Nuclear Constant Storage for Precise Power Distribution

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Solution Overview

Problem

Conventional core performance calculation methods for nuclear reactors face precision issues due to the assumption of homogeneous nuclear constants in fuel assemblies with different nuclear characteristics, leading to errors in three-dimensional power distribution calculations.

Innovation Solution

A core performance calculation apparatus that stores response relationships between neutrons and fuel assembly characteristics, using these relationships to calculate the neutron effective multiplication factor and obtain precise power distributions without homogenization or diffusion approximation.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Device complexity

If nuclear constants are spatially homogenized in a fuel assembly cell including a half region of a gap between fuel assemblies, then calculation complexity is reduced, but manufacturing precision (power distribution accuracy) deteriorates when adjacent fuel assemblies have significantly different nuclear characteristics

Engineering Contradiction:

Improvecalculation complexityVSAvoidpower distribution accuracy

Core Design Contradiction:

Device complexityVSManufacturing precision

Solution Approach 1:

The invention segments the calculation approach by treating each fuel assembly individually rather than homogenizing across the entire core. Nuclear constants are evaluated separately for each fuel assembly type, and the power distribution is calculated by superimposing individual assembly contributions. This segmentation allows precise handling of assemblies with different nuclear characteristics while maintaining manageable calculation complexity through modular processing.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The invention applies local quality by evaluating nuclear constants specific to each fuel assembly's local characteristics (enrichment, type, position) rather than using uniform homogenized constants throughout. Each fuel assembly cell uses its own locally-evaluated nuclear constants, ensuring that assemblies with significantly different nuclear characteristics are treated with appropriate local precision while the overall calculation remains systematic.

Inventive Principle:

Principle #3Local quality

2Productivity

If the three-dimensional neutron flux distribution is calculated according to the diffusion equation, then calculation speed is improved, but measurement precision (power distribution accuracy) deteriorates due to diffusion approximation errors

Engineering Contradiction:

Improvecalculation speedVSAvoidpower distribution accuracy

Core Design Contradiction:

ProductivityVSMeasurement precision

Solution Approach 1:

The invention replaces the diffusion equation approach (which relies on diffusion approximation) with a direct neutron transport calculation method. Instead of using the simplified diffusion theory that approximates neutron behavior, the invention directly calculates neutron flux distribution by considering neutron transport physics, thereby eliminating diffusion approximation errors while maintaining computational efficiency through the modular assembly-by-assembly calculation structure.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

3Manufacturing precision

If response matrix calculations are performed to achieve high-precision power distribution, then manufacturing precision improves, but loss of time increases

Engineering Contradiction:

Improvepower distribution accuracyVSAvoidcalculation time

Core Design Contradiction:

Manufacturing precisionVSLoss of time

Solution Approach 1:

The invention segments the response matrix calculation into individual fuel assembly contributions. Instead of performing a full-core response matrix calculation that would be computationally intensive, the invention calculates and stores response matrices for individual fuel assembly types in advance, then uses these pre-computed assembly-level response matrices to build the overall power distribution through superposition. This segmentation dramatically reduces calculation time while maintaining precision.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The invention performs preliminary action by pre-evaluating and storing nuclear constants and response matrices for each fuel assembly type before the actual power distribution calculation. These pre-computed data are stored in tables for rapid retrieval and combination during the final calculation, eliminating the need for repeated complex computations and significantly reducing the time required for production power distribution calculations.

Inventive Principle:

Principle #10Preliminary action

Data Source

PatentUS20230197302A1Core performance calculation apparatus

Publication Date: 2023.06.22 HITACHI GE NUCLEAR ENERGY LTD

AI summary

A core performance calculation apparatus includes: a nuclear constant storage device that stores nuclear constants that have been evaluated in advance in analysis of a fuel assembly; and a three-dimensional core nuclear thermal-hydraulic characteristics analysis device that obtains core characteristics including a power of the fuel assembly. The nuclear constant storage device stores, as the nuclear constants, response relationships between a neutron that flows into a fuel assembly cell and fuel assembly nuclear characteristics, and response relationships between a neutron that is produced from a fuel rod and the fuel assembly nuclear characteristics. The three-dimensional core nuclear thermal-hydraulic characteristics analysis device obtains a neutron effective multiplication factor by using the response relationships that have been stored in the nuclear constant storage device, and obtains the power of the fuel assembly by using the neutron effective multiplication factor.