Nuclear Reactor Fuel Rod Defect Localization via Power Distribution Patterns
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Solution Overview
Problem
Current methods for monitoring nuclear reactor operations, such as flux-tilting and power distribution analysis, are either risky or result in production losses due to the need for reduced reactor power, and fail to detect defects in fuel rods without prior power changes.
Innovation Solution
A method combining fission gas detection with continuous power distribution pattern analysis using core simulators and sensors to locate defects in fuel rods during normal reactor operation, allowing for preventive actions without power reduction and reduced flux-tilting tests.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If flux-tilting method is used to locate fuel rod defects, then defect localization capability is improved, but production loss increases due to reduced reactor power
Solution Approach 1:
The system continuously monitors and establishes power distribution patterns before defects occur, enabling proactive defect detection without requiring preliminary power reductions. The baseline power distribution is established during normal operation, and deviations from this baseline indicate defects, eliminating the need for flux-tilting power suppression tests
Solution Approach 2:
The invention replaces the mechanical flux-tilting method (which requires physical movement of control rods and power changes) with a monitoring-based detection system that uses neutron flux sensors and power distribution analysis to locate defects, thereby avoiding production losses associated with reduced reactor power
2Measurement precision
If flux-tilting method is used to locate fuel rod defects, then defect localization capability is improved, but system reliability deteriorates due to increased risk of secondary defects
Solution Approach 1:
The system applies preliminary anti-action by continuously monitoring power distribution patterns to detect defects before they can develop into secondary defects. By establishing baseline power distributions and detecting deviations, the system prevents the progression from primary to secondary defects without requiring flux-tilting operations that could cause additional damage
Solution Approach 2:
The monitoring system enables the reactor to self-diagnose fuel rod defects by analyzing its own power distribution patterns and neutron flux measurements, eliminating the need for external flux-tilting interventions that could inadvertently cause secondary defects
3Productivity
If continuous monitoring is implemented during normal operation, then productivity is maintained, but device complexity increases
Solution Approach 1:
The system achieves multi-functionality by using existing reactor instrumentation (neutron flux sensors, power distribution measurement systems) for dual purposes: normal reactor control and defect detection. This eliminates the need for separate dedicated monitoring hardware, maintaining productivity while minimizing additional device complexity
Solution Approach 2:
The system implements feedback mechanisms where power distribution measurements and neutron flux data are continuously analyzed and compared against established patterns. This feedback loop enables automatic defect detection and localization without requiring complex manual analysis systems, maintaining continuous operation while managing system complexity through automated processing
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
Enables effective localization of fuel rod defects without production losses, allowing for timely preventive measures and reduced risk of secondary defects, while maintaining normal reactor power levels.
Implementation Method 1
continuously measuring during a normal fuel operation cycle a radioactivity level in the off-gas stream for detecting a possible release of fission gases from the fuel rods
Implementation Method 2
sensors evenly distributed throughout the core sense local power levels at different positions of the core
Implementation Method 3
calculating local power levels at different positions in the core by means of the process computer; establishing a power distribution pattern based on the instantaneous power distributions over time
Data Source
Figure 1
Figure 2a~2b
Figure 3
AI summary
The invention concerns a method of monitoring the operation of a reactor (1 ) of a nuclear plant. The reactor is operated at a given total reactor power during a normal fuel operation cycle. The radioactivity level in the off-gas stream (8) is continuously measured to detect a possible release of fission gases from the fuel rods (9) as a consequence of a fuel leakage due to a defect (13) on the cladding (10) of any of the fuel rods in any of the fuel assemblies (3). An instantaneous power distribution (PDI) is regularly established in the core (2) and a power distribution pattern (PDp) over time is established based on the instantaneous power distributions. The release of fission gases and the established power distribution pattern are then combined and correlations between changes in the release of fission gases and in the power distribution pattern are observed in order to determine a position of the defect.