Passive Containment Cooling for Boiling Water Reactors
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Solution Overview
Problem
Conventional emergency core cooling systems for boiling water reactors face challenges in enhancing reliability, particularly in cooling the containment vessel during a loss of coolant accident, due to the reliance on multiple reactor coolant water and sea water systems, which are prone to common mode failures and vulnerable to natural disasters like tsunamis, and the passive containment cooling system's inefficiency when active safety systems are activated.
Innovation Solution
The proposed emergency core cooling system incorporates an advanced passive containment cooling system with a gas vent pipe submerged in a scrubbing pool, reducing the number of active safety divisions and systems, and utilizing air-cooled injection systems, while the passive containment cooling system includes a heat exchanger with a gas supply and condensate return pipes to efficiently cool the containment vessel, even when active safety systems are activated.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If multiple reactor coolant water systems and sea water systems are used to cool the containment vessel, then the cooling capacity is sufficient, but the reliability decreases due to common mode failures and vulnerability to natural disasters
Solution Approach 1:
The invention introduces a passive containment cooling system as an intermediary system that operates independently from the active reactor coolant water and sea water systems. This passive system uses natural convection and condensation processes to cool the containment vessel, thereby maintaining cooling capacity while eliminating the common mode failures associated with multiple active systems.
Solution Approach 2:
The invention replaces the mechanically complex active cooling systems (requiring pumps, motors, and external water sources) with a passive thermodynamic system that utilizes natural convection, condensation, and gravity-driven water circulation. This substitution eliminates mechanical failure points while maintaining adequate cooling capacity.
2Device complexity
If the passive containment cooling system is used, then the system simplicity is improved, but the cooling efficiency decreases when active safety systems are activated
Solution Approach 1:
The invention creates a dynamic interaction between the passive containment cooling system and the active safety systems. The passive system is designed to operate complementarily with active systems, where the active systems provide primary cooling and the passive system provides supplemental cooling and pressure control, thereby maintaining high cooling efficiency while preserving system simplicity.
Solution Approach 2:
The passive containment cooling system is designed to perform multiple functions: it can operate independently as a primary cooling system, function as a supplemental cooling system when active systems are running, and provide containment pressure control. This multi-functionality maintains cooling efficiency across different operational scenarios while keeping the system simple.
3Reliability
If the number of active safety divisions is increased to enhance reliability, then the safety margin is improved, but the number of components and system complexity increases
Solution Approach 1:
The passive containment cooling system serves as an intermediary that reduces the need for multiple redundant active safety divisions. By providing an independent cooling pathway that does not rely on complex mechanical systems, the passive system enhances the safety margin while avoiding the component proliferation that would result from adding more active safety divisions.
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 configuration improves the reliability of cooling the containment vessel in a loss of coolant accident, reduces the number of components, and enhances resilience against natural disasters and station blackouts by diversifying active safety systems and emergency power sources, ensuring effective containment vessel cooling and core integrity.
Implementation Method 1
a gas vent pipe connected to the outlet plenum of the heat exchanger at one end and to the scrubbing pool at another end, the gas vent pipe being configured to vent non-condensable gases in the heat exchanger into the scrubbing pool
Implementation Method 2
a heat exchanger including an inlet plenum, an outlet plenum and heat transfer tubes, at least part of the heat exchanger being submerged in the cooling water in the cooling water pool; a gas supply pipe connected to the inlet plenum of the heat exchanger at one end and to a gas phase part of the containment vessel at another end
Implementation Method 3
at least part of the heat exchanger being submerged in the cooling water in the cooling water pool
Implementation Method 4
a condensate return pipe connected to the outlet plenum of the heat exchanger at one end and to the containment vessel at another end, the condensate return pipe being configured to guide condensate in the heat exchanger into the containment vessel
Data Source
AI summary
According to an embodiment, an emergency core cooling system has: three active safety divisions each including only one motor-driven active safety system; one passive safety division including a passive safety system; an emergency power source disposed in each of the active safety divisions to supply electric power to the motor-driven active safety system; and an advanced passive containment cooling system disposed in the passive safety division. Only two active safety divisions each includes a low pressure flooder system that is commonly used with a residual heat removal system as the only one motor-driven active safety system. The other active safety division includes an air-cooled injection system as the only one motor-driven active safety system.