Decay Chain Research Articles

The coupled effect of bentonite colloid and radioactive ingrowth on the transport of actinide decay chains in a single fracture

An analytical model is used to illustrate the colloid-facilitated transport of decay chain radionuclides (RNs) in the granitic fractured porous media. The colloid source is assumed from the erosion of the bentonite used as buffer materials in a spent nuclear fuel repository. A conservative assumption that all colloids are mobile and have reached a sufficiently high concentration before RNs start to release is made in the present model. The latest reported distribution coefficient (Kd) values for both local granite and bentonite are used for several calculations. Investigating the simulation results shows that the second peaks of the breakthrough curves and profiles for daughter RNs are found using various initial concentration boundary conditions. The second peak is caused by the radioactive decay of the parent RN. Therefore, the contribution of the parents of a decay chain should not be ignored when performing a safety assessment. Moreover, the existence of colloids promotes a higher influence of the parents on the transport of their daughter RNs. A conservative colloid velocity that could reflect the effect of hydrodynamic chromatography phenomena is also investigated. Simulation results show that the Kd values of RNs on rock and bentonite colloids are the dominant factor that affects the colloid-facilitated-decay chain transport in the fractured rock system.

Development of a stand-alone precalculated Monte Carlo code to calculate the dose by alpha and beta emitters from the Ra-224 decay chain.

Recent developments in alpha and beta emitting radionuclide therapy highlight the importance of developing efficient methods for patient-specific dosimetry. Traditional tabulated methods such as Medical Internal Radiation Dose (MIRD) estimate the dose at the organ level while more recent numerical methods based on Monte Carlo (MC) simulations are able to calculate dose at the voxel level. A precalculated MC (PMC) approach was developed in this work as an alternative to time-consuming fully simulated MC. Once the spatial distribution of alpha and beta emitters is determined using imaging and/or numerical methods, the PMC code can be used to achieve an accurate voxelized 3D distribution of the deposited energy without relying on full MC calculations. To implement the PMC method to calculate energy deposited by alpha and beta particles emitted from the Ra-224 decay chain. The GEANT4 (version 10.7) MC toolkit was used to generate databases of precalculated tracks to be integrated in the PMC code as well as to benchmark its output. In this regard, energy spectra of alpha and beta particles emitted by the Ra-224 decay chain were generated using GAMOS (version 6.2.0) and imported into GEANT4 macro files. Either alpha or beta emitting sources were defined at the center of a homogeneous phantom filled with various materials such as soft tissue, bone, and lung where particles were emitted either mono-directionally (for database generation) or isotropically (for benchmarking). Two heterogeneous phantoms were used to demonstrate PMC code compatibility with boundary crossing events. Each precalculated database was generated step-by-step by storing particle track information from GEANT4 simulations followed by its integration in a PMC code developed in MATLAB. For a user-defined number of histories, one of the tracks in a given database was selected randomly and rotated randomly to reflect an isotropic emission. Afterward, deposited energy was divided between voxels based on step length in each voxel using a ray-tracing approach. The radial distribution of deposited energy was benchmarked against fully simulated MC calculations using GEANT4. The effect of the GEANT4 parameter StepMax on the accuracy and speed of the code was also investigated. In the case of alpha decay, primary alpha particles show the highest contribution (>99%) in deposited energy compared to their secondary particles. In most cases, protons act as the main secondary particles in the deposition of energy. However, for a lung phantom, using a range cutoff parameter of 10µm on primary alpha particles yields a higher contribution of secondary electrons than protons. Differences between deposited energy calculated by PMC and fully simulated MC are within 2% for all alpha and beta emitters in homogeneous and heterogeneous phantoms. Additionally, statistical uncertainties are less than 1% for voxels with doses higher than 5% of the maximum dose. Moreover, optimization of the parameter StepMax is necessary to achieve the best tradeoff between code accuracy and speed. The PMC code shows good performance for dose calculations deposited by alpha and beta emitters. As a stand-alone algorithm, it is suitable to be integrated into clinical treatment planning systems.

