Deformation behaviour of Zr-2.5 wt percent Nb pressure tubes under internal pressurization and ramp temperature conditions

The deformation behaviour of 0.6 m long Zr-2.5 wt percent Nb pressure tube specimens deformed under internal pressurization and ramp temperature conditions has been studied. Both inert gas and steam have been used as the pressurizing medium. Controlled heating rates in the range 1-25 K/s and internal pressures in the range 0-12 MPa have been investigated. It was observed that, except at the very high test pressures, the samples deformed to circumferential strains well in excess of the nominal 'contact' strain of 0.18 before possible rupture. Over the time scale of the biaxial tests carried out, the effect of steam on deformation behaviour appeared to be minimal. It was also found that the major features of the biaxial deformation behaviour can be investigated, at least qualitatively, by carrying out uniaxial tensile tests. However, detailed analysis of uniaxial and biaxial data showed that there were several major differences between the two types of data. These differences are discussed in considerable detail in the present report