Radioactive Detection Research Articles

Changes in detection characteristics of CdTe X-ray sensors by proton irradiation

This paper reports on the performance changes in CdTe:Cl semiconductor X-ray detectors seen after irradiation with 50 MeV protons up to a fluence of 1.6⋅1011cm−2. The rationale for the irradiation parameters is described. Performance was quantified before and after irradiations by obtaining X-ray spectra with a barium-133 radioactive source and detectors cooled to −20°C. Energy resolutions, electron and hole drift lengths, and energy calibration parameters were extracted by fitting model spectra to the data. Ten crystals of dimension 10×10×1 mm3 were used, with two each being irradiated to 20%, 40%, 60%, 80%, and 100% of the maximum fluence. Each crystal is pixelized and the eight large pixels of area 9.6mm2 are analysed separately to allow estimation of uncertainties.The main observations are a strong decrease of the electron drift length and an increase of the electronic noise with fluence. The hole drift length shows a tendency to increase with fluence. A basic interpretation of some observations in terms of an increasing density of acceptor trap levels with fluence is given.

Automated extraction chromatographic radionuclide separation system for analysis of 90Sr in seawater

After the Fukushima Dai-ichi nuclear power plant disaster, the demand for a rapid method for the detection of environmental radioactivity increased drastically. Since the development of extraction chromatography using resins, analytical methods have advanced significantly in terms of simplicity and required labor. Herein, a home-made automated separation system that is applicable radio-extraction chromatographic separation techniques is reported. A simple, rapid, and high-throughput method was developed using this home-made automated separation system to analyze radiostrontium in seawater in emergency and routine situations. For emergency situations, radiostrontium in seawater is pre-concentrated on a cation exchange resin and consecutively purified using the Sr-resin. Fifty minutes are required for the purification of 90Sr in four samples (100 ml). The minimum detectable activity (MDA) for 90Sr is 0.2 Bq kg−1 at 100 min counting, with a recovery of 70% and counting efficiency of 95% in the scintillation mode. For routine monitoring, 90Y that is in equilibrium with 90Sr is first separated from the sample matrix using DGA. Treatment of 30 L of each seawater sample requires ~2 h. The MDA for this method is 0.3 mBq kg−1 at 400 min counting with a recovery of 70% and counting efficiency of 67% in the Cerenkov mode. By employing the developed method, the measured 90Sr in seawater collected from the coastal area of Korea is 0.92 ± 0.18 mBq kg−1, which is comparable to that reported previously. The measurements were obtained using a liquid scintillation counter, and the entire separation process was performed by employing the home-made separation system.

Physiological Animal Imaging with 68Ga-Citrate.

Gallium-68 is an ideal research and hospital-based PET radioisotope. The uptake mechanism of Gallium citrate is a combination of specific and non-specific processes, for example, vasodilatation, increased vascular permeability, plasma transferrin binding and lactoferrin and siderophores. In this study, by applying the 68Ge/68Ga generator product, a simple technique for the synthesis and quality control of 68Ga-citrate was introduced and was followed by preliminary animal studies. The synthesis of 68Ga-citrate was performed with a cationic method using the Scintomics automated synthesis system (Scintomics GmbH GRP module 4V). Since the standard procedure for quality control (QC) was not available, the definition of chemical and radiochemical purity of 68Ga-citrate was carried out according to the ICH Q2(R1) guideline. The standard QC tests were analysed with Scintomics 8100 radio-HPLC system equipped with a radioactivity detector. In this study, a New Zealand rabbit weighing 2520 g was used for PET/CT images. 68Ga-citrate synthesis was performed by a cationic method without using organic solvents. The labelling efficiency was found to be >98%. The HPLC method used to assess the radiochemical purity of 68Ga -citrate was validated as rapid, accurate and reproducible enough to apply it to patients safely. The physiological distribution of 68Ga-citrate was investigated in a healthy rabbit. The blood pool, liver, spleen, kidneys and growth plates were the most common sites of 68Ga-citrate involvement.

The purity identification and radiolabeling of α-mangostin with technetium-99m.

Alpha-mangostin (AM) is a natural compound that has the greatest activity in breast cancer. Radiolabeling AM with technetium-99 m (Tc-99m) has a function as breast cancer radiotracer. This study is aimed to identify the purity of Tc-99m-labeled AM. The identification method was conducted by a validated radio-high-performance liquid chromatography (HPLC) to confirm the chemical purity of the compound when the thin layer of chromatography and paper chromatography were used to find out the radiochemical purity (RCP). The validated radio-HPLC method obtained was C18 column with methanol:water (90:10) as the mobile phase and ultraviolet (243 nm) tandem radioactive detector (Gabi Star). The result showed that the RCP was 70.6% ± 2.87%. The analytical method met the validation criteria according to ICH Q2 (R1); thus, it could be applied in the identification. Unfortunately, the 99mTc-AM identification using radio-HPLC showed that the expected complex was not yet formed perfectly because of chemical impurities.

