nuclear

NUCLEAR PROLIFERATION AND LASER URANIUM ENRICHMENT

/ Tyler Pedigo / 3 Comments

To the average person, uranium enrichment is something that feels too scientifically complex to understand. People typically only hear about enrichment in conjunction with a myriad of other advanced-sounding concepts, which can be off-putting for someone who would have otherwise wished to better understand this process. However, at a fundamental level, the enrichment process is actually quite simple, with the primary objective being that we wish to separate different kinds of uranium that are mixed together when it is mined from the Earth. At face value, this does not feel like a complicated task, but these two different types, or isotopes of uranium are practically identical in every physical way except for their weight, and the fact that one isotope of uranium is fissile. One isotope is called 238U, and it is mostly useless for the purposes of energy generation or nuclear weapons, but comprises 99.284% of all uranium that exists on Earth. The other isotope, 235U, is the one that we desire, because it can produce what we think of as a nuclear reaction. This is the basis for why nuclear power plants work and the basis for why nuclear weapons that use uranium explode. However, 235U, the useful isotope, only comprises 0.711% of all the uranium on Earth, and is homogeneously mixed within the 238U in uranium ore. It turns out that these two different types of uranium are incredibly difficult to sort, as there is only about a 1% difference in atomic weight between them, thus mankind continues to search for better, cheaper, faster ways to separate them. Recently, a technology has emerged that makes the sorting of these atoms much faster, which, in the context of nuclear proliferation, can be a bad thing.

The refinement of technology throughout civilization has followed a consistent pattern; machines become easier to use, more efficient with respect to resource consumption, faster at completing the process they were designed to perform, and for all these reasons, cheaper to operate. This is exactly what has happened with the technology that people have developed to enrich uranium over the past eighty years. The Manhattan Project saw the advent of the “gaseous diffusion” enrichment process, which was the most technologically advanced and cheapest process for separating uranium at that time. Gaseous diffusion was eventually replaced with the “gas centrifuge” enrichment process, which was much faster and could perform the same amount of separative work while consuming far less electricity. Centrifuge enrichment remains the primary enrichment process throughout the world now, but today we are at another crossroads, with lasers looking to take the enrichment industry by storm; bearing promise of much quicker uranium enrichment while supposedly using even less electricity to do it once the process has been optimized. People are getting better and better at sorting atoms.

ENRICHMENT METHODS

The gaseous diffusion process was cutting edge technology in the 1940’s, and operated on a very simple premise. The idea was to somehow turn uranium into a gas and push it through filters that could block the passage of the comparatively larger 238U atoms, while letting the smaller 235U atoms through at a faster rate. Scientists, engineers, and chemists succeeded by combining uranium with fluorine in a uranium-hexafluoride (UF6) compound[1], and then forcing this gas through advanced membranes that solved the problem of sorting (U.S. Nuclear Regulatory Commission). The end result was low-enriched uranium that could be used for nuclear energy generation, but if that low-enriched uranium was cycled back through the system many more times, you could ultimately yield uranium that was enriched to the point that it was almost entirely 235U. This is called highly-enriched uranium (HEU), and it is what is used in nuclear weapons. The gaseous diffusion process provided a means for governments to enrich uranium, but this process is really quite slow and uses a tremendous amount of electricity. These drawbacks prompted the advent of the next epoch of enrichment technology.

The centrifuge enrichment process completely changed the enrichment industry. By injecting the aforementioned UF6 gas into a centrifuge that is rotating at a very fast speed, the lighter 235U will tend to collect at the axis of rotation and also at the top of the cylinder, allowing it to be discriminately captured, while the heavier 238U will collect on the perimeter and bottom of the cylinder (U.S. Nuclear Regulatory Commission). This explanation makes this process sound deceptively simple, but in reality, these centrifuges are rotating at such a great speed (typically 50,000-70,000rpm) that they push the physical limits of the aluminum, steel, or carbon fiber components that they are made of. Regardless, these material’s problems were ultimately overcome, allowing processors to enrich uranium much faster while using about fifty times less electricity than the gaseous diffusion process to produce the same amount of material at the same level of enrichment (Cameco Corporation).

