Kevin J. Kramer

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.

Timely Delivery of Laser Inertial Fusion Energy (LIFE)

Abstract The National Ignition Facility (NIF), the world’s largest and most energetic laser system, is now operational at Lawrence Livermore National Laboratory. A key goal of the NIF is to demonstrate fusion ignition for the first time in the laboratory. Its flexibility allows multiple target designs (both indirect and direct drive) to be fielded, offering substantial scope for optimization of a robust target design. In this paper we discuss an approach to generating gigawatt levels of electrical power from a laser-driven source of fusion neutrons based on these demonstration experiments. This “LIFE” concept enables rapid time-to-market for a commercial power plant, assuming success with ignition and a technology demonstration program that links directly to a facility design and construction project. The LIFE design makes use of recent advances in diode-pumped, solid-state laser technology. It adopts the paradigm of Line Replaceable Units utilized on the NIF to provide high levels of availability and maintainability and mitigate the need for advanced materials development. A demonstration LIFE plant based on these design principles is described, along with the areas of technology development required prior to plant construction.

CHAMBER DESIGN FOR THE LASER INERTIAL FUSION ENERGY (LIFE) ENGINE

Abstract The Laser Inertial Fusion Energy (LIFE) concept is being designed to operate as either a pure fusion or hybrid fusion-fission system. The present work focuses on the pure fusion option. A key component of a LIFE engine is the fusion chamber subsystem. It must absorb the fusion energy, produce fusion fuel to replace that burned in previous targets, and enable both target and laser beam transport to the ignition point. The chamber system also must mitigate target emissions, including ions, x-rays and neutrons and reset itself to enable operation at 10-15 Hz. Finally, the chamber must offer a high level of availability, which implies both a reasonable lifetime and the ability to rapidly replace damaged components. An integrated design that meets all of these requirements is described herein.

Thermal and Mechanical Design Aspects of the LIFE Engine

Abstract The Laser Inertial confinement fusion - Fission Energy (LIFE) engine encompasses the components of a LIFE power plant responsible for converting the thermal energy of fusion and fission reactions into electricity. The design and integration of these components must satisfy a challenging set of requirements driven by nuclear, thermal, geometric, structural, and materials considerations. This paper details a self-consistent configuration for the LIFE engine along with the methods and technologies selected to meet these stringent requirements. Included is discussion of plant layout, coolant flow dynamics, fuel temperatures, expected structural stresses, power cycle efficiencies, and first wall survival threats. Further research to understand and resolve outstanding issues is also outlined.

LIFE Tritium Processing: A Sustainable Solution For Closing The Fusion Fuel Cycle

Abstract The Laser Inertial Fusion Energy (LIFE) power plant is being designed to deliver a transformative source of safe, secure, sustainable electricity, in a time scale that is consistent with the global energy market needs. The LIFE market entry plant will demonstrate the feasibility of a closed fusion fuel cycle, including tritium breeding, extraction, processing, re-fueling, accountability and safety, in a steady-state power-producing device. While many fusion plant designs require large quantities of tritium for startup and operations, a range of design choices made for the LIFE fuel cycle act to reduce the inprocess tritium inventory. The high fractional burn-up (~30%) in an Inertial Fusion Energy (IFE) capsule relaxes the tritium breeding requirements, while the use of only milligram quantities of fuel per shot and choice of a pure lithium heat transfer fluid substantially reduce the amount of material entrained in the facility. Additionally, the high solubility of tritium in the lithium breeder is expected to mitigate the need for development of permeation barriers in the engine systems, normally required to control routine releases within the allowable regulatory limits. The present paper offers an overview of the design of the LIFE fuel cycle, including a summary of the technology development plan consistent with the delivery schedule of the LIFE market entry plant.

Parameter Study of an Inertial Fusion Energy Chamber Response Using the 1-D BUCKY Radiation Hydrodynamics Code

Abstract A parameter study of a proposed inertial fusion energy chamber is performed. A baseline case of a 6-m-radius chamber filled with 6 μg/cm3 of xenon is studied in detail. The maximum first-wall temperature is shown to be 1136 K with an overpressure of 5.83 + 10−3 MPa. A parameter sweep is conducted for the chamber by adjusting the first-wall radius from 4 to 14 m, changing the gas density and changing the fill gas from xenon to argon. The results set limits on the first-wall radius for different gases and densities. Analytic fits to simulation results allow their use in overall engine design trade-off studies.

FUSION-FISSION BLANKET OPTIONS FOR THE LIFE ENGINE

Abstract The Laser Inertial Fusion Energy (LIFE) concept is being developed to operate as either a pure fusion or hybrid fusion-fission system. The hybrid version is designed to generate power and burn both fertile and fissile nuclear fuel. The fuel blanket is composed of TRISO-based fuel cooled by a molten salt. Low-yield (˜25-40 MJ) targets and a repetition rate of ˜10-15 Hz produce a 300-500 MW fusion source. When this fusion power is coupled to a compact (2-4 m diameter) target chamber, a 14 MeV neutron flux of ˜2 × 1014 n/cm2-s drives fissile production and destruction in the fuel blanket providing an additional energy gain of 4-8, depending on the fuel and design objective. We employ a methodology using 6Li as a neutron absorber to generate self-sustaining tritium production for fusion and to maintain constant power over the lifetime of the engine. In a single pass, fertile LIFE blankets achieve uranium and thorium utilization beyond 80% without chemical reprocessing or isotopic enrichment. Fissile blankets destroy more than 90% of the initial load of weapons grade plutonium or highly enriched uranium.

LIFE: a sustainable solution for developing safe, clean fusion power.

AbstractThe National Ignition Facility (NIF) at the Lawrence Livermore National Laboratory (LLNL) in California is currently in operation with the goal to demonstrate fusion energy gain for the first time in the laboratory—also referred to as “ignition.” Based on these demonstration experiments, the Laser Inertial Fusion Energy (LIFE) power plant is being designed at LLNL in partnership with other institutions with the goal to deliver baseload electricity from safe, secure, sustainable fusion power in a time scale that is consistent with the energy market needs. For this purpose, the LIFE design takes advantage of recent advances in diode-pumped, solid-state laser technology and adopts the paradigm of Line Replaceable Units used on the NIF to provide high levels of availability and maintainability and mitigate the need for advanced materials development. The LIFE market entry plant will demonstrate the feasibility of a closed fusion fuel cycle, including tritium breeding, extraction, processing, refueling, accountability, and safety, in a steady-state power-producing device. While many fusion plant designs require large quantities of tritium for startup and operations, a range of design choices made for the LIFE fuel cycle act to reduce the in-process tritium inventory. This paper presents an overview of the delivery plan and the preconceptual design of the LIFE facility with emphasis on the key safety design principles being adopted. In order to illustrate the favorable safety characteristics of the LIFE design, some initial accident analysis results are presented that indicate potential for a more attractive licensing regime than that of current fission reactors.

Adjoint-based uncertainty analysis for essential reactions in a laser inertial fusion engine

Abstract This study establishes a procedure for constructing explicit and adjoint-based implicit sensitivities with MCNP5. Using these methods, an instantaneous sensitivity-based uncertainty analysis is performed on the depleted uranium hybrid LIFE (Laser Inertial Fusion Energy) blanket. Explicit sensitivities and uncertainties are calculated for (n, 2n), tritium production, fission, and radiative capture reaction rates during the fuel lifecycle. Nuclear data uncertainties and Monte Carlo counting precision are compared in a convergence study and the compounding of the two is quantified to gauge the validity of the analysis. A multi-group cross-section library is generated for adjoint calculations and selected adjoint distributions are shown and discussed.