Recommendations for modeling upper plenum injection system for a pressurized water reactor

Abstract

The present work examines the unique heat transfer modeling problems associated with analysis of performance of an upper plenum emergency core cooling injection system during a postulated Loss-of-Coolant Accident (LOCA) in a pressurized water reactor. The particular system under study consists of four 4-inch pipes conveying emergency core cooling water from outside the pressure vessel through four spare control and rod mechanism housings and internal pipings, discharging the water directly over the top of the reactor core. Previously, it has been assumed that the water injected into the upper plenum passes through the reactor core to the lower plenum without any heat interaction with the fuel rods during a LOCA. This simplified model neglects the many beneficial and adverse effects that accompany the upper plenum injection. This study is undertaken to examine the following items · heat transfer to the emergency core coolant before reaching the core · flow and heat transfer through the reactor core · reflood heat transfer. The phenomena occurring will be delineated and recommendations made for calculating both conservative and best estimate values. The method of solving these problems will be illustrated in a series of examples given in the appendices.