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Screening tier comparisons

ERICA, RESRAD-BIOTA & EA R&D128

Follow-up actions from Vienna workshop

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Vienna scenario

• Comparison of the three openly available models – RESRAD-BIOTA, ERICA-Tool & EA R&D128

• River receiving mixed radionuclide discharges from multiple sources

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Results

• ERICA – highest dose rate (circa E3 µGy/h) predicted for insect larvae dominated by 234Th

• R&D128 – highest dose rate (circa E3 µGy/h) predicted for amphibian dominated by 239Pu

• RESRAD-BIOTA – 137Cs was the only nuclide to result in a risk quotient (RQ) in excess of 1 (for riparian animal)

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Parameter/output ERICA R&D128 RESRAD-BIOTA Radiation weighting factors α 10 20 20 Low-β 3 3 1 Kd values (l/kg) Cs 1.37x105 1x103 5x102 Pu 1.39x106 1x105 2x103 Th 1.84x107 1x104 6x104 Insect larvae (ERICA) cf Small Benthic Crustacean (R&D128) cf Geometry 2 (RESRAD-BIOTA)

Total dose rate (μGy/h) 3200 4.25 27.96 Cs Total dose rate (μGy/h) 116 1.32 6.83 Pu Total dose rate (μGy/h) 10.7 2.59 19.21 Th Total dose rate (μGy/h) 3070 0.32 1.90 CR Cs (Bq/kg:Bq/l) 10400 5230 22000 CR Pu (Bq/kg:Bq/l) 1100 137 1000 CR Th (Bq/kg:Bq/l) 100 100 80 Amphibian (ERICA and R&D128) cf Geometry 3 (RESRAD-BIOTA)

Total dose rate (μGy/h) 5.35 1898 27.58 Cs Total dose rate (μGy/h) 3.13 4.16 7.46 Pu Total dose rate (μGy/h) 2.20 1892 19.21 Th Total dose rate (μGy/h) 0.03 2.22 0.89 CR Cs (Bq/kg:Bq/l) 9300 11000 22000 CR Pu (Bq/kg:Bq/l) 230 100000 1000 CR Th (Bq/kg:Bq/l) 110 10000 80

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Parameter/output ERICA R&D128 RESRAD-BIOTA Radiation weighting factors α 10 20 20 Low-β 3 3 1 Kd values (l/kg) Cs 1x103 1x103 1x103 Pu 1x105 1x105 1x105 Th 1x104 1x104 1x104 Insect larvae (ERICA) cf Small Benthic Crustacean (R&D128) cf Geometry 2 (RESRAD-BIOTA)

Total dose rate (μGy/h) 15.3 23.6 25.0 Cs Total dose rate (μGy/h) 3.11 2.46 3.51 Pu Total dose rate (μGy/h) 10.5 20.8 21.2 Th Total dose rate (μGy/h) 1.68 0.33 0.33 CR Cs (Bq/kg:Bq/l) 10400 10400 10400 CR Pu (Bq/kg:Bq/l) 1100 1100 1100 CR Th (Bq/kg:Bq/l) 100 100 100

Amphibian (ERICA and R&D128) cf Geometry 3 (RESRAD-BIOTA)

Total dose rate (μGy/h) 5.35 7.96 8.02 Cs Total dose rate (μGy/h) 3.13 3.54 3.44 Pu Total dose rate (μGy/h) 2.20 4.35 4.42 Th Total dose rate (μGy/h) 0.03 0.06 0.17 CR Cs (Bq/kg:Bq/l) 9300 9300 9300 CR Pu (Bq/kg:Bq/l) 230 230 230 CR Th (Bq/kg:Bq/l) 110 110 110

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• Decision to further compare the screening tiers of the three models – 1 Bq per unit media model runs

• Associated ‘request’: can PROTECT establish the degree of conservatism ?