Charged Higgs prospects in extended gauge models

In this paper, we explore the collider phenomenology of charged Higgs bosons in the context of a generic Beyond Standard Model scenario with extended gauge and scalar sectors. In such scenarios, the charged Higgs boson can decay via the W^{'}Z/ WZ^{'} channels. We formulate a search strategy for the H^{pm } in the channel sigma (g b rightarrow H^{pm }t){mathcal{B}mathcal{R}}(H^{pm } rightarrow W' Z) considering the interesting cascade decay chain H^{pm } rightarrow W^{'} Z rightarrow W^{pm } Z Z. We find that the charged Higgs can be discovered in final states with multiple hard leptons and/or b-quarks which future LHC experiments with sufficiently large luminosity ({mathcal {L}} = 1000~text {fb}^{-1} and above) can probe. We then study the phenomenological implications of our findings in the context of a generic toy model with a H^{pm } as well as in a more realistic electroweak symmetry breaking scenario.

Fat b-jet analyses using old and new clustering algorithms in new Higgs boson searches at the LHC

We compare different jet-clustering algorithms in establishing fully hadronic final states stemming from the chain decay of a heavy Higgs state into a pair of the 125 GeV Higgs boson that decays into bottom-antibottom quark pairs. Such 4b events typically give rise to boosted topologies, wherein b{bar{b}} pairs emerging from each 125 GeV Higgs boson tend to merge into a single, fat b-jet. Assuming large hadron collider (LHC) settings, we illustrate how both the efficiency of selecting the multi-jet final state and the ability to reconstruct from it the masses of all Higgs bosons depend on the choice of jet-clustering algorithm and its parameter settings. We indicate the optimal choice of clustering method for the purpose of establishing such a ubiquitous beyond the SM (BSM) signal, illustrated via a Type-II 2-Higgs Doublet Model (2HDM).

DQPB: software for calculating disequilibrium U–Pb ages

Abstract. Initial radioactive disequilibrium amongst intermediate nuclides of the U decay chains can have a significant impact on the accuracy of U–Pb ages, especially in young samples. For samples that can reasonably be assumed to have attained radioactive equilibrium at the time of analysis, a relatively straightforward correction may be applied. However, in younger materials where this assumption is unreasonable, it is necessary to replace the familiar U–Pb age equations with more complete expressions that account for growth and decay of intermediate nuclides through time. DQPB is software for calculating U–Pb ages while accounting for the effects of radioactive disequilibrium among intermediate nuclides of the U decay chains. The software is written in Python and distributed as both a pure Python package and a stand-alone graphical user interface (GUI) application that integrates with standard Microsoft Excel spreadsheets. The software implements disequilibrium U–Pb equations to compute ages using various approaches, including concordia intercept ages on a Tera–Wasserburg diagram, U–Pb isochron ages, Pb*/U ages based on single aliquots, and 207Pb-corrected ages. While these age-calculation approaches are tailored toward young samples that cannot reasonably be assumed to have attained radioactive equilibrium at the time of analysis, they may also be applied to older materials where disequilibrium is no longer analytically resolvable. The software allows users to implement a variety of regression algorithms based on both classical and robust statistical approaches, compute weighted average ages and construct customisable, publication-ready plots of U–Pb age data. The regression and weighted average algorithms implemented in DQPB may also be applicable to other (i.e. non-U–Pb) geochronological datasets.

Gamma-ray energies and intensities observed in decay chain 83Rb/83mKr/83Kr

Radioactive sources of the monoenergetic low-energy conversion electrons from the decay of isomeric ^{83textrm{m}}mathrm {{Kr}} are frequently used in the systematic measurements, particularly in the neutrino mass and dark matter experiments. For this purpose, the isomer is obtained by the decay of its parent radionuclide ^{83}mathrm {{Rb}}. In order to get more precise data on the gamma-rays occuring in the ^{83}mathrm {{Rb}}/^{83textrm{m}}mathrm {{Kr}} chain, we re-measured the relevant gamma-ray spectra, because the previous measurement took place in 1976. The obtained intensities are in fair agreement with the previous measurement. We have, however, improved the uncertainties by a factor of 4.3, identified a new gamma transition and determined more precisely energies of weaker gamma transitions.

