BELLA: a multi-point dynamics code for safety-informed design of fast reactors

Highlights: • A multi-point dynamics code for simulation of LMFRs transients was developed. • The lumped-parameter simulator can predict primary system's average temperatures. • The ability to model natural circulation allows for safety-informed design. • The benchmark with respect to SAS4A/SASSYS-1 shows satisfactory accuracy. - Abstract: In this paper, the multi-point dynamics code BELLA and its benchmarking with respect to SAS4A/SASSYS-1 is described for a small fast reactor cooled with natural convection of lead (ELECTRA). It is shown that BELLA is capable of reproducing the magnitude of mass-flow, reactivity, power and temperature excursions during design extension conditions with an accuracy better than 10%. Hence, the BELLA code can be used for safety-informed design and stability analyses of fast reactor systems, permitting to isolate essential phenomena and trends of significance for their safety assessment