Fuel assembly plant

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A fuel element factory is a nuclear facility for the production of fuel elements for nuclear power plants . The fuel elements have different composition and shape depending on the type of reactor in which they are used: They usually contain uranium as nuclear fuel in oxidic form (e.g. in light and heavy water reactors ) or in metallic form ( Magnox reactors ). However, some fuel elements also contain thorium (e.g. in high-temperature reactors ) or uranium-plutonium mixed oxide (see also MOX ) as fissile material . The latter is used in breeder reactors as well as in light water reactors.

Manufacture of uranium fuel elements

Most of the world's nuclear power plants are light water reactors. These need enriched uranium in oxidic form for their operation. In order to achieve this, enriched uranium hexafluoride (UF 6 ) is first converted to UO 2 . Wet (AUC, ADU) or dry (IDR) processes are used. In the wet process, the conversion is brought about by a chemical reaction with liquids. The resulting intermediate product gives the process its name: the ADU process produces ammonium diuranate as an intermediate product, and the AUC process ammonium uranyl carbonate. In contrast to this, no liquids are used in the dry IDR process (Integrated Dry Route). The conversion takes place in an oven at high temperature. The resulting powder is pressed into tablets ( pellets ) 2 to 3 cm long and 1 cm in diameter. They become ceramic material at about 1700 ° C sintered , mechanically finished (sanded) and in 4 to 5 m long casing tubes of Zircaloy filled. The ends of the ducts are welded shut. A larger number of individual rods (up to 250) become a fuel rod bundle, i.e. H. to form a fuel assembly . This process is called assembly. In some plants, all these sub-steps are carried out in one place, while other plants only take on certain process steps by processing intermediate products (e.g. assembly of fuel rods) or producing an intermediate product (e.g. uranium powder) themselves, which is done in another plant is further processed.

Manufacturing of MOX fuel elements

Fuel elements that contain plutonium dioxide in addition to uranium dioxide are called mixed oxide fuel elements or MOX fuel elements. Because of the presence of plutonium , special safety precautions must be taken in the manufacture of MOX fuel assemblies. All production steps are carried out in gas-tight enclosures and largely remote-controlled. The individual process steps are similar to those in the manufacture of uranium fuel elements.

Fuel element production in Germany

In Germany today only one fuel element factory, the Lingen fuel element manufacturing plant , is in operation. It is located in Lingen (Lower Saxony) and is operated by Areva . The fuel element factory has three production sites: the cladding tubes are manufactured in Duisburg (North Rhine-Westphalia), the components (head and foot parts of a fuel element) in Karlstein (Bavaria); The fuel elements are assembled in Lingen. The factory produces fuel elements for pressurized water reactors and for boiling water reactors . Demand in Germany has been greatly reduced due to the nuclear phase-out in March 2011 ; Lingen exports to many countries around the world.

There used to be a center for fuel assembly production in Hanau ( Hesse ). Different types of fuel assemblies were produced in four different plants. The Siemens company produced uranium fuel elements and MOX fuel elements in separate operating units , NUKEM produced fuel elements for research reactors and HOBEG operated a plant for the production of fuel elements for high-temperature reactors .

At the end of the 1980s, when planning still assumed large-scale reprocessing of spent fuel elements in Germany, Siemens began building a new, significantly larger and more modern fuel element factory for MOX fuel elements at the Hanau site ; but this never went into operation. The plant was supposed to process the plutonium produced during reprocessing into MOX fuel elements so that they can then be reused in the reactors. The licensing procedure got caught up in the political dispute over the future of nuclear energy, which became more intense after the Chernobyl disaster (1986).

In July 1993 the Hessian administrative court in Kassel revoked three of six partial licenses for the fuel element factory. In 1995 Siemens finally waived (probably for economic reasons) the operating license for the 95% completed plant. Instead, the German nuclear power plant operators concluded contracts with fuel element manufacturers in France ( Cogema ) and England ( British Nuclear Fuels ). The most important components were packed in containers.

In 2001 a sale to Russia failed. An attempt to sell the plant to China for 50 million euros ended after fierce political controversy in 2004 when China abandoned the delivery. The cost of the plant (planning and production) was estimated in 1995 (when Siemens abandoned the project) at 1.1 billion Deutschmarks.

Fuel assembly abroad

Fuel element production plants are in operation in numerous countries. The processes used depend heavily on the type of fuel elements that are manufactured there.

In the production of light water reactor fuel elements, the processes differ mainly in the process for converting UF 6 into UO 2 . Differences still exist in the scope of the partial production steps carried out by an individual system. So z. B. In some systems only UO 2 powder or pellets are produced, while others take on the sub-step of assembly. The most important plants for the production of uranium fuel elements are located in

MOX fuel elements are / were manufactured in the following countries:

See also

Web links

Individual evidence

  1. ↑ Plus minus September 11, 2013: No nuclear phase-out - In Germany, fuel assemblies are still being manufactured for export even after the last nuclear power plant was shut down. The uranium enrichment plant in Gronau, Westphalia, and the fuel element factory in Lingen, Lower Saxony, received unlimited operating permits. A current application by the state of North Rhine-Westphalia in the Federal Council to amend the Atomic Energy Act in order to end uranium enrichment in Germany has been postponed for an indefinite period. ( Memento from September 15, 2013 in the Internet Archive )
  2. ↑ a b c Quote : The assembly should be part of an international program for the destruction of weapons plutomium from stocks of the Russian military. According to information from the daily “taz”, the federal government approved a preliminary request from Siemens. But then only a few countries agreed to help finance the maintenance and operation of the plant. As a result, Siemens' interest died and the company decided in August 2001 to dismantle the factory and sell it in individual parts.
  3. ↑ http://www.world-nuclear-news.org/WR-Studsvik_to_decommission_Belgian_MOX_plant-050309.html
  4. ↑ http://www.world-nuclear-news.org/WR_Sellafield_MOX_plant_to_close_0308111.html