Age-dating and assumptions testing of 226Ra and 228Ra decay series applied to barite chimneys and mud volcanoes in deepwater Gulf of Mexico

A chronological framework of ocean-based methane emissions is a prerequisite to identify the factors controlling the flux and duration of gas venting into the atmosphere.Here we report the results of a study of ubiquitous barite chimneys and barite-bearing mud volcanoes documented in association with methane seeps and gas hydrates at mid-bathyal depths in the Gulf of Mexico.The barites exhibit anomalously high 226Ra and 228Ra activities, orphans in the 238U/232Th decay chains, and are well suited for the application of 210Pb/226Ra and 228Th/228Ra dating methods. In order to account for the interference of impurities with the accuracy of the dates, gamma counts from paired raw and purified aliquots were evaluated. Chimneys yield a mean 228Th/228Ra age of 1.60 ± 0.25 yr (n = 16) and consistently younger 210Pb/226Ra ages. The biased 210Pb/226Ra ages are attributed to poor 210Pb counting efficiency, young chimneys with little 210Pb ingrowth and possibly an open system. Rapid vertical growth rates of 11.4 and 12.8 cm/yr established from 228Th/228Ra ages are comparable to barite chimney estimates from hydrothermal settings.In general mud volcanoes are distinguished from the chimneys by absence of 228Ra and 228Th and high 210Pb/226Ra ratios, occasionally >1 in the raw subsamples. A positive relation between 210Pb/226Ra and the amount of pyrite in the samples supports the contention that PbS, co-precipitated with pyrite in H2S-rich pore fluids, acts as the principal scavenger of external 210Pb resulting from decay of 222Rn in the pore fluids. The mud volcanoes 210Pb/226Ra assays yield consistent ages with a mean of 17.4 ± 1.8 yr (n = 9) after removal of the pyrite. The general absence of 228Ra and 228Th in the mud volcanoes, contrasting to their abundance in the chimneys, is attributed to the age difference between the barite geomorphic forms.The (228Ra/226Ra)o initial activities in the chimneys, representing the ratios in the fluids at the time of barite deposition, exhibit statistically distinct values of 1.084 ± 0.015 (n = 28) and 0.752 ± 0.023 (n = 4) at the two sampling sites separated by a 265 km stretch. These (228Ra/226Ra)o values match the range of oil-field brine values from deep siliciclastic reservoirs in the US Gulf Coast. The fluids maximum migration time from the source to the seafloor is estimated to be <20 yr on the basis of 228Ra presence in the chimneys. The assessment based on the radiometric ages supports the notion that barite deposition in the Gulf of Mexico is a relatively recent event.

Role of quasiparticle structure in α decay of superheavy nuclei

We use the superfluid tunneling model (STM) to calculate the half-lives of \ensuremath{\alpha} decays of odd-$A$ and odd-odd superheavy nuclei (SHN) with $Z\ensuremath{\ge}100$ and $A\ensuremath{\ge}250$. The experimental data are reproduced to accuracies comparable to other contemporary models of the \ensuremath{\alpha} decay of the SHN. We then apply the STM to examine the influence of the quasiparticle structure on the properties of the chains of \ensuremath{\alpha} decays arising from odd-$A$ SHN. Using representative calculations of the one-quasi-particle structure of odd-$Z$ and odd-$N$ SHN, we illustrate the important role played by high-\ensuremath{\Omega} orbitals in defining the observed characteristics of the \ensuremath{\alpha}-decay chains. We point out sources of possible ambiguity that may arise due to the quasiparticle structure when assigning \ensuremath{\alpha}-decay chains to specific SHN.

Preparation of low-radioactive high-purity enriched 100MoO3 powder for AMoRE-II experiment

This paper describes preparing radiopure molybdenum trioxide powder enriched with Mo-100 isotope for the AMoRE-II experiment. AMoRE-II, the second phase of the AMoRE experiments, will search for the neutrinoless double-beta decay (0νDBD) of the 100Mo isotope using over 100 kg of 100Mo embedded in 200 kg of ultra-pure Li2100MoO4 bolometric crystals. Efficient purification technology was developed and adapted to purify 100MoO3 powder with a 5 kg per month production capacity. Based on the ICP-MS analysis of purified powder, the 232Th and 238U were reduced to &amp;lt;9.4 μBq/kg and &amp;lt;50 μBq/kg, respectively. The concentrations of potassium, transition metals, and heavy metals were lower than 1 ppm. HPGe counting confirmed the reduction of progenies from the 232Th and 238U decay chains, reporting upper limits of &amp;lt;27 μBq/kg for 228Ac and &amp;lt;16 μBq/kg for 228Th. The 226Ra activity was acceptable at 110 ± 30 μBq/kg. In the last 3 years, 100 kg of pure 100MoO3 powder was produced. The production yield for the final purified product was above 90%, while irrecoverable losses were under 1.5%, and all by-products could be recycled further.

