The Hot Function Flow Characteristics of a Main Cooling Water System for the Nuclear Fuel Test Loop Installed in HANARO

A nuclear fuel test loop (after below, FTL) is installed in IR1 of an irradiation hole in HANARO for testing neutron irradiation characteristics and thermo hydraulic characteristics of a fuel loaded in a light water power reactor or a heavy water power reactor. There is an in-pile section (IPS) and an out-pile section (OPS) in this test loop. When HANARO is normally operated, the fuel loaded in the IPS has a nuclear reaction heat generated by a neutron irradiation. To remove the generated heat and to maintain an operating conditions of the test fuel, a main cooling water system (MCWS) is installed in the OPS of the FTL. The MCWS is composed of a main cooler, a pressurizer, two circulation pumps, a main heater, interconnection pipe line and instruments. The interconnection pipeline is a closed loop which is connected respectively to an inlet and an outlet of the IPS. To absorb the nuclear reaction heat, there is a higher elevation pipeline with a reverse U letter type pipeline installed in upstream of the cooler. And there is another higher elevation pipeline for sucking a fluid by a vertically installed circulation pump with a top suction and a side discharge. Therefore, we predicted that it is difficult to continuously suck a fluid and pressurize the fluid due to air pockets in the two higher elevation pipelines under a high temperature operation. To verify the hot function flow characteristics of the MCWS including air pockets of the higher elevation pipelines, a flow net work analysis has been conducted under a high temperature operation. When the two higher elevation pipelines wholly filled with coolant, it was confirmed through the results that the pump pressurizes the coolant normally. And it was confirmed through the analysis results that the system hot function characteristics met the system design requirements.