Effects of Advanced Amines on Magnetite Deposition of Steam Generator Tubes in Secondary System

Abstract

Ethanolamine (ETA) is widely used to control the pH value in the secondary water of pressurized water reactors. However, it is necessary to consider other advanced amines which can replace ETA due to its serious human hazards and environmental treatment problems. The purpose of this study is to contemplate the effects of three advanced amines (ETA, 3-methoxypropylamine (MPA), and dimethylamine (DMA)) on the magnetite deposition behavior of a thermally treated (TT) Alloy 690 tubes by using a steam generator (SG) tube fouling loop in simulated secondary water. All particles were identified as a magnetite and were polyhedral or spherical in shape. When using ETA, MPA, and DMA, the average porosity of the deposits was about 34.7%, 33.0%, and 24.6%, respectively. The amount of deposits was largest when ETA was added, and it decreased by 41% when adding MPA and 55% when adding DMA. The mechanism of magnetite deposition was discussed in terms of zeta potentials of both the magnetite particles and the Alloy 690TT surface and magnetite solubility depending on the amines. To compare the potential for replacing ETA with other advanced amines, the various factors such as SG integrity, human hazards, and environmental treatment problems were discussed.

Magnetite Deposition Behavior on Alloy 600 and Alloy 690 Tubes in Simulated PWR Secondary Water

“…In previous research, some parameters affecting the deposition of colloid particles on metal surface have been reported. The parameters include thermal hydraulic conditions (temperature, pressure, heat flux, velocity), water chemistry conditions (pH value, pH agent, DO), factors related to the particles (size, concentration, zeta potential, solubility), and surface characteristics (surface zeta potential, wettability, surface roughness) [6,[14][15][16]45].…”

“…That is, where the zeta potential of a metal surface has the same sign as that of the particles, a repulsive force acts between the metal and the particles. Some researchers have presented that the number of particles deposited on a metal surface is strongly affected by the difference in the zeta potentials of the metal surfaces and particles [14][15][16]24].…”

“…Recently, investigations on the magnetite deposition onto the surface of SG tubes have been reported from the viewpoint of water chemistry factors such as pH control amines and chemical impurities [14][15][16]. These studies found that the amount of magnetite deposits is strongly dependent on the pH control agents and is reduced in the order of ethanolamine > morpholine > ammonia [14].…”

“…These studies found that the amount of magnetite deposits is strongly dependent on the pH control agents and is reduced in the order of ethanolamine > morpholine > ammonia [14]. Lee et al [15] reported that dimethylamine was beneficial to mitigate SG tube fouling compared to ethanolamine and 3-methoxypropylamine. The ingress of sodium chloride as an impurity into feedwater decreased the particle size and quantity of magnetite deposits [16].…”

Deposition of Colloidal Magnetite on Stainless Steel in Simulated Steam Generator Conditions—Experiments and Modeling

“…Despite considerable research efforts on the subject in recent years [5][6][7][8][9][10][11][12], currently, no generally applicable models of sludge deposition and consolidation processes have been proposed. The development of this type of model would include a quantitative assessment of the possibilities of minimizing the formation of magnetite particles and their deposition on the SG surfaces by optimizing the water chemistry and hydrodynamics (assessing the influence of different types of amines, the use of dispersants, etc.).…”