Essay About Moveable Pieces Of Neutron And Reactivity K Of Reactorcandu Reactors

Idealized Thermal Nuclear Reactor
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Idealized Thermal Nuclear ReactorFuel Rods:Fuel in form of small pelletsPellets held in bundles and several bundles make up fuel rodControl Rods:Moveable pieces of neutron-absorbing material Used to control reactivity k of reactorCANDU reactors use light water in control rodsFine tuning of reactivity done with stainless steel neutron flux adjuster rodsModerator:Slows fission neutrons to an energy where fission cross section of fuel high enough to guarantee k > 1Neutron Reflector:Layer of neutron-moderating material surrounding the reactor core which causes fast neutrons emitted from core to undergo elastic scattering with some being reflected back into coreCANDU reactors: D2O moderator surrounding core acts as a neutron reflectorGreatly increases efficiencyReactor Vessel:Outer boundary of reactor coreCANDU reactors the calandria vessel is very big but isn’t exposed to high temp or pressureNuclear Reactor FuelsFissile Material:Material which undergoes fission when hit with low energy thermal neutronsFertile Material:Material that doesn’t undergo fission within a nuclear reactor however it absorbs neutrons and decays into new isotopes which are fissileLight Water ReactorsUse H2O as coolant and moderator Must use enriched uranium because H2O moderator absorbs too many neutrons to allow natural uranium to be used as fuelThermal efficiency of 30-33%Gas-Cooled ReactorsCooled with either CO2 or Helium (He) gas (not strong neutron absorbers)Moderated with graphiteMost thermal efficient up to 50%!Breeder ReactorsMost efficient breeder reactors use Fast neutrons to accomplish the fission processUse 233U as fuel For molten salt breeder reactor, the salt solution is piped through a graphite moderated coreNo control rods in corek value controlled by flow rate of molten salt through the coreinherently low efficiency but have high thermal efficiency (44%)CANDU ReactorPWR reactorPressure tubes are pressurized through the calandriaUO2 fuel pellets are in tubes and pressurized D2O coolant runs through the tubes and carries away the fission heatRoom temperature D2O fills spaces between pressure tubes in calandria and acts as primary moderator and neutron reflector of reactor core