Neutron Reflector Block Segmentation for HTGR Stress Management
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Solution Overview
Problem
High temperature gas cooled nuclear reactors face challenges with graphite neutron reflector blocks experiencing uneven internal stresses due to extreme conditions, leading to potential cracking and compromised structural integrity, which is exacerbated by the introduction of additional reflector layers that increase gas leakage and reduce thermal efficiency.
Innovation Solution
A neutron reflector block design featuring a first portion and a second portion with a narrowed profile, allowing for a closed geometric arrangement and reduced internal stress generation, along with a key block system to secure adjacent blocks, maintaining heat flow paths while minimizing stress.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stress or pressure
If the size of graphite reflector blocks is reduced to limit internal stresses, then internal stress magnitude is reduced, but gas leakage increases and thermal efficiency decreases
Solution Approach 1:
The reflector block is segmented into an inner layer with smaller blocks and an outer layer with larger blocks. This segmentation allows the inner layer to experience lower internal stresses while the outer layer provides structural integrity and maintains heat flow paths, preventing gas leakage and preserving thermal efficiency.
Solution Approach 2:
Different regions of the reflector are assigned different block sizes based on local requirements. The inner layer uses smaller blocks where neutron flux is highest and stress is most critical, while the outer layer uses larger blocks for structural support and heat dissipation, optimizing both stress management and thermal performance locally.
2Stress or pressure
If additional reflector layers are introduced to reduce block size, then internal stresses are limited, but gas leakage increases
Solution Approach 1:
The reflector is divided into multiple layers with different block sizes, where the inner layer handles stress management and the outer layer maintains structural continuity. This segmentation prevents gas leakage by ensuring the outer layer provides a continuous barrier while the inner layer manages stresses.
Solution Approach 2:
The inner and outer layers are combined into a unified reflector structure where the layers work together. The inner layer with smaller blocks manages stress, while the outer layer with larger blocks provides structural integrity and prevents gas leakage, achieving both goals simultaneously.
3Stress or pressure
If block size is reduced to manage internal stress, then stress magnitude decreases, but structural integrity may be compromised
Solution Approach 1:
The reflector is segmented into inner and outer layers with different block sizes. The inner layer uses smaller blocks to manage internal stresses, while the outer layer uses larger blocks to provide structural integrity and support, ensuring both stress management and structural strength are maintained.
Solution Approach 2:
Different block sizes are used in different regions: smaller blocks in the stress-critical inner layer and larger blocks in the structurally important outer layer. This local optimization ensures structural integrity is maintained where needed while managing stresses where they are most severe.
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
The design reduces internal stress and maintains heat transfer efficiency, enhancing the operational safety and longevity of the reactor by balancing stress generation and heat transfer properties.
Implementation Method 1
The reflectors mainly act to reflect neutrons back into the core so as to increase fissile activity in the core
Implementation Method 2
When graphite is used as reflective material, the reflectors also act as neutron moderators
Implementation Method 3
heat flow between the layers of blocks is decreased and leads to the passive cooling capacity of the core being reduced
Data Source
Figure 1
Figure 2~3
Figure 4
AI summary
The invention relates to a neutron reflector block. The neutron reflector block comprises a first portion and a second portion. The first portion has a first end face and oppositely located intermediate shoulders which are spaced from the first end face. The first end face and the intermediate shoulders are bounded by spaced side faces and spaced upper and lower faces. The second portion protrudes from the first portion between the intermediate shoulders and has spaced side faces and spaced upper and lower faces. The second portion side faces are more narrowly spaced relative to the first portion side faces. The second portion also has a second end face located oppositely to the first end face.