Chapter 32: Q12CQ (page 1181)
Compare a low dose of radiation to a human with a low dose of radiation used in food treatment.
Low doses of irradiation have been shown to be advantageous to food and humans, as well as the development of good mending mechanisms.
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Breeding plutonium produces energy even before any plutonium is fissioned. (The primary purpose of the four nuclear reactors at Chernobyl was breeding plutonium for weapons. Electrical power was a by-product used by the civilian population.) Calculate the energy produced in each of the reactions listed for plutonium breeding just following Example 32.4. The pertinent masses are \(m\left( {{\rm{ }}239{\rm{ U}}} \right){\rm{ }} = {\rm{ }}239.054289{\rm{ u }},{\rm{ }}m\left( {{\rm{ }}239{\rm{ Np}}} \right){\rm{ }} = {\rm{ }}239.052932{\rm{ u }},{\rm{ and }}m\left( {{\rm{ }}239{\rm{ Pu}}} \right){\rm{ }} = {\rm{ }}239.052157{\rm{ u}}\)
The energy produced by the fusion of a \(1.00 - kg\) mixture of deuterium and tritium was found in Example Calculating Energy and Power from Fusion. Approximately how many kilograms would be required to supply the annual energy use in the United States?
(a) Calculate the energy released in the neutron-induced fission reaction\(n{ + ^{235}}U{ \to ^{92}}Kr{ + ^{142}}Ba + 2n\),
Given \(m{(^{92}}Kr) = 91.926269{\rm{ }}u\) and
\(m{(^{142}}Ba) = 141.916361{\rm{ }}u\).
(b) Confirm that the total number of nucleons and total charge are conserved in this reaction.
Fallout from nuclear weapons tests in the atmosphere is mainly \({}^{{\rm{90}}}{\rm{Sr}}\) and \({}^{137}Cs\) , which have \(28.6\) - and \(32.2y\) half-lives, respectively. Atmospheric tests were terminated in most countries in 1963, although China only did so in 1980. It has been found that environmental activities of these two isotopes are decreasing faster than their half-lives. Why might this be?
(a) Two annihilation \(\gamma \) rays in a PET scan originate at the same point and travel to detectors on either side of the patient. If the point of origin is \({\rm{9}}{\rm{.00\;cm}}\)closer to one of the detectors, what is the difference in arrival times of the photons? (This could be used to give position information, but the time difference is small enough to make it difficult.)
(b) How accurately would you need to be able to measure arrival time differences to get a position resolution of \({\rm{1}}{\rm{.00\;mm}}\)?
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