The α-particle clustering and half-lives of the newly discovered 207,208Th decay chains within relativistic-Hartree-Bogoliubov approach

The structural and decay properties of the ground state of recently discovered neutron-deficient 207Th and remeasured 208Th isotopes Yang et al. (2022) [26] is examined using the Relativistic-Hartree-Bogoliubov (RHB) formalism using the DD-ME2 parameter set within the preformed cluster-decay model (PCM). The relativistic medium-dependant R3Y so-called DD-R3Y NN potentials are for the first time used to obtain the nucleus-nucleus potential as input into the PCM. The penetration probability is calculated using the WKB approximation, and the preformation probability (Pα) is estimated using our newly derived formula, which is based on parameters well known to influence the α -particle radioactivity. A close correlation is observed between the α-preformation factor and the crucial role of the pairing correlation in the α-decay process. Furthermore, the Pα values for the even-even nuclei are generally found to be of higher magnitude than those for the odd-A nuclei. Our results further affirm that the odd-even staggering effect on the Qα values and its accompanying effects on other observables such as the charge radii and the decay half-lives, which can be largely attributed to the pairing correlation and Pauli blocking of the unpaired valence nucleons.

ESTIMATION OF THE GAMMA-RAY FIELD IN AIR FROM RADIOACTIVE SOURCES IN THE GROUND BY NUMERICAL SOLUTION OF THE BOLTZMANN TRANSPORT EQUATION.

Gamma-ray field in air from radioactive sources uniformly distributed in the ground is calculated by numerically solving the photon transport equation. The scattered flux is developed on the Legendre polynomials basis of the spherical harmonics method and a double P1 approximation is applied. The method is implemented in the Octave programming package. The calculation of the gamma-ray field is also done by Monte Carlo simulation using an optimised geometry model of the soil-air medium that is implemented in Geant4 simulation code. The results obtained by the two methods are in good agreement. The computing time for the spherical harmonics deterministic method is significantly less than the Monte Carlo simulation. Dose rate conversion factors in the air are calculated for the natural radioactive series of 238U and 232Th and for 40K nuclide and for soils contaminated by various radionuclides. The results are in agreement with the published theoretical and experimental studies.

Force decay of orthodontic elastomeric chains: A systematic review

In orthodontic therapy elastics and elastomeric chains are commonly used as an active component. These synthetic elastic materials are not supposed to be ideal, as they are sensitive to prolonged exposure to saliva, water, enzymes, temperature variations and external factors. The main disadvantage of elastomeric auxiliaries is their inability to sustain the delivered force for an extended period of time. The objective of this review is to determine the time taken by the elastomeric chains force to degrade after stretching and to assess oral environment and external factors affect the decay force of elastomeric chains. Databases such as PubMed, Medline, and the Cochrane Library are searched electronically. Additional sources (Google Scholar, clinicaltrails.gov) were manually searched for additional trials or protocols until December 2021 Studies involving in vitro and in vivo exposure of elastomeric chains in various factors like, temperature, saliva, beverages, food, paste, mouthwash, etc were included. 18 studies included primarily focused on the force decay in E-chains and also the associated external factors. The force decay of the Elastomeric chains was affected by time, temperature and environment. The force decay of the elastomeric chains was affected by time, temperature, and environment. The greatest effect on the elastomeric chain is shown by temperature. Force loss increased with increasing temperature, as expected of a viscoelastic material.

