Class Notes on Fission Reactors Nuclear accidents and Neutron detection

Class Notes on Fission Reactors Nuclear accidents and Neutron detection

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Class Notes on Fission Reactors, Nuclear Accident, and Neutron Detector Some References: 1) http://en.wikipedia.org/wiki/Nuclear_reactor 2) http://en.wikipedia.org/wiki/Nuclear_weapon_design#Fission_weapons 3) See also the links and references in 1 and 2 above. 4) http://www.uic.com.au/nip16.htm : Advanced Nuclear Power Reactors Fission Reactors A nuclear reactor, in its basic form, consists of four parts: 1) Fuel (usually enriched uranium); 2) A moderator, usually made from low atomic mass materials, to thermalize neutrons (how about the fast reactors?); 3) Control rods made of materials with a high neutron capture σ (e.g., Cd or B), and 4) A coolant to remove heat The fuel is contained in the reactor core . The core is where the fission chain is sustained and the energy of fission is released as heat. Since the most of the fissions result from the absorption of slow neutrons, the moderator must also be in the core (recall that the function of the moderator is to slow down the fission neutrons through the elastic scattering reactions). The core is surrounded by a neutron reflector of a material determined largely by the energy distribution of the neutrons in the reactor. The purpose of the reflector is to decrease the loss of neutrons from the core by scattering back many of those which escaped. The rate of heat generation is proportional to the nuclear fission rate and this is determined, in a given reactor core, by the neutron density, i.e., the number of neutrons per unit volume. Control, including startup, operation at any desired power level, and shut down, is thus achieved by varying the neutron density in the core. This is generally done by moving rods of a material that absorbs neutron readily, i.e., a neutron poison. Insertion of a poison results in decrease in the reactivity (or neutron multiplying property) of the core and, consequently, in a decrease in the neutron density. Note: some reactors (e.g., research, teaching, Naval) use Fuel Rods for control of power. The heat generated in the reactor core is removed by circulation of a suitable coolant . Heat must be removed from the core at a rate that permits the coolant to attain a high temperature without the development of such thermal stresses and internal temperatures as to cause the reactor to suffer damage.
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A schematic representation of a nuclear reactor system Boiling-water reactor system with its cycle schematic diagram
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Pressurized-water reactor system with its cycle schematic diagram
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Simplified steam-cycle schematic for the CANDU-PHW (Pressurized Heavy Water) Reactor
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Reactor and Criticality Accidents For the purpose of standardization, the Nuclear Regulatory Commission (NRC) divided the spectrum of possible accidents into classes, nine of which are listed in the table below. On site and off site failure of power at the time of Loss-of-Coolant Accident (LOCA)
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This note was uploaded on 04/11/2008 for the course CHNE 524 taught by Professor Mohagheghi during the Fall '08 term at New Mexico.

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Class Notes on Fission Reactors Nuclear accidents and Neutron detection

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