What is Traveling wave reactor?

Enriched uranium-a compound high in the radioactive uranium-235 isotope-has long been the fuel of choice for civilian nuclear reactors.

But traveling wave reactors (TWR) currently being designed could convert less rarified radioactive materials into fuel.

The traveling wave reactor stands apart because it will use waste uranium as its basic fuel, amplifying the basic fuel supply by 10. The completed reactors should also be able to extract large amounts of power from other “non- optimal” fuels, including unrefined natural uranium and thorium.

The traveling wave reactor is an incredibly exciting new design that could really advance the nuclear energy field. This nuclear reactor can extract far more energy from uranium than the conventional ones. The concept is for a reactor core that transforms a common, cheap form of uranium into reactor fuel, much the way a candle flame melts the wax that it will later burn as a liquid.

Existing commercial reactors run on uranium that has been enriched to raise the proportion of uranium 235, the type that splits easily and gives off neutrons, the subatomic particles that sustain the nuclear reaction.

With the traveling wave technology, the reaction would take place in only a small region of the core at any given time. It would start on one end, which would have a layer of enriched uranium; the remainder would be uranium 238, the hard-to-split form, which often ends up as nuclear waste.

When the reactor begins operating and throwing off neutrons, some of those would be captured by the uranium 238 and would then be transmuted into plutonium 239, a good reactor fuel. The reactor would use sodium rather than water to carry away the heat it produces.

Because it would make use of the uranium 238, the reactor could extract 40 times more energy from uranium than do existing designs. Existing reactors also make some plutonium as they operate, but they do not come close to using up the uranium 238, as the traveling wave design would.

Plutonium is usable in bombs, but because it would be produced bit by bit, the reactor would not be attractive to a bomb maker and therefore would be unlikely to contribute to nuclear proliferation.

If nuclear power becomes a major global energy player in future decades, bolstered by strong growth in energy demand and a need to limit carbon-dioxide emissions from burning fossil fuels, more efficient use of uranium will be needed.