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The stellarator plasma device has been widely studied as one of the candidate solutions paralleling the ITER project, and its coupling with a fission blanket can bring benefits promoting the develo...

In this technical note, an innovative thorium-uranium–fueled fusion-fission hybrid reactor (FFHR) design that employs a dual-coolant system to enhance 233U breeding and is based on a three-dimensional engineering model is presented. The reactor consists of two kinds of modules: a water-cooled, thermal spectrum power generation natural uranium–fueled module and helium-cooled, fast spectrum fissile-breeding natural thorium–fueled modules, which are arranged alternately in the poloidal direction of the blanket. An interesting and important neutronic characteristic of the FFHR is found in this technical note: Energy multiplication is primarily determined by the uranium module parameters and is almost independent of the thorium module parameter. Uranium module design should first consider improving energy production. The 232Th neutron capture rate is primarily determined by the thorium module parameters. The uranium module parameter has almost no influence on the 232Th neutron capture rate in the thori...

A conventional (SB-CMBR) and a hybrid moving-bed (SB-HMBR) sequencing batch membrane bioreactor treating municipal wastewater were compared during their start-up in terms of organic matter and nutrient removal, membrane fouling characteristics and microbial community. Both systems exhibited similar COD, ammonium, total nitrogen (TN) and phosphorus removal efficiency, amounting up to 96%, 99%, 70% and 85%, respectively. Results from cycle tests revealed that the contribution of attached biomass to the overall ammonium removal in the hybrid reactor was marginal. Moreover, higher despite the similar phosphorus removal efficiency attained in both reactors, nitrate-dosing activity batch assays specifically revealed that the anoxic phosphate uptake rate (PUR) in the SB-HMBR was 1.71 times higher than in the SB-CMBR. Moreover, a higher frequency of Candidatus Accumulibacter-related polyphosphate-accumulating organisms was observed in the biofilm carriers of the hybrid reactor. These findings may explain why the overall PUR was almost 50% higher in the SB-HMBR. By operating the reactors in sequencing batch mode, adhesion of particles on the membrane surface was reduced while fouling was mitigated as compared to continuous MBR systems. Better filterability conditions with lower fouling rate were found in the SB-HMBR, important features of the hybrid reactor for reducing membrane cleaning-related energy demand.

An accelerator-driven system (ADS) combined with a subcritical molten salt reactor (MSR) is a type of hybrid reactor originally designed to use Th/U (or U/Pu ) fuel cycles. In most accelerator-driven molten salt reactor (AD-MSR) concepts, the salt material is also used as a target for inducing spallation neutrons. Although a neutron source is an important component in the design of ADS, only a few studies have addressed the effects of the neutron spallation source in the AD-MSR. Incidentally, there is no quantitative study on how much the beam power can be reduced by installing a spallation target in a sodium chloride-based fast reactor. We studied the proton and the neutron source efficiencies of an AD-MSR with chloride fuels by considering an Lead Bismuth Eutectic (LBE) spallation target. This LBE target is found to increase the proton source efficiency significantly. The required beam power for an AD-MSR can be reduced by 33 % and 16 % for NaCl-Th/233U and NaCl-U/Pu fuels, respectively, relativ...

A team at the Budker Institute of Nuclear Physics has been working for several years to develop the Gas Dynamic Trap Mirror Neutron Source (GDT-NS) for fusion materials irradiation. In 2010 they op...

In this paper, a light water cooled fusion-fission hybrid reactor blanket fueled with thorium and uranium is presented. The major objective is to study the feasibility of this new concept with mult...

The straight field line mirror (SFLM) hybrid reactor studies aim to identify a concept where the safety of fission power production could be enhanced. A fusion neutron source could become a mean to achieve this. The SFLM studies address critical issues such as reactor safety, natural circulation of coolants, steady state operation for a year or more and means to avoid too strong material loads by a proper geometrical arrangement of the reactor components. A key result is that power production may be possible with a fusion Q factor as low as 0.15. This possibility arises from the high power amplification by fission, which within reactor safety margins may exceed a factor of 100. The requirements on electron temperature are dramatically lower for a fusion hybrid compared to a stand-alone fusion reactor. This and several other factors are important for our choice to select a mirror machine for the fusion hybrid reactor studies.

