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

RADIATION DOSIMETRY 271
6.2. An air ionization chamber whose volume is1Lisused as an environmental monitor
at a temperature of 27◦C and a pressure of 700 torr. What is the exposure rate, in
μC/kg/h and in mR/h, if the saturation current is 10−13 A?
6.3. A beam of 1-MeV gamma rays and another of 0.1-MeV gamma rays each produce
the same ionization density in air. What is the ratio of 1:0.1 MeV photon
flux?
6.4. Assuming that the specific heat of the body is 1 cal/g/ ◦C, calculate the temperature
rise due to a total body dose of 5 Gy.
6.5. Compute the exposure rate, in mGy/h, at a distance of 50 cm from a small vial
containing 10 mL of an aqueous solution of
(a) 2-GBq (54.1-mCi) 51Cr (b) 2-GBq (54.1-mCi) 24Na, based on the transformation schemes shown below:
6.6. What is the soft tissue dose rate during exposure to 25.4 μC/kg/h (100 mR/h) of
0.5-MeV gamma radiation?
6.7. A collimated beam of 0.3-MeV gamma radiation whose energy flux is 5 J/m2 /s is
shielded by 2-cm Pb.
(a) What is the photon flux incident on the shield, in photons cm −2 s −1 ?
(b) What is the exposure rate, mR/h and C/kg/h, in the incident and emergent
beams?
(c) What is the tissue dose rate, mGy/h, in the incident and emergent beams?
6.8. The exposure rate in a beam of 100-keV gamma rays is 25.8 μC/kg (100 mR) per
hour. What is the
(a) photon flux, in photons/cm2 /s?
(b) power density, in W/m2 and mW/cm2 ?
6.9. In an experiment, a 250-g rat is injected with 10-μCi 203 Hg in the form of
Hg(NO3)2. The rat was counted daily in a total-body counter and the following
equation was fitted to the whole-body-counting data
Y = 0.55e −0.346t + 0.45e −0.0346t
where Y is the fraction of the injected dose retained t days after injection. If the
long-lived component of the curve represents clearance from the kidneys while the
short-lived component represents clearance from the rest of the body, calculate
the radiation absorbed dose to the whole body and the kidneys if each kidney
weighs 0.7 g. Assume the mercury to be uniformly distributed in the whole body