CORE TO SURGE-LINE ENERGY-TRANSPORT IN A SEVERE ACCIDENT SCENARIO

The analysis of loss-of-coolant accidents in a nuclear power plant, wh ich progress to the stage where the core is uncovered, poses important safety related questions. One of these questions concerns the rate of energy transport to metal components of the primary system. An experi mental program has been conducted at the University of Maryland test f acility which quantifies the rate of energy transfer from an uncovered core in a B&W plant (once-through type steam generators). SF6 is used to simulate the high pressure steam at prototypical conditions. A tim e-dependent scaling methodology is developed to transpose experimental data to prototypical conditions. To achieve this transformation, a no minal fluid temperature increase rate of 1.0-degrees-C s-1 is inferred from available TMI-2 event data. To bracket the range of potential pr ototypical transient scenarios, temperature ramps of 0.8-degrees-C s-1 and 1.2-degrees-C s-1 are also considered. Repeated tests, covering a range of test facility conditions, lead to estimated failure times at the surge line nozzle of 1.5-2 h after initiation of the natural circ ulation phase of the transient.