[3E10-15] Advanced Reactor Safety

3:45 PM - 4:00 PM JST(6:45 AM - 7:00 AM UTC)

[3E14] Study on Eutectic Melting Behavior of Control Rod Materials in Core Disruptive Accidents of Sodium-Cooled Fast Reactors(40) Eutectic Melting and Relocation Behavior of B4C Pellet-Stainless Steel Using Numerical Approach

*Zeeshan Ahmed¹, Avadhesh Kumar Sharma¹, Marco Pellegrini¹, Yamano Hidemasa², Koji Okamoto¹ (1. The University of Tokyo (UTokyo), 2. Japan Atomic Energy Agency)

Keywords:

Eutectic reaction,MPS method,Boron Carbide,Stainless Steel,Severe Accidents

In severe nuclear accidents, eutectic reactions induce early melting of stainless steel (SS) cladding and boron carbide (B4C), leading to control rod failure and eutectic melt relocation. A modified moving particle semi-implicit (MPS) method is employed to simulate this phenomenon in 2D and 3D, incorporating mass diffusion and eutectic reaction criteria based on the Fe-B phase diagram. Unlike previous eutectic MPS simulations, which used dummy walls as heat sources and radiation modeling, we reduce computational costs by employing surface particles of SS as a heat source. The study aims to measure the boron concentration in the solidified eutectic melt, numerically. The results indicate that upon eutectic reaction, boron diffuses into the SS wall, initiating melting at the B4C-SS interface and leading to melt flow following SS cladding penetration. The current model accurately replicated the eutectic melt's geometry, aligning closely with experimental observations. It also reflected a nearly 13% rise in boron's atomic composition within the eutectic melt, approximately 15% increase noted in our experiments.