A Non-Human Species Radiological Impact Assessment
by
Sarah Hunak
A dissertation submitted to the Department of Physics,
University of Surrey, in partial fulfilment of the degree of
Master of Science in Radiation and Environmental Protection.
Department of Physics
Faculty of Electronics & Physical Sciences
University of Surrey
September 2009
© Sarah Hunak 2009
Abstract
Environmental legislation and policy decisions at both national and regional levels have resulted in
a requirement to assess the environmental impact of ionising radiation. This includes impact
assessments on humans and also non-humans. This report will look at the current approaches to
assessing risk to non human species with the use of the ERICA (Beresford et al, 2007) integrated
approach and the Environment Agency R&D Publication 128 Impact assessment of Ionising
Radiation on Wildlife (Copplestone, 2001) for carrying out generic radiation dose assessments on
non-human species.
i
Acknowledgements
Thanks go to amec, especially Sarah Warner Jones for her help during this project.
Thanks also to Paddy Regan for his support.
ii
Tables of Contents
Contents
Abstract ................................................................................................................................................. i
Acknowledgements ..............................................................................................................................ii
Tables of Contents ..............................................................................................................................iii
Introduction .......................................................................................................................................... 1
Environmental Guidance...................................................................................................................... 4
Methodology ........................................................................................................................................ 6
The ERICA Integrated Approach .................................................................................................... 6
The Sellafield Site ................................................................................................................................ 9
Species in the area .......................................................................................................................... 11
Bats............................................................................................................................................. 15
Badgers....................................................................................................................................... 16
Determination of habitats and species ........................................................................................... 20
Detemining Habitats ...................................................................................................................... 21
Habitat 1: Terrestrial .................................................................................................................. 21
Habitat 2: Marine ....................................................................................................................... 21
Habitat 3: Freshwater ................................................................................................................. 21
Data Used ........................................................................................................................................... 22
Methodology for ERICA and R&D 128 Dose Assessments ............................................................. 27
Freshwater ecosystem modelling within ERICA ........................................................................... 29
Freshwater methodology ................................................................................................................ 29
Results and Discussion....................................................................................................................... 31
Habitat 1 ......................................................................................................................................... 31
Habitat 2 ......................................................................................................................................... 33
Habitat 3 ......................................................................................................................................... 34
Discussion .......................................................................................................................................... 35
Uncertainties .................................................................................................................................. 35
Conclusions ........................................................................................................................................ 37
References .......................................................................................................................................... 38
iii
Tables
Table 1:
Table 2:
Table 3:
Table 4:
Table 5:
Table 6:
Table 7
Table 8:
Table 9:
Table 10:
Table 11:
Table 12:
Table 13:
Animal species recorded in Sellafield area and ERICA reference ................................ 12
Plant species recorded in Sellafield area and ERICA reference .................................... 14
“Add new organism” parameters for ERICA ................................................................ 17
Guidance to assess exposure to terrestrial biota outside the defined mass ranges ......... 18
Annual gaseous discharge limits .................................................................................... 22
Annual liquid discharge limits ....................................................................................... 23
Habitat 1. Air and soil concentrations resulting from terrestrial discharges from ............
Sellafield ........................................................................................................................ 24
Habitat 2. Seawater and seabed sediment concentrations resulting from marine .............
discharges from HPC ..................................................................................................... 25
Calculations for freshwater Habitat 3 ............................................................................ 26
ERICA Results for Habitat 1 ......................................................................................... 31
Habitat 1. R&D128 results for Sellafield Site noble gas discharges (μGy h-1) ............ 32
ERICA results for Habitat 2 ........................................................................................... 33
ERICA results for Habitat 3 ........................................................................................... 34
Figures
Figure 1:
Figure 2:
Figure 3:
Figure 4:
Figure 5:
Figure 6:
iv
Map of UK showing th edose to members of the public from direct radiation and waste
discharges. ........................................................................................................................ 9
Location of the Sellafield site with respect to the UK. .................................................. 10
International Nuclear Even Scale ................................................................................... 11
Average bat dimensions ................................................................................................. 16
Map of the locations of the three habitats. ..................................................................... 20
Flowchart of the operation of an ERICA assessment .................................................... 28
Introduction
The effect of ionising radiation on humans is a well documented and important topic that has given
rise to many laws and regulations over the years.
The effects on non-human species and the environment, however, is not so well documented and
not subject to the same international and regional legislations applied to the protection of humans.
In the 1970s, the issue of the protection of non-human species and the environment started to
become perceived as increasingly important. Indeed, the International Commission on Radiological
Protection (ICRP) published in its 26th publication (ICRP, 1977) that if humans were adequately
protected, then everything else probably would be too. Yet since this primitive approach, more
attention has been paid to the protection of non-human species and their surrounding environment
