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Comparison of accelerator-based with reactor-based nuclear waste transmutation schemes

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Abstract

An overview of the most significant studies in the last 35 years of partitioning and transmutation of commercial light water reactor spent fuel is given. Recent Accelerator-based Transmutation of Waste (ATW) systems are compared with liquid-fuel thermal reactor systems that accomplish the same objectives. If no long-lived fission products (e.g., 99Tc and 129I) are to be burned, under ideal circumstances the neutron balance in an ATW system becomes identical to that for a thermal reactor system. However, such a reactor would need extraordinarily rapid removal of internally-generated fission products to remain critical at equilibrium without enriched feed. The accelerator beam thus has two main purposes (1) the burning of long-lived fission products that could not be burned in a comparable reactor's margin (2) a relaxing of on-line chemical processing requirements without which a reactor-based system cannot maintain criticality. Fast systems would require a parallel, thermal ATW system for long-lived fission product transmutation. The actinide-burning part of a thermal ATW system is compared with the Advanced Liquid Metal Reactor (ALMR) using the well-known Pigford-Choi model. It is shown that the ATW produces superior inventory reduction factors for any near-term time scale.

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... Cheng and Cerbone [12] analyzed and compared two tokamak based transmutation reactors: (1) minor actinide (MA) fueled and (2) "Pu-assisted" (Pu+MA fuel) which they determined could operate at a Pfus=200 MW, k-eff ~0. 8 [23]. ...
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... There is a general consensus that significantly higher levels of actinide destruction can be achieved by repeated recycling of spent fuel in sub-critical reactors with a neutron source. An accelerator-spallation neutron source has been extensively studied for this application [1][2][3][4][5][6]. ...
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... Special transmutation facilities for these species are also an option. 34 The only other long-lived radioactive species that would go to the repository would be species such as 59 Ni, 93 Zr, and some other species that are not soluble in water. ...
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... An accelerator-driven system (ADS) consists of a lattice of fissile material in a subcritical configuration with the power of the system driven mainly by an intense accelerator source of neutrons. A variety of ADS designs have been studied in the past [1][2][3][4][5], and a number of accelerator-driven neutron sources have been designed and built over the years (including fusion sources using D-T fusion, spallation neutron sources using a proton beam, and photoneutron sources using an electron accelerator). However, an ADS system of significant power has never been built and operated. ...
Article
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... In the past few years, a research programme on ADSs has started to crystallize even in the U.S.A. and the interest has shifted from thermal spectrum designs [80,81] to fast spectrum systems [82], based on Pb/Bi coolant technology. The ATW (Accelerator Transmutation of Waste) programme at LANL envisions incineration of TRU and LLFP coming directly from LWRs in a sub-critical reactor using metallic fuel -an admixture of TRU with zirconium (85%Zr-15%TRU) and driven by a super-conducting linac which design is based on the tentative proposal for the Accelerator Production of Tritium project. ...
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Neutronics-processing interface parameters have large impacts on the neutron economy and transmutation performance of an aqueous-based Accelerator Transmutation of Waste (ATW) system. A detailed assessment of the interdependence of these blanket neutronic and chemical processing parameters has been performed. Neutronic performance analyses require that neutron transport calculations for the ATW blanket systems be fully coupled with the blanket processing and include all neutron absorptions in candidate waste nuclides as well as in fission and transmutation products. The effects of processing rates, flux levels, flux spectra, and external-to-blanket inventories on blanket neutronic performance were determined. In addition, the inventories and isotopics in the various subsystems were also calculated for various actinide and long-lived fission product transmutation strategies.
