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Nick Beresford (CEH) & David Copplestone (Stirling Univ.)

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Presentation on theme: "Nick Beresford (CEH) & David Copplestone (Stirling Univ.)"— Presentation transcript:

1 Nick Beresford (CEH) & David Copplestone (Stirling Univ.)

2 Code which implements the USDOEs Graded approach (replaces BCG-calculator) Part of the RESRAD suite of models Freshwater and terrestrial ecosystems Database contains 46 radionuclides Four organisms – terrestrial animal, terrestrial plant, riparian animal and aquatic animal Can create organisms & simple foodchains

3 Available at no cost for download on-line Comparatively well documented Being maintained and upgraded Training available

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5 BDAC Series of paper in: Woodhead, D.S. (Ed.), Protection of the environment from ionising radiation. Journal of Environmental Radioactivity, 66.

6 Tiers are Levels CRs are Bivs EMCLs are BCGs (Biota Concentration Guides) DCCs are DCFs (Dose Conversion Factor)

7 RESRAD-BIOTA Level

8 Based on NCRP & IAEA set dose limits for protection of: Aquatic animals - 10 mGy d -1 Terrestrial plants - 10 mGy d -1 Terrestrial animals - 1 mGy d -1

9 Estimated assuming: Infinitely large (internal) and small (external) geometries for dose calculations Daughter T 1/2 s up to 100 y included All terrestrial organisms 100% in soil; aquatic 100% water-sediment interface Maximum CR values or 95th percentile CR values predicted using a kinetic- allometric approach

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11 Screening assessment - Levels 1 Cs-137 water 10 Bq/l sediment 1000 Bq/kg Am-241 sediment 1000 Bq/kg Cf-252 water 1 Bq/kg Use 10 µGy/h screening level (2.4E-4 Gy/d)

12 Run the freshwater and terrestrial scenarios from the ERICA Tier 1 practical Use ERICA screening value 10 µGy/h Leave out the radionuclides which are not included in RESRAD

13 RadionuclideFreshwater (Bq/l) H-34 Co Cs Pu RadionuclideSoil (Bq/kg) Cs Am Pu Co Sr-901.3

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15 Site specific CR values available for aquatic animal: Co 1500; Cs 9000; H 0.25; Pu 200 RadionuclideFreshwater (Bq/l) H-34 Co Cs Pu

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17 Also uses CRs (or Bivs), but:

18 Soil contamination Fugitive dust Vegetation Soil invertebrate Herbivorous mammals Herbivorous birds Carnivorous mammals Water contamination Root uptake Can use kinetic-allometric approach with simple foodchains for terrestrial/riparian vertebrates

19 Size effects rates of all biological structures and processes from cellular metabolism to population dynamics The dependence of a biological variable Y on a body mass M is typically characterised by an allometric scaling law of the form: Y = aM b where a and b are constants

20 b most often = quartile values: b most often = quartile values: metabolic rates scale as M 0.75 M 0.75 is often referred to as metabolic live-weight life-span scales as M 0.25 food, water and inhalation rates scale as M 0.75 All potential useful for radioecological models, but:

21 For (some) radionuclides both the biological half-life (often M 0.25 ) and transfer from diet (M ) have been found to scale allometrically RESRAD-BIOTA uses allometric relationships for radionuclide biological half- lives and a number of other animal parameters (e.g. food & water intake, life- span, inhalation rate) for terrestrial and riparian vertebrates

22 kg/d T1/2 =13.22*(mass )

23 kg/d T1/2 =13.22*(mass ) Ff=8.89*(mass ) Transfer coefficient F f ( d kg -1 ) = Equilibrium activity concentration in animal (Bq kg -1 FW) Daily intake of radionuclide (Bq d -1 )

24 kg/d T1/2 =13.22*(mass ) Ff=8.89*(mass ) DMI=0.0551*(mass 0.74 )

25 kg/d T1/2 =13.22*(mass ) Ff=8.89*(mass ) DMI=0.0551*(mass 0.74 )

26 kg/d T1/2 =13.22*(mass ) Ff=8.89*(mass ) DMI=0.0551*(mass 0.74 ) Bq/kg = Ff x DMI Transfer coefficient F f ( d kg -1 ) = Equilibrium activity concentration in animal (Bq kg -1 FW) Daily intake of radionuclide (Bq d -1 )

27 Create an organism and foodchain

28 RESRAD-BIOTA Level 3 Soil activity concentrations are available: Cs Bq/kg Pu Bq/kg Water concentration: Cs Bq/kg Pu-239 1E-3 Bq/kg Alpha RBE=10; Cut-off half-life=180 Dormouse characteristics: Size – 9x3x3 cm Weight - 30 g Occupancy – 50% in soil/50% on soil

29 RESRAD-BIOTA Level 3 Diet – 70 % seeds and 30 % invertebrates Concentration ratios for dormouse diet Seed Cs Pu-239 5E-3 Invertebrate Cs Pu


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