Neutronic comparison of liquid breeders for ARC-like reactor blankets

The proposed blanket for Affordable Robust Compact (ARC) reactor is one of the simplest blanket concepts. It is a bulk tank filled with a lithium and beryllium fluorides molten salt. The fluid effectively works as tritium breeder, vessel coolant and neutron moderator and shield. However, despite the simplicity of the concept, the compactness of the reactor constitutes a novelty in the fusion field. It is thus necessary to evaluate all the possible solutions for an effective blanket component. This work analyses different liquid blanket identifying the most suitable for a compact fusion reactor. More specifically, the study addresses the capability of breeding tritium in a compact solution, actively shielding the coils and reducing the radioactive waste. Findings are that FLiBe optimizes the most the system in terms of applicability, tritium breeding, compactness and activation. Nonetheless, there is no lack of backup choices. For instance, there are hints that lithium-zirconium fluoride salts could accomplish the blanket main tasks in a compact reactor too. Leaving PbLi as inefficient, but cheap and still virtually viable solution

Storia Futura dell’Energia

Quest'opera riprende la storia delle fonti di energia, ed è divisa in due parti. La prima parte, DAL FOSSILE AL RINNOVABILE, riguarda innanzitutto la storia dell'energia tout court fino agli anni '60 dello scorso secolo: comprende la parte pre-industriale e l'era delle fonti fossili. In essa troviamo poi, per i tempi più recenti, ampi approfondimenti sulle questioni climatiche e ambientali, nonchè due capitoli dedicati alle fonti eoliche e solari. La seconda parte, ENERGIA NUCLEARE, frutto soprattutto dell'eseperienza diretta dell'autore, va a completare il quadro della storia dell'energia per i tempi più recenti

Experiments on the MHD Effect on the Drainage of a LiPb Channel and Supporting Numerical Computations with the Level Set Method

To analyze the impact of the magnetohydrodynamics (MHD) effect on the fast draining of a LiPb channel (lithium-lead eutectic, 15.7 at. % Li) for a liquid metal fusion blanket such as the water-cooled lithium-lead test blanket system of ITER or DEMO, an experimental campaign was carried out with the support of the Integrated European Lead Lithium LOop experimental facility (IELLLO), installed at the ENEA Brasimone research center, Italy. The experiments were carried out by measuring the drainage time of the internal permanent magnet pump channel, normally used to circulate the LiPb in the loop, with and without the magnetic field. Moreover, this paper proposes a new numerical methodology to study the time delay induced by the MHD by using the commercial software COMSOL Multiphysics. In this way, it was possible to evaluate the LiPb fraction present at each time step in the computational domain and to estimate the time necessary for the complete drainage of the channel. The level set method was used to describe the transient behavior of the MHD flow under low-Rm approximation. The developed code was compared with the experimental results and showed good agreement, and it constitutes the first step in model validation as a possible application to ITER and DEMO. The experimental and numerical analyses performed in this work can be used as a benchmark case for MHD code development

Probing the in-plane electron spin polarization in Ge/Si0.15 Ge0.85 multiple quantum wells

We investigate spin transport in a set of Ge/Si0.15Ge0.85 multiple quantum wells (MQWs) as a function of the well thickness. We exploit optical orientation to photogenerate spin-polarized electrons in the discrete energy levels of the well conduction band at the Γ point of the Brillouin zone. After diffusion, we detect the optically oriented spins by means of the inverse spin-Hall effect (ISHE) taking place in a thin Pt layer grown on top of the heterostructure. The employed spin injection/detection scheme is sensitive to in-plane spin-polarized electrons, therefore, by detecting the ISHE signal as a function of the photon energy, we evaluate the spin polarization generated by optical transitions driven by the component of the light wave vector in the plane of the wells. In this way, we also gain insight into the electron spin-diffusion length in the MQWs. The sensitivity of the technique to in-plane spin-related properties is a powerful tool for the investigation of the in-plane component of the spin polarization in MQWs, which is otherwise commonly inaccessible

Acute outcome after a single cryoballoon ablation: Comparison between Arctic Front Advance and Arctic Front Advance PRO

BACKGROUND: The novel fourth-generation cryoballoon (CB4) potentially allows for enhanced catheter maneuverability and more frequent capture of pulmonary vein (PV) potentials which can be used to monitor real-time PV isolation (PVI). The aim of our study is to compare the acute procedural endpoints between the CB4 and second-generation cryoballoon (CB2). METHODS: A single-center retrospective chart review was used to examine 50 consecutive patients with drug-refractory atrial fibrillation undergoing CB4-based PVI. Procedural data and acute success of these patients were compared to 50 propensity-matched controls who underwent cryoballoon ablation procedure using CB2. RESULTS: Procedures performed with the CB4 showed significant shorter fluoroscopy time (14.8 \ub1 5.5 vs 18.0 \ub1 6.5 minutes, P = .04), shorter procedure time (58.3 \ub1 15.7 vs 65.3 \ub1 21 minutes, P = .13), and shorter total ablation time (10.8 \ub1 1.5 vs 13.8 \ub1 1.9 minutes, P = .42). The real-time PVI visualization rate was 33.3% in the CB2 group and 74.7% in the CB4 group (P < .001). CB4 was correlated to significant increase of acute real-time recordings with regard to all the single PV (left superior PV: 58% vs 84%, P = .02; left inferior PV: 26% vs 71%, P = .001; right superior PV 29% vs 61%, P = .01; and right inferior PV 19% vs 58%, P = .002). CONCLUSION: The CB4 was more often able to capture real-time recordings of PV potentials and the subsequent acute PV isolation