Neutronic and thermal performance analysis of advanced cladding materials for ACP-100 SMR

Abstract

This study analyzes the impact of various cladding materials: silicon carbide (SiC), Iron-Chromium-Aluminum Alloy (FeCrAl), Titanium-Molybdenum-Zirconium Alloy (TMZ), and Austenitic Stainless Steel (Alloy 33) and thicknesses (from 100 to 1000 µm) on the neutronic and thermal performance of the ACP-100 small modular reactor (SMR). Zircaloy is used as the reference material for comparison. Computational simulations using the Monte Carlo code SERPENT and nuclear data library ENDF/B-VII.1 indicate that SiC achieves the highest effective multiplication factor (keff) (1.3096), a 0.65 % increase over Zircaloy, while Alloy 33 exhibits the lowest keff (1.1724), a 9.90 % decrease at beginning of life (BOL) for thickness of 570 μm. As cladding thickness increases from 100 to 1000 µm, keff decreases by 4 % for SiC, 5.2 % for Zircaloy, and 18.2 % for Alloy 33 at BOL due to higher thermal neutron absorption. SiC sustains a cycle length of over 900 effective full power days (EFPDs) at 100 μm, achieving 912 EFPDs at 570 μm. In contrast, Alloy 33 shows poor neutron economy, with the cycle length dropping to 200 EFPDs at 1000 μm. SiC and TMZ demonstrate superior thermal conductivity (122.0 W/m·K and 110.3 W/m·K), reducing the fuel temperature by ∼10 K. While thicker cladding improves structural integrity, it compromises thermal efficiency. A thickness of 570 µm provides an optimal balance between performance and durability. SiC emerges as the most promising alternative cladding material for the ACP-100 SMR and further studies are recommended to assess its long-term behavior under reactor conditions.