Appendix CRF - Part 3 - Northamptonshire County Council

Radiological Assessment 0820-2
Version 2
Pu-240 2.28E-02 Phytoplankton 1.09E+03 Lichen & bryophytes
Pu-241 8.47E+01 Phytoplankton 4.05E+06 Lichen & bryophytes
Ra-226 1.40E-02 Vascular plant 2.27E+02 Lichen & bryophytes
Ru-106 1.28E-01 Insect larvae 8.20E+02 Lichen & bryophytes
Sb-125 8.40E-01 Insect larvae 3.73E+04 Detritivorous invertebrate
Sr-90 3.51E+00 Insect larvae 3.76E+02 Reptile
Tc-99 5.05E+01 Vascular plant 2.11E+03 Bird egg
Th-230 3.10E-02 Phytoplankton 1.63E+03 Lichen & bryophytes
Th-232 3.64E-02 Phytoplankton 1.90E+03 Lichen & bryophytes
U-234 4.22E-02 Vascular plant 1.67E+03 Lichen & bryophytes
U-235 4.55E-02 Vascular plant 1.76E+03 Lichen & bryophytes
U-238 4.93E-02 Vascular plant 1.51E+03 Lichen & bryophytes
Table 5.10 Limiting concentrations in freshwater and terrestrial ecosystems, based
on a dose rate of 10 Gy h -1 to the limiting organism or wildlife group.
For the purposes of the wildlife assessment, the modified SNIFFER model described
in Section 4.2 has been used to calculate radionuclide concentrations in a hypothetical
stream close to the site boundary. This stream is assumed to receive baseflow from
groundwater using the same assumptions as used for the drinking water pathway
(Section 5.1). For the terrestrial ecosystem, it is assumed that this stream periodically
floods an adjacent area of land. The SNIFFER model does not explicitly model
flooding, and the irrigation model is therefore used to determine radionuclide
concentrations in soil.
Radionuclide concentrations in the freshwater and terrestrial ecosystems calculated
using the SNIFFER model do not reflect actual concentrations as they are based on
unit disposal (1 MBq) of each radionuclide. To allow comparison with the limiting
concentrations presented in Table 5.10, it is conservatively assumed that the site
receives the maximum amount of each radionuclide that keeps the site below the
radiological capacity (see Section 6.2). Environmental concentrations based on
disposal of radionuclides at capacity are presented in Tables 5.11 and 5.12, together
with calculated risk quotients. The risk quotient for a radionuclide is the highest
value of the ratio between calculated dose rate and the 10 Gy h -1 criterion (i.e., a risk
quotient of 1 or greater would indicate that the screening criterion was exceeded).
Radionulide Soil
concentration
(Bq kg -1 )
Risk
quotient
Am-241 4.92E-03 7.87E-06 Flying insects
Limiting reference organism
C-14 2.22E+00 2.66E-02 Mammal (Deer)
Cl-36 5.28E-02 3.59E-05 Grasses & Herbs
Cm-243 1.60E-13 2.22E-16 Flying insects, Gastropod
Galson Sciences Limited 55 14 July 2009
WS010001/ENRMF/CONSAPPCRF 605