Modelling the reliability of sodium sulphur cells

Abstract

One of the main influences on the reliability of sodium sulphur cells has been identified to be the cracking of beta alumina ceramic. Several ceramic degradation mechanisms have been proposed; flaw-dependent, subcritical crack growth, stress corrosion cracking and progressive degradation mechanisms. These are reviewed in the paper. Reliability models based on these mechanisms are considered, and methods to distinguish between the models are developed. None of the models seems clearly to account for the empirical results obtained. The authors develop an alternative model. The method developed may be used for other similar processes.