Minimum Detectable Activity Values Research Articles

Characterization of a CZT-based spectrometer for underwater operation via simulations and experiments

The harsh environmental conditions in the marine environment pose variousconstraints on developing efficient instruments to carry out long-term, in situradioactivity measurements. In addition, the strong attenuation of γ-raysin the water medium, makes remote sensing of such radiation a challenging task.In the present work, we report on the efforts to find the optimal characteristicsand deployment scenarios of a new prototype γ-ray instrument based on asmall-size CZT crystal enclosed in seal-tight housing to be deployed for operationin large depths. Lab experiments and detailed Monte Carlo simulations were combinedto validate the actual crystal dimensions, determine its efficiency and energyresolution, as well as establish the minimum detectable activity values of theinstrument in different configurations and scenarios.

A baseline estimation procedure to improve MDA evaluation in gamma-ray spectrometry

The evaluation of minimum detectable activity (MDA) for a radionuclide in a gamma-ray spectrum is generally carried out through the computation of a suitable background count. This task is sometimes difficult for complex spectra for the presence of many photopeaks which make the trend of continuum extremely variable due to multiple dispersion effects and interference factors. It follows that the MDA assessment must be take into account the contributions of all gamma emissions of radionuclides contained in a sample and its value can be significantly higher than that determined by considering only the background of the spectrometric system due to the overlapping of other peaks. A procedure or an algorithm to determine, each time, the count values to be used for the calculation of MDA is interesting and useful. In this work, some of the more recent algorithms proposed for background subtraction in a gamma-ray spectrum have been examined, applying them in an inverse way for the evaluation of baseline trend in the whole energy range. Among the algorithms examined, particular attention was paid to the application of SNIP (statistical sensitive nonlinear iterative peak clipping) algorithms, which are the simplest to adopt and implement in an application procedure. The results obtained in the analysis of test gamma-ray spectra are satisfactory and allow to quickly determine the MDA values with a formulation based on the ISO-11929 standard.

An Advanced Optimization Method to Minimize the Detection Limit of Liquid Scintillation Counter to Measure Low-Level Tritium Activity in Groundwater

In arid regions, the tritium concentration in groundwater is typically very low and often falls below the minimum detectable activity (MDA) of the conventional liquid scintillation counter (LSC). Therefore, to measure the tritium activity concentration, it is necessary to lower the detection limit so that the scintillation counter can detect it. In the present study, several methods are discussed which are effective at lowering the detectable activity of tritium. One of these methods is to enrich the tritium activity concentration by ten- to fortyfold of the initial concentration of the tritium. Twelve spiked samples with known amounts of tritium, five with high concentrations and seven with low concentrations, were enriched by the electrolysis process. The results indicated that enriching the tritium levels in groundwater lowers the MDA value. Other methods are minimizing background radiation using low-background materials for sample containers, increasing the measurement efficiency of the scintillation counter and counting time, and shielding the sample from environmental radiation using the shutter option in LSC. Moreover, reducing the number of interfering contaminants in the sample can lower the uncertainty in measuring the tritium concentration in the water sample, which is beneficial for detecting low-level tritium in water to ensure public health and safety.

Gamma Radioactivity Detection Limits and Associated Radionuclide Intakes Study in Artificial Human Urine Using Sodium-iodide and High-purity Germanium Detectors.

The performance of several gamma detectors was investigated for emergency urine bioassay screening of two radionuclides of concern: 131 I and 137 Cs. Unspiked artificial urine samples were measured for 10 min each on four different gamma detectors: 80% relative efficiency high-purity Ge detector in standard shielding, 102% low-background high-purity Ge detector equipped with top muon shield, 78% high-purity Ge well detector in standard shielding, and 4″ × 4″ NaI well detector in standard shielding. The measured gamma spectra were analyzed in two ways: (1) for the 364-keV peak region of 131 I and 662-keV peak region of 137 Cs and (2) for the total counts in the full energy spectrum (50-2,048 keV). The results were analyzed using the principles of signal detection theory according to the Currie's formalism extended by a complete uncertainty propagation. This enabled calculation of the detection capability in terms of detection limit (Bq L -1 ) of urine, the latter referred to as minimum detectable activity. The NaI well detector had the lowest minimum detectable activities for total spectra, whereas the high-purity Ge well detector had the lowest peak minimum detectable activity values. Minimum detectable inhalation and ingestion intakes from urine bioassay were calculated from the minimum detectable activity values for urine collection 1 d, 1 wk, and 1 mo past the initial intake. The calculated intakes were compared with annual limits on intake. The results are interpreted with respect to a large-scale radiological emergency response.

