INHALATION
Exhaled 25%
UPPER
RESPIRATORY
INGESTION
dy, /dt = faxéR - Or, + Ay
(39)
Sypone’*t = fpay’p ~ Oy * >p)¥pone
(40)
dypp/dt = Epogty - Og + Ang) ¥pp
(41)
where
TRACT
tar Topp are the rates that plutonium reaches the blood and
gastrointestinal tract (GIT), respectively (uCi/day),
AH, are the plutonium inhalation and ingestion rates,
I
GASTROINTESTINAL
TRACT
(18 hours
transit)
UL dey
|
Transit)
|
|
{
BLOOD
|
1
|
l
SLOW
(365 days)
I
|
I
1
*
**
LIVER
KIDNEY
BONE
30,000 days
32,000 days
(73,000 dayq)
Soluble Compounds
Insoluble Compounds
DEEP
|
LUNG
'
,y,oLvnwitwTe J
respectively (uci /day) ,
f is the fraction of plutonium transferred from one
location to another within the body with the subscript notation as follows: URG is upper respiratory tract (URT) to GIT; URB is URT to blood;
GITB is GIT to blood; URDLF and URDLS are URT to
the fast and slow portions, respectively, of the
deep lung; BL, BK, BBN, and BIB are blood to liver,
kidney, bone and total body, respectively. T
,
T
are transit times for the fast portion ofEne
deep lung and the GIT (lower large intestine), respectively.
>
nino
is the biological elimination rate constant with
the subscript notation as follows: DLS is deep
lung (slow portion), TB is total body, L is liver,
K is kidney, and B is bone (day~1),
\ = In(2)/1 where 1 is the biological half-time for the
organ,
days.
y is the plutonium burden in the organ with the subscript notation either self evident or identical to
that for \} except BDLF is the fast portion of the deep
Jung and DL is the total deep lung (uCi).
Fraction From Bloom to Total Body is 100%
Biological Half-Time in Total Body is 65,000 days.
Values of the parameters in Equations (33) through (41) can be obtained from
Figure 3 for plutonium. The values for other transuranic elements, if different from plutonium, are given in Table 8. Radioactive half-times for each
transuranic nuclide are given in Table 7.
Task Group on Lung Dynamics Model
FIGURE 3,
ICRP COMMITTEE IT MODEL FOR PLUTONIUM
662
The ICRP Task Group on Lung Dynamics (Morrow et al., 1966) provided a more
detailed description of the inhalation pathway and arrived at the model indicated in Figure 4. A subsequent report (ICRP 19, 1972) provided specific data
for applying this mode! to plutonium and other transuranics.
The Task Group
model treats the respiratory tract as a series of compartments in which the
amount initially deposited depends on the particle size and the clearance rate
(biological half-time) depends on the type of compound.
663