Chemical Injection System for Nuclear Reactor Startup
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Solution Overview
Problem
Current systems for mitigating intergranular stress corrosion cracking (IGSCC) in nuclear power reactors are inefficient, as they require noble metal injection during hot standby, resulting in lost time and inability to inject hydrogen during startup, leading to crack propagation, and face issues with chemical deposition, concentration control, and pump failure due to harsh conditions.
Innovation Solution
An on-line injection system using positive displacement pumps to deliver a concentrated chemical solution, internally diluted before injection, which minimizes deposition loss, allows higher concentration use, eliminates labor-intensive dilution, raises solution pressure, prevents precipitation, and ensures continuous chemical delivery during reactor operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If chemical solution is injected during hot standby mode, then IGSCC mitigation is achieved, but reactor startup time is lost and productivity decreases
Solution Approach 1:
The system performs preliminary action by injecting chemical solution into the reactor during startup mode before power generation begins, rather than waiting for hot standby mode. This preliminary injection during the startup phase eliminates the need for subsequent injection during hot standby, thereby maintaining IGSCC mitigation while avoiding loss of startup time and improving overall productivity
2Object-affected harmful factors
If dilute chemical solution is used for injection, then main steam radiation increase is minimized, but chemical deposition loss increases and storage tank depletes frequently
Solution Approach 1:
The system changes the parameter of chemical solution concentration by using concentrate formulation instead of dilute solution. This parameter change allows the chemical to be injected in concentrated form during startup, which reduces chemical deposition loss in the steam lines while still controlling radiation increase through proper injection timing and dosage control
Solution Approach 2:
The system ensures continuous chemical injection throughout the startup mode and into the early operation phase, maintaining continuous protective action on crack surfaces. This continuous injection prevents chemical deposition loss by ensuring the chemical is delivered directly to the reactor internals rather than being lost in transit lines
3Loss of substance
If concentrated chemical solution is used for injection, then chemical deposition loss is reduced, but pump reliability decreases due to harsh operating conditions
Solution Approach 1:
The system introduces an intermediary cooling mechanism where the chemical solution is cooled before being injected into the reactor. This intermediary cooling step reduces the thermal stress on the injection pump components, allowing the pump to reliably handle concentrated chemical solution without failing due to the combined effects of high concentration and harsh operating conditions
4Reliability
If chemical injection is performed during startup mode, then crack surfaces are treated during critical period, but hydrogen injection capability is lost
Solution Approach 1:
The system achieves universality by designing a chemical injection system that can deliver multiple beneficial chemicals (including both noble metal compounds for IGSCC mitigation and hydrogen peroxide for oxygen control) through a single injection mechanism during startup mode. This multi-functional capability replaces the need for separate hydrogen injection systems, allowing crack surface treatment during the critical startup period while maintaining chemical versatility
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 uninterrupted chemical delivery to operating reactors, effectively treating new crack surfaces and maintaining optimal chemical concentration, reducing downtime and extending pump lifespan through controlled injection and specialized flush solutions.
Implementation Method 1
The process of delivery is via positive displacement pumps
Implementation Method 2
The injection of chemicals is in a concentrated solution form, which is internally diluted by the system prior to discharging from the skid
Implementation Method 3
noble metal solution is injected into a reactor to assist in the recombination of oxygen and hydrogen. As a catalyst, noble metal solution is injected into a reactor
Implementation Method 4
it raises the chemical solution to the pressure required for injection
Data Source
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AI summary
An injection system 10 designed to deliver a chemical solution into a reactor through feedwater system taps 22 during normal operating condition of a power reactor is disclosed. The process of delivery is via positive displacement pumps 12 and 14. Injection of chemical is in a concentrated solution form, which is internally diluted by the system 10 prior to discharging from the skid. The injection system 10 minimizes chemical loss due to deposition on the transit line 15, enables a higher concentrated solution to be used as the injectant, eliminates the time consuming laborious process of chemical dilution, raises chemical solution to the pressure required for injection, prevents solid precipitations out of solution at the injection pump head through the use of a flush solution, and deposits fresh chemical on new crack surfaces that develop during a power reactor start-up, shutdown and operation.