Greenhouse gas (GHG) emissions from anthropogenic sources, more specifically emissions of carbon dioxide (CO2) through energy intensive processes, are predicted to accelerate on a non-linear trend that began at the onset of the Industrial Revolution in the 19th century. The growing concentration of CO2 from the combustion of fossil fuels has begun to warm the atmosphere, and beginning only a few decades ago, society became aware of not only the presence of more GHGs in our atmosphere, but also became conscious of the implications with respect to human civilization. Several different sources of renewable energy have become popular and are marketed as substitutes for fossil fuels, such as photovoltaics and wind. However, these sources are still largely too expensive to be adopted by utilities that have traditionally provided their customers with a pricing structure rooted in cheap electricity from coal. Compared to these renewable sources, nuclear power generation has some advantages that humans will have to rely on in the coming decades while manufacturing processes are optimized to make solar, wind, and battery technologies more economically viable.
If there is one historically unifying theme for nuclear power, it is that it seems to have been consistently under-utilized. 439 nuclear reactors are in operation today, in thirty countries, with only fourteen of those countries generating more than 20% of their overall electricity consumption with nuclear. Only three countries, Hungary, Slovakia, and France use nuclear sources to provide the majority of their electricity (IAEA 2015). This trend seems to be due to several different factors, the first of which being the relatively high capital and financing cost of constructing a new nuclear power plant, coupled with long construction time scales. The upfront capital required for a nuclear plant is higher than any other energy generation technology with the exception of offshore wind power and coal-gasification integrated combustion cycle (IGCC) with carbon capture and storage (CCS). Total overnight cost, which includes engineering, procurement, and construction costs, but also excludes interest on financing, came to $671/kW for modern combustion turbine designs that utilize coal as fuel. This is in very stark contrast to modern nuclear reactor installations that have recently averaged $5,366/kW total overnight cost in the United States (U.S. Energy Information Administration 2015). It is easy to see why utilities prefer traditional fossil fuel plants with such a substantial difference in upfront costs, but this is only a piece of the story.
Compared with every other energy generation technologies, a new nuclear plant takes longer than any other installation to bring online without even considering regulatory or political roadblocks. While a conventional coal or gas plant could be completed in about three years from date of order, a nuclear plant is expected to take about eight years (U.S. Energy Information Administration 2015). Add to this the nearly unanimous tendency for nuclear projects to be delayed while still under construction, and you have a nuclear plant that in some cases ends up costing 75% more than initially estimated (World Nuclear News 2014). This is a tremendous investment risk for private investors, governments, or utilities, and has consistently made the estimation of plant cost wildly unpredictable. Delays on nuclear projects are so common that a project being completed on time has become the exception rather than the rule.
Capital and financing issues are not the only problems with trying to bring new nuclear online. Beginning with the first major nuclear accident in Chernobyl, nuclear has been characterized as being unacceptably dangerous in many countries around the world. There have been countless public demonstrations against nuclear power, with every subsequent nuclear accident revitalizing public opposition and sparking mass protests throughout the world. The meltdown of three reactors at the Fukushima Daiichi power plant in 2011 is classified as the second worst nuclear accident in history and has resulted in a massive international response, despite no deaths having been attributed to the disaster at this time. Most notably, Chancellor Merkel of Germany made a commitment in the days that followed the Fukushima accident to accelerate the decommissioning of all of Germany’s nuclear reactors (Reuters 2011). It is also estimated that this disaster alone will result in only half the previously estimated new nuclear capacity by 2035 due to public concerns, though some of the major markets such as India and China are expected to proceed with earlier plans to vastly increase their share of nuclear power capacity (The Economist 2011). China has since reiterated its commitment, with a planned completion of 129 new reactors by the year 2030 citing considerable public health concerns with air quality in major population centers, as well as an increasing international focus on the mitigation of CO2 emissions (Forbes 2015). Nuclear disasters have been a regular source of waning interest in the nuclear sector for decades now, but there does seem to be momentum in the industry. Nuclear electricity generation is a very effective way to offset CO2 emissions, and the politicians know this, but the public is cautious. Just as the Ukrainian ghost town of Pripyat was contaminated with radioisotopes after the meltdown at Chernobyl, the phrase “nuclear power” has been contaminated with ideas of apocalypse and catastrophe. There must be a relentless focus on improving reactor technical safety and redundancy, as well as improving human safety protocol and inspection measures to reassure the public that this technology is overwhelmingly safe when compared to other forms of energy generation.
