Nuclear reactor fluid thermal monitoring array

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.

1 . A nuclear reactor, comprising:
 a reactor core;   a downcomer assembly at least partially defining an annular downcomer flow channel, the downcomer assembly being configured to direct a coolant fluid to the nuclear reactor core via the annular downcomer flow channel;   a thermal monitoring array including at least one flowmeter assembly, the at least one flowmeter assembly coupled to at least one surface of the downcomer assembly such that the at least one flowmeter assembly is exposed to at least a portion of the downcomer flow channel, the flowmeter assembly including,
 a first temperature sensor configured to generate first temperature data based on measuring a temperature of a first flowstream of the coolant fluid in the portion of the downcomer flow channel; 
 a heating element coupled to the first temperature sensor such that the heating element is operable to apply heat to the first temperature sensor; and 
 a second temperature sensor configured to generate second temperature data based on measuring a temperature of a second flowstream of the coolant fluid in the portion of the downcomer flow channel, the second temperature sensor being at least partially insulated from the heating element; and 
   a control system configured to determine a flow rate of the coolant fluid through the downcomer flow channel based on at least the first and second temperature data.   
     
     
         2 . The nuclear reactor of  claim 1 , wherein the first and second temperature sensors are configured to be exposed to a common flowstream. 
     
     
         3 . The nuclear reactor of  claim 1 , wherein the control system is configured to
 determine a temperature difference based on the first and second temperature data; and   determine the flow rate based on the temperature difference, a magnitude of electrical power supplied to the heating element, and a surface area of an interface between the heating element and the first temperature sensor.   
     
     
         4 . The nuclear reactor of  claim 1 , wherein the flowmeter assembly includes,
 at least one third temperature sensor, the at least one third temperature sensor being configured to generate third temperature data based on measuring a temperature of at least one flowstream of the coolant fluid in the downcomer flow channel, the at least one third temperature sensor being at least partially insulated from the heating element.   
     
     
         5 . The nuclear reactor of  claim 1 , wherein the thermal monitoring array includes a plurality of flowmeter assemblies, at least two flowmeter assemblies of the plurality of flowmeter assemblies being exposed to separate portions of the downcomer flow channel. 
     
     
         6 . The nuclear reactor of  claim 5 , wherein the at least two flowmeter assemblies are exposed to at least one of
 axially-separated portions of the downcomer flow channel, relative to a longitudinal axis of the downcomer flow channel, and   azimuthally-separated portions of the downcomer flow channel, relative to the longitudinal axis of the downcomer flow channel.   
     
     
         7 . The nuclear reactor of  claim 1 , wherein the control system is configured to determine a temperature of fluid flowing in the at least one portion of the downcomer flow channel based on the first and second temperature data. 
     
     
         8 . The nuclear reactor of  claim 1 , wherein the control system is configured to determine a phase of fluid flowing in the at least one portion of the downcomer flow channel based on the first and second temperature data. 
     
     
         9 . The nuclear reactor of  claim 1 , wherein the nuclear reactor is at least one of a pressurized water reactor and a boiling water reactor. 
     
     
         10 . The nuclear reactor of  claim 1 , wherein the thermal monitoring array includes a flow channel cover configured to direct at least the first and second fluid flowstreams in flow communication with the at least one flowmeter assembly and in isolation from a remainder of the downcomer flow channel. 
     
     
         11 . An apparatus, comprising:
 a flowmeter assembly configured to be coupled to at least one surface such that the flowmeter assembly is exposed to at least a portion of a flow channel, the flowmeter assembly including,
 a first temperature sensor configured to generate first temperature data based on measuring a temperature of a first flowstream of the coolant fluid in the portion of the flow channel; 
 a heating element coupled to the first temperature sensor such that the heating element is operable to apply heat to the first temperature sensor; and 
 a second temperature sensor configured to generate second temperature data based on measuring a temperature of a second flowstream of the coolant fluid in the portion of the flow channel, the second temperature sensor being at least partially insulated from the heating element. 
   
     
     
         12 . The apparatus of  claim 11 , wherein the first and second temperature sensors are configured to be exposed to a common flowstream. 
     
     
         13 . The apparatus of  claim 11 , wherein the flowmeter assembly includes insulating material configured to at least partially insulate the second temperature sensor from the heating element, the insulating material being packed around the heating element and at least a portion of the first temperature sensor. 
     
     
         14 . The apparatus of  claim 11 , wherein the flowmeter assembly includes,
 at least one third temperature sensor, the at least one third temperature sensor being configured to generate third temperature data based on measuring a temperature of at least one flowstream of the coolant fluid in the flow channel, the at least one third temperature sensor being at least partially insulated from the heating element.   
     
     
         15 . The apparatus of  claim 14 , wherein the at least one third temperature sensor and the second temperature sensor are configured to be exposed to at least one of
 axially-separated portions of the flow channel, relative to a longitudinal axis of the flow channel; and   azimuthally-separated portions of the flow channel, relative to the longitudinal axis of the flow channel.   
     
     
         16 . The apparatus of  claim 11 , further comprising:
 a flow channel cover configured to at least partially define the first and second fluid flowstreams.   
     
     
         17 . A method, comprising:
 generating first temperature data at a first temperature sensor based on both a temperature of a first flowstream of a coolant fluid and heat transfer to the first temperature sensor from a heating element, the heating element being directly coupled to the first temperature sensor at an interface such that the heat transfer is through the interface, the first temperature data indicating a first temperature measured by the first temperature sensor;   generating second temperature data at a second temperature sensor based on a temperature of a second flowstream of the coolant fluid in the flow channel and substantially independently of heat generated by the heating element, the second temperature sensor being at least partially insulated from the heating element, the second temperature data indicating a second temperature measured by the second temperature sensor; and   communicating the first temperature data and the second temperature data to a remotely-located computer processing device.   
     
     
         18 . The method of  claim 17 , further comprising:
 determining a flow rate of the coolant fluid through the flow channel based on the first and second temperature data, the determining including,
 determining a temperature difference between the first temperature and the second temperature, and 
 determining the flow rate of the coolant fluid based on the temperature difference, a surface area of the interface, and a rate of the heat transfer through the interface; and 
   controlling heat rejection by a nuclear reactor core based on the determined flow rate of the coolant fluid through the flow channel.   
     
     
         19 . The method of  claim 17 , further comprising:
 determining a location of a fluid two-phase interface in the flow channel based on the first and second temperature data, the determining including,
 determining a temperature difference between the first temperature and the second temperature, 
 determining a phase of the coolant fluid in at least one of the first and second flowstreams based on the temperature difference; and 
   controlling a flow rate of the coolant fluid through one or more portions of the flow channel based on the determined location of the fluid two-phase interface in the flow channel.   
     
     
         20 . The method of  claim 17 , further comprising:
 determining a coolant fluid temperature distribution through one or more portions of the flow channel based on the first and second temperature data, and   controlling a flow rate of the coolant fluid through one or more portions of the flow channel based on the determined fluid temperature distribution through the one or more portions of the flow channel.