Primary Loop Zinc Ion Screening for Hot Functional Tests
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
The existing zinc injection technologies in nuclear power plants struggle to determine the optimal zinc ion concentration during the hot functional test, leading to potential fouling-induced localized corrosion and increased radiation dose rates due to the formation of established oxide films on primary loop equipment.
Innovation Solution
A screening method involving an autoclave simulation of the hot functional test environment, with zinc ion concentrations ranging from 20 ppb to 250 ppb, followed by electrochemical impedance testing to identify optimal zinc ion concentrations that minimize corrosion and reduce radiation dose rates, using electrochemical impedance trend charts to determine the optimal range.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If zinc injection is performed during hot functional test with high zinc ion concentration (20-100 ppb as per guidelines), then the oxide film density is improved and corrosion protection is enhanced, but the risk of fouling-induced localized corrosion and core power excursions increases due to additional release of dissolved corrosion products
Solution Approach 1:
The patent applies parameter changes by adjusting the zinc ion concentration from the conventional 20-100 ppb range to a lower range of 1-50 ppb specifically for hot functional test conditions. This parameter modification allows the system to achieve corrosion protection benefits while avoiding the harmful effects of excessive zinc concentration, such as fouling-induced corrosion and core power excursions. The optimized concentration range is determined through electrochemical impedance spectroscopy measurements that evaluate oxide film quality at different zinc levels.
Solution Approach 2:
The patent implements preliminary action by performing zinc injection during the hot functional test period, which occurs before the reactor enters commercial operation. This timing allows the zinc ions to modify the oxide film formation process from the beginning, creating a protective film structure that prevents subsequent corrosion and reduces radioactive contamination, rather than attempting to treat established corrosion problems after they occur.
2Reliability
If zinc injection is performed during hot functional test, then the dose rate reduction and corrosion mitigation are significantly improved, but the optimal zinc ion concentration range is unclear due to lack of established oxide films
Solution Approach 1:
The patent replaces traditional mechanical/chemical trial-and-error methods with electrochemical impedance spectroscopy (EIS) technology to determine the optimal zinc ion concentration. EIS provides precise, non-destructive measurement of oxide film properties, allowing the system to identify the optimal zinc concentration range (1-50 ppb) by measuring impedance changes that correlate with film quality, rather than relying on empirical observations or destructive testing methods.
Solution Approach 2:
The patent introduces electrochemical impedance spectroscopy as an intermediary measurement tool that bridges the gap between zinc ion concentration and oxide film quality assessment. The EIS technique measures the electrical impedance of the oxide film, which serves as an intermediate parameter that correlates with both corrosion resistance and zinc concentration, enabling precise determination of the optimal zinc injection level without direct observation of corrosion or radioactive contamination.
3Object-affected harmful factors
If conventional zinc injection concentration (2-15 ppb) is used in loaded nuclear power plants with established oxide films, then the risk of fouling-induced corrosion is reduced, but the effectiveness in mitigating corrosion and reducing dose rate is insufficient compared to pre-loading injection
Solution Approach 1:
The patent applies local quality by recognizing that different operational stages require different zinc injection strategies. For hot functional test conditions (pre-loading), a higher zinc concentration range of 1-50 ppb is optimal for forming protective oxide films from scratch. For loaded plants with established oxide films, the lower conventional range of 2-15 ppb is appropriate to maintain film stability without causing fouling. This localized optimization of zinc concentration according to operational stage resolves the contradiction between effectiveness and risk.
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 method provides a systematic and accurate determination of the optimal zinc ion concentration range, reducing corrosion and radiation dose rates by enhancing the denseness of the oxide film, thereby improving the safety and operational efficiency of nuclear power plants.
Implementation Method 1
the zinc ions can replace the radionuclides in the oxide film, such that these ions are released into the coolant
Implementation Method 2
the zinc ions can also occupy the inter-crystalline position of the released metal ions, such that the oxide film is denser
Implementation Method 3
performing an electrochemical impedance test on the test specimen, plotting an electrochemical impedance trend chart of the test specimen over different zinc ion concentrations
Data Source
AI summary
The disclosure relates to the field of nuclear power energy technology, and specifically relates to a screening method for an optimal zinc ion concentration in the primary loop during the hot functional test of a nuclear power plant. Unlike the study of zinc injection in primary loop during pre-critical and power operation of a nuclear power plant, the disclosure is directed to the study of optimal zinc injection concentration during the hot functional test. Specifically, in the disclosure, a hot functional test environment is simulated by an autoclave, and the optimal zinc ion concentration range is identified by impedance experiments on test specimens with film formation in the autoclave. The method is highly representative of tests, with clear data trends, high experimental visibility and evaluability, which provides a screening method for the optimal zinc ion concentration in the primary loop during the hot functional test of a nuclear power plant.