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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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A Rough Model of a Nuclear Reactor

This model is very rough however it gives some idea  about power and energy output from a nuclear reactor which I will use in later posts. The model is very simplistic but is useful in understanding some of the processes that are going on. We are going to assume that all the power is from […]

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Uranium Enrichment Formula

This is another one of those background information posts deriving the mass balances for uranium enrichment. Let us consider the following enrichment  scenario: We have mass F of unenriched uranium entering on the left. It has Nf of U-235 (0.72% for natural uranium). After enrichment mass P of product enriched to Np of U-235 and […]

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Secular and Transient Equilibrium Formula

I will give the full derivation since although it is quite long and looks complicated it uses nothing more than A-level mathematics. Despite this the solution of the differential equations is usually given as a standard solution rather than derived. Consider a parent isotope (P) decaying into a daughter product (D). The rate of decay […]

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Secular Equilibrium

The reason for this post is to help people understand ‘secular equilibrium’. The reason for people interest is mainly due to this report which is based on data here. I have a bit to say about this data but will not go into it now. If you want a more mathematical explanation the see here […]

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Thorium and Proliferation

I will probably write about the Thorium cycle a bit more at some later point. There seems to be a growing number of people who say that we can use Thorium as a nuclear fuel. One of the reasons they state is that you cannot make a bomb from Uranium-233 and therefore the thorium cycle […]

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