The invention of and later public arrival of lasers in the 1960’s prompted Los Alamos researchers to theorize a decade later that a finely tuned laser could be used to separate isotopes of uranium, but it wasn’t until the 21st century that this technology was effectively commercialized (SILEX Systems). Two different methods using lasers for enrichment purposes were developed: Atomic Vapor Laser Isotope Separation (AVLIS), and Molecular Laser Isotope Separation (MLIS). AVLIS relies on imparting an electrical charge on the individual uranium atoms by exciting the atom so much that it loses an electron and is ionized. The laser is able to discriminate between 235U and 238U due to the different atomic weights giving each atom a different spectral absorption band, much like an atomic resonant frequency. By precisely tuning a solid-state laser with a Nd-YAG lasing medium, one can induce the 235U atoms to absorb the energy, and the 238U atoms to effectively ignore it. This is no small feat, however, as it requires a laser wavelength so precise that it needs to be accurate to a single angstrom.[2] A negatively charged plate awaits the uranium vapor after it has been lased, which then captures the positively charged 235U (U.S. Nuclear Regulatory Commission).

Despite the viability of AVLIS, MLIS seems to have emerged as the method of choice for commercialization of laser enrichment.[3] The idea of using lasers for sorting isotopes was conceived at Los Alamos National Laboratory in the 1970’s, but SILEX Systems, an Australian company, is widely regarded as the commercial pioneer in this field (Los Alamos National Laboratory). SILEX began work on the process in the 1990’s and eventually licensed the technology to General Electric and Hitachi who are currently in the process of constructing a test facility akin to a large scale proof-of-concept (SILEX Systems). Fundamentally, MLIS shares many similarities with the AVLIS process, though there are some important distinctions. With the MLIS process, the uranium is processed as the UF6 compound, just as it is in conventional enrichment methods. The aim is to induce a chemical change within the compound by breaking the molecule in a specific way, and MLIS can do this by utilizing two different lasers sequentially. The first excitation laser typically uses a carbon-dioxide lasing medium, which outputs light in the infrared spectrum and is optically tuned to exactly 16μm. This is the frequency at which it will selectively excite the 235U atoms, generating atomic vibration and producing a state of general volatility in the molecule. After the UF6 molecules pass through the infrared laser, they then pass through the beam of a second laser which serves to break only the UF6 molecules that contain 235U with a quick, high-energy pulse of light tuned to a wavelength in the absorption spectrum of 235U (U.S. Nuclear Regulatory Commission). A good analogy for this process is the classic TV trope in which a character sings so loudly and at such a high pitch that wine glasses and windows begin to break after some time. The laser is effectively exploiting the resonant frequency of the excited molecules, and when it does, an electron that the uranium is sharing with any of the fluorine atoms (recall that the compound is UF6, a single uranium atom bonded to six fluorine atoms) breaks away from the molecule; this is called disassociation (Jensen, Judd and Sullivan). What remains is UF5 and a free fluorine atom, and the immensely useful property of UF5 is that it exists as a solid under the same pressure and temperature that UF6 exists as a gas! The UF5 immediately precipitates out of the UF6 gas as a powder, allowing for conventional filtration methods to physically separate it from the feedstock. All the while, a scavenger gas such as methane captures the free fluorine atom to prevent re-fluoridation of the UF5 (U.S. Nuclear Regulatory Commission). This UF5 precipitate contains a disproportionately larger amount of the 235U isotope than natural uranium ore, thus we can say that it has been enriched.

