Numerical modelling and experimental validation
Designing efficient energy production systems largely benefits from optimized multi-physics modelling methodologies and code development competences. To simulate the behavior of a generic system in any engineering application (and the synergies among its sub-systems), dedicated numerical models are continuously developed, implemented and validated by the DAF group.
These cover a wide spectrum of multi-dimensional, time-dependent physics problems, including electromagnetism, mass and energy transport, plant integral modelling and constrained system optimization. These involve a broad spectrum of cross-cut skills, comprising mathematical and numerical conception of the models, code development and validation methods.
In the DAF group, a variety of physics and engineering problems are routinely implemented through optimized object-oriented C++, MATLAB and Python computer programs and validated against experimental or numerical reference results. Accordingly, the validation techniques are continuously refined and adapted to the problem.
MIRA: Modular Integrated Reactor Analysis Code
According to the European Roadmap of Fusion Energy , the development and the operation of a demonstration power plant (DEMO) is the key step towards establishing nuclear fusion as a sustainable energy source. A fusion reactor based on magnetic confinement is a notably complex device withstanding challenging nuclear, thermal and electromagnetic loads. Hence, a reliable multi-physics and holistic approach is of paramount importance for an optimal reactor design. The design of the EU-DEMO is carried out by the EUROfusion Consortium, and the selection of the DEMO baseline is led by fusion systems-codes: computational tools that simulate the physics and engineering features of a Fusion Power Plant (FPP).
The DAF group is involved in several EUROfusion activities associated with the design of the EU-DEMO reactor. In this framework, the multi-fidelity system/design tool MIRA (Modular Integrated Reactor Analysis) has been developed  and is continuously under improvement. With the objective of solving the utmost FPP problems, it incorporates diverse coupled mathematical models into a unique computing environment. These include magnetic equilibrium and core transport physics for a tokamak plasma, neutron & photon radiation transport, magnetic and engineering characterization of the superconducting coils system, and power & fuel cycle balances for reactor-plant integration.
Figure 1 Schematic work-flow of a typical MIRA analysis
FUS-TPC: Tritium Permeation Code for fusion applications
The fuel of a fusion reactor is composed of hydrogen isotopes, such as deuterium and tritium. Under high-temperature fields, hydrogen permeates through structural materials, thereby leading to unavoidable losses, posing concerns on fuel economy and radiological safety of a fusion plant. Reliable quantification of tritium inventories and flows across the sub-systems is mandatory for the safety licensing and for the design of a fusion power plant. The fusion tritium permeation code FUS-TPC has been developed in collaboration with ENEA-Politecnico di Torino [3,4] and, within the frame of EUROfusion safety activities, is continuously improved in the DAF group.
FUS-TPC can map the flows of tritium generated inside the tritium breeder (or breeding blanket, BB) and extracted in the tritium extraction and removal system (TER). Most importantly, it quantifies the tritium flows towards the environment through steels in the BB cooling structures, intermediate heat exchangers (IHX) and steam generators (SG). FUS-TPC relies on a multi-species and quasi 2D time-dependent mass transport model, including co-permeation with different permeable gaseous species and chemical reaction rates. It is based on a Matlab/Simulink environment and it allows for a definition of an arbitrary number of plant sub-systems, atomic and chemical species, and source profiles.
Figure 2 Schematic view of FUS-TPC plant nodalization to quantify the tritium flows across the breeding blanket, tritium extraction and removal systems and other connected ancillary components
Nowadays, computational electromagnetics is widely applied for the design and analysis of electromagnetic devices. In this contest, the class of electromagnetic (EM) phenomena occurring in a fusion reactor based on the tokamak concept is so wide that a variety of models and related numerical techniques are needed to give a satisfactory solution to the main design problems. During the past years, the DAF group gained main competencies in the EM analyses of fusion machines using Finite Element codes (e.g. ANSYS). Main applications are related to low-frequency analysis of in-vessel components, as the Breeder Blanket System, to investigate electrical currents and magnetic field distribution (and thus EM loads) during normal and off-normal operations and in presence of nonlinear magnetic material. Ad-hoc macros in different scripting languages are usually developed to overcome limitations of the used software.
- EUROfusion. European Research Roadmap to the Realisation of Fusion Energy, Garching, Germany, 2018. https://www.euro-fusion.org/eurofusion/roadmap.
- F. Franza. Development and Validation Development and Validation of a Computational Tool for Fusion Reactors' System Analysis, PhD thesis, Karlsruhe Institute of Technology, June 2019. https://publikationen.bibliothek.kit.edu/1000095873
- F. Franza, A. Ciampichetti, I. Ricapito and M. Zucchetti. "A model for tritium transport in fusion reactor components: The FUS-TPC code," Fusion Engineering and Design, vol. 87, pp. 299 - 302, 2012.
- F. Franza, L. V. Boccaccini, A. Ciampichetti and M. Zucchetti. "Tritium transport analysis in HCPB DEMO blanket with the FUS-TPC code," Fusion Engineering and Design, vol. 88, p. 2444–2447, 2013