Open AccessExamination of Surface Deposits on Oldbury Reactor Core Graphite to Determine the Concentration and Distribution of 14C
Author(s) -
Liam Payne,
Peter J Heard,
Thomas Bligh Scott
Publication year - 2016
Publication title -
plos one
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.99
H-Index - 332
ISSN - 1932-6203
DOI - 10.1371/journal.pone.0164159
Subject(s) - graphite , fraction (chemistry) , rod , materials science , radiochemistry , irradiation , nuclear graphite , pellet , analytical chemistry (journal) , chemistry , mineralogy , metallurgy , environmental chemistry , chromatography , composite material , medicine , alternative medicine , physics , pathology , nuclear physics
Pile Grade A graphite was used as a moderator and reflector material in the first generation of UK Magnox nuclear power reactors. As all of these reactors are now shut down there is a need to examine the concentration and distribution of long lived radioisotopes, such as 14 C, to aid in understanding their behaviour in a geological disposal facility. A selection of irradiated graphite samples from Oldbury reactor one were examined where it was observed that Raman spectroscopy can distinguish between underlying graphite and a surface deposit found on exposed channel wall surfaces. The concentration of 14 C in this deposit was examined by sequentially oxidising the graphite samples in air at low temperatures (450°C and 600°C) to remove the deposit and then the underlying graphite. The gases produced were captured in a series of bubbler solutions that were analysed using liquid scintillation counting. It was observed that the surface deposit was relatively enriched with 14 C, with samples originating lower in the reactor exhibiting a higher concentration of 14 C. Oxidation at 600°C showed that the remaining graphite material consisted of two fractions of 14 C, a surface associated fraction and a graphite lattice associated fraction. The results presented correlate well with previous studies on irradiated graphite that suggest there are up to three fractions of 14 C; a readily releasable fraction (corresponding to that removed by oxidation at 450°C in this study), a slowly releasable fraction (removed early at 600°C in this study), and an unreleasable fraction (removed later at 600°C in this study).