Biomedical Engineering Reference
In-Depth Information
(b)
The exposure rate from the bremsstrahlung emitted by
the stopping beta particles.
A small sample of pure sulfur contains
1.96 × 10
10
Bq of
35
S
embedded in it.
(a)
40.
Estimate the rate of energy emission from the source in
the form of bremsstrahlung.
(b)
Estimate the bremsstrahlung dose rate in air 1 m from
the source.
(c)
What thickness of aluminum would reduce this dose
rate by a factor of 100?
10
11
Bq source of
35
S is contained in aqueous
solution. Assume that the beta particles are stopped by the
water and that self-absorption of bremsstrahlung in the
solution is negligible.
(a)
41.
An
8.51
×
Estimate (for bremsstrahlung shielding purposes) the
dose rate in air due to bremsstrahlung at a distance of
50 cm from the source.
(b)
Estimate the fraction to which this dose rate would be
reduced by a 0.30-cm sheet of tin.
42.
(a)
Estimate the dose-equivalent rate at a distance of 80 cm
from a
210
Po-B point source that emits
2.2
10
7
neutrons s
-1
and is shielded by 30 cm of water.
×
(b)
How thick would the water shield have to be to reduce
the dose-equivalent rate to 0.025 mSv h
-1
?
What is the maximum number of neutrons s
-1
that a
210
Po-Be point source can emit if it is to be stored
behind 65 cm of paraffin and the dose-equivalent rate is
not to exceed 0.10 mSv h
-1
at a distance of 1 m?
43.
(a)
(b)
By what factor would a 31-cm shield reduce the
dose-equivalent rate?
15.8
Answers
Interaction coefficients and attenuation curves in the text can be read only approx-
imately; therefore, answers may not agree precisely with those given here.
1.
6.4 cm
12.
(a)
0.207
61 mR h
-1
2.
0.18
(b)
4.
10.5 cm
14.
(a)
8.1 cm
0.010 mRmin
-1
1.6 mR h
-1
6.
(b)
85 mR h
-1
8.
(a)
18.
(a)
9.0 in.
220 mR h
-1
(b)
(b)
6.0 in.
11.
5.3 cm
19.
4.2 mm
