15 research outputs found
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An Inertial-Fusion Z-Pinch Power Plant Concept
With the promising new results of fast z-pinch technology developed at Sandia National Laboratories, we are investigating using z-pinch driven high-yield Inertial Confinement Fusion (ICF) as a fusion power plant energy source. These investigations have led to a novel fusion system concept based on an attempt to separate many of the difficult fusion engineering issues and a strict reliance on existing technology, or a reasonable extrapolation of existing technology, wherever possible. In this paper, we describe the main components of such a system with a focus on the fusion chamber dynamics. The concept works with all of the electrically-coupled ICF proposed fusion designs. It is proposed that a z-pinch driven ICF power system can be feasibly operated at high yields (1 to 30 GJ) with a relatively low pulse rate (0.01-0.1 Hz). To deliver the required current from the rep-rated pulse power driver to the z-pinch diode, a Recyclable Transmission Line (RTL) and the integrated target hardware are fabricated, vacuum pumped, and aligned prior to loading for each power pulse. In this z-pinch driven system, no laser or ion beams propagate in the chamber such that the portion of the chamber outside the RTL does not need to be under vacuum. Additionally, by utilizing a graded-density solid lithium or fluorine/lithium/beryllium eutectic (FLiBe) blanket between the source and the first-wall the system can breed its own fuel absorb a large majority of the fusion energy released from each capsule and shield the first-wall from a damaging neutron flux. This neutron shielding significantly reduces the neutron energy fluence at the first-wall such that radiation damage should be minimal and will not limit the first-wall lifetime. Assuming a 4 m radius, 8 m tall cylindrical chamber design with an 80 cm thick spherical FLiBe blanket, our calculations suggest that a 20 cm thick 6061-T6 Al chamber wall will reach the equivalent uranium ore radioactivity level within 100 years after a 30 year plant operation. The implication of this low radioactivity is that a z-pinch driven power plant may not require deep geologic waste storage
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Direct energy conversion in fission reactors: A U.S. NERI project
In principle, the energy released by a fission can be converted directly into electricity by using the charged fission fragments. The first theoretical treatment of direct energy conversion (DEC) appeared in the literature in 1957. Experiments were conducted over the next ten years, which identified a number of problem areas. Research declined by the late 1960's due to technical challenges that limited performance. Under the Nuclear Energy Research Initiative the authors are determining if these technical challenges can be overcome with todays technology. The authors present the basic principles of DEC reactors, review previous research, discuss problem areas in detail, and identify technological developments of the last 30 years that can overcome these obstacles. As an example, the fission electric cell must be insulated to avoid electrons crossing the cell. This insulation could be provided by a magnetic field as attempted in the early experiments. However, from work on magnetically insulated ion diodes they know how to significantly improve the field geometry. Finally, a prognosis for future development of DEC reactors will be presented
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Recyclable transmission line concept for z-pinch driven inertial fusion energy.
Recyclable transmission lines (RTL)s are being studied as a means to repetitively drive z pinches to generate fusion energy. We have shown previously that the RTL mass can be quite modest. Minimizing the RTL mass reduces recycling costs and the impulse delivered to the first wall of a fusion chamber. Despite this reduction in mass, a few seconds will be needed to reload an RTL after each subsequent shot. This is in comparison to other inertial fusion approaches that expect to fire up to ten capsules per second. Thus a larger fusion yield is needed to compensate for the slower repetition rate in a z-pinch driven fusion reactor. We present preliminary designs of z-pinch driven fusion capsules that provide an adequate yield of 1-4 GJ. We also present numerical simulations of the effect of these fairly large fusion yields on the RTL and the first wall of the reactor chamber. These simulations were performed with and without a neutron absorbing blanket surrounding the fusion explosion. We find that the RTL will be fully vaporized out to a radius of about 3 meters assuming normal incidence. However, at large enough radius the RTL will remain in either the liquid or solid state and this portion of the RTL could fragment and become shrapnel. We show that a dynamic fragmentation theory can be used to estimate the size of these fragmented particles. We discuss how proper design of the RTL can allow this shrapnel to be directed away from the sensitive mechanical parts of the reactor chamber
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Pulsed Power Driven Fusion Energy
Pulsed power is a robust and inexpensive technology for obtaining high powers. Considerable progress has been made on developing light ion beams as a means of transporting this power to inertial fusion capsules. However, further progress is hampered by the lack of an adequate ion source. Alternatively, z-pinches can efficiently convert pulsed power into thermal radiation, which can be used to drive an inertial fusion capsule. However, a z-pinch driven fusion explosion will destroy a portion of the transmission line that delivers the electrical power to the z-pinch. They investigate several options for providing standoff for z-pinch driven fusion. Recyclable Transmission Lines (RTLs) appear to be the most promising approach
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Low Mass Transmission Lines for Z-Pinch Driven Inertial Fusion
Recyclable transmission lines (RTL) are studied as a means of repetitively driving z pinches. The lowest reprocessing costs should be obtained by minimizing the mass of the RTL. Low mass transmission lines (LMTL) could also help reduce the cost of a single shot facility such as the proposed X-1 accelerator and make z-pinch driven space propulsion feasible. We present calculations to determine the minimum LMTL electrode mass to provide sufficient inertia against the magnetic pressure produced by the large currents needed to drive the z pinches. The results indicate an electrode thickness which is much smaller than the resistive skin depth. We have performed experiments to determine if such thin electrodes can efficiently carry the required current. The tests were performed with various thickness of materials. The results indicate that LMTLs should efficiently carry the large z-pinch currents needed for inertial fusion. We also use our results to estimate of the performance of pulsed power driven pulsed nuclear rockets
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The Role of Strong Coupling in Z-Pinch-Driven Approaches to High Yield Inertial Confinement Fusion
Peak x-ray powers as high as 280 {+-} 40 TW have been generated from the implosion of tungsten wire arrays on the Z Accelerator at Sandia National Laboratories. The high x-ray powers radiated by these z-pinches provide an attractive new driver option for high yield inertial confinement fusion (ICF). The high x-ray powers appear to be a result of using a large number of wires in the array which decreases the perturbation seed to the magnetic Rayleigh-Taylor (MRT) instability and diminishes other 3-D effects. Simulations to confirm this hypothesis require a 3-D MHD code capability, and associated databases, to follow the evolution of the wires from cold solid through melt, vaporization, ionization, and finally to dense imploded plasma. Strong coupling plays a role in this process, the importance of which depends on the wire material and the current time history of the pulsed power driver. Strong coupling regimes are involved in the plasmas in the convolute and transmission line of the powerflow system. Strong coupling can also play a role in the physics of the z-pinch-driven high yield ICF target. Finally, strong coupling can occur in certain z-pinch-driven application experiments
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Scaling and optimization of the radiation temperature in dynamic hohlraums
The authors have constructed a quasi-analytic model of the dynamic hohlraum. Solutions only require a numerical root solve, which can be done very quickly. Results of the model are compared to both experiments and full numerical simulations with good agreement. The computational simplicity of the model allows one to find the behavior of the hohlraum temperature as a function the various parameters of the system and thus find optimum parameters as a function of the driving current. The model is used to investigate the benefits of ablative standoff and axial convergence