Spent Fuel Unloading System with Negative Pressure and Inert Gas
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Solution Overview
Problem
The challenge in safely unloading spent fuel elements from a pebble bed high temperature gas-cooled reactor, which requires a system that prevents oxidation and uncontrollable release of graphite dust and radioactive gases.
Innovation Solution
A nuclear power plant spent fuel negative pressure unloading system comprising a fuel element transport pipe and a gas transport pipe, with an iodine adsorber and dust filter to manage radioactive materials and maintain a negative pressure state, ensuring the integrity and safety of the fuel elements during unloading.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If spent fuel elements are unloaded from the reactor, then the fuel elements can be stored and processed, but oxidation of spent fuel and release of graphite dust and radioactive gases occur
Solution Approach 1:
The patent applies inert atmosphere principle by filling the fuel element transport pipe with protective gas (nitrogen or carbon dioxide) to create an oxygen-free environment. This prevents oxidation of spent fuel elements during transport and storage, while also containing graphite dust and radioactive gases within the closed system. The protective gas atmosphere is maintained throughout the unloading process from reactor to storage facility.
Solution Approach 2:
The patent uses protective gas as an intermediary substance between the spent fuel elements and the external environment. This intermediary gas layer acts as a barrier that prevents direct contact between oxygen and the spent fuel, thereby preventing oxidation. The gas also serves as a containment medium for graphite dust and radioactive gases, allowing safe transport and storage.
2Reliability
If a closed unloading system is used, then oxidation and release of harmful substances are prevented, but system complexity increases
Solution Approach 1:
The patent segments the unloading system into distinct functional modules: the fuel element transport pipe for conveying spent fuel, the protective gas supply system for maintaining inert atmosphere, the storage facility for receiving fuel elements, and the connection interfaces between these components. This modular segmentation allows each subsystem to be designed, operated, and maintained independently, reducing overall system complexity while maintaining the benefits of a closed system.
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 system effectively prevents oxidation of spent fuel and retention of graphite dust and radioactive gases, ensuring the safety and integrity of the fuel elements during unloading, while maintaining a negative pressure state to prevent uncontrollable releases.
Implementation Method 1
A negative pressure generating mechanism is further provided in the closed unloading system, and the negative pressure generating mechanism is used to generate negative pressure in the fuel element transport pipe
Implementation Method 2
The nuclear power plant spent fuel unloading system uses a closed unloading system and a protective gas, wherein the spent fuel element is transported from the reactor to the storage facility through the fuel element transport pipe in the closed unloading system filled with the protective gas
Implementation Method 3
an iodine adsorber is installed between the end of the gas transport pipe in proximity to the fuel element unloading pipe and the gas driving mechanism
Implementation Method 4
a dust filter is installed between the end of the gas transport pipe in proximity to the fuel element unloading pipe and the gas driving mechanism
Data Source
AI summary
A nuclear power plant spent fuel negative pressure unloading system comprises a fuel element transport pipe and a gas transport pipe. The fuel element transport pipe comprises a fuel element output pipe, a fuel element lifting pipe, and a fuel element unloading pipe connected in series. The fuel element unloading pipe is arranged obliquely downward in the direction of fuel element movement. The distal end of the fuel element unloading pipe is connected sequentially to fuel loading apparatus and a transfer apparatus. Two nozzles of the gas transport pipe are connected to set positions on the fuel element output pipe and the fuel element unloading pipe respectively. A gas driving mechanism is connected to the gas transport pipe. An inlet of the gas driving mechanism is arranged at one end in proximity to the fuel element unloading pipe.