Robert Socolow, Alexander Glaser, and M.V. Ramana have led efforts to assess the challenges and benefits of negative emissions strategies and new nuclear technologies.


Prospects for direct air capture of CO2

IA major focus of Robert Socolow and colleagues in 2012 was bridging the gaps between various stakeholders in the debate over the mitigation potential of carbon dioxide removal (CDR) from the atmosphere. The previous year’s publication of an American Physical Society Report co-chaired by Socolow and bp’s Michael Desmond suggested that air capture costs would be ~$600/ton CO2 , much higher than previously suggested by CDR proponents. In a paper written with report co-authors Marco Mazzotti and Renato Baciocchi, Socolow and Desmond this year updated the cost estimate using an optimized design, but costs were reduced by only 7%. In light of these findings, Socolow attended a meeting of major players in the field of air capture in March and emphasized that CDR will only make sense after the majority of large-scale CO2 sources have been decarbonized, and encouraged participants not to allow audiences to infer that humanity can “solve” climate change while being relaxed about fossil fuels.

Socolow and Massimo Tavoni were also instrumental in assembling a compendium of papers on CDR strategies that will be published as a special issue of Climatic Change edited by Michael Oppenheimer. The issue provides an original and self-contained assessment of the role of negative emissions by bringing together leaders of the integrated assessment community with experts on technology, natural science, and political science. Socolow and Tavoni wrote the introductory article for the issue, and worked with the journal to make it available to the public free of charge.


Re-engineering the nuclear future

Two years after the Fukushima accident, many countries around the world continue to consider an increasing role for nuclear power. An important component in future nuclear installations will likely be a new generation of small modular reactors (SMRs), with power outputs of 100 to 300 MWe , being developed in several countries. These reactors are expected to cost significantly less than current gigawatt-scale reactors and thereby address some of the economic challenges faced by utilities interested in constructing nuclear power plants.

The main focus during the past year of the Re-engineering the Nuclear Future project led by Alexander Glaser and M. V. Ramana has been to estimate resource requirements, waste generation, and proliferation risks associated with SMRs of different kinds relative to current light-water reactors. Their computer simulations show that SMRs based on light-water reactor technologies have a significantly higher uranium and enrichment demand, which could affect fuel-cycle choices in some countries. In contrast, SMRs with long-lived cores based on fast neutrons have substantially lower uranium and enrichment demand, and produce a smaller volume of waste relative to both conventional and small light water reactors. However, all SMRs examined so far produce substantially greater amounts of plutonium per MWh of electrical energy generated than conventional reactors.

Due to the larger amounts of plutonium generated, the results of a probabilistic model of proliferation applied to SMRs suggest that if a fleet of SMRs is deployed with the same efficiency of safeguards, it would have a somewhat increased proliferation risk compared to a fleet of gigawatt-scale reactors generating the same electric power. This finding highlights the importance of “safeguards-friendly” design choices for SMRs and, ideally, new fuel-cycle architectures to reduce these risks.

Figure 22. Basic resource and fuel requirements for a currently standard light-water reactor (1000 MW(e)), five small modular LWRs (iPWRs, 200 MW(e) each), and five notional SMRs (200 MW(e) each) with long-lived cores. Significant differences to the reference case are highlighted (increases in red, reductions in green). All numbers are scaled to a power generation of 1000 MW(e) for 9000 effective full-power days (e.g. 30 years, 300 days per year).

Glaser and Ramana have been involved in analyzing several policy issues for SMR licensing critical to determining the economic viability of these reactors, including security requirements, insurance and liability arrangements, and the size of the emergency planning zone. In future work, they will be analyzing the concern that the promised safety enhancements in SMR designs could be “offset” by a simultaneous relaxation of licensing requirements, e.g., by siting SMRs closer to urban areas.

As part of the Re-engineering the Nuclear Future project, the researchers are also engaging students on research related to the project. Edward McClamrock (MAE, Class of 2013) is writing his Senior Thesis on Molten Salt Reactors and the potential of thorium fuel, which has been considered as an alternative to uranium because it is much more abundant. Similarly, as a recipient of a PEI/ STEP fellowship, David Turnbull (PhD candidate, MAE) examined the “option value” of fusion energy for low-carbon energy scenarios. We are collecting these results to make them available to a broader audience on our website dedicated to the Re-engineering the Nuclear Future project (http://


Wind catch-up in China

Working with Robert Socolow, Nicolas Lefevre has completed a Ph.D. thesis on technological “catch up” as illustrated by the rise of the Chinese wind turbine industry. Lefevre’s hypothesis is that firms in a developing country can develop the capability to compete at a global technological frontier previously dominated by industrialized country firms, provided the developing country enables its domestic firms to pursue coherent and long-term strategies and provided the frontier is not evolving especially rapidly. The thesis zeroes in on the windpower industry in China, where the catch-up process is nearly complete (Figure 23). Firm-level analysis for Chinese windpower developers reveals rapid passage from an initial period of learning from western firms to a period of strong government support for dramatic expansion into large domestic markets. At the same time, the wind power frontier was evolving relatively slowly due to limited early support from the governments of industrialized countries, which facilitated the process of technological catch-up by Chinese firms.

Figure 23. Cumulative and incremental installed wind power capacity by country from Lefevre (2013).