Low-Pressure Water Reactor With Passive Natural Circulation
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Solution Overview
Problem
Current nuclear reactors face high construction costs and safety concerns due to complex design features, which are exacerbated by regulatory demands, leading to uncertain investment and operational risks, especially in smaller modular reactors.
Innovation Solution
A low-pressure water reactor (LPWR) design featuring a reactor core located underground, utilizing natural circulation and passive safety systems, minimizing reliance on complex safety features and active systems for reactivity control and cooling, with a simplified design achieving a power output of around 300MW(e).
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If complex safety features and active systems are used in nuclear reactors, then safety and reliability are improved, but device complexity and construction costs increase
Solution Approach 1:
The reactor core is designed to automatically shut down by sinking to the bottom of the containment vessel when power is lost or safety issues arise, without requiring active control systems. The natural circulation of coolant occurs passively through density differences, eliminating the need for complex pumping systems. This self-regulating mechanism provides inherent safety while minimizing system complexity.
Solution Approach 2:
Active mechanical control systems for reactor shutdown and coolant circulation are replaced with passive physical mechanisms. The core uses gravitational sinking for shutdown instead of mechanical actuators, and natural convection for coolant flow instead of mechanical pumps, thereby reducing device complexity while maintaining safety.
2Reliability
If complex safety features and regulatory compliance measures are implemented, then safety is improved, but construction costs and investment uncertainty increase
Solution Approach 1:
The passive safety mechanisms eliminate the need for expensive active safety systems and complex control infrastructure. The automatic core shutdown and natural circulation cooling provide inherent safety without requiring costly redundant systems, directly reducing construction and operational costs.
Solution Approach 2:
The simplified design uses fewer expensive materials and components by eliminating complex active safety systems. The containment vessel and core structure are designed for straightforward construction with minimal regulatory burden, reducing overall project cost and investment uncertainty.
3Device complexity
If passive safety systems and simplified design are used, then construction costs and operational complexity are reduced, but power output may be limited
Solution Approach 1:
The reactor operates at lower pressures and temperatures compared to conventional designs, which simplifies the containment requirements and safety systems. This parameter change enables a simpler, more cost-effective design while still achieving useful power output, trading some power density for reduced complexity and cost.
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 LPWR achieves reduced construction and maintenance costs while significantly lowering environmental risks and operational complexity, ensuring reliable operation and safety through inherent safety features, including passive cooling and simplified emergency response.
Implementation Method 1
A nuclear power plant produces heat by energy release from a fissile material like uranium or plutonium by nuclear fission in a controlled chain reaction
Implementation Method 2
utilizing natural circulation and passive safety systems
Implementation Method 3
converting, by the riser tube, the heated water to steam
Implementation Method 4
whereby the conversion creates a difference in a primary coolant density that achieves a density-driven natural circulation
Data Source
Figure 1
Figure 2~3
Figure 4
AI summary
A low pressure water reactor (LPWR) and a method for controlling a LPWR are proposed. The LPWR comprises a reactor vessel with an internal cavity comprising a primary coolant, a riser tube, and a core located below ground level with 6-15 bars atmosphere pressure; a steam drum connected to the riser tube and located at ground level at a pressure of 1 -10 bars absolute; a water storage tank to store borated water; a passive injection system to inject the borated water from the water storage tank into the vessel; and low pressure steam turbines to generate power at a pressure of 1-10 bars atmosphere. The vessel heats water up to a certain temperature and the riser tube converts the heated water to steam, which is further delivered to the turbine(s). The conversion creates a difference in a primary coolant density that initiates a density-driven natural circulation of the primary coolant in the riser tube, downcomer, steam drum and core.