The NEA Working Party on Scientific Issues of Reactor Systems (WPRS) held its annual meeting and associated expert group meetings on 19-21 February 2020 with more than 60 experts from 16 countries. The WPRS conducts studies on the reactor physics of advanced nuclear systems, reactor fuel performance, radiation transport and shielding, reactor core thermal-hydraulics and uncertainty analysis in the modelling of power systems, focusing on light water reactor (LWR) transients. Participating experts reported on and discussed ongoing activities under the WPRS, including the International Reactor Physics Experiment Evaluation (IRPhE) Project, the International Fuel Performance Experiments database (IFPE) and the Shielding Integral Benchmark Archive and Database (SINBAD).