Optimisation of CO2 absorption and liquid scintillation counting method for carbon-14 specific activity measurement in atmospheric air

A method for the determination of 14C activity in the ambient air was optimised with the development of a simple setup for the regeneration of CO2 from carbonate sample and saturating the absorber in <45 min for direct determination of activity by liquid scintillation counting (LSC). Atmospheric CO2 was trapped in NaOH solution and precipitated as BaCO3 by adding BaCl2. The carbonate sample was taken in a newly designed regeneration system, subjected to acid hydrolysis, and the absorber (CarboSorb-E) was saturated with the CO2 regenerated from carbonate sample. This allowed optimisation of CO2 absorption by the absorber (up to ~ 2.3941 g of CO2/10 mL with an average of 2.1688 g) and a minimum detectable activity value of 14 Bq kg−1C for a counting time of 300 min (8 Bq kg−1C for 1000 min) was achieved with Quantulus - 1220 LSC system. The necessity of (i) the measurement of the total volume of air sampled, (ii) the determination of trapping efficiency for CO2 in the NaOH, recovery of 14C in chemical processing of BaCO3, and subsequent regeneration and absorption processes, and (iii) independent determination of carbon content in the air for expressing the results in terms of 14C specific activity (Bq kg−1C), are avoided in this method. The method is capable of yielding accurate results, in a considerably shorter time when compared to previously reported methods, with a deviation of <2.2% from the target value (with a relative standard deviation of 1.1%, and a relative error of 0.53%) when ambient air samples from clean air region (region not affected by local anthropogenic sources of 14C) are analysed. Validation of the method was performed by (i) analysing BaCO3 sample derived from ambient air by accelerator mass spectrometry, and (ii) analysing the CO2 produced from the combustion of IAEA C3 reference material. Upon validation, the suitability of the method for determining small excess 14C specific activity in the vicinity of a nuclear power plant was demonstrated.

Tritium concentrations and consequent doses in bottled natural and mineral waters sold in Turkey and Azerbaijan

In this study, tritium levels in commercially sold bottled natural and mineral waters in Turkey and Azerbaijan were determined. Tritium measurements were performed using Liquid Scintillation Counter (PerkinElmer TriCarb 2910 TR). 16 natural and 11 mineral samples from Turkey and 7 natural and 8 mineral samples from Azerbaijan, for a total of 42 commercially sold water samples were analyzed. The Minimum Detectable Activity (MDA) value for the method used was found as 1.69 Bq L−1. In total, 7 of the natural water samples and 8 of the mineral water samples were found to be below the MDA value. The average activity concentrations in natural and mineral water samples were found as 2.23 ± 0.90 Bq L−1 and 2.51 ± 0.90 Bq L−1 for Turkey and 2.69 ± 0.91 Bq L−1 and 2.43 ± 0.89 Bq L−1 for Azerbaijan, respectively. In addition, annual effective dose rates and lifetime cancer risk values for the water samples were calculated. These radiological parameters were compared with the values recommended by international organizations. The results demonstrated that consumption by humans of the studied waters would not constitute any health risks in terms of tritium.

Optimisation of a batch thermal combustion method using a tube furnace oxidation system (pyrolyser) and LSC for carbon-14 determination in environmental matrices

Accelerator mass spectrometry and benzene synthesis coupled with liquid scintillation spectrometry are often used for accurate measurements of 14C activity in the environmental matrices. Thermal oxidation is one of the methods employed for 14C determination in environmental matrices. In this method, the sample is oxidised at high temperature (600–900 °C) to convert carbon species to CO2 and trapped in an amine-based absorber for determining the activity in a liquid scintillation counting (LSC) system. In this study, the performance of a commercially available tube furnace system (pyrolyser), for batch combustion of samples, was evaluated for the determination of 14C specific activity in terrestrial biota samples. Significant improvements over the manufacturer specified method, which is primarily designed for analysis of samples with activity well above the environmental background level, was implemented to achieve accurate determination of 14C specific activity at ambient background level. In the improved method, the CO2 produced from the combustion of the sample was isolated from the combustion products through cryogenic trapping and then absorbed in the absorber (Carbo-Sorb E) through a simple off-line transfer process. This allowed (i) optimisation of CO2 absorption by the absorber (2.2477 g of CO2/10 mL), (ii) achieving good accuracy and precision in the measurements, and a minimum detectable activity value of 13 Bq kg−1C for a counting time of 300 min (7 Bq kg−1C for 1000 min), (iii) avoiding uncertainty associated with the determination of recovery of 14C in the combustion and trapping process, and (iv) elimination of the need for an independent determination of carbon content (%) for expressing the results in terms of 14C specific activity. The method is capable of yielding accurate results with a deviation of <2.4% from the target value for IAEA C3 quality assurance reference material (with a relative standard deviation of 1.40%, and relative error of 0.34%). The combined uncertainty (1σ) associated with the measurements was computed to be 3.4%. Upon optimisation, the suitability of the method for the determination of 14C specific activity in typical terrestrial biota samples of clean air region (region not affected by local anthropogenic sources) and for the quantification of a small increase in the 14C activity above ambient levels in the vicinity of a nuclear power plant is demonstrated.

