Gamma Radiation Source Research Articles

EMPIRICAL FORMULA FOR THE DEPENDENCE OF HPGe-DETECTOR EFFICIENCY ON ENERGY AND DISTANCE FOR SHIELDED GAMMA-RAY SOURCES

The accuracy of gamma-spectrometric measurements in the isotopic analysis of shielded nuclear materials depends on the accuracy of the detector calibration in terms of energy efficiency, which should take into account corrections related to the measurement geometry and the absorption of γ-radiation by the shield material. The results of experimental studies of the energy efficiency of the HPGe-detector measured at fixed distances between the calibration source and the detector (50 and 100 mm) in the presence and absence of an absorbing shield made of stainless steel 12X18H10T (thickness ‒ 9.6 mm) are presented. On the basis of experimental data, an empirical description of the efficiency dependence for fixed distances between the gamma radiation source and the detector in the presence of a stainless steel absorbing shield was obtained.

Design of DAMC dye as a liquid scintillator for gamma ray detection

In this work, we designed a highly sensitive liquid scintillator (LS) based on 7-Diethylamino-4-methylcoumarin (DAMC) dye to detect gamma rays and localize Compton edges (CEs). The absorption and fluorescence peaks of DAMC at a concentration of 0.03 wt%. are 350 nm and 450 nm in toluene, respectively. Typical Photomultiplier tube (PMT) photocathodes have a high quantum yield in the 400 nm–470 nm region, where DAMC emission is most intense. The LS is packaged in a standard glass container with a 2.54 × 2.54 cm diameter and height. Different gamma radiation sources, including 137Cs, 60Co, and 22Na, were used to record LS responses for varying concentrations of DAMC in toluene. The results are compared with LS of the same concentration made with POPOP. The CE was determined by fitting the shoulder and tail of the pulse height distribution spectrum with a Gaussian-based distribution technique. In short, the CE was obtained at the half-height of the gaussian based distribution's fitting. The detector model created by GEANT4, a Monte Carlo code, was compared to the theoretical and experimental results. The CE location was obtained for both ionizing radiation interactions, and scintillation photon transit was simulated using the code. Finally, the experimental spectra were compared to the GEANT4 simulation for calibration, and the CEs were located.

Effects of low doses of gamma-radiation on the development of cardiac pathologies and heart rhythm disorders in male C57Bl/6J mice

Epidemiological studies have revealed a potential of low doses (< 500mGy) of gamma-radiation to induce cardiac pathologies, such as circulatory disease and ischemia. Involvement of Arrythmias in this pathological context is less clear. Indeed the development of arrythmia is reported in some but not all epidemiological studies (internal 137-Cesium (137Cs) exposure). The controversies can be attributed to the lack of understanding of the underlying mechanisms involved. Arrhythmias may be caused by an imbalance between stimulation of the sympathetic nervous system and inhibition by the parasympathetic. The objective of this project is to identify the signalling pathways involved in cardiac pathologies after exposure and over time. The study hypothesis would be that exposure to low doses of gamma-radiation induces tissue and nerve remodelling in the heart. We exposed C57Bl/6J male mice to whole-body single external doses ranging from 50 to 2000mGy from a 137Cs gamma-radiation source. Two post-exposure time points were studied (4 hours and 3 months). The heart function was monitored by Doppler ultrasound examination. Signalling pathways were examined by measuring levels of proteins involved in various cardiac functions by Western blotting and Sirius red staining of histological sections. In all, 4 hours after exposure, Western blot analysis showed a significant decrease in the expression of proteins involved in the conduction of cardiac nerve influx (Connexins 43 at 100 and 250mGy; P-value < 0.05) and in the synthesis of catecholamines (Tyrosine Hydroxylase at 50 and 250mGy; P-value < 0.05). These decreases may be responsible for heart contraction problems. Conversely, at 3 months post-exposure, we observed a significant increase in the levels of these same proteins of interest (Connexins 43 and Synapsin at 500 and 2000mGy; P-value < 0.05) which could induce long-term arrhythmia. These protein expression changes were observed only in the atrium and right ventricle. In addition, we observed interstitial fibrosis in the hearts of the mice exposed to the same doses (P-value < 0.05). Lastly, we observed a significant increase in the percentage of muscularized pulmonary arterioles (at 500mGy; P-value < 0.05), indicating the development of pulmonary hypertension. In summary, our results suggest that a single external exposure to a low dose of gamma rays can induce long-term functional alteration in the heart and that a potential dose threshold for such effect is below 500mGy.