Aside from the fact that this process is impressively innovative and an elegant solution when it comes to sorting uranium atoms, it is also much faster. To compare the three different enrichment processes, we will look at the typical separation factor[4] for each technology:

Technology Separation Factor # Stages for LEU (4%)[5] # Stages for HEU (90%) Req. Facility Size
Gaseous Diffusion 1.004 440-1760 1800-7000 Large
Gas Centrifuge 1.05 – 1.2 10-36 39-145 Moderate
Laser Separation  2 – 6[6] 1-2 4-10 Small

What the above table tells us is that for a single kilogram of uranium to be enriched to the point that it is usable fuel in a nuclear power plant (assumed to be 4% 235U in this example), it would have to either pass through 440-1760 separation stages of membranes/diaphragms in a gaseous diffusion facility,[7] 10-36 separation stages of centrifuges (range due to differences in efficiencies between different models), or pass through an AVLIS/MLIS system one to two times. Similarly, it would take only 4-10 passes through an AVLIS/MLIS device to generate weapons grade uranium (assumed to be 90% 235U in this example), compared to 39-145 stages of centrifuges or 1800-7000 stages of gaseous diffusion. Depending on the throughput of each system, i.e. the volume of feed material that a system can process over an interval of time, AVLIS/MLIS is likely an order of magnitude improvement in enrichment speed over centrifuge enrichment; a true game changer. Furthermore, AVLIS/MLIS prevents 234U contamination of the enriched product, whereas gaseous diffusion and centrifuge enrichment actually exacerbate 234U contamination due to its lighter atomic weight (U.S. Nuclear Regulatory Commission). 234U is not desired in the final product, because just like 238U it is not capable of undergoing fission. Given these vast advantages that AVLIS/MLIS has over traditional enrichment methods, it is easy to see why it is such an attractive option for any entity that wishes to enrich uranium.

LASER ENRICHMENT AND PROLIFERATION

Some may read this and ask, ‘does this ground-breaking technology change the dynamics of the ongoing international push against nuclear proliferation?’ This question is really just analogous to asking if there would be more nuclear weapons states if it were easier to covertly manufacture nuclear weapons. Personally I believe the answer is yes, though I admit the answer is speculative. The biggest obstacle of nation-states that have aspirations to manufacture nuclear weapons at this point is the risk they assume when they build an enrichment facility, as they are taking a chance that U.S. satellites will discover it and subsequent questions will be raised. What has changed is that these enrichment facilities no longer have to be large, as AVLIS/MLIS is a much more compact system.

AVLIS and MLIS both use a comparatively much smaller footprint than centrifuge and diffusion methods when speaking of the required infrastructure associated with the technologies. Centrifuges used in uranium enrichment are truly massive devices, with some advanced carbon fiber designs up to forty feet tall and and two feet in diameter, and a typical facility would house several thousand of them (Glaser). Gaseous diffusion plants are notoriously enormous and bulky, requiring large cooling systems and would typically, at any given time, be using hundreds or even thousands of megawatts of power as they try to force their uranium gas through the aforementioned membranes (Centrus Energy). Both of these types of facilities are much easier to identify from satellite imagery because of their size and unique features. Laser enrichment, however, allows for the capability to quickly produce an appreciable amount of weapons-grade fissile material in a small facility that is correspondingly difficult to detect. There is no requirement for any particularly large cooling systems, and though these systems do use a large amount of power compared to similarly sized civilian facilities, it’s not such a remarkably large amount of power that it requires substantial electrical infrastructure that is easily identified (U.S. Nuclear Regulatory Commission). This means that it will be much easier to hide enrichment infrastructure for countries that wish to trudge down the nuclear path. Though it is generally desired to reduce the size and increase the efficiency of practically any machine humans have ever invented, the “bulkiness” of conventional enrichment infrastructure happens to be useful because it’s distinctive and easier to detect.

