Natural and Engineered Barriers in a Romanian Disposal Site for Low and Intermediate Level Waste

2003 ◽  
Author(s):  
Daniela Diaconu ◽  
Kay Birdsell ◽  
George Zyvoloski
Keyword(s):  
Contaminant Transport ◽  
Vadose Zone ◽  
Nuclear Power ◽  
Water Movement ◽  
Intermediate Level ◽  
Danube River ◽  
Disposal Site ◽  
Near Surface ◽  
River Level ◽  
Engineered Barriers

The operational waste generated by the Cernavoda Nuclear Power Plant will be disposed in a near-surface facility. The low and intermediate level wastes, containing particularly large concentrations of C-14 and H-3, are treated and conditioned in steel drums, which will be placed in the disposal cells and then immobilized in concrete. The Saligny site has been proposed for LIL waste disposal. Geologically, the main components of this site are the quaternary loess, the Precambrian and pre-quaternary clays, and the Eocene and Barremian limestones. Hydrologically, the site can be divided into a vadose zone down to 45–50m and three distinct aquifers, two of them in the limestone beds and the third into the lenses of sand and limestone existing in the pre-quaternary clay layer. Preliminary performance assessments, presented in this paper, indicate that the geologic layers are efficient natural barriers against water flow and radionuclide migration from the vadose zone to the Barremian aquifer. The semi-arid climate and the low precipitation rate prevent contaminant transport from the disposal site to the Eocene aquifer. FEHM simulations of transient groundwater flow showed that seasonal variations influence the moisture content profile in the top of the vadose zone, but the influence over the long term is not significant for contaminant transport. The Danube River level variations control water movement in the Barremian aquifer, especially in the upper part where the limestone is highly fractured and water moves toward the river when its level is low and toward the site when the river level is high. The disposal concept tries to combine the natural and engineered barriers in order to ensure the safety of the environment and population. Therefore, the concrete filling the disposal cells surrounds the waste with a medium that facilitates C-14 retention by precipitation, thus reducing the C-14 releases in the atmosphere and geosphere.

scholarly journals Development of Predictive Tools for Contaminant Transport through Variably-Saturated Heterogeneous Composite Porous Formations

2012 ◽  
Author(s):  
David Russo ◽  
Daniel M. Tartakovsky ◽  
Shlomo P. Neuman
Keyword(s):  
Contaminant Transport ◽  
Water Flow ◽  
Vadose Zone ◽  
Practical Importance ◽  
Computational Method ◽  
Computational Framework ◽  
Near Surface ◽  
Flow And Transport ◽  
Subsurface Environments ◽  
Heterogeneous Formations

The vadose (unsaturated) zone forms a major hydrologic link between the ground surface and underlying aquifers. To understand properly its role in protecting groundwater from near surface sources of contamination, one must be able to analyze quantitatively water flow and contaminant transport in variably saturated subsurface environments that are highly heterogeneous, often consisting of multiple geologic units and/or high and/or low permeability inclusions. The specific objectives of this research were: (i) to develop efficient and accurate tools for probabilistic delineation of dominant geologic features comprising the vadose zone; (ii) to develop a complementary set of data analysis tools for discerning the fractal properties of hydraulic and transport parameters of highly heterogeneous vadose zone; (iii) to develop and test the associated computational methods for probabilistic analysis of flow and transport in highly heterogeneous subsurface environments; and (iv) to apply the computational framework to design an “optimal” observation network for monitoring and forecasting the fate and migration of contaminant plumes originating from agricultural activities. During the course of the project, we modified the third objective to include additional computational method, based on the notion that the heterogeneous formation can be considered as a mixture of populations of differing spatial structures. Regarding uncertainly analysis, going beyond approaches based on mean and variance of system states, we succeeded to develop probability density function (PDF) solutions enabling one to evaluate probabilities of rare events, required for probabilistic risk assessment. In addition, we developed reduced complexity models for the probabilistic forecasting of infiltration rates in heterogeneous soils during surface runoff and/or flooding events Regarding flow and transport in variably saturated, spatially heterogeneous formations associated with fine- and coarse-textured embedded soils (FTES- and CTES-formations, respectively).We succeeded to develop first-order and numerical frameworks for flow and transport in three-dimensional (3-D), variably saturated, bimodal, heterogeneous formations, with single and dual porosity, respectively. Regarding the sampling problem defined as, how many sampling points are needed, and where to locate them spatially in the horizontal x₂x₃ plane of the field. Based on our computational framework, we succeeded to develop and demonstrate a methdology that might improve considerably our ability to describe quntitaively the response of complicated 3-D flow systems. The results of the project are of theoretical and practical importance; they provided a rigorous framework to modeling water flow and solute transport in a realistic, highly heterogeneous, composite flow system with uncertain properties under-specified by data. Specifically, they: (i) enhanced fundamental understanding of the basic mechanisms of field-scale flow and transport in near-surface geological formations under realistic flow scenarios, (ii) provided a means to assess the ability of existing flow and transport models to handle realistic flow conditions, and (iii) provided a means to assess quantitatively the threats posed to groundwater by contamination from agricultural sources.