Investigate shielding of standard materials and glass for stopping 662 KeV gamma ray penetrations

Calculations on shielding are required for the building of a gamma ray radiography exposure room to ensure worker exposure to radiation. A measurement used to evaluate the radiation diffusive and absorption characteristics of a medium is the linear attenuation coefficient ( ). Despite the fact that, as radiation moves through a medium, its absorption is influenced by the wavelength of the radiation as well as the thickness and composition of the medium, the linear absorption coefficient is crucial in the interaction of radiation with matter. This research uses a variety of materials as a shield for a gamma radiation source of emitted by Cs-137. The results obtained using a gamma source with a scintillation counter showed that the Half Value Thickness (HVT) of glass and aluminum were 3.57 cm, and 3.39 cm while for standard materials (concrete, iron, and lead) were 2.98 cm, 1.195 cm, and 0.58 cm respectively.

Correlation Method of 3-D Detection of Distant Sources of Gamma Radiation and Neutrinos by Intensity Interferometry

This paper discusses the physical and mathematical foundations and possible applications of the intensity correlation method for spatial three-dimensional (3-D) positional detection (finding the 3-D spatial position) of distant γ-ray or neutrino sources in real time or after a set of registered events. This method is based on the correlation of intensities of event sequences measured by several spaced-apart distant detectors. A specific consideration is made of the possibility of using a correlation intensities method for the analysis of the processes within a nuclear reactor, for the search of the hypothetical intra-terrestrial georeactor (planetocentric nuclear fission reactors), for the optimization of the method of single-photon-emission-computed tomography in medicine, and for other applications. The conditions of successful applications of the intensity correlation method for these systems are determined. The main problem with this method is connected to a relatively low count rate of registered neutrino events.

Effect of gamma irradiation on structural, morphological, optical and thermal properties of Ca doped CuO nanostructure thin films

Semiconductor optoelectronic and photonic devices are used in many harsh environment applications such as space and nuclear reactor etc. Gamma radiation in such environments significantly interacts with the semiconductor materials used in these devices, changing their structural, optical, morphological and thermal properties. Therefore, it is vital to investigate the gamma radiation effect of the material to be exposed to radiation in terms of the performance and lifetime of the application. In this study, nanostructured thin films were produced by doping different ratios (0, 0.3, 1.25, 2.5 and 5 mg/mL) of Ca to the copper oxide (CuO) is a semiconductor used in optoelectronic and photonic devices. The thin films produced were deposited on the glass substrate by the spin coating method. The effects of gamma rays on the structural, morphological, optical and thermal properties of the films were investigated by irradiating with different doses (1, 5, 15, 50, 100 and 150 kGy) used a Cobalt-60 gamma radiation source. The structural, morphological, optical and thermal properties of Ca doped CuO nanostructured thin films were investigated by using X-ray diffractometer (XRD), scanning electron microscopy (SEM), energy-dispersive spectroscopy (EDS), atomic force microscope (AFM), mechanical profilometer, UV-Vis spectrophotometry (UV-Vis) and thermogravimetric differential thermal analyzer (TG/DTA). The band gap of thin films were been calculated using Tauc’s plot. The obtained results showed that high-dose gamma radiation caused defects in undoped and Ca doped CuO nanostructured thin films and affected their structural, morphological, thermal and optical properties. Despite the resulting defects, Ca doped CuO nanostructured thin films showed higher absorption intensity and thermal stability against gamma rays. These results showed that Ca doped CuO nanostructured thin films are suitable for many harsh environment applications such as space and nuclear reactors.

