Fabrication tests of TRICOTH-type reactor water level sensor

To study the feasibility of manufacturing a TRICOTH reactor water level sensor, a prototype structure design has been done and fabrication tests have been performed. The sensor consists of an Inconel sheath with a diameter of 3.2 mm, magnesia insulating material and inner elements (two heater wires and three sensing wires). The heater wires are made of Ni-Cr alloy, while the sensing wires are serially connected chromel-alumel-constantan wire-trains with multijunctions. The sensors have been tested using dimension measurements, electric tests, heat cycle tests, and functional tests. The cold functional tests showed clear trinary code outputs that were uniquely related to the momentary water levels. An advanced sensor structure was designed for actual in situ applications. This TRICOTH-III sensor includes a central coaxial heater, six trinary coding sensor wires, and one set of standard thermocouple wires, all integrated in a 3.4 mm outer sheath. This sensor has stand-alone capability. Because of the hybrid (digital and analog) nature of the sensor, a unique and continuous level indication is obtained