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This paper aims to consider numerical simulation for radionuclide transport calculations in geological radioactive waste repository.

The nonlinear two-point flux approximation is used to discretize the diffusion flux and has a fixed stencil. The cell-vertex unknowns are applied to define the auxiliary unknowns and can be interpolated by the cell-centered unknowns. The approximation of convection flux is based on the second-order upwind method with a slope limiter.

Numerical results illustrate that the positivity-preserving is satisfied in solving this convection-diffusion system and has a second-order convergence rate on the distorted meshes.

A new positivity-preserving nonlinear finite volume scheme is proposed to simulate the far-field model used in the geological radioactive waste repository. Numerical results illustrate that the positivity-preserving is satisfied in solving this convection-diffusion system and has a second-order convergence rate on the distorted meshes.

This research study aims to develop regular cylindrical pore network models (RCPNMs) to calculate topology and geometry properties of explosively created fractures along with their resulting hydraulic permeability. The focus of the investigation is to define a method that generates a valid geometric and topologic representation from a computational modelling point of view for explosion-generated fractures in rocks. In particular, extraction of geometries from experimentally validated Eulerian smoothed particle hydrodynamics (ESPH) approach, to avoid restrictions for image-based computational methods.

Three-dimensional stabilized ESPH solution is required to model explosively created fracture networks, and the accuracy of developed ESPH is qualitatively and quantitatively examined against experimental observations for both peak detonation pressures and crack density estimations. SPH simulation domain is segmented to void and solid spaces using a graphical user interface, and the void space of blasted rocks is represented by a regular lattice of spherical pores connected by cylindrical throats. Results produced by the RCPNMs are compared to three pore network extraction algorithms. Thereby, once the accuracy of RCPNMs is confirmed, the absolute permeability of fracture networks is calculated.

The results obtained with RCPNMs method were compared with three pore network extraction algorithms and computational fluid dynamics method, achieving a more computational efficiency regarding to CPU cost and a better geometry and topology relationship identification, in all the cases studied. Furthermore, a reliable topology data that does not have image-based pore network limitations, and the effect of topological disorder on the computed absolute permeability is minor. However, further research is necessary to improve the interpretation of real pore systems for explosively created fracture networks.

Although only laboratory cylindrical rock specimens were tested in the computational examples, the developed approaches are applicable for field scale and complex pore network grids with arbitrary shapes.

It is often desirable to develop an integrated computational method for hydraulic conductivity of explosively created fracture networks which segmentation of fracture networks is not restricted to X-ray images, particularly when topologic and geometric modellings are the crucial parts. This research study provides insight to the reliable computational methods and pore network extraction algorithm selection processes, as well as defining a practical framework for generating reliable topological and geometrical data in a Eulerian SPH setting.

The most significant sources and environmental pathways of manmade radionuclides have recently been examined by the RADPATH (Biochemical Pathways of Artificial Radionuclides) project, which was initiated under the auspices of the SCOPE (Scientific Committee on Problems of the Environment) unit. The accident at the Chernobyl nuclear power plant in 1986, with its associated radionuclide release, has provided an unexpected data source concerning movement of materials within various environmental compartments. Outlines some of the findings of the SCOPE‐RADPATH project, a particular focus of which was the Chernobyl accident, with reference to the atmospheric, terrestrial, aquatic and urban environments.

ARRANGEMENT OF REGULATIONS

Background: Geostatistics focuses on spatial or spatiotemporal datasets. Geostatistics was initially developed to generate probability distribution predictions of ore grade in the mining industry; however, it has been successfully applied in diverse scientific disciplines. This technique includes univariate, multivariate, and simulations. Kriging geostatistical methods, simple, ordinary, and universal Kriging, are not multivariate models in the usual statistical function. Notwithstanding, simple, ordinary, and universal kriging techniques utilize random function models that include unlimited random variables while modeling one attribute. The coKriging technique is a multivariate estimation method that simultaneously models two or more attributes defined with the same domains as coregionalization.

Objective: This study investigates the impact of populations on traffic volumes as a variable. The additional variable determines the strength or accuracy obtained when data integration is adopted. In addition, this is to help improve the estimation of annual average daily traffic (AADT).

Methods procedures, process: The investigation adopts the coKriging technique with AADT data from 2009 to 2016 from Montana, Minnesota, and Washington as primary attributes and population as a controlling factor (second variable). CK is implemented for this study after reviewing the literature and work completed by comparing it with other geostatistical methods.

