MOX fuel assembly

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Head area of ​​a fuel assembly. Detail left: uranium tablets (pellets) in the fuel rods

As a mixed-oxide fuel , in short, MOX fuel ( MOX = mixed oxide), are in the nuclear fuel called that, unlike fuel of pure uranium dioxide , another oxide included. Mostly it is plutonium dioxide , less often thorium dioxide . Only uranium-plutonium mixed oxide is dealt with below.

description

Plutonium is inevitably produced in any uranium-fueled nuclear reactor . If the spent fuel elements are reprocessed , which was initially forbidden in Germany and now possible in limited quantities (see Nuclear Non-Proliferation Treaty ), plutonium is usually separated for various reasons, especially because of its greater radioactivity and high biological hazard.

There has been an excess of plutonium in the world since the two superpowers agreed on massive nuclear disarmament (see below).

Plutonium can be used in the form of MOX fuel in nuclear reactors and used there to generate energy . In light water reactors , this is an option for breeder reactors is a necessity, because the required there high neutron yield of nuclear fission is only with a high enough plutonium -239 content in fuel (and cleavage by fast, not moderated reached neutrons).

In 2011, MOX fuel elements were used in 21 French nuclear reactors , in 10 of the 17 German nuclear reactors at the time and in Japan. A total of around 30 thermal reactors in Europe (Belgium, Switzerland, Germany and France) contained MOX in 2017 and a total of 40 received permits. In Europe, nuclear fuel reprocessing for the production of MOX takes place exclusively in France, to a lesser extent in Russia and Japan. In China there are plans for fast breeders and reprocessing plants . The USA has been operating appropriate reprocessing plants for a long time, with interruptions due to the possible use of plutonium in nuclear weapons.

Reactor 3 of the Fukushima I nuclear power plant has also contained MOX fuel elements since August 2010. At the time of its explosion, 32 of the total of 548 fuel elements were made of MOX fuel.

Effects on the operational safety of the reactor

The use of MOX in light water reactors causes a slight increase in the radiation damage to which the reactor pressure vessel is exposed. The radiation damage is caused by the "fast" part of the neutron flux . This proportion is higher in the fission of plutonium than in the case of uranium. The calculation of the neutron spectrum in a Westinghouse pressurized water reactor fully loaded with MOX resulted in a 12% higher rapid flow compared to pure uranium oxide fuel; with the usual admixture of 30% MOX fuel elements, this corresponds to an increase of 4%.

Another effect comes from the lower proportion of delayed neutrons in plutonium-239 compared to uranium-235. As a result, the distance between the states becomes somewhat smaller with a delayed critical and promptly critical and requires a correspondingly fine reactor control.

Manufacturing

The manufacturing process for MOX fuel elements is similar to that of uranium dioxide fuel elements. Plutonium is a much more dangerous substance than uranium because of its greater radioactivity and its tendency to form aerosols . Therefore, significantly greater safety precautions must be taken. The processing takes place in shielded, airtight enclosures ( glove box technology ) and is largely automated. The admixture of plutonium is 7–11%, on average 9.5%. If weapons-grade plutonium (≥ 90% Pu-239) is used, only an admixture of 5% is required.

Manufacturer

Large plants for the production of MOX fuel elements are or were among others

In August 2011, a few months after the start of the Fukushima nuclear disaster , the UK Nuclear Regulatory Authority announced that the Sellafield Mox Plant would be shut down in 2011. Since the disaster in Fukushima, the market situation has changed because future demand from Japan is uncertain. In addition, the costs for UK taxpayers - previously 1.4 billion euros - should be minimized.

In Japan, Japan Nuclear Fuel Limited is working on the completion of a plant called J-MOX in 2017 , with completion scheduled for 2022. Template: future / in 2 yearsSmall plants are working near the Tōkai nuclear power plant (120 km northeast of Tokyo) and in Mayak (Russia).