A stellarator-mirror fusion-fission hybrid has recently been proposed. Neutral beam injection (NBI) is here studied numerically for this hybrid using a two-dimensional kinetic code, KNBIM The code accounts for Coulomb collisions between the hot ions and the background plasma. The geometry of the confining magnetic field is arbitrary for the code and is accounted for via a numerical bounce averaging procedure. Along with the kinetic calculations the neutron production intensity is computed. The calculated hot ion distribution function from NBI is used in power balance estimates for the whole system. The requirement that the fast neutrals should be efficiently captured in the plasma is imposed to restrict the range of plasma parameters. The results of the power balance calculations are close to results obtained previously with a bi-Maxwellian ion distribution function. The calculated parameters for a power producing stellarator mirror device are within modern top technical capabilities. The parameters of plasma and NBI characteristics seem also attainable. The calculated fusion Q is within a range with potential for energy production in a hybrid reactor.

In this study, the anaerobic hybrid reactor (AHR) was used for the treatment of synthetic wastewater containing tetrachloroethylene (PCE) by systematic increment in the influent PCE and chemical oxygen demand (COD) concentrations. According to the acclimatization study, 99.95 ± 0.07% of PCE and 98.26 ± 0.46% of COD removals were obtained at an influent PCE and COD concentrations of 50mg/l and 2,000 mg/l, respectively. The maximum yield coefficient (Ym ) was found to be 0.055 mg biomass/mg COD, while the maximum specific substrate as COD (qm S) and co-substrate as PCE (qm CS) utilization rates were found to be 570 mg COD/g volatile suspended solids (VSS)/d and 15.83 mg PCE/g VSS/d, respectively, during the bio-kinetics study. The optimum hydraulic retention time for the maximum PCE removal was observed to be 18 h. The results of this study broadly indicated that the AHR has the high potentiality for the treatment of wastewater containing high concentration of PCE.

A fusion-fission hybrid reactor whose fusion component is the gasdynamic mirror (GDM) is proposed for power production that could meet the world’s energy needs of the next several decades. The choi...

An experimental technique based on an accelerator-beam trip or restart operation is proposed to determine the subcritical reactivity of an accelerator-driven system (ADS). Applying the least-squares inverse kinetics method to the data analysis, the subcriticality can be inferred from time-sequence neutron count data after these operations. A series ofbeam trip and restart experiments with 14 MeV neutrons were carried out in a thermal ADS of Kyoto University Critical Assembly (KUCA), to demonstrate the applicability of the proposed technique. The subcriticalities evaluated using neutroncounters far from the DT target were consistent with those obtained in a previous pulsed neutron experiment. However, a counter placed close to the target significantly overestimated the subcriticality. The present technique is expected to be available for subcriritcality measurement at startup and shutdown of various ADSs.

Anaerobic digestion with ozonation is a promising process to enhance the digestion efficiency and reduce the sludge quantity for disposal. In this study, new process schemes by incorporating thermophilic digestion were studied for further improvements. Pilot tests were performed with three schemes having mesophilic, thermophilic or mesophilic-thermophilic hybrid reactors. In the process scheme with thermophilic digestion, the degradation ratio of VSS components was observed to improve by 5.5% over mesophilic digestion. The amount of ozone consumption could also be reduced by 18%. However, biogas conversion ratio was not improved due to considerable non-degradable organic fraction remaining in soluble form. In batch tests, this soluble fraction was found to readily degrade by mesophilic microorganism. Based on this observation, a mesophilic-thermophilic hybrid flow scheme was developed. In this flow scheme, thermophilic microbes rapidly degraded ozonated sludge and remaining soluble organic components were...

