Traveling wave reactor

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A traveling wave reactor ( English traveling-wave reactor , TWR ) is a theoretical concept of a nuclear reactor type , the fertile material into fissile material converts ( hatching ). The TWR differs from the fast breeder in that it manages with little or no enriched uranium . Instead, it uses depleted uranium , natural uranium , thorium or spent fuel assemblies of light water reactors (LWR), and combinations of the aforementioned materials. The name is derived from the fact that the nuclear fission does not take place in the entire reactor, but only in a certain zone of the reactor, which spreads through the core over time.

Numerical simulation of a running wave reactor, red 238 U, green 239 Pu, blue neutron density

history

The idea of ​​a running wave reactor dates back to the 1950s and has been taken up and further developed since then. This concept of a reactor which its own fuel bred and equal self-consumed, from the first time in 1958 Saveli Feinberg explored. Feinberg spoke of the principle of breed-and-burn (in German breeding and burning ). It was started by Michael Driscoll in 1979, Lev Feoktistov in 1988, Edward Teller & Lowell Wood in 1995 , Hugo van Dam in 2000, Hiroshi Sekimoto in 2001 and has been followed by Bill Gates ' TerraPower since 2006 .

Reactor physics

Articles and presentations on the TerraPower TWR describe a reactor similar to the swimming pool reactor, which is cooled with liquid sodium . The reactor is mainly operated with depleted uranium, but requires a small amount of enriched uranium or other fissile materials to initiate nuclear fission. Some of the fast neutrons that are generated during nuclear fission convert neighboring breeding material (e.g. non-fissile depleted uranium) into plutonium through neutron capture :

At the beginning the core is filled with breeding material. A small amount of fissile material is added to one end of the reactor core. When the reactor is in operation, after some time four zones can be distinguished in its core:

  • The “fresh” zone, which contains the unused breeding material.
  • The breeding zone in which new fissile material is created through neutron capture.
  • The fission zone in which the nuclear fission takes place.
  • The “used” zone, which contains fission products as well as unused (hatched) fuel.

The energy-producing cleavage zone migrates through the core over time. The brood material is consumed on the one hand and fission products and unused fuel are left behind on the other. The heat that is generated during the fission and the breeding reaction is converted into electrical energy in a conventional steam turbine - generator combination .

fuel

Unlike conventional reactors, TWRs can be filled with enough depleted uranium during construction to provide energy for over 60 years or more at full power. In relation to the electrical power, TWRs consume significantly less uranium than previous reactors, since TWRs burn the fuel more efficiently and have a better thermal efficiency . The TWR can be reprocessed during operation without the need for the chemical separation that is typical for other breeder types. These properties significantly reduce the amount of fuel and waste and make proliferation more difficult .

Depleted uranium as a starting fuel is abundantly available as it is a waste product of the enrichment of uranium. The United States' current inventory of depleted uranium is approximately 700,000 tons. TerraPower estimates the value of the electricity to be generated from it at USD 100 trillion . According to the company, TWRs with the depleted uranium stored around the world could supply 80% of the world's population with per capita electricity consumption at the level of the average US citizen for over a millennium. In addition, there are around 4.5 billion tons of uranium, which is found in dissolved form in seawater.

In principle, TWRs could use spent fuel assemblies from LWRs. This is possible because these spent fuel elements consist mainly of depleted uranium and because the absorption of the fast neutrons of the TWR at fission products is several orders of magnitude smaller than that of the thermal neutrons in the LWR.

TWRs are also, in principle, able to recycle their own fuel. The spent material from the TWR still contains fissile material. By reforming and re-encapsulating into new pellets , the fuel can be reused in TWRs without chemical reprocessing. This eliminates the need for uranium enrichment.

Possible problems

Since the construction of the reactor has not yet actually been implemented, some new problems have to be solved during construction, some of which are similar to other breeder reactors .

