The promise of carbon-free, reliable energy means that nuclear power is still touted by some quarters as the panacea to the world’s energy needs. Once the domain of governmental players, private companies have brought much needed innovation as they seek to realize the potential of nuclear energy and fusion in particular, otherwise known as “building the sun in the box." However, the usual and very valid caveats remain; the disasters at Chernobyl and Fukushima are not just reputational stains but highlight the volatile nature of nuclear power (fission in particular) and whilst scientists have been chasing the dream of fusion for decades, there are currently no concrete signs it can scale to an industrial level in the near term. Additionally, the rise of renewables is making the business case for nuclear even more difficult. Innovation, maybe through small scale, modular nuclear, is therefore vital for keeping the technology relevant.
A total of 448 nuclear power reactors were in operation at the end of 2017, and a total of 59 reactors are under construction around the world1. The global generating capacity of nuclear energy was 392 gigawatts (electrical) (GW(e)) at the end of 2017, equivalent to about 15% of global electricity generation capacity and decreasing relevance towards 2050 due to the rise of solar and wind2 .
Talking about nuclear power generation today, most people have utility sized plants in mind and mostly neglect the smaller reactors, most of them used onboard navy ships. Importantly, all of the currently operating reactors use the fission process (splitting an atom into two) to generate energy. But there is a second nuclear process called fusion (combining two atomic nuclei into one) which is the nuclear process of our star, the Sun. These are opposing processes and therefore very different.
With recent advances in design and manufacturing, but also business models, interest in small and medium sized or modular (fission) reactors (SMRs) has been increasing, due to their anticipated ability to meet the need for flexible power generation for a wider range of users and applications and possibly replace ageing fossil fuel-fired power plants3. Some designs also promise enhanced safety performance through passive safety features, might use radioactive waste from other reactors as fuel, offer better upfront capital cost affordability and are suitable for cogeneration and non-electric applications. These reactors are designed to be built in factories and shipped for installation. There are about 50 SMR designs and concepts globally4.
The molten salt reactor (MSR) is one design of the next generation of fission reactors and it offers passive safety features, making runaway safety events unlikely or even impossible. For some designs the fuel and the coolant are the same fluid, so a loss of coolant removes the reactor's fuel. With an MSR using the Thorium fuel cycle, nuclear waste is much reduced and the radioactivity of the resulting waste also drops down to safe levels after a few hundred years. This has sparked interest and a number of startups5 are developing mostly small MSR designs.
In parallel to the construction of the first large fusion reactor ITER6 aiming to begin Deuterium-Tritium operation in 2035, a group of startups is working on small fusion reactors, again taking advantage of progress in design and manufacturing as well as available venture capital. Fusion reactors will be inherently safe, produce little radioactive waste and have very low fuel cost (the main fuel, Deuterium, exists abundantly in the Earth's ocean: about 1 in 6500 hydrogen atoms in seawater is deuterium); making them tremendously attractive as future sources of energy. In contrast to fission reactors, quite some amount of energy is needed to operate a fusion reactor and till today, net positive energy was not demonstrated with any fusion reactor.
Current fusion reactor designs differentiate mainly on how the fusion condition with high plasma density and temperature for a sufficiently long confinement time can be achieved. In magnetic confinement designs, the density is very low, meaning that useful reaction rates require the temperature and confinement time to be increased. The best known design is called Tokamak, employing a toroid that holds the plasma, and ITER is by far the largest example of this type, with about 50 experimental tokamaks operating today7. In inertial confinement designs, higher densities result in very small confinement time needs. Fusion is ignited by laser or x-rays and the largest reactor is called the National Ignition Facility8 (NIF), located at the Lawrence Livermore National Laboratory in Livermore, California. There are also hybrid designs like, for example, magnetized target fusion which uses intermediate plasma density and confinement times, while plasma temperature is achieved with inertial compression. The startup General Fusion9 has an advanced design in this category and is the only one with a plausible way to harvest the energy.Opportunities and market impacts
With the climate crisis coming to the forefront of society’s attention, electricity generation with zero green house gas emission needs to ramp up in capacity. Renewables like solar and wind are predicted to grow exponentially over the next decades and replace existing thermal power production because they are more economically attractive. Recent estimates on levelized cost of energy (LCoE) provided by NREL10 show the changes in prediction over time for the main electricity generation plants. While LCoE for solar and wind generated electricity has dramatically fallen, cost for advanced nuclear fission systems have been almost constant, underlining the competitive situation for new small scale nuclear reactors. However, if the capital cost, which is the main contributor to nuclear’s high cost, could significantly be reduced then it could be possible to compete with renewable energy prices.
Small scale also means lower investment and with factory manufacturing style faster deployment, making it capital costs significantly less. Small scale nuclear is also attractive to consider as replacement for small utilities running on gas and for remote installations. Other possible areas are desalination plants, hydrogen production plants and mobile application such as, for example, ships, offshore units, large floating multiuse platforms and potentially space vehicles.Risks and uncertainties
Even if small scale nuclear could solve the inherent cost issues currently preventing nuclear to compete with renewable energy, a number of challenges remain to be solved. Societal acceptance of nuclear power plants is certainly low in some countries, following the nuclear accidents at Chernobyl (1986) and Fukushima (2011). In addition, long term safe storage of nuclear waste is not considered to be available. Therefore, building larger numbers of new nuclear power plants is today limited to few countries, namely China, India and Russia. However, if there was a significant technological advancement, maybe from one of the private equity funded fusion projects, the prospect of carbon free, reliable electricity may cause attitudes to change.Contributors
Main author: Pierre Sames
Contributor: Mats Rinaldo; Frank Børre Pedersen
Editor: Peter Lovegrove