Traveling wave reactor

A run -wave reactor (English Traveling wave reactor, TWR ) is a theoretical concept of a nuclear reactor type, the fertile material to fissile material converts ( Transmutation ). The TWR is different from the fast breeder reactor in that it manages with little or no enriched uranium. Instead, it uses depleted uranium, raw uranium, thorium or spent fuel from light water reactors ( LWR) and combinations of the above. The name derives from the fact that nuclear fission does not take place in the entire reactor, but only in a specific zone of the reactor, which propagates with time through the core.

History

The idea of ​​a drive shaft reactor is from the 1950s and has since been taken up and developed over and over again. The concept of a reactor which may erbrüten its own fuel, was first explored by Saveli Feinberg 1958. Feinberg said this principle breed - and-burn ( erbrüten to German and burn ). The concept has since been taken up again and again. First, in 1979 by Michael Driscoll, 1988 by Lev Feoktistov, 1995 by Edward Teller and Lowell Wood, 2000 by Hugo van Dam, 2001 by Hiroshi Sekimoto and most recently in 2006 by the company Intellectual Ventures.

So far succeeded yet none of the aforementioned scientists and institutions to construct an executable run- wave reactor, but Intellectual Ventures founded a sister company called Terra Power, with the aim to design a commercially deployable TWR and edify. Terra Power has elaborated various designs with an output power of 300 MW and 1000 MW ≈. 2010 got the research on TWR renewed momentum after Bill Gates and also the company Toshiba announced interest in this technology.

Reactor Physics

Articles and presentations on Terra Power TWR describe a reactor similar to the swimming pool reactor which is cooled with liquid sodium. The reactor is operated mainly with depleted uranium, but requires a small amount of enriched uranium or other fissile material to initiate nuclear fission. Some of the fast neutrons generated by nuclear fission are, (eg non-fissile depleted uranium ) is converted by neutron capture in the neighboring breeding material by subsequent nuclear reaction in plutonium:

Initially, the core is filled with fertile material. At one end of the reactor core is added a small amount of fissile material. Once the reactor has been put into operation, the core is divided into four zones:

• The depleted zone containing mainly fission products and leftover fuel.
• Cleavage zone where the nuclear fission of erbrüteten material takes place.
• The breeding zone where new fissionable material produced by neutron capture.
• The "fresh" zone containing the unused nesting material.

The energy-producing fission zone moves with the times through the core. Here, the breeding material is consumed on one side and abandoned on the other side of spent fuel. The heat generated in the cleavage and breeding reaction is converted into electrical energy by conventional steam turbines.

Fuel

Unlike conventional reactors TWRS can be filled during construction with enough depleted uranium to supply energy at full power for 60 years or more. Consume TWRS related to the electric power much less uranium than existing reactors, as TWRS burn the fuel more efficiently and have a better thermal efficiency. The TWR reaches a reprocessing on the fly, without the typical for other breeders kinds of chemical separation must take place. These properties reduce the fuel and waste significantly and complicate proliferation.

Depleted Uranium is abundantly available as the starting fuel. The stocks of depleted uranium in the United States currently consist of approximately 700,000 tons. It is a waste product of the enrichment process. Terra Power estimates the value of the electricity can be generated thereby to $ 100 trillion. Company scientists have also calculated that TWRS could supply the world with depleted uranium stored 80 % of the world population with a per capita electricity consumption at the level of an average U.S. citizen over a thousand years. In addition there are about 4.5 billion tonnes of uranium, which is in dissolved form in seawater.

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

TWRS are also in principle be able to reuse their own fuel. The burnt material from the TWR still contains fissile material. By conversion into new pellets and Neuverkapselung the fuel can be re-used without chemical reprocessing in TWRS. This eliminates the need for uranium enrichment.

Possible Problems

Since the construction of the reactor has not yet been implemented in real terms, some new problems to solve in the construction, some of which are similar to other breeder reactors.

• The reactor operates at about 550 ° C ( 820 K) with relatively high core temperatures ( cf. light water reactors operate at 330 ° C). This extends the life of the systems involved is shortened.
• Due to the high material and neutron sales, the fuel assembly is mechanically very stressed.
• By design, the heating of the core is not uniform, but in a limited zone, which generates the complete output of the reactor.
• The planned sodium cooling poses an inherent security risk. Therefore interpose yet another sodium loop between the primary circuit and the water - steam cycle, so that in case of a leak only non- radioactive sodium reacts with water (see breeder reactor ).