Extension of the Discrete-Ordinates Transport Solver IDT to Regular Two-Dimensional Triangular Meshes

In this work, the Integro-Differential Transport solver (IDT), which is one of the transport solvers available in the APOLLO3(R) lattice code, has been extended to handle 2D unstructured meshes. In particular, the previously implemented method of short characteristics (MoSC) used to solve for the spatial variable in the framework of an SN approach has been extended to triangular cells which represent the natural discretization for calculating the hexagonal lattices present in fast reactors. The coefficients of the collision-probability matrices have been evaluated by means of a split-cell algorithm, specialized for dealing with different orientations of the triangle with respect to each discrete ordinate of the SN sweeping. A new sweeping routine for unstructured meshes has been added to IDT. The correct implementation of the method and its robustness with respect to the skewness and the optical thickness of the triangle has been verified. The method of manufactured solutions has been employed to obtain a numerical estimate of the spatial convergence order of the method. The same version of the MoSC has then been implemented in MINARET, another solver available in APOLLO3(R). Finally, the modified IDT applied to an unstructured mesh for the C5G7 benchmark has been successfully benchmarked against MC calculations, and the modified MINARET has been applied to a neutron transport calculation for the RJH research reactor

Neutronic benchmark of the FRENETIC code for the multiphysics analysis of lead fast reactors

The FRENETIC code is being developed at Politecnico di Torino in the frame of the international effort for the deployment of lead fast reactors technology. FRENETIC is a multiphysics computational tool solving the neutronics and thermal-hydraulics equation at the full-core level, aiming at performing steady-state and time-dependent simulations in different conditions. In the present work, the validation activity of FRENETIC is carried forward by performing a benchmark against a reference computational model for the ALFRED design implemented in Serpent. Different core configurations in FRENETIC and different temperature distributions are considered, performing consistent comparisons between the two codes. All the results obtained show an extremely good agreement between the two models, implying that the ALFRED core can be well characterized by the FRENETIC code. The present study sets the basis for the future application of the code to simulate safety-relevant transients with FRENETIC

Functional safety assessment of a liquid metal divertor for the European demo tokamak

A reliable strategy for the heat exhaust problem for fusion reactors is among the milestones indicated in EUROfusion (2018). In a fusion reactor, the divertor targets are subject to extremely large heat and particle fluxes. For fusion to be economically feasible, these conditions must be withstood without damage for long time. The “baseline” strategy will be employed for the ITER experiment (which is being built in France) and is based on actively cooled tungsten monoblocks. It is unclear whether this strategy will extrapolate to a future fusion reactor (such as the EU-DEMO, whose pre-conceptual design is ongoing within the EUROfusion consortium). For this reason, alternative solutions are under study, which will eventually be tested in a dedicated experiment in Italy, namely the Divertor Tokamak Test (DTT). One possibility is to employ liquid metal divertors (LMDs), for which the plasma-facing surface is inherently self-healing and immune to thermo-mechanical stresses. Within the framework of the pre-conceptual design of an LMD for the EU-DEMO, safety issues need to be considered at an early stage. In this work we present a preliminary but systematic safety analysis for this system, by means of the Functional Failure Mode and Effect Analysis (FFMEA). The FFMEA allows to identify possible accident initiators for systems undergoing pre-conceptual design, when more specific safety evaluations (e.g. at the component level) are not possible, US Nuclear Regulatory Commission (2009). This is done by postulating the loss of a system function rather than a specific component failure, thus compensating for the lack of detailed design information. For each function, the potential causes of its loss, a plausible evolution and preventive and mitigative measures are investigated, possibly specifying the need for further information. The initiating events are grouped according to consequences and the plant response. For each group, the Postulated Initiating Event (PIE) is chosen. The PIEs list drives and limits the set of accidental scenarios which will undergo deterministic analysis in a successive phase of the work, in order to evaluate the capacity of the system to withstand/mitigate its consequences. This will assess whether safety limits are respected or whether additional safety provisions are required. From the PIEs list, the design basis accident (DBA) and beyond design basis accident (BDBA) will eventually be selected

