Synthesis and characterization of homogeneous (U,Am)O₂ and (U,Pu,Am)O₂ nanopowders

This paper details the first dedicated production of homogeneous nanocrystalline particles of mixed actinide oxide solid solutions containing americium. The target compositions were $U_{0.75}Pu_{0.20}Am_{0.05}O_{2}$, $U_{0.90}Am_{0.10}O_{2}$ and $U_{0.80}Am_{0.20}O_{2}$. After successful hydrothermal synthesis and chemical characterisation, the nanocrystals were sintered and their structure and behaviour under self-irradiation were studied by powder XRD. Cationic charge distribution of the as-prepared nanocrystalline and sintered $U_{0.80}Am_{0.20}O_{2}$ materials was investigated applying $U M_{4}$ and $Am M_{5}$ edge high energy resolution XANES (HR-XANES). Typical oxidation states detected for the cations are $U_{(IV)}/U_{(V)}$ and $Am_{(III)}/Am_{(IV)}$. The measured crystallographic swelling was systematically smaller for the as-synthesised nanoparticles than the sintered products. For sintered pellets, the maximal volumetric swelling was about 0.8% at saturation, in line with literature data for $PuO_{2}$, $AmO_{2}$, $(U,Pu)O_{2}$ or $(U,Am)O_{2}$

Cytokines in relation to hCG are significantly altered in asymptomatic women with miscarriage – a pilot study

Background: Spontaneous abortion is one of the most common complications in early pregnancy. A preventive test to identify women who will experience a miscarriage, even before first symptoms occur, is not established. Activation of maternal immunological tolerance seems to be essential for early fetal development and various cytokines have been described in different stages of pregnancy. Therefore, we aimed to investigate if chemokine levels at the time of pregnancy testing relative to human Choriogonadotropin (hCG) are altered in patients who will experience a miscarriage in this pregnancy. Methods: We obtained blood samples from 39 women. Dependent on the follow-up, patients with a positive pregnancy test were subsequently divided in two groups: ongoing pregnancy (n = 22) and miscarriage (n = 17) in this pregnancy. Immunological and endocrine profiling of maternal plasma at the time of pregnancy testing (5th week of gestation) was performed for each group at the time of pregnancy test using Multiplex and ELISA analysis. Results: hCG was significantly decreased in patients with abortion whereas levels of IL-1ra, MIP-1a and TNF-alpha were significantly increased. GCSF/ IL-1ra-ratio was 1.66-fold increased in patients with ongoing pregnancy. TGF-beta /MIP1a-ratio was significantly 3.45-times higher in patients with miscarriage. Comparing patients with ongoing pregnancy to patients experiencing a miscarriage, we could demonstrate significant alterations of the ratios MIP1a/hCG, IL-1ra/hCG, TNFalpha/hCG, MCP1/hCG, IL-6/hCG, TPO/hCG and TGF-beta1/hCG. The strongest effects were seen for the ratio MIP1a/hCG, IL-1ra/hCG and TNFalpha/hCG. Conclusions: We have shown that cytokines in relation to hCG after 4 weeks of gestation are significantly altered in women with miscarriage, promising potential as a prognostic biomarker

Radiation Effects in Americium Ceramic Compounds

Along with uranium dioxide, mixed oxides play an essential role as fuels for present or next generation nuclear reactors. Although their production has been studied extensively, the methods applied currently result in materials that are usually not homogeneous at an atomic scale. To improve the quality of the powders (homogeneity and sintering properties), the hydrothermal decomposition of oxalate method was investigated. Preliminary attempts for the (Th,Pu)O2, (Np,Pu)O2 and (Th,Np,Pu)O2 systems were reported elswhere. The procedure allowed the production of nanometric powders of U1-xPuxO2 solid solution in the full composition range. Partial oxidation of U(IV) to U(V) was observed, while plutonium was assumed to maintain its tetravalent oxidation state. Thanks to the low-temperature of the synthesis, such mixed oxides were used as reagents for the fabrication of more complicated systems. The aliovalent americium, which has a preference for the trivalent oxidation state, can be accommodated in the UO2 fluorite structure by charge compensation with U(V) only in limited amounts. Still, the feasibility of the method has been demonstrated for an Am-content relevant to transmutation fuels. Thus, U1-xAmxO2 (x = 0.1 and 0.2) and U0.75Pu0.20Am0.05 nanosized powders were produced by hydrothermal decomposition of the corresponding mixed oxalate. Typical oxidation states detected for the cations were U(IV)/U(V) for nanometric and sintered materials, respectively, where both exhibit mixed and Am(III)/Am(IV) oxidation state. Their sintering ability was tested and the volumetric expansion was measured by powder XRD as a function of storage time. A low swelling with no indications of amorphization has been derived over a period of four years

