Integrated Fuel and Control System for Nuclear Reactors
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Solution Overview
Problem
Nuclear reactors operating without soluble boron face challenges in managing reactivity control and maintaining a safe shut-down state during refueling operations due to the need for disassembling in-vessel control rod mechanisms, which complicates core design and increases the risk of criticality.
Innovation Solution
A fuel and control system integrates a drive motor, control rod assembly, and fuel unit with a frame, allowing them to be moved as a single unit, ensuring the control rod assembly remains intact during reloading, and incorporates instrumentation and electrical connections within the frame to prevent inadvertent withdrawal of control rods.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If in-vessel control rod drives are used to eliminate fast ejection transients, then reactor safety is improved, but the operating temperature and pressure conditions become challenging for electric components
Solution Approach 1:
The patent combines the control rod drive mechanism with the fuel assembly into an integrated unit. The drive mechanism is positioned inside the fuel assembly structure, merging two previously separate systems (control rod mechanism and fuel assembly) into one integrated component that can withstand in-vessel operating conditions.
Solution Approach 2:
The control rod drive mechanism is nested within the fuel assembly structure. The drive mechanism fits inside the fuel assembly housing, with the control rod extending through the fuel assembly. This nesting arrangement protects the electric components from direct exposure to extreme temperature and pressure while maintaining functional integrity.
2Ease of operation
If soluble boron is used for reactivity control, then reactivity management is simplified, but the chemical and volume control system complexity increases
Solution Approach 1:
The patent extracts the reactivity control function from the chemical boron system and transfers it to the mechanical control rod system. By integrating the drive mechanism with the fuel assembly, the control rods can be precisely positioned to manage reactivity without requiring complex chemical injection and volume control systems.
3Ease of operation
If control rods are operated from outside the pressure vessel, then access is easier, but fast ejection transients cannot be eliminated
Solution Approach 1:
The control rod drive mechanism is merged with the fuel assembly structure and positioned inside the pressure vessel. This integration eliminates the pressure differential that causes fast ejection transients while maintaining the ability to control rod positioning through the integrated drive system.
4Ease of operation
If control rod drives are removed during refueling, then fuel assembly access is enabled, but maintaining safe shut-down state becomes challenging
Solution Approach 1:
The control rod drive mechanism is permanently integrated with the fuel assembly structure. During refueling, the entire integrated unit (fuel assembly with embedded drive mechanism) is replaced as one component, eliminating the need to remove or access the control rod drives separately. This ensures control rods remain in safe positions throughout the refueling process.
5Ease of repair
If conventional separate control rod mechanisms are used, then component replacement is easier, but refueling operations become more complex and time-consuming
Solution Approach 1:
The control rod drive mechanism is merged with the fuel assembly into an integrated unit. While individual component replacement becomes more difficult, refueling efficiency is dramatically improved because the entire integrated unit can be quickly installed and locked into place without requiring separate assembly steps for control rod mechanisms.
Solution Approach 2:
The control rod drive mechanism is pre-integrated with the fuel assembly during manufacturing. This preliminary integration eliminates the need for complex on-site assembly operations during refueling, allowing for rapid deployment of complete fuel assembly units.
Data Source
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AI summary
According to an example aspect of the present disclosure, there is provided a fuel and control system (100) for a nuclear reactor (170) comprising, a drive assembly (110), a control rod assembly (140), and a fuel unit (150), featuring a frame (130), which attaches the drive assembly (110) to the fuel unit (150) and provides a space for control movement of the control rod assembly (140) so that the frame (130), the fuel unit (150), the drive assembly (110) and the control rod assembly (140) are integrated as one unit, and so that the fuel and control system (100) is configured to be loaded into and unloaded out of the nuclear reactor (170) as one unit.