Just Released! “Energy, Biology, Climate Change”

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Our newest book, published on May 6, 2015 and available at Amazon.com for $19.95.

The focus of this book is the interactions between energy, ecology, and climate change, as well as a few of the responses of humanity to these interactions. It is not a textbook, but a series of chapters discussing subtopics in which the authors were interested and wished to write about. The basic material is cutting-edge science; technical journal articles published within the last year, selected for their relevance and interest. Each author selected eight or so technical papers representing his or her view of the most interesting current research in the field, and wrote summaries of them in a journalistic style that is free of scientific jargon and understandable by lay readers. This is the sort of science writing that you might encounter in the New York Times, but concentrated in a way intended to give as broad an overview of the chapter topics as possible. None of this research will appear in textbooks for a few years, so there are not many ways that readers without access to a university library can get access to this information.

This book is intended be browsed—choose a chapter topic you like and read the individual sections in any order; each is intended to be largely stand-alone. Reading all of them will give you considerable insight into what climate scientists concerned with energy, ecology, and human effects are up to, and the challenges they face in understanding one of the most disruptive—if not very rapid—event in human history; anthropogenic climate change. The Table of Contents follows: Continue reading

Nuclear Power Generation: High Demands for Cooling Water Use

by Cameron Bernhardt

Nuclear power is often praised for its potential to replace carbon-intensive energy sources and reduce greenhouse gas emissions from electricity and power generation. Although nuclear power may offer a promising future in this regard, it is likely to place stresses on the environment in other ways, namely through increased demands on water for cooling and space for waste disposal. Byers et al. (2014) tested six decarbonization pathways to estimate current water use in the UK electricity sector and project water use to 2050 in the UK. The study observed the water use associated with cooling for all varieties of thermoelectric power plants, but nuclear power accounts for over 20 percent of the UK’s electricity mix and is likely to share a large stake in the future of the UK’s power mix. Byers et al. concluded that the pathways with the highest projected proportion of nuclear generation resulted in tidal and coastal water abstraction that exceeded current levels by up to six times. This finding suggests that nuclear power may not be as viable a future energy source as previously thought, especially in areas where water resources are relatively scarce. It seems that the UK should extend its investigations into the merits of nuclear power, and similar studies may be warranted to assess the impacts of nuclear generation in other countries. Continue reading

What Has Worked to Slow Global Warming

by Emil Morhardt

Last week, in anticipation of the United Nations climate conference in New York, The Economist concluded that the single most important action to slow global warming so far has been enactment of the Montreal protocol. Say what? This isn’t on most environmentalists’ radar as an important factor. The Montreal protocol is the 1987 international agreement to save the ozone layer by phasing out Freon and other chlorofluorocarbons used in refrigeration. But these substances are powerful greenhouse gases as well as destroyers of stratospheric ozone, and the protocol caused millions of tonnes of them not to be released into the atmosphere. The article concludes that this avoided release of the greenhouse gas equivalent of 5.6 billion tonnes (bt) of CO2. This is about twice as much avoided CO2 as the next two most effective actions, global use of nuclear power (2.8 bt) and hydroelectricity (2.2 bt), and four times that of the fourth most effective action, China’s one-child policy (1.3 bt). I’m guessing that most of the 300,000 demonstrators in New York last week are not proposing an expansion of these latter three items, but their past effectiveness does make one think. The most effective actions taken specifically to reduce energy usage and CO2 emissions have been worldwide adoption of renewables (0.6 bt), US vehicle emissions standards (0.5 bt), and Brazil forest preservation (0.4 bt). The remaining 11 items on The Economist’s list are small potatoes, totaling less than 1 bt collectively. Continue reading

Japan’s Nuclear Crisis

The 8.9 earthquake, and subsequent tsunami, that rocked Japan on March 11, 2011 have lead to severe damage at Tokyo Electric Power Co.’s Fukushima Daiichi<!–[if supportFields]> XE “Fukushima Daiichi” <![endif]–><!–[if supportFields]><![endif]–> nuclear power plant. The problems at Fukushima Daiichi arose due to the failure of the cooling system and the significant loss of water from the cooling pools.  As authorities continue to work to reestablish the cooling system, Japanese citizens wait anxiously.  Twenty-five years after the meltdown of Chernobyl-4, it seemed that the world was beginning to accept the importance of nuclear power for providing a clean and reliable source of energy in the future.  However, the situation in Japan has awakened our fear of all things nuclear.  Critics argue that the same thing that is happening at Fukushima Daiichi could happen in the U.S. and that the country would be wise to halt all nuclear energy production.  Other, conversely, argue that the Fukushima accident could create a chance for the nuclear industry to “reboot” and look for innovative technologies that may decrease the risk associated with traditional solid-fuel uranium reactors.—Carolyn Campbell

