Integration of OpenCalphad thermo-chemical solver in PLEIADES/ALCYONE fuel performance code

International audienceThe ALCYONE fuel performance code, co-developed by CEA, EDF and Framatome, within the PLEIADES software environment provides a multidimensional modeling for detailed analysis of PWR fuel elements behavior under irradiation [1]. Iodine-Stress Corrosion Cracking is one of the physical phenomena of major interest for cladding design and long term operation of PWRs. In a first step towards I-SCC simulations, the thermochemical code ANGE was integrated in PLEIADES [2]. ANGE, a modified version of SOLGASMIX, enables to compute thermo-chemical equilibria using the TBASE database [3] and associate species description [4] but has some limitations and cannot be used to solve chemical systems based on the Compound Energy Formalism, such as the one proposed in the TAF-ID [5]. Consequently, a robust, efficient and free numerical tool, OpenCalphad [6], was introduced in PLEIADES. In this work, we focus our presentation on the calculation of complex multi-component systems representative of fuel elements behavior under irradiation. From the results of in-reactor power transient calculations (1D-2D-3D), we show that ALCYONE/OpenCalphad is much faster than ALCYONE/ANGE. We note a decrease of the CPU time by almost a factor 4 that can be explained by the OpenCalphad solver itself and by a set of numerical strategies implemented to start a thermodynamic calculation on a mesh node by using another calculated equilibrium as an initial solution. We also show through first results the capacity and the robustness of the ALCYONE/OpenCalphad coupling to do in-reactor power transients calculations (1D-2D-3D) using the TAF-ID. In the latter, the models are more complicated and the possible phases are greater in number than in the TBASE database. For calculations performed in the same conditions as those done with the TBASE database, we note a slight increase of the CPU time that can be reduced by calculating several thermodynamic equilibria simultaneously with a multithread approach.References[1] V. Marelle, et al. New developments in ALCYONE 2.0 fuel performance code, Top Fuel, Boise ID (2016)[2] B. Baurens, et al., J. Nucl. Mater. 452 (2014) 578[3] E.H.P. Cordfuncke, R.J.M. Konings, J. Phase Equilibria 14 [4] (1993)[4] T.M. Besmann, Comprehensive Nucl. Mater. 1.17 (2012)[5] C. Gueneau et al., J. Nucl. Mater. 419 (2011) 147[6] B. Sundman, et al, Integ. Mater. Manuf. Innov. 4 (2015)

1D modelling and preliminary analysis of the coupled DYNASTY–eDYNASTY natural circulation loop

In the continuous strive to improve the safety of current-generation and next-generation nuclear power plants, natural circulation can be used to design passive safety systems to remove the decay heat during the shutdown. The Molten Salt Fast Reactor (MSFR) is a peculiar type of Gen-IV nuclear facility, where the fluid fuel is homogeneously mixed with the coolant. This design leads to natural circulation in the presence of an internally distributed heat source during the shutdown. Furthermore, to shield the environment from the highly radioactive fuel, an intermediate loop between the primary and the secondary loops, able to operate in natural circulation, is required. To analyze the natural circulation with a distributed heat source and to study the natural circulation of coupled systems and the influence of the intermediate loop on the behaviour of the primary, Politecnico di Milano designed and built the DYNASTY-eDYNASTY facility. The two facilities are coupled with a double-pipe heat exchanger, which siphons heat from DYNASTY and delivers it to the eDYNASTY loop. This work focuses on modelling the coupled DYNASTY-eDYNASTY natural circulation loops using DYMOLA2023((R)), an integrated development environment based on the Modelica Object-Oriented a-causal simulation language. The 1D Modelica approach allows for building highly reusable and flexible models easing the design effort on a complex system such as the DYNASTY-eDYNASTY case without the need to rewrite the whole model from scratch. The coupled models were developed starting from the already-validated single DYNASTY model and the double-pipe heat exchanger coupling. The models were tested during the whole development process, studying the influence of the numerical integration algorithm on the simulation behaviour. A preliminary analysis of both the adiabatic and the heat loss models analyzed the effect of the secondary natural circulation loop on the behaviour of the DYNASTY loop. The simulation results showed that the eDYNASTY loop dampens the behaviour of the primary DYNASTY loop. Furthermore, a parametric analysis of the DYNASTY and the eDYNASTY coolers highlighted the influence of the cooling configuration on the facility's behaviour. Finally, the simulation results identified the most critical aspects of the models in preparation for an experimental comparison

Development of an OpenFOAM multiphysics solver for solid fission products transport in the Molten Salt Fast Reactor