Anaerobic biofilm reactors have limitations in treating wastewaters with low organic substrate concentrations (COD value below 1000 mg/L) because the substrate cannot reach the microorganisms present in the interior part of the biogranules. Hence, the performance of these reactors is mainly influenced by the size of the biogranules present within the reactor. An anaerobic hybrid reactor with a tapered configuration has been developed where the self-immobilized biogranules are kept under completely fluidized condition. The tapered configuration can retain smaller sized biogranules more effectively than a cylindrical configuration for the same hydraulic loading rate. A synthetic effluent containing glucose as the sole carbon source was used to study the performance of this reactor. The reactor could handle an organic loading rate up to 19.1 kgCOD/(m3 x d) with a hydraulic retention time (HRT) of 0.63 h, removing around 90% of inlet COD. Even though the strength of the wastewater is low, the resultant organic loading rate is also high because of the high hydraulic loading rate (low HRT). The specific substrate utilization rate study showed that the concentration of methanogenic bacteria within the biogranules increased along the reactor height, whereas the concentration of acidogens decreased. The morphology and hydrodynamic characteristics of the biogranules obtained from the reactor at different heights were also studied. The biogranules obtained from the upper port of the reactor had a lower diameter, lower terminal settling velocity and more cavities than those from the lower port. Biogranules up to the size of 5.2 mm were observed.

A comparatively small mirror fusion hybrid device may be developed for industrial transmutation and energy production from spent nuclear waste. This opportunity ensues from the large fission to fusion energy multiplication ratio, Q(r) =P-fis/P-fus

The transient response of the subcritical advanced burner reactor (SABR) subcritical, sodium-cooled, transuranic fueled, fast transmutation reactor design concept, which ensued from several accident initiation events, has been simulated. The results establish such things as the number of primary loop pumps that could fail or the magnitude of flow reduction in the intermediate loop heat removal capability due to either pump failure or intermediate heat exchange failure that could be tolerated without core damage, the consequences of loss of electrical power, and the consequences of control rod ejection or neutron source excursions. Suggestions are offered for design changes to improve the already good safety characteristics of the design concept.

To confirm the reliability of calculated reactor physics parameters for the nuclear transmutation systems, the uncertainty deduced from the covariance data prepared in JENDL-3.3 is compared with the differences in the reactor physics parameters in the Monte-Carlo calculation using different nuclear data libraries, ENDF/B-VII.0 and JEFF-3.1.1. The Accelerator-Driven System (ADS) and the Minor Actinide (MA)-loaded Fast Reactor (FR) are selected as the representative transmutation systems. The criticality and void reactivity of these systems are discussed. The results show that the uncertainties deduced from the JENDL-3.3 covariance data are smaller than the differences in the reactor physics parameters among the nuclear data libraries. The cause of this discrepancy is that the covariance data of main nuclides and reactions in JENDL-3.3 are smaller than the relative differences in the cross sections among the nuclear data libraries. It is required to verify the uncertainty of the reactor physics parameters by integral experiments and to discuss the uncertainty utilization for the nuclear design accuracy.

Neutron spectrum experiments on the Accelerator-Driven System (ADS) are conducted by combining a critical assembly of a solid-moderated and solid-reflected core with a Cockcroft-Walton-type accelerator. Neutrons (14 MeV) generated from the accelerator are injected into a subcritical system and the reaction rates are measured by the foil activation method to obtain neutronic spectrum data. The numerical calculations are executed by MCNP-4C3 with JENDL-3.3 and JENDL/D-99 libraries to evaluate the reaction rates of activation foils set in the core center and at the target. In the present study, the measured and calculated (JENDL/D-99) reaction rates in all the activation foils at the target reveal around a difference of 10% in C/E values, while a bigger discrepancy between the results of the experiments and the calculations is observed in the center of the core. On the other hand, a special mention is made of the fact that the reaction rate analyses for the neutron spectrum in the subcritical systems demonst...

In this study, progresses and recent trends in biogas processing are reviewed. Biogas is generated from biomass by digestion under anaerobic conditions in the presence of microorganisms. Anaerobic digestion occurs in the absence of air and is typically carried out for a few weeks. The anaerobic digestion process occurs in the following four basic steps: (1) hydrolysis, (2) acidogenesis, (3) acetogenesis, and (4) methanogenesis. In the last two decades, anaerobic digestion technology was significantly improved by the development of the sludge bed digesters, granular sludge-based bioreactors such as the upflow anaerobic sludge blanket, and the anaerobic hybrid reactor. Biogas plants at farm level are good candidates for treating organic residues of both municipalities and the agro-industrial sector in a cost-effective way and in providing territorially diffused electric and thermal power.

