Скачать или смотреть Controlling a chain reaction with cadmium atoms

In this variant of the simulation    • Chain reaction: Shooting a single neutron ...   modeling nuclear fission, cadmium atoms have been added to the initial stack of uranium atoms, in a proportion of 40%. Cadmium atoms are good absorbers of neutrons, and can therefore prevent the nuclear reaction from getting out of control. In a nuclear reactor, they are contained in the control rods, whose purpose it is to control the flux of neutrons, partly by absorbing them, but also by slowing down other neutrons to make the nuclear reaction possible.
The reaction modeled here is one of the most common in nuclear fission, in which a uranium 235 atom, hit by a neutron, decays in a strontium 95 atom, a xenon 139 atom, and two neutrons, having some extra kinetic energy. These two neutrons can hit other uranium atoms, which expel more neutrons, provoking a chain reaction. The difference to the previous simulation is that a single neutron is used at the beginning, instead of several neutrons.
In this simulation, the reaction has been decomposed into three more elementary reactions:
²³⁵U + n → A + B
A → ⁹⁵Sr + ¹³⁹Xe
B → n + n
In addition, the reaction
¹¹²Cd + n → ¹¹³Cd
describes the capture of a neutron by a cadmium atom.
The first reaction has a certain probability to occur when a neutron remains close to uranium atom for a sufficient time, and when the difference of kinetic energies is not two large. The reactions are exothermic, meaning that the created neutrons tend to have a larger kinetic energy. The masses of the particles have been taken proportional to their atomic weight. However, the reaction probabilities and exothermic energy gain have been tweaked to obtain a nice reaction speed, neither too fast nor too slow.
This video has two parts, showing the same evolution with two different color codings:
Particle type: 0:00
Kinetic energy: 1:24
In the first part, the particles' color depends on their type: neutrons are red, uranium atoms are dark blue, while strontium and xenon atoms are yellow and green, and cadmium isotopes are cyan or blue. In the second part, the particles' color depends on their kinetic energy. The graph at the top right shows the number of atoms of each type over time.
To save on computation time, particles are placed into a "hash grid", each cell of which contains between 3 and 10 particles. Then only the influence of other particles in the same or neighboring cells is taken into account for each particle.

Render time: 2 minutes 47 seconds
Compression: crf 23
Color scheme: Turbo, by Anton Mikhailov
https://gist.github.com/mikhailov-wor...

Music: "Flight Is Aight" by Karneef‪@karn33f‬

Current version of the C code used to make these animations:
https://github.com/nilsberglund-orlea...
https://www.idpoisson.fr/berglund/sof...
Some outreach articles on mathematics:
https://images.math.cnrs.fr/auteurs/n...
(in French, some with a Spanish translation)

#atoms #particles #fission #nuclearreactions