Study of the Mechanical Properties of Shell of Fuel Elements from Zr1% Nb Alloys at Radial Stresses Similar to Reactor Conditions

Abstract

When determining the mechanical properties of ring specimens, a feature of a uniaxial (standard) loading scheme is that the method of applying a load to a specimen is somewhat remote from that to which the pipe walls can be subject in real operating conditions, in particular, these are tubes of fuel element shells. As an alternative loading method, the method of strain of an ring specimen on a cylindrical rod was considered and tested. By compressing the cylindrical rod from the ends, which in this case expanded and exerted pressure on the inner walls of the ring specimen in the radial direction, the specimen was deformed. The plasticity of fuel element shells made of Zr-1%Nb alloy on ring specimens under different loading methods is evaluated: uniaxial tension on half-disk supports, on a cylindrical rod, and on a tapered rod. Uniaxial tensile strain was determined in accordance with the normative documentation for the test method. When testing on a tapered rod, a specimen with a thinned working part was used. For the proposed loading method, the radial strain was measured by the change in the sample diameter. The results of testing the samples on a cylindrical rod were compared with the previously obtained results on half-disc supports and a tapered rod. The method of deformation of a ring specimen on a cylindrical rod makes it possible to obtain higher values of plasticity in comparison with uniaxial tension. In addition, the proposed method of deformation of a sample on a cylindrical rod, in contrast to uniaxial tension, in terms of the nature of the stress state, approaches to the operating reactor conditions.