This work presents the development of an analytical approximation solution for a space-time-dependent neutron transport problem in a one-dimensional system consisting of a homogenized medium with a central external source with Green 's functions. The delayed neutron production is implemented with the multiple-scale expansion method. Qualitative results for a given system are analyzed and an example of the use for the analysis of accelerator-driven systems is given.

In preparation for connecting a Fixed Field Alternating Gradient (FFAG) accelerator atthe Kyoto University Critical Assembly (KUCA), static and kinetic experimental and numerical analyses of Accelerator-Driven System (ADS) are envisaged. Improvement of source multiplication by the implementation of a neutron guide is expected to affect the characteristics of the ADS core. The effects on reactivity and neutron flux distribution are investigated by measurements of the subcriticality and the reaction rate distributions of indium wire, respectively, using the KUCA core and the current 14MeV pulsed neutron generator. A comparison of the results of static measurements with those of calculations provides an estimation of MCNP-4C3 precision with JENDL-3.3 and ENDF/B-VI.2 for the basic research on ADS with 14 MeV neutrons at KUCA. The neutron guide has proved to be experimentally effective in improving external source when it is extended into the fuel region. Since the reactivity range of the actual ADS operation ...

The three most important americium isotopes, 241Am, 242mAm, and 243Am originate in the nuclear fuel of pressurized water reactors (PWRs), fast reactors (FRs), or accelerator-driven systems (ADSs) i...

Three-dimensional analysis has been made using the MCNP Monte Carlo code and ENDF/B-VI nuclear data. The nuclear characteristics of a fusion-fission hybrid reactor such as tritium breeding ratio, energy multiplication factor, fissile fuel breeding, first wall radiation damage, and heat deposition have been investigated in a liquid first wall, blanket, and shield for the various mixture compositions of molten salt and heavy metals for blanket layer thicknesses of 20, 30, 40, and 50 cm. The neutron flux load at the first wall is assumed to be 10 MW/ m 2 . The flowing molten salt wall is composed of flibe (Li 2 BeF 4 ) as the main constituent with increased mole fractions of heavy metals, 2 to 10% ThF 4 and UF 4 . In terms of all parameters, the mixtures with UF 4 show better performance than the mixtures with ThF 4 . The atomic displacement and the helium, tritium production rates remain well below the presumable limits for all mixture compositions of molten salt and heavy metals and thicknesses of the blanket.

The production of nuclear energy in France has been associated, since its inception, with the optimization of radioactive waste management, including the partitioning and the recycling of recoverable energetic materials. From the start, the Commissariat a l'Energie Atomique (CEA) has devoted considerable effort to the management of the back end of the cycle in order to extract the re-usable materials, uranium and plutonium, and to condition the resulting waste with the vitrification process. At the end of the December 1991 Waste Management Act, it is considered that partitioning techniques, which have been validated on real solutions with aqueous process, have been brought to a point where there is reasonable assurance that industrial deployment can be successful. For transmutation, CEA has conducted programs proving at lab scale the feasibility of the elimination of minor actinides and scenario studies have also allowed assessing the efficiency of transmutation in terms of the quantitative reduction of t...

Research and development of minor actinide-containing fuels and targets, i.e., (Pu,Am)O2–MgO, (Pu,Np)O2–MgO, (U,Pu,Np)O2, (U,Pu,Np)N and (Pu,Np,Zr)N, for use in a future integrated closed cycle system that includes fast reactor and accelerator driven sub-critical system is underway. The present statuses of fabrication test and property measurements are given. Design concept of the oxide target is described in detail together with a screening of the support material. A new apparatus for the measurement of mechanical properties at the elevated temperature is installed for use in evaluating the fuel-cladding mechanical interaction. Development histories with future prospects of two types of Np-containing fuels for the fast reactor are mentioned. Preliminary test results for a new nitride target for the accelerator driven sub-critical system are given. Finally, an irradiation test plan in the experimental fast reactor JOYO is briefly described.

