What is Nuclear Power.

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What is Nuclear Power

Like coal, oil and natural gas, uranium is an energy resource which must be processed through a series of steps to produce an efficient fuel for use in the generation of electricity. Each fuel has its own distinctive fuel cycle: however the uranium or 'nuclear fuel cycle' is more complex than the others.

To prepare uranium for use in a nuclear reactor, it undergoes the steps of mining and milling, conversion, enrichment and fuel fabrication. These steps make up the 'front end' of the nuclear fuel cycle.

After uranium has been used in a reactor to produce electricity it is known as 'spent fuel' and may undergo a further series of steps including temporary storage, reprocessing, and recycling before eventual disposal as waste. Collectively these steps are known as the 'back end' of the fuel cycle.

The Nuclear Fuel Cycle

Like coal, oil and natural gas, uranium is an energy resource which must be processed through a series of steps to produce an efficient fuel for use in the generation of electricity. Each fuel has its own distinctive fuel cycle: however the uranium or 'nuclear fuel cycle' is more complex than the others.

To prepare uranium for use in a nuclear reactor, it undergoes the steps of mining and milling, conversion, enrichment and fuel fabrication. These steps make up the 'front end' of the nuclear fuel cycle.

After uranium has been used in a reactor to produce electricity it is known as 'spent fuel' and may undergo a further series of steps including temporary storage, reprocessing, and recycling before eventual disposal as waste. Collectively these steps are known as the 'back end' of the fuel cycle.

These are the steps which together make up the Nuclear Fuel Cycle.

Mining and milling

Uranium is usually mined by either surface (open cut) or underground mining techniques, depending on the depth at which the ore body is found. In Australia the Ranger mine in the Northern Territory is open cut, while Olympic Dam in South Australia is an underground mine (which also produces copper, with some gold and silver). Most Canadian uranium mines are underground.

The mined uranium ore is sent to a mill which is usually located close to the mine. At the mill the ore is crushed and ground to a fine slurry which is leached in sulfuric acid to allow the separation of uranium from the waste rock. It is then recovered from solution and precipitated as uranium oxide (U308) concentrate.
(Sometimes this is known as "yellowcake", though it is finally khaki in colour.)

Some new mines in Australia, USA and Asia use in situ leaching (ISL) to extract the uranium from the ore body underground and bring it to the surface in solution. It is recovered in the same fashion.

U308 is the uranium product which is sold from the mine. About 180-200 tonnes is required to keep a large (1000 MWe) nuclear power reactor generating electricity for a year.

Conversion

Because uranium needs to be in the form of a gas before it can be enriched, the U308 is converted into the gas uranium hexafluoride (UF6) at a conversion plant in Europe or North America.

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Enrichment

The vast majority of all nuclear power reactors in operation and under construction require 'enriched' uranium fuel in which the content of the U-235 isotope has been raised from the natural level of 0.7% to about 3.5% or slightly more. The enrichment process removes 85% of the U-238 by separating gaseous uranium hexafluoride into two streams: One stream is enriched to the required level and then passes to the next stage of the fuel cycle. The other stream is depleted in U-235 and is called 'tails'. It is mostly U-238.

So little U-235 remains in the tails (usually less ...

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