Hasil untuk "Radioactivity and radioactive substances"

Chavdar Dutsov, Timothy Hume, Maxim Pospelov et al.

We discuss a search for the electric dipole moment (EDM) of a light beta-radioactive ion using a compact ion trap by adapting the "frozen-spin" method. The measurement will be done on ions stripped of their valence electrons, thereby bypassing the significant Schiff screening that hinders the application of successful contemporary EDM searches using heavy neutral atoms and molecules to light nuclei. We identified $^8$Li as the most promising candidate for a proof-of-concept EDM search and we estimate that the current indirect proton EDM limit of a few $10^{-25} e\cdot$cm set by $^{199}$Hg measurements can be surpassed with a week of measurement time at existing facilities.

S. S. Silkin, L. D. Mikryukova

Colorectal cancer (colon, rectum, rectosigmoid and anus) is one of the most frequently registered cancer sites. Apart from main risk factors for the development of cancer of this localization (dietary disorders, obesity, alcohol and tobacco use, contact with certain chemicals), a number of authors have noted in their studies the effect of ionizing radiation. The objective of this study was to directly assess the excess relative risk of colorectal cancer in the population exposed to long-term chronic radiation mainly in the range of low-dose and low  dose  rates.  These  people  are  included  in  the  Southern  Urals  Population  Exposed  to  Radiation  Cohort. Materials and methods: the analytical cohort included 47,282 people, the follow-up period was 63 years (from 1956 to 2018), and the number of person years at risk was 1,292,930. The incidence catchment area includes five Chelyabinsk Oblast raions, the cities of Chelyabinsk and Ozersk. For the period from 1956 to 2018, 462 cases of colon cancer were registered in the follow-up territory. The colon dose was used as a reference dose. The mean absorbed dose was 69 mGy, the maximum dose – 1,824 mGy. The analysis was performed using Epicure statistical package programs by Poisson regression method with a simple parametric model of excess relative risk. Significance of the results was assessed by the maximum likelihood method with 95% probability. Results: In SUPER members, baseline colorectal cancer incidence rates were found to be dependent on such factors as sex (p<0.001), ethnicity (p=0.001), attained age (p<0.001), education (p<0.001), year of birth of cohort members (p<0.001), presence of cancer in first degree relatives (p=0.03). The risk analysis did not reveal statistically significant dose dependence of the excess relative risk of malignant neoplasms of the whole large intestine, as well as no significant dependence of the excess risk of malignant neoplasms of the colon and rectum. The influence of modifying factors on the magnitude of radiogenic risk was evaluated. Assessment of the excess relative risk of colorectal cancer in this cohort is carried out for the first time.

Justin Smith, Tracey Anderson, Viktoryia Kliaus

G. V. Arkhangelskaya

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G. Saxena, Mamta Aggarwal, D. Singh et al.

Effect of deformation on half-life of two-proton (2p) radioactivity is investigated across the periodic chart for nuclei with Z$<$82. 2p-decay half-lives are estimated by employing our newly proposed semi-empirical formula wherein the nuclear deformation has been incorporated in a phenomenological way. Robustness of the formula is demonstrated as it estimates the measured values quite accurately and, hence, reliably applied to predict the other possible 2p-emitters. For many proton rich nuclei for which experimental data on the decay energies are not available, we have used the theoretical values obtained from our calculations using the relativistic mean-field (RMF) approach. The uncertainties in the theoretical decay energy values are minimised by machine learning (ML) technique. Correlation of 2p-radioactivity with 2p-halo and deformation is probed. Our calculations show the phenomenon of shape coexistence in several 2p-emitters, wherein the prolate shape is found to be more predominant for the ground state.

