Post by Joe Neubarth on Dec 25, 2011 12:41:19 GMT -5
Fuel: Usually pellets of uranium oxide (and possibly Plutonium Oxide) arranged in Zirconium tubes to form fuel rods. The rods are arranged into fuel assemblies in the reactor core in a vertical manner so that Control Rods can be driven up or down between them.
Control rods: These are made with neutron-absorbing material such as cadmium, hafnium or boron, and are inserted or withdrawn from the core to control the rate of reaction, or to halt it (Full Insertion, commonly called a reactor scram if done in an emergency).
Moderator (Water): This is necessary to slow down the neutrons released from the fission of Uranium (or Plutonium) so that they cause more fission with heavy elements. When Uranium fissions it throws out two to three high speed neutrons. These have to slow down (lower energy level) to be able to cause more Uranium to fission. Without the moderator you can not have a controlled fissioning process.
Coolant: Water circulating through the core so as to transfer the heat from it. You have to be able to carry the heat away from the reactor (If you can't, very bad things like Meltdowns can happen.)
Reactor Vessel (Pressure Vessel) A robust steel and nickle alloy vessel containing the reactor core and moderator/coolant. It is designed to preheat the coolant entering, pass it up through the core where the coolant acts as a moderator and turns to steam. The steam under high pressure is directed to the steam turbine located in the turbine building.
Containment. The concrete and steel structure around the reactor core which is designed to protect it from outside intrusion and to protect those outside from the effects of radiation in case of any major malfunction inside. It is typically a meter-thick. The base can be several meters thick in order to contain the melted fuel and other metals and radioactive elements (Corium) in a meltdown. (Corium at 2000 degrees can melt its way through concrete.)
In a reactor the condensed water under high pressure that has been pumped from the condenser enters the Reactor Vessel and flows down the interior side while heating up. It then passes up through the core where it is heated to approximately 400 Degrees. It can reach this temperature as steam because it is under pressure. The Steam then flows out through the Steam Pipes to the Steam Turbine which converts the heat energy of the steam to centrifugal energy to drive an Electrical Generator. The electricity from the generators is increased to thousands of volts through transformers and passed into the electrical grid. The Steam after it has lost almost all of its energy is condensed back into water in the condenser so that it can be pumped back into the reactor.
Most reactors need to be shut down for refueling, so that the pressure vessel can be opened up. In this case refueling is at intervals of 1-2 years, when a quarter to a third of the fuel assemblies are replaced with fresh ones.
Natural uranium has the same elemental composition as when it was mined (0.7% U-235, over 99.2% U-238), enriched uranium has had the proportion of the fissile isotope (U-235) increased by a process called enrichment, commonly to 3.5 - 5.0%.
Practically all fuel is ceramic uranium oxide (UO2 with a melting point of 2800°C) and most is enriched. The fuel pellets (usually about 1 cm diameter and 1.5 cm long) are typically arranged in a long zirconium alloy (zircaloy) tube to form a fuel rod, the zirconium being hard, corrosion-resistant and permeable to neutrons. Up to 264 rods form a fuel assembly, which is an open lattice and can be lifted into and out of the reactor core. In the most common reactors these are about 3.5-4.0 metres long (About twice the height of a man).
The term MOX Fuel (Multiple Oxide Fuel) refers to fuel that contains Uranium and Plutonium (that has been harvested out of spent fuel rods). MOX fuel is at greater risk for a spontaneous fission accident as may have occurred at the Reactor Three Spent Fuel Pool at the top of Reactor 3
Control rods: These are made with neutron-absorbing material such as cadmium, hafnium or boron, and are inserted or withdrawn from the core to control the rate of reaction, or to halt it (Full Insertion, commonly called a reactor scram if done in an emergency).
Moderator (Water): This is necessary to slow down the neutrons released from the fission of Uranium (or Plutonium) so that they cause more fission with heavy elements. When Uranium fissions it throws out two to three high speed neutrons. These have to slow down (lower energy level) to be able to cause more Uranium to fission. Without the moderator you can not have a controlled fissioning process.
Coolant: Water circulating through the core so as to transfer the heat from it. You have to be able to carry the heat away from the reactor (If you can't, very bad things like Meltdowns can happen.)
Reactor Vessel (Pressure Vessel) A robust steel and nickle alloy vessel containing the reactor core and moderator/coolant. It is designed to preheat the coolant entering, pass it up through the core where the coolant acts as a moderator and turns to steam. The steam under high pressure is directed to the steam turbine located in the turbine building.
Containment. The concrete and steel structure around the reactor core which is designed to protect it from outside intrusion and to protect those outside from the effects of radiation in case of any major malfunction inside. It is typically a meter-thick. The base can be several meters thick in order to contain the melted fuel and other metals and radioactive elements (Corium) in a meltdown. (Corium at 2000 degrees can melt its way through concrete.)
In a reactor the condensed water under high pressure that has been pumped from the condenser enters the Reactor Vessel and flows down the interior side while heating up. It then passes up through the core where it is heated to approximately 400 Degrees. It can reach this temperature as steam because it is under pressure. The Steam then flows out through the Steam Pipes to the Steam Turbine which converts the heat energy of the steam to centrifugal energy to drive an Electrical Generator. The electricity from the generators is increased to thousands of volts through transformers and passed into the electrical grid. The Steam after it has lost almost all of its energy is condensed back into water in the condenser so that it can be pumped back into the reactor.
Most reactors need to be shut down for refueling, so that the pressure vessel can be opened up. In this case refueling is at intervals of 1-2 years, when a quarter to a third of the fuel assemblies are replaced with fresh ones.
Natural uranium has the same elemental composition as when it was mined (0.7% U-235, over 99.2% U-238), enriched uranium has had the proportion of the fissile isotope (U-235) increased by a process called enrichment, commonly to 3.5 - 5.0%.
Practically all fuel is ceramic uranium oxide (UO2 with a melting point of 2800°C) and most is enriched. The fuel pellets (usually about 1 cm diameter and 1.5 cm long) are typically arranged in a long zirconium alloy (zircaloy) tube to form a fuel rod, the zirconium being hard, corrosion-resistant and permeable to neutrons. Up to 264 rods form a fuel assembly, which is an open lattice and can be lifted into and out of the reactor core. In the most common reactors these are about 3.5-4.0 metres long (About twice the height of a man).
The term MOX Fuel (Multiple Oxide Fuel) refers to fuel that contains Uranium and Plutonium (that has been harvested out of spent fuel rods). MOX fuel is at greater risk for a spontaneous fission accident as may have occurred at the Reactor Three Spent Fuel Pool at the top of Reactor 3