[en] This report summarizes a study performed by Brookhaven National Laboratory for the Reactor and Plant Safety Issues Branch, RES of the US Nuclear Regulatory Commission in pursuit of the resolution of NRC Generic Issue 99. Generic Issue 99 focuses on the risk associated with loss of residual heat removal events at PWRs while shut down. Numerous loss of residual heat removal events have occurred at pressurized water reactors (PWRs) in the USA, which were terminated prior to damaging the reactor core. This study estimates the risk from loss of residual heat removal events and investigates ways of lowering this risk