  • The reactor works at approx. 550 ° C (approx. 820 K) with relatively high core temperatures (see light water reactors work at 330 ° C). This shortens the lifespan of the systems involved.
  • Due to the high material and neutron turnover, the fuel element is mechanically very stressed.
  • Due to the design, the core is not heated evenly, but in a limited zone that generates the full power of the reactor.
  • The planned sodium cooling has an inherent safety risk. For this reason, a further sodium circuit must be interposed between the primary circuit and the water-steam circuit so that only non-radioactive sodium reacts with water in the event of a leak (see breeder reactor ).

The reactor type is primarily intended for the generation of base load electricity and is therefore less suitable for covering the residual load , which remains as the difference between electricity consumption and electricity generation from fluctuating generators (especially wind and sun), than nuclear energy processes with higher process temperatures that enable the production of (storable) Enable gas fuels.

Individual evidence

  1. ^ SM Feinberg: Discussion Comment. Rec. Of Proc. Session B-10, ICPUAE, United Nations , Geneva , Switzerland (1958).
  2. ↑ MJ Driscoll, B. Atefi, DD Lanning: An Evaluation of the Breed / Burn Fast Reactor Concept. MITNE-229 (Dec. 1979).
  3. ^ LP Feoktistov: An analysis of a concept of a physically safe reactor. Preprint IAE-4605/4, in Russian, (1988).
  4. ↑ E. Teller, M. Ishikawa, and L. Wood: Completely Automated Nuclear Reactors for Long-Term Operation. (Part I), Proc. Of the Frontiers in Physics Symposium, American Physical Society and the American Association of Physics Teachers Texas Meeting, Lubbock , Texas , United States (1995); Edward Teller, Muriel Ishikawa, Lowell Wood, Roderick Hyde, John Nuckolls : Completely Automated Nuclear Reactors for Long-Term Operation II: Toward A Concept-Level Point-Design Of A High-Temperature, Gas-Cooled Central Power Station System. (Part II), Proc. Int. Conf. Emerging Nuclear Energy Systems, ICENES'96, Obninsk , Russia (1996) UCRL-JC-122708-RT2. .
  5. ^ H. van Dam: The Self-stabilizing Criticality Wave Reactor. Proc. Of the Tenth International Conference on Emerging Nuclear Energy Systems (ICENES 2000), p. 188, NRG, Petten , Netherlands (2000).
  6. ↑ H. Sekimoto, K. Ryu, Y. Yoshimura: CANDLE: The New Burnup Strategy. In: Nuclear Science and Engineering . 139 (2001), pp. 1-12.
  7. ↑ Bill Gates makes a strong wind for nuclear power in heise online from January 29, 2019
  8. ↑ Bill Gates wants to revolutionize nuclear power with mini-piles. In: Spiegel-Online. March 23, 2010.
  9. ^ R. Michal and EM Blake: John Gilleland: On the traveling-wave reactor. In: Nuclear News. September 2009, pp. 30-32.
  10. ↑ a b M. Wald: 10 Emerging Technologies of 2009: Traveling-Wave Reactor. In: MIT Technology Review . March / April 2009.
  11. ^ A b c Gilleland, John: TerraPower, LLC Nuclear Initiative. In: Spring Colloquium; April 20, 2009. University of California at Berkeley , archived from the original March 31, 2010 ; accessed on January 27, 2019 .
  12. ↑ United States Department of Energy : Depleted UF6 Inventory and Storage Locations. ( Memento of the original from August 27, 2009 in the Internet Archive ) Info: The archive link was automatically inserted and not yet checked. Please check the original and archive link according to the instructions and then remove this notice. Accessed October 2009 @1@ 2Template: Webachiv / IABot / web.ead.anl.gov
  13. ^ L. Wood, T. Ellis, N. Myhrvold, R. Petroski: Exploring The Italian Navigator's New World: Toward Economic, Full-Scale, Low Carbon, Conveniently-Available, Proliferation-Robust, Renewable Energy Resources. 42nd Session of the Erice International Seminars on Planetary Emergencies, Erice, Italy, 19024 August (2009).
  14. ^ Julian Ryall: Japan plans underwater sponges to soak up uranium , Telegraph Media Group . June 16, 2009. Accessed July 5, 2009.  (English)
  15. ↑ ML Forest: TR10: Traveling-Wave Reactor. In: Technology Review . March / April 2009. (English)