and they now play a much more important role in legislations and conventions.
The Convention for the Protection of the Marine Environment of the North-East Atlantic (OSPAR
Convention, 1998) specified that there should be a prevention of pollutions of the maritime area
from ionising radiation. The next year, the International Atomic Energy Agency (IAEA) published
“Protecting the Environment from the Effects of Ionising Radiation” (IAEA, 1999) which set down
guidelines for protection of the environment. Since this change in the 1970s, there has been a
definite shift in society from an anthropocentric approach to a biotic and abiotic approach to
radiation protection.
When considering the effects of ionising radiation on humans, the main concern is focussed on the
consequences on human health. When studying the effects on non-human species, the focus is on
seven main biological effects:
 Mutation;
”A change in the chromosome or genes of a cell which may affect the structure and
development of the resultant offspring” – Collins concise dictionary.
 Morbidity;
A reduction of lifespan due to the loss of functional capacities or reduced fitness resulting in
the organism being less competitive and subject to more stressors.
1
 Reproduction;
A decline in reproductive capacity resulting in the reduced number of offspring or sterility.
 Mortality;
An increase in death rate, the ratio of number of deaths to a given population number.
 Stimulation;
Any defence mechanisms in an organism that could lead to an increase in survival rates,
number of offspring and growth.
 Adaptation;
Adjustment of an organism’s physiology, biochemistry or DNA that better adapts them to
conditions/environments that they previously would not have survived.
 Ecological effects.
Non-direct ecological effects of radiation due to interactive relationships between
populations, including competition, predator-prey interaction and mutualism. The radiation
responses of individual populations cause indirect changes in the ecological balance
between species in the ecosystem - (Whicker, Schultz, 1982; IAEA, 1992)
The consequence of exposure to ionising radiation, for both human and non-human species is
concentrated on the biological effect to DNA within the organism. Ionising radiation can cause
damage to living tissue from the transfer of energy to the cellular structure by causing excitation
and ionisation to the molecules within the living tissue. Depending on the level of damage, the cell
can sometimes repair itself. When the levels of radiation a cell is exposed to are high, then
irreparable damage can often occur and result in the death of the cell. DNA is the primary target for
cell damage from ionising radiation and can suffer from mutations and breaks in the DNA strand.
Data for the effects of ionising radiation on humans is readily available. Years of study and the
implementation of “Reference man” (ICRP, 2002) have lead to a greater understanding of
consequence. “Reference man” is not meant to serve as an “average” man, but a “standard” man
from which a point of reference for dose estimations on humans can be made.
2
With non-human species, there is information gathered from lab work, and also from the study of
accidental releases of high levels of radiation into the environment (IAEA, 1992; UNSCEAR, 1996;
Van der Stricht and Kirchmann, 2001) and research is revealing that effects on the reproduction of a
species are the most limiting to its survival within the environment as a whole. Reference flora and
fauna now are being developed for the same purpose as “Reference man”.
The effects of radiation and humans and non-human species has much in common, but the
limitations to the knowledge about the effects on non-human species lag far behind that of humans
not due to a lack of data, but rather the organisation and interpretation so that this information can
be used to assess potential impacts.
Currently, the standards used for the assessment of impact on non-human species are based around
the sources of available information. These include the software ERICA and it’s parallel running
database FREDERICA. Environment Agency standards for the United Kingdom recommend the
use of the software ERICA when performing impact assessments on non-human species.
3
Environmental Guidance
The UK and the word have a responsibility to ensure that habitats and species are sufficiently
protected. This is done via a series or legislations, regulations and designation of protected sites.
International legislation states that certain species, including great crested newts and bats, require
protection. The European Community’s Habitats Directive (92/43/EEC) (JNCC p1374) implements
this in European legislation and is transposed into British law through inclusion on Schedule 2 of
The Conservation (Natural Habitats, &c.) Regulations 1994 (SI, 1994). Additionally, UK national
legislation provides protection in the Wildlife and Countryside Act 1981 (SI, 1981). As amended it
provides protection to all British bird species, their nests and eggs (excluding some pest and game
species), selected animal species including great crested newts and all species of British bat, and
against damage to “any structure or place which any wild animal (included in the schedule) uses for
shelter and protection” and against disturbance whilst in such places.
In the United Kingdom conservation legislation considerations encompass radiological impacts, i.e.,
including the EC Habitats and Birds Directives (1992) on the conservation of natural habitats and
wild flora and fauna; and the Conservation (Natural Habitats) regulations 1994 which implements
the Habitats Directive (92/43/EEC) (JNCC p1374). The Habitats Directive requires steps to
maintain and restore to favourable conservation status of habitats and species of community level
interest. Other relevant legislation includes the Countryside & Rights of Way Act, (2000) and the
European Water Framework Directive (2000).
Designated protected sites were established in the UK and internationally to protect flora, fauna and
geographical or physiographical features. These include:
 Sites of Special Scientific Interest (SSSIs)
 Areas of Special Scientific Interest (ASSIs) in Northern Ireland
 Special Protection Areas (SPA)
 Special Areas of Conservation (SAC)
 Marine Nature Reserves (MNRs)
 National Nature Reserves
 Wetlands of International Importance – Ramsar Site
4
 Areas of Outstanding Natural Beauty
 Natural World Heritage Sites
5
Methodology
The software ERICA is based upon a joint effort between 15 institutions in seven European
countries and was developed under the EC 6th Framework Programme. The ERICA approach is
compatible
with
The
International
Commission
on
Radiological
Protection
(ICRP)
recommendations. The reference organisms used within ERICA complement the Reference Animals
and Plants proposed by ICRP (ICRP, 2007). It uses some of the plant and animal geometries
currently outlined within the Reference Animals and Plants, but is also broader in range so it can
add value within the ICRP processes and the wider field of radiological research. ERICA is
designed to fulfil the IAEA safety objective and the fundamental safety principles of protecting
people and the environment from harmful effects of ionising radiation and the protection of present
and future generations (IAEA, 2006). The assessment uses site-specific information with generic
reference organisms where possible.
The general method used to calculate environmental soil and water concentrations is based on EC
guidance document Radiation Protection 72 (Simmonds, J.R, et al. 1995). RP72 describes a
comprehensive model, i.e. Consequences of Releases to the Environment: Assessment Methodology
(CREAM). The NRPB model PC CREAM 98 (EUR17791) (Mayall, A, et al. 1997) was developed
as a tool for carrying out radiological impact assessments as detailed in RP72. This model is used to
carry out the assessments of concentrations in soil and water.
The ERICA Integrated Approach
The Tier 1 ERICA assessment is designed to be simple and conservative, requiring a minimum of
input data and enabling the user to exit the process and exempt the situation from further evaluation,
provided the assessment meets a predefined screening criterion. The default screening criterion in
the ERICA Integrated Approach is an incremental dose rate of 10 µGy h-1, to be used for all
ecosystems and organisms. This value was derived from a species sensitivity distribution analysis
performed on chronic exposure data in the FREDERICA database and is supported by other
methods for determining predicted no-effect values. Other default options are: a screening dose rate
