Defense in Depth Safety for Nuclear Reactor Heat Removal
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional nuclear reactor safety systems often lead to automatic reactor depressurization upon detection of a safety event, which can deplete the ultimate heat sink and complicate recovery processes, necessitating a more controlled approach to maintain the reactor within a safe operational envelope without immediate depressurization.
Innovation Solution
The implementation of a 'defense in depth' strategy that includes a pressure-hardened reactor coolant inventory and purification system (RCI) with high-pressure components and an air-cooled auxiliary condenser, allowing for heat removal at elevated pressures without depressurizing the reactor, along with additional safety measures like isolation valves and passive thermal communication with the ultimate heat sink, to manage safety events effectively.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional safety systems automatically depressurize the reactor upon detecting a safety event, then the reactor is quickly brought to a safe state, but the ultimate heat sink is depleted and recovery processes are complicated
Solution Approach 1:
The patent segments the heat removal function into multiple independent systems: the primary RCI system for normal operation and the auxiliary condenser system for safety events. This segmentation allows the ultimate heat sink to be preserved while safety functions are handled by the auxiliary system, resolving the contradiction between rapid safety response and heat sink preservation.
Solution Approach 2:
The auxiliary condenser system acts as an intermediary between the reactor and the ultimate heat sink during safety events. It provides a buffer that handles heat removal temporarily, preventing direct depletion of the ultimate heat sink while maintaining reactor safety. The intermediary system can operate independently or in conjunction with the primary system.
2Reliability
If the reactor is immediately depressurized during a safety event, then safety is prioritized, but operational control is reduced and recovery is complicated
Solution Approach 1:
The patent implements dynamic control capabilities where operators can adjust the response based on the specific safety event conditions. The system can transition between different operational modes (normal RCI operation, auxiliary condenser operation, or combined operation) providing flexible control that maintains ease of operation while ensuring safety. This dynamic approach avoids the rigidity of automatic immediate depressurization.
Solution Approach 2:
The system allows for parameter changes in the heat removal process, enabling operators to modulate the rate and extent of heat removal based on conditions. Rather than fixed immediate depressurization, the system can adjust pressure and temperature parameters dynamically, maintaining operational control while responding to safety events effectively.
3Adaptability or versatility
If high pressure components are added to the RCI system to enable heat removal without depressurization, then operational flexibility is improved, but device complexity increases
Solution Approach 1:
The auxiliary condenser system is pre-configured and ready for immediate deployment when safety events occur. The high pressure components are prepared in advance, allowing the system to switch to pressure-retained operation without requiring complex real-time modifications. This preliminary preparation reduces the perceived complexity during actual operation.
Solution Approach 2:
The auxiliary condenser system serves as a temporary, dedicated safety system that is used only during safety events. Rather than making the entire RCI system complex and pressure-hardened, a separate auxiliary system is added that can be deployed temporarily, handled safely, and then deactivated, reducing the overall complexity burden on the primary system.
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 approach enables the reactor to manage safety events without immediate depressurization, extending the useful life of the ultimate heat sink and reducing the load on it, thereby facilitating safer and more controlled reactor operations and recovery processes.
Implementation Method 1
an air-cooled auxiliary condenser, allowing for heat removal at elevated pressures without depressurizing the reactor
Implementation Method 2
passive thermal communication with the ultimate heat sink
Data Source
AI summary
A nuclear reactor includes a nuclear reactor core disposed in a pressure vessel and immersed in primary coolant water at an operating pressure higher than atmospheric pressure. A containment structure contains the nuclear reactor. A reactor coolant inventory and purification system (RCI) is connected with the pressure vessel by make-up and letdown lines. The RCI includes a high pressure heat exchanger configured to operate responsive to a safety event at the operating pressure to remove heat from the primary coolant water in the pressure vessel. An auxiliary condenser located outside containment also removes heat. The RCI also includes a pump configured to inject make up water into the pressure vessel via the make-up line against the operating pressure. An emergency core cooling system (ECC) operates to depressurize the nuclear reactor only if the RCI and auxiliary condenser are unable to manage the safety event.