The analysis of innovative reactor concepts such as the Molten Salt Fast Reactor (MSFR) requires the development of new modeling and simulation tools. In the case of the MSFR, the strong intrinsic coupling between thermal-hydraulics, neutronics and fuel chemistry has led to the adoption of the multiphysics approach as a state-of-the-art paradigm. One of the peculiar aspects of liquid-fuel reactors such as the MSFR is the mobility of fission products (FPs) in the reactor circuit. Some FP species appear in form of solid precipitates carried by the fuel flow and can deposit on reactor boundaries (e.g., heat exchangers), potentially representing design issues related to the degradation of heat exchange performance or radioactive hotspots. The integration of transport models for solid particles in multiphysics codes is therefore relevant for the prediction of deposited fractions. To this aim, we develop a multiphysics solver based on the OpenFOAM library to address the issue of solid fission products transport. Single-phase incompressible thermal hydraulics are coupled with neutron diffusion, and advection-diffusion-decay equations are implemented for fission products concentrations. Particle deposition and precipitation are considered as well. The developed solver is tested on two different MSFR application to showcase the capabilities of the solver in steady-state simulation and to investigate the role of precipitation and turbulence modeling in the determination of particle concentration distributions

Characterization of varroa destructor mites in Cuba using mitochondrial and nuclear markers

Varroa destructor has been present in Cuba since 1996, but without the use of acaricidal infestation rates remain at very low levels. The presence of Korean haplotype mites was described in 2007, but there is no information regarding the introgression of the less virulent Japanese haplotype that could account for a low pathogenicity of the mite. In this research, we carried out molecular characterization of Cuban Varroa mites through mitochondrial DNA and hypervariable nuclear loci. We applied an alternative RFLP tech-nique and found that all the analyzed samples corresponded to Korean haplotypes. We analyzed the three STRs loci VD112, VD114 and VD016, previously described as highly variable and found new alleles in all of them, with an absolute allele size very different to those reported worldwide. We also detected genic and genotypic differentiation be-tween samples from two nearby locations (P=0.08). We also tested a new RFLP method for mite haplotype discrimination with an intra-reaction positive control of digestion

Neighbours’ Conviviality Without Gatherings. Social Streets in Times of Lockdown

The lockdown period imposed by Italian institutions to their citizens from March to May 2020 to contrast the Coronavirus diffusion had a very deep impact on people’s sociality and their daily practices. However, informal groups and associations tried to keep them alive with the help of digital communication technologies, used to enhance conviviality and to support and organize forms of mutual help. This article aims to analyse how Social Streets promoted sociality and mutual help among neighbours in time of lockdown, and how Streeters, here defined as people who are at least inscribed at the Facebook group of their Social Street, have profited from the possibility to have at their disposal an online social place where to interact and be informed about the possibility of giving and receiving help. This article draws from data gathered through two online surveys, administered, respectively, during lockdown phase in the second half of April (838 respondents) and in June 2020, after its end (371 respondents). Our results show that, after seven years since their foundation in 2013, Social Streets still play a pivotal role in the neighbourhood. During lockdown, they gave a contribution in keeping neighbours informed about what was going on in the neighbourhood, in sustaining and producing convivial ties, in organizing mutual help services. In the hard time of lockdown, when most of the usual habits and practices were forcefully suspended, Social Streets proved very important in setting a cognitive, emotional, and organizational framework inside which conviviality and collaboration among neighbours could find greater plausibility

A multi-targeted drug candidate with dual anti-HIV and anti-HSV activity

Human immunodeficiency virus (HIV) infection is often accompanied by infection with other pathogens, in particular herpes simplex virus type 2 (HSV-2). The resulting coinfection is involved in a vicious circle of mutual facilitations. Therefore, an important task is to develop a compound that is highly potent against both viruses to suppress their transmission and replication. Here, we report on the discovery of such a compound, designated PMEO-DAPym. We compared its properties with those of the structurally related and clinically used acyclic nucleoside phosphonates (ANPs) tenofovir and adefovir. We demonstrated the potent anti-HIV and -HSV activity of this drug in a diverse set of clinically relevant in vitro, ex vivo, and in vivo systems including (i) CD4⁺ T-lymphocyte (CEM) cell cultures, (ii) embryonic lung (HEL) cell cultures, (iii) organotypic epithelial raft cultures of primary human keratinocytes (PHKs), (iv) primary human monocyte/macrophage (M/M) cell cultures, (v) human ex vivo lymphoid tissue, and (vi) athymic nude mice. Upon conversion to its diphosphate metabolite, PMEO-DAPym markedly inhibits both HIV-1 reverse transcriptase (RT) and HSV DNA polymerase. However, in striking contrast to tenofovir and adefovir, it also acts as an efficient immunomodulator, inducing β-chemokines in PBMC cultures, in particular the CCR5 agonists MIP-1β, MIP-1α and RANTES but not the CXCR4 agonist SDF-1, without the need to be intracellularly metabolized. Such specific β-chemokine upregulation required new mRNA synthesis. The upregulation of β-chemokines was shown to be associated with a pronounced downmodulation of the HIV-1 coreceptor CCR5 which may result in prevention of HIV entry. PMEO-DAPym belongs conceptually to a new class of efficient multitargeted antivirals for concomitant dual-viral (HSV/HIV) infection therapy through inhibition of virus-specific pathways (i.e. the viral polymerases) and HIV transmission prevention through interference with host pathways (i.e. CCR5 receptor down regulation)

Are Urologists Ready for Interpretation of Multiparametric MRI Findings? A Prospective Multicentric Evaluation

