Estudio de la movilidad de venenos quemables en el sistema Zr-Nb-Er-U
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Comisión Nacional de Energía Atómica. Gerencia Área Académica. Gerencia Instituto Sabato
Universidad Nacional San Martin. Instituto de tecnología Sabato
Universidad Nacional San Martin. Instituto de tecnología Sabato
Resumen
En el contexto energético global, es importante que cada una de las fuentes de energía, además de ser confiables, sean económicamente competitivas. En este sentido, uno de los factores importantes para disminuir el precio de la energía eléctrica producida por reactores nucleares de agua liviana (LWR) es la prolongación del ciclo de operación. Una de las propuestas para lograrlo es el aumento de la concentración de 235U en las pastillas combustibles, esto aumentaría el tiempo entre recambios. En el marco del desarrollo de nuevos elementos combustibles para reactores LWR, surgieron propuestas que incorporan Er en la vaina del elemento combustible como veneno quemables. Por tanto, surge la necesidad de estudiar en profundidad el sistema ternario Er-Nb-Zr. Ante la falta de datos correspondientes al sistema mencionado, esta tesis se propuso estudiar, principalmente, la interacción vía difusión de los elementos que conforman el sistema. El trabajo está dividido en dos partes. Primero, para estudiar la interacción de los elementos vía difusión en el sistema, se prepararon los pares de difusión Er/Zr y Er/Zr20Nb, los mismos fueron caracterizados mediante diferentes técnicas (Microscopía óptica, SEM/EDS, LIBS, microsonda/WDS) y se obtuvieron valores de coeficientes de difusión representativos de cada una de las experiencias. Segundo, con el objetivo de estudiar las fases presentes en el sistema ternario Er-Nb-Zr, se prepararon, homogeneizaron y caracterizaron aleaciones ternarias con distintas composiciones. Adicionalmente, se estudiaron fenómenos propios de la técnica LIBS. Esto permitió la validación de la técnica para ser utilizada en el estudio de experiencias de difusión en este sistema y aportó datos importantes sobre la relación entre intensidad espectral y concentración de Er en Zr20Nb.
In the global energy context, it is important that each of the energy sources, in addition to being reliable, is economically competitive. In this sense, one of the important factors to reduce the price of electrical energy produced by light water nuclear reactors (LWR) is the extension of the operation cycle. One of the proposals to achieve this is to increase the concentration of 235U in the fuel tablets, this would increase the time between replacements. Within the framework of the development of new fuel elements for LWR reactors, proposals have emerged that incorporate Er in the sheath of the fuel element as a burnable poison. Therefore, the need arises to study the Er-Nb-Zr ternary system in depth. Given the lack of data corresponding to the aforementioned system, this thesis aimed to study, mainly, the interaction via diffusion of the elements that make up the system. The work is divided into two parts. First, to study the interaction of the elements via diffusion in the system, the Er/Zr and Er/Zr20Nb diffusion pairs were prepared, they were characterized using different techniques (Optical microscopy, SEM/EDS, LIBS, microprobe/WDS). and values of diffusion coefficients representative of each of the experiences were obtained. Second, with the objective of studying the phases present in the Er-Nb-Zr ternary system, ternary alloys with different compositions were prepared, homogenized and characterized. Additionally, phenomena specific to the LIBS technique were studied. This allowed the validation of the technique to be used in the study of diffusion experiences in this system and provided important data on the relationship between spectral intensity and concentration of Er in Zr20Nb.
In the global energy context, it is important that each of the energy sources, in addition to being reliable, is economically competitive. In this sense, one of the important factors to reduce the price of electrical energy produced by light water nuclear reactors (LWR) is the extension of the operation cycle. One of the proposals to achieve this is to increase the concentration of 235U in the fuel tablets, this would increase the time between replacements. Within the framework of the development of new fuel elements for LWR reactors, proposals have emerged that incorporate Er in the sheath of the fuel element as a burnable poison. Therefore, the need arises to study the Er-Nb-Zr ternary system in depth. Given the lack of data corresponding to the aforementioned system, this thesis aimed to study, mainly, the interaction via diffusion of the elements that make up the system. The work is divided into two parts. First, to study the interaction of the elements via diffusion in the system, the Er/Zr and Er/Zr20Nb diffusion pairs were prepared, they were characterized using different techniques (Optical microscopy, SEM/EDS, LIBS, microprobe/WDS). and values of diffusion coefficients representative of each of the experiences were obtained. Second, with the objective of studying the phases present in the Er-Nb-Zr ternary system, ternary alloys with different compositions were prepared, homogenized and characterized. Additionally, phenomena specific to the LIBS technique were studied. This allowed the validation of the technique to be used in the study of diffusion experiences in this system and provided important data on the relationship between spectral intensity and concentration of Er in Zr20Nb.