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135 results on '"Livens, F. R."'

2. Improved localization of radioactivity with a normalized sinc transform

Author

Tsitsimpelis, Ioannis, Alton, Tilly, West, A., Taylor, James, Livens, F. R., Lennox, Barry, Joyce, Malcolm, Tsitsimpelis, Ioannis, Alton, Tilly, West, A., Taylor, James, Livens, F. R., Lennox, Barry, and Joyce, Malcolm

Abstract

A technique for the in-situ localization of radioactivity is described in which the influence of gamma-radiation impinging on a high-Z collimator, by which the angular response of a scintillation detector is constrained in order to identify the position of the radiation source, is expressed mathematically by way of a normalized sinc transform. We test this approach by examining the utility of the sinc transform to express the angular responses derived from a slot-collimated cerium bromide detector, across a variety of energy regions. Individual spectra have been acquired as a function of angle to explore how the shape of the response of the collimator-detector arrangement changes for X-rays and gamma rays. A 90% improvement in localization is observed when defined in terms of the area described by the variance between the known location and that indicated by the response of the collimated system. This approach has the potential to improve source location accuracy and to further optimize autonomous robot exploration routines used to characterize contaminated environments associated with nuclear legacies and radiological emergencies.

Published
2022

6. Synthesis and characterization of uranyl compounds with iminodiacetate and oxydiacetate displaying variable denticity

Author

Jiang, J., Sarsfield, M. J., Renshaw, J. C., Livens, F. R., Collison, D., Charnock, J. M., Helliwell, M., and Eccles, H.

Subjects
Chemistry, Inorganic -- Research, Acetates -- Physiological aspects, Oxygen -- Physiological aspects, Ligands -- Physiological aspects, Solid state chemistry -- Research, Chemistry
Abstract

Research has been conducted on the uranyl compounds with the dicarboxylate ligands oxydiacetate or iminodiacetate. The synthesis and characterization of these compounds have been carried out in a solid state and the results of the X-ray crystallographic analysis are presented.

Published
2002

18. Influence of riboflavin on the reduction of radionuclides by Shewanella oneidenis MR-1

Author

Cherkouk, A., Law, G. T. W., Rizoulis, A., Law, K., Renshaw, J. C., Morris, K., Livens, F. R., and Lloyd, J. R.

Subjects
food and beverages
Abstract

Uranium (as UO22+), technetium (as TcO4-) and neptunium (as NpO2+) are highly mobile radionuclides that can be reduced enzymatically by a range of anaerobic and facultatively anaerobic microorganisms, including Shewanella oneidensis MR-1, to poorly soluble analogues. The redox chemistry of Pu is more complicated, but the dominant oxidation state in most environments is poorly soluble Pu(IV), which can be reduced to the potentially more soluble Pu(III), which could enhance migration of Pu in the environment. Recently it was shown that flavins (riboflavin and flavin mononucleotide (FMN)) secreted by Shewanella oneidensis MR-1 can act as electron shuttles, promoting anoxic growth coupled to the accelerated reduction of poorly-crystalline Fe(III) oxides. Here we studied the role of riboflavin in mediating the reduction of radionuclides in cultures of Shewanella oneidensis MR-1. Our results demonstrate that the addition of 10 µM riboflavin enhances the reduction rate of Tc(VII) to Tc(IV) and Np(V) to Np(IV), but has no significant influence on the reduction rate of U(VI) by Shewanella oneidensis MR-1. The presence of riboflavin also accelerated Pu(IV) reduction, demonstrated by an increase in the percentage of Pu(IV) reduced to Pu(III), with and without riboflavin present (17 and 3%, respectively). Thus riboflavin can act as an extracellular electron shuttle to enhance rates of Tc(VII), Np(V) and Pu(IV) reduction, and may therefore play a role in controlling the oxidation state of key redox active actinides and fission products in natural and engineered environments. These results also suggest that the addition of riboflavin could be used to accelerate the bioremediation of radionuclide-contaminated environments.

Published
2016

20. The microbial ecology of land and water contaminated with radioactive waste; towards the development of bioremediation options for the nuclear industry

Author

Geissler, A., Selenska-Pobell, S., Morris, K., Livens, F. R., and Lloyd, J. R.

Abstract

The high financial and environmental costs associated with remediation of land contaminated through 60 years of global nuclear activity has underpinned the development of new passive in situ bioremediation processes for sites contaminated with nuclear waste. Many of these processes rely on successfully harnessing newly discovered natural biogeochemical cycles of key radionuclides and fission products. Of particular note are strategies that involve enzymatic and indirect redox transformations of actinides such as uranium, neptunium and plutonium and fission products such as technetium. This chapter will discuss the recent advances that have been made in understanding the microbial colonization of radioactive environments and the biological basis of microbial transformations of radioactive waste in these settings. In addition, the impact of co-contaminants such as nitrate on both the microbial ecology of sediments and radionuclide speciation will also be discussed.

Published
2010

38. Book reviews

Author

van Staden, J. F., primary, Taylor, R. B., additional, Davies, J. T., additional, Brereton, Richard, additional, Livens, F. R., additional, Davies, Cledwyn L., additional, Sneddon, Joseph, additional, and Blanchflower, John, additional

Published
1995
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49. ASSOCIATION OF PLUTONIUM WITH SOIL ORGANIC MATTER

Author

LIVENS, F. R., BAXTER, M. S., and ALLEN, S. E.

Abstract

A significant association of environmental plutonium with the organic components of U.K. soils has recently been demonstrated by sequential leaching experiments on samples influenced by discharges from both the Dounreay and Sellafield nuclear fuel reprocessing plants. This relationship has been further studied by alkali extraction, fractional precipitation, and dialysis to isolate both the humic and fulvic acid fractions of a Cumbrian soil. The 239,240Pu activities of these extracts were 31 and 7.7 Bq g-1, respectively, greater than the activity of the bulk soil (5.9 Bq g-1). Gel filtration on Sephadex gels G-50 and G-150 further showed that the humic acid extract is composed of relatively large molecules, with approximately 65 of the plutonium in the largest of these; fulvic acid is of lower molecular weight, and its plutonium content is distributed more evenly throughout the molecular weight spectrum. In both humic and fulvic acids, iron is concentrated in the largest molecular weight (>150 000) fractions.

Published
1987

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