V. P. Ramzaev, A. M. Biblin, V. S. Repin et al.

The article presents results of a study on the tritium content in surface and ground waters in the area of peaceful underground nuclear explosions of the “Dnepr” series. Low-yield thermonuclear explosions (1.8–2.1 kt of TNT equivalent) were carried out inside Mount Kuel’por (Khibiny Massif, Kola Peninsula, Murmansk Oblast, the Russian Federation) in 1972 and 1984. The purpose of the explosions was to crush the ore body (apatite minerals), followed by the extraction of the crushed rock to the ground surface. The main long-term problem generated by these explosions was the flow of tritium-contaminated groundwater onto the ground surface. The area where the explosions took place is actively visited by tourists. Water from local reservoirs, in particular from the Kuniyok River, is used by people for drinking. The purpose of this study was to assess the drinkability of the local waters in terms of activity concentration of tritium. To achieve this goal, 35 water samples were taken in 2019 from wells, boreholes, rivers, streams, lakes and other accessible environmental waterbodies. Activity concentration of tritium in the samples was determined using the Quantulus 1220 low-background liquid scintillation spectrometer. The activity concentration of tritium in the water samples was in a rather wide range: from less than 2 Bq/kg up to 1510 Bq/kg. The maximum value was up to three orders of magnitude higher than the regional background level of approximately 2 Bq/kg. At the same time, the maximum activity concentration was significantly lower compared to the intervention level for drinking water (7600 Bq/kg, according to Sanitary Norms and Rules of the Russian Federation). Based on the results of this study and data obtained by other researchers earlier, it became possible to assess the half-time for decrease of activity concentration of tritium in surface and ground waters in the period 2008–2019. The mean value (± standard error of the mean) of the effective half-time of tritium in water from the mine, the boreholes, and the Kuniyok River was estimated as 4.4 ± 0.2 year. The decrease in activity concentration of tritium in water depended more on ecological processes (dilution with “pure” water) than on physical decay of the radionuclide. In 2019, the estimated value of the effective dose due to ingestion of tritium in drinking water from the Kuniyok River was 0.17 μSv; this was negligible compared to the dose limit of 1 mSv per year for the public.

Ihor M. Kadenko, Nadiia V. Sakhno, Oleksandr M. Gorbachenko et al.

This paper deals with the formation of a bound dineutron in the outgoing channel of the $^{159}$Tb(n,$^2$n)$^{158g}$Tb nuclear reaction followed by assumed transformations of this reaction products $^{159g}$Tb and $^2$n. Such nuclear processes were studied in detail from the point of view of $^{160}$Tb / $^{160}$Dy / $^{160}$Ho amount of nuclei versus time dependence. Some signs of fusion process between heavier nuclei ($^{158}$Tb and/or $^{158}$Gd) and the deuteron, that is a bound dineutron decay product, were detected as unexpected increasing of 879.38 keV gamma-ray peak count rate due to $^{160}$Dy gamma-transitions. The mathematical model, including three systems of differential equations, was developed to describe the experimental data. This development requires a reasonable estimate of the half-life of a bound dineutron, which was found to be equal 5,877 s as an upper limit. We mathematically modeled the experimentally observed delayed in time buildup of the $^{160}$Tb radioactivity with a maximum at about 495 d since the neutron irradiation completion of the Tb sample, based on the similarity with the parent-daughter nuclei radioactivity decay and nuclear accumulation processes.

Guilherme Fernandes Nielsen, Nathanael Wagner Sales Morais, Nelson Batista de Lima

The uranium molybdenum (U-Mo) alloys have potential to be used as low enriched uranium nuclear fuel in research, test and power nuclear reactors. U-Mo alloy with composition between 7 and 10 wt% molybdenum shows excellent body centered cubic phase (γ phase) stabilization and presents a good nuclear fuel testing performance. Hot rolling is commonly utilized to produce parallel fuel plate where it promotes the cladding and the fuel alloy bonding. The mechanical deformation generates crystallographic preferential orientation, the texture, which influences the material properties. This work studied the texture evolution in hot rolled U-Mo alloys. The U7.4Mo and U9.5Mo alloys were melted in a vacuum induction furnace, homogenized at 1000°C for 5 h and then hot rolled at 650°C in three height reductions: 50, 65 and 80%. The crystalline phases and the texture were evaluated by X-ray diffraction (XRD). The as-cast and processed alloys microstructures were characterized by optical and electronic microscopies. The as-cast, homogenized and deformed alloys have γ phase. It was found microstructural differences between the U7.4Mo and U9.5Mo alloys. The homogenized treatment showed effective for microsegregation reduction and were not observed substantial grain size increasing. The deformed uranium molybdenum alloys presented α, γ, θ texture fibers. The intensity of these texture fibers changes with deformation step.

