HOOP TENSILE STRENGTH OF CERAMIC MATRIX COMPOSITE TUBES FOR LWRS APPLICATIONS USING ELASTOMERIC INSERTS: DRAFT ASTM TEST METHOD

摘要

The US DOE is evaluating the replacement of conventional zirconium-alloy fuel rod tubes in light water reactors (LWR) with those consisting of SiC/SiC CMCs to enhance fuel performance and accident tolerance. SiC/SiC CMCs show tolerance to the irradiation and chemical environments of LWRs. Failure modes in LWR fuel cladding include loss of gas tightness and mechanical integrity due to the build-up of internal gas pressure and the swelling of fuel pellets. Therefore, determination of the hoop tensile strength is critically important for evaluation of SiC/SiC CMC fuel claddings. A draft ASTM test method has been developed and submitted for full consensus balloting that uses axial compression of elastomeric inserts to introduce hoop stresses in composite tubular test specimens from the resulting internal pressures. This test method is based on sound, theoretical analysis of the stresses developed in tubes subjected to internal pressure over a finite length inside a semi-infinitely long tube. The draft ASTM test method contains test specimen dimensions, testing geometries, test conditions and results interpretation based on this theory and subsequent empirical tests applied to various materials and geometries. This test method (a.k.a., overhung tube method) is for material development, material comparison, material screening, material down selecting and quality assurance.