Fast Reactor Reflector Segmentation for Thermal Stress Control
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Solution Overview
Problem
Conventional fast reactors face issues with reflector deformation and thermal stress due to temperature variations, which can lead to failure in shutting down the reactor within a predetermined time.
Innovation Solution
A reflector control type fast reactor design featuring a neutron reflecting part formed by stacked metal plates with coolant channels and a cavity part with sealable containers, connected via universal joints, to manage thermal expansion and stress, ensuring robustness and reliable operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a reflector is used to control reactivity by vertical movement, then reactivity control capability is improved, but thermal expansion and deformation occur due to temperature variations
Solution Approach 1:
The reflector is divided into multiple independent reflector units that can move vertically relative to each other. Each unit is separated by gaps allowing independent thermal expansion and movement, preventing deformation while maintaining reactivity control capability through collective vertical displacement
Solution Approach 2:
The reflector units are constructed using composite material structures combining different materials with complementary properties. The first reflector unit uses a material with lower thermal expansion coefficient than the second reflector unit, creating a composite structure that manages differential thermal expansion while maintaining overall structural integrity and reactivity control function
2Speed
If the reflector is moved down for urgent shutdown, then shutdown speed is improved, but thermal stress and deformation may prevent timely shutdown
Solution Approach 1:
By segmenting the reflector into multiple independently movable units with gaps between them, each unit can move down freely during emergency shutdown without being constrained by thermal deformation of adjacent units. The gaps provide clearance that prevents contact and deformation, ensuring reliable rapid shutdown
Solution Approach 2:
The invention changes the physical parameters of the reflector structure by introducing gaps and using materials with different thermal expansion coefficients. This allows the reflector units to undergo thermal expansion in a controlled manner that does not prevent rapid downward movement during emergency shutdown, maintaining both speed and reliability
3Stress or pressure
If coolant channels are added to metal plates, then thermal stress is reduced, but device complexity increases
Solution Approach 1:
The reflector units incorporate coolant channels creating a porous-like structure within the metal plates. These channels allow coolant flow through the reflector, providing internal cooling that reduces thermal stress. The channel integration adds structural complexity but is offset by the simplified overall design compared to external cooling systems
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 effectively prevents deformation and thermal stress, allowing for controlled reactivity adjustment and safe shutdown of the reactor, enhancing structural robustness and operational reliability.
Implementation Method 1
each of the metal plates has a plurality of coolant channels through which the coolant flows
Implementation Method 2
the reflector 4 may be deformed by a thermal expansion difference
Implementation Method 3
a neutron reflecting part disposed on an outside of the reactor core in a vertically movable manner
Data Source
AI summary
A fast reactor 1 controlled with a reflector comprises: a reactor vessel 7 accommodating therein a coolant 5; a reactor core 2 disposed in the reactor vessel 7 and immersed in the coolant 5; and a reflector 4 that vertically moves for adjusting leakage of neutrons generated from the reactor core 2 to control a reactivity of the reactor core 2, the reflector 4 including a neutron reflecting part 4a disposed on an outside of the reactor core 2 in a vertically movable manner, the neutron reflecting part 4a having a neutron reflecting ability higher than that of the coolant 5, and a cavity part 4b positioned above the neutron reflecting part 4a, the cavity part 4b having a neutron reflecting ability lower than that of the coolant 5. The neutron reflecting part 4a is formed of a plurality of metal plates 37 that are stacked on each other. Each of the metal plates 37 has a plurality of coolant channels 36 through which the coolant 5 flows.