Humidity effects on neutron irradiated beryllium Zabolockis, Rudolfs Janis; Pajuste, Elina; Avotina, Liga
Nuclear materials and energy,
June 2023, 2023-06-00, 2023-06-01, Volume:
35
Journal Article
Peer reviewed
Open access
•Oxidation of beryllium is enhanced by neutron irradiation and elevated humidity.•Elevated humidity and neutron irradiation lower thermal process temperatures.•Oxidation of beryllium yields a mobile ...needle- and cluster-like oxide layer.•Tritium inclusions due to neutron irradiation are released above 1040 K.•Beryllium oxide structure depends on the humidity level in airflow.
This study focuses on neutron-irradiated beryllium interactions with air of differing humidity, simulating water cooled fusion reactor malfunction.
Beryllium in the form of ∼ 1 mm ∅ pebbles has been used in the study. Both non-irradiated and neutron-irradiated pebbles were thermally treated and studied using thermogravimetric/differential thermal analysis in dry airflow with relative humidity (RH) < 5 % and humid > 90% RH.
Surface structure and composition was investigated with scanning electron microscopy (SEM) and energy dispersion X-ray spectrometry (EDX). Tritium release was monitored using a tritium monitor.
Results show that elevated RH coupled with neutron irradiation damage on beryllium yields the largest mass increase of 180% (in relation to the initial mass) compared to non-irradiated Be treated in RH < 5% which resulted in 3 % mass increase. SEM and EDX revealed a substantial number of cracks as well as the formation of irregular shape micro-/nanoparticles of BeO. Tritium release took place at temperatures above ∼ 1040 K, reaching a peak after 1263 K. Overall tritium inventory was estimated to be up to 1.08∙1017 T atoms/g.
Sulfonated poly(ether ether ketone) (SPEEK) materials are promising candidates for replacing Nafion™ in applications such as proton exchange membrane (PEM) and direct methanol fuel cells. SPEEK ...membranes have several advantages such as low cost, thermal and radiation stability and controllable physicochemical and mechanical properties, which depend on the degree of sulfonation (DS). Commercial PEEK was homogenously sulfonated up to a DS of 60–90% and the membranes were prepared using a solvent casting method. Part of the samples were irradiated with a 10 MeV electron beam up to a 500 kGy dose to assess the ionizing radiation-induced effects. Both non-irradiated and irradiated membranes were characterized by Fourier Transformation infrared (FT-IR) spectroscopy, thermogravimetric analysis (TGA), proton nuclear magnetic resonance (1H-NMR) spectroscopy, electrochemical impedance analysis and, for the first time for non-irradiated membranes, by spectrophotometric analysis with Cr(III). The above-mentioned methods for application for DS assessment were compared. The aim of this study is to compare different methods used for the determination of the DS of SPEEK membranes before and after high-dose irradiation. It was observed that irradiated membranes presented a higher value of DS. The appearance of different new signals in 1H-NMR and FT-IR spectra of irradiated membranes indicated that the effects of radiation induced changes in the structure of SPEEK materials. The good correlation of Cr(III) absorption and SPEEK DS up to 80% indicates that the spectrophotometric method is a comparable tool for the characterization of SPEEK membranes.
Background
In order to support the ongoing research across Europe to facilitate access to novel radionuclides, the PRISMAP consortium (European medical radionuclides programme) was established to ...offer the broadest catalog of non-conventional radionuclides for medical and translational research. The aim of this article is to introduce readers with current status of novel radionuclides in Europe.
Main body
A consortium questionnaire was disseminated through the PRISMAP consortium and user community, professional associations and preclinical/clinical end users in Europe and the current status of clinical end-users in nuclear medicine were identified. A total of 40 preclinical/clinical users institutions took part in the survey. Clinical end users currently use the following radionuclides in their studies:
177
Lu,
68
Ga,
111
In,
90
Y, other alpha emitters,
225
Ac,
64
Cu and Terbium isotopes. Radionuclides that would be of interest for users within the next 2–5 years are
64
Cu, Terbium radionuclide “family” and alpha emitters, such as
225
Ac.
Conclusions
Thanks to a questionnaire distributed by the PRISMAP consortium, the current status and needs of clinical end-users in nuclear medicine were identified.