For nuclear powers that have nuclear weapons with plutonium and want to destroy them, the production of MOX elements is a possibility to dispose of the plutonium with its long half-life . The only ways to dispose of plutonium are to mix it with nuclear waste with subsequent final storage or to convert it into MOX fuel, which reduces the proportion of plutonium during final disposal, but increases the proportion of other long-lived alpha emitters in this regard.

In 2010, the USA and Russia agreed in the Plutonium Management and Disposition Agreement to reduce their stocks of weapons plutonium by 34 tons each. This amount is sufficient to build up to 17,000 bombs. The protocol was signed in Washington in April 2010 by Secretary of State Hillary Clinton and Sergei Lavrov ; the treaty was ratified by Russia on May 20, 2011. The 2010 estimated cost would be $ 2.5 billion; of this, the USA will take on $ 400 million and other G-8 countries will take on another million.

For cost reasons, the US side plans not to convert its own plutonium into MOX fuel elements as agreed, but rather to dilute it with non-radioactive material. However, the dilution can be reversed (with great effort). On October 3, 2016, Russian President Putin ordered the agreement to be suspended because the US side had failed to fulfill its obligations.

Germany

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In 1991, the Hessian Ministry of the Environment banned production in Hanau-Wolfgang . At the beginning of 1992, a report by the Society for Reactor Safety (Cologne) warned of the dangers of MOX elements and thus confirmed warnings from the Öko-Institut (Darmstadt).

In 1995, Siemens stopped building a larger facility.

Between 2000 and 2008, a total of nine (of the 17 at the time) German nuclear power plants used mixed oxide fuel elements from reprocessing together with conventional uranium fuel elements. The fuel elements remain in the reactor core for an average of four years. So far (as of February 2011) 51 MOX fuel elements have been returned to Germany from French reprocessing plants . An application for the transport of 16 MOX fuel elements by sea from Sellafield in the UK to the Grohnde nuclear power plant was withdrawn by E.ON in February 2011, but implemented in September and November 2012.

As part of the 2009 (?) And April 2012 revisions, no MOX fuel elements were used in Grohnde.

The German nuclear power plant operators have agreed with the British and French reprocessing plants for the production and delivery of 170 t of mixed oxide, which corresponds to around 648 fuel elements, for the period 2009 to 2016. In March 2012, the Federal Office for Radiation Protection (BfS) approved the transport of Mox fuel elements from the British Sellafield MOX Plant to the Grohnde nuclear power plant. According to the operator E.ON, the mixed oxide fuel elements should not yet be used during the revision in April 2012. On the morning of September 24, 2012, eight fuel elements from Sellafield reached the Grohnde NPP.

Load of MOX fuel elements in t per year (planning status 2010)
Nuclear power plant operator 2000 2001 2002 2003 2004 2005 2006 2007 2008
Emsland RWE - - - - 6.5 6.5 6.5 6.5 6.5
Brokdorf E.ON 8.5 8.5 8.5 8.5 4.2 8.5 - 8.5 8.5
Lower Weser E.ON 8.5 8.5 8.5 2.1 12.7 2.1 6.4 - -
Grohnde E.ON 6.4 8.5 8.5 8.5 8.5 - - - -
Philippsburg 2 EnBW - - 8.5 10.6 8.5 10.6 8.5 - -
Neckarwestheim 2 EnBW 8.6 4.3 4.3 6.4 - - - - -
Gundremmingen RWE 11.8 14.6 19.2 19.5 16.7 18.1 16.7 - 10.4
Isar 2 E.ON - 17.1 17.1 8.6 - 6.4 6.4 6.4 6.4
Grafenrheinfeld E.ON - 8.5 8.5 8.5 8.5 8.5 6.4 6.4

About the table: The Unterweser and Grafenrheinfeld nuclear power plants have meanwhile been shut down as part of the German nuclear phase-out.