The issue of nuclear waste handling has been a source of contentious debate for decades, and will likely continue well into the future. Traditionally, many countries treated all of the spent nuclear fuel as waste; despite the spent fuel containing only <5% undesirable actinides and fission products. This “spent” fuel can be reprocessed to separate the undesirable contents from the portions of uranium and plutonium that are still valuable, but because reprocessing this fuel requires relatively expensive infrastructure and new nuclear fuel is relatively cheap, it has never been in the economic interests of a company or government to build a fuel reprocessing plant. Despite this, many countries have done just that, partly to reduce fuel costs by recycling the spent fuel, but also because reprocessing makes waste disposal much easier by concentrating the dangerously radioactive waste into a smaller volume. The United States has had a very lackluster history with regard to nuclear waste disposal, choosing not to reprocess spent fuel and also to simply store it in sealed “dry-casks” above ground (Hashem 2012). This is a very inexpensive method of disposal, but many argue is unsustainable and presents unacceptable levels of risk to the public.
If humanity is to rely on nuclear power to a greater extent in the future, the nuclear fuel cycle must be normalized among countries to create continuity, consistency, and predictability. This would involve a commitment by every country with nuclear capacity to extract the most radioactive actinides from spent fuel to reduce the volume of waste, and then permanently “freeze” this waste in an insoluble compound such as borosilicate glass or synthetic rock. This ensures that if this high level waste were to ever come into contact with water, it could not leach out and pose a health concern. Countries with nuclear capacity also need to normalize the way in which they ultimately dispose of this high level waste after reprocessing. Projects are underway in several different countries at this time to develop geological repositories up to 500m deep, well below the water table in a majority of the world (World Nuclear Association 2012). These repositories must be subject to several constraints, including but not limited to proximity to population centers, proximity to aquifers, and geological stability. This strategy provides multiple layers of protection against an accidental radiological release into the biosphere, and seems to be the best nuclear waste policy at this time. It is likely, though, that the populations of people closest to these sites will be vehement opponents of this disposal process, making it politically difficult to implement.
RENEWABLES AND NUCLEAR
There are no CO2 emissions associated with producing electricity at a nuclear power plant, and also no harmful emissions like mercury or sulfur that are produced when burning coal. An estimated 60 GW of coal capacity is estimated to be retired by 2020 in the United States with the advent of new Mercury and Air Toxics Standards (MATS) that requires “significant reductions in emissions of mercury, acid gases, and toxic metals,” and the Clean Power Plan that limits CO2 emissions by plant type (U.S. Energy Information Administration 2014). This means that it is currently advantageous to begin planning base load replacement in the form of nuclear plants. Because an average sized coal plant in the United States has a capacity of 250 MW, and an average sized nuclear plant has a capacity of just over 1 GW, the net effect to overall grid capacity would be insignificant if society were willing to invest in one nuclear plant for every four coal plants that closed. Coal provides about 30% of the United States power, and a good starting point for a long term CO2 mitigation strategy would be to aim to replace all coal power with nuclear sources, leaving the last 70% to ultimately be entirely comprised of wind, solar, and hydroelectric capacity (U.S. Energy Information Administration 2013). For every 1 GW of coal capacity replaced by nuclear capacity, on average, 4 MtCO2 is avoided per year. Hypothetically, if all coal capacity in the United States were replaced with nuclear, 1.38 GtCO2 would be avoided annually; equivalent to 4.27% of global CO2 emissions (Davis and Socolow 2014).