of 40 µGy h-1 for terrestrial animal populations and 400 µGy h-1 for all other organisms is based on
historical international recommendations (IAEA, 1992; ICRP, 2003 and US DOE, 2002) and current
EA guidelines (Copplestone, D, 2001).
For Tier 1, the predefined screening dose rate is back-calculated to yield Environmental Media
Concentration Limits (EMCLs) for all reference organism/radionuclide combinations. The ERICA
Tool compares the input media concentrations due to discharges with the most restrictive EMCL for
6
each radionuclide and determines a risk quotient (RQ). If the RQ is less than one, then the tool
suggests that the user should exit the assessment process. If the RQ is greater than one, the user is
advised to continue with the assessment.
RQ 
M
EMCL
Where:
RQ is the risk quotient for a given radionuclide;
M is estimated or measured activity concentration for a given radionuclide in Bq l-1
for water, Bq kg-1 dry weight for soil/sediment or Bq m-3 for isotopes of C, H, P
and S within the terrestrial environment;
EMCL is the Environmental Media Concentration Limit for a given radionuclide for
the most limiting reference organism (in same units as M) and
EMCL 
Where:
is given by:
screening dose rate
F
F is the dose rate that a given organism will receive for a unit concentration of a
given radionuclide in an environmental medium.
Although the RQ approach might be deemed overly conservative, it was selected because it is
reasonably consistent with other assessment approaches currently available. It also reflects the
uncertainty associated with the lack of data for some radionuclide-reference organism
combinations. It is simple and resource effective – its conservatism bounds the uncertainty.
The Tier 2 ERICA analysis allows the user to be more interactive, to change the default parameters
and to select specific reference organisms. The evaluation is performed directly against the
screening dose rate, with the dose rate and RQs generated for each reference organism selected for
assessment. A ‘traffic light’ system is used to indicate whether the situation can be considered:
i – (green) of negligible concern (with a high degree of confidence);
ii – (amber) of potential concern, where more qualified judgements may need to be made and/or a
refined assessment at Tier 2 or an in-depth assessment in Tier 3 performed;
iii – (red) of concern, where the user is recommended to continue the assessment either at Tier 2 if
7
refined input data can be obtained or at Tier 3.
Decisions to exit an assessment given outcomes (ii) and (iii) should be justified, for example by
using information from FREDERICA provided in the ERICA Tool as ‘look-up effects tables’ for
different species groups.
Situations which give rise to a Tier 3 assessment are likely to be complex and unique; there is no
detailed or specific published guidance on how the Tier 3 assessment should be conducted. A Tier 3
assessment does not provide a simple yes/no answer, nor is the ERICA-derived incremental
screening dose rate of 10 µGy h-1 appropriate with respect to the assessment endpoint.
Not all radionuclides discharged are provided in the basic ERICA application. It is possible
however to derive dose conversion coefficients for any radioisotope included within the electronic
version of ICRP-38 (ICRP, 1983). Noble gases are not included and therefore the contribution from
these nuclides has not been incorporated in the dose estimates using the ERICA Tool. Instead, for
these, R&D128 is used. R&D128 uses the same EA biota dose limits as ERICA:
 terrestrial animal populations at chronic dose rates below 40 µGy h-1;
 terrestrial plant populations at chronic dose rates below 400 µGy h-1;
 populations of freshwater and coastal organisms at chronic dose rates below 400 µGy h-1.
Any organisms receiving a dose greater than 30% of these limits would be flagged as needing
further attention.
8
The Sellafield Site
This example assessment carried out in this report will use data from the Radioactivity in Food and
the Environment report 13 (RIFE 13, 2008). These annual reports use the results of monitoring of
radioactivity in food and the environment near nuclear sites to make an assessment of doses to the
public.
In the UK, there are currently 22 nuclear sites. These are illustrated on the map below, Figure 1,
with their associated doses to the public from direct radiation and radioactive waste discharges in
2007 (RIFE13, 2008). The dose limit to members of the public is shown to scale on the right hand
side of the map for comparison.
Figure 1:
Map of UK showing th edose to members of the public from direct radiation and
waste discharges.
9
It is clear, that none of these sites expose the public to greater than the public dose limit, yet without
defined screening levels for non-human organisms it is harder to say if these dose levels are harmful
to organisms other than humans with different masses and geometries to “Reference man”.
This is where the software ERICA can be used to estimate risk and dose to non-human species
around Sellafield in the north west of England.
The map below, Figure 2, shows the area around Sellafield Power Station. Sellafield (formerly
known as Windscale) is a nuclear processing and former electricity generating site, close to the
village of Seascale on the coast of the Irish Sea in Cumbria, England.
Figure 2:
Location of the Sellafield site with respect to the UK.
Facilities at the site include the THORP nuclear fuel reprocessing plant and the Magnox nuclear
fuel reprocessing plant. It is also the site of the remains of Calder Hall, the world's first commercial
nuclear power station, now being decommissioned, as well as some other older nuclear facilities.
Sellafield is located on a coastal location with nearby wetland habitats likely to support a range of
invertebrates as well as birds and other species of flora and fauna. Farming practices in the area are
currently tenanted farmland used for the rearing of livestock and cultivation of crops.
The soils around Sellafield have been identified as primarily deep, well drained coarse loamy and
sandy soils locally over gravel. This type of soil generally gives rise to neutral and acid pastures and
deciduous woodlands; acid communities such as bracken and gorse in the uplands (Cranfield
University, 2008).
10
Discharges of radioactive material have caused the site to be at the centre of controversy as between
1950 and 2000 there have been 21 accidents or incidents meriting rating on the International
Nuclear Event Scale (IAEA, 1990). This scale describes the severity of accidents or incidents, with
each level being 10 times more severe than the previous. These levels are illustrated in the diagram
below, Figure 3:
Figure 3:
International Nuclear Even Scale
Sellafield has had one level five incident, five level four incidents and fifteen at level three. The
Irish Sea, to which Sellafield discharges to, is considered to be one of the most heavily
contaminated seas in the world due to Sellafield discharges. Indeed, the OSPAR Commission
estimates 200 kg of plutonium has been deposited into its marine sediments. Cattle and fish in the
area are also reported to be contaminated with plutonium and caesium.
So, it is important to keep regular monitoring schemes in place, and also carry out radiological
impact assessments on non-human species in the area to ensure that radiation levels in the local area
are not at harmful levels.
Species in the area
A rudimentary desktop study has revealed many species of plants and animals in the area. Table 1
and Table 2 show species of animals and plants found in the local area and include several
mentioned in the Red Data Book (Joint Nature Conservation Committee). This is a list of species
whose continued existence is threatened. Reference to the Taxon Designations 2008 (JNCC p3408)
sourced from the Joint Nature Conservation Committee highlights that almost all of the species in
11
Table 1 and Table 2 are listed under one or more of the following reporting categories: The Bern
Convention, Birds Directive, Bonn Convention, EC Cites, Global Red List Status, Habitat and
Species Directive, Rare and Scarce Species (not based on International Union for Conservation of
Nature and Natural Resources (IUCN) criteria), Red Data Categories – Birds (not based on IUCN
criteria), Red Listing, UK Biodiversity Action Plan List, and the Wildlife and Countryside Act
1981. References are contained within the Taxon designations 2008 table.
Table 1:
Animal species recorded in Sellafield area and ERICA reference
Animal
ERICA reference
Mammals
Pipistrelle bat
User Defined
Water Vole
Freshwater mammal
Deer
Mammal (deer)
Badger
User Defined
Reptiles
Slow Worm
Reptile