 
          The core of a traditional nuclear reactor, such as the Fukushima Daiichi<!–[if supportFields]> XE “Fukushima Daiichi” <![endif]–><!–[if supportFields]><![endif]–> reactor, contains both water and fuel rods made of zirconium and pellets of nuclear fuel, usually uranium, which set off a controlled nuclear reaction.  This reaction heats the water, creating high temperature steam, which powers a turbine<!–[if supportFields]> XE “turbine” <![endif]–><!–[if supportFields]><![endif]–> and generates electricity.  A meltdown occurs when the core gets too hot, causing the fuel rods to crack and release radioactive gases.  In the worse case scenario, the fuel pellets melt and fall onto the reactor floor, where they can eat through the protective barriers and eventually reach the surrounding environment.  In Japan, the reactors are designed to turn off automatically in case of a disaster, with the aim of preventing a meltdown.  However, even with the plant shut off, nuclear fuel rods continue to generate a huge amount of heat.  In order to cool the fuel, backup generators are meant to pump water into the plant.  These generators failed at Fukushima Daiichi, leading the fuel rods to boil off remaining water and become partially exposed.  If left exposed for long enough, the fuel rods could melt and leak radiation.  In order to avoid this, authorities are pumping seawater into the reactor to cool the fuel rods.  However, salt buildup on the fuel rods can allow them to heat up more by blocking water circulation between the fuel rods, and, in the worst case, can eventually lead to a meltdown.  Additionally, workers have released built-up gases containing some radioactive material into the atmosphere in order to ease pressure inside the plant. 
          The problems at Fukushima Daiichi<!–[if supportFields]> XE “Fukushima Daiichi” <![endif]–><!–[if supportFields]><![endif]–> have aroused concerns of similar disaster occurring in the United States.  While some critics argue that the US should halt all nuclear power generation others suggest that the accident in Japan lends a chance to recreate the nuclear industry.  It has been suggested in recent years that the solid-fuel nuclear reactors, like the ones in Japan, are an outdated technology and should be replaced by a safer and cheaper kind of nuclear energy. According to Matt Ridley of the Wall Street Journal, thorium has many advantages as a nuclear fuel.  There is four times as much thorium in the world as there is uranium; it is easier to handle and to process; it “breeds” its own fuel by continuously creating uranium 233; it can produce 90 times as much energy from the same quantity of fuel; no plutonium is produced by its reactions; and it generates much less waste, with a much shorter half life.  Neutrons are needed for a thorium reactor to run and can be supplied with a particle accelerator or uranium 235.  Both options are highly controlled and are relatively safe.  Additionally, the fuel in a thorium reactor cannot melt down because it is already molten, and reactions slow as it cools.  Whether it leads to new innovations or a general shift away from nuclear power, the disaster at the Fukushima Daiichi plant will undoubtedly alter the future of nuclear energy generation.  

Laser Transmutation of Nuclear Waste

The issue of radioactive waste is a major challenge in the widespread acceptance of a nuclear energy industry. The issues of where to store the nuclear waste and the possibility of radioactive materials leaching into the under-ground water supply seriously undermine the potential of nuclear energy.  However, with the ongoing development of ultra-intense laser techniques, researchers are exploring the possibility of laser transmutation of radioactive materials into stable isotopes.  Sadighi-Bonabi et al. (2009) analyzed the opportunity for transmutation of 93Zr, a highly radioactive nuclear waste with a half-life of 1.53 million years.  The authors suggest that through ultra-intense laser transmutation, 93Zr can be converted to 92Zr, its stable isotope.  High-energy electron generation, Bremsstrahlung, and photonuclear reactions were observed and the number of reactions that produced 92Zr calculated.  It was found that the laser intensity, irradiation time, and repetition rate of laser have strong and direct effects on the yield of 92Zr and the number of reactions. —Carolyn Campbell
Sadighi-Bonabi, R., Irani, E., Safaie, B., Imani, Kh., Silatani, M., Zare, S., 2010. Possibility of ultra-intense laser transmutation of 93Zr (γ, n) 92Zr a long-lived nuclear waste into a stable isotope. Energy Conservation and Management 51, 636–639.

