There has been a lot of hype recently about the “Travelling Wave Reactor” (TWR), thanks largely to a very popular TED talk given recently by none other than Microsoft founder and multi-billionaire Bill Gates. In the 20 min talk, he describes the urgent need for cheap, abundant, low-CO2 energy, if we are to successfully mitigate climate change (a problem he takes very seriously). One key focus of Gates’ talk is nuclear power… new nukes. To quote:
At TED2010, Bill Gates unveils his vision for the world’s energy future, describing the need for “miracles” to avoid planetary catastrophe and explaining why he’s backing a dramatically different type of nuclear reactor. The necessary goal? Zero carbon emissions globally by 2050.
The ‘dramatically different’ type of nuclear reactor Gates refers to is the TWR, and he and Nathan Myhrvold are offering some financial backing for the concept. But is it a good bet? Here is a brief summary of the technology he’s talking about:
Wave of the future: Unlike today’s reactors, a traveling-wave reactor requires very little enriched uranium, reducing the risk of weapons proliferation. The reactor uses depleted-uranium fuel packed inside hundreds of hexagonal pillars (shown in black and green). In a “wave” that moves through the core at only a centimeter per year, this fuel is transformed (or bred) into plutonium, which then undergoes fission. The reaction requires a small amount of enriched uranium (not shown) to get started and could run for decades without refueling. The reactor uses liquid sodium as a coolant; core temperatures are extremely hot–about 550 ºC, versus the 330 ºC typical of conventional reactors.
For those who are regular readers of BNC, you’d be forgiven for thinking that this tech “sounds a lot like the IFR“. Well, it is similar, in many ways, and indeed is based on many of the same principles of sodium-cooled, metal-fueled fast reactors that have been developed by Argonne Labs and others over the last five decades. But there are also some fundamental differences, and this includes some ‘features’ that may seriously limit the ultimate usefulness of the TWR. Below, in another guest post, Dr George Stanford of SCGI takes a critical eye to the TWR vs IFR comparison, and draws some interesting conclusions…
Comments on TerraPower’s Travelling Wave Reactor (printable PDF version here)
By Dr George S. Stanford. George is is a nuclear reactor physicist, part of the team that developed the Integral Fast Reactor. He is now retired from Argonne National Laboratory after a career of experimental work pertaining to power-reactor safety. He is the co-author of Nuclear Shadowboxing: Contemporary Threats from Cold War Weaponry.
We hear from time to time about the Traveling Wave Reactor (TWR) that is being developed by TerraPower, an organization sponsored by Bill Gates. The developers are keeping many of the technical details to themselves. However, from the available info about the TWR, one can make some ball-park calculations. Some assumptions are necessary, because better numbers have not, to my knowledge, been revealed. If anyone has better info, please come forward.
Fact 1: In generating 1 GWe-yr of energy, any nuclear reactor necessarily fissions about 1 tonne of heavy metal, creating 1 tonne of fission products.
Fact 2: The TWR is based on the technology of the IFR (Integral Fast Reactor), developed at Argonne National Laboratory in the ’80s and ’90s — it uses metallic fuel and is cooled by liquid sodium. In effect, the TWR is a very large IFR (in size, not in GWe) that forgoes reprocessing, storing its fission products in the used part of the core (behind the traveling wave). This pushes the disposal problem perhaps 60 or more years into the future. Unlike the IFR, the TWR does not completely burn its fuel, and leaves behind a mixture of transuranic actinides — which perhaps eventually could be recycled (not clear).