Fusion Hybrid Reactor Research Articles

Multi-group analysis of Minor Actinides transmutation in a Fusion Hybrid Reactor

New nuclear technologies are currently being study to face High Level Waste treatment and disposal issues. Generally, GEN-IV fission Fast Reactors (FR) are considered the waste-burners of the future. In fact, a fast flux turns out to be the best choice for actinides irradiation in critical reactors because of favorable cross section conditions. Differently, Fusion Fission Hybrid Reactors (FFHR) are futuristic devices based on the combination of fusion and fission systems and could represent an alternative to FRs. In such systems, the choice spectrum of the neutron flux that irradiates HLW may be non-obvious due to some operational constraints which have to be considered. To design and optimize these systems as waste-burners, one should fully understand the transmutation dynamics occurring into the fission region. A multi-energy-group analysis by FISPACT-II code has been set to analyze the conversion processes in scenarios characterized by different neutron energy spectra and fluences. The results of this study show that, despite fast fluxes are characterized by better behaviors in terms of radiotoxicity treatment, the difficulties of reaching high reaction yields may require solutions involving moderators or broadened neutron fluxes to increase the reactions probabilities and, consequently, actinides mass conversion yield.

Nuclear waste transmutation and tritium production in a fusion-driven hybrid reactor based on different reflectors

Abstract A comprehensive comparison neutronics calculation has been performed to investigate the effect of different reflectors on the tritium production and transmutation of minor actinides in a fusion hybrid reactor. Fusion-Driven Subcritical Spent Fuel Burner hybrid reactor (FDS-SFB), has been chosen as the computational model. All the designs and calculations have been carried out by using SuperMC Monte-Carlo code with ENDF/B-VII neutron cross-section library. Beryllium (Be), beryllium oxide (BeO), HT-9 stainless steel, tungsten carbide (WC), magnesium oxide (MgO), silicon carbide (SiC), and titanium carbide (TiC) have been selected as the candidate reflectors. Other neutronic parameters, such as the neutron flux spectrum as well as the effective multiplication factor (keff), have been calculated for each of the reflectors to understand the behavior of each reflector material. In the case of tritium production, as expected, Be and BeO had the best performance and if a non-beryllium reflector was considered, MgO could be the best. In the case of transmutation of TRUs, for 241Am, 243Am, and 242Pu, BeO had the best results. For 244Cm and 237Np, TiC and MgO were the best choices respectively. For the total transmutation, BeO, MgO, and WC had the best capability to transmute TRUs among the other reflectors. Considering both parameters, i.e., TRUs transmutation and Tritium production, BeO (among beryllium-reflectors) and MgO (among non-beryllium reflectors) could be an appropriate choice to fusion hybrid designs.

Numerical simulation of flow instability in a circular tube under pulse heating condition

Energy systems based on inertial confinement fusion or fusion-fission hybrid reactor generate energy in the form of pulse heating, which may lead to new flow instability phenomenon in the cooling system. In order to make thermal hydraulic design of pulse heating energy system safe and reliable, it is necessary to deeply understand the oscillation characteristics of flow and heat transfer under the pulse heating condition. As for the first stage of this complicated research, the numerical simulation of coolant flow in a circular tube under pulse heating condition is executed in this paper. The oscillation characteristics of flow and heat transfer under different pulse heating conditions are discussed in detail, and the effect of heating power, pulse heating period and duty ratio are studied. Four flow development stages (stage A – stage D) are identified, and three kind of flow oscillation phenomenon are found according to the numerical results with increasing the pulse heating power. The analysis shows that oscillation is mainly caused by pulse heating itself or the combination of pulse heating and density wave oscillation (DWO). Increasing the pulse heating period is beneficial to decrease flow oscillation, and decreasing the duty ratio, the flow oscillation is more obvious. The flow development stage maps are also given in the plane of average power and inlet subcooled temperature. With the increase of period, the stage D appears more easily at lower average power. When the duty ratio decreases, the region of stage C in instability map becomes larger.

Hybrid Reactor Studies Based on the Straight Field Line Mirror

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 Fusion Hybrid Reactor Based on the Gasdynamic Mirror (GDM)

