Nuclear Main Pump Shaft Seal Water Injection System
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Solution Overview
Problem
Existing main pump shaft seal water injection systems in nuclear power plants face issues such as ineffective exhaust, increased complexity due to multiple auxiliary pumps, inability to effectively isolate reactor coolant, lack of monitoring instruments, and system instability when high pressure coolers fail, leading to potential shutdowns.
Innovation Solution
A main pump shaft seal water injection system with a bypass pipeline and reduced auxiliary pumps, incorporating a pressure sensor for real-time monitoring, and a redundant design that allows for direct injection of low temperature water when high pressure coolers fail, ensuring continuous operation and reduced valve operations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If multiple auxiliary pumps are used in the shaft seal water injection system, then the reliability of cooling and lubrication is improved, but the device complexity and structural complexity increase
Solution Approach 1:
The patent combines the functions of multiple auxiliary pumps into a single auxiliary pump by integrating the cooling and lubrication functions. The single pump supplies water to both the shaft seal assembly and water lubricated radial bearing through a unified water injection system, reducing the number of components while maintaining reliable cooling and lubrication for both components.
Solution Approach 2:
The single auxiliary pump is designed to serve multiple functions simultaneously - it provides cooling water to the shaft seal assembly and lubrication water to the water lubricated radial bearing. This multi-functional design eliminates the need for separate pumps for each component, simplifying the overall system structure while ensuring reliable operation.
2Temperature
If high pressure cooler and jet pump are used for shaft seal water injection, then the cooling effect is improved, but the system stability deteriorates when cooler fails
Solution Approach 1:
The patent incorporates a bypass pipeline that allows the system to operate in different modes by changing flow parameters. Under normal conditions, water flows through the high pressure cooler for effective cooling. When the cooler fails, the bypass pipeline enables direct injection of cooling water without the cooler, allowing the system to maintain operation with reduced cooling capability rather than shutting down completely.
Solution Approach 2:
The bypass pipeline acts as an intermediary pathway between the auxiliary pump and the shaft seal assembly. It provides an alternative route for cooling water when the high pressure cooler is non-functional, serving as a mediator that maintains system operation during cooler failures and prevents complete system shutdown.
3Quantity of substance
If reactor coolant is used as ejection media for jet pump, then the available resources are improved, but the ability to isolate reactor coolant for maintenance deteriorates
Solution Approach 1:
The patent segments the water injection system into separate pathways - a main pipeline for normal operation and a bypass pipeline for maintenance mode. The bypass pipeline is equipped with isolation valves that can separate the jet pump and high pressure cooler from the reactor coolant system, allowing these components to be maintained or replaced without shutting down the entire reactor coolant system.
Solution Approach 2:
The bypass pipeline with isolation valves is pre-configured in the system design, allowing for easy isolation of the jet pump and high pressure cooler when maintenance is needed. This preliminary arrangement of isolation mechanisms enables rapid switching between operational and maintenance modes without complex procedures.
4Measurement precision
If monitoring instruments are added to the shaft seal water injection system, then the measurement capability is improved, but the device complexity increases
Solution Approach 1:
The patent replaces complex mechanical monitoring systems with simple pressure sensors that can be easily integrated into the water injection system. These sensors monitor the pressure of cooling water in the bypass pipeline and injection water in the main pipeline, providing essential system status information through simple electrical signals rather than complex mechanical measurement devices.
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 system ensures reliable and safe operation of the main pump by providing redundant shaft seal injection water under various conditions, reducing complexity and improving maintainability, and enabling effective isolation and monitoring of reactor coolant.
Implementation Method 1
The working media of the jet pump 20 is a low temperature upper filling water from the RCV system and the ejection media is a high temperature reactor coolant at the back of the impeller 13 in the main pump, both of which are mixed in the jet pump 20
Implementation Method 2
both of which are mixed in the jet pump 20, and then flows through the shaft seal water injection hole of the main flange 14 into the shaft seal chamber 15 after cooled by the high pressure cooler 22
Implementation Method 3
after cooled by the high pressure cooler 22 and filtered by the hydrocyclone 21
Implementation Method 4
after cooled by the high pressure cooler 22 and filtered by the hydrocyclone 21
Implementation Method 5
The pressure is increased by the action of the other auxiliary pump 25
Data Source
AI summary
A main pump shaft seal water injection system of a nuclear power plant includes a jet pump, a high pressure cooler, a hydrocyclone, valves and a main connection pipeline outside of a main pump, and an auxiliary pump and an internal flow path inside the main pump. Inner and outer flow paths of the main pump are connected with a shaft seal water injection hole and a high temperature water drainage hole. The main connection pipeline is connected between an upper filling water pipeline and a shaft seal water injection hole. A bypass pipeline connected with the jet pump, the high pressure cooler and the hydrocyclone, the main connection pipeline is provided with a normally open main pipeline isolating valve. The bypass pipeline allows low temperature upper filling water in the RCV system to enter the shaft seal water injection hole of the main flange directly.