Grass Snake
Reptile
Hoverfly
Flying Insect
Soldier flies1
Flying Insect
Aquatic snail
Gastropod
Hairy dragonfly
Flying Insect
Ladybird
Flying Insect
Whimbrel
Bird
Wigeon
Bird
Nightingale
Bird
Kestrel
Bird
Collared and Stock doves
Bird
Rock Pipit
Bird
Dunnock
Bird
Other
Bee
Flying insect
12
Trout
Pelagic Fish
Farm
Cow
Mammal (deer)
Sheep
Mammal (deer)
Pig
Mammal (deer)
Chicken
Bird
Marine
Plaice
Benthic fish
Cuttlefish
Mollusc
Skate
Benthic fish
Prawns
Crustacean
Sea Bass
Benthic fish
Sole
Benthic fish
Crustacean
Crustacean
Mollusc
Mollusc
Wild Fowl
Bird
Butterflies
\Dark green fritillary
Flying Insect
Meadow brown
Flying Insect
Marbled white
Flying Insect
Small heath
Flying Insect
Common blue
Flying Insect
13
Table 2:
Plant species recorded in Sellafield area and ERICA reference
Plants
ERICA reference
Hedgerow
Ash
Tree
Blackthorn
Tree
Brambles
Tree
Dog Rose
Shrub
Dogwood
Shrub
Elder
Tree
Elm
Tree
Field Maple
Tree
Hawthorn
Shrub
Ivy
Tree
Privet
Shrub
Wayfaring Tree
Tree
Spindle
Shrub
Other
Oilseed rape
Grasses & Herbs
Hay meadow
Grasses & Herbs
Deciduous woodland
Tree
Tussocky grassland
Grasses & Herbs
Marine
plants
and
algae
Macroalgae/vascular plants
Seaweed
Macroalgae
It is evident from these tables that there are many species of animals and plant in the area that
should be assessed for radiological impact. ERICA requires that the species and their dimensions
are defined in such a way that they can be modelled as a simplified ellipsoidal shape. This requires
only length, width and height. This simplified geometric shape is used for dose assessments and is
consistent with the Reference Animals and Plants method. Most species will fit within a generic
organism within ERICA, those that do not can easily be created with species specific parameters.
Not all species found in the area were directly matched with an identical reference organism in
14
ERICA. However, for many of these organisms, there is a similar organism in ERICA that is
sufficient for this assessment. The exceptions are the bat species and badgers for which new
organism parameters can be input into ERICA. Occupancy factors are given in Table 12, mass and
dimensions of these new organisms were entered as shown in Table 22.
Bats
Bats are included in Schedule 2 of The Conservation (Natural Habitats, &c.) Regulations 1994 (as
amended). The Regulations, commonly referred to as the “Habitats Regulations”, extend protection
against disturbance to those animals wherever they are present and provides tests against which the
permission for a development that may have an effect on a Schedule 2 protected species must be
assessed before permission can be given.
All British species of bat are protected under Schedule 5 of the Wildlife and Countryside Act, 1981
(as amended).
The legislation makes it illegal to:
•
Intentionally kill, injure or capture (take) bats;
•
Possess or control any live or dead specimens or anything derived from a bat;
•
Intentionally or recklessly disturb bats; and
•
Intentionally or recklessly damage, destroy or obstruct access to bat roosts.
In this sense a bat roost has been interpreted to mean any structure or place which is used for shelter
or protection whether or not bats are present at the time.
There are some exceptions to the provisions listed above. Licences permit otherwise potentially
unlawful activities and are granted for certain purposes by Natural England for scientific, education
or conservation purposes (including survey). Licences may also be issued for the purposes of
“preserving public health or safety or other imperative reasons of overriding public interest
including those of a social or economic nature and beneficial consequences of primary importance
for the environment” (Regulation 44(2)(e) of the Habitats Regulations). This being said, it still
makes it very difficult for bats to be captured or killed for scientific purposes and therefore ERICA
cannot model bats to the same accuracy as other species due to this lack of public information. Bats
would be ideally modelled as terrestrial mammals under the species of “Bird or flying insect”
however the mass range allowed for external exposure of birds in the BIOTA_DCC tool is 35 g to a
15
maximum of 2 kg, therefore the bats are all too small. Average weights for bat species are shown in
Table 22. The dimensions and weights for the Pipistrelle bat were used in the calculations as this is
the most common bat species in the Sellafield area. Bats were modelled as terrestrial mammals:
“Ground-living animal” as the mass range allowed for terrestrial animals in the BIOTA_DCC tool is
between 0.17 g and 550 kg. Under this species, occupancy factors in-air are disabled in ERICA.
The ERICA manual does suggest that 100% occupancy on soil for a flying animal is conservative. It
is recognised that some species cannot be accurately modelled with the defined weight and
dimension ranges. For instances such as this, it includes a guidance table to assess exposure to
terrestrial biota outside the defined mass ranges shown in Table 3 and illustrated in Figure 4.
Figure 4:
Average bat dimensions
It has been assumed that modelling a bat as a ground living animal would be the worst case scenario
for an animal that spends a proportion of its time roosting near to the ground and some proportion
of its time flying, as ground air concentration level and deposited radioactivity levels would give
rise to higher dose rates than airborne concentration levels. A bat can then also be modelled with its
correct dimensions and weight.
Badgers
Badgers have an average mass of 13 kg. ERICA is limited to modelling in soil organisms with an
upper mass boundary of 6.6 kg. The methodology for assessing exposure to terrestrial biota outside
the defined mass range described above can apply for modelling a badger (using average
dimensions and masses shown in Table 3).
16
Table 3:
“Add new organism” parameters for ERICA
Weight (g)
Length (cm)
Bat Species:
Minimum
Maximum
Minimum
Maximum
Pipistrelle
3
8
3.3
4.8
Myotis
7
21
4.5
5.5
Rhinolophus
5
9
3.5
4.5
Nyctalus noctula 18
40
6
8.8
Eptesicus
15
35
5.8
8
Plecotus auritus
6
12
3.7
5.2
Badger
10000
16000
56
90
Length (cm)
Height (cm)
Width (cm)
hipposideros
serotinus
Final Values to Weight (g)
be
used
in
ERICA
Pipistrelle
7
4.05
1.15
1.15
Badger
13000
73
30
25
The ERICA manual suggests that the researcher should create geometries for each habitat
individually, as the badger will spend some of its time in-soil, and some on-soil and account for the
under-prediction of this smaller in-soil organism. Therefore, an on-soil organism could be created
with the correct mass, and an in-soil organism created with the maximum permissible mass (6.6 kg)
then again, using Table 4 to calculate the deviation from the calculated value and the actual value
for the in-soil organism.
17
Table 4:
Habitat
Guidance to assess exposure to terrestrial biota outside the defined mass ranges
Mass range (kg) General trend
Difference to lower/upper mass limit
External exposure
On soil
< 0.00017
Higher than for m = <2%
0.00017
In soil
> 550
Lower than for m=550 kg
< 10% for m=1000 kg
< 0.00017
Higher than for m = < 2%
0.00017
> 6.6
Lower than for m=6.6 kg
< 30% for m ≈ 25 kg
Above soil < 0.035
Higher than for m = < 2%
(birds)
0.00017
>2
Lower than for m=2 kg
Less than 10% for m ≈ 7 kg
Internal exposure
On soil
< 0.00017
Lower than for m=0.00017 < 40% for 1-MeV-photons for m = 0.0001 kg
kg
< 2% for 0.5-MeV-betas for m = 0.0001 kg
< 1% for alphas
> 550
Higher than for m = 550 < 25% for photons for m = 1000 kg
kg
< 2% for betas
< 1% for alphas < 25%
In soil
< 0.00017
Lower than for m=0.00017 < 40% for 1-MeV-photons for m = 0.0001 kg
kg
< 2% for 0.5-MeV-betas for m = 0.0001 kg
< 1% for alphas
> 6.6
Higher than for m =6.6 kg
< 25% for photons for m = 10 kg
< 2% for betas
< 1% for alphas
Above soil < 0.035
Lower than for m=0.035 < 35% for 1-MeV-photons for m = 0.01 kg
(birds)
kg
< 2% for betas for 1-MeV-photons for m = 0.0001
kg
< 1% for alphas
>2
Higher than for m = 2 kg
< 50% for photons for m = 6.6 kg
< 2% for betas
< 1% for alphas
Badgers were modelled as two separate organisms. One with 100% occupancy on-soil with the
correct mass and one with 100% occupancy in-soil with the reduced mass of 6.6kg. The results for
18
each organism were then halved and the in-soil badger scaled up for its reduced mass using the
scaling factors given in the ERICA manual and presented in Table 23. This correction is not taken
into account in ERICA so the correction was made to the ERICA result and the two final results
combined to create an accurate representation of the badger dose.
RQ BADGER
  in - soil, internal dose
  on - soil, internal dose  
* scaling factor   
 
