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?
The number of in diameter particles is .
The activity of particle is .
The dose in is .
This is a very high dose to a very small volume of body mass. The exposure to this tissue is much higher than the background level.
The half-life of the is
The radius of soot particles is
The density of Plutonium is
The number of atoms in a diameter particle is
Substitute the given values
Therefore, the number of atoms in diameter particle is .
The activity of the particles is given by
Substitute the given values
Therefore, the activity of diameter particle is .
The volume of diameter sphere of tissue around the particle is
This volume of tissue has a mass of
The number of decays per year is
As each decay creates an particle with energy 5.2 MeV, the total energy received per year by the tissue is
The dose received by the tissue is
The dose per year in mSv is
Therefore, the dose in is .
This is a very high dose to a very small volume of body mass. The background radiation from various natural-occurring sources is about . The exposure to this tissue is much higher than the background level.
Stars are powered by nuclear reactions that fuse hydrogen into helium. The fate of many stars, once most of the hydrogen is used up, is to collapse, under gravitational pull, into a neutron star. The force of gravity becomes so large that protons and electrons are fused into neutrons in the reaction p+ + e- S n + n. The entire star is then a tightly packed ball of neutrons with the density of nuclear matter. a. Suppose the sun collapses into a neutron star. What will its radius be? Give your answer in km. b. The sun’s rotation period is now 27 days. What will its rotation period be after it collapses? Rapidly rotating neutron stars emit pulses of radio waves at the rotation frequency and are known as pulsars
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