Carolina Nogueira da Silva, Clédola Cássia Oliveira de Tello

The use of nuclear energy, as well as all human activity, generates wastes and these need to receive suitable treatments so that they don’t expose a risk to the public and the environment. Currently there is a project in Brazil whose objective is the implementation of a national repository for the final storage of low and intermediate level waste. The disposal of the radioactive waste is based on the concept of multiple barriers, in which packed wastes are conditioned in concrete containers, which are then placed in modules, which are closed and covered by natural materials. In this work, Steel Fiber Reinforced Concrete (SFRC) was studied as a substitute for the concrete with conventional steel reinforcement in the production of containers. Compressive and tensile strength tests were performed, as well as characterization and evaluation of steel fibers. 48 specimens of concrete were prepared with two types of fibers (A and C) and tested. The best results were obtained with the addition of 1.5% vol. of type A fibers. Through the carbon and sulfur quantification test it was possible to conclude the steel used in the fibers’ manufacture was low carbon. It was also possible to verify, using the folding test, the material used served the parameters of quality. This research project was supported by the Centro de Desenvolvimento da Tecnologia Nuclear (CDTN), the Comissão Nacional de Energia Nuclear (CNEN) and the Fundação de Amparo à Pesquisa do Estado de Minas Gerais (FAPEMIG).

Diana Rodrigues Pina, Francielen Barreto Hortencio, José Carlos Souza Trindade Filho et al.

O objetivo deste trabalho foi desenvolver um indicador de dose eletrônico para a otimização da proteção radiológica no setor de Tomografia Computadorizada do Hospital das Clínicas de Botucatu. Foram estimadas doses efetivas utilizando o parâmetro DLP (do inglês Dose-Length Product). Estas doses efetivas foram comparadas com valores da literatura. O indicador de dose foi inserido no sistema de gestão hospitalar e contribuiu com o princípio da justificativa e proteção radiológica. Os valores de doses efetiva, para os protocolos da instituição são semelhantes aos referenciados na literatura, a maior diferença encontrada foi de 3,2%. O indicador de dose, carrega informações, sobre: a) dose acumulada pelo paciente em todos os exames de TC, b) O risco benefício de exames que envolvem radiação ionizante e c) Um termo que representa a ciência do solicitante quanto à dose acumulada e o risco-benefício. Este estudo vem corroborar com o princípio da justificação junto ao solicitante do exame. Essa ferramenta, contribui para orientação da equipe médica sobre a indicação excessiva de um exame considerado com alta taxa de dose. Essa metodologia pode ser implementada em qualquer serviço que realiza exames, envolvendo radiações ionizantes promovendo a melhor relação risco-benefício para o paciente custo-benefício para a instituição.

Yu. I. Stepkin, M. I. Chubirko, M. K. Kuzmichev et al.

The aim of the work was to characterize the radiation incidents that took place in the territory of the Voronezh region. Materials and methods. To prepare this article the stock data of the radiological laboratory of the Center for Hygiene and Epidemiology in the Voronezh Region for 2009-2018 was used. All measurements in the investigation of radiation incidents were carried out with the MKS-AT1117M dosimeter-radiometer which passed the state calibration. The equivalent dose rate of gamma radiation (μSv/h) was determined. Results. For the last 10 years, 8 radiation incidents were registered on the territory of the Voronezh region, which were related to domestic clocks - 4 (measurements according to citizens), the detection of orphan sources of ionizing findings - 2, scrap metal - 1 and a thermometer - 1 (during customs inspection). According to the classification of emergencies, the radiation incidents are local, i.e. do not go beyond the territory of the facility, according to the international scale of nuclear and radiological events, INES refer to the incident (anomalies) with the level 1 “minor problems with the safety of components, a radioactive source of low activity level”. All interactions in the investigation of radioactive incidents involving specialists from the radiological laboratory of the Center for Hygiene and Epidemiology in the Voronezh region with other services showed a good level of rapid response.

Wolfgang Hennig, Vincent Thomas, Shawn Hoover et al.

In systems with multiple radiation detectors, time synchronization of the data collected from different detectors is essential to reconstruct multi-detector events such as scattering and coincidences. In cases where the number of detectors exceeds the readout channels in a single data acquisition electronics module, multiple modules have to be synchronized, which is traditionally accomplished by distributing clocks and triggers via dedicated connections. To eliminate this added cabling complexity in the case of a new radioactive gas detection system prototype under development at the French Atomic Energy Commission, we implemented time synchronization between multiple XIA Pixie-Net detector readout modules through the existing Ethernet network, based on the IEEE 1588 precision time protocol. The detector system is dedicated to the measurement of radioactive gases at low activity and consists of eight large silicon pixels and two NaI(Tl) detectors, instrumented with a total of three 4-channel Pixie-Net modules. Detecting NaI(Tl)/silicon coincidences will make it possible to identify each radioisotope present in the sample. To allow these identifications at low activities, the Pixie-Net modules must be synchronized to a precision well below the targeted coincidence window of 500-1000 ns. Being equipped with an Ethernet PHY compatible with IEEE 1588 and synchronous Ethernet that outputs a locally generated but system-wide synchronized clock, the Pixie-Net can operate its analog to digital converters and digital processing circuitry with that clock and match time stamps for captured data across the three modules. Depending on the network configuration and synchronization method, the implementation is capable to achieve timing precisions between 300 ns and 200 ps.

