The Effect of air fraction in steam on the embrittlement of Zry-4 fuel cladding oxidized at 1273-1573 K

Negyesi, M.; Amaya, Masaki  

The paper deals with the effect of air fraction in steam on the embrittlement of Zry-4 fuel cladding exposed under steam-air atmospheres (air fractions of 10-100%) in the temperature range of 1273-1573 K. Ring compression tests were carried out in order to evaluate the embrittlement of fuel cladding. Furthermore, the microhardness of prior -phase was measured and fractured surfaces were observed under SEM. The degree of the embrittlement was discussed against the results of metallographic and hydrogen analyses. The microstructure and the hydrogen pick-up were substantially affected by nitride formation. Accelerated oxidation kinetics enhanced shrinking of the prior -region. The enhanced hydrogen absorption resulted in the increased microhardness of prior -phase. The degree of fuel cladding embrittlement, expressed by the plastic strain at failure and the maximum load, correlated well with the microhardness and the thickness of prior -phase.