 
          The disposal of long-lived radioactive waste is a significant challenge for the nuclear industry.  Through the development of ultra-intense laser technologies, the possibility of photonuclear transmutation of nuclear waste to more stable isotopes has offered new solutions to solving this problem.  When an ultra-intense laser pulse interacts with the radioactive waste, gamma radiations induce nuclear reactions for transmutation of the waste into a stable isotope.  Sadighi-Bonabi et al. focused their study on Zirconium, particularly 93Zr, a fission product in nuclear reactors with a half-life of 1.53 million years.
          In order to assess the number of reactions and laser-induced photonuclear activation of 93Zr, the authors analyzed available experimental data from focusing intensities onto a solid target.  For this study, the laser intensity was assumed to be 1020W/cm2 with a repetition rate of 10 Hz.  Calculations were also extended to higher intensities of 5 x 1020 W/cm2, 1021 W/cm2, 5 x 1021 W/cm2, and 1022 W/cm2.  The number of reactions was calculated by evaluating the energy spectrum of the laser and a cross section of the photonuclear reaction between threshold and cut-off energy.  It was found that the Bremsstrahlug spectrum, relating to the deceleration of electrons, depended on the intensity of the laser, with higher intensities increasing the number of reactions.  Additionally, irradiation time and repetition rate were found to have substantial effects on the yield of 93Zr (γ, n) 92Zr and the number of reactions.  If the target is irradiated for an hour by a laser light of 1020 W/cm2 at a repetition rate of 10 Hz, approximately 2.7 x 107 reactions will occur.  By increasing the repetition rate, yield would also increase.  However, achieving higher rates also means using more power, and more advanced lasers.  Additionally, although increased intensity of the laser would lead to a higher number of reactions and activity, there is an optimum intensity at which a maximum number of reactions is reached and, beyond that point, the overlap between reaction cross-section and the number of photons disappears.  For 93Zr (γ, n) 92Zr, this optimum intensity was calculated at 3 x 1021 W/cm2
          Through this study, it was found that laser intensity, irradiation time, and repetition rate of the laser have a significant, direct effect on the yield of 92Zr and the number of reactions.  Maximizing the efficiency of laser technology for the transmutation of radioactive isotopes will prove valuable in future efforts to solve the problem of long-lived nuclear waste. 

Nuclear Waste Disposal

While there is a growing consensus that increased investment in nuclear energy is necessary to satisfy future energy needs, the United States currently lacks a suitable permanent storage site for radioactive waste.  With more than 103 open-cycle nuclear reactors throughout the country, the issue of nuclear waste storage is a growing concern.  Schaffer (2010) assesses the current state of nuclear waste in the U.S. and proposes solutions to developing a viable nuclear waste disposal program.  First, the U.S. should reopen the licensing process for the Yucca Mountain waste disposal facility.  Additionally, to decrease the amount of waste sent to disposal facilities the U.S. should restart PUREX reprocessing plants.  Upon taking these initial steps, the government must continue to search for additionally permanent storage sites and appropriate funds to educate local communities about nuclear waste storage.  The Department of Energy (DOE) and the Nuclear Regulatory Commission (NRC) should also issue guidelines and promotions to encourage the industry to build new TRISO-fueled reactors.  Finally, further research should focus on innovative technologies that burn nuclear fuel waste. —Carolyn Campbell
Schaffer, M.B., 2011. Toward a viable nuclear waste disposal program. Energy Policy 39, 1382–1388.
Of the 103 operating commercial nuclear power plants in the U.S., all of them are of the open-cycle, batch type.  These plants produce long-lived radioactive waste in the form of ceramic-encased low-enriched uranium oxide pellets packed into zirconium-clad rods.  With the 1982 Nuclear Policy Act, the U.S. recognized the need for a consolidated storage site, and in 1987 named Yucca Mountain, Nevada as the site for deep underground repositories.  However, in response to pressures from Nevada politicians, the DOE has filed a motion to withdraw the license application for Yucca Mountain operations.  Due to this decision, the country’s nuclear waste remains stored in on-site tanks and casks, which Schaffer argues is risky, inefficient, and unsustainable.    Additionally, as more open-cycle nuclear plants come on line, the problem only gets worse.
Schaffer suggests that there are two main components to solving the open-cycle nuclear waste disposal program.  First is the issue of community confidence; in order for a permanent storage site to be developed, community endorsement is required.  Therefore, a confidence-enhancing plan should identifying three or four sites instead of just one, specify storage for a nominal period, provide adequate monetary incentives, and disclose the risks and rewards of a nuclear storage site.  The second component of a long-term solution for nuclear waste involves reducing the amount of high-level nuclear waste sent to a storage facility.  One way to achieve this is through the PUREX (Plutonium and Uranium by Extraction) process in which depleted fuel rods are cut into pieces and dissolved in nitric acid.  Uranium, plutonium, and actinides can then be extracted from the resulting liquid.  The extracted uranium-235 can be burned in heavy-water moderated reactors or fast-neutron reactors for additional energy, the plutonium-239 can be used to make MOX (mixed oxide uranium and plutonium) fuel, and the actinides can be vitrified in a design that is resistant to water leaching. 

