What to look for when interpreting an assessment

Nick Beresford (CEH)

What to look for when interpreting an assessment

www.ceh.ac.uk/PROTECT

Objective

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


Chronology

Environmental Radiological assessment approaches have developed rapidly over the last 10 y

A number of approaches have been made freely available Some of these have been superseded But they are still available & are being used


Chronology UK

Environment Agency R&D128 - 2001 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)


Chronology

Europe FASSET (EC) 2001-2004

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


Chronology

Europe EPIC (EC) 2000-2003

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


Chronology Europe

ERICA (EC) 2004-2007 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


Chronology Europe

ERICA (EC) 2004-2007 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 (p

arameters) rather

than develop R&D128

EC PROTECT supported th

e

10µGy/h screening dose rate –

using additional data and im

proved

data selection


Chronology International

IAEA (2009-) Developing wildlife transfer parameter handbook and

associated on-line database Database will be maintained and updates released

annually


Chronology 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

Draft report presenting CR values for RAPs currently with main Commission

Will be used to update the ERICA Tool CR values

(and recalculate EMCLs)


Chronology 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


So don’t ......

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 (there’s a reason these were not included in ERICA)


Misuse of default values 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 values very generic and conservative


Misuse of default values

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


Double accounting Some scope for ‘double accounting’

associated with daughter product half-life cut-offs e.g. R&D128 includes all 234Th and 234U in DCCs

for 238U Entering both 234Th and 238U activity concentrations

would over estimate dose rates RESRAD-BIOTA and ERICA both offer the user

the opportunity to do similar

How do screening tiers compare?


Screening tier - recap

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’]

‘Concentration limits’ 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

ERICA Tool - EMCLs

Estimated assuming: Habitat assumption to maximise exposure Probability distributions associated with the default

CR and Kd 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

RESRAD-BIOTA - BCGs

Estimated assuming: Infinitely large (internal) and small (external)

geometries for dose calculations Daughter T1/2’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

RESRAD-BIOTA - BCGs

Estimated assuming: Infinitely large (internal) and small (external)

geometries for dose calculations Daughter T1/2’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


Screening Tier Comparison

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

Input data - freshwaterActivity concentration (Bq l-1 or Bq kg-1)

FW1 FW2 FW3 FW4

Nuclide Water Sediment Water Sediment Water Water Sediment3H 5.60x104 2.78x103 14C 4.81x10-1

60Co 2.52x10-2 1.59x102 8.51x10-2 90Sr 1.60x10-1 6.00x102 7.50x10-3 9.60x10-1 2.74x10-1

106Ru 2.60 2.32x103 8.14x10-1 131I 1.10x10-1 1.10 1.44x10-1

137Cs 8.80x10-2 2.08x103 8.50x10-3 8.50 4.44x10-3 210Po 5.00x10-2 3.70x102 3.70x10-2 1.51x103

234U** 8.00x10-2 2.05x101 2.00 1.00x102 3.05x10-1 2.15x104

234Th*** 8.00x10-2 1.00x102 1.80 9.10x101 3.05x10-1 2.15x104

238U 8.00x10-2 1.00x102 1.80 9.10x101 3.05x10-1 2.15x104

239Pu 9.50x10-5 5.06x101 241Am 5.00x10-3 5.00x101

Input data - terrestrial

Nuclide T1 T2 T3

Soil (Bq kg-1) Air (Bq m-3) Soil (Bq kg-1) Groundwater (Bq m-3)

Soil (Bq kg-1)

3H 6.59x102 4.81x107 7.00x109

14C 4.81x10-1 2.16x103 2.37x106

60Co 4.52x102

90Sr 1.85137Cs 1.80x102 2.85x101

234U** 6.09x104 6.08234Th*** 9.40x103 6.08238U 9.40x103 6.08239Pu 7.00

EA R&D128 RESRAD-BIOTA ERICA Tool

Radionuclide

Most exposed group RQ



FW13H All organisms 5.5x10-2 Riparian animal 2.3x10-2 Phytoplankton 1.6x10-1

60Co Bacteria 9.5x10-3 Aquatic animal 1.9x10-2 Insect larvae 1.3

90SrAmphibian, Duck 4.5x10-2 Riparian animal 1.7x10-1 Insect larvae 4.9x10-2

106Ru Duck 1.8x101 n/i Insect larvae 2.0x101

137Cs Duck 4.2x10-1 Riparian animal 3.0x10-1 Insect larvae 1.7131I Duck 9.1x10-4 Riparian animal 8.9x10-4 Phytoplankton 5.3x10-3

210Po

Large benthic crustacean, Small benthic crustacean, Benthic mollusc 8.5x101 Aquatic animal 1.5x10-1 Bivalve mollusc 1.8x101

234U n/a Aquatic animal 4.3x10-1 Vascular plant 6.4x101

234Th n/a n/a Insect larvae 8.6x101

238UAmphibian, Duck 1.3x102 Aquatic animal 3.9x10-1 Vascular plant 2.7x102

239Pu Amphibian 3.0x10-1 Riparian animal 9.5x10-4 Phytoplankton 8.0x10-2

241AmAmphibian, Duck 2.5 Aquatic animal 1.2x10-2 Phytoplankton 1.9

SUM 2.4x102 1.5 4.6x102

Fre

shw

ater

EA R&D128+ RESRAD-BIOTA ERICA Tool

Radionuclide




FW290Sr Duck 5.7x10-4 Riparian animal 3.1x10-3 Insect larvae 2.1x10-3

137Cs Duck 1.7x10-3 Riparian animal 4.3x10-2 Insect larvae 1.1x10-3

234U n/a Aquatic animal 1.1x101 Vascular plant 3.1x102


238U Duck 1.2x102 Aquatic animal 8.7 Vascular plant 2.4x102

SUM 1.2x102 1.9x101 2.5x103

Freshwater


Radionuclide





14C Duck 1.0x10-2 Riparian animal 8.5x10-2 Bird 3.1x10-2

60Co Bacteria 2.6x10-2 Aquatic animal 3.1x10-2 Insect larvae 4.690Sr Duck 2.1x10-2 Riparian animal 1.1x10-1 Insect larvae 7.8x10-2

