scholarly journals Flow-Accelerated Corrosion of Type 316L Stainless Steel Caused by Turbulent Lead–Bismuth Eutectic Flow

Metals ◽  
2018 ◽  
Vol 8 (8) ◽  
pp. 627 ◽  
Author(s):  
Tao Wan ◽  
Shigeru Saito
Keyword(s):  
Mass Transfer ◽  
Stainless Steel ◽  
Transfer Coefficient ◽  
Mass Transfer Coefficient ◽  
316L Stainless Steel ◽  
Straight Tube ◽  
Accelerated Corrosion ◽  
Corrosion Depth ◽  
Cfd Analyses ◽  
Flow Accelerated Corrosion

Lead–bismuth eutectic (LBE), a heavy liquid metal, is an ideal candidate coolant material for Generation-IV fast reactors and accelerator-driven systems (ADSs), but LBE is also known to pose a considerable corrosive threat to its container. However, the susceptibility of the candidate container material, 316L stainless steel (SS), to flow-accelerated corrosion (FAC) under turbulent LBE flow, is not well understood. In this study, an LBE loop, referred to as JLBL-1, was used to experimentally study the behavior of 316L SS when subjected to FAC for 3000 h under non-isothermal conditions. An orificed tube specimen, consisting of a straight tube that abruptly narrows and widens at each end, was installed in the loop. The specimen temperature was 450 °C, and a temperature difference between the hottest and coldest legs of the loop was 100 °C. The oxygen concentration in the LBE was lower than 10−8 wt %. The Reynolds number in the test specimen was approximately 5 × 104. The effects of various hydrodynamic parameters on FAC behavior were studied with the assistance of computational fluid dynamics (CFD) analyses, and then a mass transfer study was performed by integrating a corrosion model into the CFD analyses. The results show that the local turbulence level affects the mass concentration distribution in the near-wall region, and therefore, the mass transfer coefficient across the solid/liquid interface. The corrosion depth was predicted on the basis of the mass transfer coefficient obtained in the numerical simulation and was compared with that obtained in the loop. For the abrupt narrow part, the predicted corrosion depth was comparable with the measured corrosion depth, as was the abrupt wide part after involving the wall roughness effects in the prediction; for the straight tube part, the predicted corrosion depth is about 1.3–3.5 times the average experimental corrosion depth, and the possible reason for this discrepancy was provided.

Flow and Mass Transfer in Bends Under Flow-Accelerated Corrosion Wall Thinning Conditions

2009 ◽  
Author(s):  
John M. Pietralik ◽  
Chris S. Schefski
Keyword(s):  
Mass Transfer ◽  
Transfer Coefficient ◽  
Mass Transfer Coefficient ◽  
Flow Conditions ◽  
Ferrous Ions ◽  
Local Flow ◽  
Accelerated Corrosion ◽  
Flow Effects ◽  
Flow Accelerated Corrosion

The three groups of parameters that affect flow-accelerated corrosion (FAC) are flow conditions, water chemistry, and materials. Nuclear power plant (NPP) data and laboratory tests confirm that under alkaline water chemistry there is a close relationship between local flow conditions and FAC rates in piping components. The knowledge of local flow effects can be useful for developing targeted inspection plans for piping components, predicting the location of the highest FAC rate for a given piping component, and determining what piping components should be replaced. A similar evaluation applies also to FAC in heat transfer equipment such as heat exchangers and steam generators. The objective of this paper is to examine the role of flow and mass transfer in bends under FAC conditions. Bends experience increased FAC rates compared to straight pipes, and are the most common components in piping systems. When the flow effects are dominant, the FAC rate is proportional to the mass flux of ferrous ions, which, in turn, is proportional to the mass transfer coefficient in the flowing water. The mass transfer coefficient describes the intensity of the transport of corrosion products (ferrous ions) from the oxide-water interface into the bulk water. Therefore, this parameter can be used for predicting the local distribution of the FAC rate. The current paper presents plant and laboratory evidence of the relationship between local mass transfer conditions and the FAC rate in bends. It shows correlations for mass transfer coefficients in bends and reviews the most important flow parameters affecting the mass transfer coefficient. The role of bend geometry and, in particular, the short and long radii, surface roughness, wall shear stress, and local turbulence is discussed. Computational fluid dynamics calculations and plant artefact measurements for short-radius and long radius bends are presented. The effect of the close proximity of two bends on FAC rate is also examined based on CANDU™ NPP inspection data and compared with literature data.

