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

Solution
Dn,p
=
The dose rate due to the n, p reaction is calculated from Eq. (6.108).
RADIATION DOSIMETRY 269
4 neutrons
10
cm2 atoms
cm2
× 1.49 × 1024 × 1.75 × 10−24
/s kg atom × 0.63 MeV × 1.6 × 10−13 J
MeV
1 J/kg
−9 Gy
= 2.628 × 10
s ,
or, the close rate per hour = 2.628 × 10 −9 Gy/s × 3.6 × 10 3 s/h
˙Dn,p = 9.5 μGy
h
0.95 mrad
.
h
The auto-integral gamma-ray dose rate is calculated with Eq. (6.82). The gammaray
“activity,” from Eq. (6.109) is
4 neutrons
A = 10
cm2 atoms
cm2
× 5.98 × 1025 × 3.3 × 10−25
/s kg atom
5 ′′
Bq′′
= 1.973 × 10
kg .
The dose rate from this uniformly distributed gamma ray emitter is calculated from
Eq. (6.82):
˙Dγ = AS
m
× ϕ × Gy
s .
The absorbed fraction, ϕ, for the 2.23-MeV gamma ray is found, by interpolating
in Table 6-8 between the 2.000 and 4.000 MeV values, to be 0.278, and , the dose
rate in an infinitely large mass whose specific activity is 1 Bq
, is calculated from
kg
Eq. (6.81):
= 1.6 × 10 −13 × 2.23 MeV
γ
Gy
= 3.57 × 10−13 Gy/s
Bq/kg .
The auto-integral gamma-ray dose rate, therefore, is
or
˙Dγ
5 Bq
Gy/s
= 1.973 × 10 × 0.278 × 3.57 × 10−13
kg Bq/kg
−8 Gy
= 1.96 × 10
s
71 μ Gy
h
7.1 mrad
.
h
(1.96 × 10 −6 rad/s)