Ryan P. Abbott

A SUSTAINABLE NUCLEAR FUEL CYCLE BASED ON LASER INERTIAL FUSION ENERGY

Abstract The National Ignition Facility (NIF), a laser-based Inertial Confinement Fusion (ICF) experiment designed to achieve thermonuclear fusion ignition and burn in the laboratory, will soon be completed at the Lawrence Livermore National Laboratory. Experiments designed to accomplish the NIF’s goal will commence in 2010, using laser energies of 1 to 1.3 MJ. Fusion yields of the order of 10 to 35 MJ are expected soon thereafter. We propose that a laser system capable of generating fusion yields of 35 to 75 MJ at 10 to 15 Hz (i.e., ≈ 350- to 1000-MW fusion and ≈ 1.3 to 3.6 x 1020 n/s), coupled to a compact subcritical fission blanket, could be used to generate several GW of thermal power (GWth) while avoiding carbon dioxide emissions, mitigating nuclear proliferation concerns and minimizing the concerns associated with nuclear safety and long-term nuclear waste disposition. This Laser Inertial Fusion Energy (LIFE) based system is a logical extension of the NIF laser and the yields expected from the early ignition experiments on NIF. The LIFE concept is a once-through, self-contained closed fuel cycle and would have the following characteristics: (1) eliminate the need for uranium enrichment; (2) utilize over 90% of the energy content of the nuclear fuel; (3) eliminate the need for spent fuel chemical separation facilities; (4) maintain the fission blanket subcritical at all times (keff <0.90); and (5) minimize future requirements for deep underground geological waste repositories and minimize actinide content in the end-of-life nuclear waste below the (the lowest). Options to burn natural or depleted U, Th, U/Th mixtures, Spent Nuclear Fuel (SNF) without chemical separations of weapons-attractive actinide streams, and excess weapons Pu or highly enriched U (HEU) are possible and under consideration. Because the fission blanket is always subcritical and decay heat removal is possible via passive mechanisms, the technology is inherently safe. Many technical challenges must be met, but a LIFE solution could provide a sustainable path for worldwide growth of nuclear power for electricity production and hydrogen generation.

Annular vortex generation for inertial fusion energy beam-line protection

The use of swirling annular vortex flow inside beam entrance tubes can protect beam-line structural materials in chambers for heavy-ion inertial fusion energy (IFE) applications. An annular wall jet, or vortex tube, is generated by injecting liquid tangent to the inner surface of a tube wall with both axially and azimuthally directed velocity components. A layer of liquid then lines the beam tube wall, which may improve the effectiveness of neutron shielding, and condenses and removes vaporized coolant that may enter the beam tubes. Vortex tubes have been constructed and tested with a thickness of three-tenths the pipe radius. Analysis of the flow is given, along with experimental examples of vortex tube fluid mechanics and an estimate of the layer thickness, based on simple mass conservation considerations.

Thick-Liquid Blanket Configuration and Response for the HIF Point Design

Abstract This paper describes the thick-liquid blanket system of the Robust Point Design (RPD-2002). RPD-2002 is the first self-consistent description of a heavy-ion fusion accelerator, final focus, target, magnet shielding, and thick-liquid blanket design. The 120 beams are delivered to the target from two sides, in 9x9 arrays, with 5.4° between rows giving a maximum beam angle from the target axis of 24°. The chamber employs thick-liquid protection, using liquid jets that have been demonstrated to have the required geometric precision in scaled water experiments. Other aspects of the chamber design, not directly related to the beam-line shielding, have been kept the same as the HYLIFE-II design.

Abatement of shocks during disruption of porous thick-liquid blankets in HYLIFE-type inertial fusion chambers

Abstract The dispersion and control of liquid kinetic energy and momentum are a major issue after the explosion of targets in an inertial fusion energy (IFE) thick-liquid chamber. For HYLIFE-type IFE chambers the desired repetition rate for shots varies from 5 to 10 Hz—a rate much too fast for natural gravity clearing of liquid debris. The impulse load delivered by a single shot generates enough kinetic energy in disrupted liquid material to do significant damage to surrounding solid structures. However, carefully designed jet arrays with regular void spacing can diffuse and dissipate kinetic energy that could damage adjacent structures, and rapidly moving, oscillating jets can dynamically clear the chamber center. A brief theoretical and mathematical background is given for this method of shock abatement, using the current Berkeley jet array experiment as a representative geometry.

Experimental Investigation of Z-Pinch IFE Chamber Liquid Structure Response

Abstract Z-Pinch IFE chamber fluid mechanics can be studied using simulant fluids such as water in reduced scale facilities. The use of porous liquid and solid blanket materials provides the key to mitigating blast effects from fusion reaction. The UCB Vacuum Hydraulics Experiment (VHEX) was recently upgraded with a large, annular inlet nozzle system to produce an annular porous liquid curtains to study Z-Pinch IFE chamber response. Explosives experiments in VHEX studied the response of the liquid structure to the detonation of high explosive C-4. The experiments demonstrated that the crushing of porous liquid structures is effective in transferring momentum uniformly into the blanket mass. No significant high-speed jetting or spall was observed exiting the shocked liquid structure. Independent measurement of the transient pressure history, coupled with high-speed video of the blanket response and final velocity, will provide the basis to validate gas dynamics and blanket response models.

Experience with Conversion of CAD to Monte Carlo Particle Transport Models

Abstract During the past two years a team at Lawrence Livermore National Laboratory (LLNL) has used Raytheon’s TopAct code to convert a variety of CAD models into TART and MCNP Monte Carlo input files. TopAct offers the possibility of enormous savings by largely eliminating the need for manual generation of models via combinatorial geometry. Also, TopAct is expected to deliver improvements in quality assurance and configuration management. We detail our experiences with various test problems. The reader will see the steady improvements that have been made in the conversion process and understand our expectations for further progress. Finally, we explain how TopAct will become a cornerstone of our future neutronics efforts.

Ion Deflection for Final Optics in Laser Inertial Fusion Power Plants

Left unprotected, both transmissive and reflective final optics in a laser-driven inertial fusion power plant would quickly fail from melting, pulsed thermal stress, or degradation of optical properties as a result of ion implantation. One potential option for mitigating this threat is to magnetically deflect the ions such that they are directed to a robust energy dump. In this paper we detail integrated studies that have been carried out to assess the viability of this approach for protecting final optics.