Thermal oils have been utilized as heat transfer fluids for several decades in many applications, including industrial facilities, power plants and solar receiver systems. Despite their large employment, very few data are available about oils behavior under thermal stress and related degradation processes. For these reasons, the thermal stability of a silicone-based diathermic oil, Bluesil FLD 550 HT, was investigated in the present work. A laboratory-scale set-up was assessed to perform controlled heating tests, and fresh and thermally aged oils samples were analyzed to determine changes in chemical composition and thermo-physical features. Degradation products in the gaseous and vapor phase were also detected and analyzed by online and offline measurements. The obtained results are compared with the ones present for aromatic oils, largely employed as heat transfer media. Bluesil showed a higher thermal resistance compared to aromatic materials, and, thanks to its low volatility together with a high chemical stability, it was successfully tested up to 500 °C. According to its polymeric structure, thermal degradation processes occur mainly through Si-O bond scission, leading to both the segmentation of silicone chains and the formation of cross-linked species as byproducts.

The paper presents a conceptual study of a neutron source based on a spherical tokamak (ST). The plasma scenario chosen for the ST is non-thermal fusion (hot ion mode), which is extensively used on machines like JET and TFTR deuterium–tritium (DT) experiments, which seems suited for low fusion gain reactors. As demonstrated in experiments, this scenario is a robust tool for neutron production. Starting from a new scaling law of energy confinement tested, approximately, on ST40 spherical tokamak, the parameters of a 15 MW ST DT fusion reactor (ST180) are derived, and a preliminary radial build of the machine is established.

The studies on the development of fusion–fission hybrid reactors (FFHR) have gained consensus in recent years as an intermediate step before fusion energy. This work proposes a possible approach to FFHRs based on the coupling of a Reversed Field Pinch fusion machine and a Molten Salt Subcritical fission test bed. The proposed test bed is characterized by the coexistence of a fast-neutron fission core and a dedicated thermal-neutron zone, allowing the performing of tritium breeding and actinides transmutation studies. The neutronic design solutions and the results obtained by the irradiation of FLiBe salt (inside the thermal-neutron zone) and of an actinide target (inside the core) are shown. The outcomes of the analysis reveal the potential of FFHR systems as breeding/burner systems. In particular, the results regarding tritium breeding are very encouraging as the system is demonstrated to be able to reach a very high Tritium Breeding Ratio.

Fusion–fission hybrid reactors are concepts of subcritical reactors based on the coupling of fusion and fission devices. In this case, the fusion reactor would work as an external neutron supplier for the fission core of the machine. Such systems could, in principle, operate as multi-purpose machines, such as energy generators, breeders and waste burners. The large availability of fusion and fission technologies makes the choice of devices to couple quite chaotic. In fact, most of the concepts proposed in the literature are based on attempts without real optimization. The purpose of this paper is to propose a parameter which could provide practical information regarding the choice or the design of the fusion system of an FFHR. An engineering approach based on the estimation of the energy efficiency of FFHRs was used. An evaluation of the parameter and some of its possible practical applications are shown. Obtained results indicate that, from a geometrical point of view, compact machines would need lower Q-values to reach high neutron source performance.

Laser-driven plasma wakefields can provide hundreds of MeV electron beam in mm-range distances potentially shrinking the dimension of the actual particle accelerators. The plasma density plays a fundamental role in the control and stability of the acceleration process, which is a key development for the future electron injector proposed by EuPRAXIA. A gas cell was designed by LPGP and LIDYL teams, with variable length and backing pressure, to confine the gas and tailor the gas density profile before the arrival of the laser. This cell was used during an experimental campaign with the multi TW-class laser at the Lund Laser Centre. Ionization assisted injection in a tailored density profile is used to tune the electron beam properties. During the experiment, we filled the gas cell with hydrogen mixed with different concentration of nitrogen. We also varied the backing pressure of the gas and the geometrical length of the gas cell. We used a transverse probe to acquire shadowgraphic images of the plasma and to measure the plasma electron density. Methods and results of the analysis with comparisons between shadowgraphic and interferometric images will be discussed.