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 choice of the GDM is based on the fact that it is linear, axisymmetric and can operate in steady state. Since the primary role of the fusion component is to supply neutrons to the blanket, it can operate at or near “breakeven” condition, a much less stringent condition than that required for a pure fusion reactor. A large aspect ratio GDM is desirable because of MHD stability considerations, and if we choose such a geometry then a cylindrically symmetric plasma with a surrounding blanket can be treated as semi-infinite cylinders, allowing for the reactor performance to be determined by two, one-dimensional equations: one describing the time evolution of the fissile material density bred in the fertile blanket, and another describing the diffusion of fast neutrons in that region. Our choice for the blanket material is thorium-232 in order to take advantage of the thorium fuel cycle that leads to the breeding of uranium-233. Such a fuel cycle is known to be resistant to proliferation and clandestine operations. We choose to operate the GDM at 0.10 of breakeven, using deuterium-tritium (DT) plasma at a density of 1016 cm-3, and a temperature of 10keV. We find that for a reasonable design, such a reactor can generate tens of megawatts of thermal power per cm “safely” because it is “subcritical”, and “securely” because of our choice of the fuel cycle. A systems analysis reveals that about 2% of the net electric power is needed to sustain the fusion component. Moreover, we find that it takes approximately 4 months to reach steady state due to the several steps involved in the breeding cycle.

A possibility of miniaturized fusion and fission hybrid reaction core with positive fusion yield

A novel fission–fusion hybrid reactor was proposed, comprising saturating of a fissile actinide core with a mix of deuterium–tritium hydrogen isotopes (U–D–T target), similarly to Hyperion design. Movement of massive, highly charged and short-range fissile fragments was assumed to produce transfer of energy to deuterons at the distances below collision impact parameter for electrons, when the latter are already deflected. The overall bulk of energy transfer was still assumed to be directed to electrons, being argued to experience secondary interactions in dense metallic matrix at a short distance (∼3 × 10 −13 m) from the projectile. The resulting energy dissipation occurs as a continuous shockwave front (as opposed to discrete transfer in environments of lesser densities) producing compression ahead of the projectile and impacting local values of density. The continuity at short distances from the projectile justified hydrodynamic analogy and application of Taylor–Sedov's shockwave theory. At higher local densities in a bow-wave, the probability of high-energy deuteron acceleration was shown to increase in proportion to compression. The transient non-equilibrium equivalents of pressure and temperature may support fusion in the region with volume V over hot zone life-time τ. Both parameters were compared for the U–D–T and benchmark system (accelerator driven deuteron implantation in a non-actinide hydride target) in a dimensionless and hypothesis-free form, canceling the complexities of the mechanism. Based on the dimensionless theoretical prediction, ∼1–2 fusion 14 MeV neutrons per fission are expected to be produced, accompanied by 1–2 photoneutrons and leading to a significantly decreased critical mass. If confirmed experimentally, the proposed system could produce ∼10–20% of its energy output as controlled fusion, be of compact and economical design, environmentally friendly, lead to significant miniaturization of reactor core compatible with high rate of heat exchange. Novel technological applications in robotics, propulsion, sea bed exploration and as a robust energy source were proposed.

Suitability of Small Scale Linear Systems for a Fission–Fusion Reactor, Breeder, and Waste Transmutation

To date the magnetic fusion effort has been almost entirely devoted to only one application, that being a multi gigawatt central station electric plant. Given the already well established fission based industry, the likelihood that fusion will have any impact on curbing the current carbon-based energy demand in the 21st century is slim. This paper advocates that the first and primary use of fusion neutrons should be as the driver for a sub-critical fission nuclear energy system—a fission–fusion hybrid reactor. This system can also be utilized to transmute long-lived radioactive wastes, and breed fissile nuclear fuel for several additional fission reactors. A small-scale fusion system based on a reciprocating fusion cycle employing the magneto-kinetic compression of the Field Reversed Configuration (FRC) is particularly well suited for this application. The characteristics of this fusion neutron driver and the potential for transmutation of long-lived nuclear wastes and breeding of fissile nuclear fuel in a blanket are presented.

Radiation damage in muon-catalyzed hybrid reactors / Strahlenschäden in Hybridreaktoren mit myonenkatalysierter Fusion.

Radiation damage of the structural components of a muon-catalyzed fusion hybrid reactor is considered. These damage effects are examined for a range of materials, and a ranking of material composition is established

An Analysis of Tritium and Fissile Fuel Exchange in Fusion-Fission Systems

A model is developed to describe the tritium and fissile fuel flow in a fusion-fission system which consists of a fusion (hybrid) reactor, tritium production (fission) reactors, and (fission) power reactors. The fusion reactor provides all of the fissile fuel for the tritium production and power reactors. Tritium production reactors assure that the system is self sufficient in tritium even if the fusion reactor is not self sufficient. Studies were performed to determine the changes in the cost of electricity from the system as the tritium breeding responsibility varies between the fusion reactor and the tritium production reactors. Allowance for system growth was accomplished with the use of a compound doubling time parameter. Results indicate that the cost of electricity from certain fusion-fission systems may be comparable to that from other advanced systems expected in the same era.