Silicon nitride (Si3N4) in a form of single and multi-layer nanofilms is proposed to be used as a dielectric layer in nanocapacitors for operation in harsh environmental conditions. Characterization ...of surface morphology, roughness and chemical bonds of the Si3N4 coatings has an important role in production process as the surface morphology affects the contact surface with other components of the produced device. Si3N4 was synthesized by using low pressure chemical vapour deposition method and depositing single and multi-layer (3 – 5 layers) nanofilms on SiO2 and polycrystalline silicon (PolySi). The total thickness of the synthesized nanofilms was 20 – 60 nm. Surface morphology was investigated by means of scanning electron microscopy (SEM) and atomic force microscopy (AFM). Chemical bonds in the layers were identified by means of Fourier transform infrared spectrometry, attenuated total reflection (FTIR-ATR) method. (From the SEM and AFM images it was estimated that both single and multi-layer coatings are deposited homogenously. Si-N breathing and stretching modes are observed in FTIR spectra and the surface morphology is highly dependent on PolySi, therefore suggesting the decrease of the roughness of the bottom electrode for use in the nanocapacitors.
The radionuclides 43Sc, 44g/mSc, and 47Sc can be produced cost-effectively in sufficient yield for medical research and applications by irradiating natTi and natV target materials with protons. ...Maximizing the production yield of the therapeutic 47Sc in the highest cross section energy range of 24–70 MeV results in the co-production of long-lived, high-γ-ray-energy 46Sc and 48Sc contaminants if one does not use enriched target materials. Mass separation can be used to obtain high molar activity and isotopically pure Sc radionuclides from natural target materials; however, suitable operational conditions to obtain relevant activity released from irradiated natTi and natV have not yet been established at CERN-MEDICIS and ISOLDE. The objective of this work was to develop target units for the production, release, and purification of Sc radionuclides by mass separation as well as to investigate target materials for the mass separation that are compatible with high-yield Sc radionuclide production in the 9–70 MeV proton energy range. In this study, the in-target production yield obtained at MEDICIS with 1.4 GeV protons is compared with the production yield that can be reached with commercially available cyclotrons. The thick-target materials were irradiated at MEDICIS and comprised of metallic natTi, natV metallic foils, and natTiC pellets. The produced radionuclides were subsequently released, ionized, and extracted from various target and ion source units and mass separated. Mono-atomic Sc laser and molecule ionization with forced-electron-beam-induced arc-discharge ion sources were investigated. Sc radionuclide production in thick natTi and natV targets at MEDICIS is equivalent to low- to medium-energy cyclotron-irradiated targets at medically relevant yields, furthermore benefiting from the mass separation possibility. A two-step laser resonance ionization scheme was used to obtain mono-atomic Sc ion beams. Sc radionuclide release from irradiated target units most effectively could be promoted by volatile scandium fluoride formation. Thus, isotopically pure 44g/mSc, 46Sc, and 47Sc were obtained as mono-atomic and molecular ScF 2+ ion beams and collected for the first time at CERN-MEDICIS. Among all the investigated target materials, natTiC is the most suitable target material for Sc mass separation as molecular halide beams, due to high possible operating temperatures and sustained release.
In this paper, we present results on tritium release from the beryllium pebbles irradiated for 294 full power days from 17 April 2003 to November 2004 to the neutron fluence of 1.5-2 × 10
25
m
-2
...(E>1 MeV) at temperature 523-773 K in the pebble-bed assemblies (PBA) experiment in the high flux reactor (HFR) at Petten, the Netherlands. Stages of gradual and burst release are evident in the tritium release of the PBA Be pebbles at a temperature ramp of 2.3-4.8 K/min from room temperature to 1310-1520 K. These two stages may be related to the tritium release by atomic diffusion and bubble venting respectively. The main maximum of the tritium release rate of the PBA Be pebbles was found to be in the temperature ranges of 1178-1309 K and 1178-1350 K at the temperature ramps of 2.4 and 4.8 K/min respectively. The tritium inventory and abundance ratios of chemical forms of tritium localized in the pebbles were determined with dissolution methods. The total tritium inventory in the PBA Be pebbles was found to be 2-4 GBq/g.
Radiation resistance of nanolayered silicon nitride capacitors Romanova, Marina; Avotina, Liga; Andrulevicius, Mindaugas ...
