Significance of the nuclear fuel cycle in the 21st century.pdf

Chapter 1 Significance of the Nuclear Fuel Cycle in the 21 st Century Kenneth L Nash 1 Gregg J Lumetta2 Sue B Clark1 and Judah Friese 2 1Chemistry Department Washington State University P O Box 644630 Pullman WA 99164 4630 2Pacific Northwest National Laboratory P O Box 999 Richland WA 99352 Summary The combined effects of increasing industrialization around the world the threat of global climate change and decreasing availability of clean fossil fuels will make the development of alternative energy sources more important in the coming decades For fission based nuclear power to contribute significantly to future energy supplies it will be essential to maintain the improvements that have been made in plant operational efficiency to license geological repositories for waste disposal and to consider again the issue of recycling of spent nuclear fuels to recover its fuel value and to reduce the long term radiotoxicity of the wastes In this chapter we present an overview of the nuclear fuel cycle from spent fuel recycling through the repository perance in the context of its importance to energy production in the 21 s t Century 2006 American Chemical Society 3 Downloaded by CORNELL UNIV on March 24 2013 http pubs acs org Publication Date June 9 2006 doi 10 1021 bk 2006 0933 ch001 In Separations for the Nuclear Fuel Cycle in the 21st Century Lumetta G et al ACS Symposium Series American Chemical Society Washington DC 2006 4 Energy Demand and Geopolitical Situation At the beginning of the 21 s t Century the world faces an unprecedented combination of energy and environment related challenges At the same time that countries with large populations and underdeveloped infrastructure are engaging in a rapid modernization industrialization of their economies we are becoming increasingly aware of the negative impacts of reinjecting fossil carbon into the environment as we consume fossil fuels to sustain the global economy The transation of poor economies into more modern versions is desirable for the stability of the world as the poverty associated with underdevelopment is at the root of many social ills However increased demand for fossil fuels will simultansouely have the effect of increasing the rate of release of C 02 into the atmosphere and diminishing supplies of fossil carbon at an increasingly rapid rate Though definitive conclusions cannot be drawn because the entire ecosystem is far too complex to reliably model there are increasing indications that global climate change could result in severe environmental degradation which in turn might result in significant social upheaval To sustain development of modern societies capable of supporting a growing population nuclear power based on fission combined with effective energy conservation may be the most rational approach to avoiding the impacts of a runaway greenhouse atmosphere To further complicate the picture it is likely that at some point in the future fossil carbon will become more valuable as a chemical feedstock than it is as a source of energy Hoffert and coworkers 1 analyzed the global energy situation in a featured paper in Science entitled Advance Technology Paths to Global Climate Stability Energy for a Greenhouse Planet They reported that Current global power consumption is 12 TW 10 1 2 Watts is 85 fossil fueled Atmospheric C02 was 275 ppm in 1900 is 370 ppm in 2000 will be 550 ppm in 2100 They conclude that we will need 15 TW of emission free power by 2050 to stabilize atmospheric C 02 at 550 ppm These authors further indicate that fission based nuclear power is the only presently developed technology that could deliver this perance They further suggest that known terrestrial reserves of uranium are inadequate to sustain this level of power production if we utilize only the fissile 2 3 5U that is present They conclude that it is imperative that development begin immediately on a serious international effort to close the nuclear fuel cycle and to breed additional fissile plutonium Downloaded by CORNELL UNIV on March 24 2013 http pubs acs org Publication Date June 9 2006 doi 10 1021 bk 2006 0933 ch001 In Separations for the Nuclear Fuel Cycle in the 21st Century Lumetta G et al ACS Symposium Series American Chemical Society Washington DC 2006 5 In recent years a number of books have been published that consider the possible impacts of the combined effects of population growth continued fossil fuel consumption and increased industrialization On the Editor s Page of the March 15 2004 edition of Chemical and Engineering News Rudy M Baum reviewed Out of Gas The End of the Age of Oil by David Goodstein and Frank J Gilloon Baum characterized the book as a simultaneously brilliant polemic and a clear examination of the chemistry and physics of global energy issues He notes that the book opens with an apocalyptic vision from the authors The world will soon start to run out of conventionally produced cheap