Monitoring the Radioactive Contamination in Imported Processed Food items

A total of 138 samples corresponding to 24 different types of imported processed food items, distributed between January and November 2019, were collected in order to test their radioactive contamination levels. The radioactivity of 131I, 134Cs, and 137Cs was measured via gamma spectrometry using an HPGe detector. Radiation levels of 131I and 134Cs higher than the minimum detectable activity value were not detected in any of the samples. However, in 20 samples, radiation levels of 137Cs, ranging between 0.86 and 79.28 Bq/kg, were detected. The food items tested included cashew nuts, hazelnuts, noni juice, Neungi mushroom, pine pollen, and aronia powder; the food items had been imported from India, Vietnam, Turkey, the United States of America, Russia, China, and Poland. Among these food items, the radiation level corresponding to 137Cs in Neungi mushroom, imported from Russia, was the highest, with a concentration of 79.28 Bq/kg. In this study, the radiation concentrations of all the collected food items were below the maximum permitted level of 100 Bq/kg. In the future, it may be necessary to monitor various food items based on consumption trends in order to alleviate consumer anxiety regarding radioactivity in food. Key Words: radioactivity, 137Cs, imported processed food items

Calibration of a SPECT-CT gamma camera with child and adult thyroid-neck phantoms for in vivo monitoring of radioiodine in the exposed population in case of nuclear emergency

The need to quantify the uptake of 131I in the thyroid of the exposed population or workers is one of the main concerns to take into account in case of nuclear or radiological emergencies. In such scenarios, due to the high volatility and rapid intake by inhalation of 131I, it is very important a rapid identification of the exposed individuals to know their level of internal contamination in order to establish action protocols and countermeasures. In vivo measurements of 131I in the thyroid by gamma spectrometry at Whole Body Counters (WBC) is the recommended technique, but it is difficult to manage in case of a large number of individuals potentially exposed. It is known that gamma cameras located in the nuclear medicine services are available at most hospitals and could be used as an alternative method in order to provide support in the emergency response. Thus, this work describes a methodology to calibrate this kind of equipment with anthropometric phantoms to carry out direct measurement of 131I in thyroid for the quantification of internal contamination of the exposed population. A Gamma Camera (GC) of a public hospital from Madrid, H.U. La Paz, was calibrated for such purpose taking into account that a realistic geometry (10 cm distance from GC to phantom) and a rapid screening (counting time of 300 s with collimators removed) of internally contaminated individuals is necessary at early stage response. The calibration factors obtained for 131I vary with thyroid size being in the range of 0.0459 to 0.0541 cps·Bq-1. The minimum detectable activity (MDA) also varies with the thyroid size of the phantoms being in the range of 67 Bq to 79 Bq. An estimation of minimum detectable effective dose for children (E(70)) and adults (E(50)) has been carried out, taking into account such MDA values. Results show that, assuming a scenario of acute inhalation of 131I by members of the public, this methodology allows estimating doses far below 1 mSv three days after the intake. Moreover, the validation of the methodology has been carried out by participating in an international intercomparison exercise (CATHYMARA project, EC-OPERRA 2016–2017) for the in vivo measurement of 131I in thyroid to the exposed population in emergencies.

