Natural Circulation Fast Reactor Coolant Startup
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Solution Overview
Problem
The existing method for organizing natural circulation of liquid metal coolant in the heat sink of a fast neutron nuclear reactor requires a forced circulation mode, which introduces additional hydraulic resistance and cannot switch to natural circulation without heat transfer from the reactor, compromising safety and efficiency.
Innovation Solution
The method involves pre-heating the pipelines and equipment of the heat sink circuit to specific temperatures, creating a density difference that initiates natural circulation without pumps, allowing the circuit to operate solely in natural circulation mode from startup, using sectional electric heaters to maintain calculated temperatures and ensuring passive safety.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If forced circulation mode is used to circulate coolant in the heat sink circuit, then the coolant can be circulated reliably, but additional hydraulic resistance is introduced and the system cannot operate in natural circulation mode without reactor heat transfer
Solution Approach 1:
The invention removes the pump from the heat sink circuit, extracting the forced circulation component entirely. The circuit is designed to operate solely in natural circulation mode from startup, eliminating the harmful hydraulic resistance introduced by pumping equipment while maintaining reliable coolant circulation through optimized natural circulation pathways and density-driven flow.
Solution Approach 2:
The system utilizes the natural density differences of the coolant at different temperatures to self-drive circulation without external mechanical assistance. The hot coolant in the lifting section (lower density) naturally rises while the cooler coolant in the downing section (higher density) naturally descends, creating a self-sustaining circulation loop that operates autonomously from reactor startup.
2Ease of operation
If pumps are used to start coolant circulation, then circulation can be initiated, but the system cannot switch to natural circulation mode before reactor power ascension
Solution Approach 1:
The invention performs preliminary heating of the lifting and downing sections to different temperatures before startup, creating the necessary density difference in advance. This preliminary thermal preparation enables natural circulation to begin immediately when coolant is introduced, eliminating the need for pump-assisted startup and ensuring the system can operate in natural circulation mode from the very beginning of reactor operation.
Solution Approach 2:
The system is designed to self-initiate circulation through natural convection forces generated by the pre-established temperature and density differences. The circulation startup is achieved without external mechanical intervention, allowing the system to transition directly to natural circulation mode and enhancing passive safety by eliminating dependence on active pumping components.
3Temperature
If pipelines and equipment are heated to the same temperature before filling, then overcooling of coolant is prevented, but natural circulation cannot be initiated without reactor heat transfer
Solution Approach 1:
The invention applies different temperature levels to different sections of the circuit - the lifting section is heated to a higher temperature than the downing section. This local quality differentiation creates the density gradient necessary for natural circulation while still preventing overcooling of the coolant, as both sections are heated above ambient temperature but with a controlled temperature difference.
Solution Approach 2:
The invention changes the temperature parameter distribution from uniform (same temperature throughout) to non-uniform (different temperatures in lifting vs. downing sections). This parameter change creates the density difference driving force for natural circulation while maintaining coolant temperature above levels that would cause overcooling, thus resolving the contradiction between temperature uniformity and circulation initiation capability.
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 approach eliminates forced circulation, reduces hydraulic resistance, and ensures the heat sink circuit operates in natural circulation mode from startup, enhancing reactor safety by leveraging temperature-induced density differences to drive coolant circulation without reactor heat transfer.
Implementation Method 1
sectional electric heaters are switched on for heating the pipelines and equipment of the lifting and downing sections of the heat sink circuit to the calculated temperatures
Implementation Method 2
the circulation of the coolant in the circuit is launched simultaneously with the transition to the natural circulation mode and until the nuclear reactor reaches its nominal operating parameters due to the difference in densities
Implementation Method 3
the output of heat source 1 is connected by means of a lifting pipe 2 with the input of the device for removing heat 3
Data Source
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AI summary
The invention relates to the field of nuclear engineering and can be used to organize the natural circulation of liquid metal coolant in the heat sink of a fast neutron nuclear reactor. In order to create a driving pressure of circulation without using pumping equipment and to provide the required direction of natural circulation of the liquid metal coolant in the heat sink circuit of the fast neutron nuclear reactor in the absence of heat transfer from the reactor before filling the pipelines and equipment of the lifting and downing sections of the circuit, they are pre-heated by electric heating to temperatures T1 and T2, respectively, which are selected from the condition of inequality: ρ1(T1)·g·ΔH1 > ρ2(T2)·g·ΔH2 + ΔP, where: ρ1(T1) is the density of the liquid metal coolant at temperature T1 of pipelines and equipment in the lifting section; ρ2(T2) is the density of the liquid metal coolant at temperature T2 of pipelines and equipment at the downing section; ΔH1 is the height difference between the inlet and outlet of the lifting section; ΔH2 is the height difference between the inlet and outlet of the downing section; ΔP is the hydraulic resistance of the circuit; g is the acceleration of gravity. The circulation of the coolant in the circuit and the transition to natural circulation mode are carried out simultaneously until the nuclear reactor reaches its rated operating parameters by creating a moving pressure of the circulation due to the difference in densities ρ1(T1) and ρ2(T2) of the liquid metal coolant on the lifting and downing sections of the circuit, respectively.