Applied Radiation and Isotopes最新文献

This study aims to establish phantom-solution systems suitable for estimating doses in boron neutron capture therapy (BNCT). The phantom containing three typical solutions, H₃BO₃, LiOH, and Gd(NO₃)₃·6H₂O with different concentrations and nuclide abundances have been studied since the nuclides ¹⁰B, ⁶Li, and ¹⁵⁷Gd are capable of absorbing thermal neutrons. The results indicate that all three phantom-solution systems, with suitable concentrations and nuclide abundances, effectively distinguish between the nitrogen dose and the hydrogen dose for dose measurement in BNCT.

The primary goal of this study was to develop a simulation model of a long counter available at Canadian Nuclear Laboratories (CNL). Using the Monte Carlo N-Particle version 6 (MCNP6) code, the model was used to calculate, as a function of incident energy, the number of counts recorded per source neutron, effective centre, and sensitivity. This study also carried out measurements of the neutron emission rate of and direct neutron flux at 2 m from an in-house ²⁵²Cf neutron source.

Carbon/Oxygen logging is an effective method to perform oil layer recognition and oil saturation calculation, which plays an important role in the evaluation of remaining oil after casing. At present, there are two main methods to calculate the ratio of carbon to oxygen (C/O). Compared with the energy window count method, the element yield method can avoid the influence of background count in the gamma spectrum and calculated carbon/oxygen value has the higher sensitivity and better accuracy, but it is still greatly affected by carbon and oxygen elements in the formation skeleton. Therefore, a new carbon/oxygen calculation method is proposed in this paper to overcome the influence of formation skeleton and improve the response sensitivity of Carbon/Oxygen logging. Based on Monte Carlo method, the inelastic gamma spectrum of pure sandstone and pure limestone skeletons are obtained. Based on spectrum analysis technology, the ratio relationship of carbon, oxygen yield and skeleton mark element (Si, Ca) yield in two skeletons are obtained. Using these ratio relationships, the carbon and oxygen yields from the sandstone and limestone reservoir skeletons are deducted from the total carbon and oxygen yield. A new carbon/oxygen parameter called the residual carbon/oxygen value (C/O)_R is calculated to perform oil-water recognition and a set of oil saturation calculation model suitable for the residual carbon/oxygen value is proposed. The environment application of the residual carbon/oxygen value is also analyzed. The study shows that the residual carbon/oxygen value has higher sensitivity than original carbon/oxygen value in oil layer recognition and has a great accuracy in oil saturation calculation. In environment application aspect, the residual carbon/oxygen value is basically unaffected by formation water salinity and is affected by wellbore fluid and wellbore size obviously. This new carbon/oxygen value calculation method has an important significance to improve the application effect of Carbon/Oxygen logging.

The radon-prone area of the Adamawa region is characterized by high radon concentrations, where no low-risk area was observed. This study aims to investigate about indoor thoron concentration in this area, using RADUET detectors, thoron progeny monitors and DTPS/DRPS. The indoor thoron concentration ranged between 17 and 1000 Bq m⁻³, with an average of 131 Bq m⁻³. 36% of dwellings have thoron concentration less than 100 Bq m⁻³ while 28% are above 300 Bq m⁻³. The thoron equilibrium factor of 0.04 was found to be two times higher than the globally assumed value. Thoron progeny contributes on average to 26% (1.9 mSv y⁻¹) of the total inhalation dose. The excess lifetime cancer risk due to thoron progeny is about 5%. These results justify that thoron cannot be neglected when assessing radiation doses. As only radon is regulated, such study will contribute to accelerate the regulation on thoron.

Polyvinyl alcohol (PVA) is a beneficial polymer capable of forming hydrogels helpful in a wide range of applications. Hydrogels based on cross-linking of PVA with borax, and able to incorporate with a decontaminating agent have been used in the decontamination of ⁹⁹Mo from contaminated surfaces. Aluminum hydroxide has been introduced in the formulations of PVA-borax, to increase the gel efficiency for ⁹⁹Mo decontamination from surfaces. The formulations were investigated with glass, stainless steel, and wood as examples of different surfaces. When the hydrogel is sprayed on different surfaces, it forms rapidly and adheres well. Moreover, the hydrogel was shown to efficiently decontaminate surfaces contaminated with ⁹⁹Mo by a maximum value of decontamination factor (D.F) for glass, stainless steel, and wood to be 43.5, 31.3, and 19.6 respectively.

