Creep and Creep-Rupture Properties of the Nuclear Fuel Cladding Tube for Fast Breeder Reactor

Abstract

For the design and fabrication of the experimental fast breeder reactor it is desirable to obtain the creep and creep-rupture properties of the domestic tubes of 316 stainless steel with nominal dimension of 5.6mm inside diameter and 0.35mm wall thickness, that will carry nuclear fuel.The creep rupture tests under internal gas pressure and creep and creep-rupture tests under uniaxial tension have been carried out on two kinds of these tubes, one of which was approximately 6% cold-drawn and the other was approximately 18% cold-drawn, in unirradiated and atmospheric conditions at test temperatures of 550°C, 600°C, 650°C and 700°C.The results obtained are summarized as follows:(1) The regression curves for the creep-rupture data obtained from the internal pressure tests and uniaxial tension tests showed points of bend at the pressure of 360kg/cm2 and stress of 30kg/mm2 when the Larson-Miller parameter method was applied.(2) Compared with ISO's and NRIM's data, the present data for uniaxial tension tests showed a little greater creep-rupture strength for 6% cold-drawn tubes and definitely greater creep-rupture strength for 18% cold-drawn tubes.(3) The creep-rupture strength of 18% cold-drawn tubes is generally greater than that of 6% cold-drawn tubes. However, the creep-rupture curves for the two kinds of tubes tended to approach each other when the temperature was raised from 600°C to 700°C and the test time was prolonged.(4) The data for creep-rupture tests under internal pressure nearly agreed with those for uniaxial tension tests at stresses less than 30kg/mm2, when the hoop stress of internally pressurized specimens was calculated by the mean diameter formula.