Abstract: The characterization of a dosimetry system based on a commercial PIN photodiode as a routine dosimeter in a 60Co industrial facility is reported. The main parameters of the dose rate response (repeatability, reproducibility, and angular dependence) and the dose response (dependence on both dose rate and accumulated dose) are investigated. The results obtained, within a dose rate range of 3.7–52.8 Gy/h and doses up to 200 Gy, fully adhere to the standard protocols established for radiation processing dosimetry. The diode performance as a routine dosimeter is validated by the good overall agreement with radiochromic films and alanine dosimetry.

Palavras-Chave: photodiodes; thin films; gamma radiation; dosimetry; silicon diodes

GONCALVES, JOSEMARY A.C.; MANGIAROTTI, ALESSIO; BUENO, CARMEN C. Characterization of a thin photodiode as a routine dosimeter for low-dose radiation processing applications. Radiation Physics and Chemistry, v. 198, p. 1-7, 2022. DOI: 10.1016/j.radphyschem.2022.110200. Disponível em: http://repositorio.ipen.br/handle/123456789/33206. Acesso em: $DATA.

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Abstract: A channel box installation in the IEA-R1 research reactor core was numerically investigated to increase fluid flow in fuel assemblies (FAs) and side water channels (SWCs) between FAs by minimizing bypasses in specific regions of the reactor core, which is expected to reduce temperatures and oxidation effects in lateral fuel plates (LFPs). To achieve this objective, an isothermal three-dimensional computational fluid dynamics model was created using Ansys CFX to analyze fluid flow distribution in the Brazilian IEA-R1 research reactor core. All regions of the core and realistic boundary conditions were considered, and a detailed mesh convergence study is presented. Results comparing both scenarios are presented in the percentage of use of the primary circuit pump. It is indicated that 21.4% of fluid bypass to unnecessary regions can be avoided with the channel box installation, which leads to the total mass flow from the primary circuit for all FAs increasing from 68.9% (without a channel box) to 77.6% (with a channel box). For the SWCs, responsible for cooling LFPs, an increment from 9.7% to 22.4%, avoiding all nondesired cross three-dimensional effects, was observed, resulting in a more homogeneous fluid flow and vertical velocities. It was concluded that the installation of a channel box numerically indicates an expressive mass flow increase and homogeneous fluid flow distribution for flow dynamics in relevant regions. This gives greater confidence to believe that lower temperatures, and consequently oxidation effects in LFPs, can be expected with a channel box installation.

Palavras-Chave: computer codes; fluid mechanics; reactor cores; distribution; fluid flow

SCURO, N.L.; ANGELO, G.; ANGELO, E.; PIRO, M.H.A.; UMBEHAUN, P.E.; TORRES, W.M.; ANDRADE, D.A. Computational fluid dynamics analysis of an open-pool nuclear research reactor core for fluid flow optimization using a channel box. Nuclear Science and Engineering, v. 197, n. 6, p. 1100-1116, 2023. DOI: 10.1080/00295639.2022.2142437. Disponível em: http://repositorio.ipen.br/handle/123456789/34060. Acesso em: $DATA.

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Abstract: The aim of this work was to investigate the effect of galvanic coupling between stainless steel AISI 316 L abutment type Morse taper and implant made of ASTM F1108–14 Ti-6Al-4V alloy. The assembly of the two alloys was carried out using mechanical imbrication by means of successive strikes at 0.05 J force onto the abutment inserted in the implant along the centerline. Corrosion attack at the interface of the alloys was evaluated according to the number of strikes used for joining the parts. Corrosion resistance was evaluated for the samples by open circuit potential measurements as function of time and scanning vibrating electrode technique (SVET) and scanning ion selective electrode technique (SIET) in phosphate buffer solution with pH adjusted to 3.0, and into which hydrogen peroxide was added to simulate tissue inflammatory conditions. Samples were evaluated at the cross and longitudinal sections. Results indicated that the number of strikes used in assembling affected corrosion susceptibility. The lowest amount of corrosion products was associated to the highest number of strikes used. The corrosion resistance was related to the characteristics of the crevice between the implant and the abutment.

Palavras-Chave: dentistry; implants; titanium alloys; stainless steel-316l; morse potential; corrosion

BERBEL, LARISSA O.; VIVEIROS, BARBARA V.G. de; MICELLI, ANA L.P.; NIGRO, FREDERICO; ROSSI, JESUALDO L.; COSTA, ISOLDA. Corrosion mechanism of Ti-6Al-4V morse taper dental implants connected to 316 L stainless steel prosthetic abutment. Materials Today Communications, v. 33, p. 1-13, 2022. DOI: 10.1016/j.mtcomm.2022.104583. Disponível em: http://repositorio.ipen.br/handle/123456789/33446. Acesso em: $DATA.