Nuclear instruments & methods in physics research. Section B, Beam interactions with materials and atoms,
05/2020, Volume:
471
Journal Article
Peer reviewed
Single-layered and multi-layered 20–60 nm thick silicon nitride (Si3N4) dielectric nanofilms were fabricated using a low-pressure chemical vapour deposition (LPCVD) method. The X-ray photoelectron ...spectroscopy (XPS) confirmed less oxygen content in the multi-layered nanofilms. The capacitors with Si3N4 multilayer demonstrated a tendency to a higher breakdown voltage compared to the capacitors with Si3N4 single layer. Si3N4 nanofilms and capacitors with Si3N4 dielectric were exposed to 1 kGy dose of gamma photons. Fourier transform infrared (FTIR) spectroscopy analysis showed that no modifications of the chemical bonds of Si3N4 were present after irradiation. Also, gamma irradiation did not influence the breakdown voltage of the capacitors but decreased their capacitance measured at 1 MHz frequency. However, the multi-layered capacitors were not affected by radiation more than the single-layered capacitors. These findings suggest a promising process to fabricate nano-scaled multi-layered Si3N4 capacitors with improved breakdown voltage characteristics and resistance to ionizing radiation.
•JET-C divertor samples from 200 to 2009 and JET-ILW 2010–2012 are compared.•JET-C sample had >20 times higher concentration of tritium than JET-ILW sample.•FTIR signals of EP in the 400–1000 cm−1 ...range could be due to the metal-oxygen bonds.•In Raman spectra of EP an increased luminescence background occurs.•In the ESR spectra of EP a signals with g = 2.002 and 2.12 are observed and analysed.
One of main reasons of the Joint European torus (JET) transformation from the carbon (JET-C) to ITER-like (JET-ILW) wall was high tritium retention of carbon. In order to compare the tritium retention, samples of analogous positions of the plasma-facing side of vertical tiles No. 3 of two campaigns: JET-C (2008–2009) and JET-ILW (2011–2012) were cut out.
Temperature-programmed tritium desorption spectrometry in He + 0.1% H2 gas flow showed that JET-C sample without a tungsten coating had by a factor of >20 higher surface concentration of tritium than JET-ILW tungsten-coated sample: 4.9 × 1013 and 1.7–2.2 × 1012 T atoms/cm2 respectively.
Installation of metallic plasma facing wall in the JET was a unique possibility to collect from the vacuum vessel the first wall erosion products (EP) – dust and flakes. Selected EP were investigated by means of energy dispersion X-ray (EDX), electron spin resonance (ESR), infrared and Raman spectrometry. EDX analysis shows presence of metallic impurities and carbon as a main component. Investigations with ESR spectrometry allows to estimate presence of two main paramagnetic centres – g = 2.002 and g = 2.12. Infrared spectra show presence of inorganic oxides. The obtained results supplement the information about composition of the EP from fusion devices.
Beryllium pebble behaviour has been studied regarding the accidental operation conditions of tritium breeding blanket of fusion reactors. Structure evolution, oxidation and thermal properties have ...been compared for nonirradiated and neutron irradiated beryllium pebbles during thermal treatment in a temperature range from ambient temperature to 1600 K. For neutron irradiated pebbles tritium release process was studied. Methods of temperature programmed tritium desorption (TPD) in combination with thermogravimetry (TG) and temperature differential analysis (TDA), scanning electron microscopy (SEM) in combination with Energy Dispersive X-ray analysis (EDX) have been used. It was found that there are strong relation between tritium desorption spectra and structural evolution of neutron irradiated beryllium. The oxidation rate is also accelerated by the structure damages caused by neutrons.
Post-irradiation tritium release from the Pebble Bed Assembly (PBA) neutron-irradiated beryllium (Be) pebbles (empty_set approximately 1 mm; the total tritium inventory 2-4 GBq/g) was investigated on ...annealing in He + 0.1% H2. Temperature ramps of 2.3 K/min followed by annealing for 1 h at 1310-1320 K resulted in complete detritiation of the PBA Be pebbles. The tritium burst release occurred after a time lag of 1-6.5 h during constant temperature anneals at 1089-1180 K, with the release time measured after reaching the annealing temperature. Tritium burst release was also observed to occur during cool down. Anneals at 1089 K for 8 h and at 1045 K for 23 h caused detritiation of the PBA Be pebbles by >=75%. Effective values of the tritium diffusivity were estimated for the PBA Be pebbles as 2.6 10-13 m2/s for 1045 K; 4.7-5.1 10-13 m2/s for 1089 K.
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