CFD Application to Flow-Accelerated Corrosion in Feeder Bends

2006 ◽  
Author(s):  
John M. Pietralik ◽  
Bruce A. W. Smith
Keyword(s):  
Mass Transfer ◽  
Mass Transport ◽  
Transfer Coefficient ◽  
Mass Transfer Coefficient ◽  
Oxide Layer ◽  
Operating Conditions ◽  
Local Flow ◽  
Accelerated Corrosion ◽  
Wall Functions ◽  
Flow Accelerated Corrosion

Feeder piping in CANDU® plants experiences a thinning degradation mechanism called Flow-Accelerated Corrosion (FAC). The piping is made of carbon steel and has high water flow speeds. Although the water chemistry is highly alkaline with room-temperature pH in a range of 10.0–10.5, the piping has FAC rates exceeding 0.1 mm/year in some locations, e.g., in bends. One of the most important parameters affecting the FAC rate is the mass transfer coefficient for convective mass transport of ferrous ions. The ions are created at the pipe wall as a result of corrosion, diffuse through the oxide layer, and are transported from the oxide-layer/water interface to the bulk water by mass transport. Consequently, the local flow characteristics contribute to the highly turbulent convective mass transfer. Plant data and laboratory experiments indicate that the mass transfer step dominates FAC under feeder conditions. In this study, the flow and mass transfer in a feeder bend under operating conditions were simulated using the Fluent™ computer code. Because the flow speed is very high, with the Reynolds numbers in a range of several millions, and because the geometry is complex, experiments in a 1:1 scale were conducted with the main objective to validate flow simulations. The experiments measured pressure at several key locations and visualized the flow. The flow and mass transfer models were validated using available friction-factor and mass transfer correlations and literature experiments on mass transfer in a bend. The validation showed that the turbulence model that best predicts the experiments is the realizable k-ε model. Other two-equation turbulence models, as well as one-equation models and Reynolds stress models were tried. The near-wall treatment used the non-equilibrium wall functions. The wall functions were modified for surface roughness when necessary. A comparison of the local mass transfer coefficient with measured FAC rate in plant specimens shows very good agreement. Visualization experiments indicate secondary flows in the bends. No boundary layer separation was observed in experiments or in simulations.

The Effect of Flow Field on the Mass Transfer Coefficient in the Orifice Downstream

2012 ◽  
Author(s):  
Atsushi Fujishiro ◽  
Feng Shan ◽  
Retsu Kojo ◽  
Momoe Takeuchi ◽  
Yoshiyuki Tsuji
Keyword(s):  
Mass Transfer ◽  
Flow Field ◽  
Transfer Coefficient ◽  
Mass Transfer Coefficient ◽  
Swirling Flow ◽  
Thermal Power ◽  
Mass Transfer Rate ◽  
Cross Sectional ◽  
Accelerated Corrosion ◽  
Piv Measurement

Flow accelerated corrosion (FAC) caused many accidents of nuclear energy or thermal-power-generation plants. The main cause of FAC is known as promotion of mass transfer from the wall by the turbulence accompanied by separation, reattachment, and rotating of the flow. However, the relation between mass transfer and flow field is not clarified. In this study, we investigate the relation between the flow field behind the orifice and the mass transfer rate by means of PIV measurement and electrochemical method. It is concluded that the mass transfer coefficient is scaled by the cross-sectional averaged velocity at the orifice UD and the parameter Res in an interaction with a swirling flow.

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