BANDO PRIN 2022D. D. N. 104 DEL 2 FEBBRAIO 2022

TITOLO DEL PROGETTO: RaDAMES: RAdiation DAMagE in Structural material of fusion reactors under neutron irradiation: cross section measurements, possible mitigation strategies and material testing protocols

CODICE CUP B53D23005050006

Budget: € 65.098

P.I. o Responsabile U.R. Prof. Giuseppe Demelio

Altre Unità di Ricerca o eventuali Sub Unità Dott. Nicola colonna (INFN), Dott.ssa Annamaria Mazzone (CNR)

Breve descrizione del progetto
The project addressed the study of neutron-induced damage in structural materials intended for use in future fusion reactors. Its main focus was on gas production resulting from neutron-induced charged-particle emission reactions, which can significantly affect the long-term behaviour and reliability of materials exposed to fusion-relevant neutron fields. To tackle this issue, the project combined complementary experimental, computational, and diagnostic approaches. Experimental activities were mainly devoted to assessing the feasibility of measuring energy-dependent reaction cross sections at the CERN n_TOF facility. At the same time, Monte Carlo and molecular dynamics simulations were used to investigate neutron–material interactions and radiation damage mechanisms at different scales. Particular attention was given to tungsten, a key material for fusion applications, and to the formation of defects such as vacancies, interstitials, dislocation loops, and helium-related damage. In parallel, non-destructive thermal techniques were explored as possible tools for detecting irradiation-induced changes in material properties. The project was carried out by INFN, CNR, and Politecnico di Bari, each contributing specific expertise to the overall scientific objectives.

Finalità
The main objective of the project was to improve the understanding and assessment of neutron damage in materials used in fusion-reactor environments. A first goal was to verify whether neutron-induced charged-particle emission reactions could be measured accurately at the n_TOF facility, with particular reference to reactions relevant to gas production, tritium breeding, and material degradation. A second objective was to evaluate the predictive capability of molecular dynamics simulations in describing radiation damage at the atomic scale. These simulations were intended to provide insight into the formation, evolution, and stability of irradiation-induced defects in tungsten. A further aim was to investigate how such defects affect thermal and mechanical properties, which are crucial for the safe operation of fusion components. The project also sought to explore non-destructive diagnostic methods, especially stimulated thermography and pulsed laser techniques, as possible tools for detecting damage without compromising the material. Overall, the final purpose was to integrate experimental measurements, numerical modelling, and material-characterization methods in order to support the development of safer and more reliable materials for future fusion technologies.

Risultati attesi
The project was expected to provide a concrete demonstration of the feasibility of measuring neutron-induced charged-particle reactions at CERN n_TOF. This included the design, construction, and validation of a new detection system capable of identifying light charged particles emitted during neutron-induced reactions. Monte Carlo simulations were expected to support the experimental work by estimating detector efficiency, expected counting rates, and neutron-beam-induced background. The project also aimed to prepare the ground for future measurements on isotopes of specific interest for fusion applications, including materials relevant to tritium breeding and neutron damage in reactor blankets. On the modelling side, molecular dynamics simulations were expected to clarify the mechanisms through which neutron irradiation produces defects in tungsten and modifies its thermophysical properties. These results were intended to help connect atomistic damage processes with macroscopic material degradation. In addition, the project was expected to assess the potential of non-destructive thermal techniques for identifying irradiation-induced damage. More broadly, the expected outcome was a set of experimental and computational tools useful for future studies on structural materials for fusion reactors, together with scientific publications and open-access dissemination of the results.

Risultati raggiunti 
The project achieved significant results in all the main planned areas. An innovative solid-state detection system was developed, tested, and validated under neutron-beam conditions at the n_TOF facility. The apparatus proved capable of detecting and identifying light charged particles such as protons, deuterons, tritons, and alpha particles, with promising performance for future cross-section measurements. Validation measurements were performed using carbon reactions, and preliminary results confirmed the feasibility of the proposed experimental approach. GEANT4-based Monte Carlo simulations were successfully used to optimize the setup, estimate efficiencies, evaluate background, and plan future measurements. A proposal for measurements on lithium and beryllium isotopes, both relevant to fusion applications, was submitted and approved at CERN. In parallel, molecular dynamics simulations were successfully applied to tungsten in order to study radiation-induced defects and their effects on thermal transport. The simulations showed that defects such as helium-filled bubbles, vacancies, and dislocation loops can significantly reduce lattice thermal conductivity. The project also assessed non-destructive thermal methods, including pulsed laser approaches, as promising tools for evaluating irradiation-induced degradation. Overall, the activities were completed consistently with the approved work plan and provided a strong basis for further experimental campaigns, modelling studies, and diagnostic developments.