From the ' State Survey on the Disposal of Spent Fuel Elements from Nuclear Power Plants in the Federal Republic of Germany' as of December 31, 2010 , the Federal Government reported the contract quantities for the manufacture of MOX fuel elements that had been concluded by the operators at that time (Pu fiss = fissile Plutonium-239 and -241):

  • Neckarwestheim, Unit 2: 28 fuel elements, from 2016, 660 kg Pu fiss
  • Isar, Block 2: 48 fuel elements, 2011–2014, 1176 kg Pu fiss
  • Gundremmingen, Units B and C: 112 fuel elements, 2018, 865 kg Pu fiss
  • Grohnde: 16 fuel elements, 2012, 264 kg Pu fiss
  • Emsland: 12 fuel elements, 2011, 298 kg Pu fiss and 28 fuel elements 2017-2019, 693 kg Pu fiss
  • Brokdorf: 36 fuel elements, 2013–2015, 750 kg Pu fiss
  • Total: 4,706 kg Pu fiss

In the same answer, the federal government also reported how many MOX fuel elements were imported to Germany between 2001 and August 5, 2011.

Japan

The world's first use of MOX fuel elements took place in a Japanese prototype, in the Fugen nuclear power plant since March 1978. In 1995, the government decided not to build reactors of this type any more because the costs were too high compared to light water reactors. In March 2003 this reactor was shut down.

In November 2009, MOX elements were used for the first time in a commercial nuclear power plant in Japan, namely in reactor 3 of the Genkai nuclear power plant . "We have finally reached this point," said Shojiro Matsuura, President of the Nuclear Safety Commission of Japan .

Before that, numerous breakdowns, accidents and earthquake damage had increased distrust of the nuclear industry and delayed the first use of MOX for many years.

On March 8, 2010, reactor 3 of the Ikata nuclear power plant (Ehime prefecture), together with reactor 3 of the Fukushima I nuclear power plant, began generating electricity with MOX fuel elements. The latter received 32 MOX fuel elements in August 2010 (out of a total of 548 fuel elements).

The nuclear disaster in Fukushima in March 2011 resulted in core meltdowns in reactor units 1, 2 and 3 of the plant, as well as an explosion in the reactor building of unit 3. Plutonium was also released in this incident.

Before the accident, it was planned to use MOX elements nationwide in 16 to 18 nuclear reactors by 2015 . Next, electricity companies Shikoku Denryoku and Chūbu Denryoku MOX wanted to use.

Switzerland

In Switzerland, MOX has been used in the Beznau nuclear power plant since 1978 and in the Gösgen nuclear power plant since 1997 . In the KKG, however, MOX fuel has not been used for some time because the contract volume has been used up.

United States

The United States is building a new MOX facility on the Savannah River in South Carolina for $ 4.86 billion . Production is scheduled to begin between 2016 and 2018 and utilize 43 tons of plutonium from the nuclear arsenal. Although the Tennessee Valley Authority (TVA) and Duke Energy have an interest in utilizing MOX fuel from the conversion of weapons plutonium, TVA (currently the most likely customer) stated in April 2011 that it would wait until a decision was made on what it would provide on the connection between the use of MOX fuel and the Fukushima Daiichi reactor accident. In May 2018, Energy Secretary Rick Perry informed Congress that he had definitely completed the project (Savannah River Site), which was around 70% complete. Perry stated that the cost of a diluted and discarded approach to the plutonium will cost less than half the remaining life cycle cost of the MOX facility program.