The Research Reactor Institute of Kyoto University started the KART (Kumatori Accelerator-driven Reactor Test facility) project in fiscal year 2002 under the Contract with the Ministry of Education, Culture, Sports, Science and Technology of Japan. The purpose of this research project is to demonstrate the basic feasibility of accelerator-driven system (ADS), studying the effect of incident neutron energy on the effective multiplication factor in a subcritical nuclear fuel system. For this purpose, a variable-energy FFAG (Fixed Field Alternating Gradient) accelerator complex is constructed and coupled with the Kyoto University Critical Assembly (KUCA). This paper presents the present status of the project and some of the results from the task performed up to Fiscal Year 2005.

A consistent analytical comparison has been made of the transient behavior of critical and subcritical fast-spectrum reactor systems, the basic core design assumed in each case being that of the 80-MW(thermal) mixed-oxide-fueled, Pb-Bi-cooled, experimental accelerator driven system (XADS). The transient calculations were performed using the FAST code system developed at the Paul Scherrer Institute. The present study demonstrates a high level of self-protection of both the critical and subcritical systems over a wide range of postulated events, including transient overpower due to reactivity insertion, loss of flow, station blackout, loss of coolant, and core overcooling accidents. The relative advantages and shortcomings of the two system types, from the viewpoint of transient behavior, are discussed on the basis of the corresponding simulation results obtained.

The FUTURE and CONFIRM projects of the 5th European Framework Program address the issues of the design and fabrication of oxide and nitride fuels, respectively, for the transmutation in an accelerator-driven system (ADS). They started in December 2001 and September 2000, respectively. Advantages and drawbacks of transuranic oxides and nitrides in terms of performance and fabricability have been analyzed. Recommendations on the fuel design will be given and used for the next step of the 6th European Framework Program related to the design and the feasibility assessment of an industrial ADS prototype dedicated to transmutation.

The ability of point kinetics to describe dynamic processes in accelerator-driven systems (ADSs) is investigated. Full three-dimensional energy-space-time-dependent calculations, coupled with therm ...

A lead-bismuth-cooled fast reactor concept targeted for a balanced mission of actinide burning and low-cost electricity production is proposed and its performance analyzed. The design explores the potential benefits of thorium-based fuel in actinide-burning cores, in particular in terms of the reduction of the large reactivity swing and enhancement of the small Doppler coefficient typical of fertile-free actinide burners. Reduced electricity production cost is pursued through a longer cycle length than that used for fertile-free burners and thus a higher capacity factor. It is shown that the concept can achieve a high transuranics destruction rate, which is only 20% lower than that of an accelerator-driven system with fertile-free fuel. The small negative fuel temperature reactivity coefficient, small positive coolant temperature reactivity coefficient, and negative core radial expansion coefficient provide self-regulating characteristics so that the reactor is capable of inherent shutdown during major transients without scram, as in the Integral Fast Reactor. This is confirmed by thermal-hydraulic analysis of several transients without scram, including primary coolant pump trip, station blackout, and reactivity step insertion, which showed that the reactor was able to meet all identified thermal limits. However, the benefits of high actinide consumption and small reactivity swing can be attained more » only if the uranium from the discharged fuel is separated and not recycled. This additional uranium separation step and thorium reprocessing significantly increase the fuel cycle costs. Because the higher fuel cycle cost has a larger impact on the overall cost of electricity than the savings from the higher capacity factor afforded through use of thorium, this concept appears less promising than the fertile-free actinide burners. « less

We outline the strategy and constraints adopted for the design of medium-power lead-alloy–cooled actinide-burning reactors that strive for a lower cost than accelerator-driven systems and for robus...

The TRiga Accelerator-Driven Experiment (TRADE), to be performed in the TRIGA reactor of the ENEA-Casaccia Centre in Italy, consists of the coupling of an external proton accelerator to a target to be installed in the central channel of the reactor scrammed to subcriticality. This pilot experiment, aimed at a global demonstration of the accelerator-driven system concept, is based on an original idea of C. Rubbia. The present paper reports the results of some neutronic analyses focused on the feasibility of TRADE. Results show that all relevant experiments (at different power levels in a wide range of subcriticalities) can be carried out with relatively limited modifications to the present TRIGA reactor.