 
2
2
 
 



  in - soil, external dose   on - soil, external dose  


  






2
2
 






10
all radionuclides
Where “in soil” is the badger modelled with a mass of 6.6kg and spends 100% of it’s time in soil,
and “on soil” is the badger modelled with the correct mass of 13kg and on soil occupancy of 100%.

As there is no difference in Risk Quotients to a badger or bat with the
minimum or maximum values for dimension and weight parameters, the
average was used. The Bat Conservation Trust weight ranges are given in Table
22 for the Pipistrelle but 7 to 8 grams is an accepted average weight (Fujita &
Kunz, 1984) so the lower boundary of this range was used as the average
weight. Heights and weights were estimated from scale drawing and
photographs as no actual information was available for badgers. A diagram
with given measurements was used for the bat dimensions (Greenaway &
Hutson, 1990) shown in Figure 6.

Concentration ratios for each radionuclide for the two species (bats and
badgers) use the default ERICA numbers for Mammal (deer) for badgers and
the numbers for Mammal (rat) for bats.

There is no consideration for external scaling. This is more conservative, as
external dose is lower for a 25kg organism than a 6.6kg organism. Also there is
no information available on the scaling effects for intermediate weights.
19
Determination of habitats and species
Three representative Habitats were selected for the species they are likely to support in the vicinity
of the power station site.

Habitat 1 lies next to the Sellafield site, in the surrounding fields.

Habitat 2 comprises the coastal area adjacent to the site.

Habitat 3 is a small lake.
These habitat locations are shown in Figure 5.
Figure 5:
Map of the locations of the three habitats.
As the majority of marine biota is mobile, assessing the activity concentration at a single receptor point has
little value, particularly given the highly dynamic nature of the tides, currents and sediments of the Irish Sea.
By assessing the average activity concentration in a small area of sea around the discharge point, the
radiation exposure over a period of time of any biota present is more likely to be determined The local
compartment as defined in PC CREAM for Sellafield, in a more in depth study, would be used for this
purpose to determine concentrations in seawater and seabed sediments. Also, in a more in depth study,
meteorological data for the area could be used to calculate at specific bearings and distances the
concentration in soil and air of gaseous discharged radionuclides.
20
Detemining Habitats
Habitats should include the three ecosystems included in ERICA for full scope of assessment:

