Passive Shutdown System for Liquid Metal Reactor
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Solution Overview
Problem
Conventional liquid metal cooled reactors face high operational and maintenance costs due to expensive pumping loads and large thermal variations during power changes, leading to thermal stresses and inefficient load following capabilities, as well as risks of core damage from loss of primary coolant flow.
Innovation Solution
A passive shutdown system that uses a neutron absorber and flow control mechanisms to maintain a constant coolant temperature, reducing thermal stresses and allowing for flexible power control through core flow and control rod adjustments, and a float structure to manage reactivity and prevent core damage during loss of flow events.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If temperature is increased to increase power output to the grid, then electrical power output is improved, but thermal stresses and thermal fatigue on metal components worsen
Solution Approach 1:
The patent changes the control parameter from temperature-based power control to flow-rate-based power control. By adjusting the coolant flow rate through the core rather than changing outlet temperature, the system can modulate power output without subjecting components to large thermal cycles, thereby reducing thermal stress and fatigue while maintaining electrical power output capability.
2Reliability
If primary and secondary pumps operate at 100% flow at low power, then coolant flow is maintained, but pumping power consumption increases
Solution Approach 1:
The patent implements dynamic pump operation where the pump flow rate is adjusted according to the reactor power level. Instead of operating at fixed 100% flow, the pump speed varies to match the thermal demand, allowing the system to maintain adequate coolant flow for reliability while significantly reducing pumping power consumption during low-power operations.
3Reliability
If high primary and secondary coolant flow rate is established before critical state, then core cooling is ensured, but pumping loads and operational costs increase
Solution Approach 1:
The patent establishes a minimum threshold flow rate (e.g., 15% of rated flow) that must be maintained before the reactor can achieve criticality, rather than requiring high flow rates. This preliminary action ensures adequate core cooling is in place before power generation begins, while avoiding the excessive pumping loads associated with maintaining high flow rates throughout all operating conditions.
4Adaptability or versatility
If temperature changes are large during power transitions, then power output flexibility is improved, but thermal cycling and wear on components worsen
Solution Approach 1:
The patent changes the control parameter from temperature modulation to flow-rate modulation for achieving load following. By varying the coolant flow rate through the core to match grid demand, the system achieves flexible power output adaptation without subjecting components to large temperature changes, thereby extending component service life while maintaining load following 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 reduces pumping power consumption, mitigates thermal fatigue, enhances load following capabilities, and lowers operational and maintenance costs while ensuring core safety and stability.
Implementation Method 1
A passive shutdown system for a liquid metal cooled reactor includes a tube configured to extend through a core of the liquid metal cooled reactor, wherein the tube defines a flow path for a liquid metal coolant, and a neutron absorber within the tube
Implementation Method 2
flowing a liquid metal coolant at a flow rate through a core of the liquid metal cooled reactor via a tube that contains a neutron absorber therein
Implementation Method 3
The tube defines a flow path for a liquid metal coolant
Data Source
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AI summary
A passive shutdown system (100) for a liquid metal cooled reactor may include a tube (104) and a neutron absorber (106) within the tube. The tube may be configured to extend through a core of the liquid metal cooled reactor. The tube has an upper end (110) and a lower end (112). The tube defines a flow path for a liquid metal coolant (102). The neutron absorber is a mobile structure configured to partially obstruct a flow of the liquid metal coolant within the flow path. A method of operating a liquid metal cooled reactor may involve the use of the passive shutdown system.