b'FeatureAirborne radiometrics over Maralinga - call for a new survey Table 1.Details of airborne radiometric surveys over Maralinga.Date, surveyor,Aircraft SpeedLineSensorController Na I CrystalEnergyChannels and reference (m/s) spacing (m) height (m) Sensor (l) layout range (keV) recorded1987, EG&G/EM,Wessex HC Mk2 30 50 30 REDAR IV 26 40x 0.65 l 38- 3026 256 Tipton et al. 1988 Helicopter1992, AGSO, MintyTwin Otter 80 1500 150 AGSO33 8x 4.13 l 300-3000 256et al. 1994 Own Design (every 100 s)1992, WGC Cessna 206 50 50 40 Geometrics33 8x 4.13 l 300-3000 256GR8002005, Fugro,Aero Commander70 400 80 Exploranium33 8x 4.13 l 0-3000 512Fugro2005 500S GR8202018, ThomsonCessna 210 70 200 60 Radiation33 8x 4.13 l 0-3000 512Aviation, ThomsonSolutions Aviation 2020 RSX-4Table 2.Half- lives of isotopesTable 3.Maximum activity concentrations in kBq/m2 of elementsobservedatMaralinga. present atthe time of each survey. Thosedetected areIsotope Symbol Half-life highlighted in red.Potassium 40 K-40 1.25 billion years Change in activity concentrations in kbq/m2 of elements over time at MaralingaUranium 238 U-238 4.5 billion years Isotope Half-life 1987 1992 1992 2005 2018Uranium 235U-235 708 million years EG&G AGSO,WGC FUGRO THOMSONThorium 232 Th-232 14 billion yearsObservedCalculated Calculated Calculated CalculatedPlutonium 239 Pu-239 24,100 years x 1.33Plutonium 241 Pu-241 14 years Cs-137 30.1718.6 16.6 16.6 12.3 9.1Americium 241 Am-241 432 years yearsCobalt 60 Co-60 5.27 years Co-60 5.27465 241 241 44 7.9yearsEuropium 152 Eu-152 13.5 yearsAm-241 432133 138 138 149 159Caesium 137 Cs-137 30.17 years yearsData examples By way of comparison with the reprocessed Thomson data, the caesium 137 data extracted from a survey \x1cown by World In 2018 Thomson Aviation \x1cew a survey area for GeoscienceGeoscience Corporation in 1992 over the area of the test range Australia (Figure 1) that included the Maralinga Test site. Theare presented. The fallout patterns illustrate the wind direction co-ordinates of this survey, part of the Gawler Craton survey, areat the time of each test and the northeast, southwest direction listed in Table 4. of the sand dunes (Figure 3).When this (Thomson) data was reprocessed for caesium 137,The ground zero sites and other information of the various tests plumes of this isotope could be seen streaming away from theare presented in Table 5.test site (Figure 2).Table 4.Coordinates of Thomson Aviation survey overMaralinga (area R1B) in 2018 (ThomsonAviation 2020).Longitude Latitude131.5 -29.5133.5 -29.5133.5 -30.5131.0 -30.5131.0 -29.65131.5 -29.65Figure 1. The R1B area \x1fown by Thomson Aviation over Maralinga in 2018.48 PREVIEWAPRIL 2024'