Performance Analysis of a Repository for Low and Intermediate Level Reactor Waste

1986 ◽  
Vol 84 ◽  
Author(s):  
Timo Vieno ◽  
Henrik Nordman ◽  
Seppo Vuori ◽  
Esko Peltonen
Keyword(s):  
Power Plant ◽  
Performance Analysis ◽  
Nuclear Power ◽  
Nuclear Energy ◽  
Fixed Time ◽  
Intermediate Level ◽  
Time Points ◽  
Safety Margins ◽  
Engineered Barriers ◽  
Flexible Model

AbstractIn Finland, utilities producing nuclear energy are responsible for the management of the radioactive waste, including final disposal. As regards low and intermediate level waste, the approach has been adopted to employ the power plant sites for locations of repositories. The repositories will be excavated at the depth of about 50 to 125 m in the bedrock of the two Finnish nuclear power plant sites, Loviisa and Olkiluoto.The performance analysis presented in this paper has been carried out for the Preliminary Safety Analysis Report (PSAR) of the Olkiluoto reposi- tory. A flexible model has been developed to estimate the release of radio- nuclides from waste packages and their subsequent transport through the engi- neered barriers in the repository. Gradual degradation of the engineered barriers is accounted for by altering parameters at fixed time points. Safety margins of the disposal concept have been evaluated by including disturbed evolution scenarios in the analysis.

The Effects of Ion Implantation on the Surface Features of Inconel 600

1985 ◽  
Vol 43 ◽  
pp. 288-289
Author(s):  
John D. Rubio
Keyword(s):  
Grain Boundary ◽  
Ion Implantation ◽  
Nuclear Power ◽  
Power Plants ◽  
Surface Region ◽  
Selective Dissolution ◽  
Boundary Region ◽  
Near Surface ◽  
Inconel 600 ◽  
Steam Generator Tubing

The degradation of steam generator tubing at nuclear power plants has become an important problem for the electric utilities generating nuclear power. The material used for the tubing, Inconel 600, has been found to be succeptible to intergranular attack (IGA). IGA is the selective dissolution of material along its grain boundaries. The author believes that the sensitivity of Inconel 600 to IGA can be minimized by homogenizing the near-surface region using ion implantation. The collisions between the implanted ions and the atoms in the grain boundary region would displace the atoms and thus effectively smear the grain boundary.To determine the validity of this hypothesis, an Inconel 600 sample was implanted with 100kV N2+ ions to a dose of 1x1016 ions/cm2 and electrolytically etched in a 5% Nital solution at 5V for 20 seconds. The etched sample was then examined using a JEOL JSM25S scanning electron microscope.

Geological and contaminant transport assessment of a low level radioactive waste disposal site

2019 ◽  
Vol 197 ◽  
pp. 174-183 ◽  
Author(s):  
Abdel-Aal M. Abdel-Karim ◽  
Ahmed A. Zaki ◽  
Waheed Elwan ◽  
Mohamed R. El-Naggar ◽  
Mahmoud M. Gouda
Keyword(s):  
Radioactive Waste ◽  
Contaminant Transport ◽  
Waste Disposal ◽  
Radioactive Waste Disposal ◽  
Disposal Site ◽  
Waste Disposal Site ◽  
Low Level ◽  
Low Level Radioactive Waste

The effect of subsurface military detonations on vadose zone hydraulic conductivity, contaminant transport and aquifer recharge

2013 ◽  
Vol 146 ◽  
pp. 8-15 ◽  
Author(s):  
Jeffrey Lewis ◽  
Jan Burman ◽  
Christina Edlund ◽  
Louise Simonsson ◽  
Rune Berglind ◽  
...  
Keyword(s):  
Hydraulic Conductivity ◽  
Contaminant Transport ◽  
Vadose Zone ◽  
Aquifer Recharge

ISO Standardization of the Scaling Factor Method for Low- and Intermediate Level Radioactive Wastes Generated at Nuclear Power Plants

2007 ◽  
Author(s):  
Makoto Kashiwagi ◽  
Hideki Masui ◽  
Yasutaka Denda ◽  
David James ◽  
Bertrand Lante`s ◽  
...  
Keyword(s):  
Nuclear Power ◽  
Power Plants ◽  
Nuclear Power Plants ◽  
Scaling Factor ◽  
Project Team ◽  
Radioactive Wastes ◽  
Intermediate Level ◽  
International Standard ◽  
Factor Method ◽  
International Standardization

Low- and intermediate-level radioactive wastes (L-ILW) generated at nuclear power plants are disposed of in various countries. In the disposal of such wastes, it is required that the radioactivity concentrations of waste packages should be declared with respect to difficult-to-measure nuclides (DTM nuclides), such as C-14, Ni-63 and α-emitting nuclides, which are often limited to maximum values in disposal licenses, safety cases and/or regulations for maximum radioactive concentrations. To fulfill this requirement, the Scaling Factor method (SF method) has been applied in various countries as a principal method for determining the concentrations of DTM nuclides. In the SF method, the concentrations of DTM nuclides are determined by multiplying the concentrations of certain key nuclides by SF values (the determined ratios of radioactive concentration between DTM nuclides and those key nuclides). The SF values used as conversion factors are determined from the correlation between DTM nuclides and key nuclides such as Co-60. The concentrations of key nuclides are determined by γ ray measurements which can be made comparatively easily from outside the waste package. The SF values are calculated based on the data obtained from the radiochemical analysis of waste samples. The use of SFs, which are empirically based on analytical data, has become established as a widely recognized “de facto standard”. A number of countries have independently collected nuclide data by analysis over many years and each has developed its own SF method, but all the SF methods that have been adopted are similar. The project team for standardization had been organized for establishing this SF method as a “de jure standard” in the international standardization system of the International Organization for Standardization (ISO). The project team for standardization has advanced the standardization through technical studies, based upon each country’s study results and analysis data. The conclusions reached by the project team was published as ISO International Standard 21238:2007 “The Scaling Factor method to determine the radioactivity of low- and intermediate-level radioactive waste packages generated at nuclear power plants” [1]. This paper gives an introduction to the international standardization process for the SF method and the contents of the recently published International Standard.

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