Assessment of natural radiation in contaminated automobile workshop soils

The presented study aims to identify and quantify the natural radionuclides activity concentrations on the top and sub-soils around mechanic workshops in Ojo and Ijegun, Lagos, Nigeria. Based on these measured radionuclides activity concentrations, radiological hazard indices are assessed. Twenty oil-contaminated soil samples were collected, and the levels of natural radionuclides activity are measured by applying gamma spectrometry The measured radionuclides with authoritative regularity are linked with the natural decay series of 238U (226Ra) and 232Th as well as the series of non-decay 40K. The obtained results show that the mean radionuclides activity concentrations in the collected oil-contaminated soils samples are 14 ± 4 Bq kg−1, 105 ± 55 Bq kg−1, and 90 ± 33 Bq kg−1, for 226Ra, 232Th, and 40K respectively. It was founded that the 226Ra radionuclide is the lower present in the oil-contaminated soils samples. The radiological assessments were evaluated in terms internal hazard index (0.54), and external hazard index (0.55) both of which are below the UNSCEAR-2000 standard limit. Consequently, the radiological assessment indicated that long-time exposure to those radionuclide's strength confuses integral hazards.

Complete β -decay patterns of Cs142,Ba142, and La142 determined using total absorption spectroscopy

Background: The β decays of fission products produced in nuclear fuel are important for nuclear energy applications and fundamental science of reactor antineutrinos. In particular, nuclear reactor safety is related to the decay modes of radioactive neutron-rich nuclei, primarily via the emission of γ rays, neutrons, and electrons. Additionally nuclear reactors are the most powerful man-made source of antineutrinos emitted during the β decay of fission products. These antineutrinos are used to inspect fundamental properties of leptons as well as informing reactor operation. However, the majority of data on complex decays of fission products collected in the evaluated nuclear data repositories like Evaluated Nuclear Structure Data File (ENSDF) and Evaluated Nuclear Data Files (ENDF) are based on low-efficiency and often incomplete measurements resulting in questionable reference reactor antineutrino flux predictions, see the analysis by [Nichols, J. Nucl. Sci. Technol. 52, 17 (2015)]. Various assessments like the one done under the auspices of the [Yoshida et al., Assessment of Fission Product Decay Data for Decay Heat Calculations: A report by the Working Party on International Evaluation Co-operation of the Nuclear Energy Agency Nuclear Science Committee (Nuclear Energy Agency, Organization for Economic Co-operation and Development, Paris, France, 2007), Vol. 25], as well as by [Sonzogni, Johnson, and McCutchan, Phys. Rev. C 91, 011301(R) (2015)] and [Dwyer and Langford, Phys. Rev. Lett. 114, 012502 (2015)], list the A=142 isobars with high cumulative fission yield among the important nuclei where data for reactor decay heat and/or antineutrino production should be verified and/or improved. Purpose: Our goal is to improve the quality of β-decay measurements and evaluate the impact of modified decay schemes on reactor decay heat and antineutrino energy spectra, for fission products along the A=142 isobaric chain. This work is an in depth follow-up on [Rasco et al., Phys. Rev. Lett. 117, 092501 (2016)]. which presented briefly the impact of the corrected decay scheme of 142Cs. Here, we extend the data to full isobaric decay chain including the daughter nuclei, 142Ba and 142La, and present more details on the 142Cs results. Method: The decays of neutron-rich isobars of mass A=142 produced by means of proton-induced fission of U238 were measured using the Modular Total Absorption Spectrometer (MTAS) array on-line at the mass separator and Tandem accelerator at Oak Ridge National Laboratory. Results: The β-decay schemes for 142Cs and 142La were modified with respect to the nuclear data repositories. A small β-delayed neutron branching ratio for 142Cs emitter was remeasured as 0.10−3+5 %. Improved precision on the measured half-lives is reported. Small corrections to the low-energy decay of 142Ba are made. The β-decay patterns for 142La and 142Cs are presented. The decay heat release and cross section for the detection of reactor antineutrinos are deduced and compared to earlier results. Conclusions: The β-feeding pattern for 142Cs having decay energy value Qβ of over 7 MeV was substantially modified with respect to the current ENSDF entry. Smaller changes were encountered for 142La, but since this A=142 isobar also has a large cumulative yield in fission, the changes influence both decay heat and the antineutrino spectra. The previously known β intensities for 142Ba decay (Qβ value of 2.2 MeV) were verified and slightly modified. Overall, increased decay heat values and lower flux of antineutrinos interacting with matter are presented.12 MoreReceived 13 October 2022Accepted 14 February 2023DOI:https://doi.org/10.1103/PhysRevC.107.034303©2023 American Physical SocietyPhysics Subject Headings (PhySH)Research AreasBeta decayFissionLifetimes & widthsNuclear reactorsNuclear structure & decaysProperties90 ≤ A ≤ 149TechniquesSpectrometers & spectroscopic techniquesNuclear Physics

