An intriguing concept in new nuclear energy technology, so-called ‘travelling wave’ technology, has recently received a publicity boost from Bill Gates. Already associated with the concept through his TED talk in 2010, Gates’ backing of TerraPower LLP lends strength to its engagement with Chinese representatives, which aims to pursue the first full-scale implementation of the technology.
‘Travelling wave’ reactors (TWRs) are variants on the ‘fast breeder’ reactor concept. Instead of traditional designs, TWRs are designed to operate with minimal refuelling and enrichment. After an initial fuelling, the design of the reactor incorporates a ‘wave’ of fission, with non-fissile material gradually converted into fuel as the reactor runs. Among several advantages, this means that the reactor could run off depleted radioactive material such as Uranium-238.
The end result, if successful, would be a TWR with a smaller ‘footprint’ (probably one-fifth to one-tenth the size of existing reactors in terms of power generation), but with far fewer concerns about fuelling. This, in turn, helps to reduce operating costs and security concerns, with a much lower volume of transported materials and fuelling operations required. In theory, a perfected TWR design could operate for over 100 years before refueling or retirement. This would allow construction of TWRs on a more modular basis, distributing generation as required, and minimizing dependencies on transport infrastructure.
Critics note, however, the inherent difficulties of existing TWR designs. At present, liquid sodium is proposed as a coolant, which would appear to open TWRs to the same risks as other liquid-metal designs. One such design, in Monju, Japan, has barely operated since completion, due to a serious leakage of sodium that – after reacting with oxygen – created a major fire. The subsequent actions taken to try to manage the incident, including incomplete information being pubilshed by the responsible agency, and further problems attempting to re-start the reactor, have left liquid-metal-cooled designs with a decidedly mixed reputation.
These challenges, and others relating to safety, sustainability, and the lack of a proven design, will continue to be raised as TWR technology progresses from concept to prototype. Nevertheless, with clear advantages over more traditional methods of nuclear generation, the industry will be watching developments at TerraPower very closely over the next few years.
Posted by Ben Thacker on the 5th of January 2012
