Main Results of Na-K Alloy Boiling Investigation

Abstract

Boiling experiments on eutectic sodium-potassium alloy in the model of fast reactor subassembly under conditions of low-velocity circulation carried out at the IPPE call for further investigations into numerical modeling of the process. The paper presents analysis of pin bundle liquid metal boiling, stages of the process, its characteristics (wall temperature, coolant temperature, flow rate. pressure void fraction and others), that allowed the pattern map to be drawn. The problem of conversion of the data gained in Na-K mock-up experiments to in-pile sodium reactor operating conditions is analyzed here, as well as thermodynamic similarity of liquid metal coolants and eutectic Na-K alloy. Data on bundle boiling in Na-K are presented in comparison with those in different liquid metals. Analysis of data on liquid metal heat transfer in cases of pool boiling, boiling in tubes, in slots, and in pin bundles, as well as data on critical heat flux in tubes was performed and discussed in the paper. The relationship for calculation of critical heat flux in liquid metal derived by the authors is presented. Results of numerical modeling of liquid metal boiling heat transfer during accident cooling of reactor core applied to experimental conditions of going from forced to natural circulation are presented, too.

Experimental research on the thermal hydraulic characteristics of sodium boiling in an annulus

“…As a result, the boiling heat transfer coefficient is affected by the heat flux and system pressure instead of the mass velocity or the sodium vapor quality. The effective heat transfer coefficients can achieve hundreds of kW/m 2 [25]. Experimental data under different conditions and several correlations for the boiling heater transfer coefficient have been announced by different scholars.…”

“…Based on the experimental data, a correlation was proposed, assuming that the heat transfer to boiling potassium obeyed the known power dependence on heat flux typical of nucleate boiling and caused by the variation of the number of acting vaporization centers with the increase in heat flux. Experimental data on potassium pool boiling and boiling in tubes [28] and on sodium potassium boiling in pin bundles were gathered by Sorokin et al [25] and a correlation was obtained based on the data.…”