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Abstract: Over the last decades there was an increasing interest in using magnesium alloys for medical applications due to their biodegradability in the human body, providing a temporary mechanical support and corroding completely after the tissue healing. Although magnesium is a non-toxic element, it is of great importance to evaluate the element concentration, as well as the impurities present in both, pure magnesium and magnesium alloys, as the AZ31. The purpose of this study was to analyze the element composition of these materials using the method of neutron activation analysis (NAA). Standard Reference Materials (SRMs) acquired from National Institute of Standards and Technology (NIST) were analyzed for analytical quality control. Short and long term irradiations were carried out at the IEA-R1 nuclear research reactor and gamma-ray activities induced to the samples and element standard were measured using HPGe detector coupled to a Digital Spectrum Analyzer. The radioisotopes were identified by gamma ray energies and half-life. Concentrations of the elements As, Cr, Cd, Co, Fe, In, La, Mg, Mn, Mo, Na, Sb, V, W and Zn were determined in pure magnesium sample and the Al, As, La, Mg, Mn, Na, Sb and Zn in the AZ31 alloy, calculated by comparative method. The SRMs were analyzed by applying the same experimental conditions used for magnesium-based materials and their results presented good accuracy and precision. Thus, from the measurements obtained in this study it can be concluded that NAA is a suitable method for element determinations in magnesium-based materials providing reliable results.

Palavras-Chave: biological materials; gamma radiation; high-purity ge detectors; impurities; magnesium alloys; quality control

SILVA, C.A.J.; BRAGUIN, L.N.M.; ROSSI, J.L.; COSTA, I.; SAIKI, M. Determination of chemical elements in magnesium-based materials by neutron activation analysis. Brazilian Journal of Radiation Sciences, v. 9, n. 1A, p. 1-16, 2021. DOI: 10.15392/bjrs.v9i1A.1584. Disponível em: http://repositorio.ipen.br/handle/123456789/32149. Acesso em: $DATA.

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Abstract: Nd3+-doped GeO2-PbO glass with silver (Ag) nanoparticles (NPs) are produced with double line waveguides through fs laser processing for photonic applications. A Ti:sapphire fs laser at 800 nm was used to write the waveguides directly into the glass 0.7 mm beneath the surface. This platform is based on pairs of parallel lines with spacing of 10 µm, each pair being formed by two identical written lines but in two different configurations of 4 or 8 separately processed lines, which are coincident. The results of optical microscopy, absorbance measurements, refractive index change, beam quality factor (at 632 and 1064 nm), photoluminescence, propagation losses, and relative gain at 1064 nm are presented. The structural changes in the glass due to the presence of Ag NPs were investigated by Raman spectroscopy. At 632 and 1064 nm, x,y-symmetrical guiding was observed, and for both kinds of overlapping pulses, a refractive index alteration of 10−3 was found in both directions. Photoluminescence growth of ~47% at 1064 nm was observed due to the plasmonic effect of Ag NPs. In dual waveguides containing Ag NPs, the relative gain obtained increased by 40% and 30% for four and eight overlapping lines, respectively, at 600 mW of 808 nm pump power, when compared to waveguides without those metallic NPs. We highlight the resultant positive internal gains of 5.11 and 7.12 dB/cm that showed a growth of ~40% and ~30%, respectively, with respect to the samples without Ag NPs. The increase in photoluminescence and relative gain were related to the local field growth produced by Ag NPs. The present results show that the addition of Ag NPs impacts positively on the optical performance at 1064 nm of double line waveguides processed by fs laser writing in Nd3+-doped GeO2-PbO glass, opening news perspectives for photonics.

Palavras-Chave: lasers; pulses; germanates; waveguides; optical equipment; silver; nanoparticles

BORDON, CAMILA D. da S.; DIPOLD, JESSICA; WETTER, NIKLAUS U.; ROSSI, WAGNER de; FREITAS, ANDERSON Z.; KASSAB, LUCIANA R.P. Effect of silver nanoparticles on the optical properties of double line waveguides written by fs laser in Nd3+-doped GeO2-PbO glasses. Nanomaterials, v. 13, n. 4, p. 1-13, 2023. DOI: 10.3390/nano13040743. Disponível em: http://repositorio.ipen.br/handle/123456789/33995. Acesso em: $DATA.