Y. Zhu, S. H. Yue, Z. W. Ge et al.

Scintillating NaI(Tl) crystals are widely used in a large variety of experimental applications. However, for the use as Dark Matter (DM) detectors, such crystals demand a high level of radio-purity, not achievable by means of standard industrial techniques. One of the main difficulties comes from the presence of potassium that always accompanies sodium in alkali halides. On the other hand, the arguable DM detection by DAMA experiment using NaI(Tl) scintillating crystals requires a reliable verification able to either confirm the existence of DM or rule out the DAMA claim. Ultra-low radioactivity NaI(Tl) crystals, particularly with very low potassium content, are therefore indispensable to overcome the current stalemate in Dark Matter searches. Nonetheless, apart from DAMA-LIBRA experiments, to date, no other experiment has succeeded in building a detector from NaI(Tl) crystals with potassium content of ppb level. This work describes recent results in the preparation of ultra-radio-pure NaI(Tl) crystals using a modified Bridgman method. A double-walled platinum crucible technique has been designed and reliability tests show that 5 ppb of potassium in the NaI(Tl) crystals of 2 and 3 inches in diameter can be achieved starting from NaI powder with potassium content of the order of 10 ppb. The potassium excess is segregated in the tail-side of the as grown ingot where measured potassium concentration is above 20 ppb. The purifying effect of Bridgman growth for larger NaI(Tl) crystals is currently being tested. The work also reports on scintillation parameters of our NaI(Tl) crystals measured in a dedicated setup conceived for naked, hygroscopic crystals. The reproducible and reliable production of ultra-low radioactivity NaI(Tl) crystals reported in this work will hopefully spur the construction of new DM search experiments and, anyway, clarify the controversial DAMA-LIBRA results.

Larissa Pereira Farias, Isaac Antônio Luquetti dos Santos, Paulo Victor Rodrigues de Carvalho et al.

The Human Factors Engineering (HFE) program is an essential aspect for the design of nuclear installations. The overall aim of the HFE program is the improvement of the operational reliability and safety of plant operation. The HFE program main purpose is to ensure that human factor practices are incorporated into the plant design, emphasizing man-machine interface issues and design improvement of the nuclear reactor Control Centre. The Control Centre of nuclear reactor is a combination of control rooms, control suites and local control stations, which are functionally connected and located on the reactor site. The objective of this paper is to present a participatory design approach, including human factor issues, for the Control Centre of a nuclear research reactor used to produce radioisotopes and for nuclear research. The design approach is based on participatory design principles, using human factor standards, ergonomic guidelines, and the participation of a multidisciplinary team during all design phases. Using the information gathered, an initial sketch 3D of the Control Centre was developed.

Cássia K. L. Fonseca, Vivianne L. B. Souza, Bárbara E. S. Melo et al.

Parks and squares are inserted in urban environments, influenced by diverse anthropogenic sources of chemical elements. The Apipucos Maximiano Campos Park, located in the Apipucos neighborhood, in the city of Recife - PE aims to promote entertainment for the local population. The park was previously a green area containing scrap metal, which was removed to build the park, but it is still affected by vehicular emissions. Considering the possibility of negative health effects caused by local contaminants, the concentration of Cu, Fe, Mn, Ni, Pb and Zn in the soil of the Apipucos Maximiano Campos Park was determined by the Energy Dispersive X-Ray Fluorescence (EDXRF) technique. Fifteen soil samples were collected at three locations, under the vertical projection of tree crowns. Before the analysis, the samples were dried in an oven at 60 °C for 24 hours and pulverized. The concentrations of Cu, Fe, and Zn were characteristic of polluted soil; and the concentrations of Ni and Pb were higher than the reference values for Pernambuco. These contaminations probably derived from the previously deposited scrap metal. Such levels of contaminants demand public actions to avoid a negative effect on the health of the local population and to the environment.