Optimizing UAV-based radiation sensor systems for aerial surveys

In this study, we qualitatively and quantitatively analyzed unmanned aerial vehicle (UAV)-based radiation sensor systems suitable for specific survey missions. We examined a variety of UAVs, radiation sensors, and radiological survey missions; after reviewing previous studies that developed and conducted field tests, we categorized them by mission and suggested suitable types of UAVs and radiation sensors for each mission. To quantitatively analyze various system designs previously suggested, we proposed a new figure of merit (FOM) formula that can explain the mutual effects of parameters of both radiation sensors and UAVs on system performance. After targeting a radiological survey mission, we selected UAV and radiation sensor types qualitatively. Then, the quantitative FOM formula can be employed to efficiently assess whether the system achieves the required minimum detectable activity (MDA) without field test, while keeping the error of the MDA values in the order of 100. After defining the constraints including the proposed FOM formula, we replicated a severe nuclear power plant accident scenario. We found that one fixed-wing UAV and multiple rotary-wing UAVs are the minimum number of UAVs, and thus the optimal system for timely achievement of a satisfactory MDA and estimation of the three-dimensional radiation distribution contributed by both ground radiation and an atmospheric radioactive plume.

Minimum detectable activity of plastic scintillator for in-situ beta measurement system in ground water

Abstract The minimum detectable activity (MDA) value was derived according to the flow rate of the sample and degree of amplification of the device by sending the sample directly from the collection site to the detection part through a pump. This method can lead to reduction in time and cost compared to the existing measurement method that uses a pre-treatment process. In this study, experiments were conducted on 3H and 90Sr, which are the major pure beta-emitting radionuclides, by setting the sample flow rate and the amplification gain as factors. The MDA values were derived according to the flow rates, considering that the flow rate can affect the MDA values. There were no change in the MDA under different flow rates of 0, 600, 800, and 1000 mL/min. Therefore, it was confirmed that the flow rate may not be considered when collecting samples for monitoring in actual field. As the degree of amplification of the amplifier increased, the time required to reach the target MDA decreased. When the amplification was quadrupled, the detection efficiency increased by approximately 23.4 times, and the time to reach the MDA decreased to approximately 1/550 times. This method offers the advantage of real-time on-site monitoring.

Optimisation of radioxenon measurement for comprehensive nuclear test-ban treaty

ABSTRACTThe international monitoring system (IMS) has been developed to verify compliance with the comprehensive nuclear test-ban treaty (CTBT) and radionuclide monitoring stations are the smoking gun for underground nuclear explosions identification. One of the main objectives of the verification regime is to improve the sensitivity of measurements providing background reduction and, as a result, decrease the minimum detectable activity (MDA) values. At this ENEA laboratory an anticoincidence system has been developed: the system is comprised of a high purity germanium (HPGe) detector surrounded by a low–background shield and two plastic scintillators able to detect coincident cosmic-ray interactions. Tests conducted with the anticoincidence system have shown a reduction of the Compton continuum that contributes to the spectrum background and the measured MDA values, compared to those obtained using the standard system, decreased for all the four radioxenon isotopes.

Presence of artificial radionuclides in samples from potable water and wastewater treatment plants

Human activity, such as the operation of nuclear power plants (NPPs) and the use of radionuclides in nuclear medicine, results in the presence of artificial radionuclides in surface waters, which may even reach potable water treatment plants (PWTPs) and wastewater treatment plants (WWTPs).In this study, water and sludge samples from a PWTP are radiologically monitored. The incoming water of the plant is influenced by the presence of an NPP upstream. Two WWTPs receiving wastewater from medical centres and other origins are also studied. As a result, 131I, 60Co and 137Cs have been determined in the dewatered sludge samples from the PWTP, while 131I, 99mTc, 67Ga and 111In were detected in the sludge samples from the WWTPs. The radionuclide activities in the influent water from the WWTPs studied were lower than the minimum detectable activity values. Therefore, on the basis of our results, the analysis of sludge samples is very useful as it enables the concentration of any radionuclides that may be present in the incoming water.Lastly, as higher activity of 131I was detected in the samples studied, the total effective dose was assessed for WWTP workers, as they handle dewatered sludge containing this radionuclide. It can be concluded that there is no risk in terms of total exposure.

