Hasil untuk "Radioactivity and radioactive substances"

Hiroyuki Kintsu, Keita Kodama, Toshihiro Horiguchi

Aliaksandr Dvornik, Robert Finck, Christopher Rääf

Denise das Mercês Camarano, Emanuelle Costa e Silva, Jefferson José Vilela et al.

A global nuclear safety regime is in place and is being continuously improved. In this context, the aging management of research reactors is one of the requirements for licensing by the regulatory body. The IPR-R1 Triga reactor, located at the for Nuclear Technology Development Center (CDTN), is a nuclear reactor used primarily to research support. It has been in operation for over 60 years and its activities are expected to continue.  Thus, the aging management of components, structures and systems is one of the safety factors included in the Periodic Safety Report and encompasses several programs and activities, following the Specific Safety Guide SSG-10 (Aging Management for Research Reactors) of the International Atomic Energy Agency (IAEA). These programs are broad and transversal, serving as input for critical analysis of the Aging Management Plan (AMP), aimed at its continuous improvement. This paper aims to systematically present information related to the AMP of the CDTN IPR-R1 Triga reactor, such as visual inspection, reactor pool water quality control, maintenance, obsolescence control, investigation of operational parameters and all necessary controls to ensure that the safety margins required in the reactor design are maintained throughout its useful life.

Vanessa Silva Granadeiro Garcia, Flávio kiyoshi Tominaga, Nathalia Fonseca Boiani et al.

The presence of surfactants and other emerging pollutants in water bodies has become a major environmental concern in several places around the world, since these pollutants cause adverse problems in aquatic ecosystems and compromise public health, regarding the supply of good quality water. These pollutants often originate from various sources, including industrial activities, pharmaceuticals, and personal care products. A critical aspect of this issue is that many of these pollutants and their mixtures are difficult to degrade in biological treatment processes, requiring auxiliary treatments. Electron beam technology has been applied in various environmental matrices to degrade these pollutants, helping not only to increase degradability, as also to reduce the toxicity of these compounds. The present work aimed to evaluate LAS surfactant single and combined effects with emerging pollutants (caffeine and ciprofloxacin antibiotic) to aquatic organism Daphnia similis. It was also evaluated the electron beam (EB) treatment for reducing toxicity of single compounds. The organisms were exposed to samples (non-irradiated and irradiated LAS and mixtures) for 48 hours and the observed effect was immobility. The toxicity was evaluated through EC50 (median effective concentration) calculations. The EC50 values showed a high toxicity level for surfactant LAS with EC50s below 9%. Caffeine and Ciprofloxacin EC50 data were higher than 20%. EC50% values ​​of the mixtures were close to the values ​​of the isolated compounds.  After the EB treatment (5 kGy) about 70% acute toxicity reduction was obtained for LAS surfactant. The combined presence of surfactants and emerging pollutants in aquatic matrices requires a comprehensive approach to monitoring and mitigating their impacts to protect aquatic ecosystems and human health.

Tatiane Rocha Pereira, Maria Angélica Vergara Wasserman, Michele Maria da Silva et al.

Graphene Quantum Dots (GQDs) represent a new class of nanomaterials that, due to their optical, electronic, and chemical properties, have gained attention for various applications in industry, health, and the environment. However, the understanding of their dynamics and behavior in different environmental compartments is still in its early stages, requiring further research, although recent studies have already highlighted their potential for the remediation of polluted environments. While knowledge about the behavior of radionuclides in soils has advanced, research on semi-arid soils remains limited, both nationally and internationally. To address some of these gaps, this study determined the distribution coefficient (Kd) values for 137Cs and 60Co in some soils from the Brazilian semiarid region (Latossolo and Argissolo, respectively Ferralsol and Acrisol in the FAO classification), considering variations in pH and the presence or absence of GQDs. The obtained Kd values for 137Cs and 60Co showed different responses of the soils to the radionuclides, pH variations, and/or the presence of GQDs. The geometric mean of 137Cs Kd values to the studied soils were 510 mL g-1 in the Acrisol and 1730 mL g-1 in the Ferralsol, differing from the generic values found in the literature, which are often used as standard in radioecological models due to the lack of regional data. The geometric mean for 60Co Kd values were 791 mL g-1 in the Acrisol and 395 mL g-1 in the Ferralsol, also diverging from the generic literature values. These results highlight the responses of certain Brazilian soils to the introduction of exogenous materials and the need to obtain specific Kd values for semi-arid soils, aiming to improve environmental protection strategies.