From dangerous wastes to green construction materials, as thermally stable-radiation blocker, in presence of meso-porous magnesia and alumina

The nominal objective behind this study is to recycle iron-rich slag (GGBFS) and lead-rich glass waste (LRGW) as industrial solid wastes in the presence of meso-porous magnesia or alumina to produce sustainable, eco-friendly, and high-performance binding materials. Four NaOH-activated composites (AACs) pastes have been prepared: Pure alkali-activated slag (AAS), AAS-20%LRGW, AAS-20%LRGW-3% meso-porous MgO, and AAS-20%LRGW-3% meso-porous Al2O3. After the hardening process, the compressive strength was measured at 1, 7 and 28-days of normal curing (high humidity at 25 °C). Thermal stability test for all AACs, after 28-days, was conducted at 250, 500 and 750 °C. Two different radio-active isotopes (Cs-137 and Co-60) were used, as gamma radiation sources, to investigate the attenuation performance of all prepared AACs. The results confirmed that, among the four composites, AAS-20%LRGW-3% meso-porous MgO composite pastes possessed the highest compressive strength (29.3 MPa), highest thermal stability (25 MPa, 18.2 MPa and 10 MPa at 250 °C, 500 °C and 750 °C, respectively). Moreover, this composite has the highest gamma radiation shielding performance, whatever the intensity of the gamma-ray or firing temperature. At cesium isotope, it was found that the μ values were 0.199 ± 0.003, 0.197 ± 0.003, 0.194 ± 0.005 and 0.188 ± 0.005 cm−1 at 25, 250, 500 and 750 °C, respectively. This efficiency is attributed to the role of meso-porous MgO; it has a high surface area (8891 cm2/g), high adsorption capacity (2.042 cm3/g), and low average pore diameter (37.17 nm); these textural characteristics helped much in the generation of additional hydrates/binding phases such as calcium-silicate-hydrates (CSHs), calcium-aluminate-hydrates (CAHs), calcium-alumino-silicate hydrates (CASHs as gehlenite or hydrogarnet), hydrotalcite, magnesium silicate hydrates (MSHs) as well as sodium-alumino-silicate-hydrates (NASHs) and lead silicates (Pb3SiO5). All these phases were detected via XRD, TGA/DTG as well as SEM/EDX techniques. Moreover, the inclusion of meso-porous MgO enhanced the immobilization of hazardous lead according to the obtained data from the toxicity characteristics leaching procedure (TCLP). Hence, we recommend using AAS-20%LRGW-3%MgO composite as gamma-radiation blocker in medical fields and concrete landfills containing dangerous radioactive wastes.

Heavy alloy based on tungsten and bismuth: fabrication, crystal structure, morphology, and shielding efficiency against gamma-radiation.

W-Bi2O3 composites were fabricated using the hot isostatic pressing technique for the first time. The duration of the samples sintering was 3 minutes under conditions of high pressure and temperature. The study of microstructural features and chemical composition of sintered samples was carried out using scanning electron microscopy and energy-dispersive X-ray spectroscopy, respectively. The effect of temperature on the quality of the obtained W-Bi2O3 composites is determined. The densest samples were obtained at a pressure of 5 GPa and temperatures of 25 °C and 500 °C, the densities of which were 18.10 and 17.85 g cm-3, respectively. It is presented that high temperature exposure during sintering adversely affects both the composite density and microstructure due to the redox reaction accompanied by the reduction of Bi and the oxidation of W. The results of the W-Bi2O3 structure study using X-ray diffraction analysis showed that all samples included the main bulk-centered cubic W phase. The presence of the WO2 phase is noted only when the sintering temperature is increased up to 850 °C, which is confirmed by the appearance of diffraction peaks that correspond to 111 and 22-2 crystallographic planes. The shielding efficiency of the W-Bi2O3 composite against gamma radiation using the Phy-X/PSD software was evaluated. A Co60 isotope with an energy of 0.826-2.506 MeV was used as a source of gamma radiation. The calculation results were compared with those for Pb and Bi. Key shielding parameters such as the linear attenuation coefficient, half-value layer, tenth-value layer, mean free path, and effective atomic number are determined. The calculation results revealed that the W-Bi2O3 composite surpasses Pb and Bi in its shielding properties, which makes it promising for use as a prospective material for radiation shielding applications.

