Abstract
Magnetite particles deposited on the secondary side of a steam generator (SG) can degrade the integrity and performance of pressurized water reactors. Therefore, it is necessary to produce the data of fundamental interfacial electrokinetic properties of magnetite particles and SG tube materials. This study investigated the zeta potentials of magnetite nanoparticles and Alloy 690 surfaces, which were dependent on the pH value, pH agent, and the presence of NaCl. The zeta potentials of the magnetite nanoparticles increased in the negative direction as the pH increased, regardless of the pH agent. At the same pH value, the absolute values of the zeta potentials with different pH agents were: ethanolamine < ammonia < morpholine. In the presence of NaCl, the zeta potentials of the particles further increased negatively. The meaning of the measured zeta potentials was discussed in terms of the dispersion stability and the agglomeration of the particles. Based on the relationship between the zeta potentials of the particles and Alloy 690 surfaces, the magnetite deposition on Alloy 690 was also discussed. Furthermore, the empirical formulas for the pH-dependent zeta potentials of magnetite particles in each alkaline solution were suggested.
Highlights
Corrosion products of carbon steel and other structural materials in pressurized water reactors (PWRs) are released to the secondary water as a result of flow-accelerated corrosion [1,2]
It is expected that the amount of magnetite deposition on the Alloy 690 surfaces will decrease as the pH increases from 9.0 to 10.0, regardless of the pH agent
The empirical formulas for the zeta potentials of magnetite nanoparticles derived in the pH range from 9.0 to 10.0 at 25 ◦ C were as follows: ζE = −9.0 × pH + 57.5 for ETA; ζA = −10.2 × pH + 61.9 for ammonia; ζM = −12.3 × pH + 77.8 for morpholine
Summary
Corrosion products of carbon steel and other structural materials in pressurized water reactors (PWRs) are released to the secondary water as a result of flow-accelerated corrosion [1,2] These corrosion product particles are transported to steam generators (SGs) and attached to SG tubes to form deposits with a porous structure. Mitigating and inhibiting such magnetite deposition is a key to controlling the chemistry of secondary water for reliable PWR operation. Comparing the zeta potentials of magnetite particles and SG tube materials could prove useful for studying magnetite deposition behavior in the secondary side of SGs. The secondary side of PWRs is managed by a thorough pH control to suppress the corrosion of the structural materials of the secondary system.
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