Enhanced thermal stability of organic solar cells comprising ternary D-D-A bulk-heterojunctions

Organic solar cells: Polymer mixtures enhance the thermal stability Organic solar cells increase their lifetime by adding another polymer component, paving the way towards commercialization. A team led by Alexander Colsmann at Karlsruhe Institute of Technology, Germany conducted systematic spectroscopic investigations and device characterizations to demonstrate that the degradation of PTB7-Th: PC61BM solar cell can be efficiently suppressed by incorporating the near infrared-absorbing polymer PDTP-DFBT. Upon harsh thermal stress at 120 °C for 2 h, the ternary solar cells show only a minor relative deterioration of 10% with a high power conversion efficiency of 6%. This work reveals the importance of a third component to lock the phase conformation of the polymer and fullerene domains. This is a key step for the thermally stable power output thus the commercialization of the organic solar cells

JRC Science Summit

In June 2022, the Joint Research Centre of the European Commission organised the 2022 Science Summit, the first and largest simultaneous multi-site, hybrid, multi-day science event the JRC has organised since the SARS-CoV-2 pandemic. Organised internally, with bottom-up involvement from all six JRC sites, the Summit brought together about 1900 participants in more than 60 parallel sessions and six keynote speeches in a 3-day, 6-site, highly interactive event. The Summit was conceptualised in late 2021 as a primarily JRC-internal event, with the goals to ● stimulate a debate about the role of science and how the JRC sees itself in the future; ● encourage JRC staff to reconnect after the pandemic, also between sites; and ● complement the JRC Reset, Re-imagine, Re-energize initiative. The Summit was structured in three thematic blocks ● The state of science today; ● The needs for science in the future; ● Where does the JRC go next? Each block included an invited high level keynote lecture and parallel sessions covering various topics that were proposed by JRC staff in in the first three months of 2022.JRC.S.4 - Scientific Development Programme

Störfallsimulationen und Nachbestrahlungsuntersuchungen an kugelförmigen Brennelementen für Hochtemperaturreaktoren

An important aspect of the safety of high temperature reactors is the quality of the nuclear fuel and its ability to remain intact even at high temperatures and to safely contain the radioactive fission products. In combination with a suitable reactor an inherent safety against large release of fission products can be achieved. In this work experimental simulations of severe accidents were conducted on spherical fuel elements for high temperature reactors with TRISO-coated particles and fission product release was measured. The fuel elements originated from various irradiation experiments conducted at high temperatures with high burn-up. The experiments were performed using the cold finger apparatus, a test apparatus which was already used in the past in a former version at the Research Center Jülich. The new cold finger apparatus is installed since 2005 in the Hot Cells of the European Institute for Transuranium Elements. The cold finger apparatus at the Institute for Transuranium enabled incident simulations on irradiated high temperature reactor fuel elements in a helium atmosphere at ambient pressure, at temperatures up to 1800°C and for periods of several hundred hours. Here, both the release of fission gases and the release of solid fission products were measured. In addition, in the context of the present study, the mechanical behavior of the fuel particles and the transport mechanisms of the main fission products were analyzed and the expected release was computed. For a better understanding of the processes post irradiation examinations were conducted on the available fuel elements. It was finally made an assessment of the test results which were compared with results in the existing literature. A key objective of the work was the extension of the existing data base for modern HTR-fuel towards higher burn-up and higher fluences of fast neutrons, higher operating temperatures and extended accident temperatures

Störfallsimulationen und Nachbestrahlungsuntersuchungen an kugelförmigen Brennelementen für Hochtemperaturreaktoren

