Passive Emergency Feedwater Natural Circulation Cooling
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Solution Overview
Problem
Current nuclear reactor designs face challenges in maintaining safe operation during normal and emergency conditions without operator intervention, particularly in addressing loss of feedwater flow scenarios and decay heat removal, leading to extended shutdowns and inefficiencies.
Innovation Solution
A novel cooling system that includes a power module assembly with a submerged containment vessel and a secondary cooling system utilizing natural circulation to circulate emergency feedwater through a heat exchanger, leveraging the containment cooling pool as both a source of makeup water and a heat sink, enabling passive cooling without external power.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional active cooling system with feedwater pumps is used, then the reactor can be cooled during normal operation, but the system requires operator intervention and external power during emergencies, leading to extended shutdowns
Solution Approach 1:
The emergency feedwater system utilizes natural circulation driven by density differences between hot and cold water to automatically circulate cooling water through the heat exchanger without requiring external power or operator intervention. The system self-regulates based on temperature gradients, with cooler water naturally sinking and hotter water rising to maintain continuous cooling flow during emergency conditions
Solution Approach 2:
The patent replaces the mechanical feedwater pump system with a passive natural circulation system. Instead of using mechanical force to drive water flow, the system relies on thermal convection and buoyancy forces created by temperature-induced density variations, eliminating the need for external power sources and mechanical components during emergency operation
2Reliability
If the reactor is shut down by flooding containment or depressurizing reactor vessel during loss of feedwater, then safety is maintained, but electricity generation is halted for extended periods
Solution Approach 1:
The emergency feedwater system is pre-configured with natural circulation pathways and thermal storage capacity in the containment pool before emergencies occur. This preliminary arrangement allows the system to immediately begin passive cooling operations upon activation, maintaining reactor safety without requiring time-consuming shutdown procedures or system reconfigurations
Solution Approach 2:
The system utilizes changes in water temperature and density parameters to drive the cooling process. By leveraging the thermal energy already present in the containment pool and the natural density gradients created during cooling operations, the system maintains effective heat removal while avoiding the need for reactor shutdown, thus reducing loss of time
3Extent of automation
If a passive cooling system using natural circulation is implemented, then operator intervention is eliminated, but the system complexity increases with submerged containment vessels and natural circulation pathways
Solution Approach 1:
The patent combines the containment vessel and cooling pool into a single integrated structure, where the containment pool serves dual purposes as both a safety barrier and a heat sink. The heat exchanger is positioned to utilize the natural thermal stratification within the containment, merging multiple functions into unified system components that reduce overall complexity despite the passive operation requirement
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 solution provides a passive means for long-term cooling and decay heat removal, allowing for quick reactor restarts and reduced downtime, while maintaining containment of fission products and minimizing environmental impact, thus enhancing the safety and viability of nuclear power as a global energy source.
Implementation Method 1
The cooling system is configured to circulate the emergency feedwater through the heat exchanger by natural circulation
Implementation Method 2
an outlet line connected to the heat exchanger. The outlet line is configured to remove heat from the nuclear reactor
Implementation Method 3
leveraging the containment cooling pool as both a source of makeup water and a heat sink
Data Source
AI summary
A power module assembly includes a reactor vessel containing a reactor core surrounded by a primary coolant. A containment vessel is adapted to be submerged in a containment cooling pool and to prohibit a release of the primary coolant outside of the containment vessel. A secondary cooling system is configured to remove heat generated by the reactor core. The heat is removed by circulating liquid from the containment cooling pool through the primary coolant.