and zero-peak characteristics of the energy spectrum.

Rapid method to determine 89/90Sr in steel samples

The rapid measurement of 89/90Sr in steel samples is important in the event of a radiological emergency as well as for the characterization of routine nuclear decommissioning samples. A new method for the determination of radiostrontium in 1–2 g steel samples has been developed at the Savannah River Environmental Laboratory. The new method employs a rugged acid digestion that includes hydrofluoric acid, followed by a single preconcentration step to rapidly collect the radiostrontium and remove nearly all of the high iron content. A fusion step can be implemented after the steel dissolution when soil, concrete, or highly refractory particles are present. The 89Sr + 90Sr and/or 90Y are separated using extraction chromatographic resins and measured radiometrically, either by gas flow proportional counting or liquid scintillation counting. Several approaches for the measurement of 89Sr + 90Sr, 90Sr, and discrimination between 89Sr and 90Sr are discussed. This approach has a sample preparation time of 6–8 h for steel samples.

Incorporation of an Amptek Silicon Drift Detector into a Wavelength Dispersive Spectrometer (WDS) Replacing the Gas Flow Proportional Counter

Incorporation of an Amptek Silicon Drift Detector into a Wavelength Dispersive Spectrometer (WDS) Replacing the Gas Flow Proportional Counter

A study of gross alpha and beta measurements for thermal springs in Central Anatolia, Turkey

A screening of natural radioactivity content has been carried out in thermal water samples collected from surrounding of Central Anatolia, Turkey. The concentration levels of gross alpha and beta of 19 different samples has been determined using the low background gas-flow proportional counter. The measured gross alpha and beta activities in waters range from 0.11 to 16 Bq/L and 0.10 to 16.9 Bq/L, respectively. The measured values of gross alpha and beta concentrations are compared to previous studies in the literature and recommend WHO guideline activity concentration. The data resulting from the measurement have been statistically analyzed.

Activity Concentrations of <sup>137</sup>Cs and <sup>90</sup>Sr in Seawaters of East Sea, Korea

Background: This study was a long-term evaluation of 137Cs and 90Sr activity concentrations in seawater samples from the East Sea, Korea, in order to establish current activity levels. Results and long-term monitoring trends will be useful in the future monitoring of environmental radioactivity. Materials and Methods: Surface seawater samples were collected quarterly from Guryongpo and Jangho in the East Coast between 1998 and 2010 and the quarterly deep seawater samples were collected from three sites in the sea adjacent to Ulleung-do between 2012 and 2015. The activity concentrations of 137Cs were measured using a gamma-spectrometer. The activity concentrations of 90Sr and 90Y in a radioactive equilibrium state were measured using a gas flow proportional counter. Results and Discussion: We found the annual average activity concentrations of 137Cs in the surface seawater was 1.66-2.89 mBq∙kg-1 in Guryongpo and 1.68-2.43 mBq∙kg-1 in Jangho. The annual average activity concentrations of 90Sr in the surface seawater was 0.83- 1.98 mBq∙kg-1 in Guryongpo and 0.82-1.57 mBq∙kg-1 in Jangho. The annual average activity concentrations of 137Cs in the deep seawater sites were 1.51-1.73 mBq∙kg-1, 1.19-1.60 mBq∙kg-1 and 0.87-1.15 mBq∙kg-1 in TH, JD, and HP. The annual average activity concentrations of 90Sr in the same deep seawater sites were 1.00-1.94 mBq∙kg-1, 0.82-1.26 mBq∙kg-1, and 0.79-1.32 mBq∙kg-1. The effective half-life was calculated by analyzing change over time in the activity concentration in the surface seawater. The effective half-life of 137Cs was 15.3 ± 0.1 years in Guryongpo and 102 ± 3 years in Jangho. The effective half-life of 90Sr was 28.3 ± 4.3 years in Guryongpo and 16.6 ± 0.1 years in Jangho. The ratio of the average activity concentration (137Cs/90Sr) was 1.72 in the surface seawater, which is similar to the reported ratio of the global radioactive fallout. The ratio in the deep seawater was 1.24, which is somewhat low compared to the global ratio (1.6, 1.8). Conclusion: Activity concentrations of 137Cs and 90Sr in the seawaters of the East Sea were similar to the previously reported activity levels in the East Sea and northwestern Pacific as a result of global radioactive fallout following atmospheric nuclear weapon tests.

