Introduction to Health Physics: Fourth Edition - Ruang Baca FMIPA UB

RADIATION SAFETY GUIDES 387
REGION FRACTION DEPOSITED
ET1
0.34
ET2
0.40
BB 0.018
bb 0.011
AI 0.053
Table 8-15 (17-B, ICRP 66) gives the size-dependent partition of a regional deposit
into the several regional compartments. For the BB region, the slowest cleared fraction
of the bronchial deposit is called BBseq, and is listed as 0.007. The next morerapidly
cleared fraction is listed as fs, and fastest cleared fraction is given 0.993 − fs.
The value for fs is size dependent, and is given by the following relations:
0.5 ρ
for dae ≤ 2.5 μm, fs = 0.5,
χ
0.5
ρ
χ
for dae > 2.5 μm, fs = 0.5 exp −0.63 dae − 2.5 .
χ
ρ
For the case of WC we have: 2.5(15.6/1.5) 0.5 = 8.1. Since dae = 5 μm < 8.1, therefore,
fs = 0.5. Using this value for fs, we can calculate the activity deposited in each
of the regional compartments:
The MRT in each compartment is given by
MRT = 1
, (8.31)
λE
where λE = effective clearance rate constant = λab + Ss + λR.
For very long lived insoluble activity, λR ≈ 0, therefore,
λE = (λab + 0.0001) per day.
TABLE 8-15. Compartmental Distribution of Deposited Activity
REGIONAL COMPARTMENTAL DEPOSITED
FRACTIONAL FRACTIONAL ACTIVITY
REGION DEPOSIT COMPARTMENT DEPOSIT (Bq)
ET1 0.34 ET1 1 0.34
ET2 0.40 ET2 0.9995 0.3998
ETseq 0.0005 0.0002
BB 0.018 BB1 0.993 − 0.5 = 0.493 0.22887
BB2 0.5 0.0090
BBseq 0.007 0.00013
bb 0.011 bb1 0.993 − 0.5 = 0.493 0.00542
bb2 0.5 0.0055
bbseq 0.007 0.000077
AI 0.053 AI1 0.3 0.0159
AI2 0.6 0.0318
AI3 0.1 0.0053
ET, extrathoracic; BB, bronchial; bb, bronchiolar; AI, alveolar-interstitial.