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Centre for Ecology & Hydrology – Lancaster 27 th – 29 th June 2012.

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Presentation on theme: "Centre for Ecology & Hydrology – Lancaster 27 th – 29 th June 2012."— Presentation transcript:

1 Centre for Ecology & Hydrology – Lancaster 27 th – 29 th June 2012

2  Give an overview of what may impact on assessment results using the available approaches  In part based on things we know are being done  Consider chronology of development, misuse of default values, double accounting, screening tier application  Not considering dispersion modelling and sampling strategies

3  Environmental Radiological assessment approaches have developed rapidly over the last 12 y  A number of approaches have been made freely available  Some of these have been superseded  But they are still available & are being used

4  UK  Environment Agency R&D  Spreadsheet model for limited number of radionuclides  Comparatively limited review to derive CR values  Dosimetry methods similar to later approaches  Environment Agency Sp1a – 2003  Supports R&D128 including derivation of complete CR data sets using a ‘guidance approach’ (can be extremely conservative)

5  Europe  FASSET (EC)  Establish a framework for radiological environmental protection from source characterisation – interpretation, including:  Tabulated CR and DCC values for:  radionuclides of 20 elements  circa 30 reference organism in 7 ecosystems  Developed the on-line FASSET Radiation Effects Database

6  Europe  EPIC (EC)  Establish a framework for radiological environmental protection for the Arctic  Ran concurrent to FASSET and shared CR database  Although presented differently and for only 12 radionuclides  DCCs derived by a different method  Allowed participation of Russian institutes leading to EPIC effects database

7  Europe  ERICA (EC)  Developed the CR and effects (FREDERICA) databases from FASSET & EPIC  Developed FASSET dosimetry methodology  Adapted ‘guidance’ for selecting missing CRs from EA SP1a  Output - the ERICA Tool implementing the ERICA Integrated Approach  More generic ecosystem types (because of lack of data) than FASSET and adapted reference organism list (to encapsulate European protect species & remove some unjustified sub-categories)  Derived 10 µGy/h screening dose rate (by SSD)  Being maintained and updated

8  Europe  ERICA (EC)  Developed the CR and effects (FREDERICA) databases from FASSET & EPIC  Developed FASSET dosimetry methodology  Adapted ‘guidance’ for selecting missing CRs from EA SP1a  Output - the ERICA Tool implementing the ERICA integrated approach  More generic ecosystem types (because of lack of data) than FASSET and adapted reference organism list (to encapsulate European protect species & remove some unjustified sub-categories)  Being maintained and updated ERICA supersedes both FASSET and EPIC outputs & EA state intention to move to ERICA (parameters) rather than develop R&D128 EC PROTECT supported the 10µGy/h screening dose rate – using additional data and improved data selection

9  International  IAEA (2009-)  Developing wildlife transfer parameter handbook and associated on-line database  Database will be maintained and updates released annually

10 ERICA New & review data EA R&D128 EPIC FASSET IAEA 422 Wildlife TRS ICRP 114 Canadian U-mine industry COG monitoring data Russian language literature SKB reports Japanese estuaries Australian data Data from new studies Post ERICA literature review and more

11  International  IAEA (2009-)  Developing wildlife transfer parameter handbook and associated on-line database  Database will be maintained and updates released annually  ICRP Committee 5 (2005-)  Developing a framework (ICRP-108)  Currently provided tabulated DCC values (using ERICA methodology) and summarised effects information  Report presenting CR values for RAPs now available (ICRP-114) Will be used to help update the ERICA Tool CR values (and recalculate EMCLs)....

12  USA  USDOE Graded Approach (2002)  Initially supported by BCG-Calculator spreadsheet model. Still available – but replaced by:  RESRAD-BIOTA  Limited and conservative CR values for generic organisms  RESRAD-BIOTA v1.5 (2009) includes values from the ERICA CR database in supporting documentation for application in uncertainty analysis

13  Use out of date approaches unless you can justify why they have been used, e.g.:  OK to use R&D128 for noble gases  Not OK to use FASSET CR values because they offer more ‘refined’ reference organism list/ecosystem range.... but do be aware that this is an evolving area

14  To serve the purpose for which they were intended RESRAD-BIOTA, R&D128(SP1a) and the ERICA Tool give a complete list of radionuclide-organism transfer parameters.  ERICA Tool and R&D128 missing values derived using ‘guidance’ approaches. These should not be blindly used in higher tier assessments nor should they be picked out for use in other models/recommendations without being clearly identified as such  RESRAD-BIOTA Biv (=CR) values very generic and conservative

15  ERICA and R&D128 both clearly identify values which have been derived via guidance approach rather than data  But have been taken as ‘values’

16  Some scope for ‘double accounting’ associated with daughter product half-life cut-offs  e.g. R&D128 includes all 234 Th and 234 U in DCCs for 238 U  Entering both 234 Th and 238 U activity concentrations would over estimate dose rates  RESRAD-BIOTA and ERICA both offer the user the opportunity to do similar

17  Some scope for ‘double accounting’ associated with daughter product half-life cut-offs  e.g. R&D128 includes all 234 Th and 234 U in DCCs for 238 U  Entering both 234 Th and 238 U activity concentrations would over estimate dose rates  RESRAD-BIOTA and ERICA both offer the user the opportunity to do similar Understand what daughters are/are not included in default DCCs especially important for assessments of natural radionuclides

18

19  Aim - to enable sites of negligible concern to be identified and removed from need for further assessment – with a high degree of confidence  Envisaged that most sites will only need this level of assessment [i.e. ‘be screened out’]