Calibration of a low background gas-flow proportional counter to estimate 234Th activity in coastal waters

This paper relates the calibration of a low background gas-flow proportional counter. This calibration has been used to determine low activity of 234Th in coastal water samples. Two methods were used to prepare calibration samples: Evaporation and Electrodeposition. First method was rejected due to the lack of reproducibility because the different geometry adopted by the drops of tracer once dried on the disk. On the contrary, through the second method, similar efficiencies were obtained in all detectors with an average of 0.401±0.004.In this paper, the whole procedure to obtain 234Th activity in dissolution as well as in particulate matter has been detailed, and all the algorithms needed to calculate activities and efficiencies are shown. Finally, two experiments have been designed in order to validate the calibration of the beta counter and the method to determine 234Th in coastal waters with high concentration of particulate matter.

Distributions of <sup>137</sup>Cs and <sup>90</sup>Sr in the Soil of Uljin, South Korea

Background: For the purpose of baseline data collection and enhancement of environmental monitoring the distribution studies of 137 Cs and 90 Sr in the soil of Uljin province was per- formed and the relation between surface soil activities and soil properties (pH, TOC and median of the surface soil) was analyzed. Materials and Methods: For 14 spots within 10 km from the NPP surface soil samples were collected and soils for depth profile were sampled for 3 spots in April 2011. Using γ-ray spectrometry with HPGe detector, the concentrations of 137 Cs were determined and the con- centrations of 90 Sr were measured by counting β-activity of 90 Y (in equilibrium with 90 Sr) in a gas flow proportional counter. Results and Discussion: The concentration ranges of 137 Cs and 90 Sr were <0.479-39.6 Bq· (kg-dry) -1 (avg. 7.51 Bq·(kg-dry) -1 ) and 0.209-1.85 Bq·(kg-dry) -1 (avg. 0.74 Bq·(kg-dry) -1 ) which were similar to the reported values from other regions in Korea. The activity ratio of 137 Cs to 90 Sr in surface soils was around 9.67, which is much bigger than the initial val- ue of 1.75 for worldwide fallouts because of faster downward movement of 90 Sr after fall- out than that of 137 Cs. For depth profile studies soils were collected down to 40 cm depth for the locations of Deokgu, Hujeong and Maehwa. The 137 Cs concentration distribution of the first two showed maximum values at top soils and decreased rapidly in exponential manner, while 90 Sr showed two local maximum values for soils near top and about 30 cm depth. Through linear fittings between the 137 Cs and 90 Sr concentrations of surface soil and pH, TOC and median of the surface soil, the only probable relationship obtained was be- tween 137 Cs and TOC (determination coefficient R 2 =0.6). Conclusion: The concentration ranges of 137 Cs and 90 Sr in Uljin were similar to the reported values from other regions in Korea. The only probable relationship obtained between activ- ities and soil properties was between 137 Cs and TOC.

Assessment of radiological risk parameters associated with some selected rivers around oil mineral producing sites in Abia state, Nigeria due to gross alpha and beta radiations