Isobars Separation (<sup>137</sup>Cs-<sup>137m</sup>Ba-<sup>137</sup>Ba) from Marine Sediments, in Order to Evaluate Directly Their Radioactive Contamination by Mass Spectrometry

Marine sediments contamination by fission product 137Cs-137mBa is a fact since the period 1945-65, when plus than two thousand atomic explosion tests were performed mainly in the southern seas, earth region with minor population density. However, marine flows have produced dissemination of this radioactive pair through the sea bottom all over the world, at different levels, because the sea movement and natural decaying of radioactive pair: parent 137Cs (t1/2 = 30.17 years) and daughter 137mBa (t1/2 = 2.55 minutes). Radioactive detection of these contaminants, compared as percentage with that of natural 40K (t1/2 = 1.28 × 109 years, 0.0118% of elementary K) leads to radiation contamination factor (RCF), as one possible unit to measure the radioactive contamination intensity in different regions, as well to determine if there is some other possible source of this contaminant, for example water cooling from power nuclear reactors when it is discharged at sea. However, radioactive detection always implies an unavoidable statistical variation, which makes more difficult to appreciate the changes as function of time and region. But at beginning of this century, mass spectrometry has got impressive advances, which makes it much more precise and sensible than radioactive detection [1]. This paper attempts to measure with other units the radioactive contamination: 137Cs atoms number per gram of sample, instead radioactivity, which could be more direct and with minor standard deviation that radioactive detection, solving at same time the isobars separation: 137Cs versus 137mBa plus elementary 137Ba (11.23% of Ba element).

The search for light dark matter with the NEWS-G spherical proportional counter

The NEWS-G (New Experiment with Spheres - Gas) collaboration searches for dark matter in the form of low-mass Weakly Interacting Massive Particles (WIMPs) using Spherical Proportional Counters (SPCs) filled with gases with low atomic masses. The operation of SEDINE, a 60-cm diameter prototype SPC filled with a mixture of neon and methane and installed at the Laboratoire Souterrain de Modane (LSM) in France, recently set new constraints on the spin-independent WIMP-nucleon scattering cross-section in the sub-GeV/c2 mass region. The collaboration is currently planning the installation a 140-cm ultra-low background SPC in a compact shielding at SNOLAB in Canada. Recent advances in radioactive background control, detector monitoring and sensor development, will provide for this next experimental phase of NEWS-G unprecedented sensitivity to low-mass WIMPs.

A Deep Learning Approach to Radioactive Seed Detection for Prostate Seed Implants

A Deep Learning Approach to Radioactive Seed Detection for Prostate Seed Implants

Study on the durability of concrete with FNS fine aggregate

As a by-product of nickel production, the ferronickel slag (FNS) puts a lot of pressure on the environment. It is becoming more and more urgent to deal with the increasing FNS. The aim of this study is to explore the durability of concrete with FNS fine aggregate. Two kinds of FNS with different storage time were selected. The radioactivity detection, XRD test and stability detection of FNS were conducted to ensure FNS can be used as construction materials. Then the durability of concrete with 13%, 27%, 40% and 50% FNS (by weight of fine aggregate) was investigated, respectively. It was found that the properties of concrete prepared from FNS with different storage time had little difference. The results indicated that 27% FNS replacement showed improvement in resistance to sulfate attack by 22% but the resistance to chloride ion penetration was not significantly influenced. Moreover, 40% FNS addition brought a 33% abrasion reduction than that of original concrete. SEM analysis showed that FNS produced more C-S-H gels and improved the microstructure of concrete. This study indicated that proper content of FNS can be used as fine aggregate and it was beneficial to the durability of concrete, especially to the abrasion resistance.

