In-Core Thermocouple Heat Output Calculation for Reactor Cores

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Solution Overview

Problem

Current methods for calculating heat output in reactor cores rely on indirect measurements, which are inaccurate and do not utilize direct core exit temperature data from in-core instrumentation.

Innovation Solution

A method using in-core instrumentation to directly measure core inlet and exit temperatures, employing thermocouples and neutron detectors to calculate heat output through equations, allowing for precise temperature measurements and improved accuracy.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Device complexity

If indirect measurement methods using RTD in hot leg and cold leg are used to calculate core inlet and exit temperatures, then the measurement system is simpler, but the measurement precision and reliability of heat output calculation deteriorates

Engineering Contradiction:
Improvemeasurement system complexityVSAvoidheat output calculation accuracy
Core Design Contradiction:
Device complexityVSMeasurement precision

Solution Approach 1:

The invention extracts the temperature measurement function from the external RTD system and relocates it inside the reactor core using in-core thermocouples. This allows direct measurement of core inlet and exit temperatures, eliminating the need for indirect calculations from hot leg and cold leg measurements, thereby improving measurement precision while maintaining reasonable system complexity

Inventive Principle:
Principle #2Taking out (Extraction)

Solution Approach 2:

The invention introduces in-core thermocouples as intermediary measurement devices that directly contact the coolant at core inlet and exit locations. These thermocouples serve as mediators between the coolant and the measurement system, providing accurate temperature data for heat output calculation without requiring complex indirect measurement systems

Inventive Principle:
Principle #24Intermediary (Mediator)

2Measurement precision

If core exit thermocouple (CET) is used in inadequate core cooling monitoring systems (ICCMS), then direct core exit temperature measurement is achieved, but the temperature data cannot be directly used in heat output calculation

Engineering Contradiction:
Improvecore exit temperature measurement accuracyVSAvoidsystem integration complexity
Core Design Contradiction:
Measurement precisionVSDevice complexity

Solution Approach 1:

The invention merges the core exit thermocouple (CET) measurement function with the heat output calculation system. By integrating the CET data directly into the heat output calculation equation along with core inlet temperature and mass flow rate, the system eliminates the need for separate ICCMS processing and enables direct heat output determination

Inventive Principle:
Principle #5Merging (Combining)

Solution Approach 2:

The in-core instrumentation system is designed to serve multiple functions: it provides core exit temperature measurement for cooling monitoring, supplies data for heat output calculation, and supports reactor power distribution monitoring. This multi-functionality eliminates the need for separate specialized systems and reduces overall system complexity

Inventive Principle:
Principle #6Universality (Multi-functionality)

Applied Scientific Principles

This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.

Function Achieved in This Case

Enhances the accuracy of heat output calculations by directly measuring core inlet and exit temperatures, improving safety margins and simplifying reactor equipment by reducing reliance on indirect methods.

Implementation Method 1

a first thermocouple that measures the core inlet temperature

Methodology Applied
Scientific EffectThermocouple effect: Seebeck Effect

Implementation Method 2

a second thermocouple that measures the core exit temperature

Methodology Applied
Scientific EffectThermocouple effect: Seebeck Effect

Implementation Method 3

an emitter that absorbs neutrons and emits an electric current

Methodology Applied
Scientific EffectNeutron absorption and electron emission: Photoelectric Effect

Data Source

PatentEP4679455A1Method for calculating heat output by using in-core instrument
Publication Date: 2026.01.14 KOREA HYDRO & NUCLEAR POWER CO LTD
  • EP4679455A1 patent drawingFigure 1
  • EP4679455A1 patent drawingFigure 2
  • EP4679455A1 patent drawingFigure 3

AI summary

Disclosed is a method of calculating heat output using in-core instrumentation, the method including: measuring a core inlet temperature and a core exit temperature using the in-core instrumentation; and calculating heat output Q of a core using the following equation, the in-core instrumentation including: a first thermocouple that measures the core inlet temperature; and a second thermocouple that measures the core exit temperature. Q=C×m×Th−Tc where, Q is a heat quantity, C is a specific heat, m is a mass flow rate, Th is a core exit temperature, and Tc is a core inlet temperature.