Erratum: “Radiative heat load distribution on the EU-DEMO first wall due to mitigated disruptions” (Nuclear Materials and Energy (2020) 25, (S2352179120300971), (10.1016/j.nme.2020.100824))

The publisher regrets for the incorrect affiliation reported in the paper for one of the authors (S. Dulla, Politecnico di Torino). The publisher would like to apologise for any inconvenience caused

Radiative heat load distribution on the EU-DEMO first wall due to mitigated disruptions

The EU-DEMO First Wall (FW) will be a relatively thin structure. In order not to damage this layer, heat loads distributed onto the wall should be carefully controlled. In the case of transient events, as for example plasma disruptions, the steady-state heat load limit (~1-2 MW/m^2) can be largely exceeded for a timespan sufficiently long to cause damages. Therefore, when the control system detects an upcoming disruption, Shattered Pellet Injection (SPI) or Massive Gas Injection (MGI) mitigation techniques can be employed to inject impurities and switch off the plasma safely. In the present work, the Monte-Carlo ray-tracing code CHERAB is used to compute the radiative heat load distribution on the EU-DEMO Plasma Facing Components (PFCs) due to a mitigated plasma disruption. By applying ad-hoc techniques to improve the quality of the Monte Carlo calculation, we obtain a peak radiative load of ~490 MW/m^2 on the PFCs, which is ~25% lower than previous estimates

DTT - Divertor Tokamak Test facility: A testbed for DEMO

The effective treatment of the heat and power exhaust is a critical issue in the road map to the realization of the fusion energy. In order to provide possible, reliable, well assessed and on-time answers to DEMO, the Divertor Tokamak Test facility (DTT) has been conceived and projected to be carried out and operated within the European strategy in fusion technology. This paper, based on the invited plenary talk at the 31st virtual SOFT Conference 2020, provides an overview of the DTT scientific proposal, which is deeply illustrated in the 2019 DTT Interim Design Report

DTT - Divertor Tokamak Test facility - Interim Design Report

The “Divertor Tokamak Test facility, DTT” is a milestone along the international program aimed at demonstrating – in the second half of this century – the feasibility of obtaining to commercial electricity from controlled thermonuclear fusion. DTT is a Tokamak conceived and designed in Italy with a broad international vision. The construction will be carried out in the ENEA Frascati site, mainly supported by national funds, complemented by EUROfusion and European incentive schemes for innovative investments. The project team includes more than 180 high-standard researchers from ENEA, CREATE, CNR, INFN, RFX and various universities. The volume, entitled DTT Interim Design Report (“Green Book” from the colour of the cover), briefly describes the status of the project, the planning of the design future activities and its organizational structure. The publication of the Green Book also provides an occasion for thorough discussions in the fusion community and a broad international collaboration on the DTT challenge

A História da Alimentação: balizas historiográficas

Os M. pretenderam traçar um quadro da História da Alimentação, não como um novo ramo epistemológico da disciplina, mas como um campo em desenvolvimento de práticas e atividades especializadas, incluindo pesquisa, formação, publicações, associações, encontros acadêmicos, etc. Um breve relato das condições em que tal campo se assentou faz-se preceder de um panorama dos estudos de alimentação e temas correia tos, em geral, segundo cinco abardagens Ia biológica, a econômica, a social, a cultural e a filosófica!, assim como da identificação das contribuições mais relevantes da Antropologia, Arqueologia, Sociologia e Geografia. A fim de comentar a multiforme e volumosa bibliografia histórica, foi ela organizada segundo critérios morfológicos. A seguir, alguns tópicos importantes mereceram tratamento à parte: a fome, o alimento e o domínio religioso, as descobertas européias e a difusão mundial de alimentos, gosto e gastronomia. O artigo se encerra com um rápido balanço crítico da historiografia brasileira sobre o tema