David Hummel, Lucian Ivan

V. P. Ramzaev, I. G. Travnikova, L. N. Basalaeva et al.

The results of radiological investigations (in 2001-2002) conducted near sites of the underground nuclear explosions Crystal and Kraton-3 in the Republic of Sakha (Yakutia) are presented. The sum of the current effective internal doses from 137Cs and 90Sr (from consumption of natural products) and the external dose from 137Cs deposition was about 21 μSv y-1 for adult residents of the urban settlements Aihal and Udachny. Intake of 137Cs and 90Sr (originating from global fallout) with reindeer meat contributes ~87% to the internal dose determined. At present, the consequences of the underground nuclear explosions, conducted in the 1970s, have no influence on the technogenic exposure of the local population.

Tomohiro Oishi, Markus Kortelainen, Alessandro Pastore

Sensitivity of two-proton emitting decay to nuclear pairing correlation is discussed within a time-dependent three-body model. We focus on the $^6$Be nucleus assuming $α+ p + p$ configuration, and its decay process is described as a time-evolution of the three-body resonance state. For a proton-proton subsystem, a schematic density-dependent contact (SDDC) pairing model is employed. From the time-dependent calculation, we observed the exponential decay rule of a two-proton emission. It is shown that the density dependence does not play a major role in determining the decay width, which can be controlled only by the asymptotic strength of the pairing interaction. This asymptotic pairing sensitivity can be understood in terms of the dynamics of the wave function driven by the three-body Hamiltonian, by monitoring the time-dependent density distribution. With this simple SDDC pairing model, there remains an impossible trinity problem: it cannot simultaneously reproduce the empirical $Q$ value, decay width, and the nucleon-nucleon scattering length. This problem suggests that a further sophistication of the theoretical pairing model is necessary, utilizing the two-proton radioactivity data as the reference quantities.

Sra. Andrea Huhn, Sra Mara Ambrosina Oliveira Vargas

O Plano de Proteção Radiológica - PPR, citado pela Norma Regulamentadora 32, obriga a manter no local de trabalho e à disposição da inspeção do trabalhador o PPR, para que o mesmo esteja ciente de seu ambiente de trabalho e os danos que podem ser causados pelo mau uso da radiação ionizante. Objetivo: Discutir a interface entre o PPR e a reflexão ética. Método: Trata-se de estudo reflexivo. Discussão e Resultados: A Norma Regulamentadora 32 ressalta que o trabalhador que realiza atividades em áreas onde existam fontes de radiações ionizantes deve conhecer os riscos associados ao seu trabalho. No entanto, considera-se que nos setores de radiodiagnóstico hospitalares a equipe multiprofissional de saúde está exposta à radiação ionizante e nem sempre tem conhecimento dos maleficios causados pela mesma, assim acabam por realizar suas atividades desprotegidos. Concomitante, pesquisas recentes enfatizam a proteção radiológica e a preocupação com os perigos da radiação em seres humanos, mas pouco referem-se à legislação acerca da proteção radiológica. Neste contexto uma reflexão ética é necessária, buscando articular a responsabilidade ética profissional que implica no cuidado a proteção de si e do outro com as condições institucionais para que esta proteção se efetive.

A. Sieverding, L. Huther, K. Langanke et al.

We study the neutrino-induced production of nuclides in explosive supernova nucleosynthesis for progenitor stars with solar metallicity and initial main sequence masses between 15 M$_\odot$ and 40 M$_\odot$. We improve previous investigations i) by using a global set of partial differential cross sections for neutrino-induced charged- and neutral-current reactions on nuclei with charge numbers $Z < 76 $ and ii) by considering modern supernova neutrino spectra which have substantially lower average energies compared to those previously adopted in neutrino nucleosynthesis studies. We confirm the production of $^7$Li, $^{11}$B, $^{138}$La, and $^{180}$Ta by neutrino nucleosynthesis, albeit at slightly smaller abundances due to the changed neutrino spectra. We find that for stars with a mass smaller than 20 M$_\odot$, $^{19}$F is produced mainly by explosive nucleosynthesis while for higher mass stars it is produced by the $ν$ process. We also find that neutrino-induced reactions, either directly or indirectly by providing an enhanced abundance of light particles, noticeably contribute to the production of the radioactive nuclides $^{22}$Na and $^{26}$Al. Both nuclei are prime candidates for gamma-ray astronomy. Other prime targets, $^{44}$Ti and $^{60}$Fe, however, are insignificantly produced by neutrino-induced reactions. We also find a large increase in the production of the long-lived nuclei $^{92}$Nb and $^{98}$Tc due to charged-current neutrino capture.