Conference Paper
Actinide burning (AB) is a concept that would greatly reduce the amounts of long-lived transuranic (TRU) nuclides in wastes going to the repository. The concept is implemented by intensified processing to reduce actinide losses to wastes and subsequent recycling of the actinides to liquid-metal reactors (LMRs). As a result, AB may simultaneously (a) simplify waste management by fissioning the TRU nuclides to shorter lived nuclides, (b) generate electricity, and (c) greatly extend uranium resources. In previous studies, researchers at the Oak Ridge National Laboratory compared the long-term repository risk reduction from AB to increases in cost and contemporary risk. They concluded that incentives for AB did not exist. Similar conclusions were reached by European investigators. During the decade since these studies, there have been two major developments related to the incentives for AB. The first is that the challenges inherent in characterizing, licensing, and funding a repository have become clearer and are larger than originally anticipated. The second development is the establishment of an Environmental Protection Agency (EPA) standard and US Nuclear Regulatory Commission (NRC) criteria to provide a specific measure of repository acceptability, as opposed to the many assumptions and calculations inherent in previous analyses. Consequently, the incentives for AB have been reexamined in the context of these developments and are discussed in this paper.
Conference Paper
A small fast reactor such as the Fast Flux Test Facility can be an effective device for destroying long-lived fission products such as {sup 99}Tc and {sup 129}I. There are several potential core configuration options using both fast and moderated neutron spectra. The calculated Doppler reactivity coefficient for {sup 99}Tc was 60% of the value for {sup 238}U on a per atom basis. Replacing {sup 238}U with {sup 99}Tc in waste burn applications has the positive attributes of reduced parasitic capture in uranium and enhanced fission product destruction, while retaining a substantial Doppler effect. A modular liquid metal reactor system could support about 8 to 10 comparably sized conventional light water reactors.
Conference Paper
The 50 years of activities following the discovery of self-sustaining fission chains have given rise to a buildup of roughly 900 tons of manmade transuranics. Of the total, about 260 tons of Pu{sup 239} were generated for use in weapons while the remainder were generated as a byproduct of electrical power produced worldwide by the commercial thermal nuclear power industry. What is to be done with these actinides? The options for disposition include interminable storage, burial, or recycle for use. The pros and cons of each option are being vigorously debated regarding the impact upon the issues of human and ecological risk -- both current and future; weapons proliferation potential -- both current and future; and total life cycle benefits and costs. As to the options for utilization, commercial uses for actinides (uranium and transuranics) are of limited diversity. The actinides have in the past and will in the future find application in large scale mostly by virtue of their ability to release energy through fission, and here their utility is unmatched -- whether the application be in commercial electricity generation or in armaments. The integral Fast Reactor (IFR) fuel cycle offers a number of features for management of the current and future burden of manmade transuranic materials and for capturing the energy content of the U{sup 238}. These features are discussed here.
Article
A study was made to examine the conceptual feasibility of a molten-salt power reactor fueled with denatured /sup 235/U and operated with a minimum of chemical processing. Because such a reactor would not have a positive breeding gain, reductions in the fuel conversion ratio were allowed in the design to achieve other potentially favorable characteristics for the reactor. A conceptual core design was developed in which the power density was low enough to allow a 30-year life expectancy of the moderator graphite with a fluence limit of 3 x 10/sup 26/ neutrons/m/sup 2/ (E > 50 keV). This reactor could be made critical with about 3450 kg of 20% enriched /sup 235/U and operated for 30 years with routine additions of denatured /sup 235/U and no chemical processing for removal of fission products. A review of the chemical considerations assoicated with the conceptual fuel cycle indicates that no substantial difficulties would be expected if the soluble fission products and higher actinides were allowed to remain in the fuel salt for the life of the plant.
Article
The authors use the Los Alamos LAHET Code System (LCS)/CINDER`90 suite of codes in a variety of spallation neutron source applications to predict neutronic performance and as a basis for making engineering decisions. They have broadened their usage of the suite from designing LANSCE and the next generation of spallation neutron sources for materials science and nuclear physics research to designing a target system for Accelerator Production of Tritium and Accelerator Transmutation of Waste. While designing, they continue to validate the LCS/CINDER`90 code suite against experimental data whenever possible. In the following, they discuss comparisons between calculations and measurements for: integral neutron yields from a bare-target of lead; fertile-to-fissile conversion yields for thorium and depleted uranium targets; dose rates from the LANSCE tungsten target; energy deposition in a variety of light and heavy materials; and neutron spectra from LANSCE water and liquid hydrogen moderators. The accuracy with which the calculations reproduce experimental results is an indication of their confidence in the validity of their design calculations.