Experiments were performed on a laboratory model of a hybrid bioreactor consisting of an aeration tank to which support media were added to simulate both suspended and attached growth reactors, a secondary clarifier and a recycling system. The system was operated for a period of two months, using synthetic wastewater for the substrate medium. Support media were added to the reactor in stages of six nets each stage, so as to evaluate the impact of the addition of the support media on the efficiency of treatment. Relevant parameters were measured regularly. The study demonstrated the positive effects the system had on BOD 5 removal and the settling efficiency in the secondary clarifier.

Hybrid reactor simulation (HRS) of boiling water reactor (BWR) instabilities, including in-phase and out-of-phase (OOP) oscillations, has been implemented on The Pennsylvania State University TRIGA reactor. The TRIGA reactor's power response is used to simulate reactor neutron dynamics for in-phase oscillation or the fundamental mode of the reactor modal kinetics for OOP oscillations. The reactor power signal drives a real-time boiling channel simulation, and the calculated reactivity feedback is in turn fed into the TRIGA reactor via an experimental changeable reactivity device. The thermal-hydraulic dynamics, together with first harmonic mode power dynamics, is digitally simulated in the real-time environment. The real-time digital simulation of boiling channel thermal hydraulics is performed by solving constitutive equations for different regions in the channel and is realized by a high-performance personal computer. The nonlinearity of the thermal-hydraulic model ensures the capability to simulate the oscillation phenomena, limit cycle and OOP oscillation, in BWR nuclear power plants. By adjusting reactivity feedback gains for both modes, various oscillation combinations can be realized in the experiment. The dynamics of axially lumped power distribution over the core is displayed in three-dimensional graphs. The HRS reactor power response mimics the BWR core-wide power stability phenomena. In the OOP oscillationmore » HRS, the combination of reactor response and the simulated first harmonic power using shaping functions mimics BWR regional power oscillations. With this HRS testbed, a monitoring and/or control system designed for BWR power oscillations can be experimentally tested and verified.« less

In an inertial fusion energy (IFE) reactor of 1000-MW(electric) fusion power, 95% flibe and 5% fuel with DR{sub c} thickness instead of 100% flibe are used. At startup, the tritium breeding ratio and M-blanket energy multiplication ratio are 1.05 and 1.26 for UF{sub 4} and DR{sub c} [approximately equal to] 60 cm, respectively. These values increase during an operation period of 30 yr. In 11 yr, M increases from 1.26 to 2 [2000 MW(electric)]. After operation of 11 yr, the energy production is stabilized by means of separation of produced plutonium. After 30 yr, displacement per atom (dpa) and helium production in the first wall are calculated as 92 dpa and 590 ppm, respectively. In addition, the cost of electricity values of the HYLIFE-II and the improved HYLIFE-II of 2000 MW(electric) drop from 4.5 and 3.2 cent/kW.h to 4.18 and 3.00 cent/kW.h, respectively. On the other hand, the IFE reactor has the fissile fuel breeding potential of 70 tonnes. The fissile fuel of 45 tonnes corresponding to [approximately equal to]2350 kg/yr would be sufficient to provide makeup fuel for [approximately equal to]10 light water reactors after 11 yr. After the shutdown process, 25 tonnes of fissile fuel with fuel enrichmentmore » of 23% would be left over.« less

So-called dedicated fuels will be utilized to obtain maximum transmutation and incineration rates of minor actinides (MAs) in accelerator-driven systems (ADSs). These fuels are characterized by a high-MA content and the lack of the classical fertile materials such as {sup 238}U or {sup 232}Th. Dedicated fuels still have to be developed; however, programs are under way for their fabrication, irradiation, and testing. In Europe, mainly the oxide route is investigated and developed. A dedicated core will contain multiple 'critical' fuel masses, resulting in a certain recriticality potential under core degradation conditions. The use of dedicated fuels may also lead to strong deterioration of the safety parameters of the reactor core, such as, e.g., the void worth, Doppler or the kinetics quantities, neutron generation time, and {beta}{sub eff}. Critical reactors with this kind of fuel might encounter safety problems, especially under severe accident conditions. For ADSs, it is assumed that because of the subcriticality of the system, the poor safety features of such fuels could be coped with. Analyses reveal some safety problems for ADSs with dedicated fuels. Additional inherent and passive safety measures are proposed to achieve the required safety level. A safety strategy along the lines of a defensemore » approach is presented where these measures can be integrated. The ultimate goal of these measures is to eliminate any mechanistic severe accident scenario and the potential for energetics.« less