Non-radioactive electron capture detector for gas chromatography — A possible replacement for radioactive detectors

With detection limits in the low ppbv-range, electron capture detectors (ECD) are the most sensitive GC-detectors available for electron affine compounds, such as pesticides or chlorofluorocarbons. The working principle is based on the generation of free electrons at atmospheric pressure, which are usually emitted from a radioactive Ni-63 source. However, the use of radioactive materials leads to regulatory restrictions regarding purchase, operation and disposal. Recently, we introduced a novel ECD based on a non-radioactive electron source, achieving comparable detection limits, e.g. 1 ppbv (6 ng/l) for 1,1,2-trichloroethane. However, the linear range was still below that of radioactive ECDs. In addition, the detector volume was too large to be used as a GC detector. We now present an improved version of this non-radioactive ECD with significantly increased linear range of 6.5∙103 for 1,1,2-trichloroethane by implementing pulsed operation using a newly developed, autonomous control electronics. In addition, the detector volume is reduced to 100 μl, leading to faster response times, less memory effects and thus less peak broadening. The improved ECD with non-radioactive electron source reaches similar analytical performance compared to commercially available radioactive ECDs and thus can be used as a possible replacement of radioactive ECDs.

Development and comparison of two high accuracy methods for uranium concentration in nuclear fuel: ID-TIMS and K-edge densitometry

This study compares the two analytical methods for uranium concentration determination with high accuracy in uranium pellet: K-edge densitometer (KED) and the isotope dilution with thermal ionisation mass spectrometry measurements (ID-TIMS). Both techniques are compared in terms of time, generated radioactive effluent, simplicity, uncertainty estimation and detection limit. ID-TIMS shows lower detection limit and uncertainties than KED. However, the KED analysis time is shorter and generates less effluent. Both techniques were used for metrological analysis of uranium concentration in nuclear materials. The optimization of sample spike mixture isotope ratio for ID-TIMS to decrease uncertainties is also discussed.

Gross alpha and beta activities in drinking water from Goiás state, Brazil

Detection of gross alpha and beta radioactivity is important for a quick surveying of both natural and anthropogenic radioactivity in water. Furthermore, gross alpha and gross beta parameters are included in Brazilian legislation on quality of drinking water. In this work, a low background liquid scintillation spectrometer was used to simultaneously determine gross alpha and gross beta in samples of the public water supplies in the state of Goiás, Brazil, during 2010-2015. Sample preparation involved evaporation to concentrate the sample ten-fold. The results indicate that the water meets the radioactivity standards required by the regulations MS 2914/2011 of the Brazilian Department of Health. Concerning the high level of censored observations, a statistical treatment of data was conducted by using analysis methods of censored data to provide a reference value of the gross alpha and beta radioactivity in drinking water from the state of Goiás. The estimated typical activities are very low, 0.030 Bq.L-1 and 0.058 Bq.L-1, for gross alpha and gross beta, respectively.

1 micrometer high-efficient radiation resistant laser crystal: Nd:YSAG

With the increased requirements of solid state lasers from some special areas, such as space craft, reactor inspection and high level radioactive waste detection, developing laser crystals with radiation resistant ability become more and more important. In this study, high quality Nd-doped Y3Sc2Al3O12 (Nd:YSAG) crystal was grown successfully by Czochralski method and its radiation resistant ability was evaluated. XRD and Raman spectrum characterization results indicate that the structure of the as-grown crystal remain unchanged after the irradiation of 20 Mrad gamma-ray. Besides, the highest decrease of the transmittance was only 5% for the crystal after the irradiation of 10 Mrad gamma-ray suggesting the excellent radiation resistant ability of the crystal. Importantly, the almost unchanged absorption at 808 nm and fluorescence properties for the crystal after the irradiation of 20 Mrad gamma-ray confirmed the excellent radiation resistant ability of Nd:YSAG crystal again. High efficient LD pumped 1.06 μm laser was realized in Nd:YSAG crystal and the slightly decreases of the laser efficiency after the irradiation indicate the crystal can be considered as a promising high efficient radiation resistant laser material for the application in harsh radiation environment.

Network Time Synchronization of the Readout Electronics for a New Radioactive Gas Detection System

In systems with multiple radiation detectors, time synchronization of the data collected from different detectors is essential to reconstruct multi-detector events such as scattering and coincidences. In cases where the number of detectors exceeds the readout channels in a single data acquisition electronics module, multiple modules have to be synchronized, which is traditionally accomplished by distributing clocks and triggers via dedicated connections. To eliminate this added cabling complexity in the case of a new radioactive gas detection system prototype under development at the French Atomic Energy Commission, we implemented time synchronization between multiple XIA Pixie-Net detector readout modules through the existing Ethernet network, based on the IEEE 1588 precision time protocol. The detector system is dedicated to the measurement of radioactive gases at low activity and consists of eight large silicon pixels and two NaI(Tl) detectors, instrumented with a total of three 4-channel Pixie-Net modules. Detecting NaI(Tl)/silicon coincidences will make it possible to identify each radioisotope present in the sample. To allow these identifications at low activities, the Pixie-Net modules must be synchronized to a precision well below the targeted coincidence window of 500-1000 ns. Being equipped with an Ethernet PHY compatible with IEEE 1588 and synchronous Ethernet that outputs a locally generated but system-wide synchronized clock, the Pixie-Net can operate its analog to digital converters and digital processing circuitry with that clock and match time stamps for captured data across the three modules. Depending on the network configuration and synchronization method, the implementation is capable to achieve timing precisions between 300 ns and 200 ps.

