Development of Reference Materials and Evaluation of Decay Data in Support of Characterisation of Naturally Occurring Radioactive Material
Creators: name: BRAYSHER, EMMA
Publisher: name: University of Surrey
Year: 2021

description: "A number of industries generate by-products containing naturally occurring radioactive material (NORM). Such materials must be characterised prior to re-use, for example, in building materials or for sentencing as waste. In the UK, industries producing NORM are subject to the Environmental Permitting Regulations 2018 (EPR 2018). As a result, such industries have a duty to accurately characterise the radioactivity content of NORM to determine if they are within regulation. The work in this thesis supports this in a variety of ways.
description: Firstly, this work supports accurate radionuclide measurement by increasing the number of reference materials available for NORM industries, by processing and characterising blast furnace slag for the steel industry and pipeline scale for the oil and gas industry. A global comparison exercise was undertaken for the characterisation of the blast furnace slag, resulting in two peer-reviewed publications, and plans have been put in place for an International comparison exercise of the pipeline scale led by NPL along with other National Measurement Institutes. Reference materials are a key requirement for validating radioanalytical methods for accurate measurement and to demonstrate compliance, and the variety of matrices and principal radionuclides encountered in NORM mean that having industry-specific reference standards is vital.
description: Secondly, a method for total dissolution of solid samples by lithium borate fusion has been improved by increasing the sample size that can be processed. This allows for various complex sample matrices, such as those encountered in nuclear decommissioning or NORM, to be entirely dissolved. Dissolution of increased sample sizes provides confidence that quantitative recovery of low activity levels from complex matrices is routinely achievable. This work, the outcomes of which have been peer-reviewed and published, supports the accurate characterisation of the significant NORM and nuclear decommissioning activities now and in the future, as well as in the development of reference materials that provide the underpinning metrology to such programmes.
description: Thirdly, the measurement of decay data which underpins all radioactive analysis has been reviewed and enhanced. A method has been developed for atom counting of long-lived radionuclides using tandem inductively coupled plasma mass spectrometry for the first time. In some cases, decay data are outdated and/or significant uncertainties remain. Half-life measurements of long-lived naturally occurring radionuclides in need of updating have been identified and measurement techniques compared, a summary of which has been peer-reviewed and published. The novel application of tandem inductively coupled plasma mass spectrometry in this field, which can be combined with primary counting to give a half-life measurement, has been investigated in this work. Initially applied to 238U and combined with defined solid angle counting measurement, this method is applicable to a range of long-lived radionuclides such as 151Sm, 93Zr, 237Np and 129I with the benefit of online separation.
description: In summary, this work has contributed to the field of radiochemistry by improving the accuracy of measurements of naturally occurring radionuclides. This can be applied to characterisation of naturally occurring radioactive materials and environmental monitoring and can also be extended to nuclear decommissioning."