Fuel cycle
The term fuel cycle (fuel cycle) is used in nuclear technology to summarize all work steps and processes that serve to supply and dispose of radioactive substances. Nuclear power opponents criticize the term cycle because it falsely suggests a closed material cycle. It is rather correct that radioactive waste is always generated even when reprocessing is used. This is why the term fuel chain is used as an alternative.
Basic principles
The operation of nuclear power plants requires an infrastructure that includes, in particular, the supply of nuclear fuel (see fuel element factory ) and the storage of radioactive waste . In order to guarantee a supply, among other things, the mining of uranium ores , the extraction of uranium from the ores, the enrichment and the production of fuel elements must be provided. Waste treatment includes the removal of spent fuel elements from nuclear power plants, if necessary the separation of reusable fissile materials through reprocessing , the packaging of the radioactive waste and its final storage .
The following processing steps can be included in the fuel cycle of a light water reactor :
- Ore mining, rock milling, uranium extraction and conversion into yellow cake (see uranium mining )
- Conversion of the yellow cake into uranium hexafluoride
- Enrichment of uranium-235 using gas diffusion , ultracentrifuges or other methods
- Conversion to uranium dioxide , production of uranium tablets and fuel rods
- Use of the fuel elements in the reactor
- Interim storage of spent fuel elements
- Reprocessing of spent fuel elements and disposal of vitrified high-level radioactive waste or direct disposal of spent fuel elements
According to the Atomic Energy Act , the transport of spent fuel elements from German nuclear power plants to reprocessing plants has not been permitted since July 1, 2005. Since then, the only possible disposal route for spent fuel elements in Germany is direct final storage without reprocessing. This increases the amount of uranium used and the amount of waste generated, but reduces the risk of reprocessing and transportation.
In the case of heavy water reactors , the enrichment step is omitted because they can be operated with natural uranium. By reprocessing fuel elements that are to be used in breeder reactors , the amount of waste can be significantly reduced, since a larger number of isotopes can be reused.
Further products
Depleted uranium is produced as a waste product in uranium enrichment. 11.8 kg of natural uranium are required to produce 1 kg of uranium with an enrichment level of 5%. This means that 10.8 kg of depleted uranium are produced as low-level radioactive waste (less radioactivity than natural uranium). Based on these facts, the manufacture of uranium ammunition is an alternative to tungsten carbide ammunition .
Nuclear weapon proliferation
When nuclear power plants run on uranium fuel, plutonium is inevitable . This can basically be used for the production of atomic bombs. Plutonium suitable for this, weapons plutonium , can be obtained from the spent fuel of some nuclear power plants with chemical means; this process may be less time-consuming and cost-effective than enriching uranium. Another advantage of plutonium as a weapon material is its lower critical mass compared to uranium . The operation of nuclear power plants in this way increases the risk of the proliferation of nuclear weapons . To minimize this, various international treaties have been concluded. The most important of these treaties is the Nuclear Non-Proliferation Treaty . As a further measure, there are restrictions on the delivery of corresponding technologies to crisis countries (see e.g. Iraqi nuclear program ).
See also
Web links
- Website of the German Nuclear Fuel Cycle Association with links to companies in the field of fuel cycle
Individual evidence
- ↑ Nuclear phase-out immediately: Uranium mining and uranium export - a "cycle" with side effects (PDF; 950 kB) by Eric Tschöp, accessed on June 16, 2011.
- ↑ Jürgen Grunwald: The energy law of the European Communities . 2003, ISBN 978-3-89949-078-7 ( page 71 in the Google book search).
- ↑ Law on the peaceful use of nuclear energy and protection against its dangers (Atomic Energy Act) Section 9a , accessed on June 7, 2017.