Measurement of local mechanical properties for Cr-coated accident tolerant fuel cladding

Abstract

After the Fukushima accident, there has been motivation to develop accident tolerant fuel (ATF) cladding has been encouraged to meet increased need for safety under accident conditions. Many countries have focused on surface-modified Zr cladding such as Cr or Cr-Al alloy coated Zr-alloy cladding as a near-term application. In the case of coated cladding, there is no currently mechanical properties data measured by a traditional tensile test to describe the characteristics of coated layer directly due to its thin thickness. In this regard, we introduce small scale mechanical test techniques, nanoindentation tests and micro-pillar compression test, to evaluate the mechanical properties for thin coated layer. The results are presented for Cr-coated Optimized ZIRLOTM ATF claddings developed for a high oxidation resistance. From the small-scale tests, the mechanical behaviors including elastic modulus and yield strength were confirmed in both Cr and Zr layers. Their values were equivalent to that of bulk properties measured with conventional testing methods. This implies that the measured mechanical properties by the small-scale tests could represent the bulk properties and could be useful data for reliable fuel performance assessment for coated ATF cladding.