The nuclear future and the changing technology

The Innovation Imperative

 

The majority of today’s nuclear fleet will complete their tenure within the coming decades. As it does so, categorically dismissing nuclear energy technology means abandoning 50 years of collective experience, just as the world’s demand for energy has never been greater – and coal-based. We believe that nuclear technologies are currently evolving in the direction of increased simplicity and safety, and by doing so nuclear energy has the potential to overcome traditional shortfalls of highly uncertain costs and unknown risks.

The uneven history of nuclear energy, especially in the United States, has been due in large part to the growing pains of a new industry combined with those of a new nuclear regulator.  The development and maturation of nuclear regulatory requirements led to design changes in nuclear plants, which were often conceived and implemented “on the fly”, because they occurred after construction of a plant had already begun.  These design changes commonly took the form of increased numbers and types of backup systems, increasing the complexity of nuclear power plants.  The result of these growing pains was an immense escalation in nuclear costs and construction schedules, which was further compounded by an attempt to build larger and larger plants to generate economies of scale.

Countries such as France, Japan, and Korea were able to learn from the U.S. example and avoid many of these growing pains, allowing their nuclear programs to be far more successful at keeping costs low and construction schedules short.  Nevertheless, the legacy of this initial expansion of nuclear energy in the ‘60s and ‘70s has been nuclear energy systems that are massive, complex, and with uncertain safety, as highlighted most recently by the March 2011 nuclear accident at Fukushima.  Today, technological innovation has the opportunity to reverse this legacy, through the development of simpler nuclear systems that are available in many sizes and hold much stronger claims to safety.

Of the many innovative technologies currently under development and deployment, four categories of them are highlighted here: advanced light water reactors, low pressure coolants, breeder reactors, and small modular reactors.  Each of these technologies has the potential to allow nuclear reactors to play a greater role in supplying energy that is pollution free, carbon free, and fully sustainable.

The first set of technologies, advanced light water reactors, are also referred to as Generation III and Generation III+ reactors.  These systems, perhaps the best known of which is the U.S. designed Westinghouse AP-1000, represent a shift toward simpler and more reliable safety systems than used in previous reactors.  They place greater reliance on “passive” systems that require no external power or pumping to operate, and instead use natural forces such as gravity, buoyancy, and heat conduction.

These advanced light water reactor designs build on the accumulated experience from the previous generation of reactors, and take advantage of new probabilistic risk assessment techniques that show which design choices make the greatest contributions to safety.  Because of their use of simpler passive systems, the probability of a core-damaging accident occurring is estimated to be one hundred times less likely in this newest generation of reactors.  Perhaps more importantly, these new reactors are designed to automatically remain safe without any operator action or sources of external power, which makes them much better safeguarded against events such as major natural disasters.

Advanced light water reactor designs are currently being built for commercial operation both in the U.S. and around the world.  Meanwhile, new reactor designs based on low-pressure coolants are being actively developed.  These reactors are part of a group of Generation IV reactor designs, which use new technologies to try and improve the safety, sustainability, cost, and proliferation resistance of nuclear energy.

Unlike water-cooled reactors which must operate under pressure in order to reach high enough temperatures, low-pressure reactors use coolants such as liquid metal and liquid salt which remain liquid even at very high temperatures.  Operating at low pressure has two advantages: first, it becomes much less likely for a leak to cause coolant to be lost, and second, it is easier to remove heat from low-pressure liquid coolant than from high-pressure boiling water. The result is that these low-pressure reactors can be designed to be even simpler than light water reactors for a given level of safety, improving their cost and reliability.

Major efforts to develop and deploy these reactors are proceeding around the world, including sodium-cooled reactor projects in the U.S., France, and Korea, and salt-cooled reactor projects in the U.S. and in China.  The U.S. in particular is well positioned to take the lead in development of such systems, due to the depth and diversity of its nuclear energy experience, and the strength of its national labs, universities, and private enterprise.

Two more categories of nuclear technologies are worth mentioning: small modular reactors (SMRs) and breeder reactors.  Both are classes of nuclear systems that are under active development and offer distinct benefits.  Breeder reactors are reactors that can convert abundant non-fissile isotopes of uranium and thorium into usable fuel, allowing several hundred times more energy to be extracted from uranium and thorium resources, which makes them important for sustainability over very long timescales.  SMRs are smaller-sized reactors (typically under 300 MW electric) that are important for several markets:  economies with low load growth like the U.S., and emerging or remote markets with poor grid capacities.

While the economic competitiveness of SMRs has yet to be demonstrated, potential advantages include increased simplicity due to lower power ratings, reduced project costs and durations, as well as reduced uncertainties in cost and construction time due to a greater degree of factory fabrication. Advanced safety characteristics mean that SMRS can also be sited on decommissioned coal plants sites, greatly streamlining the grid connection process and obviating the need for new transmission upgrades elsewhere in the system. As a result, SMRs are attracting major attention from government and industry, for example with the U.S. DOE program offering technical and financial support for developing, licensing, and deploying SMRs. With federal support, the Tennessee Valley Authority (TVA) contracted the purchase of up to six 180MW mPower SMRs over the next decade from Babcock and Wilcox Company.

With the exception of advanced light water reactors and low-pressure reactors, which use different coolants, none of the above technologies is mutually exclusive.  This means that one can have an advanced light water reactor that is also an SMR, or an SMR that is also a low-pressure breeder reactor.  Each of these combinations has a wide range of technical options associated with it, representing a space of relatively unexplored ideas that is enormous in size.  It is particularly within this space where nuclear energy has the opportunity to improve upon its historical legacy and provide an improved alternative to increased consumption of fossil fuels.

Carbon is the Enemy

We hold no reservations in saying that nuclear power has and will have drawbacks. Moreover, scientists, regulators, and investors alike have made mistakes protecting public interests – in some cases, tragic mistakes, which have rightly shaken public trust in the energy industry. History teaches us that as fallacious — and in some cases, malicious — as technology forecasting can be, equally dangerous is ludditism. Categorically dismissing nuclear technologies assumes that unlike all other energy technologies, nuclear cannot evolve with ever-changing market, safety, and other priorities. Yesterday’s nuclear power might be ill-suited for tomorrow, but the nuclear energy story is far from over.

Climate change means that carbon is the enemy. We do not believe that the promise of nuclear power comes at the exclusion or underestimation of the immense contributions that renewables and/or other low-carbon technologies will make to our common energy future. Just as innovation continues to shatter renewables’ unfortunate legacy as expensive and impractical energy technologies, the same is happening for nuclear technologies. We should celebrate the hard-fought expansions of our low-carbon energy toolbox while vigilantly adding to it.

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