Has Bill Gates come up with a safe, clean way to harness nuclear power?

Move over Monty Burns, Bill Gates is coming. Not content with creating the software empire that we all love to hate today, the Microsoft billionaire is intent on turning the seemingly Simpsons-esque world of the established nuclear industry upside down as well, and in so doing, like any revolutionary, earning the enmity of those in his wake.

With a fellow Microsoft man, former chief technology officer Nathan Myrhold, Gates is betting that a small Silicon Valley-style startup called TerraPower just down the road from Microsoft HQ in Washington state can deliver a radical reactor design known as a travelling-wave reactor. If it works it could provide humanity with the same elusive – and some say impossible – cocktail of safe, limitless, cheap and carbon-free energy that fusion promises but never delivers.

This multimillion-dollar project isn't merely a case of West Coast dreaming. TerraPower has been working with more than 24 partners from around the world to develop a design for the reactor to meet its "aggressive timescale" to break ground on the prototype by 2015–16 and begin operations in 2020–21. As well as working with the Massachusetts Institute of Technology on the design, TerraPower has discussed a deal with the Russians to test equipment for the new reactor in their own experimental reactors, as well as Japan's Kobe Steel to develop its metal casing. Although TerraPower hasn't yet finalised a deal with a country to host the prototype, nuclear-friendly – cynics would suggest regulation-lite – countries such as China, Russia and India are in the frame.

For Gates and Myrhold the travelling-wave reactor "isn't a piece of kit they want to hawk around the world" but "a solution to a problem" for the whole world, according to TerraPower's chief executive John Gilleland, whose experience of the industry stretches from solar to fusion power. "Bill, Nathan and others were sitting around back in 2006 thinking about how to provide the kind of conditions in the world that... would help them have the biggest impact on people's lives. Out of that discussion came the idea of pushing further a design that had been first thought of back in 1958. New eras mean that you can look at some of the same technology and make it work – after all, governments have spent billions of dollars on nuclear research since then."

Scientists from around the world also saw the potential for this design and had regularly revisited the idea since its conception in the US back in the Fifties. The Dutch, Japanese and Ukrainians are among the most recent to be attracted by its promise of cheap, sustainable, zero-carbon electricity produced by using the nuclear waste from the current generation of reactors. Just the waste that already exists in the Paducah nuclear storage facility in Kentucky could power the entire US for more than 1,000 years – before you even get started on the years of waste still to be produced. It is also a reactor that will, in effect, refuel itself, coming with all the fuel it needs already in its core to last its lifetime of 30 or more years; by comparison, a conventional reactor requires fuel to be shipped in every 18 to 24 months and the radioactive waste to be taken away. As a result, there is no need to build the fuel-reprocessing facilities (not for the lifetime of the reactor, anyway) that often provide cover for attempts to build WMD.

The outside of the travelling-wave reactor will be similar to today's reactors, but the inside is radically different. A conventional nuclear reactor depends on enriched uranium to generate its heat and electricity, but the travelling-wave reactor uses only a small amount of highly enriched uranium (U-235) to kickstart fission and a slow-moving chain-wave reaction. Two parallel waves of fission then move about a centimetre a year, splitting uranium atoms of the spent nuclear fuel (reprocessed uranium) or unenriched uranium (depleted uranium, U-238) packed into the core, in a process that first creates plutonium-239 and then consumes it. This reaction should be much more efficient than a conventional reactor and, in theory, can be sustained for decades.

The struggle to produce a design that is more efficient and straightforward to build has led to a change in the reactor's shape. Out has gone the original distinctive cigarette shape that the waves would travel along and in has come a more conventional-looking spherical "standing-wave reactor", where the wave stays at the centre of the reactor and it is the fuel that then travels relative to it. As a result of this change, the fuel has to be shuffled more like a conventional reactor to ensure there is enough to keep the wave going, although still in a much more simplified way. Unlike a more traditional reactor where electricity is needed to pump water around the core to cool it and prevent the kind of meltdown seen at Fukishama earlier this year, the travelling-wave reactor has a number of passive safety features – such as the use of molten sodium as a coolant, which takes much longer to boil than water, or even just the lower temperature of the core itself that makes such an event much less likely to happen.

But TerraPower's technical director is the first to admit there are serious challenges standing in the way. After 40 years in the nuclear industry, Roger Reynold was persuaded to come out of retirement by the mission and vision of TerraPower. "People will be sceptical and think that if this is so possible, why wasn't it built before?" he says. "The real reason is: material – what materials can exist for 30 to 40 years in that environment? Even today nobody has tested steel to the kinds of limit we are contemplating. So the fundamental mission of the prototype is to collect real data. We intend to build in countries which are used to fast reactor technology so we can more quickly demonstrate that the process works."

However, Tom Blees, a pro-nuclear environmentalist, and others say the travelling-wave reactor gets undue attention from being Gates's baby. Blees, who is author of the critically acclaimed Prescription for the Planet and president of the Science Council for Global Initiatives as well as an advocate for an alternative design of reactors, says: "When I first heard about the travelling-wave reactor, it sounded like Bill and Nathan had been sitting around smoking something when they came up with this cool idea of a reactor that will never need to be refuelled as it will burn like a cigarette for 60 years. Now the problem is that such a slow steady burn is hard to achieve, as nuclear fission isn't like a cigarette, it's a kind of random process; so they keep having to modify it and in the end they are going to end with up with an integral fast reactor."

Ian Hoare-Lacey, director of communications for the industry group the World Nuclear Association, accepts that there is no one else he knows like Gates "who is putting their own money into reactor design", yet "we are not holding our breath for it".

Hoare-Lacey says "it sounds like a nice idea but it has considerable problems, such as extracting heat from the reactor and the size of the core". He says the "further away you move from pressure water reactors, the higher the barriers to regulatory approval are" and that "these kinds of design haven't been executed well in the past due to lack of adequate materials". But "better materials may help realise the potential of these back-of-the-envelope designs", he adds.

Similarly, Dr Doug Parr, chief scientist from Greenpeace UK, believes "a little bit of scepticism is worthwhile... and as far as I can see cost, waste, safety and proliferation are still big issues. You could argue that new reactors are safer, but it is actually impossible to know in the lab. A lot of nuclear waste is also a real mess. It is rarely pure, especially the older waste. So if you effectively accelerate the fission of some of the more problematic elements in a reactor you might have real problems".

In the end, for Gilleland, "it isn't a slam dunk that it is going to work" as it is a "high-stakes, high-reward" kind of project. The scepticism doesn't surprise him either. "The fission community is a is very conservative bunch of people who are often uneasy with things they haven't thought of themselves and can think too much in terms of what you can do right now, although scepticism is part of life and should be focused on something so radical," he says. "After all, if there was no scepticism towards us then we would be doing something wrong."