20  Input media concentrations compared to predefined concentrations = media concentration giving rise to screening dose rate  ERICA: ‘environmental media concentration limits’ EMCLs  RESRAD-BIOTA: ‘biota concentration guidelines’ BCGs

21 Estimated assuming:  Habitat assumption to maximise exposure  Probability distributions associated with the default CR and K d databases were used to determine 5th percentile EMCL  No conservatism applied to dosimetry  For aquatic ecosystems EMCL for water includes consideration of external dose from sediment and that for sediment includes external dose from water and biota-water transfer

22 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

23  Run RESRAD-BIOTA, ERICA Tool and EA R&D128 against 10 µGy/h screening dose rate  Data suitable for application in screening tier assessment report – maximum media activity concentrations for  Four freshwater  Three terrestrial scenarios  Taken from SENES-WNA report 2007

24 Activity concentration (Bq l -1 or Bq kg -1 ) FW1FW2FW3FW4 NuclideWaterSedimentWaterSedimentWater Sediment 3H3H5.60x x C 4.81x Co2.52x x x Sr1.60x x x x x Ru x x I1.10x x Cs8.80x x x x Po5.00x x x x U ** 8.00x x x x x Th *** 8.00x x x x x U8.00x x x x x Pu9.50x x Am5.00x x10 1

25 EA R&D128 + RESRAD-BIOTAERICA Tool Radionuclide Most exposed groupRQ Most exposed groupRQ Most exposed groupRQ FW3 3H3HAll organisms2.7x10 -3 Riparian animal1.1x10 -3 Phytoplankton8.1x CDuck1.0x10 -2 Riparian animal8.5x10 -2 Bird3.1x CoBacteria2.6x10 -2 Aquatic animal3.1x10 -2 Insect larvae SrDuck2.1x10 -2 Riparian animal1.1x10 -1 Insect larvae7.8x RuDuck6.2x10 -1 n/iInsect larvae IDuck1.2x10 -3 Riparian animal1.2x10 -3 Phytoplankton6.9x CsDuck8.9x10 -4 Riparian animal1.1x10 -2 Insect larvae8.7x10 -2 SUM6.9x x x10 1 Co-60 (& Ru-106) – ERICA Tool k d values >> than values in other two models

26 EA R&D128RESRAD-BIOTAERICA Tool Radionuclide Most exposed groupRQ Most exposed groupRQ Most exposed groupRQ FW4 210 Po Large benthic crustacean, Small benthic crustacean, Benthic mollusc3.5x10 2 Aquatic animal1.1x10 -1 Bivalve mollusc1.4x Un/aAquatic animal1.6Vascular plant6.7x Thn/a Insect larvae3.3x UDuck2.9x10 4 Aquatic animal2.0Vascular plant5.7x10 4 SUM2.9x x10 5 U-238 – ERICA Tool and EA R&D128 RQ estimated from input sediment; kd value used estimates much higher water activity concentration than observed; RESRAD- BIOTA uses water and sediment inputs separately

27 NuclideT1T2T3 Soil (Bq kg -1 )Air (Bq m -3 )Soil (Bq kg -1 )Groundwater (Bq m -3 ) Soil (Bq kg -1 ) 3H3H6.59x x x C4.81x x x Co4.52x Sr Cs1.80x x U ** 6.09x Th *** 9.40x U9.40x Pu7.00

28 T2EA R&D128RESRAD-BIOTAERICA Tool 3H3HFungi1.4x10 -1 Terrestrial animal 3.3x10 1 Detritivorous invertebrate 2.5x CSeed6.3x10 -3 Terrestrial animal 6.0x10 -2 Mammal (Deer)5.8x CoFungi5.3x10 -2 Terrestrial plant8.0x10 -2 Mammal (Rat)6.1x SrCarnivorous mammal 5.9x10 -4 Terrestrial animal 8.9x10 -3 Reptile4.9x CsCarnivorous mammal 5.7x10 -3 Terrestrial animal 1.5x10 -1 Mammal (Deer)9.1x10 -3 SUM2.0x x x10 -1 H-3 – Difference in input options RESRAD-BIOTA = soil (+ groundwater) other two models = air. Soil concentrations in excess of what would be anticipated from air.

29 EA R&D128RESRAD-BIOTAERICA Tool Radionuclide Limiting organismRQ Limiting organismRQ Limiting organismRQ T1 137 CsCarnivorous mammal 3.6x10 -2 Terrestrial animal 9.4x10 -1 Mammal (Deer)5.8x Un/aTerrestrial animal 1.3Lichen & bryophytes 3.7x Thn/a Grasses & Herbs5.9x UFungi1.4x10 2 Terrestrial plant6.5x10 -1 Lichen & bryophytes PuFungi5.8x10 -2 Terrestrial plant6.0x10 -4 Lichen & bryophytes 6.4x10 -3 SUM1.4x x10 1 Organism – ERICA Tool and EA R&D128 include organisms with comparatively high CR values (Lichen&Bryophytes, fungi) – not included in RESRAD-BIOTA Guidance values – Fungi U (& Ra) CR values in R&D128 are guidance values. Values used ≥10x higher than data for fungi

30  Can be considerable variation in screening tier results  Some of variation can be understood:  CR and k d (including if 95%’ile, maximum, best estimate used)  Organism  How sediment and water inputs used  Input options  Exposure geometry  Other Tier 1 type approaches being developed  Need to compare & understand before application

31  Do not use/accept out of date approaches – unless justified  Be aware of potential changes as a consequence of recent transfer parameter reviews  Ensure no misuse of default values provided by various approaches  Use alternatives where justified  There are differences between approaches  Dosimetric methods tend to give similar results  Transfer parameters can add significant variation  Screening tiers


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