Physics

The Size Of The Atmosphere

I have had several discussions where people have said that the atmosphere is so enormous than man could not affect it. When you look up at the sky and think about the size of the Earth it is not difficult to see why they think this. I began to wonder what volume it would take […]

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Nuclear Power – Converting Mass Into Energy?

One of the things that most people know about nuclear power is that it about turning mass into energy – E= mc2. Although this is not wrong it is extremely misleading. First of all I am going to digress a bit. One of the things that makes Einsteins theory of relativity important is that it […]

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Black Holes – Classical Theory

This is just a short discussion about black holes which does not use any of Einsteins complicated field equations and relies (mainly) on school level physics with a few digressions on the way. Escape Velocity First of all I am going to discuss the ‘escape velocity’ – the speed that we would need to throw […]

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Why do metals have low specific heat capacities? – they don’t

I came across the following answer to the question “Why do metals have low specific heat capacities?”: Metal atoms in pure metal are very close together and are able to transfer heat easily via conduction from one atom exciting the other atoms next to it. So the amount of energy it takes to heat a […]

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Controlling Nuclear Fission

Every induced fission event produces two or more neutrons. These neutrons can go on to induce more fission or they can be absorbed without producing fission or lost from the surface of the reactor core. To keep the reactor self sustaining at least one neutron must go on to produce one fission for every fission […]

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Production and Fission of Transuranic Elements In A Nuclear Reactor

If you are wondering where I am going with this it is because it is relevant to nuclear weapons proliferation, thorium fuel cycles and the problems with high burnup fuel. In a previous post I explained a bit about neutron capture, cross sections etc. Now I am going to consider a simplified model for neutron […]

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More About Neutrons

This is another background post and I am going to explain a bit more about the interaction of neutrons with matter. Since neutrons do not have a charge we are going ignore their interaction with electrons – they do interact somewhat but going into this now could be confusing. They do interact with atomic nuclei. […]

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Cs-137 in Spent Fuel as it leaves the reactor

I am now going to get a rough idea of how much caesium 137 there is in spent nuclear fuel. One reason for choosing Cs-137 is that it is a major fission product, it has a reasonably long half-life (30.17 years), it has a low melting and boiling point and is readily absorbed by the […]

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Production and Decay of Fission Products

We are going to assume that the fissile product has one mode of decay and does not do anything naughty such as undergo neutron capture. We can then write its rate of production as: where is the decay constant for fission product N, is the number of fissions per second and is the fraction of […]

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Radioactivity of U-238

This is just an example of how to calculate the radioactivity of an isotope from its halflife. Uranium 238 has a halflife of 4.468×109 years (4,468,000,000years). This is 4.468×109 x 365.25 x 24 x 60 x 60 = 1.41×1017 seconds. We can now calculate the decay constant (i.e. the number of decays per second) using […]

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