106Ru Duck 6.2x10-1 n/i Insect larvae 6.4131I Duck 1.2x10-3 Riparian animal 1.2x10-3 Phytoplankton 6.9x10-3


SUM 6.9x10-1 2.4x10-1 1.1x101

Freshwater


RadionuclideMost exposed

group RQMost exposed


group RQ

FW4

210Po


234U n/a Aquatic animal 1.6 Vascular plant 6.7x104



SUM 2.9x104 4.6 1.3x105

Freshwater


RadionuclideMost exposed



group RQ

FW4

210Po


234U n/a Aquatic animal 1.6 Vascular plant 6.7x104



SUM 2.9x104 4.6 1.3x105

Freshwater

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


Radionuclide





14C Duck 1.0x10-2 Riparian animal 8.5x10-2 Bird 3.1x10-2

60Co Bacteria 2.6x10-2 Aquatic animal 3.1x10-2 Insect larvae 4.690Sr Duck 2.1x10-2 Riparian animal 1.1x10-1 Insect larvae 7.8x10-2

106Ru Duck 6.2x10-1 n/i Insect larvae 6.4131I Duck 1.2x10-3 Riparian animal 1.2x10-3 Phytoplankton 6.9x10-3


SUM 6.9x10-1 2.4x10-1 1.1x101

Freshwater

Co-60 (& Ru-106) – ERICA Tool kd values >> than values in other two models

TerrestrialEA R&D128 RESRAD-BIOTA ERICA Tool

RadionuclideLimiting organism RQ

Limiting organism RQ


T1137Cs Carnivorous

mammal3.6x10-2 Terrestrial

animal9.4x10-1 Mammal (Deer) 5.8x10-2

234U n/a Terrestrial animal

1.3 Lichen & bryophytes

3.7x101

234Th n/a n/a Grasses & Herbs 5.9x10-2

238U Fungi 1.4x102 Terrestrial plant 6.5x10-1 Lichen & bryophytes

6.2

239Pu Fungi 5.8x10-2 Terrestrial plant 6.0x10-4 Lichen & bryophytes

6.4x10-3

SUM 1.4x102 2.9 4.3x101

Terrestrial

T2 EA R&D128 RESRAD-BIOTA ERICA Tool3H Fungi 1.4x10-1 Terrestrial

animal3.3x101 Detritivorous

invertebrate2.5x10-1

14C Seed 6.3x10-3 Terrestrial animal

6.0x10-2 Mammal (Deer) 5.8x10-3

60Co Fungi 5.3x10-2 Terrestrial plant 8.0x10-2 Mammal (Rat) 6.1x10-2

90Sr Carnivorous mammal

5.9x10-4 Terrestrial animal

8.9x10-3 Reptile 4.9x10-3

137Cs Carnivorous mammal


1.5x10-1 Mammal (Deer) 9.1x10-3

SUM 2.0x10-1 3.4x101 3.3x10-1

Terrestrial


Radionuclide




T3226Ra Fungi 1.8 Terrestrial plant 1.1x10-1 Lichen &

bryophytes1.3x10-1


1.3x10-4 Lichen & bryophytes

3.6x10-3


238U Fungi 8.8x10-2 Terrestrial plant 4.2x10-4 Lichen & bryophytes

4.0x10-3

SUM 1.9 1.1x10-1 1.4x10-1

Terrestrial

T2 EA R&D128 RESRAD-BIOTA ERICA Tool3H Fungi 1.4x10-1 Terrestrial

animal3.3x101 Detritivorous

invertebrate2.5x10-1

14C Seed 6.3x10-3 Terrestrial animal

6.0x10-2 Mammal (Deer) 5.8x10-3

60Co Fungi 5.3x10-2 Terrestrial plant 8.0x10-2 Mammal (Rat) 6.1x10-2

90Sr Carnivorous mammal


8.9x10-3 Reptile 4.9x10-3

137Cs Carnivorous mammal


1.5x10-1 Mammal (Deer) 9.1x10-3

SUM 2.0x10-1 3.4x101 3.3x10-1

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.

TerrestrialEA R&D128 RESRAD-BIOTA ERICA Tool

RadionuclideLimiting organism RQ



T1137Cs Carnivorous

mammal3.6x10-2 Terrestrial

animal9.4x10-1 Mammal (Deer) 5.8x10-2


1.3 Lichen & bryophytes

3.7x101


238U Fungi 1.4x102 Terrestrial plant 6.5x10-1 Lichen & bryophytes

6.2

239Pu Fungi 5.8x10-2 Terrestrial plant 6.0x10-4 Lichen & bryophytes

6.4x10-3

SUM 1.4x102 2.9 4.3x101

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


Screening tier comparison Can be considerable variation in screening tier

results Some of variation can be understood:

CR and kd (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


Summary Do not use/accept out of date approaches –

unless justified Ensure no misuse of default values provided

by various approaches There are differences between approaches

Dosimetric methods tend to give similar results Transfer parameters can add significant

variation Screening tiers

Documents

What to look for when interpreting an assessment