Individual evidence

  1. ↑ Areva stops atomic delivery ( Memento from March 19, 2011 in the Internet Archive )
  2. ↑ a b c MOX, Mixed Oxide Fuel. World Nuclear Association , June 2017, accessed September 12, 2017 .
  3. ↑ a b Keth Bradsher, Hiroko Tabuchi: Greater Danger Lies in Spent Fuel Than in Reactors. In: New York Times . March 17, 2011, accessed September 12, 2017 .
  4. ↑ Franceschini and Petrovic, Annals of Nuclear Energy 35 (2008) pp. 1587-1597, Fig. 2
  5. ↑ After Fukushima - Great Britain closes the fuel element factory . Spiegel Online , August 3, 2011
  6. ↑ JNFL: MOX Fuel Fabrication | Business - JNFL , accessed March 25, 2018
  7. ↑ Tsuyoshi Sampei, Kazuhiko Hiruta, Junji Shimizu, Ko Ikegame: Current status of J-MOX safeguards design and future prospects . Ed .: IAEA . ( PDF ).
  8. ↑ a b message from April 15, 2010
  9. ↑ Russia ratifies treaty to destroy plutonium
  10. ↑ Obama seeks to terminate MOX project at Savannah River , World Nuclear News, February 10, 2016.
  11. ↑ Pavel Podvig: Can the US-Russia plutonium disposition agreement be saved? Bulletin of the Atomic Scientists, April 28, 2016.
  12. ↑ Указ Президента Российской Федерации от 03.10.2016 № 511
  13. ↑ Careless game . In: Der Spiegel . No. 7 , 1992 ( online ).
  14. ↑ Detlef Esslinger: Fuel element plant in Hanau - What was involved in politics never went into operation . sueddeutsche.de. December 3, 2003. Retrieved on January 5, 2009.  ( Page no longer available , search in web archives )  Info: The link was automatically marked as defective. Please check the link according to the instructions and then remove this notice.@1@ 2Template: Toter Link / www.sueddeutsche.de  
  15. ↑ a b c d Safety during the transport, storage and use of MOX fuel assemblies. Answer 17/1067 to a small question to the federal government. (PDF; 202 kB) German Bundestag , April 8, 2010, accessed on March 19, 2011 .
  16. ^ Mox fuel elements: E.ON surprised licensing authority. dewezet.de, February 8, 2011, accessed on March 19, 2011 .
  17. ↑ E.ON Kernkraft postpones the transport of mixed oxide fuel elements to the Grohnde joint nuclear power plant. (No longer available online.) Eon-kernkraft.com, February 7, 2011, formerly in the original ; Retrieved March 19, 2011 .  ( Page no longer available , search in web archives )  Info: The link was automatically marked as defective. Please check the link according to the instructions and then remove this notice.@1@ 2Template: Dead Link / www.eon-kernkraft.com  
  18. ↑ contratom.de
  19. ↑ The nuclear transport to Grohnde ends without incident
  20. ↑ Freighter brings British fuel elements to Germany . Spiegel Online , September 23, 2012
  21. ↑ Answer of the Federal Government to the small question of the MPs Sylvia Kotting-Uhl, Hans-Josef Fell, Bärbel Höhn, other MPs and the faction BÜNDNIS 90 / DIE GRÜNEN: Closure of the fuel element factory in Sellafield ( BT-Drs. 17/7137 ) , P. 2.
  22. ↑ Answer of the Federal Government to the small question of the MPs Sylvia Kotting-Uhl, Hans-Josef Fell, Bärbel Höhn, other MPs and the faction BÜNDNIS 90 / DIE GRÜNEN: Closure of the fuel element factory in Sellafield ( BT-Drs. 17/7137 ) , Pp. 3-6.
  23. ↑ a b Traces of plutonium reveal the extent of the disaster . Spiegel Online , March 29, 2011
  24. ↑ a b Japan produces nuclear power with plutonium for the first time . taz.de, November 10, 2009
  25. ↑ This recycled fuel was fabricated on 2008 at AREVA's MELOX plant in southern France using the plutonium recovered from the treatment operations of used fuels performed at AREVA's La Hague plant .
  26. ↑ The reactor accident in Fukushima Daiichi. (PDF; 477 kB) German Atomic Forum , March 2015, pp. 4–6 , accessed on September 12, 2017 .
  27. ↑ fact sheet August 2002. nuklearforum.ch
  28. ↑ TVA might use MOX fuels from SRS . In: The Augusta Chronicle , June 10, 2009
  29. ^ New Doubts About Turning Plutonium Into a Fuel . In: New York Times , April 11, 2011
  30. ^ Perry scraps completion of US MOX facility , World Nuclear News. May 16, 2018. Retrieved May 17, 2018.