Conference Paper
An attractive option for dealing with the problems of nuclear waste disposal includes reprocessing spent light water reactor fuel to recover and recycle the uranium and plutonium, partitioning key long-lived actinides and fission products, and transmuting recovered and purified very long-lived problem isotopes. Most transmutation studies have dealt with the minor actinides; however, a successful transmutation strategy also must address the long-lived fission products {sup 99}Tc and {sup 129}I. Destruction of {sup 99}Tc and {sup 129}I is accomplished by a single neutron-capture event, followed by very rapid decay to stable {sup 100}Ru and {sup 130}Xe, respectively. The probability of a neutron-capture event is significantly higher in a moderated neutron spectrum than in a fast spectrum. Studies have shown that effective transmutation rates of {sup 99}Tc and {sup 129}I potentially can be achieved in specially designed metal hydride assemblies in fast reactors or advanced accelerator-driven devices. A successful transmutation experiment for the key long-lived fission products {sup 99}Tc and {sup 129}I was performed using a metal-hydride-moderated environment in the radial reflector region of a sodium-cooled fast reactor with reasonably good agreement between measured and calculated transmutation rates. The underprediction of both transmutation rates is likely a result of axial gradients in the low-energy neutron flux over the target regions.
Conference Paper
The purpose of the Los Alamos National Laboratory Accelerator Transmutation of Nuclear Waste (ATW) project is the substantial reduction in volume of this country`s long-lived high-level radioactive waste in a safe and energy efficient manner. An evaluation of the Accelerator Transmutation of Nuclear Waste concept has four aspects; material balance, energy balance, performance and cost. An evaluation of the material balance compares the amount of long-lived high-level waste transmuted with the amount and type of waste created in the process. One component of the material balance is the activation of structural materials over the lifetime of the transmutation reactor. An activation analysis has been performed on four structure regions of the reaction vessel: the tungsten target; the lead target and annulus; the Zircalloy and aluminum tubing carrying the actinide slurry and; the stainless steel tank.
Article
The performance of liquid centrifugation for nuclear waste partitioning is examined for the Accelerator Transmutation of Waste Program currently under study at the Los Alamos National Laboratory. Centrifugation might have application for the separation of the LiF-BeF{sub 2} salt from heavier radioactive materials fission product and actinides in the separation of fission product from actinides, in the isotope separation of fission-product cesium before transmutation of the {sup 137}Cs and {sup 135}Cs, and in the removal of spallation product from the liquid lead target. It is found that useful chemical separations should be possible using existing materials for the centrifuge construction for all four cases with the actinide fraction in fission product perhaps as low as 1 part in 10{sup 7} and the fraction of {sup 137}CS in {sup 133}Cs being as low as a few parts in 10{sup 5}. A centrifuge cascade has the advantage that it can be assembled and operated as a completely closed system without a waste stream except that associated with maintenance or replacement of centrifuge components.
Article
During the 1970s, the United States and other countries thoroughly evaluated the options for the safe and final disposal of high-level radioactive wastes (HLW). The worldwide scientific community concluded that deep geologic disposal was clearly the most technically feasible alternative. They also ranked the partitioning and transmutation (P-T) of radionuclides among the least favored options. A 1982 report by the International Atomic Energy Agency summarized the key reasons for that ranking: ``Since the long-term hazards are already low, there is little incentive to reduce them further by P-T. Indeed the incremental costs of introducing P-T appear to be unduly high in relation to the prospective benefits.`` Recently, the delays encountered by the US geologic disposal program for HLW, along with advanced in the development of P-T concepts, have led some to propose P-T as a means of reducing the long-term risks from the radioactive wastes that require disposal and thus making it easier to site, license, and build a geologic repository. This study examines and evaluates the effects that introducing P-T would have on the US geologic disposal program.