Terrestrial

Marine

Freshwater
Habitat 1: Terrestrial
For the terrestrial habitat, a large number of species were found to reside in this area. This habitat is
the main receptor habitat for atmospheric discharge impacts.
Habitat 2: Marine
The marine environment encompasses the coast line adjacent to the Sellafield site and the Irish Sea.
A large number of species have been reported to reside here and this would be the area most
influenced by any liquid discharge.
Habitat 3: Freshwater
The freshwater habitat is a nearby lake. As a number freshwater organisms were identified in the
Sellafield area, it is sensible to assume that some if not all would reside or visit this area and
therefore be potentially exposed to radionuclides in the runoff from the watershed area of the river.
The SRS 19 approach for modelling discharges into the environment was used to calculate dose
rates and risk quotients in ERICA.
21
Data Used
In order to carry out an assessment of impacts on non-human species, it is necessary to determine
the activity concentration of discharged nuclides in water and soil.
Annual gaseous and liquid discharges the Sellafield site are presented in Table 5 and 6 respectively.
Discharges presented are the annual maximum or authorised limit discharges. Sellafield data are
based on the most recent RIFE report, (RIFE, 2008).
Table 5:
Annual gaseous discharge limits
Discharge limit
Radioactivity
(annual
Discharges
equivalent)
2007
during
% of annual
TBq
TBq
limit
Alpha
8.80 10-4
1.39 10-4
16.0
Beta
0.042
0.00207
4.9
Tritium
1100
82.9
7.5
Carbon-14
3.3
0.36
11.0
Krypton-85
4.40 10+05
1.41 10+04
3.2
Strontium-90
7.10 10-4
3.64 10-5
5.1
Ruthenium-106
0.028
0.00131
4.7
Antimony-125
0.0023
7.07 10-4
31.0
Iodine-129
0.07
0.00482
6.9
Iodine-131
0.055
5.65 10-4
1.0
Caesium-137
0.0058
1.73 10-4
3.0
Plutonium alpha
1.90 10-4
2.72 10-5
14.0
Plutonium-241
0.003
2.79 10-4
9.3
1.20 10-4
2.10 10-5
18.0
Americium-241 and curium242
22
Table 6:
Annual liquid discharge limits
Discharge limit
Radioactivity
(annual
Discharges
equivalent)
2007
during
% of annual
TBq
TBq
limit
Alpha
10
1.25 10-1
13.0
Beta
220
24.8
11.0
Tritium
2.00 10-04
628
3.1
Carbon-14
21
4.65
22.0
Cobalt-60
36
5.00 10-2
1.4
Strontium-90
4.80 10+1
50
10.0
95
3.8
0.12
3.2
Technetium-99
10
48.9
4.9
Ruthenium-106
63
1.49
2.4
Iodine-129
2
1.04 10-1
5.2
Caesium-134
1.6
1.37 10-1
8.6
Caesium-137
34
69.8
21.0
Cerium-144
4
4.19 10-1
10.0
Neptunium-237
1
3.80 10-2
3.8
Plutonium alpha
7.00 10-1
1.05 10-1
15.0
Plutonium-241
25
28.3
11.0
Americium-241
3.00 10-1
2.24 10-2
7.5
Curium-243 and 244
0.069
3.11 10-3
4.5
Uranium
2.00 10+3
3.02 10+2
15.0
Zirconium-95 and Niobium-
In a more comprehensive assessment, a modelling programme like PC CREAM would be used to
calculate radionuclide concentrations at specific coordinates taking into account site specific
conditions. For the purpose of this assessment, radionuclide concentrations will be approximated
from RIFE. These media concentrations are presented below. Please not that these concentrations
are only an estimation of levels found. Further study should include the relevant computer
modelling by PC CREAM; these values are for example only.
23
Table 7Habitat 1. Air and soil concentrations resulting from terrestrial discharges from Sellafield
Air
Soil
Concentration
Concentration
Bq m-3
Bq kg-1
H3
6.1 10-01
-
C14
1.6 10-01
-
S35
6.5 10-03
2.0 10-01
Ar41
1.9 10-00
-
Co58
3.6 10-06
8.8 10-05
Co60
2.7 10-05
1.5 10-02
Kr85
3.7 10-01
-
I131
4.8 10-05
1.1 10-03
I133
2.6 10-05
6.3 10-05
Xe131m
8.0 10-03
-
Xe133
1.7 10+00
-
Xe135
5.3 10-01
-
Cs134
3.3 10-06
7.6 10-04
Cs137
3.0 10-06
5.9 10-03
24
Table 8:
Habitat 2. Seawater and seabed sediment concentrations resulting from marine
discharges from HPC
Activity
Activity concentrations
concentrations in in
unfiltered
seabed
(Bq kg-1)
Nuclide
seawater (Bq l-1)
H3
8.38 10+00
5.69 10+00
C14
2.00 10-03
1.19 10-01
S35
1.78 10-02
4.82 10-03
Mn54
5.34 10-06
4.03 10-05
Ni63
2.01 10-05
3.60 10-03
Cr51
8.28 10-07
5.28 10-07
Co60
1.65 10-04
6.83 10-03
Co58
3.56 10-05
6.20 10-05
Ag110m
1.12 10-05
1.17 10-05
Sb124
8.21 10-06
2.10 10-06
Sb125
1.68 10-05
6.60 10-05
Te125m* 1.05 10-06
6.55 10-05
Te123m
4.81 10-06
2.44 10-06
Te123 *
2.16 10-20
5.86 10-18
Cs134
8.00 10-03
5.39 10-02
Cs137
1.15 10-02
5.75 10-01
I131
3.89 10-07
4.46 10-09
25
sediments
Table 9:
Calculations for freshwater Habitat 3
Release Rate,
Radioactive Approximate
Deposition
Air
Velocity
Concentration
Deposition
Rate,
Discharge
D Rate,
Decay
radionuclide
Qi Constant, λi concentration,
HPC
[Bq m-3]
[m s-1]
[Bq s-1]
[Bq s-1]
[s-1]
Cw [Bq m-3]
H3
2.70 10-01
5.00 10-03
1.35 10-03
1.82 10+00
1.78 10-09
2.28 10+06
C14
6.30 10-02
0.00 10+00
0.00 10+00
0.00 10+00
3.83 10-12
0.00 10+00
Ar41
5.80 10-02
0.00 10+00
0.00 10+00
0.00 10+00
1.05 10-04
0.00 10+00
Co58
2.80 10-06
1.00 10-03
2.80 10-09
3.78 10-06
1.13 10-07
7.41 10-02
Co60
3.30 10-06
1.00 10-03
3.30 10-09
4.46 10-06
4.17 10-09
2.38 10+00
Kr85
2.80 10-01
0.00 10+00
0.00 10+00
0.00 10+00
2.05 10-09
0.00 10+00
I131
1.60 10-05
1.00 10-02
1.60 10-07
2.16 10-04
9.98 10-07
4.81 10-01
I133
1.90 10-05
1.00 10-02
1.90 10-07
2.57 10-04
9.26 10-06
6.16 10-02
Xe131m 6.10 10-03
0.00 10+00
0.00 10+00
0.00 10+00
6.74 10-07
0.00 10+00
Xe133
1.30 10+00
0.00 10+00
0.00 10+00
0.00 10+00
1.53 10-06
0.00 10+00
Xe135
4.00 10-01
0.00 10+00
0.00 10+00
0.00 10+00
2.12 10-05
0.00 10+00
Cs134
2.50 10-06
1.00 10-03
2.50 10-09
3.38 10-06
1.07 10-08
7.04 10-01
Cs137
2.30 10-06
1.00 10-03
2.30 10-09
3.11 10-06
7.32 10-10
9.43 10+00
26
Methodology for ERICA and R&D 128 Dose Assessments
As it is not possible to add nuclides or organisms at Tier 1, a Tier 2 assessment has been completed
in order to produce dose to organism results for all relevant radionuclides. All radionuclides
discharged have been considered in ERICA with the exception of noble gases. Noble gases will not
deposit onto the ground. Doses to non-human species from noble gases cannot be assessed in
ERICA; these were calculated using R&D128.
R&D128 calculates doses to non-human species from the noble gases Ar-41 and Kr-85, these were
used together with the ERICA RQ calculations described above to determine the risk quotients for
these radionuclides. R&D128 does not model xenon radionuclides. As it is not possible to add
additional radionuclides argon was used as an analogue. This is because argon has higher gamma
and beta energies than Kr and Xe, making a conservative estimate of dose for each of the Xe
isotopes. Xenon radionuclides are modelled together as Ar-41 by entering total xenon discharge
rate as an input to the R&D128 spreadsheet rather than individual isotopes as this would not give
