Abstract
This research focuses on safety criteria for the design of high flux research reactors with downflow systems. Generally, critical heat flux must be considered during the design of the reactor system. The Sudo93 correlation is widely used for prediction of critical heat flux due to its wide applicability for high flux research reactors. In addition, high flux research reactors typically operate under low pressure conditions and they are prone to various flow instabilities especially under accident conditions. Instabilities are likely to cause premature critical heat flux, and thus the onset of flow instability must be given enough attention. The onset of flow instability can be predicted by Whittle-Forgan correlation, Saha-Zuber correlation or Dougherty correlation. To investigate the relationship between critical heat flux predicted by Sudo93 correlation and the onset of flow instability, the critical heat flux databases of Sudo85 and Sudo93 correlations are studied and analyzed. It’s found that the critical heat flux databases contain not only critical heat flux of stable flow but also critical heat flux of unstable flow, which means that critical heat flux predicted by Sudo93 correlation may be affected by flow instabilities. Furthermore, Sudo93 correlation is used to deal with experimental data of the onset of flow instability. It’s found that Sudo93 can predict the onset of flow instability for downward flow. To account for this finding, Sudo93 correlation is compared with Dougherty correlation and Whittle-Forgan correlation. This paper finds that Sudo93 correlation has the similar characteristics with Dougherty correlation and Whittle-Forgan correlation. Besides, the uncertainty of Sudo93 correlation can be accounted for from the perspective of onset of flow instability.
