Effect of temperature on the mechanical properties of HIMET fuel

Abstract

The mechanical properties of HIMET fuel for the small integrated reactors, SMART, like the reactors which change sea water to fresh water were investigated. The fundamental properties such as the microstructure of clad(Zr-1%Zb) and meat(37%U-Zr), hardness and texture of clad were observed before the tensile test which is the most important mechanical property of HIMET fuel. Tensile tests were performed to investigate the mechanical properties of Zr-1%Nb alloy and 37%U-Zr alloy used as HIMET fuel. A new tensile test system was equipped for the experiment at evaluated temperatures and for the protection of specimen against oxidation, The tensile tests were conducted at strain rate of 1×10-4/sec in the temperature range of 20 to 600℃. In case of Zr-1%Nb alloy, stress plateau due to β-Nb precipitates in α-Zr matrix and oxygen atom-dislocation interactions was observed. As shown in elongation-temperature curve of 37%U-Zr alloy, the appearance of brittle fracture was observed from RT to 200℃ but the increment of elongation was observed as test temperature increased. The above results confirmed that the most important parameters affecting tensile properties are specimen fabrication process, test temperature and strain rate. The flexural rigidity and standard deviation were assumed after the 3-point bending test of HIMET fuel, however the changes of flexural rigidity were very little with variation of loading rates.