Interação do hidrogênio com a microestrutura da liga Zr-Nb-Mn para aplicação em reatores nucleares

Abstract

Zirconium alloys are used for the manufacture of fuel rods for nuclear reactors due to their mechanical properties, low neutron absorption capacity and good corrosion resistance. Brazilian reactors are of the PWR type. Under operating conditions hydrogen derived from the radiolytic decomposition of water can be absorbed by the rod material forming zirconium hydride, a deleterious phase for the component. To increase the service lives of the rods, it is necessary to develop new alloys that reduce this effect. Computer simulation via Thermo-Calc R was used to aid the determination of the composition of three alloys: Zr -0.9Nb-0.1Mn; Zr-0.8Nb-0.2Mn and Zr-0.6Nb-0.4Mn. The Prisma mode was used to estimate the mean radius and volumetric fraction of the precipitation. Hydrogen interaction with the microstructure was analyzed by thermal desorption spectroscopy (TDS). This technique procced itself very efficient for the determination of diffusion parameters of these proposed alloys, diffusion coefficiente found are in the order of 10−12 m2/s, in accordance with the literature. The analysis of hydrides, performed by optical microscopy,revealed these were almost aligned. Results point out Mn as a promising addition element for zirconium alloys due to its potential in increasing mechanical resistance and hydrides orientation.