Context: The study of gross alpha and beta radiation in environmental components and water bodies in particular is very crucial to the environmental, radiation and medical Physicist as this helps to promote good water quality and environmental hygiene. Aim: This research work understudied the radiological risk parameters due to gross alpha and beta radiations associated with three selected rivers around crude oil production sites in Abia State, Nigeria. Materials and Methods: Gross alpha and beta activities were computed for the three rivers based on analytical measurements carried out using a well-calibrated IN-20 model gas-flow proportional counter. Radiological risk parameters were computed from the activity concentrations which included; annual effective dose equivalent of radiation from ingested water (AEDE), annual gonadal dose equivalent (AGDE), and excess lifetime cancer risk (ELCR). Results: The mean of the total AEDE due to the sum of alpha and beta radiations for the three rivers are 0.868 ± 0.221 mSv/y, 1.008 ± 0.156 mSv/y, and 0.917 ± 0.214 mSv/y; and are above the World Health Organization (WHO) permissible limit of 0.1 mSv/y. The mean of the total AGDE is 4.048 ± 1.063 mSv/y, 4.756 ± 0.739 mSv/y, and 4.295 ± 1.026 mSv/y; and are above the world average limit of 0.3 mSv/y. The mean of the total ELCR are (3.038 ± 0.774) × 10 −3 , (3.529 ± 0.547) × 10 −3 , and (3.210 ± 0.748) × 10 −3 , and are above the world average limit of 0.29 × 10 −3 . Conclusion: Most values of ELCR computed in this work are >6.0 × 10 −4 estimated to be the risk of fatal and weighted nonfatal health conditions over a lifetime (70 years) derived from the radiation dose of 0.1 mSv/y (WHO permissible limit for drinking water). Drinking water from these surveyed sources could impact negatively on the end users.

Standardization of 59Fe by 4π(PC)β–γ software coincidence system

The procedure for the standardization of 59Fe using a 4π(PC)β–γ software coincidence system is described. The standardization was performed with an experimental setup consisting of a thin window gas-flow proportional counter (PC) in 4π geometry coupled to a NaI(Tl) scintillator and to a HPGe detector. The data acquisition was carried out by means of a Software Coincidence System (SCS). The beta efficiency was changed by using Collodion films and aluminum foils as external absorbers.

Uncertainties in surface emission rate measurements

The uncertainties in surface emission rates determined by gas-flow proportional counters (multiwired) are broken down into alpha and beta emission rate determinations. Counting statistics, spectrum analysis, and electronic uncertainties are discussed with respect to the actual counting of the respective emission rate. The effects of source construction on the uncertainties are also examined.

Preliminary study on the radiological and physicochemical quality of the Umgeni Water catchments and drinking water sources in KwaZulu-Natal, South Africa

Raw and potable water sample sources, from the Umgeni Water catchment areas (rivers, dams, boreholes) in central KwaZulu-Natal (South Africa), were screened for Uranium concentration and alpha and beta radioactivity. Test methods used were gas flow proportional counting for alpha-beta radioactivity, and kinetic phosphorescence analysis (KPA), for Uranium. The uranium levels (median = 0.525 μg/L, range = <0.050–5.010) were well below the international World Health Organization (WHO) (2011) guideline for drinking-water quality (≤15 μg/L). The corresponding alpha and beta radioactivity was ≤0.5 Bq/L (median = 0.084, Interquartile Range (IR) = 0.038, range = 0.018–0.094), and ≤1.0 Bq/L (median = 0.114, IR = 0.096, range = 0.024–0.734), respectively, in compliance with the international WHO limits. For uranium radionuclide, the average dose level, at uranium level of ±0.525 μg/L, was 0.06 μSv/a, which complies with the WHO reference dose level for drinking water (<0.1 mSv/a). There was a distinct trend of cluster of relatively higher Uranium levels of some sources that were found to be associated with the geology/geography and groundwater sources. Overall, the radiological water quality classification, with respect to WHO, is “Blue” – ideal; additional physicochemical analyses indicated good water quality. The analytical test methods employed were found to be suitable for preliminary screening for potential radioactive “hot spots”. The observed Uranium levels, and the alpha/beta radioactivity, indicate contribution largely from Naturally Occurring Radioactive Material (NORM), with no significant health risk to humans, or to the environment.

Rapid determination of 90Sr in seawater samples

A rapid method for 90Sr in large seawater samples has been developed at the Savannah River National Laboratory (SRNL) to assay 90Sr at very low levels. The new method employs novel pre-concentration steps to collect 90Y quickly from up to 40 L of seawater to achieve a very low minimum detectable activity (MDA). An MDA for 90Sr of ~150 µBq L−1 may be obtained with this method using a 40 L seawater sample aliquot, counting 1,000 min with gas flow proportional counting. Following the pre-concentration of 90Y from the seawater, DGA Resin is used to rapidly separate 90Y from seawater samples and remove additional beta interferences. Gas flow proportional counting, liquid scintillation or Cerenkov counting may be used to count the purified 90Y and determine 90Sr present in the seawater sample. This new sample preparation method takes <8 h.