There is no doubt that renewable energy sources must play a substantial role in the future, but nuclear must still be a critical component of the world’s electricity generating capacity for many years to come. There are several reasons for this, with the first being that the nature of wind and solar power is inherently intermittent. Wind power output can usually be assumed to be equivalent to the turbine operating at 100% capacity for 2,200 hours per year, and for most of the United States, solar can be assumed to generate electricity for about 2,400 hours per year (Landsberg and Pinna 1978). This is in contrast to coal, natural gas, and nuclear plants that can be assumed to operate around 8,000 hours per year, with the only downtime being for maintenance or when electricity demand falls to a point that utilities would lose money by keeping a plant operating. What this means is that there must be a great deal of innovation in the energy storage sector to store power generated by wind or solar for use at night or when the wind is not blowing, likely in the form of lithium ion batteries, or it means that we must supplement a renewable energy system with plants that we have the ability to turn off and on. Because advanced battery technology is still prohibitively expensive, this means that we must use nuclear in conjunction with wind and solar to provide a base load of power, support the grid in times of need, and to offset CO2 emissions.
Another disadvantage that wind and solar possess is that the electricity generation potential varies wildly from region to region, even sub-nationally. In the United States, states in the northwest such as Montana and Idaho have wind potential areas that are upwards of 1000W/m2, whereas many of the southern states like Louisiana, Mississippi, Alabama, and Florida have no wind potential at all aside from possible offshore installations, and even most of those top out at a potential of only 100W/m2 (University of Montana 2008). With solar resources, states in the southwest such as California, Arizona, and Nevada have vast portions of their states that receive over 9.0kWh/m2/day in June, while states in the northeast like New York, Pennsylvania, and Massachusetts receive in the range of 4.0-5.0kWh/m2/day, making it twice as effective to generate solar power the southwest (National Renewable Energy Laboratory 2004). The implications of this are that it would be inefficient to generate power from these renewables in the “wrong” locations, and that it would make more sense to generate in energy dense locales and transmit the power elsewhere, though this would vastly increase transmission loss. The point is that renewable energy is geographically and topographically constrained to a much more considerable degree than nuclear is. It will be necessary to locate nuclear plants in places that do not make solar or wind “sense,” with the only local requirement being some source of freshwater for cooling. This makes nuclear versatile compared to coal and natural gas as well, because coal plants are often located as close to the source of the coal itself due to transportation cost, and natural gas transportation requires expensive underground pipelines. Nuclear reactors consume a very small amount of fuel per kWh in terms of volume and weight when compared to these sources, thus alleviating many logistical concerns that the fossil fuel industry must face.
Though nuclear is undoubtedly preferable to fossil fuels for the sake of GHG emissions, we must bear in mind that uranium is a finite natural resource. The consequence of this is that nuclear power, using current infrastructure and identified resources, is a medium-term solution for energy scarcity at this time, and cannot be considered the end-all solution to energy scarcity with current reactor technology. Globally, current identified resources of uranium in all cost categories are estimated at 13.5Mt, and at 2012 rates of uranium consumption this would provide a 120-year global supply. Undiscovered resources, estimated based off of geological data and regional geographic mapping, are estimated to amount to about 7.7Mt. Based on identified resources alone, this implies that a doubling of nuclear capacity would in principle reduce this supply from 120 years worth of uranium to 60. Fortunately, relatively higher uranium prices have resulted in more exploration for new sources. Because of this, total identified resources increased 10.8% in only the two years from 2011-2013 (OECD NEA & IAEA 2014). A trend like this will do well to mitigate any concerns utilities or governments have about a uranium shortage within the next several decades. Uranium also exists in seawater at a concentration of 0.003ppm, and could potentially be extracted if land resources became difficult enough to mine. Early research suggests that if uranium prices exceed $600/kg, it could become profitable to extract from seawater (World Nuclear Association 2015).
