Iulian Andreicovici, Radu Seremet, Silvia Ise
et al.
Gamma spectra analysis is a key component for most environmental research programs. The TENORM nuclide evaluation is essential for mapping natural and artificial radioactivity, whether conducted in situ or in laboratory experiments, and the results support a wide range of interdisciplinary investigations. Preparation protocols are well established and straightforward, and hardware tools are increasingly robust and reliable. Numerous versatile software tools are available to complement the experimental inventory, enabling precise data acquisition. However, precision is sometimes debatable due to complicated algorithms, forced correlations, or references to unadapted libraries. To address pivotal environmental requirements and embrace simplicity as an ally, we present GaDeTool Geo, an algorithm and associated software developed for the automatic calibration of spectra, with emphasis on detectors that provide a quasi-linear response to energy. Provided the spectrum includes at least a natural component or background, calibration and analysis proceed in the most minimalist and natural way possible. A variety of customizations are being implemented in the online version, which will soon evolve into an application facilitating in situ analysis. In the meantime, GaDeTool Geo has been tested against commercial software, delivering reliable output by minimizing coincidence, scattering, and, where possible, self-attenuation effects.
This study introduces the process and methodology for determining residual radioactive levels in soil at a decommissioned nuclear facility site. Drawing on current research into decommissioned sites both domestically and internationally, this study reviews the approaches adopted by the International Atomic Energy Agency, the USA, and China for defining decommissioning end-state targets and establishing dose constraint values. A source investigation of soil pollution was first conducted to identify the types and quantify the activity concentrations of key pollutants. Subsequently, the radiological assessment defined decommissioning goals and dose constraints, identified exposure pathways and key parameters under open, unrestricted land-use scenarios, and developed an assessment model to calculate the effective dose using a forward calculation approach. By using the open-limit conversion method for reverse calculation, the residual radioactive level of the decommissioned final soil is ultimately determined. The allowable residual activity concentration values for three nuclides were calculated. The allowable residual activity concentration value for ^{60}\mathrm{Co} was 1.9 \cdot 10^{2} \, \mathrm{Bgkg^{-1}} , the allowable residual activity concentration value for ^{137}\mathrm{Cs} was 8.4 \cdot 10^{2} \, \mathrm{Bgkg^{-1}} , and the allowable residual activity concentration value for ^{90}\mathrm{Sr} was 1.1 \cdot 10^{5} \, \mathrm{Bgkg^{-1}} . The final determination of the allowable residual activity concentration values for the three nuclides will provide a basis for implementing, supervising, and accepting decommissioned engineering projects.
Previous efforts to investigate changes in the decay constants of radioactive nuclides discovered that solar flares can temporarily alter radioactive decay rates. Thus, discerning whether external factors affect radioactive decay rates is vital for understanding nuclear processes. This study sought to explore the effect of neutrinos on radioactive nuclei by constructing a gamma radiation detection system that employs a radioactive source in front of a neutrino emission system. Responding to cyclotron operations, each of the four detection systems registered gamma count rate decreases. The results of this study confirm that rises in neutrino flux affected the decay rates of the examined radioactive nuclides. Here we provide significant evidence that neutrinos affect the radioactive decay process. Neutrino detection is challenging due to the minuscule absorption in a stable nucleus. However, the study found a greater probability of radionuclides interaction with the neutrino.
Yehia Abbas, Ahmed El-Khatib, Mohamed Badawi
et al.
Polymer composites of polyvinyl chloride, PVC, were loaded up with micro and nano PbO/CuO particles. The added percentage of each by mass was 10 wt.%, 20 wt.%, 30 wt.%, and 40 wt.%, plus 40 wt.% of mixed composite (20 wt.% CuO + 20 wt.% PbO). The mass and linear attenuation coefficients of the investigated composites were measured as a function of gamma-ray energies going from 59.53 keV to 1408.01 keV utilizing standard radioactive point sources. To confirm the validity of these results the attenuation coefficients for bulk composites (PVC + PbO and PVC + CuO) were calculated by using the XCOM software. The results were in good agreement with the values obtained from the experimental work. By comparing the attenuation coefficients of the different composites it was found that those loaded with either nano PbO or CuO have higher values than those loaded with bulk sizes with the same percentage. Also, samples loaded with nano PbO have the highest attenuation coefficients even by comparing them with (20 wt.% CuO + 20 wt.% PbO), especially in the energy region below 1 MeV, but for greater energies, the values become very closed. The investigation of the mechanical properties of such composites due to the injection of bulk and nano metals reveals that tensile strength and Young's modulus of PVC nanocomposite sheets were notably increased with the increasing concentration of CuO and PbO nanoparticles. The CuO nanocomposite showed the highest values of flexural strength, toughness, and tensile strength among all the fabricated nanocomposite sheets.
As a historic challenge for humans, Martian colonization has been initiated by nuclear energy. A moving nuclear power plant could be imaginable known as a nuclear reactor rover. The design of the nuclear reactor rover has been performed where the important matter is how to make the caterpillar move the reactor and its facilities. Hence the slider length and contact point are proposed. The normalized heat transfer is analyzed by slide length and contact point where they are normalized as 1.0 and 10.0, respectively. Although the slider length of the caterpillar is proportional to heat transfer, the contact point shows the adverse values. Longer slider length and less contact point could be the optimized heat production system by the caterpillar which is the additional heat source except the other nuclear reactor. Any other planet could be considered as a potential human colony using the nuclear terraforming technology.
