green atomsEmbracing nuclear power may be the only way to save the planet from carbon-induced warming.by Romney B. Duffey
Even after the record-setting run-up in oil prices last year, many people refuse to face the facts. But the truth is clearly visible to those who are willing to look at the situation: Our society's dependence on petroleum is unsustainable. We are subject to falling global oil reserves and a dwindling number of exporters. Indonesia, a charter member of the Organization of Petroleum Exporting Countries, is now a net importer of oil--but that isn't the entire reason why oil is a bad long-term bet. After all. there are still trillions of barrels of oil in the ground, and nations can suffer "regime change" if they hold out for too high a price. But recent increases, fluctuations, and speculation in oil prices show how unstable the energy system is. And add that complication to the solidifying consensus that carbon dioxide emitted from fossil fuel burning is a major contributor to unwelcome worldwide climate changes, and the need for some major alternative to petroleum is hard to refute.
Just what that alternative should be, however, is not so clear-cut.
The main contenders for the title of emission-free, safe energy are wind power and nuclear power, and the division between the two camps is stark. Nuclear advocates often pooh-pooh wind as too intermittent to rely on and too diffuse to harvest profitably. Wind enthusiasts generally deride nuclear energy as a technological nightmare that can only compete if many costs--for insurance, cleanup, and waste disposal, for example--are borne by taxpayers.
Thankfully, the concerns of both sides are overblown. Indeed, one of the best ways to move from the petroleum-based economy to one that relies on hydrogen to power vehicles is to combine wind turbines and nuclear reactors in an integrated system. Together, those energy sources could usher in Nuclear plants and windmills alike emit virtually no greenhouse gases over the full cycle. After all. uranium is not carbon, and the major emissions are actually due to mining, milling, and manufacturing of construction materials, not fuel use perse. It is already recognized that even the modest greenhouse gas reduction targets set by the Kyoto Accord (equivalent to base emissions in 1990) cannot be met in Europe, Canada, and elsewhere without the continued operation of the existing nuclear plants.
The overall energy demand, on the other hand, is not decreasing, and global demand is expected to rise rapidly in the coming decades. Even if energy efficiency measures, such as a widespread switchover to hybrid-electric vehicles, are taken in the developed world, there will be a tremendous uptick elsewhere. China and India, to name two countries making aggressive economic progress, are climbing the well-known wealth ladder that relates GDP to electrical power use, and are increasing their use of carbon fuels as a consequence.
Future energy use can be projected from assumptions related to future economic growth (circa 2 percent per annum global average), population, energy supply, and forward energy price estimates. There is plenty of blurring at the margins of such calculations, but the trends clearly point to energy needs double to seven times those of today by the middle to end of the 21st century. Along with the economic and energy growth, there are large rises expected in emissions, notably greenhouse gases, which also raise the potential for future climate change.
How much new capacity is "double to seven times" what the world has today? Current usage patterns appear broadly similar to the American ones, other than that American generation of electricity relies slightly more on carbon-based fuels. The United States uses 25 percent of the world's energy consumption today. Hence one can get a reasonable first approximation for the world by multiplying American figures by a factor of four. That means to supply just the increase in the world energy demand by 2050, we'll need to build the equivalent of the American infrastructure at least four times over--and perhaps 24 times over.
To meet this demand without causing a breakneck rise in greenhouse gas levels in the atmosphere will mean adding thousands of gigawatts worth of non-carbon-based generating capacity. To stabilize the climate, according to models published by the International Panel on Climate Change, non-carbon-based energy would be required to power 80 percent of the world's automobile usage by 2040 and 80 percent of the growth in global electric generating capacity by 2020.
It's a staggeringly large amount of power that must be produced with little or no net emissions. Even more daunting is that much of the projected new demand is expected to come from developing nations--countries most likely to adopt the cheapest, dirtiest technology available.
Setting their reputations aside, both nuclear reactors and wind turbines have a great deal in common.
The global search for a safe, secure, sustainable energy future has placed renewed emphasis on the key role of nuclear energy. Nuclear plants have a generally excellent operating record and low costs, and the world's existing nuclear plants must meet stringent national and international safety standards.
But this sterling record did not come effortlessly. There have been some painful lessons learned. The Chernobyl and Three Mile Island accidents have already led not only to enhanced public awareness and interaction, but to improved nuclear plant safety standards, plant upgrades, and the monitoring and tracking of performance indicators that emphasize increased safety and less risk. As operational experience has been gained, the management emphasis placed on excellence, safety, and efficiency has reaped rewards. This is reflected in the steady rise in plant performance and the extent of dependency on nuclear generation in many countries. The large developing countries, most notably
India and China, are significantly expanding their nuclear generating capacity.