Additional technological solutions for decreasing waste are described in the paper.  Closed-cycle fast reactor technology, such as an Advanced Liquid Metal Reactor (ALMR), has been studied for many years.  ALMR uses energetic neutrons to interact with uranium-238 to eventually produce plutonium-239.  Through pyrometallurgical processing, a mix of transnuranic elements from the used fuel can be extracted and the uranium can be reused.  This process has advantages over PUREX reprocessing, in a counter-proliferation sense, because it does not produce pure plutonium.  An alternative to reprocessing or refining is to produce nuclear waste that is self-contained, depleted to the point where it is not a proliferation problem, and can be stored in underground sites without concerns of water leaching or seismic damage.  TRISO (tri-structureal isometric) fuel reactors use fuel pebbles that, after spent, are safe to store without cooling, are resistant to water leaching, and contain highly depleted nuclear materials.  By employing such overlooked strategies for waste reduction and reopening the search for a permanent storage site the U.S. will be able to develop a more viable nuclear waste disposal program.

Hydrogen Production using Nuclear Energy

It is often argued that hydrogen is the transportation fuel of the future due to its high efficiency and versatility of use.  One way to obtain hydrogen is nuclear-based production using thermochemical water splitting.  Lubis et al. (2010) conducted a life cycle assessment (LCA) of this process in order to determine its environmental impacts.  The authors studied the impacts of both nuclear and copper-chlorine thermochemical plants using LCA methodology framework from the International Organization for Standardization (ISO) and CML-2001 impact categories.  The four main stages of the LCA include: i) goal definition and scope; ii) inventory analysis; iii) impact assessment; and iv) improvement assessment.  From this study it was found that the most significant environmental impacts come from the construction of the two plants and the operation of the nuclear plant.  In contrast, the operations of the thermochemical plant do not significantly contribute to the overall environmental impact.  In order to decrease the environmental impact of nuclear-based hydrogen production, the authors suggest developing more sustainable processes, particularly in the nuclear plant and construction. —Carolyn Campbell
Lubis, L.L., Dincer, I., Rosen, M.A., 2010. Life cycle assessment of hydrogen production using nuclear energy: an application based on thermochemical water splitting. Journal of Energy Resources Technology 132, 1–6.
          The authors undertook a LCA of hydrogen production using nuclear energy.  In order to minimize emissions, hydrogen is produced via a thermochemical cycle that involves a sequence of chemical reactions yielding a net reaction of splitting water.  This study analyzed the copper-chlorine (Cu-Cl) thermochemical cycle in which nuclear energy from a supercritical water-cooled reactor (SCWR) provides the thermal energy for driving the chemical reactions.  Therefore the emissions from the overall system are the sum of the advanced nuclear power plant and the thermochemical hydrogen production plant.  The nuclear plant is taken to be rated at 2060 MWth and the entire thermal output of the plant goes to producing hydrogen.  The thermochemical plant is assumed to have a hydrogen production capacity of 5200 kg/h of H2and a 30-year operational life.  All calculations are based on 1 h of operation of the entire plant.
          Lubis et al. utilized reported literature in order to estimate the emissions of the nuclear and thermochemical plants.  It was estimated that 4.29 kg/h of uranium is needed to produce a thermal output of 2060 MWth. For the thermochemical plant the environmental impact was estimated based on the use of chemicals in the process and use of raw materials.  In order to produce 5200 kg of H2,514,800 kg of CuCl and 189,600 kg of HCl are required.  To assess the impact of hydrogen production, the environmental impacts of emitted substances were classified into environmental impact categories.  These categories include abiotic resource depletion potential (ADP), global warming potential (GWP), ozone depletion potential (ODP), eutrophication potential (EP), acidification potential (AP), photochemical ozone creation potential (POCP), and radioactive radiation (RAD).  The quantitative environmental impacts were then calculated by multiplying the quantity of emitted substances by the relevant classification factor and the GaBi database was utilized to determine the environmental impact of emissions based on inventory analysis. 
          The LCA produced several findings regarding the environmental impact of nuclear-based hydrogen production using thermochemical water splitting.  For GWP, the system emits 0.0025 g CO2-eq over the life of the plant, with 95% of these emissions attributable to the construction of the nuclear plant and the hydrogen plant.  Additionally, regarding the AP, the emissions of the system are 0.00015 g SO2-eq, with the 99% of emissions coming from construction and the nuclear fuel cycle.  Construction contributes significantly to other impact categories including EP, ODP, and POCP, while the nuclear fuel cycle contributes significantly to ADP and RAD.  In order to decrease the environmental effects of this system the authors suggest developing more sustainable processes in the nuclear plant and the construction of hydrogen production.