Gd-148 is a radioactive isotope that decays by alpha emission. Each alpha partic
ID: 516949 • Letter: G
Question
Gd-148 is a radioactive isotope that decays by alpha emission. Each alpha particle emitted carries 5.10E-13 J of kinetic energy. A 80.0 kg worker is accidentally exposed to a sample of Gd-148 having an activity of 0.0200 curies for a total of 10.00 minutes. During that time the workers body absorbs 10.00 percent of the alpha particles emitted by the sample.
How many alpha particles were emitted by the sample during the time of the workers exposure?
How many joules of energy were absorbed by the worker?
The alpha particles emitted by the sample have an RBE=20. Calculate the workers exposure in millirems.
Explanation / Answer
1 curie = 3.7 xe10 disintegration /second
No of particles emit for 10 minutes = 0.02 x 3.7 xe10 x (10 x60) = 44.4 xe10
No of particles absorbed by worker = 10 % of 12 = .10 x 44.4xe10 = 4.44xe10
Energy absorbed by the worker = 4.44xe10 x 5.10e-13 = 22.644e-3 J
rad = 22.644e-3 /80 = 0.28305e-3 J/kg = 2.8305 erg/g
worker exposure = 2.8305 x 20 x 1000= 56610 milirem
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