Article
Transmutation of long-lived nuclear waste currently stored in spent reactor fuels may represent an attractive alternative to deep geologic disposal. The aqueous-based accelerator transmutation of waste (ATW) concept uses a proton accelerator to produce a 1.6-GeV, 250-mA ( ca. 400 MW) beam that is split four ways and directed to four D{sub 2}O-cooled solid W-Pb composite targets. Each target in turn is centered in a heavy water moderated, highly multiplying, actinide (oxide)-slurry blanket. The target-blanket system for ATW resides at an interface separating two major systems that are crucial to the economic and technical success of the concept: (a) the high-energy (power-intensive) accelerator delivering 0.8 to 1.6 GeV protons to the high-Z spallation neutron source and (b) the chemical-plant equipment (CPE) that provides feedstock appropriate for efficient and effective transmutation. Parametric studies have been performed to assess the effects of the target-blanket on overall system performance with regard to neutron economy, chemical-processing efficiency and thermal-hydraulic design options. Based on these parametric evaluations, an interim base-case aqueous-slurry ATW design was selected for more detailed analysis. This base-case target-blanket consists of an array of Zr-Nb pressure tubes placed in a heavy water moderator surrounding a heavy-water-cooled W-Pb target. Neutronics and thermal-hydraulic calculations indicate that each of the four ATW target-blanket modules operating with a neutron multiplication k{sub eff} = 0.95 can transmute the actinide waste and the technetium and iodine waste from ca. 2.5 light water reactors. By recovering the fission heat, sufficient electricity can be produced both to operate the accelerator and to supply power to the grid for revenue generation. These broad-based parametric studies have provided guidance to a preliminary conceptual engineering design of the aqueous-slurry ATW blanket concept.
Article
This report is concerned with an overall assessment of the feasibility of and incentives for partitioning (recovering) long-lived nuclides from fuel reprocessing and fuel refabrication plant radioactive wastes and transmuting them to shorter-lived or stable nuclides by neutron irradiation. The principal class of nuclides considered is the actinides, although a brief analysis is given of the partitioning and transmutation (P-T) of /sup 99/Tc and /sup 129/I. The results obtained in this program permit us to make a comparison of the impacts of waste management with and without actinide recovery and transmutation. Three major conclusions concerning technical feasibility can be drawn from the assessment: (1) actinide P-T is feasible, subject to the acceptability of fuels containing recycle actinides; (2) technetium P-T is feasible if satisfactory partitioning processes can be developed and satisfactory fuels identified (no studies have been made in this area); and (3) iodine P-T is marginally feasible at best because of the low transmutation rates, the high volatility, and the corrosiveness of iodine and iodine compounds. It was concluded on the basis of a very conservative repository risk analysis that there are no safety or cost incentives for actinide P-T. In fact, if nonradiological risks are included, the short-term risks of P-T exceed the long-term benefits integrated over a period of 1 million years. Incentives for technetium and iodine P-T exist only if extremely conservative long-term risk analyses are used. Further RD and D in support of P-T is not warranted.
Conference Paper
A parametric systems model of the ATW [Accelerator Transmutation of (Nuclear) Waste] has been used to examine key system tradeoffs and design drivers on the basis of unit costs. This model has been applied primarily to the aqueous-slurry blanket concept for an ATW that generates net-electric power from the fissioning of spent reactor fuel. An important goal of this study is the development of essential parametric tradeoff studies to aid in any eventual engineering design of an ATW that would burn and generate net- electric power from spent reactor fuel.