Radioactivity analysis of commonly available building and flooring material in Kerala, India

Building materials are primary sources of indoor gamma radiation. Therefore, we have made a detailed study of building materials which are being used extensively in the region. Primordial radionuclides namely uranium (238U), Thorium (232Th) and potassium (40K) were studied in the building materials. As of the results acquired, we can arrive at the following inferences: We have estimated specific activities of radionuclides, the radium equivalent and radiological risk parameters resulting from the gamma originating from building materials. The highest Radium equivalent activity was obtained for red clay brick and the minimum value obtained was for M-sand. M-sand is processed sand being used widely now a days in the region. Most of the building materials were found to have very low levels of Radium. As of the results we obtained, none of the building materials were found to pose any notable radiological health hazard.

Тривимірне моделювання як інструмент підвищення культури безпеки під час проведення робіт на радіаційно-ядерних об’єктах

As work is planned at the Shelter object (SO), minimizing doses to the personnel involved in these work is of great importance. This is of particular importance for the construction work with the dismantling of the structure, which is characterized by large collective effective doses, which are taken by the personnel during the hour of its implementation. The need to assign personnel doses, as well as optimize approaches to the radiation protection and, first of all, biological protection, is related to this already at the design stage. As the radiation situation will change during the dismantling of unstable structures, design solutions must take into account possible changes in the radiation dose when planning protective measures. To determine the intensity of the gamma radiation dose, a method of mathematical modeling based on the “point kernel” model is proposed. This approach makes it possible to carry out calculation and analysis of the radiation situation practically in real time. By means of the ChNPP VRdose Planner Pro program, a three-dimensional model of the SO roof outer shell with selected sources of gamma radiation and building structures with the protective screens properties was built. The radiation situation analysis was made and a radiation field visual display above the roof was shown. Models of building structures were created, which to some extent shield gamma radiation emanating from the SO Central Hall. Three-dimensional modeling of the early dismantled building structures was carried out using the program ChNPP VRdose Planner Pro v. 2.2.2. The application of methods of modeling radiation conditions during planning and execution of work in radiation-hazardous conditions will make it possible optimizing design solutions regarding the dismantling of unstable structures of the Shelter object, as well as optimizing the structure of radiation protection of personnel. The software package is a convenient tool for performing calculations of estimated exposure doses in radiation-hazardous conditions, enables quick and visual modeling of alternative work execution options, and enables optimization of the work performance process and personnel behavior in radiation-hazardous conditions. Based on the simulation, it is possible to create an interactive software package on the Chornobyl nuclear power plant training center for detailed personnel education and training. The results of the radiation situation analysis can be used in the performance of work planning in radiation-hazardous conditions to ensure the personnel protection in accordance with the ALARA principle.

Polilaktik Asit (PLA) / Titanyum Karbür (TiC) Nanokompozit Filmin Gama Işını Zırhlama Özelliklerinin İncelenmesi

In this study, gamma rays absorption properties of Polylactic Acid (PLA)/Titanium Carbide (TiC) nanocomposite films produced by containing 5% TiC were investigated. In applications where radioactive sources such as industry and medical are used, protection from the harmful effects of radiation is very important. Researches on materials to be used in shielding as an alternative to lead are becoming widespread. Comfortable, easily shaped, thin, durable, non-toxic to the environment and the user are the features sought in an ideal shield materials. For this purpose, the gamma ray absorption properties of the PLA/TiC nanocomposite material and its effect on radiation shielding were investigated. The linear attenuation coefficient value of the sample with different thicknesses was obtained with the NaI(TI) scintillation detector. A monochromatic gamma source, Cs-137 gamma radioisotope with 661.62 keV energy was used as the gamma radiation source. To determine the gamma ray shielding ability of materials Half value layer (HVL), tenth value layer (TVL) and radiation shielding efficiency (RPE) parameters of the material were calculated.

