Study on Eutectic Melting Behavior of Control Rod Materials in Core Disruptive Accidents of Sodium-Cooled Fast Reactors: Project Overview and Progress Until 2018

Abstract

One of the key issues in a core disruptive accident (CDA) evaluation in sodium-cooled fast reactors is eutectic reactions between boron carbide (B4C) and stainless steel (SS) as well as its relocation. Such behaviors have never been simulated in CDA numerical analyses in the past, therefore it is necessary to develop a physical model and incorporate the model into the CDA analysis code. This study focuses on B4C-SS eutectic melting experiments, thermophysical property measurement of the eutectic melt, and physical model development for the eutectic melting reaction. The eutectic experiments involve the visualization experiments, eutectic reaction rate experiments and material analyses. The thermophysical properties are measured in a range from solid to liquid state. The physical model is developed for a severe accident computer code based on the measured data of the eutectic reaction rate and the physical properties. This paper describes the project overview and progress of experimental and analytical studies conducted until 2018. Specific results in this paper are boron concentration distributions of solidified B4C-SS eutectic sample in the eutectic melting experiments, which would be used for the validation of the eutectic physical model implemented into the computer code.

Thermophysical properties of austenitic stainless steel containing boron carbide in a solid state

“…Based on this background, the JAEA has been performing a research project to develop a physical model that can describe liquefaction and relocation behavior and obtain related experimental data since 2016 (Yamano et al, 2019). At various B4C concentrations, the physical model development requires a database of the thermophysical properties of SS containing B4C (abbreviated as SS-B4C) with a wide temperature range covering solid to the liquid phase.…”

“…This study aims to measure the thermophysical properties of the eutectic mixture in a solid state with a wide temperature range. To date, the thermophysical property measurements of the eutectic mixture from the solid to liquid state (Takai et al, 2019;Fukuyama et al, 2019;Ohta et al, 2019) and physical model development for the eutectic melting reaction (Liu et al, 2018) were conducted together with research institutes in our project (Yamano et al, 2019). As mentioned above, the SS-B4C produced by contact between SS and B4C is considered microscopically inhomogeneous from place to place.…”