This work addresses the problem of propagating uncertainty from group-wise neutron cross-sections to the results of neutronics diffusion calculations. Automatic differentiation based on dual number arithmetic was applied to uncertainty propagation in the framework of local sensitivity analysis. As an illustration, we consider a two-group diffusion problem in an infinite medium, which has a solution in a closed form. We employ automatic differentiation in conjunction with the sandwich formula for uncertainty propagation in three ways. Firstly, by evaluating the analytical expression for the multiplication factor using dual number arithmetic. Then, by solving the diffusion problem with the power iteration algorithm and the algebra of dual matrices. Finally, automatic differentiation is used to calculate the partial derivatives of the production and loss operators in the perturbation formula from the adjoint-weighted technique. The numerical solution of the diffusion problem is verified against the analytical formulas and the results of the uncertainty calculations are compared with those from the global sensitivity analysis approach. The uncertainty values obtained in this work differ from values given in the literature by less than 1?10?5.
Ex vivo culture of human hematopoietic cells is a crucial component of many therapeutic applications. Although current culture conditions have been optimized using quantitative in vitro progenitor assays, knowledge of the conditions that permit maintenance of primitive human repopulating cells is lacking. We report that primitive human cells capable of repopulating nonobese diabetic (NOD)/severe combined immunodeficiency (SCID) mice (SCID-repopulating cells; SRC) can be maintained and/or modestly increased after culture of CD34+CD38− cord blood cells in serum-free conditions. Quantitative analysis demonstrated a 4- and 10-fold increase in the number of CD34+CD38− cells and colony-forming cells, respectively, as well as a 2- to 4-fold increase in SRC after 4 d of culture. However, after 9 d of culture, all SRC were lost, despite further increases in total cells, CFC content, and CD34+ cells. These studies indicate that caution must be exercised in extending the duration of ex vivo cultures used for transplantation, and demonstrate the importance of the SRC assay in the development of culture conditions that support primitive cells.
The manuscript clarifies the issues concerning the effective miniaturization of readout of the plastic scintillators while maintaining their high detection efficiency and sensitivity. Values obtained from the measurements of the chosen gamma emitters (60Co, 137Cs, 241Am), at various distances, were used to compare the detection efficiencies. The organic plastic scintillators, with the ternary system of different shapes and volumes, were chosen for the measurement. The detection parameters for the examined 1" PMT, with variable photocathode geometry, were experimentally found and compared to the normally used 2" PMT, with the circular type of photocathode. The primary aim of this work was to verify whether, in the case of mobile applications, such as UAV, it is possible to replace the currently bulky and quite heavy electronics with a miniature version and simultaneously preserve their detection parameters.
Aldo Parlato, Elio Tomarchio, Cristiano Calligaro
et al.
The methodology, developed for active testing of electronic devices under the radiations, is presented. The test set-up includes a gamma-ray facility, the hardware board/fixtures and the software tools purposely designed and realized. The methodology is so wide-ranging to allow us the verification of different classes of electronic devices, even if only application examples for static random access memory modules are reported.
This work presents the results of the study of radon concentration in soil gas for 187 measurements of soil samples collected from different locations of Gedarif town in Sudan using the can technique, containing CR-39. From in this work, the soil gas radon concentrations were ranged from 4.20 ? 0.61 kBqm-3 to 15.15 ? 1.62 kBqm-3 with an average of (9.10 ? 1.31) kBqm-3. The annual effective dose was calculated that ranged from 18.71 ? 2.73 mSv to 67.53 ? 7.22 mSv, with an average value of 40.57 ? 5.86 mSv. A good correlation was observed between the radon concentration and soil depth. It was found that soil radon gas concentration increased with depth. The radon concentrations in the soil samples were found to be larger than the allowed limit from the World Health Organization. The results of this work were compared with national and worldwide results.
The stability analysis of a nuclear reactor is an important aspect in the design and operation of the reactor. A stable neutronic response to perturbations is essential from the safety point of view. In this paper, a general methodology has been developed for the linear stability analysis of nuclear reactors using the lumped reactor model. The reactor kinetics has been modelled using the point kinetics equations and the reactivity feedbacks from fuel, coolant and xenon have been modelled through the appropriate time dependent equations. These governing equations are linearized considering small perturbations in the reactor state around a steady operating point. The characteristic equation of the system is used to establish the stability zone of the reactor considering the reactivity coefficients as parameters. This methodology has been used to identify the stability region of a typical pressurized heavy water reactor. It is shown that the positive reactivity feedback from xenon narrows down the stability region. Further, it is observed that the neutron kinetics parameters (such as the number of delayed neutron precursor groups considered, the neutron generation time, the delayed neutron fractions, etc.) do not have a significant influence on the location of the stability boundary. The stability boundary is largely influenced by the parameters governing the evolution of the fuel and coolant temperature and xenon concentration.