Measurements of Dispersed Phase Velocity in Two-Phase Flows in Pipelines Using Gamma-Absorption Technique and Phase of the Cross-Spectral Density Function

This paper concerns the application of the gamma radiation absorption method in the measurements of dispersed phase velocity in two-phase flows: liquid–gas flow in a horizontal pipeline and liquid–solid particles in a vertical pipe. Radiometric sets containing two linear 241Am gamma radiation sources and two NaI(Tl) scintillation detectors were used in the research. Due to the stochastic nature of the signals obtained from the scintillation probes, statistical methods were used for their analysis. The linear average velocity of the dispersed phase transportation was calculated using the phase of the cross-spectral density function of the signals registered by the scintillation detectors. It is shown that in the presented cases, the phase method can be more accurate than the most commonly used classical cross-correlation one.

Carrying out calculations of radiation safety during unloading and disassembly of cores of spent removable parts of reactors with liquid metal coolant of submarines

The results of calculations conducted to substantiate radiation safety while handling spent removable sections (SRS) of reactors with a liquid metal coolant (LMC) for nuclear submarines (NS) are presented in the article. The spent removable sections of reactors with liquid metal coolant for nuclear submarines are the sources of intense neutron and gamma radiation. Shielding should ensure the dose rate level for neutrons and gamma radiation which is not exceeding the values allowed for transportation of nuclear materials established by the NP-053-04 therefore it will attenuate emission of neutrons and gamma quanta by several orders of magnitude. A homogeneous model of the reactor core was used for calculations. Sources of neutrons and photons in the spent nuclear fuel (SNF) of the SRS, sources of photons in the reactor control devices and in construction materials (the reactor vessel and grids of fuel rods) have been taken into consideration while conducting the calculations. The computer code MCNP-4B was employed to calculate dose rates for neutrons and photons. In most cases direct calculations of dose rates for neutrons and secondary gamma-quanta using the MCNP-4B code provided acceptable results with admissible methodical errors. For the tasks with sources of gamma quanta direct calculation using the MCNP-4B brought unsatisfactory results due to strong attenuation. Various methods were applied to reduce dispersion: the first one is to assign importance to the cells and the second one is the method of weight windows iteration. Values of dose rates were obtained with acceptable errors. The results of the calculations provided necessary information to conduct operations to unload spent nuclear fuel from the SRS. The results of performed calculations were also used in the design and manufacturing of the shielding.

Determination of Lethality Curve for Cobalt-60 Gamma-Radiation Source in Rhesus Macaques Using Subject-Based Supportive Care.

Well-characterized and validated animal models are required for the development of medical countermeasures (MCMs) for acute radiation syndrome to mitigate injury due to high doses of total- or partial-body irradiation. Animal models used in MCM development must reflect a radiation dose- and time-dependent relationship, clinical presentation, and pathogenesis of organ injuries in humans. The objective of the current study was to develop the lethality curve for the Armed Forces Radiobiology Research Institute high level cobalt-60 gamma-radiation source in nonhuman primates (NHPs) after total-body irradiation. A dose-response relationship was determined using NHPs (rhesus macaques, N = 36, N = 6/radiation dose) irradiated with 6 doses in the range of 6.0 to 8.5 Gy, with 0.5 Gy increments at a dose rate of 0.6 Gy/min. Animals were provided subject-based supportive care including blood transfusions and were monitored for 60 days postirradiation. Survival was the primary endpoint of the study and the secondary endpoint included hematopoietic recovery. The lethality curve suggested LD30/60, LD50/60, and LD70/60 values as 5.71, 6.78, and 7.84 Gy, respectively. The results of this study will be valuable to provide specific doses for various lethalities of 60Co-gamma radiation to test radiation countermeasures in rhesus macaques using subject-based supportive care including blood transfusion.

