Appendix CRF - Part 3 - Northamptonshire County Council

Radiological Assessment 0820-2
Version 2
Parameter Description Value Unit
Irrigrate rate of irrigation 0.3 m year -1
dsoil depth of the soil layer being irrigated 1.0 m
soil density of the soil 1300 kg m -3
Yieldplant plant yield
Pasture 1.7
kg m
Grain 0.4
Green veg 3.0
Root veg 3.5
-2 year -1
soil porosity of the soil 0.3 dimensionless
degree of saturation 0.5 dimensionless
erosion
loss of radioactivity owing to erosion
of the soil
2.0x10 -4
year -1
Table 4.6 Parameter values used in the calculation of radionuclide concentrations
in groundwater used for irrigation and in irrigated soil.
4.3 Other scenarios and pathways
4.3.1 Gas
The gas pathway has been considered only for tritium and radon. It is not envisaged
that there would be sufficient organic waste material in the LLW to generate
radiogenic CO2 or CH4. Potentially exposed groups for the gas pathway are site
workers, members of the public spending time immediately downwind of the site
during the operational period, and members of the public living in a house built on the
site after closure.
Radioactive Gas Release
For H-3 (in hydrogen, water, or methane) and C-14 (in carbon dioxide or methane),
the release rate of radioactive gas, RRn,gas (Bq year -1 ), at time t (years) is given by:
R
Rn,
gas
( t)
A
Rn,
waste
where: ARn,waste is the initial activity of radionuclide Rn in the waste (Bq).
Rn is the decay constant of radionuclide Rn (year -1 ).
fgas is the fraction of the activity associated with each gas
(dimensionless).
gas is the average timescale of generation of each gas (years).
Galson Sciences Limited 40 14 July 2009
e
Rnt
For radon (Rn-222), the release rate at time t is given by:
Ra
226t
R ( t)
a C e
H
radon
Rn222
Ra-226,
waste
where: is the decay constant of the indicated radionuclide(year –1 ).
a is the surface area of the disposal unit (m 2 ).
CRa-226,waste is the initial Ra-226 concentration in the waste (Bq kg –1 ).
gas
f
gas
waste
WS010001/ENRMF/CONSAPPCRF 590
1
e
-h
H
2
2