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The BN-350 fast-neutron reactor at Aktau, Kazakhstan.It operated between 1973 and 1994. A fast-neutron reactor (FNR) or fast-spectrum reactor or simply a fast reactor is a category of nuclear reactor in which the fission chain reaction is sustained by fast neutrons (carrying energies above 1 MeV, on average), as opposed to slow thermal neutrons used in thermal-neutron reactors.
The multiplication factor, k, is defined as (see nuclear chain reaction): k = number of neutrons in one generation / number of neutrons in preceding generation . If k is greater than 1, the chain reaction is supercritical, and the neutron population will grow exponentially.
In 1942, the first artificial [note 1] critical nuclear reactor, Chicago Pile-1, was built at the University of Chicago, by a team led by Enrico Fermi. [4] From 1944, with the goal of weapons-grade plutonium production for fission bombs, the first large-scale reactors were operated at the American Hanford Site.
With the control rods down, the reaction is subcritical: too many neutrons are absorbed for a chain reaction to take place. Pulling up the rods makes the reactor critical, and the fuel rods start producing heat. During operation of a reactor, the amount of fuel contained in the core decreases monotonically.
Reactions with neutrons are important in nuclear reactors and nuclear weapons. While the best-known neutron reactions are neutron scattering , neutron capture , and nuclear fission , for some light nuclei (especially odd-odd nuclei ) the most probable reaction with a thermal neutron is a transfer reaction:
Suppose also that the reactor is highly supercritical and ΔK/K is 0.00700. Reactivity in dollars = ρ / β eff = 0.007 / 0.007 = 1$ If the excess reactivity of a reactor is 1 dollar (1$) or more, the reactor is prompt critical. Prompt neutrons are so numerous that the production of delayed neutrons is no longer needed to ...
A: So the reactor is fueled, the reactor is closed, bolted shut. Control rods are slowly being pulled out. The control rods absorb neutrons without undergoing any nuclear reactions.
Thus, by widening the margins of non-operation and supercriticality and allowing more time to regulate the reactor, the delayed neutrons are essential to inherent reactor safety, even in reactors requiring active control. The lower percentage [3] of delayed neutrons makes the use of large percentages of plutonium in nuclear reactors more ...