Article
ORIGEN2 is a versatile point-depletion and radioactive-decay computer code for use in simulating nuclear fuel cycles and calculating the nuclide compositions and characteristics of materials contained therein. It represents a revision and update of the original ORIGEN computer code, which was developed at the Oak Ridge National Laboratory (ORNL) and distributed worldwide beginning in the early 1970s. Included in ORGEN2 are provisions for incorporating data generated by more sophisticated reactor physics codes, a free-format input, and a highly flexible and controllable output; with these features, ORIGEN2 has the capability for simulating a wide variety of fuel cycle flow sheets. The decay, cross-section, fission product yield, and photon emission data bases employed by ORIGEN2 have been extensively updated, and the list of reactors that can be simulated includes pressurized water reactors, boiling water reactors, liquid-metal fast breeder reactors, and Canada deuterium uranium reactors. A number of verification activities have been undertaken, including (a) comparison of ORIGEN2 decay heat results with both calculated and experimental values, and (b) comparison of predicted spent fuel compositions with measured values. The agreement between ORIGEN2 and the comparison bases is generally very good. Future work concerning ORIGEN2 will involve continued maintenance and user support along with additional verification studies and limited modifications to enhance its flexibility and usability. ORIGEN2 can be obtained, free of charge, from the ORNL Radiation Shielding Information Center.
Conference Paper
Fast-spectrum advanced liquid-metal-cooled reactors (ALMRs) have been proposed to transmute transuranic (TRU) elements (neptunium, plutonium, americium, and cadmium) recovered from light water reactor (LWR) spent fuel that would otherwise be emplaced in a geologic repository. The purpose is to reduce the inventory of TRU in the high-level waste (HLW) to reduce the risks from actinides in a geologic repository for HLW. New chemical processes for LWR and ALMR spent fuel would be developed with TRU decontamination factors {gamma} of 10{sup 3} to 10{sup 5}, assuming that transmutation in ALMRs would reduce the amount of TRU to be sent to a geologic repository by factors of 10{sup 3} to 10{sup 5}. In this paper, the authors calculate reduction factors actually obtainable and the length of time ALMRs must operate to reduce the TRU inventory by a given amount.
Article
Elimination of long-lived transplutonium actinides by fissioning in a generic actinide burner reactor (a reactor fueled solely with waste actinides) was investigated. The results showed that actinide elimination by fissioning is enhanced by increasing the average energy of the neutron flux spectrum. In addition, the reactivity worths and the fission-to-capture rate ratios of the individual actinide nuclides increased with increasing flux spectrum energy. This suggests that specially designed fast reactors of relatively small size and having metal alloy fuel may effectively dispose of the waste actinides produced by several large light water reactors in a mixed reactor community. The fuel value of waste actinides was studied, and the replacement of at least some conventional mixed-oxide fast reactor fuel by waste actinides (to conserve a fuel resource) was proposed. It is calculated that the time required to reach equilibrium actinide concentrations in the reactor core, after many refueling periods, is shorter for reactors having higher neutron flux energies. Also, increasing the specific power density within the reactor core both decreases the equilibrium actinide concentrations in the core and increases the time required for equilibrium conditions.
Conference Paper
It has been proposed that light water reactor spent fuel now destined for a geologic repository be reprocessed with high-yield recovery of all transuranics and that the recovered transuranics be fissioned in liquid-metal fast reactors. The reprocessing waste would be emplaced in the geologic repository. The purpose would be to reduce the risk from actinides in the geologic repository. In this paper, the author presents calculations of the relative risk of actinides and fission products in a tuff repository and reviews the risk estimated by the actinide-burning program. It is shown that the proposed reduction in actinide inventory in the waste would make only a negligible reduction in the radiation dose from contaminated water from the repository.
