SEALER is a small lead-cooled reactor, designed by LeadCold Reactors for commercial power production in off-grid applications, such as Arctic communities and mining operations. For the purpose of safety-informed design, and independent verification of transient performance, KTH and LeadCold are developing BELLA, a lumped-parameter dynamics code for simulation of protected and un-protected transients in liquid metal cooled reactors. In the present contribution, results from a preliminary benchmark on UTOP and ULOF transients between BELLA and SAS4A/SASSYS-1 are presented. Whereas the codes predict very similar fuel and clad temperatures during the UTOP simulation, discrepancies in natural convection mass flow following a loss-of-flow event are identified and discussed.