LDR Lite Benchmark: Description of the Core Model

We alleviate the lack of detailed, design-specific SMR-benchmarks by providing the first specifications of the LDR lite benchmark.This benchmark is based on the public version of the LDR-50 reactor design, developed at VTT since 2020 for low temperature heat production applications.The main characteristics of this 50 MWth integrated pressure water reactor are in-vessel control rod drives, boronless operation, natural circulation driven primary circuit, self-pressurization and passive decay heat removal through a dual vessel design.The reactor core consists of 37 17x17 square fuel assemblies with active fuel length of 100 cm.This paper provides a brief description of the reactor core model and introduces the first core neutronics benchmark task in which cold all-rods-out and cold critically rodded states are modelled.Preliminary results calculated with the Monte Carlo code Serpent and the nodal diffusion code Ants are presented and compared.