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Dear all, We are having some hiccups preparing some naturally occurring radioactive samples in our thin section lab, such as monazite-bearing carbonatites and some alkaline granite samples (dose rate of 0.6--5 uSv/hr). I was wondering if any members of the community could impart some advice? Firstly, when assessing samples for radioactivity, what 'cut-off' levels do you have in your labs, and how are they calculated? We work from the UK HSE 1999 guidelines where no member of the public can obtain 1 mSv of radiation, above their normal background dose, over the course of a year. To assess the potential impact of an individual sample, we therefore measure the dose-rate in uSv/hr and multiply this by 1650 hours. From this we obtain the equivalent dose if the sample was worked with every working day in a year. If this value is above 1 mSv, currently, we do not proceed with any sample preparation (thin sectioning, crushing, etc.). This cut-off works out at around 0.65 uSv/hr for any sample. This cut-off has the advantage that a user of the thin-section lab will never receive >1 mSv in a year. However, it has the downside that many samples simply cannot be prepared in-house. Any advice on how you assess the radioactivity of samples, and the levels above which these samples cannot be worked on, would be helpful. Secondly, if you do prepare radioactive samples, what control measures do you put in place? For example, do you have completely separate equipment and dust filters for naturally-occurring radioactive samples? Do you apply a varying range of control measures depending on the activity of the sample? Any advice here would be very welcome. Lastly, do any of you know any thin-section labs which will prepare material in the range of 0.6-5 uSv/hr? Many Thanks, Sam Broom-Fendley _________________________________________ Dr. Sam Broom-Fendley, Research fellow in geology, University of Exeter, Camborne School of Mines. Room 3129, University of Exeter, Penryn Campus, Cornwall, TR10 9FE https://emps.exeter.ac.uk/csm/staff/slb241 http://www.bgs.ac.uk/sosRare/home.html Twitter: @SoSRare ------------------------------------------------------------------------------- Geo-mineralisation is administered by the Mineral Deposits Studies Group (UK) (www.mdsg.or.uk)