Clarysson Alberto Mello da silva, Paola Machado de Almeida, Claubia Claubia Pereira

The present work simulates the European Lead Cooled Training Reactor (ELECTRA), focusing on studying the neutronic parameters of a small fast nuclear reactor. The goal is to evaluate the possibility of incinerating minor actinides and the potential for energy production from 238U. The simulations consider the following scenarios: depleted uranium mixed with the reprocessed fuel, and individual fuel rods containing only depleted uranium positioned at different locations within the reactor core. The results show that the use of reprocessed fuels could contribute to the reduction of minor actinides, while the use of depleted uranium reduces reactor criticality by acting as a neutron absorber. Most uranium nuclides do not undergo fission during burnup, which increases their isotopic concentration.

Yin Fan, Sibo Wang, Xiao-Hua Li et al.

We present the first microscopic description of proton radioactivity in $^{149}$Lu, the most oblate deformed proton emitter known, using a deformed microscopic optical potential derived from $ab\ initio$ nuclear matter calculations. We predict a novel angular-dependent phenomenon unprecedented in spherical proton emitters: the disappearance of classically allowed regions at small polar angles $(θ\leq 21^\circ)$. Combining the Wentzel-Kramers-Brillouin penetration probabilities and the assault frequency of the emitted proton estimated with a new harmonic-oscillator-inspired scheme, our framework yields a half-life $T_{1/2}=467^{+143}_{-108}$ ns for $^{149}$Lu, in excellent agreement within uncertainties with the experimental value $450^{+170}_{-100}$ ns. Deformation analysis rigorously excludes configurations with $|β_2|\geq 0.32$. Extensions to $^{150, 151}$Lu and their isomers also achieve excellent agreement with experimental half-life data. We further predict $^{148}$Lu as another highly oblate $(β_2 = -0.166)$ proton emitter with a half-life of 4.42 ns. This work validates deformed microscopic optical potentials as a robust predictive tool for drip-line proton emitters and provides quantitative evidence for deformation effects in exotic decays.

Anirudh Patel, Brian D. Metzger, Jared A. Goldberg et al.

We present nucleosynthesis and light-curve predictions for a new site of the rapid neutron capture process ($r$-process) from magnetar giant flares (GFs). Motivated by observations indicating baryon ejecta from GFs, Cehula et al. (2024) proposed mass ejection occurs after a shock is driven into the magnetar crust during the GF. We confirm using nuclear reaction network calculations that these ejecta synthesize moderate yields of third-peak $r$-process nuclei and more substantial yields of lighter $r$-nuclei, while leaving a sizable abundance of free neutrons in the outermost fastest expanding ejecta layers. The final $r$-process mass fraction and distribution are sensitive to the relative efficiencies of $α$-capture and $n$-capture freeze-outs. We use our nucleosynthesis output in a semi-analytic model to predict the light curves of novae breves, the transients following GFs powered by radioactive decay. For a baryonic ejecta mass similar to that inferred of the 2004 Galactic GF from SGR 1806-20, we predict a peak UV/optical luminosity of $\sim 10^{39}$-$10^{40}\,\rm erg\,s^{-1}$ at $\sim 10$-$15$ minutes, rendering such events potentially detectable following a gamma-ray trigger by wide-field transient monitors such as ULTRASAT/UVEX to several Mpc. The peak luminosity and timescale of the transient increase with the GF strength due to the larger ejecta mass. Although GFs likely contribute 1-10% of the total Galactic $r$-process budget, their short delay-times relative to star-formation make them an attractive source to enrich the earliest generations of stars.