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1.Screening tiers – similarities/differences(where we think the conservatism is)

2.Comparison of outputs

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ERICA-Tool - Tier 1• Recommends enter maximum media activity

concentration• 95th percentile environmental media concentration

limits (EMCLs) predicted using default transfer parameters pdfs (conservative habitat assumption)– 10 µGy h-1

– 40 µGy h-1 terrestrial animals / 400 µGy h-1 plants and all aquatic organisms

• Risk quotients reported for most limiting organism (and media) for each radionuclide and for ecosystem

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ERICA-Tool Tier 1 result

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ERICA EMCLsEMCL for water – takes into account external exposure from sediment (kd) or water and internal exposure estimated from water conc. using CR

EMCL for sediment - takes into account external exposure from sediment or water (kd) and internal exposure estimated from water conc. (kd) using CR

Freshwater EMCLs

Cd-109

Sediment = 2.61E4 Bq/kg

Water = 51 Bq/l

Cs-137

Sediment = 8000 Bq/kg

Water = 5.1E-2 Bq/l

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ERICA EMCLs

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ERICA Tier 2 • Organism specific dose rates and RQs (from

total predicted dose rate) reported:– Best estimate– Conservative estimate

• Conservative dose estimated by applying uncertainty factor (UF) to the best estimate, where: – UF 3 ≈ 95th percentile prediction– UF 5 ≈ 99th percentile prediction

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ERICA Tier 2

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ERICA Tier 2

• In theory conservative estimate with UF=3 should approximate to Tier 1 result [with same input] and Tier 3 95th percentile prediction– Generally works: some case where it does not

for aquatic ecosystems if input to sediment T1 RQ T2 conservative RQ T3 95th %ile ‘RQ’

Pb-210 0.73 (phytoplankton) 0.04 (gastropod) 0.22 (insect larvae) Po-210 0.09 (mollusc) 0.01 (mollusc) 0.1 (mollusc) Ra-226 14 (plant) 3.1 (plant) 15 (insect larvae)

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1.E-03 1.E-02 1.E-01 1.E+00 1.E+01 1.E+02 1.E+03

D-Max

DosDiMEco

R&D128

ERICA

FASTer

LIETDOS-BIOTA

RESRAD-BIOTA

Rodent

Large mammal

Bird

Amphibian

Reptile

Invertebrate

Vegetation

Cs-137 BWG Chernobyl

A thought on UF =3

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RESAD-BIOTA (USDOE) Tier 1

• Recommend enter maximum media activity concentration

• Media activity concentrations compared to biota concentration guidelines (BCG):– Infinitely large/small geometries assumed – 100 % in soil; sediment-water interface– Conservative CR (BiV) values (not kd)– 1 mGy/d (40 µGy h-1) terrestrial & riparian animals / 10

mGy/d (400 µGy h-1 ) terrestrial plants & aquatic animals

• More limited range of organisms considered than ERICA (which includes e.g. planktons, lichen which tend to have ‘high exposure’ estimates)

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RESRAD-BIOTA Tier 1 CRs

• Aquatic animals – maximum– Predominantly taken from Till & Meyer 1983

maximum of the 84th %ile from collated data for fish, mollusc or crustacean

• Terrestrial plants – maximums– Predominantly taken from Till & Meyer 1983

considers food crops, forage & grass

• Terrestrial/Riparian animals – most derived using kinetic-allometric approach – 95th %ile

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BGCs

• Terrestrial - Soil & water• Aquatic & Riparian - Sediment & water

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BGCs• Aquatic animals

– Sediment - External exposure from sediment– Water – Internal & external exposure from water

• Riparian animals– Sediment – Internal & external exposure from sediment– Water – Internal & external exposure from water

• Terrestrial animals – Soil - Internal & external exposure from soil– Water - Internal & external exposure from water

• Terrestrial plants– Soil - Internal & external exposure from soil– Water - External exposure from water

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EA R&D128 - screening

• As applied – maximum inputs

• Compares results to 5 µGy h-1 for screening (40 µGy h-1 action level)

• Default transfer parameters used– Some transfer values are highly conservative

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Screening tier predictions•Assuming 1 Bq soil/water/sediment

•Against 40/400 µGy h-1

•Terrestrial – freshwater only [RESRAD-BIOTA does not consider marine]

•Radionuclides common to RESRAD-BIOTA & ERICA-Tool

•Not H-3 & C-14 for terrestrial: RESRAD-BCGs for soil; ERICA EMCL for air

•Compared as RQs

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Terrestrial

RESRAD-BIOTA & ERICA-Tool

+ EA R&D128

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Terrestrial – EA 5 µGy h-1

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RQ Min/Max > 10

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Freshwater – input to water

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RQ Min/Max > 10

ERICA kd’s often comparatively high

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Freshwater – input to sediment

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RQ Min/Max > 10

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Comment

• Used in basic screening assessments (their envisaged main use) the readily available models can give widely differing results– (yet again) predominantly explained by

transfer elements