Since thorium is an abundant fertile material, there is hope for the thorium-cycle fuels for an accelerator driven subcritical system (ADS). The ADS utilizes neutrons, which are generated by high-e...

In recent years an increasing interest is observed with respect to subcritical, accelerator driven systems (ADS), for their possible role in future nuclear energy scenarios, as actinide (Pu and MA) incinerators, and/or as claimed energy plants with potential enhanced safety characteristics. Important research programs are devoted to the various related fields of research. Extensive studies on the ADS behavior under incidental conditions are in particular made, for verifying their claimed advantage, under the safety point of view, with respect to the corresponding critical reactors. Related medium and long range scenarios are being considered to cope with a number of concerns associated with safety (power excursions, residual heat risk), as well as with fuel flow (criticality accidents, fuel diversion, radiological risk, proliferation). In the present work we shall comment on some issues relevant to these new reactor concepts, with the intent of giving a general view of the present state-of-the-art in the ...

A conceptual blanket design for 129I transmutation is proposed for an accelerator-driven system (ADS) that is designed to transmute minor actinides (MAs). In this ADS, 250 kg/yr of MA and 56 kg/yr ...

A general-purpose transport and burnup code system for precise analysis of subcritical reactors like a fusion-fission (FF) hybrid reactor was developed and used for analyzing their performance. The FF hybrid reactor is a subcritical system, which has a concept of fusion reactor with a blanket region containing nuclear fuel and has been under discussion by author’s group for years because the present burnup calculation system mainly consists of a general-purpose Monte Carlo code MCNP-4B, a point burnup code ORIGEN2. JENDL-3.3 pointwise cross section library and JENDL Activation Cross Section File 96 were used as base cross section libraries to make group constant for burnup calculation.A new method has been proposed to make group constant for the burnup calculation as accurate as possible directly using output data of the neutron transport calculation by MCNP and evaluated nuclear data libraries. This method is strict and a general procedure to make one group cross sections in Monte Carlo calculations, whi...

Effects on the neutronic performance of the hybrid blanket rejuvenating light water reactor and CANDU spent fuels of moderators (Be, C, and D2O) inserted between the fusion chamber and the fissile zone of deuterium-deuterium and deuterium-tritium-driven hybrid reactor were investigated to obtain the best rejuvenation performance and more energy production. The calculations were carried out for different thicknesses of the moderator zone (DR). In addition, to eliminate focal heating, the analysis was also repeated for reduced radius of the spent fuel rods in the first and the second fuel rows of the fissile zone.

A contact are and adiabatic expansion hybrid reactor has been utilized to provide a controlled cooling process of gaseous carbon species capable of attaining very high velocities. Both vaporization and annealing temperatures and annealing time were found to be impartant for the formation of fullerenes. Immediate rapid quenching of gaseous carbon resulted in the reduction of fullerene yields. However, rapid quenching was demonstrated to improve the fullerene yield by preserving the as-grown fullerenes in the high temperature annealing process.

Plasma size and other basic performance parameters for 1000-MW (electric) power production are calculated with the blanket energy multiplication factor, the M value, as a parameter. The calculational model is based on the International Thermonuclear Experimental Reactor (ITER) physics design guidelines and includes overall plant power flow. Plasma size decreases as the M value increases. However, the improvement in the plasma compactness and other basic performance parameters, such as the total plant power efficiency, becomes saturated above the M = 5 to 7 range. Thus, a value in the M = 5 to 7 range is a reasonable choice for 1000-MW (electric) hybrids. Typical plasma parameters for 1000-MW (electric) hybrids with a value of M = 7 are a major radius of R = 5.2 m, minor radius of a = 1.7 m, plasma current of Ip = 15 MA, and toroidal field on the axis of B0 = 5 T. The concept of a thermal fission blanket that uses light water as a coolant is selected as an attractive candidate for electricity-produ...

