Gamma Scanning Apparatus for Fuel Assembly Burn-up Measurement
Solution Overview
Problem
Existing gamma scanning apparatus for measuring burn-up and power distribution in fuel assemblies at nuclear power plants are prone to measurement errors due to minor bends or shifts in fuel rods and require accurate installation angles, leading to inefficiencies and increased costs.
Innovation Solution
A gamma scanning apparatus that includes a gamma-ray detector, collimator, absorber, shield, and moving/fixing means, which rotates the fuel assembly 360 degrees while maintaining constant height, allowing for accurate burn-up and power distribution measurements independent of installation angle, using a gamma-ray counting circuit and data collecting/analyzing apparatus to derive distribution data.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the fuel assembly is fixed at a specific installation angle for measurement, then the measurement precision of burn-up and power distribution is improved, but the reliability of the measurement is worsened due to sensitivity to minor bends or shifts in fuel rods
Solution Approach 1:
The patent applies the dynamics principle by transforming the fixed-angle measurement approach into a rotating measurement approach. The fuel assembly is rotated through 360 degrees during measurement, allowing the system to adapt to minor bends or shifts in fuel rods dynamically. This rotational movement enables the detection system to capture radiation patterns that are independent of the fuel assembly's initial installation angle, thereby maintaining both measurement precision and reliability despite variations in fuel rod positioning.
2Reliability
If two gamma-ray detectors are used symmetrically arranged to eliminate angle dependence, then the reliability of measurement is improved, but the device complexity and cost increase
Solution Approach 1:
Instead of using multiple detectors in a static symmetric arrangement, the patent employs a single detector combined with dynamic rotation of the fuel assembly. The rotational movement creates a time-varying geometric relationship between the detector and the fuel assembly, effectively eliminating the need for symmetric multi-detector configurations. This approach reduces device complexity while maintaining the reliability benefit of angle-independent measurement.
Solution Approach 2:
The patent applies the self-service principle by using the fuel assembly's own rotation to achieve angle-independent measurement. Rather than requiring external complex detector arrangements to compensate for angle sensitivity, the system leverages the rotational movement of the fuel assembly itself to create measurement conditions that are inherently independent of installation angle. This self-service approach eliminates the need for additional complex detector components.
3Measurement precision
If multiple measurement steps are performed to account for angle variations, then the measurement precision is improved, but the loss of time increases
Solution Approach 1:
The patent applies the continuity of useful action principle by performing the 360-degree rotation and measurement in a single continuous operation rather than through multiple discrete measurement steps. The fuel assembly rotates continuously while the detector records radiation patterns throughout the rotation cycle, capturing all necessary angular information in one uninterrupted measurement sequence. This continuous approach eliminates the time loss associated with repeated measurement steps while maintaining measurement precision.
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 accurate measurement of burn-up and power distribution without relying on precise installation angles, allowing for rapid assessment of multiple fuel assemblies, reducing measurement time and costs.
Implementation Method 1
a gamma-ray detector (3), a collimator (5) that limits a measuring range in a fuel assembly (1) and limits entry of gamma rays from the fuel assembly (1) into the gamma-ray detector (3)
Implementation Method 2
a collimator (5) that limits a measuring range in a fuel assembly (1) and limits entry of gamma rays from the fuel assembly (1) into the gamma-ray detector (3)
Implementation Method 3
an absorber (7) that controls intensity of the gamma rays entering the gamma-ray detector (3)
Data Source
AI summary
A gamma scanning apparatus includes a moving and fixing mechanism which moves/fixes a housing to a definite position, and a rotating and moving mechanism which moves a fuel assembly vertically in addition to rotating the assembly. A gamma-ray counting circuit measures an output of a gamma-ray detector, and a data collecting/analyzing and controlling apparatus analyzes data output from the gamma-ray counting circuit, in association with data relating to the rotation and movement of the fuel assembly by the rotating and moving mechanism. The rotating and moving mechanism, after fixing the vertical position of the fuel assembly with the housing also fixed, rotates the fuel assembly through 360° with its height kept constant, and during the 360° rotation of the fuel assembly, the gamma-ray counting circuit measures either a time average of count values of the detector during the rotation or an integral value within a fixed time.