Displacement Damage and Self-Healing in High-Entropy Alloys: a TEM with in situ ion irradiation study

Recent developments in the field of materials for future nuclear fusion reactors have led to the design of innovative metallic alloys that can sustain their mechanical and structural properties under a wide variety of extreme conditions, such as fast neutrons (E <= 14 MeV) and alpha particle bombardment (4He with E up to ~ 3.5 MeV). High-Entropy Alloys (HEAs) are promising candidates for new concepts of nuclear reactors as they have mechanical properties and thermodynamic stability that is believed to be superior to conventional metallic alloys, although their radiation resistance is still a subject of intense research. The efforts to understand the behavior of HEAs under particle irradiation indicated a possible “self-healing” effect of radiation induced defects. In this report, a preliminary study using Transmission Electron Microscopy (TEM) with in situ ion irradiation was performed to investigate the formation and evolution of displacement damage in the microstructure of a FeCrMnNi HEA

Modelling a compact nuclear reactor for optimization studies in biological shielding in nuclear submarines.

A presente pesquisa apresenta o desenvolvimento de um modelo computacional de um reator nuclear térmico e compacto para estudos em optimização e avaliação de materiais inovadores para uma melhor efetividade da blindagem primária. Utilizou-se dois códigos de transporte nêutron-gama, o estatístico MCNP5 e o determinístico gem/EVENT: o primeiro para o design do PWR e o segundo para simular um modelo 1D do reator para estudar o comportamento de blindagem gama e de nêutrons para diversos materiais. Adicionalmente o MATLAB Optimization Toolbox foi utilizado para fornecer novas configurações geométricas optimizadas do modelo unidimensional do reator visando reduzir o volume e o peso das cascas da blindagem por meio de uma função custo/objetiva. Foi demonstrado no MCNP5 que a dose após a blindagem primária reduziu uma ordem de magnitude para o modelo optimizado utilizando-se um novo material compósito e o volume e o peso das cascas de blindagem foram reduzidos por um fator de 13%. Os resultados confirmam que os códigos nucleares podem ser executados paralelamente ao MATLAB com a intenção de se testar novos materiais para o propósito de optimização da blindagem da radiação em um reator PWR compacto e que materiais compósitos podem substituir os materiais de blindagem tradicionais sem o comprometimento da segurança da instalação nuclear.This research was focused to develop a computational model of a compact PWR to study optimization methods and evaluate innovative materials to enhance the biological shielding effectiveness. We used two radiation transport codes MCNP5 and GEM/EVENT: the first for the PWR design and the second one to simulate (in a 1D slab) several materials and shielding thickness behavior under gamma and neutron penetration. Additionally MATLAB Optimization Toolbox was used to provide new geometric configurations of the slab aiming to reduce the volume and weight of the walls by means of a cost/objective function. It is demonstrated in the MCNP5 that the dose rate after biological shielding has reduced by one order of magnitude for the optimized model with a new composite material (Ecomass) and the volume and weight of the shielding walls were reduced by 13% when we compare both sets. The results confirm that we can couple a deterministic and stochastic transport codes with MATLAB to test new materials in a very fast way for the purpose of radiation shielding optimization in common compact PWR. All this states that composite materials can replace (with advantages) traditional shielding materials without jeopardizing the nuclear power plant safety assurance