Radioactivity, radiological risk and metal pollution assessment in marine sediments from Calabrian selected areas, southern Italy

The two most significant categories of physical and chemical pollutants in sediments (radionuclides and metals) were investigated in this article, in order to evaluate pollution levels in marine sediments from eight different selected sites of the Calabria region, south of Italy. In particular samples were analyzed to determine natural and anthropic radioactivity and metal concentrations, in order to assess any possible radiological hazard, the level of contamination and the possible anthropogenic impact in the investigated area. Activity concentrations of 226Ra, 232Th, 40K and 137Cs were measured by High Purity Germanium (HPGe) gamma spectrometry. The obtained results show that, for radium (in secular equilibrium with uranium), the specific activity ranges from ( $ 14 \pm 1$ ) Bq/kg dry weight (d.w.) to ( $ 54 \pm 9$ ) Bq/kg d.w.; for thorium, from ( $ 12 \pm 1$ ) Bq/kg d.w. to ( $ 83 \pm 8$ ) Bq/kg d.w.; for potassium, from ( $ 470 \pm 20$ ) Bq/kg d.w. to ( $ 1000 \pm 70$ ) Bq/kg d.w. and for cesium it is lower than the minimum detectable activity value. The absorbed gamma dose rate in air (D), the annual effective dose equivalent (AEDE) outdoor and the external hazard index ( $ H_{\rm ex}$ ) were calculated to evaluate any possible radiological risk, mainly due to the use of marine sediments for the beach nourishment. The results show low levels of radioactivity, thus discarding any significant radiological risk. Some metals (As, Cd, Crtot, Hg, Ni, Pb, Cu, Zn, Mn and Fe), that could be released into the environment by both natural and anthropogenic sources, were investigated through inductively coupled plasma mass spectrometry (ICP-MS) measurements and compared with the limits set by the Italian Legislation, to assess any possible contamination. Experimental results show that they are much lower than the contamination threshold value, thus excluding their presence as pollutants. The degree of sediment contaminations were quantified using enrichment factor (EF) and geoaccumulation index ( Igeo) for some potential hazardous elements. Results show that EF and Igeo values of As, Pb and Mn were the greatest among the studied metals. Data of this preliminary study could be helpful in the future to obtain background levels in marine sediments of the investigated region and to develop environmental regulatory frameworks.

Emergency Radiobioassay Method for Determination of ⁹⁰Sr and ²²⁶Ra in a Spot Urine Sample.

A new radiobioassay method has been developed for simultaneous determination of (90)Sr and (226)Ra in a spot urine sample. The method is based on a matrix removal procedure to purify the target radionuclides from a urine sample followed by an automated high performance ion chromatographic (HPIC) separation of (90)Sr and (226)Ra and offline radiometric detection by liquid scintillation counting (LSC). A Sr-resin extraction chromatographic cartridge was used for matrix removal and purification of (90)Sr and (226)Ra from a urine sample prior to its introduction to the HPIC system. The HPIC separation was carried out through cation exchange chromatography using methanesulfonic acid (75 mM) as the mobile phase at 0.25 mL/min flow rate. The performance criteria of the method was evaluated against the American National Standard Institute ANSI/HPS N13.30-2011 standard for the root mean squared error (RMSE) of relative bias (Br) and relative precision (SB) at two different spiked activity levels. The RMSE of Br and SB for (90)Sr and (226)Ra were found to be satisfactory (≤0.25). The minimum detectable activity (MDA) of the method for (90)Sr and (226)Ra are 2 Bq/L and 0.2 Bq/L, respectively. The MDA values are at least 1/10th of the concentrations of (90)Sr (190 Bq/L) and (226)Ra (2 Bq/L) excreted in urine on the third day following an acute exposure (inhalation) that would lead to an effective dose of 0.1 Sv in the first year. The sample turnaround time is less than 8 h for simultaneous determination of (90)Sr and (226)Ra.

Activity concentrations of 226Ra, 232Th, 40K and 137Cs radionuclides in Turkish medicinal herbs, their ingestion doses and cancer risks

Twenty-two medicinal herb samples, each representing a distinct species, were collected from Turkish markets and measured by the gamma spectrometric method. The activity concentration of 226Ra in medicinal herbs was found in the range of minimum detectable activity (MDA) and 15.1 ± 2.2 Bqkg−1. The activity concentration of 232Th ranged from MDA values to 3.5 ± 0.8 Bqkg−1. The activity concentration of 40K varied between 50.0 ± 16.8 and 1311.5 ± 57.3 Bqkg−1. All 137Cs activity concentrations of medicinal herbs were found to have lower than MDA values. The bone surface dose, lower large intestine and colon doses were found to be 182.9, 18.8 and 18.7 µSvy−1, respectively. The highest committed effective dose originated from the annual ingestion of 1 kg medicinal herb was calculated notably low as 9.0 µSv. The cancer risk of ingestion of medicinal herbs was found to be small enough to be neglected. The selected Turkish medicinal herbs are considered safe for human consumption.

