Radon Measurements at Australian Antarctic Stations Brendan Tate Australian Radiation Protection and Nuclear Safety Agency
Why Measure Radon in Antarctica? Indoor radon Request from AAD to find out radon levels at stations Two categories of radon exposures Dwellings (public) Workplaces (occupational) Antarctic stations cover both categories, sometimes in the same building! AAD Station Staff live on site, 24-7 occupation, from 2 to 18 months Any locations above RPS 1 recommended action levels? 200 Bq/m 3 for dwellings 1000 Bq/m 3 for workplaces How much does radon vary between winter and summer seasons? 2
History of Antarctic Radon Radon measured in Antarctica since 1950 s US station Little America V, International Geophysical Year, 1957-58 ( 100 mbq/m 3 ) Long-range atmospheric transport from continental areas Rn measurements mostly used as a tracer for other environmental processes Outdoor radon levels orders of magnitude lower than that found elsewhere in the world Very few indoor measurements attempted E.g. Ukrainian research station Academician Vernadsky 2004 (annual indoor average 18 Bq/m 3 ) 3
Australian Antarctic Stations Three permanent Mainland stations Casey, Davis, Mawson Refurbished, New buildings 1980 s Steel frames, steel exteriors Extensive weather sealing and cold porches One permanent Sub-Antarctic station Macquarie Island Mix of old and new buildings Wooden frames and exteriors Weather sealing not as complete as mainland All four stations built on rock, which can be exposed during summer months Diagram courtesy of Australian Antarctic Division www.antarctica.gov.au 4
Macquarie Island Exterior Construction Interior Construction 5
Mainland Stations Exterior Construction Davis Casey Photos courtesy of Australian Antarctic Division www.antarctica.gov.au 6
Passive Radon Monitors NRPB-style radon monitor housing, single use only Fitted with ARPANSA Pershore CR-39 Plaque (35mm x 20mm and 0.5mm thick) Counted using in-house SANTECs system 52 Annual or Winter monitors, 13 at each station In place for approx. one year Minimum 300 days, maximum 400 days 24 Summer monitors, 6 at each station In place from 1 to 2 months Minimum 28 days, maximum 56 days Measured combinations of living, working and common (recreational) areas 7
Monitor Deployment 1 Winter Placement Included guiding notes, allowed station staff to choose appropriate monitor locations No of Buildings Building Storey Area Type Downstairs Upstairs Living Common Work Mawson 4 10 3 4 3 6 Davis 1* 9 4 1 10 2 Casey 3 10 3 1 8 4 Macq Is. 10 11 2 3 2 8 Total 18 40 12 9 23 20 Percentage 77% 23% 17% 44% 39% Note: *Davis: living quarters consist of 3 interlinked structures 8
Monitor Deployment 2 Summer Placement Monitors to be placed alongside 6 existing winter monitors No of Buildings Building Storey Area Type Downstairs Upstairs Living Common Work Mawson 2 4 2 2 1 3 Davis 1* 6 0 1 4 1 Casey 1 4 2 2 # 1 1 Macq Is. 4 6 0 2 3 3 Total 8 20 4 7 9 8 Percentage 83% 17% 29% 38% 33% Notes: *Davis: living quarters consist of 3 interlinked structures # Casey: one new location with no winter analogue 9
Typical Indoor Locations Davis Casey 10
Monitor Placement Issues Davis 1 building (3 modules) 13 monitors per building Mix of living, working & common areas Poor representation of entire station Good representation of single high-use building Casey Multiple monitors in large open areas A summer placement in new location Macquarie Is. 10 buildings No more than 2 monitors per building Mix of living, working & common areas Good representation of entire station Preferred Situation Overall Several missing monitors after winter redundant monitors 11
Interesting Observations Highest winter Measurement at Mawson 30 Bq/m 3 : Crawlspace beneath Red Shed Highest winter measurement at Davis 41 Bq/m 3 : Partially underground room Lowest Maximum winter measurement at Casey 21 Bq/m 3 : Plant Inspector s workshop Highest winter value at Macquarie Island 24 Bq/m 3 : Green Store, area not usually heated Lowest overall average winter and summer measurements at Macquarie Island 14 Bq/m 3 and 23 Bq/m 3 respectively No accurate measurements above action limits imposed by RPS 1 Summer/Winter decrease at 2 locations an office and living quarters used extensively over summer but rarely during winter 17
Alternative Active Measurement Radon concentrations are high enough in summer to justify active monitoring Use portable continuous monitor (e.g. SARAD, AlphaGUARD) 24-48 hours at each location (with 1 hour integration) Could be done over 1 week during resupply Possible to measure 5-6 individual locations Would also give an indication of diurnal variation http://www.sarad.de/ Much lower uncertainty than passive monitors with 30-day exposures (±15% compared to ±50%!) http://www.saphymo.com/ 18
Summary Radon levels at all four stations low No concerns for Australian Staff Mainland Winter averages over range 14-20 Bq/m 3 (c.f. 18 Bq/m 3 Academician Vernadsky, 2004) Mainland Summer averages over range 50-60 Bq/m 3 3-3.6x increase Macquarie Is. averages 14 Bq/m 3 (winter) and 23 Bq/m 3 (summer) 1.6x increase Winter uncertainty approx ±20% Summer uncertainty approx ±50% 2 month placement is too short for this style of monitor 3 months (or 100 days) minimum is required Active Measurement would be useful alternative in summer season Reconsider monitor placement Redundant monitors 19
Acknowledgements Australian Antarctic Division: Sue Hillam for assistance with logistics Station Doctors for 2012-2013 seasons for handling and on-site deployment of monitors ARPANSA: Paul Martin for initiating project and guidance Stephen Marks for site descriptions and photos at Casey and Davis PRMS staff for assistance with monitor construction, and handling and etching of monitors on return 20
THANK YOU CONTACT ARPANSA Email: brendan.tate@arpansa.gov.au Website: www.arpansa.gov.au Telephone: +61 3 9433 2257 Freecall 1800 022 333 General Fax: +61 3 9432 1835