Perhitungan Kapasitas Kalor Pb-Bi Cair dengan Beragam Komposisi sebagai Pendingin Reaktor Menggunakan Simulasi Dinamika Molekul

Abstract

The development of next-generation nuclear reactors requires efficient and thermally stable coolant materials. Liquid lead-bismuth (Pb-Bi) alloys are promising candidates due to their favorable thermophysical properties. This study aims to calculate the heat capacity of liquid Pb-Bi alloys at various compositions using molecular dynamics simulations. The simulations were carried out with LAMMPS to generate atomic and energy data, and OVITO for structural analysis. The system was modeled using the Lennard-Jones potential and equilibrated at 873 K. Heat capacity was determined based on energy fluctuations under the NVT ensemble. The results show that compositions with 5% to 90% Pb produced stable and realistic heat capacities, ranging from 0.0001 to 0.0010 eV/K.atom. In contrast, Pb-rich compositions (95% and 100%) showed excessive energy fluctuations and unrealistic heat capacities, indicating thermal instability. These findings suggest that bismuth plays a key role in stabilizing the liquid structure. The eutectic composition (Pb 44.5% – Bi 55.5%) demonstrated optimal thermal performance and is recommended as a reliable reactor coolant materia