New nuclear technologies are currently being study to face High Level Waste treatment and disposal issues. Generally, GEN-IV fission Fast Reactors (FR) are considered the waste-burners of the future. In fact, a fast flux turns out to be the best choice for actinides irradiation in critical reactors because of favorable cross section conditions. Differently, Fusion Fission Hybrid Reactors (FFHR) are futuristic devices based on the combination of fusion and fission systems and could represent an alternative to FRs. In such systems, the choice spectrum of the neutron flux that irradiates HLW may be non-obvious due to some operational constraints which have to be considered. To design and optimize these systems as waste-burners, one should fully understand the transmutation dynamics occurring into the fission region. A multi-energy-group analysis by FISPACT-II code has been set to analyze the conversion processes in scenarios characterized by different neutron energy spectra and fluences. The results of this study show that, despite fast fluxes are characterized by better behaviors in terms of radiotoxicity treatment, the difficulties of reaching high reaction yields may require solutions involving moderators or broadened neutron fluxes to increase the reactions probabilities and, consequently, actinides mass conversion yield.

Several observational studies investigated risk factors for suicide attempts/completed suicides in older age with contrasting evidence from ongoing population-based research. The risk factors most associated to suicide attempts than other variables were: depressive disorders, methods employed to self-harm (particularly poisoning), and psychotropic drug utilization followed by psychological factors and disability. Moreover, male sex, violent methods to self-harm, any psychiatric disorder (depression, anxiety and bipolar disorders), a poor medical condition, stressors/bereavement, and living alone appeared to be more significant for predicting completed suicides in late life. There is growing evidence of a role of environmental exposures in the pathogenesis and epigenetics of suicidal behavior in older age. Little is known about the possible relationship between suicidal ideation in older age and its biopsychosocial predictors, although psychiatric disorders (among which late-life depression, LLD), play a fundamental role. LLD, distinguished as late-onset depression (LOD) and early-onset depression (EOD). Suicidal ideators accounted for 2.32% of subjects, were female, smokers and obese affected by multimorbidity. After adjusting for age, gender, education and social dysfunction, suicidal ideation was associated to LLD (EOD>LOD:OR:21.71, 95% CI:9.22-51.14). In the full random forest model, asthma was the most important contributor to suicidal ideation. Among biomarkers, interleukin (IL)-6 followed by tumor necrosis factor (TNF)-a, Apolipoprotein E e4 allele-carriers, C-reactive protein contributed most to suicidal ideation. Although EOD is a strong determinant of suicidal ideation, other non-psychiatric factors, i.e., serum inflammation biomarkers, APOE e4 allele, and multimorbidity, should be taken into account when evaluating a suicidal ideation phenotype in older age.DisclosureNo significant relationships.

The radiation effect on electronic devices is a critical issue for nuclear facilities, accelerators, and spatial missions as well as for fusion machines. Phenomena related to particle interactions have significant impact on the normal functioning of such devices: they could arise progressively during machine lifetime due to the cumulated ionization [total ionizing dose (TID)], cumulated atomic displacement (dpa) or it can appear instantaneously after a single highly ionizing particle interaction [single-event effect (SEE)]. The divertor tokamak test (DTT) facility is a tokamak machine, which will produce, in its high-performance phase, up to $1.5\times 1017$ n/s at 2.45 MeV from deuterium–deuterium reactions plus about 1% of 14.1-MeV neutrons produced by the triton burn-up inside the plasma. Such significant neutron production implies a severe radiation environment, up to 1010 n/cm2/s and $5\times 109\,\,\gamma $ /cm2/s [secondary gammas mainly due to (n, $\gamma $ ) reactions], inside Torus Hall building (THB) and outside the THB nearby the penetrations. DTT will be equipped with several power and signal electronic devices: 1) critical electronics that play a crucial role for the machine functioning in order to avoid failure, loss of plasma stability, and damages on the structural components (e.g., energy supply to the toroidal field, poloidal field, and central solenoid superconductive magnets); and 2) noncritical electronics, used to power diagnostics and systems whose failures do not compromise the machine operations, but are essential for scientific and engineering exploitation programs. Neutronics and shielding studies of electronics are fundamental for protecting the main components of the tokamak and to avoid the failure of the critical systems, as well as for the evaluation of the positioning and functioning of the noncritical devices and the selection of radiation-hard electronics. In this work, 3-D shielding studies for the DTT electronics devices, carried out with MCNP Monte Carlo code, are presented and discussed as well as the effectiveness of the proposed arrangement and mitigation solutions.

The aim of this work is to characterize an aromatic thermal oil against its maximum working temperatures with a preliminary laboratory scale oil stability characterization, to study the oil behavior under thermal stress. At this purpose, a dedicated laboratory scale set-up was built-up to undergo an oil sample to thermal stress tests. A mixture of C13-C20 alkyl substitute benzene was chosen as a representative aromatic oil to be studied.

