Reactor Passive Cooling via Containment Flooding
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Solution Overview
Problem
Conventional shutdown cooling systems for pressurized water reactors require extensive maintenance, rely on pumps and electrical sources, and are inefficient beyond 250 °F, necessitating additional cooling methods for achieving cold shutdown temperatures.
Innovation Solution
A cooling system that includes a reactor pressure vessel, a steam generator, and a containment vessel, where steam is released to cool the reactor pressure vessel and the containment region is flooded with external water to achieve a cold shutdown state without relying on pumps or electrical power.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If conventional shutdown cooling systems are used to cool the reactor below 394 Kelvin, then cold shutdown status can be achieved, but the system requires extensive maintenance and testing due to dual purpose requirements
Solution Approach 1:
The invention extracts the cooling function from the complex dual-purpose shutdown cooling system by introducing water directly into the containment region. This separates the cold shutdown cooling function from the safety injection function, eliminating the need for extensive maintenance and testing of a dual-purpose system while achieving the same temperature reduction below 394 Kelvin
Solution Approach 2:
The containment region acts as an intermediary medium between the reactor pressure vessel and the external environment. By introducing water into the containment region rather than directly into the reactor system, the invention creates a thermal buffer that facilitates heat transfer while isolating the reactor from direct water contact, simplifying the overall system architecture
2Temperature
If shutdown cooling systems are used for cold shutdown, then reactor temperature can be reduced below 366 Kelvin, but the system relies on continuous functioning of pumps, heat exchangers, and electrical sources
Solution Approach 1:
The invention implements a passive cooling system where water introduced into the containment region automatically absorbs heat from the reactor pressure vessel through natural convection and conduction. This self-service mechanism eliminates the need for pumps, motors, and complex control systems, thereby removing single points of failure and significantly improving system reliability during cold shutdown operations
Solution Approach 2:
The invention replaces the mechanical shutdown cooling system (pumps, heat exchangers, piping) with a passive thermal conduction system. Water in the containment region directly conducts heat from the reactor vessel walls, eliminating mechanical components that require maintenance and can fail, thus improving reliability while achieving the same cooling effect
3Temperature
If conventional cooling systems are used, then reactor can be cooled effectively above 394 Kelvin, but further cool down to cold shutdown becomes substantially ineffective
Solution Approach 1:
The invention transitions from one-dimensional cooling (steam condensation inside the reactor system) to two-dimensional cooling by introducing water into the containment region surrounding the reactor pressure vessel. This additional thermal pathway through the containment region walls provides an effective cooling mechanism for temperatures below 394 Kelvin where steam cooling becomes ineffective
4Reliability
If dual purpose cooling systems are used for reactor safety, then safety function can be ensured, but extensive maintenance and testing are required
Solution Approach 1:
The invention segments the cooling functions by separating cold shutdown cooling from safety injection. The containment region flooding system dedicated to cold shutdown is simplified and requires minimal maintenance, while the safety injection system remains available for emergency situations. This functional segmentation reduces the complexity and maintenance burden of any single system while maintaining both safety and shutdown capabilities
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
Enables efficient and maintenance-reduced cooling of reactor modules to cold shutdown temperatures by utilizing natural circulation and external water flooding, independent of conventional cooling systems, facilitating safe and efficient reactor operations.
Implementation Method 1
transferring heat from primary coolant to secondary coolant that circulates through the steam generator
Implementation Method 2
releasing steam from a steam generator to reduce the temperature associated with a reactor pressure vessel
Implementation Method 3
at least partially flooding a containment region located between the reactor pressure vessel and a surrounding containment vessel... cooled down from the threshold cool-down temperature to a shutdown temperature
Data Source
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AI summary
A cooling system for a reactor module includes a reactor pressure vessel that houses primary coolant and a steam generator that lowers a temperature of the reactor pressure vessel by transferring heat from the primary coolant to a secondary coolant that circulates through the steam generator. The steam generator releases at least a portion of the secondary coolant as steam. Additionally, the cooling system includes a containment vessel that at least partially surrounds the reactor vessel in a containment region. The containment region is dry during normal operation of the reactor module. A controller introduces a source of water into the containment region in response to a non-emergency shut down of the reactor module. The source of water is located external to the containment vessel, and the water is introduced into the containment region after the steam generator has initially lowered the temperature of the reactor pressure vessel in response to releasing the steam.