Hematological and gastrointestinal protection effects of ginger rhizome on whole-body exposure of gamma radiation in mice1

Radiation can induce acute radiation sickness in different ways. In this study, we investigatedthe radio-protective efficacy of ginger extract (GE) against the gamma (γ) ray-induced damageon mice. The source of gamma radiation was cobalt 60 (Co-60). GE was administered to miceat a dose of 5 ml/kg intraperitoneally (IP) for 5 consecutive days before exposing them to 8Gray (Gy) (unit of ionizing radiation dose) of Co-60-gamma-radiation. Mice treated with GEbefore irradiation (pretreated group) showed a significant decrease in the mortality of lethally&#x0D; irradiated mice. Moreover, spleen weight was significantly increased. Besides, the GE treat-ment facilitated the recovery of white blood cells (WBC), and hemoglobin (HGB) cell number.&#x0D; Altogether, the findings indicated that ginger has remarkable effects on mice against hemato-poietic suppression and gastrointestinal damage caused by irradiation.

A new approach for modeling pulse height spectra of gamma-ray detectors from passing radioactive cloud in a case of NPP accident

A comprehensive approach for modeling the pulse height spectra of gamma-ray detectors from passing radioactive cloud in a case of accident at NPP has been developed. It involves modeling the transport of radionuclides in the atmosphere using Lagrangian stochastic model, WRF meteorological processor with an ARW core and GFS data to obtain spatial distribution of radionuclides in the air at a given moment of time. Applying representation of the cloud as superposition of elementary sources of gamma radiation the pulse height spectra are calculated based on data on flux density from point isotropic sources and detector response function. The proposed approach allows us to obtain time-dependent spectra for any complex radionuclide composition of the release. The results of modeling the pulse height spectra of the scintillator detector NaI(Tl) Ø63x63 mm for a hypothetical severe accident at a NPP are presented.

Radiation Monitoring Using Personal Dosimeter Devices in Terms of Long-Term Compliance and Creating a Culture of Safety

IntroductionRadiation-emitting devices are commonplace in the hospital with their ability to produce imaging for diagnoses, However, they hold a risk for device operators due to radiation exposure. Hospital systems have programs where physicians exposed to radiation are required to wear dosimeters to help record total radiation over time. Dosimetry readings over standardized recommendations can lead to hospital image issues and disciplinary action for physicians. This study aimed to discover the true values recorded on dosimeters with radiation exposure and discuss effective ways to encourage compliance with dosimeter usage.MethodologyThe study was completed over a course of 12 months with physicians from three different hospitals. Selection criteria included physicians considered to be “radiation workers” including those who operate x-ray machines, fluoroscopy units, unsealed and sealed isotopes, or those exposed to other sources of gamma or high-energy beta radiation. Two Plan-Do-Study-Act (PDSA) cycles were implemented. The first cycle was the first six months of the study and the second cycle was the second six months of the study. The first PDSA cycle had planned dosimeter reading check-ins every month. After this cycle ended, physicians were sent a survey anonymously asking if they had ever intentionally left behind their dosimeter. In the second PDSA cycle, a planned policy change was put into action where penalties for physicians who went over the recommended dosage were stopped. A monthly educational meeting where a discussion on the risks of radiation as well as protective mechanisms was implemented instead. The same monthly check-ins for dosimeter reading monitoring were employed again with the same survey regarding dosimeter adherence and usage being sent out at the end of the second cycle. Run charts were created to determine whether the policy change showed statistically significant differences in dosimetry readings.ResultsProtocol changes led to statistically significant (p<0.05) differences in radiation exposure recorded throughout the hospital systems. The primary PDSA cycle readings showed that hospital systems one (n=118), two (n=71), and three (n=32) had readings of 3.90 mSv, 2.55 mSv, and 2.02 mSv, respectively, which were all under the annual recommended dose limit of 10 mSv maximum per six months. However, an average of 94.4% (n=221) of physicians across all hospitals admitted to not using the dosimeter. In the second PDSA cycle after the policy change, the radiation doses were higher with an increase in the average cumulative dose at hospital system one of 255%, 328% at system two, and 323% at system three. Hospital systems one and two were both over the yearly limit of 20.0 mSv (7.70 mSv over for system one and 1.86 mSv over for system two) while system three remained under. The number of physicians who stated they always used the dosimeter during the second PDSA cycle increased to 83.9% in-hospital system one, 90.2% in-hospital system two, and 93.8% in-hospital system three.ConclusionCreating a culture of safety is critical for physician compliance. A comfortable work environment without unreasonable consequences creates an environment where physicians can focus on their health and safety while also doing what is in the workplace’s best interest. This culture can best be made with more collaboration between administrative staff and workers to create a trustworthy experience in hospital systems.

