Experimental research on the gravity-driven boron injection system for a 200 MW nuclear heating reactor

The gravity-driven boron injection system (GDBIS), designed by the Institut e of Nuclear Energy Technology (INET) of the Tsinghua University, PR China, isa new type of passive system to be applied in the 200 MW nuclear heating reactor (NHR-200), also designed by INET. The function of this system is t o shut down the reactor in an emergency, in case control rods do not operat e properly. A berate water tank is located 10 m above the top of the pressu re vessel. When the pressure of the reactor and the boron tank balances, th e berate water will be driven by gravity to flow into the reactor, and thus shut down the reactor. The thermal hydraulic performances of the system fo r cold (room temperature nitrogen) and hot (mixture of hot steam and nitrog en) operating conditions, especially the response time of pressure and wate r injection, have been researched under different initial conditions. First ly, several factors, e.g. orifice on steam lines, and the volume ratio of t he gas-steam spaces of the reactor and the boron tank, have effects on the pressure and water injection response time and other thermal hydraulic perf ormance of the system. Secondly, the steam and liquid communication modes, namely the acting time and sequence of the action of valves connecting stea m and liquid lines, have great influences on the performance of the system. Thirdly, the limited pressure balance time (about 1.0 s) can be achieved u nder the cold condition. This investigation shows that GDBIS can be properl y used in the 200 MW nuclear heating reactor. (C) 2000 Elsevier Science Ltd . All rights reserved.