Fusion Fission Hybrid Systems (FFHS) could have a potential role in the management of fission reactor wastes, with (in principle) some advantage over the comparable Accelerator Driven systems, devoted to the same objective. The validation of the concept poses major challenges in the area of fusion "source" development. However, the physics of the multiplying and transmutation blanket has also to be carefully understood and validated. Simple experiments can be envisaged for that purpose. Some of these experiments have already been performed in a different research framework (i.e. validation of the ADS concepts) and could constitute a very first database. Moreover, a new series of similar experiments could be planned. (C) 2020 Elsevier Ltd. All rights reserved.

The present paper summarizes the studies related to the development of the conceptual basis of tokamak neutron sources useful for fusion fission hybrid (FFH) reactors and the FFH concept experimental validation. The parameters for a tokamak neutron source are determined by a newly derived scaling laws, based on an extension of the Kadomtsev similarity principle to fusion reactors. The tokamak model obtained is then used as neutron source for a fusion fission hybrid reactor which uses fusion and fission blankets ( which is operated in subcritical mode). This FFH model is simulated using MCNP to determine the tritium produced and the nuclear waste burned. An essential result of this evaluation is the strong ( a factor 6 ) increase of tritium production in the fusion blanket when the nuclear fuel is present in the fission blanket. In parallel, we formulate a proposal of an experimental validation of the FFH concept by using a fusion source injecting neutrons in the core of TRIGA RC-1 reactor configured in subcritical operation mode.

Fusion-fission hybrid systems (FFH) represent a coupling between a fusion device and a subcritical fission reactor driven by neutrons produced by fusion reactions.This kind of systems, in principle, can be useful for different purposes, for example, as energy amplifier or as nuclear waste burner.In this work, the preliminary characteristics and potentialities of a FFH based on a tokamak device characterized by high magnetic field (B > 9 T) and high-density plasma (n > 10 14 cm -3 ) have been evaluated.During the years high magnetic field compact tokamaks have been designed, built and operated.Thanks to their characteristics, such as compactness, high field and high density plasma, these devices can produce intense neutron fluxes, and therefore are good candidates to be incorporated in FFH while operating in a sub-ignited regime.An additional advantage is that their design is based on relatively simple existing technology.In this work, a coupling between a tokamak (operating in DD-mode) and a subcritical molten salt fission blanket has been proposed.Molten salt reactor could be adapted for this purpose and could help the hybrid system to increase its energy balance.A model with a molten salt fission blanket (k eff = 0.92, P = 95 MW) instead of the lithium one, has been considered and studied in terms of neutronic evaluations.Presented preliminary numerical calculations based on a neutron Monte-Carlo code confirm the potentialities of the system.

Thermal oils are nowadays largely employed as heat transfer fluids or cooling media in industrial and energy production plants. However, despite their widespread use, very few data are currently available about their chemical stability and possible composition changes in function of the operating temperatures, which are of crucial importance to evaluate the lifetime of these materials in real conditions. In the present work, a commercial terphenyl-based oil was investigated with respect to its thermal stability, performing ageing tests followed by a complete post-characterization analysis. To this purpose, a dedicated experimental set-up was designed and constructed to study the degradation processes, with a qualitatively and quantitatively analysis of the released gases and condensable products, together with a post-ageing characterization of the oil thermo-physical properties. The results show that the main decomposition mechanism involves the loss of hydrogen atoms, followed by partial polymerization processes, which explain the increase in dynamic viscosity and the decrease in volatility observed for the thermally stressed materials. Finally, the decomposition kinetic constants were estimated, obtaining a value of about 100 kJ/mol for the activation energy, which is in good agreement with the data available in the scientific literature.

A simplified Fusion-Fission Hybrid System (FFHS) deterministic calculation model has been developed in order to study the coupling between a fusion machine and a subcritical fission system.Monte-Carlo (MC) codes are very flexible and they have to be considered as reference calculation tools for complex systems like FFHS.On the other hand, deterministic codes can provide, in shorter calculation time respect to MC codes, parametric and sensitivity analysis, also by exploiting General Perturbation Theory (GPT) methodologies, which can usefully support the global FFHS theoretical analysis.This work describes the comparison between the results obtained for a simplified FFHS model by using a MC code (MCNP6.1,MC N-Particle) and a deterministic code (ERANOS).In particular, in this preliminary study, integral parameters like k eff , thermal power, neutron fluxes and some key reaction rate profiles, will be compared.If the comparison between the two mentioned codes will give encouraging results further, more refined, studies will be performed in order to consider deterministic codes as a powerful workhorse for the FFHS analysis, including time dependent analysis devoted to transient and reactivity monitoring issues.

