Category Archives: Advanced separation techniques for nuclear fuel reprocessing and radioactive waste treatment

Future trends

The problem of radiation pollution in the environment is expected to increase as industries in the world experience pressure to reduce their carbon atmospheric contributions. The dilemma is that production of goods will only increase with population growth. Most countries are considering nuclear energy as the interim solution to the growing energy crisis. This will require environmental engineers and scientists […]

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In situ bioaugmentation

This entails identifying indigenous species of bacteria within the vicinity of the contaminated site and determining the critical carbon sources and nutri­ents that could be supplied to encourage the growth of the target species. When the selected nutrients are introduced into the environment, either by injection into boreholes or by spreading on the ground, the target species will out-compete other […]

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Molecular bioaugmentation

The molecular bioaugmentation process utilizes genetic carriers such as transposons and plasmids to shuttle genetic information for toxic metal remediation into native species in the environment or species already adapted to the target environment. Several species of bacteria are capable of picking up and retaining circular fragments of DNA called Broad-Host — Range Plasmids which may be engineered to carry […]

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Biofractionation and bioseparation of elements

A very little understood application of bioseparation involves using micro­organisms to discriminate radioisotopes by size. So far, this application has remained conceptual due to limited understanding on the structure and function of organisms that are suspected to achieve biofractionation (Molokwane and Chirwa, 2009). In the latter study, Molokwane and Chirwa observed with a modest degree of certainty that microbial cells […]

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Simulation and parameter optimization

The system described above is an oversimplification of the actual biofilm processes in nature. However, the example serves to illustrate how complex the solution for such a simplified version could be. In the old days before fast and efficient computers, solving such problems manually was unthink­able. Lately, computer speed has increased exponentially and memory is no longer a limiting factor. […]

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Parameter optimization

The parameters in the biofilm model in the example above were estimated using a heuristic procedure — Genetic Search Algorithm (GSA). The first version of this algorithm was implemented in the C programming language using subroutines adopted from Hunter (1998). The GSA uses the inverse of the mean residual sum of squares (MRSS) computed as the global vari­ance (a2) as […]

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Application of biofilm process

The applications of mathematical models to complex biofilm process resembling natural systems are very rare. Most of the reports are based on laboratory-scale pure cultures. Black-box approaches are normally used to evaluate performance of actual systems. The above quoted example by Nkhalambayausi-Chirwa and Wang (2005) was one of the few efforts to mechanistically model a mixed culture system.

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Structure and strength of complexes

As has been noted above, actinide ions in their common solution oxidation states (3+ to 6+) are all hard Lewis acids, and their bonds with aqueous ligands are predominantly ionic. Several decades ago it was observed that for a given ligand, the strength of actinide complexes increased with the “effective” cationic electrostatic charge of the actinide ions (Rao, Choppin 1984):

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Spectroscopic demonstration using commercial fuel

Samples of commercial fuel were taken from a high-burnup ATM-109 fuel (Vaidyanathan 1997). The ATM-109 fuel consists of 6 rods that were also produced by General Electric (GE). The rods were initially irradiated in the Quad Cities I reactor beginning in February 1979 until September 1987 in a normal assembly amassing an average exposure of 43 MWd/kgU. The rods were […]

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