oil If we manage to overcome that shock by shifting the burden to coal or natural gas life may go on more or less as it has been until we run out of all fossil fuels by the end of the century And by the time we have burned up that fuel we may well have rendered the planet unfit for human life Even if human life does go on civilization as we know it will not survive unless we can find a way to live without fossil fuels In the following week s edition Chemical and Engineering News March 22 2004 Baum continued on the Editor s page with A Challenge We Must Meet II making the following observations Nuclear energy will be an essential component of any strategy for weaning humanity from fossil fuels While fissile uranium 235 is also a limited resource breeder reactor technologies exist for converting 2 3 8 U to fissile plutonium 239 and thorium 232 to fissile 2 3 3U Breeder reactors can extend the supply of the earth s fissile material several hundred fold enough to last at least several centuries He continues Problems of spent reactor fuel and 2 3 9Pu do not compare to the economic and environmental crises that our continued dependence on fossil fuels is guaranteed to engender As will be discussed below there are no energy production technologies that do not include some cost Accepting the assumption of limited fossil fuel resources and the environmental dangers of global warming through the greenhouse effect it can reasonably be argued that the path forward will demand that we explore all possible avenues for energy production for both electricity and transportation fuels and increase emphasis on efficient usage of the power we produce With the planet s population presently approaching 6 5 billion and projected doubling Downloaded by CORNELL UNIV on March 24 2013 http pubs acs org Publication Date June 9 2006 doi 10 1021 bk 2006 0933 ch001 In Separations for the Nuclear Fuel Cycle in the 21st Century Lumetta G et al ACS Symposium Series American Chemical Society Washington DC 2006 6 of that number in the next century energy water food production and environmental quality will become paramount issues Environmental Impact of Energy Production Although it is essential that sufficient energy be made available to raise the standard of living of the world s populace it is equally important that the production of that energy does not result in a concomitant decline in living standards due to environmental degradation For this reason future energy decisions must take into account the environmental impacts of energy technologies deployed All s of energy production impact the environment in some manner Direct comparison of the environmental impacts of different energy sources can be somewhat problematic but the application of life cycle assessments can be used to compare different energy production s on a common basis 2 3 Life cycle assessments are based on a cradle to grave approach to analyzing environmental impacts For that reason they examine extraction of raw materials production of system components the actual energy production technology and waste disposal They typically do not account for factors that are difficult to quantify such as land utilization and impacts to visual landscapes Gagnon et al recently published a comparison of life cycle assessments pered on a number of different electricity generation options 4 Figure 1 summarizes the results of that study The figure presents results for four key environmental factors including greenhouse gas emissions acid rain potential as represented by S02 emissions land use requirements a parameter often not considered in life cycle analyses and the energy payback ratio that is how much energy is produced divided by the energy invested for its production Based on the Gagnon study run of the river hydropower by far has the best perance in terms of greenhouse gas emissions Nuclear power is comparable with wind solar power and hydropower with a reservoir Not surprisingly all the fossil fuel based options compare poorly in the category of greenhouse gas emissions Similarly run of the river hydropower has the least impact in terms of S02 emissions with fossil fueled power production being the most impactful Nuclear power is nearly comparable to run of the river hydropower in this respect Nuclear energy has the least impact in terms of land use although the analysis by Gagnon et al did not include land use associated with long term waste disposal which would be expected to adversely affect the land use assessment for the nuclear option Downloaded by CORNELL UNIV on March 24 2013 http pubs acs org Publication Date June 9 2006 doi 10 1021 bk 2006 0933 ch001 In Separations for the Nuclear Fuel Cycle in the 21st Century Lumetta G et al ACS Symposium Series American Chemical Society Washington DC 2006 7 Hydropower options have the best payback in terms of the amount of energy produced versus the amount expended Wind energy also has a large energy payback ratio Nuclear power fares well in