α and 2α decay of nuclei in the region 94≤Z≤101 using the modified generalized liquid drop model

The \ensuremath{\alpha} decay and $2\ensuremath{\alpha}$ decay of various isotopes of Pu, Am, Cm, Bk, Cf, Es, Fm, and Md in the mass region $A=218$ to 273 are investigated using the modified generalized liquid drop model (MGLDM) and universal decay law. The comparison of experimental alpha decay half-lives with the predicted half-lives proves the consistency of our calculations. As a result we broadened our investigation to also include a study of double alpha decay of these isotopes. There is a considerable interest in performing research on double alpha decay, as seen by the proposal submitted at CERN to investigate the double alpha radioactivity of $^{224}\mathrm{Ra}$. In view of this, the decay half-lives of most probable $2\ensuremath{\alpha}$ emitters, calculated using MGLDM by employing different preformation factors, are presented which can be beneficial for upcoming experimental investigations on this topic. A peak or dip in \ensuremath{\alpha} and $2\ensuremath{\alpha}$ decay half-life is witnessed which indicates the stability of parent or daughter isotopes correspondingly. Minimum and maximum half-lives for decay are observed when the daughter and parent nuclei, respectively, contain a magic number of neutrons. From our study, 126 and 162 are found as magic/semimagic numbers. A linear plot is obtained while plotting ${\mathrm{log}}_{10}{T}_{1/2}$ of all the isotopes against $Z{Q}^{\ensuremath{-}1/2}$, which emphasizes that our estimations are reliable.

Theoretical predictions for α-decay chains and cluster radioactivity of superheavy nuclei with Z = 126

Theoretical predictions of [Formula: see text]-decay properties of several isotopes of the superheavy nucleus of [Formula: see text] [Formula: see text] and their consecutive [Formula: see text]-decay chains are presented. Based on the double-folding model, the [Formula: see text]–daughter interaction potential is constructed microscopically using a realistic M3Y–Paris nucleon–nucleon (NN) interaction. The [Formula: see text]-decay half-lives are computed for both spherical and deformed shapes of daughter nuclei within the density-dependent cluster model. The effect of deformation is found to decrease the [Formula: see text]-decay half-lives compared to spherical shapes. The calculated [Formula: see text]-decay half-lives are in satisfactory agreement with their counterparts using other theoretical methods. The prediction of the dominant decay mode for the isotopes [Formula: see text], which have not yet been experimentally synthesized, is presented through the competition between [Formula: see text]-decay and spontaneous fission. We have found that the isotopes [Formula: see text] survive fission and have relatively long half-lives which span the order [Formula: see text]–[Formula: see text]. Moreover, the correlation between the logarithm of the preformation probability deduced from the cluster formation model and the fragmentation potential for even–even [Formula: see text] isotopes is elucidated showing a negative linear relation. The feasibility of cluster emission from the superheavy isotope [Formula: see text] is investigated using different theoretical approaches. The predictions can provide useful guidance for future experimental researches.

Application of a new spectral deconvolution method for in vitro dosimetry in assessment of targeted alpha therapy.