Cs-137 in Sand and Seawater Samples from Piraquara Beach, Brazil: Discharge site of effluents from the Angra dos Reis Nuclear Power Plants

This study presents the Cs-137 radionuclide concentration and activity in sand profile and seawater samples from Piraquara Beach (PB) and from an adjacent small stretch of sand used as a beach. Both sites are located near the discharge point for cooling water and liquid effluents from the Almirante Alvaro Alberto Nuclear Power Station (CNAAA) in Brazil. The chemical composition of the sand samples was determined by granulometric analysis, elemental chemical characterization, and X-ray diffraction (XRD). Mineral sorbents for the Cs-137 radionuclide were found close to the discharge point. The presence of Cs-137 radionuclides in sand and seawater samples was determined by gamma spectrometry analysis, which was also used for seawater samples after absorption by ammonium phosphomolybdate (APM). The Cs-137 radionuclide activity measurements were lower than the minimum detectable activity (MDA): sand < 0.31 Bq.kg -1 , direct analysis of seawater < 0.42 Bq.L -1 , and seawater with APM < 0.004 Bq.L -1 . The aim of this study was to measure the amount of the Cs-137 radionuclide in the deeper layers of PB. A determination of radioactive exposure to individuals was not performed because the result values were lower than the MDA values. Our results indicate that the study site shows no contamination by the Cs-137 radionuclide.

Minimum detectable activity for NaI(Tl) airborne γ-ray spectrometry based on Monte Carlo simulation

The determination of the effective minimum detectable activity (MDA) of radionuclides by a detection system plays an important role in environmental radiation monitoring. In this study, the responses of an NaI(Tl) airborne γ ray spectrometry (AGRS) system to different radionuclides (137Cs and 131I) were investigated using the Monte Carlo technique. The MDA values were determined under different conditions according to the counting spectra obtained from the Monte Carlo simulation. The equivalent mass thickness method was applied to the Monte Carlo modeling for monitoring ground radiation to reduce statistical uncertainty. The secondary source method was used to monitor both air and ground radiation. A quadratic relationship was found between the MDA and activity concentration. An exponential relationship was found between the MDA and altitude. The MDA of a specific radionuclide from external detectors was found to be superior to that obtained from internal detectors under the same conditions. The MDA values in an NaI(Tl) AGRS system under different conditions can be estimated based on the results of this study.

Natural tritium determination in groundwater on Mt. Etna (Sicily, Italy)

Tritium is a naturally occurring radionuclide, due to interactions of cosmic-rays with the upper layers of the atmosphere; but its presence in the environment is mainly due to residual fallout from nuclear weapons atmosphere tests, carried out from 1952 till 1980. Tritium reaches the Earth’s surface mainly in the form of precipitation, becoming part of the hydrological cycle, then the interest of tritium content analysis in drinking water is both for dosimetry and health-risk and for using tritium as a natural tracer in the groundwater circulation system. This paper presents results from a survey carried out in the Mt. Etna area (east and west flanks) and in the southern side of Nebrodi in Sicily (Italy), in order to determine tritium activity concentrations in water samples by using liquid scintillation counter. The investigated areas show quite low tritium concentrations, much below the Italian limit of 100 Bq L−1 for drinking water and even comparable with the minimum detectable activity value. The effective dose due to tritium for public drinking water consumption was also evaluated.

Measurement of naturally occurring radionuclides in geothermal samples and assessment of radiological risks and radiation doses

The analysis of (226)Ra, (232)Th and (40)K radionuclides has been carried out in geothermal water and residue samples collected from six wells of geothermal power plant and disposal site, using gamma-spectrometry system equipped with a high-purity germanium detector. The activity concentrations of nine geothermal water samples were found to be lower than minimum detectable activity (MDA) values. The activity concentration of the residue samples ranged from 40 ± 4 to 2694 ± 85 Bq kg(-1) for (226)Ra, 33 ± 4 to 2388 ± 85 Bq kg(-1) for (232)Th, and MDA value to 967 ± 30 Bq kg(-1) for (40)K. In the study, some radiological indexes were examined and found to be higher than the reference values for majority of the residue samples. The annual effective doses arising from some residue samples were calculated to be higher than the permitted dose rate for the public, i.e. 1 mSv y(-1).