Safety analysis code development and validation for lead-cooled fast reactor with helical coiled once-through steam generator

•An inhouse STH code named SACLER is modified developed with LBE and pure lead thermal properties and heat transfer models.•The liquid metal Helical Coiled Once Through Steam Generator model is applied in SACLER code.•Model separation validation and system integrity validation are carried out for the code. LFRs are one of six advanced Generation IV reactor concepts using lead-based coolant with high thermal conductivity, and HCOTSGs are generally adopted to highlight LFR miniaturization characteristics. An inhouse STH code SACLER with the HCOTSG model and the cover gas model was developed specifically for LFRs. NACIE facility was used to demonstrate SACLER accuracy. The HCOTSG model was verified using the RELAP code, experimental data, and ELSY design parameters. The validation results are consistent with the experimental data of NACIE. The HCOTSG model calculation results are in good agreement with the experimental data and the RELAP code. The error between the ELSY simulation result and the design value is within 1.0%. Liquid level simulation of ELSY shows that liquid levels are mainly determined by the pump head and flow resistance. SACLER can accurately simulate the LFR system with HCOTSG, including transient and steady-state conditions.