A recent publication by authors from the University of Manchester, University of Leeds, British Geological Survey, Quintessa, NSG and Radioactive Waste Management (RWM) has shown for the first time that the mobility of potentially harmful contaminants in crystalline rocks over long periods of time may be severely limited due to the presence of tiny crystals, meaning contaminant movement is likely to be focused to water-bearing fractures only.
The study, published in the Nature journal Scientific Reports, analysed crystalline (granite) rock samples from underground systems in Japan and the UK and the results imply that in many cases the importance of ‘rock matrix diffusion’ may be minimal. These findings, which apply to long-lived systems, build on previous laboratory and field studies over short periods of time which also suggested that contaminant mobility in crystalline rocks will be limited to short distances in parts of the rock that are away from large fractures.
Dr Gráinne Carpenter, NSG’s Head of Consultancy Services and co-author of the paper, commented:
The findings of our research challenge commonly proposed models regarding the length scale and importance of rock matrix diffusion. For the nuclear industry, our findings help to develop understanding of the processes which may be drawn upon to underpin safety cases for geological disposal.