Pressure Oscillations in Darlington NGS Primary Heat Transport System Due to Tripping of One Main Circulating Pump

Abstract

The sudden trip of one or several transport PHT pumps will result in a pressure spike in the Primary Heat System. A pressure rise up to 10.7 MPaa might occur at the Reactor Outlet Header, which causes the reactor to trip. A study was conducted to simulate pump trips using the SOPHT code, in order to assess the problem and learn how to avoid it. It was found that the maximum pressure spike occurs when either one of the pumps farthest from the pressurizer trip. Several solution to the problem have been considered. The selected mode of operation is to lower the reactor trip setpoint, for a limited time, shortly after the pump trip.