any differentiation between isotopes.
The non-human species in R&D128 are not identical to those in ERICA. Therefore it is not possible
to simply sum the results from the two codes for a given habitat assessment, the results are
presented individually in Section 3.
All species found in the assessment area were tabulated and matched, if possible, with an equivalent
reference organism in ERICA. Specific habitats were chosen to cover all of the observed species
and the different compartments (marine, terrestrial, etc) in the area. Estimations of activity
concentrations in air, soil and water were made, and then these values were entered into ERICA to
determine the impact of individual radionuclides to non-human species. Any high risk radionuclide
doses would be highlighted in the traffic light colour scheme previously mentioned: red for concern,
yellow for potential concern and green for negligible concern.
The sequence of events required for an ERICA assessment is shown in Figure 6.
27
Figure 6:
Flowchart of the operation of an ERICA assessment
It was necessary to run ERICA several times for each of the habitat locations
This Tier 2 assessment is recommended by the Environment Agency to ensure adherence to current
guidance and best practices.
Use of ERICA for completing non-human species dose assessments is relatively new in the UK.
ERICA can only assess routine continuous discharges so the assessment has not considered faults or
accidents in the EIA nor have doses from planned short term discharges been assessed. However, as
this assessment calculates impact following a 60 year continuous discharge, this should \ultimately
give a higher dose than a single planned short term discharge.
28
Freshwater ecosystem modelling within ERICA
Freshwater organisms observed in the area included water voles, several species of birds,
amphibians and a number of freshwater invertebrate (Trichoptera, Oligochuato, Mollusca,
Crustacea, Diptera, Coleoptera, Nematoda and Ptychopterid larvae). For completeness, in the
ERICA assessment, all default organisms were included.
ERICA models radionuclide transport in freshwater in ecosystems using a box type model and
references IAEA report SRS-19 for derivation and assumptions used in this model. ERICA requires
release rates (Qi) inputs and lake data, and then calculates approximate radionuclide concentration
(Cw) for a station life of 60 years. Inputs needed for the ERICA run are presented in Table 16.
The calculations displayed in Table 9 for Cw can be used as a comparison and validation of the
ERICA method, but it is necessary to remember that the excel calculations for C w displayed in these
tables were rudimentary and ERICA takes into account the station discharge period of 60 years.
Freshwater methodology
Observed in the area was a small still water pond.
IAEA report SRS-19 classifies lakes and reservoirs into two types. The pond considered has
dimensions of approximately 30m lengthways and 15m in width, with a depth of around 1m. This
puts it into the type of “small lakes and reservoirs” (a surface area of less than 400 km2).
Lake area
= 30 m * 15 m
= 450 m2
As the pond is a body of still water, there is no need to consider any river inflow or outflow. It is
necessary; however, to consider the watershed area for contributions such as runoff, surface soil
erosion and groundwater seepage. The watershed area is assumed to be 100 times the lake surface
area (therefore equal to 45000 m2), and supposes that 2% of deposited radionuclides on the
watershed reach the lake via runoff, surface soil erosion and groundwater seepage (SRS 19).
To calculate the combined radionuclide release rate Q’ (Bq s-1), SRS-19 states the following formula
to be used:
Q'i  Qi 
29
3dAl
86400
Where:
Qi
=the annual average rate of radionuclide discharged directly into the lake
d
=the deposition rate from the atmosphere (Bq m-2 d-1)
Al
=the surface area of the lake
Qi can be ignored in this scenario as there is no direct discharge into the lake.
So, taking the air concentrations from PLUME, and the deposition velocities for each radionuclide,
a deposition rate, D, can be calculated in the units Bq m-2 s-1.
This results in the following equation for this pond:
Q'i  3DAl
Where:
=the deposition rate from the atmosphere (Bq m-2 s-1)
D
From this, the pond water radionuclide concentration, C w (Bq m-3) can be calculated using the
following formula (SRS 19):
Cw 
Q'i
qr  iV
Where:
qr
=the 30 year low annual river flow rate (m s-1)
λi
=the radionuclide decay constant (s-1)
V
=the lake volume (m3)
Again, qr can be ignored for this scenario, resulting in Cw being given by:
Cw 
Q'i
iV
Calculations for Qi and Cw are displayed in Tables 17 to 20. λi values were taken from ICRP 38.
30
Results and Discussion
Habitat 1
For the Sellafield site, the risk quotients and dose for atmospheric releases to the terrestrial
environment on terrestrial organisms are presented in Table 10 for each of the default ERICA
organisms and the additional custom organisms, badgers and bat based on a screening value of 10
µGy h-1. The maximum risk quotient was 8.06 10-4 for badgers. The associated dose for these
organisms is 8.06 10-3 µGy h-1
Doses and RQs for discharges of noble gases from HPB are presented in Table 11. For habitat 1,
Caterpillars have the highest total dose of 2.70 10-3 μGy h-1.
Table 10:
ERICA Results for Habitat 1
Total Dose Rate per organism
Organism
Risk Quotient [unitless]
[μGy h-1]
Amphibian
7.01 10-04
7.01 10-03
Bird
7.23 10-04
7.23 10-03
Bird egg
4.94 10-04
4.94 10-03
Detritivorous invertebrate
2.78 10-04
2.78 10-03
Flying insects
2.72 10-04
2.72 10-03
Gastropod
2.77 10-04
2.77 10-03
Grasses & Herbs
4.93 10-04
4.93 10-03
Lichen & bryophytes
4.93 10-04
4.93 10-03
Mammal (Deer)
7.24 10-04
7.24 10-03
Mammal (Rat)
7.25 10-04
7.25 10-03
Reptile
7.23 10-04
7.23 10-03
Shrub
4.93 10-04
4.93 10-03
Soil Invertebrate (worm)
2.78 10-04
2.78 10-03
Tree
7.05 10-04
7.05 10-03
badger in
7.17 10-04
7.17 10-03
badger on
7.16 10-04
7.16 10-03
Badger
8.06 10-04
8.06 10-03
Bat
7.14 10-04
7.14 10-03
31
Table 11:
Habitat 1. R&D128 results for Sellafield Site noble gas discharges (μGy h-1)
ALL
Bacteria
Ar
1.90 10-07 6.40 10-04 6.90 10-04 6.90 10-04 6.90 10-04 7.40 10-04 7.90 10-04 1.20 10-03
4.70 10-04
Kr
5.40 10-09 3.20 10-06 7.10 10-06 7.10 10-06 7.10 10-06 1.20 10-05 2.20 10-05 4.40 10-06
3.90 10-06
Xe
2.30 10-07 7.60 10-04 8.30 10-04 8.30 10-04 8.30 10-04 8.80 10-04 9.40 10-04 1.50 10-03
5.60 10-04
Total 4.25 10-07 1.40 10-03 1.53 10-03 1.53 10-03 1.53 10-03 1.63 10-03 1.75 10-03 2.70 10-03
1.03 10-03
4.25 10-08 1.40 10-04 1.53 10-04 1.53 10-04 1.53 10-04 1.63 10-04 1.75 10-04 2.70 10-04
