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Some isotopes undergo spontaneous fission (SF) with emission of neutrons.The most common spontaneous fission source is the isotope californium-252. 252 Cf and all other SF neutron sources are made by irradiating uranium or a transuranic element in a nuclear reactor, where neutrons are absorbed in the starting material and its subsequent reaction products, transmuting the starting material into ...
A startup neutron source is a neutron source used for stable and reliable initiation of nuclear chain reaction in nuclear reactors, when they are loaded with fresh nuclear fuel, whose neutron flux from spontaneous fission is insufficient for a reliable startup, or after prolonged shutdown periods. Neutron sources ensure a constant minimal ...
In 1947, John von Neumann sent a letter to Robert Richtmyer proposing the use of a statistical method to solve neutron diffusion and multiplication problems in fission devices. [5] His letter contained an 81-step pseudo code and was the first formulation of a Monte Carlo computation for an electronic computing machine.
A fixed source calculation involves imposing a known neutron source on a medium and determining the resulting neutron distribution throughout the problem. This type of problem is particularly useful for shielding calculations, where a designer would like to minimize the neutron dose outside of a shield while using the least amount of shielding ...
ACAB-2008, ACtivation ABacus Code nea-1638 ANITA-IEAF, Isotope Inventories from Intermediate Energy Neutron Irradiation for Fusion Applications nesc0873 COAST-4, Design and Cost of Tokamak Fusion Reactors nea-1200 ELEORBIT, 3-D Simulation of Electron Orbits in Magnetic Multipole Plasma Source nea-0490
The mere fact that an assembly is supercritical does not guarantee that it contains any free neutrons at all. At least one neutron is required to "strike" a chain reaction, and if the spontaneous fission rate is sufficiently low it may take a long time (in 235 U reactors, as long as many minutes) before a chance neutron encounter starts a chain reaction even if the reactor is supercritical.
The Chinese built Miniature Neutron Source reactor (MNSR) is a small and compact research reactor modeled on the Canadian HEU SLOWPOKE-2 design. The MNSR is tank-in-pool type, with highly enriched fuel (~ 90% U235). The tank is immersed in a large pool, and the core is, in turn, immersed in the tank.
The High Flux Isotope Reactor (HFIR) is a nuclear research reactor at Oak Ridge National Laboratory (ORNL) in Oak Ridge, Tennessee, United States.Operating at 85 MW, HFIR is one of the highest flux reactor-based sources of neutrons for condensed matter physics research in the United States, and it has one of the highest steady-state neutron fluxes of any research reactor in the world.