Assessment of the burnout phenomenon in the SAFARI-1

The analysis of transients for the SAFARI-1 research reactor is done using the RELAP5/SCDAPSIM Mod3.4 system code, while the analysis of critical phenomena associate with the Critical Heat Flux (CHF) is done using available correlations within the code, such as the AECL look-up tables, or from literature such as Sudo and Mishima correlations discussed and applied in this work. In this paper a proposal is made on the application of the Sudo scheme of correlations to predict CHF conditions, supplemented by the AECL look-up tables. The application was used to evaluate the low flow burnout phenomenon that may occur during the beyond design loss of flow accident. In applying the scheme and during the course of the transient, various validity and applicability checks were made on flow patterns and heat transfer conditions. These conditions (e.g. hot channel exit equilibrium quality, flow pattern, rate of variation of the channel inlet flow rate, and range of the experimental data) were selected on the basis of RELAP5/SCDAPSIM modelling of the experimental rig used by Sudo, observations made by the experimentalists, and our understanding of the CHF mechanism associate with the burnout phenomenon. In the analysis, the hot channel of the SAFARI-1 model was adapted to resemble the test rig used by Sudo. The model provides adequate simulation of the phenomenon and means for editing the required conditions mentioned above. Moreover, the paper discusses the development and validation of the above-mentioned models to adequately apply the Sudo scheme, and presents comparisons with an unbounded (i.e. no condition check) application that would conclude a challenging condition to the fuel, as opposed to this work that concludes no physical burnout and the fuel remains intact during the course of the transient. (author)