Activation cross sections of alpha-particle-induced reactions on natural rhenium were measured. The stacked-foil activation technique and high-resolution gamma-ray spectrometry were used to derive the cross sections. The production cross sections of ^{190g, 189g, 188g, 187g, 186g, 185, 184}Ir, ¹⁸⁵Os, and ^{184g, 183g}Re were determined up to 50 MeV. The cross sections of ^185,184Ir were measured for the first time. The experimental results were compared with previous experimental data and theoretical calculations in the TENDL-2021 library.

The aim of the presented work was to develop folate based radiolabeled compound intended to be used as diagnostic aid for the various folate-receptor overexpressing cancers eg. breast cancer, brain tumors, lung cancer etc. Folate was directly radiolabeled with Tc-99m using Quality-by-Design and encapsulated in micellar nanocarriers. The authors are of the view that the stable radiolabeled folate could be of potential diagnostic value in cancers overexpressing folate receptors thereby opening novel possibilities to diagnostic applications of radiolabeled folate.

Summary for technical notes

Folic acid was directly radiolabeled with Tc-99m utilizing a quality by design approach. The experimental trials were designed using the Box-Behenken design with the concentration of drug, concentration of reducing agent and the incubation time as dependent variable and percent radiolabeling as the response for the same. The applied design in the method section was validated with a series of experiments and the percent labeling of the FA with Tc-99m was found to be around 94%. The radiolabeled compound was imperilled to stability evaluation by incubating the same with serum and physiological pH and the same was found to be stable at the end of 4h. On subjecting to DTPA challenge test, the compound displayed no change in the radiolabeling percentage thereby indicating the robustness of the formed Tc-99m-FA complex, The radiolabeled Tc-99m-FA was further encapsulated into micellar nanocarriers and the same were also found to be robust and stable.

Polymers are widely used today and the changes in their properties are investigated by different methods such as plasma irradiation. One of the most important methods for modifying polymers is cold plasma, by which the surface properties of the polymers can be changed under atmospheric pressure. In this study, the effect of plasma on Polystyrene (PS) and Polyamide 6 (PA6) samples was investigated. Surface and depth changes of the PS and PA6 have been investigated by various experimental techniques such as Fourier Transform Infrared (FTIR), X-ray Diffraction (XRD), Field Emission Scanning Electron Microscope (FESEM), Contact Angle (CA), and Positron Annihilation Lifetime Spectroscopy (PALS). The results of Attenuated Total Reflectance (ATR)-FTIR show that the chemical bonds of PA6 have been changed, and preserved in PS in the depths. The XRD results show that there are no volume changes for chemical bands. The FESEM analysis results reveal that the plasma causes digging and creates roughness on the surface. The CA measurement confirms the FESEM results and points out an increase in hydrophobicity after plasma processing. The PALS results indicate that the free volumes of the matter are changed after plasma irradiation in the depths of PS and PA6. In addition, the plasma also causes changes in the micrometer depth.

Neutron activation analysis is a highly sensitive non-destructive testing technique with important applications in industry, geoscience, medical therapy, etc. This work designed and optimized a thermal neutron device that utilized a portable D-D neutron generator, and the Monte Carlo method with the Geant4 toolkit was applied to simulation. The objective of the optimized design is to maximize the thermal neutron flux at the output surface and increase the utilization efficiency of the neutron generator. A parameter K was defined as a measure of the device's slowing capacity for neutrons and was used to determine the optimized device geometry. The simulation considered the contribution of different types and sizes of moderators and reflectors to the thermal neutron intensity to obtain the optimal size. The shielding protection of the device was then designed. The effectiveness of shielding with different thicknesses was evaluated using three dose reference points. The results indicated that the optimized device can achieve a maximum thermal neutron flux of 1.97 × 10⁵ n∙cm⁻²∙s⁻¹ at the output surface by using high-density polyethylene (HDPE) as the moderator and nickel as the reflector. It was determined that using 45 cm of HDPE and 9 cm of lead protection in sequence along the neutron head axis would reduce the dose rate at the reference point, located 5 cm from the surface of the device, below the safety limit of 2.5 μSv/h.