Abstract: The apparatus includes a flowmeter coupled a surface exposed to a flow channel. The flowmeter monitors a flow of coolant. The flowmeter includes a first temperature sensor that generates first temperature data based on measuring a first temperature of a first flowstream, a heating element coupled to the first temperature sensor where the heating element applies heat to the first temperature sensor through an interface, a second temperature sensor generates second temperature data based on measuring a second temperature of a second flowstream, the second temperature sensor being spaced apart from the heating element, and the second temperature sensor being at least partially insulated from the heating element so the second temperature data generated by the second temperature sensor is independent of heat generated by the heating element. A processor calculates a flowrate of the coolant based on the second temperature data and a temperature of the coolant fluid.

Abstract: A nuclear reactor includes a coolant fluid thermal monitoring array configured to monitor coolant fluid circulation in a downcomer flow channel of a nuclear reactor. The thermal monitoring array includes one or more flowmeter assemblies configured to monitor coolant fluid flow through separate flow channel portions. Each flowmeter assembly includes a first sensor coupled to a heating element and at least one second sensor at least partially insulated from the heating element. The first and second sensors may measure temperatures of separate flowstreams of coolant fluid through a downcomer flow channel portion. Temperature data generated by the first and second sensors of the flowmeter assemblies may be processed to monitor coolant fluid flow through the downcomer flow channel portions. The temperature data may be processed to monitor coolant fluid temperature. The temperature data may be processed to monitor a location of a fluid two-phase interface in the downcomer flow channel.