Appendix CRF - Part 3 - Northamptonshire County Council

Radiological Assessment 0820-2
Version 2
Rn
Rn
Rn
Doseexcavator Dirr,
slabTC
Rn,
waste ( t)
DinhTBM
inhC
Rn,
waste ( t)
DingTM
ingC
Rn,
waste ( t)
where Minh is the dust load of contaminated waste inhaled by the excavator
(kg m -3 ).
Ming is the rate of ingestion of dust from the material (kg hour -1 ).
T is the time the excavator is exposed to the material (hours year -1 ).
B is the breathing rate (m 3 hour -1 ).
Dirr,slab, Dinh, and Ding are the dose coefficients for radionuclide Rn (Sv hour -1 Bq -1 kg;
Sv Bq -1 ; and Sv Bq -1 , respectively).
CRn,waste(t) is the concentration of radionuclide Rn (Bq kg -1 ) in the excavated
material at the time of excavation, t:
ARn(
t)
CRn,
waste(
t)
V
where ARn(t) is the activity of radionuclide Rn in the landfill at the time of
excavation, t (Bq).
Vlandfill is the volume of landfill in which the activity ARn(t) is
homogeneously distributed (m 3 ).
waste is the density of the waste (kg m -3 ).
The exposure from external irradiation is assumed to come from proximity to
contaminated material, approximated by a semi-infinite slab.
The excavator might also receive a dose through direct contact with contaminated
waste dust on hands and face:
Dose
CRn,
waste ( t)
d
hands
4
10
Galson Sciences Limited 70 14 July 2009
landfill
waste
waste
skin, hands gamma7
beta40
Rn
Rn
Areahands
DDWT skin
Area
where CRn,waste(t) is the concentration of radionuclide Rn (Bq kg -1 ) in the waste at the
time of excavation, t.
Dgamma7 is the skin equivalent dose rate for radionuclide Rn to the basal layer
of the skin epidermis for gamma irradiation (Sv h -1 per Bq cm -2 ).
Dbeta40 is the skin equivalent dose rate for radionuclide Rn to the basal layer
of the skin epidermis for hands for beta irradiation, skin thickness
400 m (40mg cm -2 ), (Sv h -1 per Bq cm -2 ).
10 4 converts Bq m -2 to Bq cm -2 .
dhands is the thickness of the contaminated layer on the hands (m).
waste is the density of the waste (kg m -3 ).
Wskin is the tissue weighting factor for skin (dimensionless).
Areahands is the area of skin in contact with the contaminated dust (cm 2 ).
Areabody is the total exposed skin area of the adult body (cm 2 ).
T is the time the worker is exposed to the material (hours year -1 ).
Dose
C Rn,
waste ( t)
d
face
4
10
waste
skin, face gamma7
beta4
Area
Rn
Rn
face
DDWT skin
Area
where CRn,waste(t) is the concentration of radionuclide Rn (Bq kg -1 ) in the waste at the
time of excavation, t.
WS010001/ENRMF/CONSAPPCRF 620
body
body