Gas Generation and Migration from Radioactive Waste Repositories

1994 ◽  
Vol 353 ◽  
Author(s):  
P. J. Agg ◽  
P. J. Nash ◽  
W. R. Rodwell ◽  
T. R. Lineham
Keyword(s):  
Research Programme ◽  
Theoretical Models ◽  
Theoretical Modelling ◽  
Gas Generation ◽  
Model Predictions ◽  
Anaerobic Corrosion ◽  
Radioactive Waste Repositories ◽  
And Migration ◽  
Waste Repositories ◽  
Assessment Research

AbstractDuring the post-closure phase of a repository for low- and intermediate-level radioactive wastes significant quantities of gas will be generated, primarily by the anaerobic corrosion of metals and the degradation of organic wastes. A description is given of recent work carried out within the Nirex Safety Assessment Research Programme to address the generation of gas within a repository and the migration of gas from the repository to the biosphere. Theoretical modelling capabilities have been developed to address both of these issues. In order to gain confidence in such theoretical models, it is important to validate model predictions against observed experimental data. Preliminary experiments carried out to help validate the modelling approaches are described.

An Assessment of the Long-Term Durability of Concrete in Radioactive Waste Repositories

1985 ◽  
Vol 50 ◽  
Author(s):  
A. Atkinson ◽  
D. J. Goult ◽  
J. A. Hearne
Keyword(s):  
Reinforced Concrete ◽  
Radioactive Waste ◽  
Concrete Slab ◽  
Laboratory Studies ◽  
Preliminary Assessment ◽  
Reinforced Concrete Slab ◽  
Radioactive Waste Repositories ◽  
Waste Repositories ◽  
Durability Of Concrete

AbstractA preliminary assessment of the long-term durability of concrete in a repository sited in clay is presented. The assessment is based on recorded experience of concrete structures and both field and laboratory studies. It is also supported by results of the examination of a concrete sample which had been buried in clay for 43 years.The enoineering lifetime of a 1 m thick reinforced concrete slab, with one face in contact with clay, and the way in which pH in the repository as a whole is likely to vary with time have both been estimated from available data. The estimates indicate that engineering lifetimes of about 103 years are expected (providing that sulphate resisting cement is used) and that pH is likely to remain above 10.5 for about 106 years.

Sorption Mechanism of Carbon-14 by Hardened Cement Paste

1995 ◽  
Vol 412 ◽  
Author(s):  
K. Noshita ◽  
T. Nishi ◽  
M. Matsuda ◽  
T. Izumida
Keyword(s):  
Electrostatic Force ◽  
Cementitious Materials ◽  
Hardened Cement ◽  
Sorption Mechanism ◽  
Carbon 14 ◽  
Adsorption Sites ◽  
Radioactive Waste Repositories ◽  
Waste Repositories ◽  
Positively Charged

AbstractCarbon-14 sorption by cementitious materials should be enhanced to ensure the long term safety of radioactive waste repositories. The sorption mechanism of inorganic C- 14 (CO32- was investigated using batch sorption experiments and zeta potential measurements. The results suggested that C-14 was adsorbed onto the cement surface by an electrostatic force, due to the reaction between SiO2 and CaO contained in the cementitious composition. That is, SiO2 was originally negatively charged (SiO-) in cement, but became positively charged through the interaction of Ca2+. These positive sites on the SiO2 surface adsorbed inorganic C-14. Ordinary Portland cement (OPC) did not contain enough SiO2 compared with its CaO content to produce sufficient numbers of C-14 adsorption sites. The C-14 distribution coefficient (Kd) was increased from 2,000 to 7,000 mL/g by adding SiO2 to OPC.

Characterisation of concrete, mortar and calcium silicate hydrated phases (CSH) and thorium retention analyses by ion beam techniques.

2012 ◽  
Vol 1475 ◽  
Author(s):  
Ursula Alonso ◽  
Tiziana Missana ◽  
Miguel Garcia-Gutierrez ◽  
Henar Rojo ◽  
Alessandro Patelli ◽  
...  
Keyword(s):  
Calcium Silicate ◽  
Cement Hydration ◽  
Ion Beam ◽  
X Ray ◽  
Tetravalent Actinide ◽  
Radioactive Waste Repositories ◽  
Edx Analyses ◽  
Waste Repositories ◽  
Beam Technique

ABSTRACTCement-based materials, like concrete and mortar, are widely used in radioactive waste repositories. A deep characterization of these heterogeneous materials, and of their main phases, is necessary to evaluate their capability of retaining critical radionuclides (RN).In this study, the ion beam technique micro- Particle Induced X- Ray Emission (μPIXE) is used to characterize the concrete and mortar used in the Spanish low level waste repository. Two calcium silicate hydrate (CSH) phases with different Ca/Si ratio are also studied, because they are known to be amongst the most relevant phases, formed upon cement hydration, that retain RN. The retention of thorium on the above mention materials, as relevant tetravalent actinide, is also analyzed. Results are compared with Scanning Electron Microscopy- Energy Dispersive X-Ray Spectroscopy (SEM-EDX) analyses.