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Abstract: Lanthanide-based beta-tricalcium phosphate (β-TCP) upconversion nanoparticles are exploited as a non-viral vector for imaging guided-gene therapy by virtue of their unique optical properties and multi-modality imaging ability, high transfection efficiency, high biocompatibility, dispersibility, simplicity of synthesis and surface modification. Ytterbium and thulium-doped β-TCP nanoparticles (βTCPYbTm) are synthesized via co-precipitation method, coated with polyethylenimine (PEI) and functionalized with a nuclear-targeting peptide (TAT). Further, in vitro studies revealed that the nanotheranostic carriers are able to transfect cells with the plasmid eGFP at a high efficiency, with approximately 60% of total cells producing the fluorescent green protein. The optimized protocol developed comprises the most efficient βTCPYbTm/PEI configuration, the amount and the order of assembly of βTCPYbTm:PEI, TAT, plasmid DNA and the culturing conditions. With having excellent dispersibility and high chemical affinity toward nucleic acid, calcium ions released from βTCPYbTm:PEI nanoparticles can participate in delivering nucleic acids and other therapeutic molecules, overcoming the nuclear barriers and improving the transfection efficacy. Equally important, the feasibility of the upconversion multifunctional nanovector to serve as an effective contrast agent for imaging modality, capable of converting low-energy light to higher-energy photons via a multi-photons mechanism, endowing greater unique luminescent properties, was successfully demonstrated.

Palavras-Chave: gene therapy; polyethylenes; nanoparticles; calcium phosphates

SILVA, FLAVIA R.O.; LIMA, NELSON B.; BELLINI, MARIA H.; TEIXEIRA, LUIZ F.S.; DU, ERIC Y.; JAMSHIDI, NILOUFAR; GOODING, JUSTIN; MARTIN, ADAM D.; MACMILLAN, ALEXANDER; MARQUIS, CHRISTOPHER P.; THORDARSON, PALL. Lanthanide-based β-tricalcium phosphate upconversion nanoparticles as an effective theranostic nonviral vectors for image-guided gene therapy. Nanotheranostics, v. 6, n. 3, p. 306-321, 2022. DOI: 10.7150/ntno.68789. Disponível em: http://repositorio.ipen.br/handle/123456789/33017. Acesso em: $DATA.

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Abstract: In this work, the insensitive layer thickness of a PIN photodiode (SFH206K - Osram) has been measured by varying the incident angle of a collimated monoenergetic alpha particle beam. This technique is based on variations in the path lengths of alpha particles through the insensitive layer and the correspondent energy losses when they impinge on a diode surface at different angles. Therefore, the pulse heights of these alpha particles, closely related to the energies deposited in the active volume of the diode, also depend on their incident angle. So, the difference between the pulse height of alpha particles perpendicularly incident on the diode surface and at any incident angle enables the insensitive layer thickness to be assessed. The result obtained (711  23) nm, less than 1% of the intrinsic layer thickness, besides validating the employed method, demonstrates that the investigated diode is suitable for high resolution charged particle spectrometry.

PASCOALINO, K.; CAMARGO, F.; GONCALVES, J.A.C.; BUENO, C.C. Measurement of the insensitive surface layer thickness of a PIN photodiode based on alpha-particle spectrometry. Brazilian Journal of Radiation Sciences, v. 10, n. 3B, p. 1-9, 2022. DOI: 10.15392/2319-0612.2022.1789. Disponível em: http://repositorio.ipen.br/handle/123456789/33500. Acesso em: $DATA.

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Abstract: The dosimetric response of silicon diodes produced with distinct engineering technologies, Magnetic Czochralski (MCz), and standard Float Zone (Fz), has been investigated, aiming at their use for online dosimeters in gamma radiation processing applications. The p+-n-n+ junction diodes, 300 µm thick with an active area of 25 mm2, are operated as online radiation dosimeters in the short-circuit current mode. In this case, the key dosimetric quantity is the dose rate, which is correlated with the output current from the diode subjected to radiation. Thus, the dose is obtained offline by the integration of the corresponding current signal. The irradiations are performed with an industrial Gammacell 60Co facility at 2.3–2.44 kGy/h covering doses up to 275 kGy. Under continuous irradiation, both diodes delivered current signals whose intensities decreased with accumulated doses. Mitigation of this decay has been accomplished by pre-irradiating the devices to 700 kGy. Polynomial functions best represent the dose responses for either pristine or preirradiated diodes. The relevant dosimetric parameters as response stability, charge sensitivity, and repeatability of current signals (<5%) reveal the better performance of the MCz diode. It is important to note that the whole dataset fully complies with the international standard protocols for routine dosimeters in radiation processing dosimetry. Regarding radiation damage, which in unbiased diodes manifests primarily in the decay of current sensitivity, the results also showed greater tolerance of the MCz diode. Based on these studies, large availability, and better cost-effectiveness, it is possible to endorse the potential use of MCz devices as online routine dosimeters in radiation processing applications. However, the data reproducibility with the accumulated dose, the dose lifespan, and the effect of the irradiation conditions (e.g., temperature, relative humidity, and dose fractionating) remain to be investigated. Works in this direction are currently in progress.