Conference Paper
A strategy of actinide burnup in LMFBRs is being investigated as a waste management alternative to long term storage of high level nuclear waste. This strategy is being evaluated because many of the actinides in the waste from spent-fuel reprocessing have half-lives of thousands of years and an alternative to geological storage may be desired. From a radiological viewpoint, the actinides and their daughters dominate the waste hazard for decay times beyond about 400 years. Actinide burnup in LMFBRs may be an attractive alternative to geological storage because the actinides can be effectively transmuted to fission products which have significantly shorter half-lives. Actinide burnup in LMFBRs rather than LWRs is preferred because the ratio of fission reaction rate to capture reaction rate for the actinides is higher in an LMFBR, and an LMFBR is not so sensitive to the addition of the actinide isotopes. An actinide target assembly recycle scheme is evaluated to determine the effects of the actinides on the LMFBR performance, including local power peaking, breeding ratio, and fissile material requirements. Several schemes are evaluated to identify any major problems associated with reprocessing and fabrication of recycle actinide-containing assemblies. The overall efficiency of actinide burnout in LMFBRs is evaluated, and equilibrium cycle conditions are determined. It is concluded that actinide recycle in LMFBRs offers an attractive alternative to long term storage of the actinides, and does not significantly affect the performance of the host LMFBR. Assuming a 0.1 percent or less actinide loss during reprocessing, a 0.1 percent loss of less during fabrication, and proper recycle schemes, virtually all of the actinides produced by a fission reactor economy could be transmuted in fast reactors.
Conference Paper
A strategy of actinide burnup in LMFBRs has been investigated as a waste management alternative to long-term storage of high level nuclear waste. This strategy has been evaluated because many of the actinides in the waste from spent-fuel reprocessing have half-lives of thousands of years and an alternative to geological storage may be desired. By burning the actinides in LMFBRs the long-lived isotopes can be effectively transmuted to fission products which have significantly shorter half-lives. Actinide burnup in LMFBRs rather than LWRs is preferred because the fission to capture reaction rate ratios are higher in the LMFBR, and the LMFBR performance is not highly sensitive to the addition of the actinide waste material. An actinide target assembly recycle scheme has been analyzed to determine the effects of the actinides on the LMFBR performance, including local power peaking, breeding ratio, and fissile material requirements. The overall efficiency of actinide burnout in LMFBRs has been evaluated, and equilibrium cycle conditions have been determined. The results of the actinide recycle study indicate that the actinide wastes produced by a fission reactor economy could be transmuted in fast reactors with only a two percent penalty in the fissile loading requirements and a one to two percent penalty in the breeding ratio of the host reactors. The actinide target assemblies could be tailored to give a power distribution which is comparable to that of the standard fuel assemblies. However, the total shutdown decay heat from a target assembly would be approximately 43 percent greater than that from a standard assembly.
Conference Paper
The modular reactor concept, PRISM (power reactor, innovative, small module), originated by General Electric in conjunction with the integral fast reactor (IFR) metal fuel being developed by Argonne National Laboratory (ANL), is the reference US Department of Energy advanced liquid-metal reactor (ALMR). The reference ALMR is unique in several ways; for example, it can produce (or breed) substantially more fissile material than it consumes. It is also unique in that it has the capability to utilize as fuel the long-life radioactive actinides (primarily plutonium, and the minor actinides, neptunium, americium, and curium) present as waste in light water reactor (LWR) spent fuels. This capability provides a means for converting long-life actinide radioactive wastes to elements whose lifetimes and thus storage needs are much shorter, namely, hundreds of years. This could clearly focus and potentially alleviate a controversial aspect (waste disposal) of the nuclear option. While it does not change the need for, or timing of, an initial high-level waste (HLW) repository, the conversion of actinides could change in a dramatic way the time period required for safe storage of nuclear waste and potentially the number and criteria for future repositories. This work considers the potential for utilizing LWR actinides in the ALMR fuel cycle.
Article
A conceptual target and blanket design for an accelerator transmutation of waste system capable of transmuting the high-level waste stream from 2.5 light water reactors is described. Typically, four such target-blanket designs would be served by a single linear accelerator. The target consists of rows of solid tungsten rod bundles, cooled by heavy water and surrounded by a lead annulus. The annular blanket, which surrounds the target, consists of a set of actinide-oxide-slurry-bearing tubes, each 3 m long, surrounded by heavy water moderator. Heat is removed from the slurry tubes by passing the slurry through an external heat exchanger. Long-lived fission products are burned in regions that are separate from the actinides. Using the Monte Carlo codes LAHET and MCNP, a conceptual design for a beam current of 62.5 mA/target of 1.6-GeV protons has been developed. Preliminary engineering analyses on key system components have been performed. A preliminary layout of the concept and the associated primary-heat transport subsystems was developed, demonstrating a multiple-containment-boundary design philosophy.