Results, observations, and conclusions: The Investigation employed two variables. The data integration methods employed in CK yield more reliable models because their strength is drawn from multiple variables. The cross-validation results of the model types explored with the CK technique successfully evaluate the interpolation technique's performance and help select optimal models for each state. The results from Montana and Minnesota models accurately represent the states' traffic and population density. The Washington model had a few exceptions. However, the secondary attribute helped yield an accurate interpretation. Consequently, the impact of tourism, shopping, recreation centers, and possible transiting patterns throughout the state is worth exploring.

The transfer of radionuclides from fallout to individual foods has been studied continuously in several areas in the Republic of Croatia, since 1959. Investigations focus on the long‐lived fission radionuclides: ¹³⁷Cs and ⁹⁰Sr. In order to estimate doses received by the Croatian population the Caesium and Strontium levels in their diets were calculated and analysed. According to the results obtained the risk to the population from ¹³⁷Cs and ⁹⁰Sr ingestion was highest over the 1960s and in the year of the Chernobyl nuclear accident, but the content of radionuclides in the foods were below the permissible levels.

The recently established SCOPE‐RADTEST (Scientific Committee on Problems of the Environment‐Radioactivity from Nuclear Test Explosions) programme is examining releases of radioactivity due to nuclear detonations which have occurred at various test sites around the world, for peaceful and military purposes, taking into consideration both ecological and human effects. Presents the background to this programme, together with a summary of the proceedings of RADTEST’s North Atlantic Treaty Organization Advanced Research Workshop meetings held during 1994 in Vienna, Austria, and Barnaul, Russia, and of the 1995 meeting in Brussels/Liège, Belgium.

The purpose of this paper is to buildup baseline data for ²²⁶Ra, ²³²Th and ⁴⁰K levels in different food samples and computes their cancer risk (CR).

This report has been performed to buildup baseline data for ²²⁶Ra, ²³²Th and ⁴⁰K levels in different food samples and computes their CR. ²²⁶Ra, ²³²Th and ⁴⁰K activity levels were measured using ?-ray spectrometry based on high-purity germanium (HPGe).

The findings exhibited that the annual effective dose (AED) and CR due to ²²⁶Ra ingestion in foodstuff samples have shown the trends cereal > vegetable > meat > fruits > sesame. Meanwhile, (AED) and (CR) due to ⁴⁰K displayed the trends vegetable > cereal > meat > fruits > sesame. Although the average value of radiological dose due to ingestion of some radionuclides slightly exceed the values of some foodstuff around the world. However, the overall average of (AED) for all foodstuff samples (226.6 µSv/y) was found to be far below the world average (AED) (300 µSv/y).

The main contributor to the AED was ⁴⁰K 85, ²²⁶Ra 9 and ²³²Th 6%. The computed magnitude values for CR owing to ²²⁶Ra, ²³²Th, ⁴⁰K (1.3 × 10⁻⁵) lower than International Commission on Radiological Protection (ICRP) CR of (2.5 × 10⁻³) for the general public.

The main contributor to the AED was ⁴⁰K 85 %, ²²⁶Ra 9% and ²³²Th 6%. The computed magnitude values for CR owing to ²²⁶Ra, ²³²Th, ⁴⁰K (1.3 × 10⁻⁵) lower than ICRP CR of (2.5 × 10⁻³) for the general public.

Electrokinetics (EK) is an emerging remediation technology for the in situ removal of heavy metals, volatile organic compounds, and radionuclides from soils and sediments. Naval Air Weapons Station Point Mugu, California will host an EK technology demonstration. The demonstration will consist of installing and operating an EK system, which is engineered to remove cadmium and chromium from former electroplating waste lagoons. The selected site is adjacent to and encroaches on an environmentally sensitive salt marsh are for a federally protected wildlife. The electrokinetic process will be used to mobilize and extract heavy metals from the metals‐contaminated soil by applying a low amperage direct current across an array of electrodes placed in the contaminated soil. The demonstration will focus on the effectiveness of the EK process for removing heavy metals from the tidal marsh area. The EK demonstration will be used to collect cost‐effective data necessary to address both the technical and economic feasibility of using this technology in areas where soils are porous, water is brackish, and the system is susceptible to tidal influences.

This paper compares the gamma‐radioactivity values determined in an intertidal ecosystem on the Atlantic island of Barra in the Western Isles of Scotland in 1989 and 1994. Distinct differences in the accumulation values in different trophic levels were detected on each occasion, but, in the intervening five years between surveys, there have also been marked reductions in the gamma counts in many different organisms of each trophic level. Gamma‐radioactivity has continued to move through the sandy soils of the machair coastal dunes system, and hence away from the rooting zone of the vegetation. The decreasing gamma‐radioactivities noted point to a shoreline ecosystem that is recovering from the input of Chernobyl fallout.