Palavras-Chave: silicon diodes; radiations; processing; czochralski method; gamma dosimetry

BUENO, C.C.; CAMARGO, F.; GONCALVES, J.A.C.; PASCOALINO, K.; MANGIAROTTI, A.; TUOMINEN, E.; HARKONEN, J. Performance characterization of dosimeters based on radiation-hard silicon diodes in gamma radiation processing. Frontiers in Sensors, v. 3, p. 1-11, 2022. DOI: 10.3389/fsens.2022.770482. Disponível em: http://repositorio.ipen.br/handle/123456789/32971. Acesso em: $DATA.

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Abstract: The storage of energy generated by photovoltaic system is one problem of it. In this aspect, integrated energy conversion and storage systems, IECSS, using supercapacitors are presented as a solution. Dye sensitized solar cell becomes a main candidate for use in IECSS due its variety of applications. Recent studies shown that zinc oxide (ZnO) is a natural candidate for use in solar cells and supercapacitor due to its high energy density of the order 650 A g-1. The aims of this paper were: i) the study of the influence of the morfology of nanostructured ZnO nanoparticles obtained by the hydrothermal method using distincts complexing agents: etylenediaminetetraacetic acid (EDTA); hexamethyltetramine (HMT) and diaminometanal (urea), besides commercial ZnO; ii) study of the ZnO and activated carbon at ratio X:Y of 10:90, 20:80 and 30:70 in proportion of mass (%) in the preparation of electrodes. The commercial ZnO, which presents particles with spherical and porous morphology, presented the best capacitance result 8.38 Fg-1 at 10:90 ratio, that demonstrates the ZnO is an excellent candidate for material for supercapacitor coupled with dye solar cell.

Palavras-Chave: capacitive energy storage equipment; capacitors; energy storage; zinc oxides; solar cells; sensitizers; electrodes; hydrothermal systems

SILVA, PAULA M. da; SERNA, MARILENE M.; GALEGO, EGUIBERTO; FARIA, RUBENS N. Study of supercapacitors for use in dye sensitized solar cells. Materials Science Forum, v. 1012, p. 114-118, 2020. DOI: 10.4028/www.scientific.net/MSF.1012.114. Disponível em: http://200.136.52.105/handle/123456789/31641. Acesso em: $DATA.

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Abstract: The response of thin diodes (SFH206k) as dosimeters has been investigated employing the beam of an electron accelerator within the dose rate range of 2–8 kGy/s and accumulated doses up to 100 kGy. These devices, operating in the short-circuit mode and under industrial irradiation conditions, deliver current signals nonlinearly dependent on the dose rate, whichever the dose history of the diodes, due to the high density of the generated electron-hole pairs herein achieved. Despite this nonlinearity, the dose rate response is stable and characterized by current signals with repeatability better than 2.0%, regardless of the accumulated dose. It is also found that the dose responses are quite linear with sensitivities slightly dependent on the accumulated dose at a constant dose rate. The decrease in the charge sensitivity, taking as reference that obtained before any radiation damage, reaches only 9% (k = 2) at 100 kGy, which is much smaller than the values reported in the literature. From this low aging and the repeatability of both dose rate and dose responses, it seems that the photodiode under investigation is a low budget alternative, good enough for routine dosimetry, provided it has been previously calibrated in the same processing facility.

Palavras-Chave: photodiodes; dosimetry; electron beams; dosemeters; electron dosimetry; si semiconductor detectors; dose rates

GONCALVES, JOSEMARY A.C.; MANGIAROTTI, ALESSIO; ASFORA, VIVIANE K.; KHOURY, HELEN J.; BUENO, CARMEN C. The response of low-cost photodiodes for dosimetry in electron beam processing. Radiation Physics and Chemistry, v. 181, p. 1-8, 2021. DOI: 10.1016/j.radphyschem.2020.109335. Disponível em: http://repositorio.ipen.br/handle/123456789/31961. Acesso em: $DATA.

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