Biomedical Engineering Reference
In-Depth Information
Fig. 15.15
Small vial containing
32
P in aqueous solution
enclosed in an aluminum can (Problem 37).
weekly workload of 100 mA min for the past 4 y. One of the
law partners has gone bald in the two years since the firm
moved into their present office. Should the dentist fear a law
suit? Explain.
36.
A 30-mL solution containing 7.4
10
10
Bq of
90
Sr in
equilibrium with
90
Y is to be put into a small glass bottle,
which will then be placed in a lead container having walls
1.5 cm thick.
(a)
×
How thick must the walls of the glass bottle be in order
to prevent any beta rays from reaching the lead?
(b)
Estimate the bremsstrahlung dose rate in air at a
distance of 1.75 m from the center of the lead container.
A small vial containing
7.4 × 10
12
Bq of
32
Pinaqueous
solution is enclosed in an 8-mm aluminum can as shown in
Fig. 15.15. Calculate the thickness of lead shielding needed
to reduce the exposure rate to 2.5 mR h
-1
at a distance 2 m
from the can. Treat the vial as a point source and assume
that all of the bremsstrahlung is produced by beta particles
slowing down in the water.
37.
10
9
Bq source of
60
Co is made by neutron activation
of a small piece of cobalt metal (
59
Co, 100% abundant).
(a)
38.
A
1.11
×
Estimate the energy fluence rate of the bremsstrahlung
from the source at a distance of 60 cm. (No shielding is
present, and all beta particles stop in the source itself.)
(b)
Estimate the bremsstrahlung dose rate in air at this
distance. (This will, of course, be much smaller than the
gamma-dose rate from this source.)
39.
60
Co activity can be induced by neutron activation of a
sample of natural cobalt (
59
Co, 100% abundant) in a reactor.
A small 370-MBq source of
60
Co is made in this fashion.
Assume that all of the beta particles emitted are stopped in
the cobalt sample itself and that all photons emitted escape
from it. For a location 1 m from the source in air, estimate:
(a)
The exposure rate from the
60
Co gamma rays.