It is already challenging enough to prevent the proliferation of nuclear weapons. It is fundamentally in every state’s interest to obtain one, because nuclear weapons function as a strong “final-word” to any sort of serious foreign-relations quarrel. Look to the decade long dispute between the United States and Iran regarding the Iranian nuclear program. This particular chronology serves to illustrate how difficult it is to reverse the course of an advanced nuclear program once it is already in place. Over ten years elapsed before a multilateral agreement with Iran was reached, and many people in both countries are still not satisfied with the result. The global community is also currently dealing with a seemingly aggressive, nuclear armed North Korea, with no particularly great solution in sight. In a hypothetical world where one could instantly obtain weapons grade fissile material by putting uranium ore into some kind of magical enriching machine, there is no doubt that every nation would have vast stockpiles of it. Obviously we do not live in that hypothetical world, but it does stand to reason that if enriching to weapons-grade concentrations of 235U is made easier in any way, more of it will be produced. Guns were, at one point in history, very difficult and time consuming to manufacture, and for that reason they were a rarity. That is, of course, not the case anymore. The introduction of AVLIS/MLIS prompts us to ask ourselves if, collectively, civilization is mature enough for the proliferation rapid enrichment capabilities.

Furthermore, enriched uranium is already quite cheap. This is especially apparent when one looks at how much of the generated electricity cost is due to the initial fuel costs for different power generation technologies. For instance, a study performed several years ago in Finland compared nuclear with gas, coal, and wind power, and quantified how many cents of a nuclear generated kilowatt-hour went to fuel costs, i.e. uranium ore and the cost to process and enrich it. For nuclear power, only 11.4% of the cost of a kilowatt-hour can be attributed to fuel costs, whereas this number is 59.7% for natural gas, and 25.5% for coal. This means that even if nuclear reactor operators were able to obtain their enriched uranium for free, the price of a kilowatt-hour produced by a nuclear reactor would only hypothetically fall from 2.37  to 2.10 ; as capital costs and operations and maintenance expenses comprise almost all of the costs associated with producing nuclear power (World Nuclear Association). Perhaps electricity producers would be able to scrape a small amount of profit from the increased savings on enrichment by using lasers, but it is doubtful that any of these savings will be passed onto consumers. In other words, if there is any energy generation technology that really needs to increase the efficiency of their fuel acquisition process, it’s certainly not nuclear. The emergence of cheap natural gas has, to some extent, necessitated innovation and cost reducing measures in the nuclear industry to ensure that it remains competitive, but the security concerns associated with rapid enrichment seem to outweigh the benefits.

INTERNATIONAL REGULATORY SOLUTIONS

At this point, there is no turning back the clock on AVLIS/MLIS. The genie is out of the bottle. The very fact that I was able to write this research paper with some degree of technical accuracy regarding the laser enrichment process is testament to that. The technical specifications of the SILEX process are technically classified by the U.S. government, but there is enough knowledge available on the Internet alone for any large team of physics, chemistry, and engineering PhDs with government level funding to set up a laser enriching facility and eventually get it working through some trial and error. In other words, though this is highly advanced technology, it is not as if it is out of reach for modernized countries like Saudi Arabia, Turkey, or Egypt to do themselves.

There is the possibility that the International Atomic Energy Agency (IAEA) could impose an international regulation on the usage of lasers for uranium enrichment purposes. It is plausible that a regulation could ban the operation of industrial scale, multi-kilowatt lasers being operated at certain wavelengths in the absorption spectra of the 235UF6 molecule or the 235U atom, but this presents a few issues. First, humanity has advanced its understanding of lasers to such an extent that, on a global scale, it is somewhat commonplace to find people who are familiar with laser tuning. Moreover, there are now several different readily employed methods one can use to achieve a highly specific wavelength in a relatively short amount of time.[8] Tuning a laser into or out of a specific wavelength is by no means an easy thing to do, but it is not prohibitively difficult for an individual who has studied photonics. This would largely prevent the IAEA from ever being able to catch someone using a laser for uranium enriching purposes “red-handed,” and this is not to mention the complexity of wavelength testing, especially in a closed system.

