Reactor coolant pump startup under degraded conditions in a scaled OTSG lowered loop PWR

After a small break-loss of coolant accident or improper maintenance activities, the potential exists for a nonuniform distribution of boric acid in a PWR coolant system. This in turn presents the possibility of a reactivity excursion if sufficient volumes of boron-dilute water an transported into the core region without having first undergone substantial mixing. A research program is being conducted at the University of Maryland College Park (USA) 2/spl times/4 thermal-hydraulic test facility to assess the generation, transport and mixing of boron-dilute volumes. The start up of a pump and the flow of a boron free slug of water in the cold leg and subsequent transport to the core downcorner in the facility is investigated.