scholarly journals Integrated approach to risk assessment of potential surface radioactive waste storage

2019 ◽  
Vol 95 (2) ◽  
pp. 133-139
Author(s):  
I. P. Korenkov ◽  
Tatyana N. Lashchenova ◽  
N. K. Shandala ◽  
V. V. Romanov
Keyword(s):  
Radioactive Waste ◽  
Potential Surface ◽  
Integrated Approach ◽  
Comprehensive Approach ◽  
Potential Danger ◽  
Management Decisions ◽  
Near Surface ◽  
Waste Storage ◽  
Radioactive Waste Repositories ◽  
Waste Repositories

Algorithm for management of decision-making on the decommissioning of nuclear and radiation hazardous objects (RHO) should be both based on an comprehensive approach, with taking into account all the potential dangers, and relied upon on the requirements of a modern regulatory framework, as well as economically sound and socially oriented. The aim of the work was a development of a comprehensive approach to the assessment of the degree of the potential danger of near surface radioactive waste repositories in RHO, on the base of which it is possible to make substantiated management decisions for their decommissioning. Tasks: To develop an array of radio-ecological approaches, including radiation-hygienic, hydrogeological and engineering criteria for the assessment of the potential danger of radioactive waste repositories. Results There are presented radiation hygienic, hydrogeological and engineering and technical criteria on the basis of which there are calculated coefficients of the relative hazard of storages. In dependence to the value of the coefficients there are suggested four categories of danger - a safe, low dangerous, dangerous and very dangerous. There are elaborated approaches on management decisions-making in various variants of decommissioning - the conversion, renovation, conservation and liquidation.

Construction and Experimental Study of an Elevation Linear Fresnel Reflector

2016 ◽  
Vol 138 (3) ◽  
Author(s):  
J. D. Nixon ◽  
P. A. Davies
Keyword(s):  
Heat Loss ◽  
Thermal Efficiency ◽  
Theoretical Models ◽  
Loss Coefficient ◽  
Heat Transfer Fluid ◽  
Stagnation Temperature ◽  
Model Predictions ◽  
The Difference ◽  
Predicted Values ◽  
Linear Fresnel Reflector

This paper outlines a novel elevation linear Fresnel reflector (ELFR) and presents and validates theoretical models defining its thermal performance. To validate the models, a series of experiments were carried out for receiver temperatures in the range of 30–100 °C to measure the heat loss coefficient, gain in heat transfer fluid (HTF) temperature, thermal efficiency, and stagnation temperature. The heat loss coefficient was underestimated due to the model exclusion of collector end heat losses. The measured HTF temperature gains were found to have a good correlation to the model predictions—less than a 5% difference. In comparison to model predictions for the thermal efficiency and stagnation temperature, measured values had a difference of −39% to +31% and 22–38%, respectively. The difference between the measured and predicted values was attributed to the low-temperature region for the experiments. It was concluded that the theoretical models are suitable for examining linear Fresnel reflector (LFR) systems and can be adopted by other researchers.

Gene Differentiation in Pacific Salmon (Oncorhynchus sp.): Facts and Models with Reference to Pink Salmon (O. gorbuscha)

1994 ◽  
Vol 51 (S1) ◽  
pp. 223-232 ◽  
Author(s):  
Lev A. Zhivotovsky ◽  
A. J. Gharrett ◽  
A. J. McGregor ◽  
M. K. Glubokovsky ◽  
Marcus W. Feldman
Keyword(s):  
Pacific Salmon ◽  
Gene Diversity ◽  
Genetic Relationships ◽  
Pink Salmon ◽  
Theoretical Models ◽  
Genetic Distances ◽  
Gene Drift ◽  
Gene Differentiation ◽  
Or Gene ◽  
And Migration

Analyzing population genetic data usually involves examining relationships among populations followed by analysis of the distribution of genetic variability. Genetic relationships are often depicted with multidimensional scaling or trees constructed from genetic distances; genetic variation within and among populations is partitioned using gene diversity measures such as FST or GST. Genetic distances or gene diversity are often used to estimate influences of gene drift, migration, and/or selection on observed gene differentiation. We used allozyme data for pink salmon populations to examine the theoretical models available for estimating magnitudes of these factors in Pacific salmon populations. The models included (1) mutation and gene drift; (2) mutation and migration; (3) migration and gene drift; and (4) gene drift, migration, and selection. These models suggest that gene drift and migration are probably important at the lowest levels of population hierarchy, but even very small forces such as weak heterogeneous selection and low migration levels may be important at higher levels. The accuracy of some estimates should be questioned because for many situations appropriate models are either not yet available or are not sufficiently refined. Also, the dynamic genetic structure of salmon populations makes it unlikely that the steady state assumed for many theoretical models has obtained.

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