Secondly, the AVLIS/MLIS processes have applicability and usefulness outside of the nuclear power and weapons industries. These processes can be utilized for purposes of purifying radioisotopes that are used in the medical industry (Eerkens, Kunze and Bond). Regulation could make this peaceful application much more troublesome, as teams would presumably be forced to shutdown their operation and/or dismantle their systems for periodic inspections. Third, if the United States were to become the country that ultimately called for international regulation of industrial scale lasers that could be used for isotope separation, there is the diplomatic implication of hypocrisy. The U.S. is one of only a handful countries that have explored this technology, and is the only country currently constructing a commercial scale laser enrichment facility. Many countries already resent the U.S. for seemingly not making any meaningful reduction in its nuclear weapons stockpiles (Wan). Thus, the acquisition of and subsequent call for no other country to use an AVLIS/MLIS system will only serve to intensify this sentiment.

CONCLUSIONS

Technological innovation is a good thing that all of humanity can harvest benefits from. The average individual would be hard-pressed to identify practically any instance in which new technology made all of global society worse off. However, technology related to the advancement of weapons is an obvious exception, and it can easily be argued that the uranium enrichment industry falls into this category. It is unique in the sense that the technology enrichers employ could be gravely harmful if it were to fall into the wrong hands, and AVLIS/MLIS most certainly will at some point in the future. There is no doubt that the AVLIS/MLIS processes have peaceful and otherwise useful applications outside of the nuclear energy industry, but if we are to embrace this technological process, we must also come to terms with, and accept the accompanying risks of provoking further nuclear weapon manufacturing capabilities.

It is troubling to argue against such a state-of-the-art and an elegant solution to the problem of sorting uranium atoms. Laser isotope separation is a triumph of human innovation, and a triumph of modern science. However, it becomes morally paralyzing when trying to reconcile the advancement of chemistry and physics as academic disciplines with the potentially harmful real world applications of the innovations themselves. For this reason, I believe that one can rationally appreciate the scientific achievement of inventing and demonstrating this process without simultaneously advocating for its use. The fact that nuclear weapons were invented is a testament to humanity’s scientific progress, ingenuity, and intellect, but that doesn’t mean that nuclear weapons were or are a good thing.

Though rapid uranium enrichment presents a potential threat to nuclear proliferation, one can take solace in the fact that it is arguably one of the most technologically advanced processes on Earth, and that the intellectual capital and resources required to make it work can only be found at the governmental level in relatively advanced nations.  This means that we do not have to worry about a dubious group of terrorists producing weapons grade uranium using lasers anytime soon. Furthermore, it is useful to remind oneself that even if an independent collective produces weapons grade uranium using a covert laser enrichment facility, one still has to build a bomb around the core. That is essentially just as difficult as building the laser to enrich the fuel. Beyond that is the requirement that this group also still has to build a delivery vehicle, such as a cruise missile that has satellite guidance, which is just as, if not more, difficult as building an AVLIS/MLIS system and a nuclear bomb. The point of saying this is to underscore the point that the laser enrichment process does not suddenly give every government the ability to produce and deliver a nuclear weapon. My aim is not to fear monger. My point is that it changes the calculus of that ability. It makes a relatively meticulous, bulky, expensive, identifiable process more efficient, more compact, less costly, and more clandestine. This is the reason that I believe we should focus on preventing the proliferation of this technology.

-Tyler

 FOOTNOTES

[1] Uranium-hexafluoride is particularly useful because it sublimes from a solid to a gas at a remarkably low temperature of 133°F.

[2] An angstrom is equal to one ten-billionth of a meter.

[3] This is largely because it is far easier to work with UF6 as a gas than it is to vaporize uranium metal.

[4] Defined as the quotient of the ratio of isotopes (235U/238U) after a stage of separation and the ratio of isotopes prior to separation.