comparison to the other energy production options examined It should be pointed out that in the case of the renewable energy sources i e solar wind and run of the river hydropower the life cycle assessments results reported by Gagnon et al can be viewed as incomplete as was pointed out by those authors The life cycle assessments did not take into account the reliability of the individual power sources The reliability of these power sources are low because the driving force is not always present at a level necessary for efficient electricity production In other words the sun does not always shine on the photovoltaic cells the wind does not always adequately turn the wind turbines and river flows can be highly variable the maintenance of a reservoir eliminates this unreliablility for hydropower but at the expense of submerged landscapes a For these reasons the popular renewable energy technologies cannot always provide power on demand Thus solar and wind power generating stations typically do not stand alone and must be backed up by more conventional technologies so that the electric power grid system remains balanced 4 5 If powered by fossil fuels this backup generating capacity could be running at less than peak efficiency Consideration of this backup generating capacity should be factored into the overall environmental impact of wind and solar technology and run of the river hydropower On the other hand the back end of the nuclear fuel cycle is often neglected in life cycle assessments because of the uncertainties associated with ultimate waste disposition The environmental impacts associated with ultimate waste disposition might be decreased if the currently planned disposal of irradiated fuel were replaced by a plan involving fuel reprocessing and might be decreased even more by implementing partitioning and transmutation P Lumetta G et al ACS Symposium Series American Chemical Society Washington DC 2006 Greenhouse Gas Emissions 104 10 3 10 2 101 1 0 a b c d e f g h i 0 k I SO2 Emissions 104 10 3 102 101 10 10 1 a b c d e f g h i G k I Downloaded by CORNELL UNIV on March 24 2013 http pubs acs org Publication Date June 9 2006 doi 10 1021 bk 2006 0933 ch001 In Separations for the Nuclear Fuel Cycle in the 21st Century Lumetta G et al ACS Symposium Series American Chemical Society Washington DC 2006 Direct Land Requirements Energy Payback Ratio 1000 Q 100 O 10 c W CM 10 km tpu 1 o O Q 0 1 C 111 a b c d e f g h i 0 k I a b c d e f g h i 0 k I Figure 1 Summary of Environmental Factors for Various Electricity Generating Options Based on Life Cycle Assessment adaptedfrom reference 4 a Hydro w Reservoir b Diesel 0 25 S c Heavy Oil 1 5 S w o S02 Scrubbing d Hydro Run of River e Coal 1 S without S02 Scrubbing J Coal 2 S w S02 Scrubbing g Nuclear h Natural Gas i Fuel Cell H2from gas reing j Biomass Plantation k Wind I Solar PV Downloaded by CORNELL UNIV on March 24 2013 http pubs acs org Publication Date June 9 2006 doi 10 1021 bk 2006 0933 ch001 In Separations for the Nuclear Fuel Cycle in the 21st Century Lumetta G et al ACS Symposium Series American Chemical Society Washington DC 2006 10 those of coal oil and even natural gas fired turbines if the link of carbon dioxide to global warming is accepted Nuclear power also compares vary favorably with solar and wind power and in contrast to these technologies nuclear plants can be configured to provide continuous on demand power no matter what the weather Role of Nuclear Power The world wide production of electricity by nuclear fission is at present nearly 351 gigawatts electric Gwe generated from 438 operating nuclear reactors and accounting for about 16 of electricity production worldwide The spent fuel from power production reactors is about 1 0 1 5 transuranium TRU actinides 3 5 4 0 fission products 95 still slightly enriched uranium upon discharge from the reactor There are three choices for the management of the spent fuel a recycle to recover valuable components reprocessing with or without actinide partitioning and transmutation b permanent geologic disposal as waste single pass fuel cycle or c long term monitoring after stabilization for surface or near surface storage World wide both byproduct recycle and monitoring of spent fuel in storage are done Option b is the present official policy for dealing with spent fuel from commercial reactors in the U S It must also be noted that the need for a geologic repository does not disappear in option a A geologic repository will still be essential for the sequestration of radioactive wastes from reprocessing from the surrounding environment Unfortunately after more than 30 years of continuous investigation no repositories for permanent geologic disposal of either spent reactor fuels or vitrified reprocessing wastes have been licensed Clearly safe disposal of either spent fuel or the high level waste HLW generated during reprocessing of spent fuel is a matter of great environmental concern 6 Waste disposal and the increased