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Chapter 42: Q.48 (page 1237)
A 1 Ci source of radiation is a significant source. 238 U is an alpha emitter. What mass of 238 U has an activity of 1 Ci?
the mass of uranium is 2.96x103kg
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The plutonium isotope 239 Pu has a half-life of 24,000 years and decays by the emission of a 5.2 MeV alpha particle. Plutonium is not especially dangerous if handled because the activity is low and the alpha radiation doesn’t penetrate the skin. However, there are serious health concerns if even the tiniest particles of plutonium are inhaled and lodge deep in the lungs. This could happen following any kind of fire or explosion that disperses plutonium as dust. Let’s determine the level of danger. a. Soot particles are roughly 1 mm in diameter, and it is known that these particles can go deep into the lungs. How many atoms are in a 1.0@mm@diameter particle of 239 Pu? The density of plutonium is 19,800 kg/m3 . b. What is the activity, in Bq, of a 1.0@mm@diameter particle? c. The activity of the particle is very small, but the penetrating power of alpha particles is also very small. The alpha particles are all stopped, and each deposits its energy in a 50@mm@diameter sphere around the particle. What is the dose, in mSv/year, to this small sphere of tissue in the lungs? Assume that the tissue density is that of water. d. Is this exposure likely to be significant? How does it compare to the natural background of radiation exposure?
Use the potential-energy diagram in Figure to estimate the strength of the strong force between two nucleons separated by fm.
A sample of 1.0x1010atoms that decay by alpha emission
has a half-life of 100 min. How many alpha particles are emitted
between t = 50 min and t = 200 min?
What is the age in years of a bone in which the ratio is measured to be?
A 115 mCi radioactive tracer is made in a nuclear reactor. When it is delivered to a hospital 16 hours later its activity is 95 mCi. The lowest usable level of activity is 10 mCi.
a. What is the tracer’s half-life?
b. For how long after delivery is the sample usable?
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