The lessons learned from operating more than 400 current nuclear plants are incorporated into the new building under way in many countries. Plans for over 40 additional units are proceeding, in addition to life extension for many operating units worldwide. New builds are occurring in Asia and Europe, with plans for more units in the United States once a new licensing process is proven out. The growth in nuclear power comes after a wave of politically motivated phase-out plans placed some energy-poor European countries at the mercy of imported natural gas from Russia and North Africa.
Despite statements by opponents that nuclear energy is expensive, in many countries with a large nuclear power industry--including Canada, France, Japan, and the United States--reactors have lower costs of electricity generation than gas- or coal-fired plants. Emerging new builds in Finland, China, and elsewhere are justified on economic grounds alone. Reactors being built today have overnight capital costs close to $1,500 to $2,000 per kilowatt of electricity, and generating costs competitive with natural gas.
Nuclear power is winning social acceptance by demonstrating a record of safe, stable, and sustained excellence in plant operation. Reactors are good neighbors. As with any technology, nuclear reactors must emphasize safe operation and inherent safety in the design. Special safety systems are incorporated into reactors to mitigate the consequences of a serious process failure requiring reactor shutdown, decay heat removal, or retention of released radioactivity.
Systems provide diverse and redundant safety, which together with the passive heat removal provide both very low core damage frequencies and consequences. The designs benefit from utilizing existing and extensive probabilistic safety assessments, for both internal and external events. The survival and performance of nuclear plants through numerous earthquakes in Japan and damaging hurricanes in the United States have already demonstrated the resilience and strength of the designs.
Nuclear plants also have been cited and listed as terrorist targets: Since 9/11, measures to strengthen plant security and restrict access have increased. Nevertheless, nuclear plants represent partially hardened and defended targets, and the evidence suggests that although threats remain, more likely targets are those that are softer and less protected. The fear outweighs the reality.
Waste disposal is an often-raised objection, but the means to store the radioactive materials safely on-site has now been technically proven. Progress toward geologic disposal or storage is also moving forward, albeit slowly as safety standards are continually revisited and opponents of the nuclear fuel cycle do not wish to see closure. Thus, the far-future limits and time scales are extended in attempts to block the licensing of underground storage.
A similar debate is just beginning for closing the "carbon cycle," with discussion over the costs and feasibility of carbon sequestration and emissions reduction. Introduction of carbon credits, emissions trading, and avoided-emissions benefits can and should be extended to nuclear energy as a rational and effective strategy.
One of the main sources of future energy demand will be transportation, which already accounts for 20 to 30 percent of the energy use--almost all of it petroleum. Recognizing the present and future problems of increased oil demand, regional locations of major suppliers, reduced supply, greenhouse
gas issues, and rising fuel prices, almost all major automobile manufacturers are pursuing research on alternate fuels.
Some critics who once saw nuclear power as a technological nightmare have come to realize that it is a potenbtially green technology.
Hydrogen is the leading candidate for replacing gasoline. The automakers and major academic and industrial partners are examining variants of hydrogen combustion, hybrid propulsion, and electric power using fuel cells. Most important, they are studying technologies for generating hydrogen in large-scale quantities. Meanwhile, high natural gas prices are pushing the petrochemical and plastics industries to seek alternate sources of hydrogen, which is now made most often by reforming methane.
Even with a major commitment to a hydrogen economy, the production needed at the outset is small. This favors distributed production by electrolysis, which avoids the scale-dependent costs of distribution from centralized plants. For electrolysis to be the preferred option capital equipment must be reasonably cheap--but the dominant cost component will always be the electricity price.
Advanced nuclear reactor designs, such as Atomic Energy of Canada's Advanced Candu Reactor and BNFL's Advanced Passive series, ought to be capable of producing electricity for about 3 cents per kilowatt-hour by 2012. It's expected that the most successful operational model will be mixed use: sending electricity to the grid during peak hours (when the price is highest) and making hydrogen the rest of the time. The exact mix of hydrogen to electricity production would be market-and cost-dependent, and would vary dynamically, depending on the electricity price and the capital cost of hydrogen production and storage. I have helped create a model of this balance, and it shows that the production costs for hydrogen, using the actual prices of electricity in Alberta and Ontario, can come in under the $2,000 per ton target set by the U.S. Department of Energy.
Wind and solar can produce electricity for electrolysis as well. In fact, they may be better suited for that than for producing electricity for the grid because of their intermittent and unpredictable availability. If wind power availability can reach a capacity factor of about 35 percent, a supplementary current of wind-generated electricity may be fed economically to an electrolytic plant primarily supplied by nuclear power.
Could co-production of electricity and hydrogen improve the economics of harnessing wind energy? To study this question, a new model was constructed using price data from the Ontario electrical grid, with costs of electricity from both nuclear and wind sources set at 3 cents per kWh. Building on the previous model, which considered nuclear power only, the current limit for the hypothetical electrolysis system for hydrogen production was increased by about a third, and the installed cost of the system was increased by 10 percent (to $330 per MW).