The tokamak hybrid reactor

At a time when the potential benefits of various energy options are being seriously evaluated in many countries throughout the world, it is both timely and important to evaluate the practical application of fusion reactors for their economical production of nuclear fissile fuels from fertile fuels. The fusion hybrid reactor represents a concept that could assure the availability of adequate fuel supplies for a proven nuclear technology and have the potential of being an electrical energy source as opposed to an energy consumer as are the present fuel enrichment processes. Westinghouse Fusion Power Systems Department, under Contract No. EG-77-C-02-4544 with the Department of Energy, Office of Fusion Energy, has developed a preliminary conceptual design for an early twenty-first century fusion hybrid reactor called the Commercial Tokamak Hybrid Reactor (CTHR) [1]. This design was developed as a first generation commercial plant producing fissile fuel to support a significant number of ‘client’ Light Water Reactor (LWR) Plants. To the depth this study has been performed, no insurmountable technical problems have been identified. The study has provided a basis for reasonable cost estimates of the hybrid plants as well as the hybrid/LWR system busbar electricity costs. This energy system can be optimized to have a net cost of busbar electricity that is equivalent to the conventional LWR plant, yet is not dependent on uranium ore prices or standard enrichment costs, since the fusion hybrid can be fueled by numerous fertile fuel resources. A nearer-term concept is also defined using a beam driven fusion driver in lieu of the longer term ignited operating mode.

Energetics of beam driven D-cycle plasmas.

The energetic characteristics of deuterium fueled fusion plasmas well below ignition and aided by neutral beam injection are investigated with the perspective of eventually being utilized in a fusion hybrid reactor. Particular emphasis is placed on the three modes of D-fusion cycles and on the role of the neutral beam ions as they effect the plasma ener-getics. Ion concentrations corresponding to steady state operation of the fusion cycles as well as total reaction rates and fusion gains are evaluated for regimes which tend to be identified with a two energy component reactor. The associated interrelation requirements on the temperature, density and magnetic confinement of the plasma are illustrated. It is shown how operational plasma constraints can be substantially relaxed by high energetic deuteron injection while retaining an energy viability sufficient for a synergetic fusion reac-tor concept.

Dynamic response of fusion reactor components with temperature-dependent properties

Transient response of thin, elastic, fluid filled semicircular cylindrical shells to thermal loads is developed using a combination of perturbation and spectral techniques applied to classic shell equations modified for variable material characteristics. The procedures are used to obtain displacements and stresses for cavity wall components of the laser fusion hybrid reactor SOLASE-H for three materials: 316 SS, graphite and zircaloy. Liquid sodium reduces the natural frequencies and the forced vibration response. A comparison of results for the three materials shows that although stresses are primarily determined by rates of change of elastic modulus and thermal strain coefficient, the effect of variable modulus is dominant.

Reaction Rate Calculations in Uranium and Thorium Blankets Surrounding a Central Deuterium-Tritium Neutron Source

Calculations were performed for /sup 238/U and /sup 232/Th blankets for a fusion hybrid reactor. Comparisons between results using ENDF/B-III and ENDF/B-IV cross sections for /sup 238/U were made. Corrections to the latter cross-section set were suggested, bringing the computed results close to the reported experimental ones. Computations using ENDF/B-IV /sup 232/Th cross sections were found to agree very well with experiment.

Tritium and Fissile Fuel Exchange between Hybrids, Fission Power Reactors, and Tritium Production Reactors

A mathematical model extending work by Gordon and Harms is developed to describe the fissile fuel and tritium flows in a fusion-fission system consisting of a fusion hybrid reactor, a tritium production reactor, and several fission power reactors. The hybrid reactor plays the role of a fuel factory, providing the fission reactors and the tritium production reactor with their fissile fuel needs. The tritium production reactor ( a fission reactor) is devoted primarily to producing tritium for subsequent use in the hybrid. Different combinations of these systems are found by shifting the tritium breeding function among the various parts. At steady state, the total thermal power in fission reactors per unit of fusion power depends only on the total conversion ratio of the fission reactors and the hybrid. An economic analysis is required to determine which combination of systems will produce electricity at the lowest costs.

The synergetics of the catalytic D-D-fusion-fission breeder

A parametric assessment of the D-D-fuelled fusion-fission hybrid reactor is undertaken. Based on the fusion hybrid reactor characteristic that the attainment of a “break-even” plasma is not essential for the maintenance of a viable system, its capabilities of net power generation and fissile fuel production at low plasma fusion gains are investigated in this paper. Analysis of the isotopic and energetic balances under steady-state conditions has resulted in the formulation of essential relationships involving fissile fuel yield, system power, fusion plasma efficiency, and plutonium content in the blanket material. The increasing systems design flexibility associated with the catalysed-D hybrid reactor suggests the definite possibility of an earlier introduction of advanced fusion cycles in the production of nuclear energy.