Appendix CRF - Part 3 - Northamptonshire County Council

Radiological Assessment 0820-2
Version 2
Kd is the distribution coefficient for radionuclide Rn in the rock
(m 3 kg -1 ).
gw is the bulk density of the rock for the groundwater pathway (kg m -3 ).
The change in concentration of radionuclides in soil, CRn,soil (Bq kg -1 ), that is irrigated
with contaminated water is given by:
dC
Rn,
soil
dt
Irrig rate
CRn,
water ( t)
eff C
Rn,
soil d
soil
where CRn,water(t) is the concentration of radionuclide in the water used for irrigation at
time t (Bq m -3 ).
Irrigrate is the rate of irrigation (m year -1 ).
dsoil is the depth of the soil layer being irrigated (m).
soil is the density of the soil (kg m -3 ).
eff is an effective decay coefficient that considers radioactive decay,
leaching from the soil, uptake by plants, and erosion (year -1 ), given
by:
eff Rn
Ptotal
AE runoff TFplant
Yield
plant
Rn
Rn
erosion
d soil soil soil K d soil soil d
,
soil
where Ptotal is the total precipitation (m year -1 ).
AE is the amount of precipitation that is lost by evapotranspiration
(m year -1 ).
runoff is the amount of precipitation lost by runoff (m year -1 ).
Yieldplant is the plant yield (kg m -2 year -1 ).
TFplant is the soil to plant transfer factor for radionuclide, Rn (Bq kg -1 fresh
weight of crop per Bq kg -1 of soil).
dsoil is the depth of the soil layer being irrigated (m).
soil is the bulk density of the soil (kg m -3 ).
soil is the porosity of the soil (dimensionless).
is the degree of saturation (dimensionless).
Kd,soil is the distribution coefficient for radionuclide Rn in the soil (m 3 kg -1 ).
Rn is the decay constant of radionuclide Rn (year -1 ).
erosion is the loss of radioactivity owing to erosion of the soil (year -1 ).
The removal of activity from the groundwater through the irrigation process is not
tracked.
Dose calculations for the groundwater pathway are described in Appendix A. Decay
constants and other radionuclide-specific parameter values are presented in Appendix
B. Other parameter values used in the calculations of specific doses for the ENRMF
are listed in Table 4.6.
Galson Sciences Limited 39 14 July 2009
WS010001/ENRMF/CONSAPPCRF 589
soil
( t)