• journal_title：Mineralogical Magazine
• Contributor：G. M. N. Baston ; T. A. Marshall ; R. L. Otlet ; A. J. Walker ; I. D. Mather ; S. J. Williams
• Publisher：Mineralogical Society of Great Britain and Ireland
• Date：2012-12-01
• Format：text/html
• Language：en
• Identifier：10.1180/minmag.2012.076.8.42
• journal_abbrev：Mineralogical Magazine
• issn：0026-461X
• volume：76
• issue：8
• firstpage：3293
• section：Gas

The release and migration of gaseous carbon-14 has been identified as a key issue for geological disposal of intermediate-level radioactive wastes in the UK. A significant fraction of carbon-14 in the UK inventory is in irradiated graphite. This paper describes measurements of gaseous carbon-14 releases from irradiated graphite on immersion in alkaline solution. Apparatus has been developed to discriminate organic and inorganic (¹⁴CO/¹⁴CO₂) species in the gas phase by means of selective oxidation and capture. In the initial experiment, small amounts of gaseous carbon-14 (~4 Bq) were released from 9 g of crushed graphite within a two-week period. In a long-term experiment, cumulative releases were measured periodically from an intact specimen of graphite over a 14 month period. A small fraction of the graphite carbon-14 inventory was released to the gas phase (~0.004% as CO/CO₂ and ~0.001% associated with organic compounds). A larger quantity of carbon-14, about 0.1%, was released to the solution phase and was thought to be mainly ¹⁴CO₂, with some possible organic component. In general, the rate of gaseous carbon-14 release decreased with time. The results suggest a small initial release of relatively labile, accessible carbon-14, with longer term release occurring at a much slower rate. Tritium (T) releases were also measured.