A Portable Radioactivity Detection System for Outdoor Measurement of Concentration of Radioactive Caesium in a Mushroom Bed Log at a Low-level Contaminated Environment

A Portable Radioactivity Detection System for Outdoor Measurement of Concentration of Radioactive Caesium in a Mushroom Bed Log at a Low-level Contaminated Environment

Evaluation of 99mTc-Ethambutol Radiopharmaceutical Using High Performance Liquid Chromatography with Radioactive Detector (Radio-HPLC)

99m Tc-ethambutol is a radiopharmaceuticals used to determine the location of Mycobacterium tuberculosis that causes TB disease. To prepare this radiopharmaceuticals, several supporting compounds are required in addition to ethambutol and radionuclide compounds. These are mannitol as filler, SnCl 2 as a reducing agent and sodium pyrophosphate as co-ligand. The radiopharmaceuticals is made in the form of a lyophilized kit without 99m Tc radionuclides. The aim of this study was to determined the effect of reducing agents on 99m Tc-ethambutol preparation using the High Performance liquid chromatography (HPLC) equiped with radiodetector (radio-HPLC) to the quality of radiopharmaceuticals. In the previous study, the determination of radiochemical purity only used TLC by determining the amount of impurities TcO 2 and TcO 4 . This study was carried out more profoundly by using radio-HPLC to ensure the quality of radiopharmaceutical products that were made is actually 99m Tc-ethambutol. The Test were performed using paper chromatography, electrophoresis, radio-HPLC, and stability test of 99m Tc-ethambutol radiopharmaceuticals. The results showed that the radiopharmaceuticalkit of ethambutol is performing good physical characterictics and high radiochemical purity of 99m Tc-ethambutol both in analysis using paper chromatography, electrophoresis and radio-HPLC. The 99m Tc-ethambutol shown the peak at retention time (t r ) 7,97 minutes using UV and radioactive detector, C18 column, isocratic system using phosphate buffer 0,2 M pH 7,4 and Acetonitrile (90 :10), flow rate 0,8 mL/min. The radiochemical purity of 99m Tc-ethambutol is still remain high (91.44 ± 0.92%) after 27 days of kit were made. Key words : 99m Tc-ethambutol, radio-HPLC, TB disease, Mycobacterium tuberculosis , radiopharmaceuticals.

Feasibility study of a lead-monoxide-based dosimeter for real-time radioactive source detection in HDR brachytherapy

Recently, cancer has been treated using high dose rates (HDRs), which requires highly reliable treatment plans. In current clinical practice, phosphors are widely used. However, these are of limited use for real-time verification of radiation during HDR brachytherapy; moreover, there is a possibility of electrical error via high-energy radiation because a photodiode is used to detect visible light. Therefore, it is necessary to develop a new dosimeter that can detect gamma rays effectively. This study aimed to investigate the feasibility of a lead monoxide- (PbO)-based dosimeter to detect the position of a radioactive source in HDR brachytherapy. It was confirmed that the fabricated PbO dosimeter has sufficient response coincidence, reproducibility, and dose linearity for gamma rays. Based on these results, it is demonstrated that the PbO dosimeter complies with the general requirements of HDR brachytherapy monitoring systems. Thus, the PbO dosimeter is expected to be used commercially in the future.

A rapid, safe, and quantitative in vitro assay for measurement of uracil-DNA glycosylase activity.