Article
The feasibility of directly irradiating five long-lived fission products (LLFPs: {sup 79}Se, {sup 93}Zr, {sup 107}Pd, {sup 126}Sn, and {sup 135}Cs, each with a half-life greater than 10,000 years), by incorporating them into the target of an Accelerator Transmutation of Waste (ATW) system is discussed. The important parameters used to judge the feasibility of a direct irradiation system were the target's neutron spallation yield (given in neutrons produced per incident proton), and the removal rate of the LLFP, with the baseline incineration rate set at two light water reactors (LWRs) worth of the LLFP waste per year. A target was constructed which consisted of a LLFP cylindrical ''plug'' inserted into the top (where the proton beam strikes) of a 30 cm radius, 100 cm length lead target. {sup 126}Sn and {sup 79}Se were each found to have high enough removal rates to support two LWR's production of the LLFP per year of ATW operation. For the baseline plug geometry (5 cm radius, 30 cm length) containing {sup 126}Sn, 3.5 LWRs could be supported per year (at 75% beam availability). Furthermore, the addition of a {sup 126}Sn plug had a slightly positive effect on the target's neutron yield. The neutron production was 36.83{+-}.0039 neutrons per proton with a pure lead target having a yield of 36.29{+-}.0038. It was also found that a plug composed of a tin-selenide compound (SnSe) had high enough removal rates to burn two or more reactor years of both LLFPs simultaneously.
Book
The author draws on his experience as a freshman legislator in the Minnesota House of Representatives and his efforts to obtain neutral information in submitting a bill (House File 378) to require a safe and economic way to dispose of wastes as a precondition to nuclear power. He focuses on the questions of economics, safety, and need in evaluating the nuclear option and its alternatives. Some attention is given to the hidden power of nuclear energy in the context of cost, health hazards, and true national needs. As a result of his research, he concludes that radioactive waste management is far from either a technical or social solution; that nuclear plant costs are high relative to their reliability; that neither the fuel-cycle safety record nor the safety record of nuclear power plants is clear; and that the public is failing to push for available alternatives and to exercise its right to organize and participate in policy decisions. 131 references, 6 figures, 4 tables. (DCK)
Article
National strategies to manage nuclear waste from commercial nuclear power plants are analyzed and compared. The current strategy is to try to operate a repository at Yucca Mountain, Nevada, to dispose of high-level nuclear waste underground. The main alternatives involve temporary above-ground storage at a centralized facility or next to nuclear power plants. If either of these is pursued now, the analysis assumes that a repository will be built in 2100 for waste not subsequently put to use. The analysis treats various uncertainties: whether a repository at Yucca Mountain would be licensed, possible theft and misuse of the waste, innovations in repository design and waste management, the potential availability of a cancer cure by 2100, and possible future uses of nuclear waste. The objectives used to compare alternatives include concerns for health and safety, environmental and socioeconomic impacts, and direct economic costs, as well as equity concerns (geographical, intergenerational, and procedural), indirect economic costs to electricity ratepayers, federal government responsibility to manage nuclear waste, and implications of theft and misuse of nuclear waste. The analysis shows that currently building an underground repository at Yucca Mountain is inferior to other available strategies by the equivalent of $10,000 million to $50,000 million. This strongly suggests that this policy should be reconsidered. A more detailed analysis using the framework presented would help to define a new national policy to manage nuclear waste.
Article
The accelerator requirements for an economic spallation breeder system are reviewed. An intermediate energy, high mean current proton linear accelerator is the preferred choice. Present designs of drift tube and coupled cavity structures can be adapted to 100% duty factor operation. From recent work on meson factory and synchrotron injector linacs it appears likely that beam spill can be reduced to acceptable levels. For economy the emphasis is on the efficient production of radiofrequency power, most of which must be delivered to the accelerated beam. Some trends in current development are outlined.
