Transient tube burst tests on fast reactor fuel cladding

Experimental results of transienst tube burst tests on tubing of three different austenitic stainless steels, Werkstoff no. 1.4970 (Sandvik 12R72HV), 1.4981 and 1.4988 (DIN classification), are reported. The tubing geometry is representative for the canning of the sodium cooled fast reactor SNR-300. The internal tube pressure ranged from 30 to 120 Kg/cm2. The heating rate was varied from 27 to 110degC/sec. Up to a heating rate of about 70degC/sec the failure temperatures can be reasonable well predicted by a secondary creep relation. The failure temperature of 1.4970 tubing is strongly influenced by the heating rate. This is much less the case for 1.4981 and 1.4988 tubing. The failure strains of the three tubings depend largely on failure temperature and except for material 1.4981, also on heating rate. Three different failure modes have been observed. It was recognized that the grain size plays a dominant role in the mode of failure. To some extent the failure mode also depend on the heating rate. The experiments performed so far do not give data on creep (strain) rate which seem to be indispensable in order to explain the discrepancies between the measured and calculated failure temperatures at high heating rates (> 70degC/sec.) and high internal tube pressures (> 45 Kg/cm2)