risk of proliferation of nuclear weapons are the two major issues standing in the way of further implementation of this otherwise environmentally friendly technology Furthermore a recent analysis projecting how fission based nuclear power could favorably impact greenhouse gas emissions emphasizes the need for breeding additional fuel to satisfy a projected long term shortage or fuel for fission reactors 1 Meeting this demand can only be accomplished by closing the loop on spent fuel reprocessing Overall the major factors that must be addressed for the expansion of fission based nuclear power from the present level to its full potential include the following 1 safety and efficiency of energy production must be maintained 2 a strategy or strategies for the final disposal of the radioactive byproducts of fission must be developed Downloaded by CORNELL UNIV on March 24 2013 http pubs acs org Publication Date June 9 2006 doi 10 1021 bk 2006 0933 ch001 In Separations for the Nuclear Fuel Cycle in the 21st Century Lumetta G et al ACS Symposium Series American Chemical Society Washington DC 2006 11 3 mistrust by the general public and in many cases elected officials and stockholders for the technology must be overcome and 4 the comparatively high initial installation costs for nuclear power plants must be reduced Ultimately it will become necessary to convert fertile 2 3 8U and or 2 3 2Th to fissile 2 3 9Pu and 2 3 3U if nuclear power is to assume an increasing role Before this will happen it will be necessary to overcome 5 the comparatively low price and relative abundance of natural uranium 6 concerns about the proliferation of nuclear weapons and to develop 7 a next generation reprocessing capability that responds to 21 s t Century demands for protection of the environment Some of these factors could yield to increased education of the public to reduce misunderstandings Item 3 some have already been greatly improved Item 1 and require only preservation of the gains that have been made some while not definitively solved have perhaps yielded a bit to decades of investigation Item 2 some will simply have to await a correction from natural market factors Item 5 and technological improvements Item 4 The issue of weapons proliferation can be most efficaciously addressed by political means i e international agreements with serious monitoring consequences for violators and vigilance for those who seek to expand the availability of nuclear materials for weapons The proliferation of nuclear weapons can also be hindered by transmutation which results in either the destruction of fissile materials or their conversion into materials less suitable for the production of efficient fission weapons for example changing isotopic mixture of Pu through successive neutron capture Besides environment protection the next generation reprocessing capability envisioned in item 7 will also have to be proliferation proof Having garnered substantial experience during the past 50 years with nuclear science and technology humanity may be poised for an acceptable expansion of this segment of our energy production capacity In the following sections some aspects of the current state of affairs in nuclear energy production are discussed Management of Irradiated Fuel Spent fuel freshly discharged from a reactor is intensely radioactive and generates substantial heat Over a period of a few decades most of the penetrating radiation decays to comparatively low levels though the spent fuels retain sufficient heat and penetrating radiation to have an impact on geological Downloaded by CORNELL UNIV on March 24 2013 http pubs acs org Publication Date June 9 2006 doi 10 1021 bk 2006 0933 ch001 In Separations for the Nuclear Fuel Cycle in the 21st Century Lumetta G et al ACS Symposium Series American Chemical Society Washington DC 2006 12 systems From 30 300 years the long lived fission products 1 3 7Cs and 9 0Sr dominate the radiation dose From 300 10 000 years the radiation dose is dominated by plutonium and americium isotopes From 10 000 250 000 years plutonium isotopes are dominant while 2 3 7Np l 2 9I and 9 9Tc are the most important beyond 250 000 years The latter three species are particularly troublesome from a regulatory perspective as they exist in generally soluble s under environmental conditions At present half of the world s spent nuclear fuel is managed in a once through cycle The other half is reprocessed to recycle U and Pu Though a great deal of research has been done no country has as yet committed to further partition and transmute long lived radioactive byproducts fission products and minor actinides Deep geological repositories are universally considered the preferred option for the long term isolation of either spent fuel or reprocessing residues from the biosphere It is widely believed that such a repository properly sited and constructed can effectively accomplish the necessary sequestration for either spent fuel or high level reprocessi