Golrokh Nouri, Paul Tupper

Many drugs used therapeutically or recreationally induce tolerance: the effect of the substance decreases with repeated use. This phenomenon may reduce the efficacy of the substance unless dosage is increased beyond what is healthy for the individual. Restoring the effect of the substance can often be obtained by taking a break from consumption. We propose designing dosing schedules that maximize the desired effect of the substance with a given total consumption, while factoring in the effect of tolerance. We provide a simple mathematical model of response to consumption and tolerance that can be fit from data on substance administration and response. Using this model with given parameters, we determine optimal consumption schedules to maximize a given objective. We illustrate with the example of caffeine, where we provide a schedule of consumption for a user who values the effects of caffeine on all days but needs extra alertness on some days of the week.

Bruno Fievet, Claire Voiseux, Catherine Leblanc et al.

Rodrigo Modesto Gadelha Gontijo, Andréa Vidal Ferreira, Daniele Faria et al.

This study evaluated Image Quality (IQ) parameters and spatial resolution (SR) of Triumph® LabPET systems installed in three different Brazilian preclinical molecular imaging centers. A comprehensive evaluation of the PET scanner intrinsic parameters is important to optimize the acquired images, providing more reliable qualitative and quantitative analyses. Experiments were carried out at the centers: C1 - Molecular Imaging Laboratory of the CDTN/CNEN; C2 - Laboratory of Nuclear Medicine of HCFMUSP; C3 - Preclinical Research Center of the Brain Institute at PUC-RS. IQ phantom PET images were acquired as recommended in NEMA NU 4-2008 standard. Image reconstructions were performed in each system using the same reconstruction protocol. Data was processed using PMOD® software. The IQ parameters: (i) uniformity, (ii) spill-over ratio (SOR) and (iii) recovery coefficients (RC) were evaluated and compared. For Uniformity test, the percentage standard deviations of mean activity concentration were 7.8%; 7.3% and 6.4% for Centers 1, 2 and 3 respectively. Cold chambers RSO values in the systems 1, 2 and 3 were respectively 0.16, 0.19 and 0.21 for water; 0.26; 0.28 and 0.30 for air. The RC’s for rod diameters from 1 to 5 mm ranged from 0.08 to 0.91 for the three centers. Results revealed that the three PET systems have appropriate quality parameters for pre-clinical studies, presenting values compatible with international standards. This study was able to reveals the performance of preclinical PET system of different Brazilian imaging centers and may support the standardization of a National Quality Control Program for Small Animal PET scanners.

S. Yu. Bazhin, E. N. Shleenkova, V. Yu. Bogatyreva

The review presents description of the work and the main provisions on the working conditions for nondestructive testing operators from the standpoint of the system for ensuring radiation safety and radiation control. The values of the average annual effective doses of flaw detectorists in the Russian Federation and abroad are indicated. Official sources of information on doses in the Russian Federation and in the world, obtained from the results of individual dosimetric monitoring, were selected for presentation. The data of our own measurements were not included in this review. The difference in the name of the specialty of the studied group of personnel in Russian and English and the difference in the processing of primary measuring information in domestic and foreign sources of information are taken into account. The relevance of the need to resolve the issues of radiation safety and radiation monitoring of personnel involved in nondestructive testing is demonstrated, due to the fact that in the Russian Federation there are regulatory and methodological documents affecting the organization and conduct of individual dosimetric monitoring of personnel in the medical field and the nuclear industry, but they do not include personnel conducting nondestructive testing. Therefore, individual dosimetric control for nondestructive testing operators is carried out by accredited laboratories in accordance with the provisions of Methodical guidelines 2.6.1.3015-12.“Organization and management of individual dosimetry of medical staff”, i.e. without taking into account the exposure scenarios for personnel involved in nondestructive testing and the specifics of it work. The doses estimated in this way are included in the regional and federal databanks of personnel exposure doses. When entering dose values into data banks, there is no division of personnel into the personnel performing nondestructive testing in stationary and nonstationary conditions, therefore, the doses of personnel performing various types of nondestructive testing are averaged.

Rafael Guimarães Malanga, Thatiane Alves Pianoschi, Cassiana Viccari et al.