An important aspect of the safety of high temperature reactors is the quality of the nuclear fuel and its ability to remain intact even at high temperatures and to safely contain the radioactive fission products. In combination with a suitable reactor an inherent safety against large release of fission products can be achieved. In this work experimental simulations of severe accidents were conducted on spherical fuel elements for high temperature reactors with TRISO-coated particles and fission productrelease was measured. The fuel elements originated from various irradiation experiments conducted at high temperatures with high burn-up. The experiments were performed using the cold finger apparatus, a test apparatus which was already used in the past in a former version at the Research Center Jülich. The new cold finger apparatus is installed since 2005 in the Hot Cells of the European Institute for Transuranium Elements. The cold finger apparatus at the Institute for Transuranium Elements enabled incident simulations on irradiated high temperature reactor fuel elements in a helium atmosphere at ambient pressure, at temperatures up to 1800 °C and for periods of several hundred hours. Here, both the release of fission gases and the release of solid fission products were measured. In addition, in the context of the present study, the mechanical behavior of the fuel particles and the transport mechanisms of the main fission products were analyzed and the expected release was computed. For a better understanding of the processes post irradiation examinations were conducted on the available fuel elements. It was finally made an assessment of the test results which were compared with results in the existing literature. A key objective of the work was the extension of the existing data base for modern HTR-fuel towards higher burn-up and higher fluences of fast neutrons, higher operating temperatures and extended accident temperatures.JRC.DG.E.2-Hot cell

Störfallsimulationen und Nachbestrahlungsuntersuchungen an kugelförmigen Brennelementen für Hochtemperaturreaktoren

An important aspect of the safety of high temperature reactors is the quality of the nuclear fuel and its ability to remain intact even at high temperatures and to safely contain the radioactive fission products. In combination with a suitable reactor an inherent safety against large release of fission products can be achieved. In this work experimental simulations of severe accidents were conducted on spherical fuel elements for high temperature reactors with TRISO-coated particles and fission product release was measured. The fuel elements originated from various irradiation experiments conducted at high temperatures with high burn-up. The experiments were performed using the cold finger apparatus, a test apparatus which was already used in the past in a former version at the Research Center Jülich. The new cold finger apparatus is installed since 2005 in the Hot Cells of the European Institute for Transuranium Elements. The cold finger apparatus at the Institute for Transuranium enabled incident simulations on irradiated high temperature reactor fuel elements in a helium atmosphere at ambient pressure, at temperatures up to 1800°C and for periods of several hundred hours. Here, both the release of fission gases and the release of solid fission products were measured. In addition, in the context of the present study, the mechanical behavior of the fuel particles and the transport mechanisms of the main fission products were analyzed and the expected release was computed. For a better understanding of the processes post irradiation examinations were conducted on the available fuel elements. It was finally made an assessment of the test results which were compared with results in the existing literature. A key objective of the work was the extension of the existing data base for modern HTR-fuel towards higher burn-up and higher fluences of fast neutrons, higher operating temperatures and extended accident temperatures

Pruebas de situaciones accidentales en combustible de HTR con el dispositivo Küfa (Accident testing of HTR fuel with the KÜFA device)

The ceramic and ceramic-like coating materials in modern high-temperature reactor fuel are designed to ensure mechanical stability and retention of fission products under normal and transient conditions, regardless of the radiation damage sustained in-pile. In hypothetical depressurization and loss-of-forced-circulation (D LOFC) accidents, fuel elements of modular high-temperature reactors are exposed to temperatures several hundred degrees higher than during normal operation, causing increased thermo-mechanical stress on the coating layers. At the Institute for Transuranium Elements of the European Commission, a vigorous experimental program is being pursued with the aim of characterizing the performance of irradiated HTR fuel under such accident conditions. A cold finger device (Küfa), operational in ITU¿s hot cells since 2006, has been used to perform heating experiments on eight irradiated HTR fuel pebbles from the AVR experimental reactor and from dedicated irradiation campaigns at the High-Flux Reactor in Petten, The Netherlands. Gaseous fission products are collected in a cryogenic charcoal trap, while volatiles are plated out on a water-cooled condensate plate. A quantitative measurement of the release is obtained by gamma spectroscopy. We highlight experimental results from the Küfa testing as well as the on-going development of new experimental facilities.JRC.DG.E.2-Hot cell