Modification of the gas‐solids separator of expanded granular sludge bed (EGSB) reactors is necessary to prevent excessive sludge wash‐out during anaerobic treatment of lipid emulsions. This paper describes two modifications: a hybrid reactor with a layer of floating carrier material (reticulated polyurethane foam) above the expanded sludge bed and a novel EGSB reactor equipped with a sieve‐drum separator (EGSB‐SDS). Replacement of the conventional sludge separator by a layer of floating polyurethane foam does not prevent sludge wash‐out. Therefore, the hybrid reactor is unreliable in treatment of emulsified lipids. An EGSB‐SDS reactor allows stable anaerobic digestion of emulsified lipids. An increase of the amount of granular sludge in the reactor can be achieved, provided that sludge granules with a sufficiently large diameter are used for inoculation. Especially if easily degradable organic contaminants are present in the waste water besides the lipids, maintaining a sufficiently large invent...

Many industrially important dehydrogenation reactions are operated under conditions where the equilibrium conversion is limited by the production of hydrogen. Ceramic membrane reactors offer the potential for increased conversion at existing operating temperatures or reduced operating temperature for the same conversion level by removal of product hydrogen. This paper reports the results of recent efforts to develop catalytic membrane reactors for the dehydrogenation of ethylbenzene to styrene. The focus of this study was to compare the performance of a hybrid reactor, consisting of a packed bed followed by a membrane reactor, with that of a traditional two-stage packed-bed reactor under industrially relevant conditions. The hybrid configuration mimics the simplest implementation of a ceramic membrane reactor, simulating the use of the membrane reactor as an add on stage to the existing reactor train. A benchscale system has been developed that is capable of experimentally simulating the industri...

A fusion--fission power system is considered in which fissile-producing hybrid (or fusion--fission) reactors supply the makeup fuel needs for fissile-consuming, or converter, reactors. As a result of the diverse nature of the hybrid reactor, a number of general performance parameters are proposed that will permit comparison of various hybrid reactor configurations. In addition, the relationships developed are used to show that scientific feasibility or breakeven for the hybrid reactor is near at hand in the fusion program and that attractive commercial reactors can be based on near-term plasma physics.

An overview is presented for recent design trends and developments in fusion-fission hybrid reactor concepts. Emphasis is on recent progress and developments but a brief review of the evolution of the hybrid concept since 1950 is also presented. Required fusion performance and technology development issues for the fusion-fission hybrid are explored with the tandem mirror as the primary example of a fusion driver. The results show that fusion breeders, especially those with suppressed-fission blankets, have the potential to produce unprecedented quantities of fissile fuel. The resulting high light water reactor support ratio relaxes both the fusion performance required and the economic constraints for commercial feasibility. 75 refs.

The AYMAN research project has been initiated to formulate the main structure of a prototypical experimental fusion and fusion-fission (hybrid) reactor blanket in cylindrical geometry. This geometry is consistent with most of the current fusion and hybrid reactor design concepts in respect to neutronic considerations.In this project, the fusion chamber is simulated by a cavity with a diameter of ∼1.6 m inside a cylindrical blanket. Fusion neutrons of 14 MeV are produced by a movable target along the axis of the cylinder. The movable neutron source allows simulation of a line source for integral experiments, which is a result of the linear nature of the Boltzmann transport equation.The calculations have shown that a blanket with a 13-cm-thick natural UO2 fuel zone and a 17-cm-thick Li2O zone has a self-sustaining tritium breeding for the fusion driver. By an appropriate dispersion of the Li2O zone inside the graphite reflector, it became possible to decrease the neutron leakage out of the reflector...

A number of approaches to the design of fusion-fission hybrid reactor blankets having a flat power distribution and constant energy multiplication are described. These include the use of reflectors, lithium control, spectral shift control, and inherent control. These approaches are illustrated for natural-uraniumfueled, light-water-moderated blankets.