We sought to find the right ratio of wind to nuclear capacity. Although the cost of producing hydrogen with this hybrid system is higher than in a nuclear-only setup, it can still meet the $2,000-per-ton target as long as no more than 30 percent of the power produced goes to making hydrogen. Indeed, with a very low proportion of hydrogen production, the hybrid's cost appears even lower than with nuclear alone.
Like the nuclear-only scenarios, the hybrid appears to make less profit than selling electricity alone, but that assumes off-peak electricity prices would not be affected by extensive capital investment in electricity generation. The added generating capacity might well bring down peak wholesale electricity prices, and the hydrogen co-product could well offer a more certain price. Another minor advantage for the hybrid approach could arise from directing wind output more strongly to electrolysis during reactor outages.
It has been argued that, in using nuclear reactors to replace fossil fuel use, society would be replacing one unsustainable energy system with another. It has been projected that a nuclear-heavy option for future non-carbon energy growth would require an eventual 123 exajoules (about 116 quadrillion Btu) per year of nuclear power. The number of new reactors needed to meet that demand is more than 4,000--more than 10 times the number of reactors currently operating or under construction. Setting aside fears of accidents, waste, and misuse of spent fuel, there are serious questions as to whether there is enough uranium to make such schemes feasible.
Conventional reserves of uranium worldwide are estimated at six million tons: advanced reactor designs require 1,160 tons of uranium to produce I EJ. That means that 123 EJ per year require around 440.000 tons of uranium per year, and the world's uranium reserves would suffice for barely 14 years.
That's not the end of the story, however. Recycling of used uranium fuel can easily double the energy availability. Reactors can quite easily use thorium, which is four times more abundant than uranium. Unconventional uranium sources can be exploited. And, lastly, we can revisit breeder reactor technology.
All of these options and extended fuel utilization schemes are being explored, and there are sufficient presently known thorium reserves to extend the use for at least 300 years. These resources are largely in geopolitically stable regions with a known history of resource extraction, and will also enable the key developing countries, such as India and China, to use alternate thorium-based fuel cycles. Uranium and thorium resources do not appear to constrain the scenarios, although the current, wasteful approach to uranium utilization, which converts much less than one percent of the available energy to heat, will have to be improved.
With fuel recycling--allowed today in France and Japan--a clear safeguards process, and the use of thorium ores, there are sufficient resources to last for as long as 2,300 years, and with thorium reuse, indefinitely.
Establishing new reactors in regions with plentiful wind resources (marked in dark blue and black) could facilitate nuclear-wind cooperation.
In addition to the sun, then, fission provides another sustainable nuclear energy source available for as long as we can reasonably imagine Homo sapiens. Having disposed of our fears, how far can we ride the fission neutron into the future, and what role could nuclear energy have in ensuring a sustainable global future?
Our new global, strategic, and market analyses show that the impact of climate change can be mitigated by introducing non-carbon hydrogen as a fuel in transportation; that nuclear electricity based on current advanced designs can supply the hydrogen fuel that is needed, plus the electricity, in a distributed system; that a potential synergism exists between wind and nuclear hybrid energy systems, when a balanced portfolio of electricity and hydrogen production is introduced that is market driven; and as a result, advanced designs and fuel cycles provide an economical, secure, and safe energy future.
A manageable deployment of nuclear, solar, wind, and any other non-carbon sources of electricity has the potential to profoundly alter the future prospects for the Earth's atmosphere.
Inaction for just one decade in embarking on this course is projected to raise all СO2 concentrations by 20 parts per million and estimated temperature by about 0.13®C. These increases should be set in the context of a 4,000-reactor deployment, which is projected to reduce СO2 by more than 95 ppm and temperature by more than 0.6®C. Viewed in the context of the capital required to implement the various stages of nuclear deployment, delay carries an extremely heavy price tag.
The future could well become the Hydrogen Age. A major reduction in greenhouse gases worldwide can be obtained by nuclear electric production of hydrogen. This need can be met by deployment of both current and advanced reactor designs and by the integration of the electric grid with the hydrogen economy. What's more, a robust nuclear-hydrogen infrastructure can provide the framework for incorporating energy from wind, solar, and other diffuse energy sources that may become more important as their technology improves.
It stands the longstanding reflexes of the environmental movement on its head, 1 know. But embracing nuclear power is an extraordinarily green idea. It is the first necessary step toward saving modern society, familiar ecosystems, and indeed the planet itself.
Romney B. Duffey is principal scientist at Atomic Energy of Canada Ltd. in Chalk River, Ontario.
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2005 by The American Society of Mechanical Engineers