Análise físico-química e térmica de revestimentos nucleares a base de FeCrAl tolerantes a acidentes

Abstract

In order to increase safety for energy production in nuclear power reactors of the LWR type, new claddings, more efficient than the current one in terms of resistance to oxidation and chemical stability, are studied. In order to gather materials with these characteristics, the class of Accident Tolerant Fuel - ATF was created. The proposals are to replace the cladding or fuel pellet. The objective of this work is to evaluate the feasibility of replacing the current cladding, Zircaloy-4, with materials considered ATFs. Initially, composites of silicon carbide and metallic alloys based on iron, chromium and aluminum were characterized. Subsequently, 4 different iron-based alloys with different levels of chromium and aluminum were compared, as well as additions of other elements in lower levels. The comparison was made considering density, thermal expansion, thermal conductivity and specific heat. These same characteristics were used to establish a comparison between FeCrAl and Zircaloy-4 alloys. A comparative analysis was also carried out between FeCrAl and Zircaloy-4 alloys considering the thermal behavior of the materials. For this purpose, data obtained through simulations using the RELAP5-3D code were used, in which nodalization based on ANGRA II FSAR. The simulations were carried in steady state and in transient state of the Loss of Flow Accident - LOFA to evaluate the thermal behavior of the cladding and the fuel pellet. The physical-chemical properties were used to interpret the thermal behavior. The FeCrAl alloys presented similar results. Furthermore, it was possible to conclude that even at low levels the addition of other elements causes changes in the thermal properties of the material, in the case of FeCrAl alloys, compositions that also contained molybdenum, silicon and yttrium were studied. Through the study was possible to evaluate the viability for replace Zircaloy-4 by any of the 4 alloys proposed in the work because there are notable similarities in the behavior of the materials, the alloys presented promising results to replace the traditional material.