Idealized Thermal Nuclear Reactor
Essay by Andrew Keenleyside • February 18, 2018 • Coursework • 348 Words (2 Pages) • 879 Views
Idealized Thermal Nuclear Reactor
Fuel Rods:
- Fuel in form of small pellets
- Pellets held in bundles and several bundles make up fuel rod
Control Rods:
- Moveable pieces of neutron-absorbing material
- Used to control reactivity k of reactor
- CANDU reactors use light water in control rods
- Fine tuning of reactivity done with stainless steel neutron flux adjuster rods
Moderator:
- Slows fission neutrons to an energy where fission cross section of fuel high enough to guarantee k > 1
Neutron 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 core
- CANDU reactors: D2O moderator surrounding core acts as a neutron reflector
- Greatly increases efficiency
Reactor Vessel:
- Outer boundary of reactor core
- CANDU reactors the calandria vessel is very big but isn’t exposed to high temp or pressure
Nuclear Reactor Fuels
Fissile Material:
- Material which undergoes fission when hit with low energy thermal neutrons
Fertile Material:
- Material that doesn’t undergo fission within a nuclear reactor however it absorbs neutrons and decays into new isotopes which are fissile
Light Water Reactors
- Use H2O as coolant and moderator
- Must use enriched uranium because H2O moderator absorbs too many neutrons to allow natural uranium to be used as fuel
- Thermal efficiency of 30-33%
Gas-Cooled Reactors
- Cooled with either CO2 or Helium (He) gas (not strong neutron absorbers)
- Moderated with graphite
- Most thermal efficient up to 50%!
Breeder Reactors
- Most efficient breeder reactors use Fast neutrons to accomplish the fission process
- Use 233U as fuel
- For molten salt breeder reactor, the salt solution is piped through a graphite moderated core
- No control rods in core
- k value controlled by flow rate of molten salt through the core
- inherently low efficiency but have high thermal efficiency (44%)
CANDU Reactor
- PWR reactor
- Pressure tubes are pressurized through the calandria
- UO2 fuel pellets are in tubes and pressurized D2O coolant runs through the tubes and carries away the fission heat
- Room temperature D2O fills spaces between pressure tubes in calandria and acts as primary moderator and neutron reflector of reactor core
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