The interaction of radiation with biological tissues may cause some damage. To quantify it, studying cells in vitro is one methodology for analyzing dose deposition in biological tissues because once exposed to radiation, different methods can quantify the biological damage. However, biological tissue culture exposure forms mostly employ high-energy beams (MeV). Thus, this study aims to characterize the radiation field from X-ray equipment using thermoluminescent dosimeters (TLD), to establish an in vitro irradiation protocol of breast cancer and glioblastoma cells for low energies. First, the central axis alignment test was performed to ensure the equipment followed the Normativa IN 90. Then the variation of radiation intensity was analyzed for a 5 x 5 cm² field at distances between 30 and 90 cm from the focal point to the detector. Subsequently, TLD immersed in breast cancer and glioblastoma cellular media were irradiated in a 106 kV and 71 mAs beam to evaluate the dose in cellular media. Simulations were performed with the PENELOPE code to compare with experimental results. The result of the central axis alignment showed that the equipment complies with the current Normativa. The dose distributions for the evaluated distances were more homogeneous for the 40 cm distance, with a standard deviation of 1.7% and 0.9% of the distributions obtained with the TLD and simulation, respectively. Thus, the irradiation field for low energy beams was characterized for a 5 x 5 cm² field for 106 kV and 71 mAs beams at a DFS of 40 cm.

Kaia Newman, Madeline Endres, Brittany Johnson et al.

Psychoactive substances, which influence the brain to alter perceptions and moods, have the potential to have positive and negative effects on critical software engineering tasks. They are widely used in software, but that use is not well understood. We present the results of the first qualitative investigation of the experiences of, and challenges faced by, psychoactive substance users in professional software communities. We conduct a thematic analysis of hour-long interviews with 26 professional programmers who use psychoactive substances at work. Our results provide insight into individual motivations and impacts, including mental health and the relationships between various substances and productivity. Our findings elaborate on socialization effects, including soft skills, stigma, and remote work. The analysis also highlights implications for organizational policy, including positive and negative impacts on recruitment and retention. By exploring individual usage motivations, social and cultural ramifications, and organizational policy, we demonstrate how substance use can permeate all levels of software development.

Miguta Faustine Ngulimi, Jerome Mbwilo Mwimanzi, Siwidhani Thomas Ndovi

Occupational radiation doses in diagnostic radiography Centres of the Lake Zone Regions of Tanzania were measured and analyzed. Thermoluminiscent Dosimeters (TLDs) were distributed to 17 radiation workers from 8 selected medical centres over a period of three (3) months. The estimated ambient doses in the Centers was measured by using a calibrated survey meter RAM DA-3-2000 of TAEC under SSDL Laboratory. The individual dose recorded ranged from 0.09 to 1.12 mSv which were all below the ICRP limit of 5mSv for 3 months. The radiation dose (ambient) recorded at 1 m from the control lead glass window ranged from 2.15 µSv/h to 7.27 µSv/h. The ambient doses were compared to the limit of 7.5 µSv/h set by ICRP. Higher values of ambient doses and indivudual doses were observed in some centres which entails improper radiation safety and protection measures in radiation cantres. But with the use  of protective gears, radiation workers receive lower doses hence abide with ALARA principle.

E. C. Amato, A. Anelli, M. Barbieri et al.

We implemented a didactic experiment to study the angular correlation between the two gamma rays emitted in typical $^{60}$Co radioactive decays. We used two NaI(Tl) scintillators, already available in our laboratory, and a low-activity $^{60}$Co source. The detectors were mounted on two rails, with the source at their center. The first rail was fixed, while the second could be rotated around the source. We performed several measurements by changing the angle between the two scintillators in the range from $90^\circ$ to $180^\circ$. Dedicated background runs were also performed, removing the source from the experimental setup. We found that the signal rate increases with the angular separation between the two scintillators, with small discrepancies from the theoretical expectations.

