External Control Rods for Nuclear Reactor Refueling
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Solution Overview
Problem
Current nuclear reactor designs face challenges during refueling operations, as control rods must be disconnected from their motor-drive elements to avoid interference, and their positioning within the core can lead to thermal and structural issues, affecting safety and efficiency.
Innovation Solution
The nuclear reactor design features control and shutdown rods positioned externally, with mechanical decoupling from the core, allowing refueling without disconnection and reducing the core's diameter and fissile material, while incorporating a float-controlled shutdown system for reliable passive shutdown.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If control rods are positioned within the core, then they can effectively control the nuclear reaction, but they interfere with refueling operations and require disconnection from motor-drive elements
Solution Approach 1:
The control rods are extracted from the core and repositioned in the reflector region surrounding the core. This allows the control rods to maintain their function of controlling the nuclear reaction while eliminating interference with refueling operations, as they are now located outside the core volume where fuel elements are replaced
2Reliability
If control rods are positioned within the core, then they can control the reaction, but they create thermal and structural issues affecting safety
Solution Approach 1:
By extracting the control rods from the core and positioning them in the reflector, the source of thermal and structural problems is removed from the core region. The control rods remain functional for reaction control but no longer contribute to thermal interference and structural complexity within the core
Solution Approach 2:
The reflector serves as an intermediary region that hosts the control rods while surrounding the core. This mediator structure allows control rods to be positioned close enough to the core for effective neutron absorption control, while the reflector material provides thermal isolation and structural support separate from the core's thermal environment
3Ease of operation
If control rods are positioned externally, then refueling is simplified and core heterogeneity is reduced, but the control mechanism complexity increases
Solution Approach 1:
The reflector structure is given multiple functions: it serves as the structural boundary of the core, provides neutron reflection, and hosts the control rod mechanisms. This multi-functionality reduces the need for separate dedicated control rod support structures, thereby limiting the increase in overall device complexity despite the external positioning of control rods
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
This design enables safe and efficient refueling without disrupting control mechanisms, reduces core heterogeneity and power gradients, and provides a reliable passive shutdown system resistant to pump acceleration fluctuations.
Implementation Method 1
a reliable passive shutdown system resistant to pump acceleration fluctuations
Data Source
AI summary
The invention concerns a nuclear reactor comprising a vessel closed at the top by a radially external fixed closing structure and by a radially internal mobile closing structure. The vessel contains a core immersed in a primary cooling fluid and comprising fuel elements, control rods, shutdown rods, and a hydraulic separation structure delimiting a hot manifold and a cold manifold in which the primary fluid circulates. The control rods and the shutdown rods are inserted in respective penetrations of the fixed closing structure and are therefore located radially external to the mobile closing structure and external to an upper portion of the separation structure containing respective heads of the fuel elements.