Abstract
In the secondary side of pressurized water reactors (PWRs), the main corrosion product accumulated on the steam generator (SG) tubes is magnetite, which has a porous structure. The purpose of this work is to simulate the porous magnetite deposited to the SG tubes using a loop system. We newly developed a circulating loop system for a porous magnetite deposition test. A test section was designed as a single hydraulic flow channel, and a cartridge heater was fabricated and mounted into a commercial SG tube to provide an equal heating source for the primary water. After the deposition test, the simulated magnetite deposits were characterized for comparison to real SG tube deposits collected from an operating PWR plant. The magnetite deposits produced using the loop system were appropriate for simulating the real SG tube deposits because the particle characteristics, phase, and porous morphology are closely similar to those of real deposit samples. Using the loop system, the chemical impurities such as Na and Cl can be easily concentrated within the pores of the simulated magnetite deposits. These simulated magnetite samples are expected to be widely utilized in various research fields such as the heat transfer degradation and magnetite accelerated corrosion of SG tubes.
Highlights
In the secondary coolant system of pressurized water reactors (PWRs), carbon steel, which exists in large numbers of pipings of steam generators (SGs), is greatly affected by the flow accelerated corrosion [1]
Afterwards, the chemical impurities are concentrated in the micro-pores of magnetite deposits [5,6,7], inducing the corrosion acceleration of SG tubes [8,9,10] owing to the formation of severe corrosive environments
The large pores with a diameter between about 6 and 8 μm were considered to be associated with steam chimneys or bubble growth
Summary
In the secondary coolant system of pressurized water reactors (PWRs), carbon steel, which exists in large numbers of pipings (i.e., feed-water lines, condensate components, separator drains, and heater drain systems) of steam generators (SGs), is greatly affected by the flow accelerated corrosion [1]. Afterwards, the chemical impurities are concentrated in the micro-pores of magnetite deposits [5,6,7], inducing the corrosion acceleration of SG tubes [8,9,10] owing to the formation of severe corrosive environments To prevent these problems owing to SG deposits, chemical [11] or mechanical cleanings [12] and high pH water treatment [13] of the secondary circuit have been developed and are widely used in the PWRs. Among them, chemical cleaning is currently the most effective strategy for removing the corrosion products in SGs. chemical cleaning is difficult to perform and could damage some parts of the SG owing to the corrosive properties of the chemical cleaning solution [4,12]. The concentration factors of Na and Cl within the deposits were evaluated and compared with previously reported ones
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