Application of alpha particle transport to the modelization of efficiency curves in proportional counters

The dependence of efficiency of a gas-flow proportional counter with respect to the source thickness and α-particle energy was evaluated using the code SRIM. Results for the mass-efficiency curves were evaluated for 209Po and 241Am in a substrate of NaNO3. The results revealed good agreement with a linear and a hyperbolic dependence for low and high thickness sources, respectively. However, some deviations were found for very thin thicknesses, which can be explained by taking into account scattering effects. A function is proposed for predicting the dependence of efficiency with α-particle energy in the range from 4 to 8 MeV.

Gross Alpha and Beta Activity Analyses in Urine—A Routine Laboratory Method for Internal Human Radioactivity Detection

The aim of this work was to develop a method to provide rapid results for humans with internal radioactive contamination. The authors hypothesized that valuable information could be obtained from gas proportional counter techniques by screening urine samples from potentially exposed individuals rapidly. Recommended gross alpha and beta activity screening methods generally employ gas proportional counting techniques. Based on International Standards Organization (ISO) methods, improvements were made in the evaporation process to develop a method to provide rapid results, adequate sensitivity, and minimum sample preparation and operator intervention for humans with internal radioactive contamination. The method described by an American National Standards Institute publication was used to calibrate the gas proportional counter, and urine samples from patients with or without radionuclide treatment were measured to validate the method. By improving the evaporation process, the time required to perform the assay was reduced dramatically. Compared with the reference data, the results of the validation samples were very satisfactory with respect to gross-alpha and gross-beta activities. The gas flow proportional counting method described here has the potential for radioactivity monitoring in the body. This method was easy, efficient, and fast, and its application is of great utility in determining whether a sample should be analyzed by a more complicated method, for example radiochemical and/or γ-spectroscopy. In the future, it may be used commonly in medical examination and nuclear emergency treatment.Health Phys. 106(5):000-000; 2014.

Long-term measurements of 36Cl to investigate potential solar influence on the decay rate

Recently, Jenkins et al. [6] reported on fluctuations in the detected decay events of 36Cl which were measured with a Geiger–Müller counter. Experimental data of 32Si measured by means of an end-window gas-flow proportional counter at the Brookhaven National Laboratory show similar periodicity, albeit a different amplitude. Jenkins et al. interpret the fluctuations as evidence of solar influence on the decay rates of beta-decaying radionuclides.In this work, liquid scintillation counting was used to check for potential variations in the 36Cl decay rates. A custom-built counter with three photomultiplier tubes was used. In contrast to commercial counters, the relevant parameters of our system are well controlled and the discrimination threshold and HV setting can be adjusted and checked. The experimental data were analyzed by means of the triple-to-double coincidence ratio (TDCR) method which is a primary method for activity determination. Thus, our results do not depend on any other standard or reference source.Our data show fluctuations which are by more than one order of magnitude lower than those seen in the experiment using a Geiger–Müller counter. More importantly, no oscillation could be identified. Interestingly, our data overlap in time with those from Jenkins et al. [6]. We do not observe the phase and amplitude as seen by Jenkins and conclude that the fluctuations are not due to solar influence. This also implies that the interpretation by Jenkins et al. is false.

Determination of gamma-ray emission probabilities per decay of Ga-68

The measurement of the gamma-ray emission probabilities per decay of 1077keV of 68Ga is presented. The standardization system consists of a gas-flow proportional counter in 4π geometry coupled to an HPGe detector for the gamma-ray detection. The gamma-ray emission probabilities per decay were measured in an HPGe gamma-ray spectrometer. The weaker gamma-ray intensities of 68Ga were measured in a relative way, making use of an uncalibrated ampoule of 68Ge–68Ga in radioactive equilibrium, and considering the absolute result from the 1077keV gamma-ray.