Aim: To assess urologists’ proficiency in the interpretation of multiparametric magnetic resonance imaging (mpMRI). Materials and Methods: Twelve mpMRIs were shown to 73 urologists from seven Italian institutions. Responders were asked to identify the site of the suspicious nodule (SN) but not to assign a PIRADS score. We set an a priori cut-off of 75% correct identification of SN as a threshold for proficiency in mpMRI reading. Data were analyzed according to urologists’ hierarchy (UH; resident vs. consultant) and previous experience in fusion prostate biopsies (E-fPB, defined as <125 vs. ≥125). Additionally, we tested for differences between non-proficient vs. proficient mpMRI readers. Multivariable logistic regression analyses (MVLRA) tested potential predictors of proficiency in mpMRI reading. Results: The median (IQR) number of correct identifications was 8 (6–8). Anterior nodules (number 3, 4 and 6) represented the most likely prone to misinterpretation. Overall, 34 (47%) participants achieved the 75% cut-off. When comparing consultants vs. residents, we found no differences in terms of E-fPB (p = 0.9) or in correct identification rates (p = 0.6). We recorded higher identification rates in urologists with E-fBP vs. their no E-fBP counterparts (75% vs. 67%, p = 0.004). At MVLRA, only E- fPB reached the status of independent predictor of proficiency in mpMRI reading (OR: 3.4, 95% CI 1.2–9.9, p = 0.02) after adjusting for UH and type of institution. Conclusions: Despite urologists becoming more familiar with interpretation of mpMRI, their results are still far from proficient. E-fPB enhances the proficiency in mpMRI interpretation

CD49a Expression Defines Tissue-Resident CD8+ T Cells Poised for Cytotoxic Function in Human Skin

Tissue-resident memory T (Trm) cells form a heterogeneous population that provides localized protection against pathogens. Here, we identify CD49a as a marker that differentiates CD8(+) Trm cells on a compartmental and functional basis. In human skin epithelia, CD8(+)CD49a(+) Trm cells produced interferon-γ, whereas CD8(+)CD49a(−) Trm cells produced interleukin-17 (IL-17). In addition, CD8(+)CD49a(+) Trm cells from healthy skin rapidly induced the expression of the effector molecules perforin and granzyme B when stimulated with IL-15, thereby promoting a strong cytotoxic response. In skin from patients with vitiligo, where melanocytes are eradicated locally, CD8(+)CD49a(+) Trm cells that constitutively expressed perforin and granzyme B accumulated both in the epidermis and dermis. Conversely, CD8(+)CD49a(–) Trm cells from psoriasis lesions predominantly generated IL-17 responses that promote local inflammation in this skin disease. Overall, CD49a expression delineates CD8(+) Trm cell specialization in human epithelial barriers and correlates with the effector cell balance found in distinct inflammatory skin diseases

Red blood cell tension protects against severe malaria in the Dantu blood group.

Malaria has had a major effect on the human genome, with many protective polymorphisms-such as the sickle-cell trait-having been selected to high frequencies in malaria-endemic regions1,2. The blood group variant Dantu provides 74% protection against all forms of severe malaria in homozygous individuals3-5, a similar degree of protection to that afforded by the sickle-cell trait and considerably greater than that offered by the best malaria vaccine. Until now, however, the protective mechanism has been unknown. Here we demonstrate the effect of Dantu on the ability of the merozoite form of the malaria parasite Plasmodium falciparum to invade red blood cells (RBCs). We find that Dantu is associated with extensive changes to the repertoire of proteins found on the RBC surface, but, unexpectedly, inhibition of invasion does not correlate with specific RBC-parasite receptor-ligand interactions. By following invasion using video microscopy, we find a strong link between RBC tension and merozoite invasion, and identify a tension threshold above which invasion rarely occurs, even in non-Dantu RBCs. Dantu RBCs have higher average tension than non-Dantu RBCs, meaning that a greater proportion resist invasion. These findings provide both an explanation for the protective effect of Dantu, and fresh insight into why the efficiency of P. falciparum invasion might vary across the heterogenous populations of RBCs found both within and between individuals.JCR, AM and DK were supported by the Wellcome Trust (206194/Z/17/Z). MPW is funded by a Wellcome Senior Fellowship (108070). TNW is funded through Fellowships awarded by the Wellcome Trust (091758 and 202800). SNK is supported by the Wellcome Trust-funded Initiative to Develop African Research Leaders (IDeAL) early-career postdoctoral fellowship (107769/Z/10/Z), supported through the DELTAS Africa Initiative (DEL-15-003). The Wellcome Trust provides core support to The KEMRI/Wellcome Trust Research Programme, Kilifi, Kenya (084535), Wellcome Sanger Institute, Cambridge, UK (206194/Z/17/Z) and the Wellcome Centre for Human Genetics, Oxford, UK (090532/Z/09/Z, 203141). PC is supported by the Engineering and Physical Sciences Research Council (EPSRC) (EP/R011443/1), and VI is supported by the EPSRC and the Sackler fellowship