Alzheimer’s disease (AD) is the most common neurodegenerative disease among the elderly with a progressive decline in cognitive function significantly affecting quality of life. Both the prevalence and emotional and financial burdens of AD on patients, their families, and society are predicted to grow significantly in the near future, due to a prolongation of the lifespan. Several lines of evidence suggest that modifications of risk-enhancing life styles and initiation of pharmacological and non-pharmacological treatments in the early stage of disease, although not able to modify its course, helps to maintain personal autonomy in daily activities and significantly reduces the total costs of disease management. Moreover, many clinical trials with potentially disease-modifying drugs are devoted to prodromal stages of AD. Thus, the identification of markers of conversion from prodromal form to clinically AD may be crucial for developing strategies of early interventions. The current available markers, including volumetric magnetic resonance imaging (MRI), positron emission tomography (PET), and cerebral spinal fluid (CSF) analysis are expensive, poorly available in community health facilities, and relatively invasive. Taking into account its low cost, widespread availability and non-invasiveness, electroencephalography (EEG) would represent a candidate for tracking the prodromal phases of cognitive decline in routine clinical settings eventually in combination with other markers. In this scenario, the present paper provides an overview of epidemiology, genetic risk factors, neuropsychological, fluid and neuroimaging biomarkers in AD and describes the potential role of EEG in AD investigation, trying in particular to point out whether advanced analysis of EEG rhythms exploring brain function has sufficient specificity/sensitivity/accuracy for the early diagnosis of AD.

The global need for energy in the world is constantly increasing. Critical fission reactors have proved great efficiency in the energy production, but the fear of nuclear wastes and accidents due to an uncontrolled chain reaction makes these unpleasant to public. More safe fusion reactors, on the opposite, have low efficiency. Hybrid reactors capable of using the advantages of both are studied, but not yet developed. In this paper, a simple fusion–fission pilot experiment model has been developed. A Tokamak with the same characteristics of DTT (Divertor Tokamak Test facility) has been considered as a reference machine for the fusion component. The fusion system has been coupled with a relatively simple low-power fission blanket configured into three different modes by using different fuels and materials. This model could be useful in order to investigate the properties of the fusion–fission hybrid coupling from a neutronic point of view.

We report a 82-year-old woman, who gradually started to present in 2015 cognitive impairment (forgetfulness, impaired attention) with fluctuating course and behavioural symptoms (auditory and visual hallucinations, apathy). Since Spring 2016, progressive slowness of movements was observed. Since Autumn 2016, she felt that another person was inside her and was telling her what to do. Neurological examination showed ipomimia, akinesia and rigidity in all limbs, postural abnormalities, difficulties in gait. The patient underwent an extensive neuropsychological assessment, MRI, Single Photon Emission Tomography (SPET) with dopamine transporter (DAT) scan. In July 2016, MRI scan showed cortical and subcortical atrophy and small areas of increased signal intensity in centrum semiovalis of both cerebral hemispheres on FLAIR sequences. In September 2016, neuropsychological testing documented cognitive impairment, mainly characterised by deficits of executive functions and episodic memory. In June 2017, about 2 years after disease onset, DAT-scan did not show decreased DAT striatal uptake. So far, the patient refused a repeat DAT-scan SPECT. According to current diagnostic criteria, a clinical diagnosis of probable Dementia with Lewy bodies can be made in this patient. The absence of abnormalities on DAT-scan, reported in a low percentage of patients with neuropathologically confirmed diagnosis of DLB, may arise from a less marked neuronal loss in the substantia nigra in such patients, who may show abnormal DAT-scan on follow-up. This case supports the view that DLB in early stages may show different patterns of presentation from clinical and neuropathological viewpoints.

Light dark matter (LDM) in the context of dark sector theories is an attractive candidate to make up the bulk of the mass of our Universe. This proposal presents the LDM discovery potential of a low-pressure, negative-ion, time-projection-chamber detector placed downstream of the Hall A beam-dump at Jefferson Lab receiving 10 ​22​ electrons on target (EOT). As with the approved Beam-Dump eXperiment (BDX) the Directional Recoil Identification From Tracks Beam-Dump eXperiment (DRIFT-BDX) would run parasitically and in parallel with BDX providing additional reach, confirmation potential and different backgrounds all providing a high degree of complementarity. DRIFT-BDX is sensitive to elastic nuclear recoil events with a threshold of ~1 keV/amu recoil energy. Multiple, powerful signatures of LDM interactions are possible with BDX-DRIFT detector. Detailed calculations present cosmic ray and beam-related background estimates. The proposed experiment will be sensitive to large regions of LDM parameter space, exceeding the discovery potential of existing and planned experiments in the MeV-GeV DM mass range.