Near-Field Transport of 129I from a Point Source in an In-Room Disposal Vault

1994 ◽  
Vol 353 ◽  
Author(s):  
Miroslav Kolář ◽  
Dennis M. Leneveu ◽  
Lawrence H. Johnson
Keyword(s):  
Mass Transport ◽  
Point Source ◽  
Groundwater Flow ◽  
Near Field ◽  
Single Point ◽  
Boundary Integral ◽  
Boundary Integral Method ◽  
Field Mass ◽  
Release Rates ◽  
Manufacturing Defects

AbstractA very small number of disposal containers of heat generating nuclear waste may have initial manufacturing defects that would lead to pin-hole type failures at the time of or shortly after emplacement. For sufficiently long-lived containers, only the the initial defects need be considered in modelling of release rates from the disposal vault. Two approaches to modelling of near-field mass transport from a single point source within a disposal room have been compared: the finite-element code MOTIF (A Model Of Transport In Fractured/porous media) and a boundary integral method (BIM). These two approaches were found to give identical results for a simplified model of the disposal room without groundwater flow. MOTIF has been then used to study the effects of groundwater flow on the mass transport out of the emplacement room.

scholarly journals Spectral boundary integral method for simulating static and dynamic fields from a fault rupture in a poroelastodynamic solid

2021 ◽  
Author(s):  
Elias Heimisson ◽  
Antonio Pio Rinaldi
Keyword(s):  
Pore Pressure ◽  
Integral Method ◽  
Near Field ◽  
Boundary Integral ◽  
Pressure Response ◽  
Boundary Integral Method ◽  
P Wave ◽  
Computational Time ◽  
Far Field ◽  
Pore Pressure Response

The spectral boundary integral method is popular for simulating fault, fracture, and frictional processes at a planar interface. However, the method is less commonly used to simulate off-fault dynamic fields. Here we develop a spectral boundary integral method for poroelastodynamic solid. The method has two steps: first, a numerical approximation of a convolution kernel and second, an efficient temporal convolution of slip speed and the appropriate kernel. The first step is computationally expensive but easily parallelizable and scalable such that the computational time is mostly restricted by computational resources. The kernel is independent of the slip history such that the same kernel can be used to explore a wide range of slip scenarios. We apply the method by exploring the short-time dynamic and static responses: first, with a simple source at intermediate and far-field distances and second, with a complex near-field source. We check if similar results can be attained with dynamic elasticity and undrained pore-pressure response and conclude that such an approach works well in the near-field but not necessarily at an intermediate and far-field distance. We analyze the dynamic pore-pressure response and find that the P-wave arrival carries a significant pore pressure peak that may be observed in high sampling rate pore-pressure measurements. We conclude that a spectral boundary integral method may offer a viable alternative to other approaches where the bulk is discretized, providing a better understanding of the near-field dynamics of the bulk in response to finite fault ruptures.

The Effect of Precipitation Fronts Induced by Radionuclide Chain Decay and Elemental Solubility Limits on Near-Field Mass Transport

1991 ◽  
Vol 257 ◽  
Author(s):  
Karen J. Worcan ◽  
Michael J. Apted
Keyword(s):  
Mass Transport ◽  
Near Field ◽  
Field Mass ◽  
Bentonite Buffer ◽  
Diffusional Mass ◽  
High Level Nuclear Waste ◽  
Uranium Plutonium ◽  
High Level ◽  
Chain Decay ◽  
Diffusional Mass Transport

ABSTRACTThe formation and impact of precipitation fronts on the diffusional mass transport of radionuclides from a high-level nuclear waste canister through a bentonite buffer has been investigated in a series of numerical simulations. The precipitation fronts arise from chain decay and ingrowth, coupled with differences in elemental solubility limits and sorption properties. The fronts influence particularly the behavior of uranium, plutonium and neptunium isotopes. The isotopic concentration profiles across the buffer differ considerably from results obtained with models that employ elemental solubility limits simply as a boundary condition at the waste-bentonite interface.

