Safety system grade apparatus and method for detecting a dropped control rod and malfunctioning exit thermocouples in a pressurized water reactor
AssigneeWestinghouse Electric Corp.
InventorsAlbert J. Impink, Jr., Michael D. Heibel, Toshio Morita, Raymond Calvo
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Abstract
A safety system grade dropped rod detection system for a pressurized water reactor (PWR) utilizes core exit thermocouples arranged in multiple trains and hot and cold leg RTDs to generate a safety system grade rod stop signal. The system generates from the temperature signals a relative power deviation (RD) and a curvature index (CI), which is the spatial second derivative of RD for each fuel assembly. The CI signatures not only provide rapid, reliable detection of dropped control rods, but also clearly identify failed and failing thermocouples.
Claims10
A method of protecting a pressurized water reactor having a reactor core with fuel assemblies through which a reactor coolant is circulated from a cold leg to a hot leg, said method comprising the steps of:
- providing safety system grade core exit thermocouples at selected fuel assemblies across said reactor core;
- automatically measuring core exit temperatures at the selected fuel assemblies at which said safety system grade core exit thermocouples are located;
- automatically measuring average core inlet and outlet temperatures with safety system grade temperature sensors at said cold leg and hot leg;
- automatically analyzing with a safety system grade analyzer said pattern of exit temperatures and said average core inlet and outlet temperatures to identify a dropped control rod;
- and
- automatically blocking with safety system grade means withdrawal of control rods from said reactor core when a dropped rod is identified.
Dependencies are inferred from the claim text.