Abstract: Thermocouple junctions located in the hot and cold regions of an elongated heat conductive body extending through a measurement zone of a power monitoring device, are interconnected in series to provide a differential temperature signal of increased signal strength and fast signal response. The signal is free of the error heretofore arising from asymmetrical axial heat flow through the heat conductive body.

Abstract: The elongated monolithic radiation absorbing body of a gamma ray sensor has its entire external surface exposed to coolant for establishing a uniform heat sink temperature throughout. Cold junction regions are formed in portions of the elongated body of reduced cross-sectional area sufficient to produce measurable signal levels from a differential temperature thermocouple. A removable low melting filler in the reduced cross-sectional portions of the body enable accurate electrical calibration of the sensor.

Abstract: There is disclosed an elongated cylindrical rod of heat-conducting and electrically-conducting material having a central bore containing a plurality of thermocouples, the hot and cold junctions of which are placed respectively in separate zones along the rod. In each zone, the hot junction of one thermocouple is fixed generally in position axially at the midway of an annular reduced-section portion of the cylindrical rod, the cold junction is located generally axially between two reduced-diameter portions and an annular insulating chamber is defined annularly opposite to each reduced-diameter portion by an outer shielding tube. The outer tube surrounds the cylindrical rod. The completed unit is to be placed within a reactor core fuel assembly to be monitored.