Study of Breakdown Voltage Stability of Gas-Filled Surge Arresters in the Presence of Gamma Radiation

The results presented in this article relate to the study of the impact of gamma radiation on the breakdown voltage of gas-filled surge arrester manufactured by CITEL, Littelfuse and EPCOS at an operating voltage of 230 V. Radium was considered as a source of gamma radiation in this research. The stability of breakdown voltage as well as the reliability of gas-filled surge arresters of different manufacturers were investigated using different statistical methods. This gas component operation was based on processes that lead to electrical breakdown and discharge in gas. The breakdown voltage has a stochastic nature, and it is a subject of certain distribution. One thousand voltage measurements of breakdown voltage were carried out for each value of the voltage increase rate, from 1 V/s up to 10 V/s, with and without the presence of additional gamma radiation. The detailed statistical analysis of the obtained experimental data was performed for both cases for all three GFSA types. Moreover, the cumulative distribution functions of breakdown voltage were presented with the applied Weibull distribution fit. The coefficient of correlation as well as Pearson χ2 test showed the strength of the relationship between the experimental distribution functions and the Weibull distribution fits. The values of the Weibull distribution coefficients for all voltage increase rates and for all components were also analyzed with and without gamma radiation.

The criterion for self-sustaining production of relativistic runaway electron avalanches by the positron feedback in thunderstorms

Relativistic runaway electron avalanches (RREA) occurring in thunderstorm large-scale electric fields are one of the sources of atmospheric gamma radiation. Relativistic feedback is the generation of RREAs by positrons or backscattered gamma rays of the previously produced RREAs. In strong electric fields, relativistic feedback can make RREAs self-sustainable that hypothetically can cause a terrestrial gamma-ray flash (TGF). This paper introduces a kinetic approach to study the positron relativistic feedback, which is predominant for the directly observed conditions within thunderstorms. The criterion for self-sustaining production of RREAs by the positron feedback in thunderstorms is derived. The discovered criterion allows one to obtain the parameters of the thunderstorm electric field required for self-sustaining RREA development with positron feedback for any altitude. It is shown that the derived conditions of self-sustainable RREA development are not achieved for the parameters of electric field observed in real thunderclouds.

Proliferation protection of uranium due to the presence of U-232 decay products as intense sources of hard gamma radiation

The objectives of the article are (1) to show the nuclear and physical causes of hard γ-quanta in the U-232 decay chain, (2) to propose tactics for handling uranium containing U-232, and (3) to assess the efficiency of its protective γ-barrier against uncontrolled proliferation. The authors show the general picture of the decay chains of U-232 nuclide transformations, on which the protection of uranium from its uncontrolled proliferation is based. During the decay of nuclei, their emission of α- or β-particles is only the first stage of the most complex process of rearrangement of both the internal structure of the nucleus itself, which consists in the rearrangement of the neutron and proton shells and the levels of its excitation, and in the rearrangement of the electron shells of the atom. As a rule, the daughter nucleus is in a highly excited state, which is removed by the emission of hard γ-quanta and internal conversion electrons. After the second case, the remaining excitation of the atom is removed by the emission of characteristic γ-quanta and Auger-electrons with characteristic γ-quanta. In addition, explanations are given for the quantum-mechanical reasons for the hard γ-radiation of Tl-208 and Bi-212, which complete the U-232 decay chain. The authors also proposed a tactic for handling uranium containing uranium-232. Since the hard γ-quanta of Tl-208 and Bi-212 appear only at the end of the U-232 decay chain, after its chemical purification from its decay products, U-232 itself does not pose a radiation hazard; therefore, at this time it is advisable to conduct all necessary operations for transporting the material to the plant, fabricating uranium-based fuel containing U-232, and transporting this fuel to the nuclear facility where it will be used.