Abstract
AbstractLarge quantities of irradiated graphite will arise from the decommissioning of the UK's Magnox power stations. Irradiated graphite contains 14C as well as other longer lived radionuclides (e.g. 36Cl). The potential use of magnetic sector secondary ion mass spectrometry (MS-SIMS) to examine the distribution of the 14C within trepanned graphite samples from a Magnox nuclear power station has been investigated. This work indicates that the methodology proposed has the potential to be used to analyse irradiated graphite samples with preliminary results highlighting a possible 14C enrichment in the carbonaceous deposit found on a channel wall sample. 14C concentrations in samples without this deposit were below the limits of detection of the instrument. The methodology used for these determinations ensured that possible mass interferences between 14C species and oxygen-bearing or nitrogen-bearing species were eliminated from the analysis. Future work will utilize the methodology proposed in this work on a larger number of samples.
Highlights
THE decommissioning of the first generation of gascooled, graphite-moderated reactors in the United Kingdom will lead to approximately 45,000 m3 of irradiated graphite waste requiring disposal (NDA, 2013)
The majority of this will be classified as intermediate level waste (ILW) (NDA, 2014) due to its content of the long-lived radionuclide 14C, which is a significant radionuclide for consideration in the safety case for a geological disposal facility (GDF) in the UK (NDA, 2012)
This work investigates whether the use of magnetic sector secondary ion mass spectrometry (MS-SIMS) is suitable to determine the distribution of 14C in irradiated graphite samples trepanned from one of the reactor cores at Oldbury Magnox power station (Gloucestershire, UK) in 2004, after 37 years of operation
Summary
THE decommissioning of the first generation of gascooled, graphite-moderated reactors in the United Kingdom will lead to approximately 45,000 m3 of irradiated graphite waste requiring disposal (NDA, 2013). The majority of this will be classified as intermediate level waste (ILW) (NDA, 2014) due to its content of the long-lived radionuclide 14C, which is a significant radionuclide for consideration in the safety case for a geological disposal facility (GDF) in the UK (NDA, 2012). This work investigates whether the use of magnetic sector secondary ion mass spectrometry (MS-SIMS) is suitable to determine the distribution of 14C in irradiated graphite samples trepanned from one of the reactor cores at Oldbury Magnox power station (Gloucestershire, UK) in 2004, after 37 years of operation. MS-SIMS inflicts minimal damage on the specimen in very small regions, and if this technique could be validated, it could be used to examine the distribution of 14C in irradiated graphite and aid the understanding of results achieved from future microbial leaching experiments
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