Nuclear Flashcards
Define nuclear power and describe process of creating nuclear power.
Production of electricity by nuclear fission. Impact of neutron and U235 nucleus causes fission process - products are more neutrons which can collide with further U235 nuclei and heat.
What are the Commercial Reactor components?
Two stage cooling with heat exchanger. Conventional steam turbine power plant within second stage.
Describe the moderator and coolant and describe properties in a Pressurised Water Reactor.
Water is both moderator and coolant. Water in the core is at 150 bar and 350 degrees Celsius in liquid form.
Describe typical type of UK reactors including the moderator and coolant and properties of them. Describe efficiency of designs.
Usually gas coolant reactors. First early Magnox design and latterly an advanced coolant reactor design. In both, graphite is the moderator and CO2 is the coolant. In Magnox CO2 is @ 25 bar and 370 degrees Celsius. in AGR C02 is @ 40 bar and 650 degrees Celsius. Efficiency of Magmox = 32% and AGR = 41%.
Why is a nuclear chain reaction hard to sustain and how is this overcome?
U235 nuclei are thinly spread but this can be overcome by using moderator to slow down free neutrons and making them less like to be captured by abundant U238 nuclei.
Give examples of some moderators.
Water, heavy water (deuterium) and graphite
Describe the basis behind a breeder reactor.
Fuel becomes depleted as number of fissionable nuclei become depleted. If enriched fuel is used, more fissionable plutonium and U235 elements are found throughout the reaction. When the rate of production of the U235 exceeds that of consumption, this is classed as a breeder reactor.
How is the reactivity of a reactor adjusted?
The activity is reduced by lowering rods of neutron absorbing substance (such as boron) into the core
What is the typical efficiency of a conventional thermal reactor?
Around 35%
What has hampered the development of breeder reactors?
Technical difficulties and poor performance.
What is maximum working lifetime of commercial nuclear reactors?
30-40 years, after which they are shut down and dismantled.
How long does the heat circuit of reactor core stay reactive for?
Around 100 years before the site can be safely approached
How does fusion work?
Fusing of deuterium and tritium to form helium nuclei.
