Reactor Coolant Pump Placement in PWR Downcomer Annulus
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Solution Overview
Problem
Existing PWR designs face challenges in integrating reactor coolant pumps due to space constraints and potential vulnerabilities during a loss of coolant accident, particularly when coupled at the bottom or top of the pressure vessel, which can interfere with natural convection and emergency cooling systems.
Innovation Solution
The design incorporates a vertically oriented cylindrical pressure vessel with upper and lower sections, featuring reactor coolant pumps with an impeller inside the pressure vessel and a motor outside, connected by a drive shaft, which allows for efficient primary coolant circulation and reduces the risk of interference with other components by positioning the pumps at the mid-flange region, providing support through forged flanges and minimizing vessel penetrations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If reactor coolant pumps are coupled into the bottom of the pressure vessel, then the pumps can be installed with straightforward structural support, but this introduces vessel penetrations at low elevation which are problematic in the event of a loss of coolant accident
Solution Approach 1:
The pump installation location is moved from the bottom (vertical dimension) to the mid-flange region (horizontal/intermediate dimension), changing the spatial dimension of pump coupling to avoid both bottom penetrations and top space constraints
2Reliability
If reactor coolant pumps are coupled into the top of the pressure vessel, then vessel penetrations are avoided at low elevation, but the region is already occupied by external control rod drive mechanism units and internal pressurizer
Solution Approach 1:
The pump installation location is moved from the top (upper vertical dimension) to the mid-flange region (intermediate vertical dimension), utilizing the underutilized mid-height space to avoid conflicts with top-mounted components
3Strength
If pumps are positioned at critical areas, then structural support is maximized, but interference with natural convection and emergency cooling systems occurs
Solution Approach 1:
The pump is positioned at a specific local region (mid-flange area) that provides adequate structural support through forged flanges while maintaining sufficient distance from the reactor core and natural convection pathways to avoid generating harmful flow turbulence
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 enhances coolant circulation efficiency, reduces the risk of flow turbulence, and simplifies maintenance access while minimizing the likelihood of a loss of coolant accident by strategically placing pumps away from critical areas, thus ensuring reliable operation and safety.
Implementation Method 1
the primary coolant flow circuit can be powered by heating caused by the reactor core and cooling of the primary coolant as it flows upward and away from the reactor core. However, for higher power reactors it is advantageous or necessary to supplement or supplant the natural convection with motive force provided by electromechanical reactor coolant pumps.
Implementation Method 2
the primary coolant flow circuit can be powered by heating caused by the reactor core and cooling of the primary coolant as it flows upward and away from the reactor core
Implementation Method 3
a drive shaft operatively connecting the pump motor with the impeller
Data Source
AI summary
A pressurized water reactor (PWR) includes a vertical cylindrical pressure vessel and a nuclear reactor core disposed in a lower vessel section. A hollow cylindrical central riser is disposed concentrically inside the pressure vessel. A downcomer annulus is defined between the central riser and the pressure vessel. A reactor coolant pump (RCP) includes (i) an impeller disposed above the nuclear reactor core and in fluid communication with the downcomer annulus to impel primary coolant downward through the downcomer annulus, (ii) a pump motor disposed outside of the pressure vessel, and (iii) a drive shaft operatively connecting the pump motor with the impeller. The PWR may include an internal steam generator in the downcomer annulus, with the impeller is disposed below the steam generator. The impeller may be disposed in the downcomer annulus. The RCP may further comprise a pump casing that with the impeller defines a centrifugal pump.