The improvement of in vitro assessment of targeted alpha therapy (reproducibility, comparability of experiments…) requires precise evaluation of the dose delivered to the cells. To answer this need, a previous study proposed an innovative dosimetry method based on α-spectroscopy and a specific deconvolution process to recover the spatial distribution of 212 Pb isotopes inside in vitro culture wells. Nevertheless, although promising, the deconvolution method was time consuming and only tested for a simple isotope decay chain. The purpose of this work is to propose a new matrix deconvolution method of α spectra based on a constrained-non-negative-maximum-likelihood decomposition, both faster and offering a greater modelling flexibility, allowing to study independently the kinetics of each of the daughter nuclides of complex decay chains (illustrated here with 223 Ra) in in vitro culture wells. Firstly, the performance of the new method was fully evaluated through Monte Carlo simulations of in vitro irradiations. Different spatial distributions of 212 Pb and 223 Ra, the corresponding α spectra measured by a silicon detector and the doses delivered to the cells were simulated with Geant4. The deconvolution results were then compared to the simulation results. Secondly, measurements were carried out in culture wells without cells containing 15kBq of 212 Pb or 9.3kBq of 223 Ra, placed above silicon detectors recording α spectra in real time. The matrix deconvolution was then applied to determine the spatial and temporal distribution of all α-emitting daughters of studied isotopes. The matrix deconvolution was proved to recover the simulated distribution gradients, ensuring simulated doses within 3% for both tested radionuclides, with errors on dose normally distributed around the reference value (consequently not exhibiting any bias), even in the case of complex decay chains as 223 Ra. The experimental study of 212 Pb and 223 Ra showed highly inhomogeneous distributions and time evolution of the concentration gradients, consistent with the previous study. Furthermore, it highlighted the complex kinetics of 223 Ra with different distributions of its α-emitting daughters (219 Rn, 215 Po, 215 At, 211 Bi, 211 Po). This study validates a new deconvolution method, fast and flexible, that proved to be accurate and reliable. This method allowed to reveal the complexity of isotopes kinetics in in vitro experiments, especially with complex decay chains. Experimental dosimetry, necessary to improve reliability of in vitro studies in targeted alpha therapy, is demonstrated to be feasible with the proposed method.

Estimation of radioactive activity by gamma spectroscopy

Radioactive sources of isotopes 22Na, 137Cs, 60Co, 133Ba and decay chains of Th and U are analyzed by means of gamma spectroscopy. The instrument used, a cylindrical NaI(Tl) scintillator from Mirion Technologies (Canberra) with dimensions of 2 × 2, is characterized by its calibration and absolute efficiency. The peak energies of the gamma spectra obtained are identified and related to corresponding isotopes and matter-radiation interactions according to nuclear and atomic databases. From these data, spectroscopic methods are implemented to compute radioactive activities for each source.

Enhanced reductive degradation of chloramphenicol by sulfidated microscale zero-valent iron: Sulfur-induced mechanism, competitive kinetics, and new transformation pathway

Crystalline iron sulfide (FeSx, i.e., FeS or FeS2) minerals as sulfur sources were used to prepare the mechanochemically sulfidated microscale zero-valent iron ((FeSx+ZVI)bm). Metastable FeS and FeS2 precursors were generated via aqueous coprecipitation and applied to fabricate FeSx@ZVI samples. (FeSx+ZVI)bm and FeSx@ZVI exhibited better chloramphenicol (CAP) degradation than ZVI due to the increase in specific surface areas, the decrease of electrochemical impedance, the formation of galvanic cells, and sulfur-induced pitting and local acidity. (FeSx+ZVI)bm had better CAP removal capacity than FeSx@ZVI under different S/Fe molar ratios, initial pH, and oxygen conditions. At the same time, FeSx@ZVI showed better electron utilization under oxic conditions, related to their Fe0 and sulfur spatial distribution. Nitro reduction and dechlorination of CAP by (FeSx+ZVI)bm produced nitroso, azoxy, amine, and monodechlorination products, while dechlorination was not involved in the degradation process of CAP by FeSx@ZVI. A new transformation pathway of nitroso-CAP to amine-CAP mediated by azoxy products is proposed via coupling a chain decay multispecies model and DFT calculations. The larger competitive reaction rates among O2, CAP, and its degradation products was determined by their lower LUMO energy. The contribution of direct electron transfer to nitro reduction was greater than that of atomic hydrogen, but the opposite was true for dechlorination. FeSx@ZVI had a larger DET contribution than (FeSx+ZVI)bm, and FeS2 promoted the DET contribution better than FeS. Toxicity assessment indicated that the rapid transformation of nitroso and azoxy products was crucial for eliminating the biotoxicity of CAP.

Distribution of 222Rn decay products in a soil sample

Common practice analysis of environmental samples is usually performed by assuming radon and its decay products from the U-Ra natural radioactive series are uniformly spread within the entire sample volume. This uniform distribution is an assumption we intended to test using a volume sample. The results show that the actual distribution is not uniform and consequently needs to be treated as such for both measurement purposes and related simulations. Immediate applications include cross-disciplinary activities such as environmental studies, metrology applications and health (radiation hazard).