Article
We describe a new approach for commercial nuclear energy production without a long-term high-level waste stream and for transmutation of both fission product and higher actinide commercial nuclear waste using a thermal flux of accelerator-produced neutrons in the 1016 n/cm2s range. Continuous neutron fluxes at this intensity, which is approximately 100 times larger than is typically available in a large scale thermal reactor, appear practical, owing to recent advances in proton linear accelerator technology and to the spallation target-moderator design presented here. This large flux of thermal neutrons makes possible a waste inventory in the transmutation system which is smaller by about a factor of 100 than competing concepts. The accelerator allows the system to operate well below criticality so that the possibility for a criticality accident is eliminated. No control rods are required. The successful implementation of this new method for energy generation and waste transmutation would eliminate the need for nuclear waste storage on a geologic time scale. The production of nuclear energy from 232Th or 238U is used to illustrate the general principles of commercial nuclear energy, production without long-term high-level waste. There appears to be sufficient thorium to meet the world's energy needs for many millenia.
Article
Advanced spallation neutron sources, which produce neutrons through interactions of protons with heavy metal target materials, afford significant advantages over existing high flux reactors. First, the effective flux is much greater than that currently available with reactor sources. Bearing in mind the proven value of neutron scattering, and that it is an intensity limited technique, a ten-fold increase in neutron flux will be a major benefit to a wide range of condensed matter studies, and it will realise important experiments that are marginal at reactor sources, e.g. experiments which utilise neutron polarisation to analyse inelastic events. Moreover, the high intensity of epithermal neutrons (with energies of several electron volts) open new vistas in studies of electronic states and molecular vibrations.
Article
Reviews text whose contents include a review of the basic nuclear processes and the use of these processes in commercial-type applications; uranium processing; thorium processing; zirconium and hafnium; properties of irradiated fuel; plutonium and other actinide elements; fuel reprocessing; radioactive waste management; light element isotope separation; and uranium isotope separation. Assets include generally good coverage of material, adequate references, and good problems. Recommended as a welcome addition to the fuel cycle literature.
Article
Release rates of 15 radionuclides from waste packages expected to result from partitioning and transmutation of Light-Water Reactor (LWR) and Actinide-Burning Liquid-Metal Reactor (ALMR) spent fuel are calculated and compared to release rates from standard LWR spent fuel packages. The release rates are input to a model for radionuclide transport from the proposed geologic repository at Yucca Mountain to the water table. Discharge rates at the water table are calculated and used in a model for transport to the accessible environment, defined to be five kilometers from the repository edge. Concentrations and dose rates at the accessible environment from spent fuel and wastes from reprocessing, with partitioning and transmutation, are calculated. Partitioning and transmutation of LWR and ALMR spent fuel reduces the inventories of uranium, neptunium, plutonium, americium and curium in the high-level waste by factors of 40 to 500. However, because release rates of all of the actinides except curium are limited by solubility and are independent of package inventory, they are not reduced correspondingly. Only for curium is the repository release rate much lower for reprocessing wastes.
Article
This article describes Carlo Rubbia's plans to work on accelerator-based power plants after his retirement from CERN. The reactors are to be powered by thorium instead of uranium. The thorium is bombarded by neutrons, forming uranium-233 which will fission if hit by neutrons, releasing energy and more neutrons, which can promote further thorium breeding and U-233 fission. This chain reaction produces too few neutrons to be self-sustaining, so a particle accelerator is used to bombard heavy nuclei with proton beams, generating the extra neutrons required for the reaction. This type of reactor offers several advantages: few long-lived highly toxic radioisotopes, such as neptunium 237, are produced; little plutonium is produced, minimizing the risk of nuclear weapons proliferation; and a runaway nuclear accident is impossible, since fission reactions can be maintained only when the accelerator is working.