One breath of fresh air with respect to potential uranium scarcity is the breeder reactor design, which operates in a fundamentally different manner than the widely used boiling water reactors (BWR), pressurized water reactors (PWR), and CANDU reactors. The advent of the nuclear era brought with it the idea that uranium was a scarce element, which directed focus to research on new reactor designs that could more efficiently extract energy from the fuel. This is the primary benefit of a breeder reactor, superior fuel economy when compared to conventional designs. Breeder reactors achieve this by not “moderating” the neutrons produced in fission, which is the role of water in nearly all reactors currently in operation. The presence of water slows the neutrons and makes them more apt to be captured by and split fissile nuclei like 235U, and also less likely to be captured by the non-fissile 238U that comprises a majority of the nuclear fuel. Without a neutron moderator, the neutrons possess a much higher energy, allowing them to more easily be captured by the non-fissile 238U, which captures two protons and converts to fissile 239Pu. Breeder reactors can also use a thorium fuel cycle, which increases efficiency even more. The takeaway is that a breeder reactor creates its own fuel that can be reprocessed into a suitable nuclear fuel on a regular basis. Where conventional reactors can extract less than one percent of the potential energy in terms of the amount uranium ore it takes to produce a viable nuclear fuel, breeder reactors can increase this “by a factor of about 60,” (World Nuclear Association 2015). This principle in conjunction with the theoretical viability of seawater uranium extraction effectively turns nuclear fuel into a source of renewable energy.
Breeder reactors have the added benefit of addressing a large portion of the nuclear waste problem. Actinides, heavy elements that are not a product of a split atom but rather a neutron capture, are the primary source of radioactivity in traditional nuclear waste. Because of the un-moderated higher energy neutrons in a breeder reactor, these actinides become an actual part of the fuel cycle. Because of this design, a breeder reactor can theoretically burn all of these actinides and leave only lighter and less radioactive fission products. Due to geometric and physical constraints of the fuel, however, this can only be achieved with the continuous reprocessing of fuel (Bodansky 2006). The breeder reactor shows future promise, though it will likely not become popular for new installations until uranium ore is sufficiently expensive and radioactive waste storage capacity becomes overwhelmingly problematic.
How can society encourage the mass adoption of nuclear power in countries that are not yet concerning themselves with clean energy? Currently, the world powers are reluctant to assist in bringing new nuclear capacity to developing countries for various reasons, but perhaps most of all because of national security concerns. There is an undeniable risk that a nuclear power program, no matter the specifics, could provide some degree of a framework for a terrorist group or a rogue administration to develop nuclear weapons. There are possible solutions to nuclear weapons proliferation, though nearly all would be immensely politically challenging to implement because they all require some level of oversight and capacity for verification.
First, the world powers could mandate that new nuclear capacity in potentially problematic countries must be constructed using the Canadian Deuterium Uranium (CANDU) reactor design, which permits the usage of fuel without enrichment. This is important, as uranium enrichment infrastructure can essentially be thought of as the tool that enables the creation of a nuclear bomb. The CANDU design nullifies this because the reactor is designed to use heavy water, water that possesses a hydrogen atom with an atomic mass of two otherwise known as deuterium, to moderate neutron emission of the fuel. The heavy water itself will capture fewer neutrons and works in some respects similar to the aforementioned breeder reactor, enabling higher energy neutrons to be captured by the 238U which transitions to fissile 239Pu, resulting in the existence of overall criticality in the reactor without enriched fuel.