Base excision repair (BER) is a frontline repair mechanism that operates through the G1 phase of the cell cycle, which ensures the genome integrity by repairing thousands of DNA lesions due to endogenous and exogenous agents. Its correct functioning is fundamental for cell viability and the health of the organism. Uracil is one of the most prevalent lesions that appears in DNA arising by spontaneous or enzymatic deamination of cytosine or misincorporation of the deoxyuridine 5'-triphosphate nucleotide (dUTP) in place of deoxythymidine 5'-triphosphate (dTTP) during DNA replication. In the first pathway, the uracil will preferentially pair with adenine, leading to C:G → T:A transition. When uracil in DNA arises from misincorporation of dUTP instead of dTTP, this process will result in A:U pairs. Organisms counteract the mutagenic effects of uracil in DNA using the BER repair system, which is mediated by a member of the uracil-DNA glycosylase (UDG) superfamily. Several assays evaluating the in vitro BER enzyme activity have been described so far. Some of these measure the BER activity by an oligonucleotide incision assay using radiolabeled duplex oligo. Others use circular double-stranded DNA substrates containing a defined lesion. The novelty of our method resides in its rapidity and safety (radioactive free detection) as well as in the possibility of having a reliable quantitative determination of UDG activity in both cell and tissue extracts. We also demonstrated the effectiveness of our method in assessing UDG activity in cell lines with a reduced DNA repair capacity and in different kinds of tissues. KEY MESSAGES: • Base excision repair is a fundamental repair mechanism ensuring the genome integrity. • Uracil is one of the most prevalent lesions that appears in DNA. • The mutagenic effects of uracil in DNA are mitigated by the uracil-DNA glycosylase. • Several assays evaluating the in vitro BER activity have been described so far. • A safe and quantitative assay evaluating the in vitro UDG activity is required.

Remote radiological assessment in the marine environment: A pilot study based on Cs-137 measurements and satellite observations in the Aegean Sea

A program concept has been developed to utilize sea parameters like sea surface temperature (SST), ocean colour (OC) and sea surface salinity (SSS), in order to explore their potential relations with 137Cs activity concentrations in sea water. These relations are expected to lead to the creation of an innovative tool based on remote sensing data and in real time 137Cs measurements, for the remote radioactivity detection of the Greek marine ecosystem both for routine control and emergency recordings. The presented results are a preliminary effort of the tool’s development. Remote sensing data have been acquired from MIRAS and MODIS instruments on-board ESA-SMOS and NASA-TERRA/AQUA satellites respectively. Satellite data comprise of SST and OC measurements. The ERL’s data of 137Cs activity concentrations (204 measurements) in seawater have been used for the period March 2012 to February 2015. Therefore, a) map analyses in a GIS including interpolation and integration of 83 real time measurements corrected with the effective half live of 7.2 y according to the monthly data of satelites and spatial linear regression have been implemented for the Aegean Sea, b) additional temporal analyses using linear and polynomial regression have been performed for the area of Souda- Crete, for which the most frequent measurements of 137Cs activity concentration in sea water have been measured in ERL. In this study, the first derived results on the correlation between SST measurements with 137Cs activity concentrations are presented, whereas the respective correlation with OC is being under invstigation. Further investigations include multivariate polynomial analyses into the Geographic Information System (GIS) platform with more extensive sampling and satellite data from new systems, whereas comparative correlations of 137Cs with seawater parameters derived by conventional means will be performed.

Improving the accuracy of single radioactive particle technique for flow velocity measurements

An original method of flow velocity estimation for a radioactive particle technique is presented. It is based on exchanging measured pulses into cumulative signals, and determination of time delay as time difference of occurrences of inflection points of cumulative curves. To determine the inflection points, a suitable algorithm is proposed. The preliminary results show that the proposed method is especially more precise than the classical cross-correlation approach. The preliminary results show that this method can be successfully applied in a laminar flow with any type of fluid, and can without limitation be applied for different types of radioactive detectors.

Development of an HPLC method for the radiochemical purity evaluation of [18F]fluoroestradiol

18F-Fluoroestradiol ([18F]FES), an estrogen analog, is a radiopharmaceutical used in Positron Emission Tomography (PET) that allows evaluating the tumor cell receptor profile and the best therapy strategy, the staging, the prognosis and the response to therapy in several breast cancer cases. As there is not any pharmacopoeia’s monograph of [18F]FES to standardize its quality control criteria, this work presents a new HPLC’s method to perform the [18F]FES radiochemical purity. A liquid chromatograph was used with radioactivity and ultraviolet detectors. Three concentrations of fluoroestradiol standard solution were used along the test. Their retention time was compared to its relative radiolabelled analogue to confirm its identity. Several mobile phases with acetonitrile and two mobile phase flows were tested to optimize the runs. Peaks symmetry, retention time, theoretical plates and resolution were analyzed to choose the best conditions. The mean retention time of both standard Fluoroestradiol and [18F]FES solutions were the same, demonstrating that [18F]FES formulation did not interfere with [18F]FES analysis. The best conditions were 1.2 mL/min and isocratic 40% V/V acetonitrile in water, which gave [18F]FES peak resolution greater than 6 and symmetry factor of 1. Thus, the developed method is ready to be validated and implemented in [18F]FES quality control routine in CDTN/Brazil.