Overview of Critical Heat Flux – Mysterious World of CHF

This seminar provides an overview of the most essential aspects of the critical heat flux (CHF) research applicable to fuel channels (CANDU reactors) and fuel assemblies (LWRs). It is based on 10-year experience of the author who worked for Atomic Energy of Canada Ltd. (AECL) at the Chalk River Nuclear Laboratories. It starts with an introduction to pool boiling and its crisis followed by two-phase flow structures and two extreme types of CHF mechanisms. The seminar presents the CHF experimental effort carried out world-wide using relatively the simplest flow geometry (tubular) and the cheapest setups. Then, in a more complex flow geometry (annular) ending in the most complex one (fuel bundles and assemblies) and the most expensive setups. Then it focuses on CHF prediction methods used in the safety computer thermohydraulic codes for design and licensing purposes. To complement the seminar the CHF enhancement methods and the CHF fluid-to-fluid modelling are discussed as well.  Still this CHF world remains mysterious and requires further research effort.