However, there are still concerns with the CANDU design. There are only a handful of heavy water manufacturers in the world, and shipping large quantities could be logistically challenging; and this is without even considering its exorbitant cost of several hundred dollars per kilogram. Also, as mentioned, CANDU reactors rely on creating much of their power through the fertilization of 238U to convert it to 239Pu. Provided a reasonable fuel reprocessing facility and scientific know-how, this 239Pu can be isolated from the rest of the waste and can potentially be used to create a nuclear warhead, assuming there are large enough quantities available. Tritium is also an incidental creation in a CANDU reactor when the deuterium atom captures another neutron. Tritium can be used to create a nuclear fusion reaction that can drive a traditional fission reaction, and greatly increases the amount of energy released when arranged in the proper way. This is what is called a “two-stage nuclear,” “thermonuclear,” or “hydrogen” bomb, and is the most powerful weapon that is publicly known to have been created. This tritium can also periodically be harvested from the heavy water in the reactor (International Panel on Fissile Materials 2013). Because this waste poses a hypothetical danger in the wrong hands, the International Atomic Energy Association (IAEA) must be able to monitor the nuclear waste produced in these countries to ensure that none is being diverted to a covert processing plant with the intent of weaponizing the material.
Lastly, the world powers could develop a global supply chain through the IAEA, whereby only carefully vetted vendors from trusted sources are allowed to enrich, manufacture, and transport nuclear fuel. This would facilitate the use of conventional and cheaper light water reactor (LWR) designs, eliminating concerns about incidental tritium production, heavy water availability, and most of the concerns with regard to the incidental production of 239Pu. In addition to total supply chain management, including nuclear waste management, there must be surveillance capacity at nearly every stage of the nuclear electricity generation process. This strategy also prevents enrichment infrastructure, which is perhaps the most important concern, but the greatest challenge with this approach is the political feasibility. A country would be required to allow a United Nations agency to essentially trample on their sovereignty by having the authority to inspect virtually any facility anywhere at any time within their borders. Requiring the countries to purchase fuel from verified vendors that are likely to exist in some other country is an additional aspect they are unlikely to find ideal. The very existence of this sort of an agreement does not particularly foster a friendly political relationship, and rests on the presumption that the new nuclear country cannot be trusted.
Assuming the later mechanics of inspection and verification process can be achieved, there is still the question of how new nuclear projects will be developed and financed. Working through the United Nations Framework Convention on Climate Change (UNFCCC) and the Special Climate Change Fund (SCCF), new nuclear proposals from developing countries or economies in transition could be refined by experts in the nuclear industry to ensure creditworthiness. The SCCF could provide lower interest debt financing compared to what the project would alternatively receive from the private sector, or use a cooperative equity model to mitigate more of the upfront costs to the recipient utility or government. Either of these strategies would help to encourage the adoption of nuclear over fossil fuel plants in countries that are expanding their energy capacity at this time, but would also ensure a return on investment for the SCCF. Also, Russia has been quietly securing contracts with other countries under a “build-own-operate” system, in which the Russian government uses their own nuclear technology to build and permanently operate a reactor in another country. This is advantageous for both parties, but has some geopolitical implications as “Russian-built nuclear power plants in foreign countries become more akin to embassies — or even military bases — than simple bilateral infrastructure projects,” (Armstrong 2015). Regardless, without the barrier of billions of dollars of upfront capital and financing costs, it is likely that nuclear projects will look more attractive to prospective countries. This is especially true when considering that nuclear is not subject to any hypothetical carbon taxes that may ultimately be introduced at a national or international level.
Nuclear power will face a multitude of challenges going forward, from political and public opposition, waste management, and lack of capital for project finance, but will nonetheless remain a technology we are to rely on if we wish to deviate significantly from the amount of CO2 we are emitting. Wind, solar, and hydroelectric power capacity will certainly be of the utmost importance over the next century, but their intermittent nature coupled with the lack of economically viable battery technology prevents us from utilizing those energy sources for 100% of global energy demand at this time. Uranium supply does not currently seem to be any significant constraint on the future of nuclear energy, and with future extraction technologies and breeder reactors, this is theoretically a non-issue for millennia. The capability of weaponizing nuclear fuel will be troubling as nuclear power is adopted around the world, but with a comprehensive monitoring and inspection process through the IAEA and United Nations, this concern can be put to rest as well. CO2 emissions must be reduced drastically, but it is up to policy makers to determine viable ways to allow developing countries to continue to experience economic growth while also making the switch to cleaner energy sources.
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