Go Nuclear, Close cycle by Tony Green

Steaming nuclear plant 

Many validated and well researched arguments exist supporting going ahead with nuclear power as a partial solution to our energy woes. Some on the pros include reduced environmental energy production and carbon emissions. Those in opposition suggest the high costs, requirement for waste disposal, environmental, safety issues, and fuel availability are reason enough not to move forward.

In spite of these arguments nuclear power still provides 20% of our nations power requirements. Without a doubt this number would be higher it not for the Chernobyl and Three Mile Island nuclear accidents.

In my view nuclear power works. I may be biased as a result of my experience as an Ex Navy Nuke but I have seen nuclear power plant run safely thanks in a large part to the disciplined attention to detail demanded as part of the training process.

With that said one of the “enemies” of nuclear power still needs to be addressed before the public can but into a growth of nuclear power on the large scale. The issue is of nuclear waste. Since there is material which needs to be disposed of after its use in the nuclear generation process this is referred to an open cycle.

Uranium occurs naturally in two forms: U235 and U238. U238 more abundant but it is not readily fissionable in light-water reactors. Light water reactors are reactors which use water to slow the speed of the neutrons to the level which will result in sustainable fissions.

U235 is fissionable but its concentration is 0.7% in natural uranium. Reactors in general require up to 5% U235 by weight. The enrichment process is how you get from natural levels of uranium to the levels used in nuclear reactors commonly referred to as Low Enriched Uranium (LEU). The process to convert natural Uranium to LEU fuel is known as the nuclear fuel cycle.

Low-enriched uranium (LEU) is defined as having a concentration of U235 of less than 20%. For use in commercial light water reactors (LWR), the uranium is enriched to concentration of 3 to 5%. 

The steps for producing the material begin with Mining and milling. In this step the natural or enriched uranium is removed from the earth in the form of ore then crushed and concentrated. The next step is conversion in which the concentrates are combined with fluorine gas to produce uranium hexafluoride. UF6 is shipped to an enrichment plant.  Once at the enrichment plant the material is processed to increase concentration of U235 isotope in the UF6 in its natural state to 5% which is usable as fuel in light water reactors.

The uranium which is at a useable concentration is it ready for fuel fabrication. The LEU is converted to uranium oxide and formed into small ceramic pellets by fabricators. The pellets are loaded into metal tubes which form fuel assemblies which are shipped to nuclear plants and used in nuclear reactors. Once the reactor lifetime is completed the material which remains produces high levels of radioactivity.

Currently when a nuclear reactor is decommissioned the materials with its core are still highly radioactive. Many of the by-products boast half lives of thousands of years therefore precautions must be taken in order to protect the environment. Most nuclear facilities utilize local places on site to store waste in the short term. In the long term the waste will be deposited to a repository. At the moment the principal location for eventual disposal of nuclear waste is a Yucca mountain in Nevada.

As technology has cleared the way to change our lives technology in this case will be needed to avert having to handle the radioactive material. A pair of possibilities is developing fast fission reactor which produce a reduced amount of waste, or develop the technologies where the uranium used can be recycled which would effectively close the cycle. 

If not the anti nuclear folks could win out in their argument and ensure nuclear plans are not utilized as a possible solution of our increasing power requirements. What a shame that would be.