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The determination of pure beta-emitters and their behaviour in a salt-marsh environment

The determination of pure beta-emitters and their behaviour in a salt-marsh environment
The determination of pure beta-emitters and their behaviour in a salt-marsh environment
The thesis describes the development of analytical procedures for the isolation and
measurement of anthropogenic pure beta-emitting radioisotopes in low-level radioactive
wastes and environmental samples. The research focussed on three key pure beta-emitting
radioisotopes, namely 63Ni, 90Sr and 99Tc. Iron-55, which decays by electron capture, was also
investigated. Source preparation and measurement techniques based on liquid scintillation
counting were developed and optimised to permit the low-level measurement of all four
radioisotopes. In particular, a technique was developed for increasing the amount of stable Fe
that may be loaded into scintillant, reducing the limit of detection achievable for 55Fe
measurement and increasing the sensitivity of analysis for 55Fe in Fe-rich materials such as
sediments and steels.
Chemistries for the isolation of the four radioisotopes were studied and optimised. Solvent
extraction was chosen for the specificity offered by the technique. In most instances,
improvements in separation efficiency were achieved by adsorbing the extractant onto an
inert support producing an extraction chromatographic material. Key separation techniques
were then combined to produce a sequential separation scheme that permitted a more rapid
analysis of the four radioisotopes on a single sample. The sequential separation technique was
then optimised for the analysis of 55Fe, 63Ni, 90Sr and 99Tc in both low-level wastes and
environmental matrices (mainly sediments). Such separation schemes are crucial to the
efficient analysis of samples in limited time spans and are vital when the amount of sample
available is restricted.
The optimised methods were used to investigate levels of anthropogenic pure beta-emitters in
a saltmarsh sediment core collected from the Esk Estuary in Cumbria. Analysis of the four
beta emitting radioisotopes was complemented by the analysis of major elements, trace
elements and gamma emitting radioisotopes. This information was used to determine the
behaviour of the beta emitters following deposition within the saltmarsh environment.
Although all four beta emitters were detected in the core, only 90Sr and 99Tc were at
sufficiently high levels to permit a more thorough investigation. The combination of
geochemica! analysis and radiochemical analysis of this range of radioisotopes with widely
varying chemistries has allowed a range of possible pre- and post-depositional processes to be
investigated as well as providing data on the levels of previously unmeasured beta emitters in
the saltmarsh environment. Such information is essential in assessing the long-term retention
and potential re-release of these radioisotopes and their importance in radiological dose
assessment. The information also has wider implications to the behaviour of inorganic
pollutants in coastal waters.
Warwick, P.E.
f2675d83-eee2-40c5-b53d-fbe437f401ef
Warwick, P.E.
f2675d83-eee2-40c5-b53d-fbe437f401ef

Warwick, P.E. (1999) The determination of pure beta-emitters and their behaviour in a salt-marsh environment. University of Southampton, Faculty of Science, School of Ocean and Earth Science, Doctoral Thesis, 285pp.

Record type: Thesis (Doctoral)

Abstract

The thesis describes the development of analytical procedures for the isolation and
measurement of anthropogenic pure beta-emitting radioisotopes in low-level radioactive
wastes and environmental samples. The research focussed on three key pure beta-emitting
radioisotopes, namely 63Ni, 90Sr and 99Tc. Iron-55, which decays by electron capture, was also
investigated. Source preparation and measurement techniques based on liquid scintillation
counting were developed and optimised to permit the low-level measurement of all four
radioisotopes. In particular, a technique was developed for increasing the amount of stable Fe
that may be loaded into scintillant, reducing the limit of detection achievable for 55Fe
measurement and increasing the sensitivity of analysis for 55Fe in Fe-rich materials such as
sediments and steels.
Chemistries for the isolation of the four radioisotopes were studied and optimised. Solvent
extraction was chosen for the specificity offered by the technique. In most instances,
improvements in separation efficiency were achieved by adsorbing the extractant onto an
inert support producing an extraction chromatographic material. Key separation techniques
were then combined to produce a sequential separation scheme that permitted a more rapid
analysis of the four radioisotopes on a single sample. The sequential separation technique was
then optimised for the analysis of 55Fe, 63Ni, 90Sr and 99Tc in both low-level wastes and
environmental matrices (mainly sediments). Such separation schemes are crucial to the
efficient analysis of samples in limited time spans and are vital when the amount of sample
available is restricted.
The optimised methods were used to investigate levels of anthropogenic pure beta-emitters in
a saltmarsh sediment core collected from the Esk Estuary in Cumbria. Analysis of the four
beta emitting radioisotopes was complemented by the analysis of major elements, trace
elements and gamma emitting radioisotopes. This information was used to determine the
behaviour of the beta emitters following deposition within the saltmarsh environment.
Although all four beta emitters were detected in the core, only 90Sr and 99Tc were at
sufficiently high levels to permit a more thorough investigation. The combination of
geochemica! analysis and radiochemical analysis of this range of radioisotopes with widely
varying chemistries has allowed a range of possible pre- and post-depositional processes to be
investigated as well as providing data on the levels of previously unmeasured beta emitters in
the saltmarsh environment. Such information is essential in assessing the long-term retention
and potential re-release of these radioisotopes and their importance in radiological dose
assessment. The information also has wider implications to the behaviour of inorganic
pollutants in coastal waters.

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Published date: April 1999
Additional Information: Digitized via the E-THOS exercise.
Organisations: University of Southampton

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Local EPrints ID: 42175
URI: http://eprints.soton.ac.uk/id/eprint/42175
PURE UUID: 7b40917d-6936-4e34-8737-a5d53af65909

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Date deposited: 22 Nov 2006
Last modified: 13 Mar 2019 21:12

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