1.03 10-04
RQ
Lichen
Tree
Shrub
Herb
Seed
Earth
Herb.
Car.
worm
Mammal
Mammal
6.40 10-04
1.50 10-07
2.50 10-04
2.50 10-06
3.70 10-06
5.10 10-10
Xe
1.40 10-03
7.70 10-04
Total
2.50 10-03
RQ
2.50 10-04
ALL
Bee
Woodlouse
Ar
1.10 10-03
Kr
32
Fungi
Caterpillar Ant
Rodent
Bird
Bird egg
Reptile
2.90 10-04
2.30 10-04
7.80 10-04
5.80 10-04
3.20 10-04
1.40 10-07
1.50 10-07
3.30 10-07
4.10 10-07
7.50 10-07
2.40 10-07
1.80 10-07
3.00 10-04
3.50 10-04
2.80 10-04
9.30 10-04
6.90 10-04
3.80 10-04
1.41 10-03
3.31 10-07
5.50 10-04
6.40 10-04
5.10 10-04
1.71 10-03
1.27 10-03
7.00 10-04
1.41 10-04
3.31 10-08
5.50 10-05
6.40 10-05
5.10 10-05
1.71 10-04
1.27 10-04
7.00 10-05
Habitat 2
For the Sellafield site, the risk quotients and dose for liquid releases to the marine environment on
marine organisms are presented in Table 12 for each of the default ERICA organisms based on a
screening value of 10 µGy h-1. The maximum risk quotient was 5.20 10-4 for reptiles. The
associated dose for these organisms is 5.20 10-3 μGy h-1.
Table 12:
ERICA results for Habitat 2
Total
Dose
Organism
Risk Quotient [unitless]
(Wading) bird
2.99 10-04
2.99 10-03
Benthic fish
1.36 10-04
1.36 10-03
Benthic mollusc
1.08 10-04
1.08 10-03
Crustacean
1.04 10-04
1.04 10-03
Macroalgae
9.63 10-05
9.63 10-04
Mammal
3.17 10-04
3.17 10-03
Pelagic fish
1.30 10-04
1.30 10-03
Phytoplankton
4.72 10-06
4.72 10-05
Polychaete worm
1.50 10-04
1.50 10-03
Reptile
5.20 10-04
5.20 10-03
Sea anemones or true corals - colony
2.26 10-04
2.26 10-03
Sea anemones or true corals - polyp
1.75 10-04
1.75 10-03
Vascular plant
7.63 10-05
7.63 10-04
Zooplankton
9.40 10-05
9.40 10-04
33
Rate
organism [μGy h-1]
per
Habitat 3
For the Sellafield Site, the risk quotients and dose for freshwater organisms are presented in Table
13 below for each of the default ERICA organisms based on a screening value of 10 µGy h -1. The
maximum risk quotient was 2.97 10-1 for insect larvae. The associated dose for these organisms is
2.97 μGy h-1. The total dose for all ERICA freshwater organisms is presented in Table 77.
Organisms common to both Habitat 1 and Habitat 4 include amphibians, birds, gastropods and
mammals. Their total dose from atmospheric and freshwater exposures is
5.49 10-2 μGy h-1, 5.03 10-2 μGy h-1, 1.48 μGy h-1 and 6.22 10-2 μGy h-1 respectively. This dose does
not include the dose from noble gases.
Table 13:
ERICA results for Habitat 3
Total Dose Rate per organism
Organism
Risk Quotient [unitless]
[μGy h-1]
Amphibian
4.78 10-03
4.78 10-02
Benthic fish
1.37 10-01
1.37 10+00
Bird
4.31 10-03
4.31 10-02
Bivalve mollusc
1.46 10-01
1.46 10+00
Crustacean
1.50 10-01
1.50 10+00
Gastropod
1.48 10-01
1.48 10+00
Insect larvae
2.97 10-01
2.97 10+00
Mammal
5.49 10-03
5.49 10-02
Pelagic fish
4.85 10-03
4.85 10-02
Phytoplankton
1.36 10-03
1.36 10-02
Vascular plant
1.50 10-01
1.50 10+00
Zooplankton
3.47 10-03
3.47 10-02
34
Discussion
From this point you may discuss the results in detail and in particular, make cross reference to
external peer review literature and statements in the context of the original study aim.
All doses to non-human species are below the ERICA screening value of 10 µGyh-1 and are well
below the EA biota dose limits:
 terrestrial animal populations at chronic dose rates below 40 µGy h-1;
 terrestrial plant populations at chronic dose rates below 400 µGy h-1;
 populations of freshwater and coastal organisms at chronic dose rates below 400 µGy h-1;
All doses calculated in R&D128 were below the EA guidelines. Furthermore, they do not exceed
the 30% of the EA guidelines benchmark that R&D128 sets as the point above which further action
should be considered.
Habitat contains an SSSI and therefore of interest to regulators. It is also the habitat for bats and
therefore special protection of the bats and their roosts must be considered. All the estimated doses
from the Sellafield discharges are below the most stringent assessment level (10 µGy h-1).
Therefore the radiological impacts for non-human species from Sellafield are considered as
negligible.
Habitat 2, as part of Bridgwater Bay, is a designated site and therefore of interest to regulators. All
the estimated doses from the HPC discharges are below the most stringent assessment level (10
µGy h-1).
Therefore the radiological impacts for non human species from Sellafield marine
discharges are considered as negligible.
Habitat 4 is not an SSSI or other designated site and all the estimated doses from the HPC
discharges are below the most stringent assessment level (10 µGy h-1). Therefore the radiological
impacts for non human species from Sellafield are considered as negligible.
Uncertainties
The 95th percentile of the risk quotient is estimated by multiplying the expected value of the risk
quotient by an uncertainty factor (UF=3 in the ERICA tool). It tests for a 5% probability of
exceeding the dose screening value, assuming exponential distribution of values.
Annex A of the D-ERICA report describes the uncertainties in ERICA and practical options for
35
dealing with uncertainties and data gaps.
The pond dimensions have been estimated from an aerial view. Pond depth was taken to be one
meter but it may be deeper in some places as no measurement of pond depth has been carried out. A
shallower pond would result in higher concentrations in the water and sediments and would
therefore result in higher doses. Conversely, a deeper, broader or longer pond would result in lower
concentrations in both water and pond sediments and therefore lower doses to organisms.
Badgers have the highest Habitat 1 dose, but as they are a special additional species, the additional
dose could be through the use of the scaling table.
36
Conclusions
Doses to non-human species are well below the 10 µGy h-1 screening value for all default organisms
and discharges for Sellafield site discharges. The maximum risk quotient is 2.97 10-1 to mammals
from atmospheric discharges.
The greatest dose impact to all non-human species from all atmospheric discharges is from C-14.
C-14 is the dominant radionuclide for dose to many of the ERICA marine organisms. Co-60 is the
dominant radionuclide for dose to many of the ERICA freshwater organisms. Cs-137, Cs-134 and
H-3 give the highest doses for some organisms. All doses to non-human species are below the
ERICA screening value of 10 µGyh-1 and well below the EA biota dose limits.
Based on this information, doses to non-human species in the vicinity of the Sellafield power
station can be considered negligible and the risk to habitats and species will be very low.
37
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