Research of Signal Disturbance of Water Level Measuring System in Reactor Vessel

The measurement result of reactor vessel water level represents the change of core coolant inventory, which is used to monitor whether the core is lost of coolant, and provides the thermo hydraulic status of the primary coolant loop under the accident conditions. During the thermal functional test of a NPP, whether in the process of water filling in the primary circuit for the first time, or under half-loop water level condition, the alarm signal of low water level in the upper part of core frequently fluctuated, which interfered with the judgment of the operator on the water level state of the primary circuit. Through in-depth study on the principle of reactor vessel water level measurement, and heat transfer analysis of water level signal disturbance according to the thermal hydraulic environment of water measurement detector, the root cause of this issue was determined. The experimental scheme of optimizing the heating current function of water level measurement system is established, and combined with the measured data, the feasibility of optimizing heating current method was comfirmed, and a feasible solution is also given. In view of the maturity of this water level measurement technology and its wide application in the field of instrument control, the research results have certain reference and enlightenment for the treatment of abnormal problems in liquid level monitoring system.