Uniform Horizontal Groundwater Flow against Dispersion in a Shallow Aquifer: Two Analytical Models

1992 ◽  
Vol 23 (1) ◽  
pp. 1-12
Author(s):  
Ram Raj Vinda ◽  
Raja Ram Yadava ◽  
Naveen Kumar
Keyword(s):  
Point Source ◽  
Groundwater Flow ◽  
Cross Section ◽  
Analytical Solutions ◽  
Concentration Distribution ◽  
Analytical Models ◽  
Shallow Aquifer ◽  
Horizontal Cross Section ◽  
Flow Components ◽  
Reactive Pollutant

Analytical solutions converging rapidly at large and small values of times have been obtained for two mathematical models which describe the concentration distribution of a non reactive pollutant from a point source against the flow in a horizontal cross-section of a finite saturated shallow aquifer possessing uniform horizontal groundwater flow. Zero concentration or the conditions in which the flux across the extreme boundaries are proportional to the respective flow components are applied. The effects of flow and dispersion on concentration distribution are also discussed.

scholarly journals Flow Turbulence Characteristics and Mass Transport in the Near-Wake Region of an Aquaculture Cage Net Panel

Water ◽  
2021 ◽  
Vol 13 (3) ◽  
pp. 294
Author(s):  
Dongdong Shao ◽  
Li Huang ◽  
Ruo-Qian Wang ◽  
Carlo Gualtieri ◽  
Alan Cuthbertson
Keyword(s):  
Mass Transport ◽  
Near Field ◽  
Lateral Spreading ◽  
Wake Flow ◽  
Wake Region ◽  
Near Wake ◽  
Turbulence Characteristics ◽  
Macro Scale ◽  
Flow Turbulence ◽  
Fish Cages

Cage-based aquaculture has been growing rapidly in recent years. In some locations, cage-based aquaculture has resulted in the clustering of large quantities of cages in fish farms located in inland lakes or reservoirs and coastal embayments or fjords, significantly affecting flow and mass transport in the surrounding waters. Existing studies have focused primarily on the macro-scale flow blockage effects of fish cages, and the complex wake flow and associated near-field mass transport in the presence of the cages remain largely unclear. As a first step toward resolving this knowledge gap, this study employed the combined Particle Image Velocimetry and Planar Laser Induced Fluorescence (PIV-PLIF) flow imaging technique to measure turbulence characteristics and associated mass transport in the near wake of a steady current through an aquaculture cage net panel in parametric flume experiments. In the near-wake region, defined as ~3M (mesh size) downstream of the net, the flow turbulence was observed to be highly inhomogeneous and anisotropic in nature. Further downstream, the turbulent intensity followed a power-law decay after the turbulence production region, albeit with a decay exponent much smaller than reported values for analogous grid-generated turbulence. Overall, the presence of the net panel slightly enhanced the lateral spreading of the scalar plume, but the lateral distribution of the scalar concentration, concentration fluctuation and transverse turbulent scalar flux exhibited self-similarity from the near-wake region where the flow was still strongly inhomogeneous. The apparent turbulent diffusivity estimated from the gross plume parameters was found to be in reasonable agreement with the Taylor diffusivity calculated as the product of the transverse velocity fluctuation and integral length scale, even when the plume development was still transitioning from a turbulent-convective to turbulent-diffusive regime. The findings of this study provide references to the near-field scalar transport of fish cages, which has important implications in the assessment of the environmental impacts and environmental carrying capacity of cage-based aquaculture.

scholarly journals Nonlinear two-dimensional free surface solutions of flow exiting a pipe and impacting a wedge

2021 ◽  
Vol 126 (1) ◽  
Author(s):  
Alex Doak ◽  
Jean-Marc Vanden-Broeck
Keyword(s):  
Surface Tension ◽  
Integral Equation ◽  
Free Surface ◽  
Boundary Integral ◽  
Boundary Integral Method ◽  
Two Dimensional ◽  
Numerical Schemes ◽  
Additional Advantage ◽  
Infinite Wedge ◽  
Good Agreement

AbstractThis paper concerns the flow of fluid exiting a two-dimensional pipe and impacting an infinite wedge. Where the flow leaves the pipe there is a free surface between the fluid and a passive gas. The model is a generalisation of both plane bubbles and flow impacting a flat plate. In the absence of gravity and surface tension, an exact free streamline solution is derived. We also construct two numerical schemes to compute solutions with the inclusion of surface tension and gravity. The first method involves mapping the flow to the lower half-plane, where an integral equation concerning only boundary values is derived. This integral equation is solved numerically. The second method involves conformally mapping the flow domain onto a unit disc in the s-plane. The unknowns are then expressed as a power series in s. The series is truncated, and the coefficients are solved numerically. The boundary integral method has the additional advantage that it allows for solutions with waves in the far-field, as discussed later. Good agreement between the two numerical methods and the exact free streamline solution provides a check on the numerical schemes.

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