Parameter sensitivity investigation and performance characterization of passive residual heat removal system for small modular lead-based alloy-cooled fast reactors

Small Modular Lead-based alloy-cooled Fast Reactors (SMLFRs) are attractive for their compact design, long refueling intervals, and a single loading operation duration exceeding 10 years. Ensuring reliable residual heat removal is critical for reactor safety. However, the sensitivity of different Passive Residual Heat Removal System (PRHRS) parameters on system performance has not been systematically analyzed, and a clear quantitative understanding of their effects for SMLFRs remains limited, posing challenges for design and optimization. To address this issue, we conduct a systematic sensitivity analysis to elucidate system characteristics and provide quantitative guidance for PRHRS optimization. Key parameters, including heat exchanger tube length, tube number, tube diameter, water tank diameter, cold and hot source height difference, pipe diameter, initial pressure, and initial temperature, are evaluated to quantify their critical impacts on performance indicators such as flow rate, heat removal power, pressure stabilization time, and cladding temperature. Results show that tube lengths of 2.0–3.3 m enable rapid stabilization, with cladding temperature minimized at 4.3 m; tube numbers of 12–24 ensure stability and improved cooling; medium tube diameters (24–60 mm) and pipe diameters (0.35–0.55 m) yield stable pressure; water tank diameters above 2.6 m enhance flow and cooling; at cold and hot source height differences ≥ 2.5 m, stable performance is ensured; and initial temperatures between 300 and 354 K shorten stabilization time, while instability arises above 381 K. These findings deepen understanding of PRHRS thermo-hydraulic behavior in SMLFRs and provide practical guidance for design and optimization to strengthen safety margins and operational reliability. © 2026 Elsevier Ltd. All rights are reserved, including those for text and data mining, AI training, and similar technologies.