[5] Number of separation stages required for 4% enrichment was calculated by using the separation factor of each respective technology sourced from the three cited U.S. Nuclear Regulatory Commission publications. Starting from natural uranium and separating to 4% could be achieved in a single stage if the technology had a separation factor of at least 5.82. From there, one can simply evaluate logx(5.82) where x is equal to the separation factor of the technology. The output of this log is the approximate number of stages that particular technology would require to reach a 4% concentration of 235U. The following HEU column is calculated in the same way, logx(1256.83).

[6] The separation factor of MLIS and AVLIS has been reported as anywhere from two to six. The technology is still largely in the developmental phase, and it is likely that a commercialized version of the technology will be able to achieve efficiencies towards or exceeding the upper end of this range.

[7] LEU at 440 stages in a gaseous diffusion plant is the theoretical minimum at a 1.004 separation factor, but many plants, like the plants in Portsmouth or Paducah, required up to four times this amount when they were still in operation.

[8] Perhaps the most common is the introduction of a specific dye into the lasing medium, hence the term “dye laser,” though there are other methods, such as simply shifting the output wavelength optically.

 

REFERENCES

Cameco Corporation. Cameco U101 Fuel Processing: Enrichment. 2016. 20 April 2016. <https://www.cameco.com/uranium_101/fuel-processing/enrichment/&gt;.

Centrus Energy. Paducah Gaseous Diffusion Plant. 2013. 20 April 2016. <http://www.centrusenergy.com/gaseous-diffusion/paducah-gdp&gt;.

Eerkens, Jeff, Jay Kunze and Leonard Bond. “Laser Isotope Enrichment for Medical and Industrial Applications.” 14th International Conference on Nuclear Engineering. Miami: Idaho National Laboratory, 2006. 1-13.

Glaser, Alexander. “Characteristics of the Gas Centrifuge for Uranium Enrichment and Their Relevance for Nuclear Weapons Proliferation.” Science and Global Security 2008: 1-25.

Jensen, Reed, O’Dean Judd and Allan Sullivan. “Separating Isotopes with Lasers.” Los Alamos Science December 1982: 2-33.

Los Alamos National Laboratory. Los Alamos Science No.4 – Winter/Spring 1982. December 1982. 1 May 2016. <http://la-science.lanl.gov/lascience04.shtml&gt;.

SILEX Systems. SILEX History. 2016. 28 April 2016. <http://www.silex.com.au/History&gt;.

U.S. Nuclear Regulatory Commission. “Uranium Enrichment Processes: Gas Centrifuge.” 21 October 2014. USNRC Technical Training Center. 6 May 2016. <http://pbadupws.nrc.gov/docs/ML1204/ML12045A055.pdf&gt;.

—. “Uranium Enrichment Processes: Gaseous Diffusion.” 21 October 2014. USNRC Technical Training Center. 4 May 2016. <http://pbadupws.nrc.gov/docs/ML1204/ML12045A050.pdf&gt;.

—. Uranium Enrichment Processes: Laser Enrichment Methods (AVLIS and MLIS). 21 October 2014. USNRC Technical Training Center. 1 May 2016. <http://pbadupws.nrc.gov/docs/ML1204/ML12045A051.pdf&gt;.

Wan, Wilfred. “Why the 2015 NPT Review Conference Fell Apart.” 28 May 2015. United Nations University Centre for Policy Research. 2 May 2016. <http://cpr.unu.edu/why-the-2015-npt-review-conference-fell-apart.html&gt;.

World Nuclear Association. The Economics of Nuclear Power. March 2016. 3 May 2016. <http://www.world-nuclear.org/information-library/economic-aspects/economics-of-nuclear-power.aspx&gt;.

YELLOWCAKE AND THE GREENHOUSE BLUES

/ Tyler Pedigo / Leave a comment

            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.

NUCLEAR ROADBLOCKS

            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.

URANIUM SUPPLY

            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.

PROLIFERATION

            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.

CONCLUSION

            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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