N. Erkaev, M. Scherf, O. Herbort et al.

The initial abundance of radioactive heat producing isotopes in the interior of a terrestrial planet are important drivers of its thermal evolution and the related tectonics and possible evolution to an Earth-like habitat. The moderately volatile element K can be outgassed from a magma ocean into H$_2$-dominated primordial atmospheres of protoplanets with assumed masses between 0.55-1.0$ M_{\rm Earth}$ at the time when the gas disk evaporated. We estimate this outgassing and let these planets grow through impacts of depleted and non-depleted material that resembles the same $^{40}$K abundance of average carbonaceous chondrites until the growing protoplanets reach 1.0 $M_{\rm Earth}$. We examine different atmospheric compositions and, as a function of pressure and temperature, calculate the proportion of K by Gibbs Free Energy minimisation using the GGChem code. We find that for H$_2$-envelopes and for magma ocean surface temperatures that are $\ge$ 2500 K, no K condensates are thermally stable, so that outgassed $^{40}$K can populate the atmosphere to a great extent. However, due to magma ocean turn-over time and the limited diffusion of $^{40}$K into the upper atmosphere, from the entire $^{40}$K in the magma ocean only a fraction may be available for escaping into space. The escape rates of the primordial atmospheres and the dragged $^{40}$K are further simulated for different stellar EUV-activities with a multispecies hydrodynamic upper atmosphere evolution model. Our results lead to different abundances of heat producing elements within the fully grown planets which may give rise to different thermal and tectonic histories of terrestrial planets and their habitability conditions.

Thomas V. Lawson, Marco Pignatari, Richard J. Stancliffe et al.

Short-lived radioactive isotopes (SLRs) with half-lives between 0.1 to 100 Myr can be used to probe the origin of the Solar System. In this work, we examine the core-collapse supernovae production of the 15 SLRs produced: $^{26}$Al, $^{36}$Cl, $^{41}$Ca, $^{53}$Mn, $^{60}$Fe, $^{92}$Nb, $^{97}$Tc, $^{98}$Tc, $^{107}$Pd, $^{126}$Sn, $^{129}$I, $^{135}$Cs, $^{146}$Sm, $^{182}$Hf, and $^{205}$Pb. We probe the impact of the uncertainties of the core-collapse explosion mechanism by examining a collection of 62 core-collapse models with initial masses of 15, 20, and 25M$_{\odot}$, explosion energies between 3.4$\times$10$^{50}$ and 1.8$\times$10$^{52}$ ergs and compact remnant masses between 1.5M$_{\odot}$and 4.89M$_{\odot}$. We identify the impact of both explosion energy and remnant mass on the final yields of the SLRs. Isotopes produced within the innermost regions of the star, such as $^{92}$Nb and $^{97}$Tc, are the most affected by the remnant mass, $^{92}$Nb varying by five orders of magnitude. Isotopes synthesised primarily in explosive C-burning and explosive He-burning, such as $^{60}$Fe, are most affected by explosion energies. $^{60}$Fe increases by two orders of magnitude from the lowest to the highest explosion energy in the 15M$_{\odot}$model. The final yield of each examined SLR is used to compare to literature models.

Meng-Hua Chen, Rui-Chong Hu, En-Wei Liang

AAssociation of GW170817/GRB170817A/AT2017gfo provides the first direct evidence for neutron star mergers as significant sources of $r$-process nucleosynthesis. A gamma-ray transient (GRT) would be powered by the radioactive decay of the freshly-synthesized $r$-process elements. By analyzing the composition and gamma-ray opacity of the kilonova ejecta in details, we calculate the lightcurve and spectrum of the GRT for a range of spherically symmetric merger ejecta models with mass $M_{\rm ej}=0.001 \sim 0.05M_{\odot}$ and expansion velocity $v_{\rm ej}= 0.1\sim 0.4c$. It is found that the peak of the GRT lightcurve depends on $M_{\rm ej}$ and $v_{\rm ej}$ as $t_{\rm pk} \approx 0.5~{\rm days} ~ (M_{\rm ej}/0.01M_{\odot})^{1/2}(v_{\rm ej}/0.1c)^{-1}$ and $L_{\rm pk} \approx 2.0\times10^{41} ~{\rm erg~s} ^{-1} (M_{\rm ej}/0.01M_{\odot})^{1/2}(v_{\rm ej}/0.1c)$. Most radiating photons are in the $100-3000$ keV band and the spectrum peaks at about 800~keV for different nuclear physics inputs. The line features are blurred out by the Doppler broadening effect. Adopting the ejecta parameters reported in literature, we examine the detection probability of the possible GRT associated with AT2017gfo. We show that the GRT cannot be convincingly detected neither with current nor with the proposed missions in the MeV band, such as ETCC and AMEGO. The low gamma-ray flux, together with the extremely low event rate at local universe, makes a discovery of GRTs a great challenge.

Torsten Schmiermund