Nuclear engineering alumnus shares vision for post-ignition fusion development

Nuclear fusion holds a promise to deliver the ultimate solution to the humanity’s energy needs.

With the practical, economically feasible scheme to produce fusion energy in large quantities, an inexhaustible energy source would become available. Nuclear fusion exhibits many of the attractive features of renewable energy sources, without many of their shortcomings.

Nuclear fusion is carbon-free, produces only short-lived nuclear waste, relies on cheap, abundant fuel (hydrogen and lithium), and is characterized by extremely high-energy density. Thus it potentially enables compact solutions for future increasing terrestrial and extraterrestrial energy needs. The mainstream fusion research is focused on two alternative methods for production of fusion energy in large quantities, with net energy gain: magnetic confinement and inertial confinement. Recently, both methods have received much attention. The premier inertial confinement fusion experiment is coming online in spring 2009, and the premier magnetic fusion experiment, now under construction, expects its first experimental results around 2020.

As the project manager of the National Ignition Facility (NIF), the world’s premier inertial confinement fusion project, I was responsible for overseeing the construction of one of the largest and most challenging scientific experiments to date—the size of three football fields. Recently completed and dedicated, NIF is now embarking on the National Ignition Campaign, in which controlled release of nuclear power from fusion is expected to result for the first time in ignition and net energy gain.

Activation of NIF is an unprecedented opportunity for fusion research, both in its scale and its expectations. As the first fusion experiment expected to reach ignition, NIF hopes to bring fusion energy to market within this
generation. While the ignition on NIF will not immediately change the energy playing field, it will likely have significant long-term impact once the scientific basis for ignition is established experimentally.

As early as in the 1950s, scientists contemplated the possibility of a transition from fission to fusion economy that would utilize the hybrid energy systems based on both technologies. The team at Lawrence Livermore National Laboratory (LLNL) recently brought this idea forward again, but in an expanded form particularly well-suited for laser fusion. As originally proposed, in hybrid fission-fusion systems fast neutrons produced by the fusion component of the reactor can be used to increase the energy production by the use of a fissionable blanket surrounding the reactor. The hybrid fusion-fission reactor relaxes the stringent requirements on the efficiency of its fusion component and represents a highly efficient breeder for fission reactor fuel: A mid-size hybrid fusion-fission reactor could produce fissile material for fission reactors at a rate up to tens of times greater than conventional fission breeder reactors.

The LLNL concept, termed LIFE (laser inertial fusion engine), offers additional capabilities, which could address many of the challenges of the current fission nuclear fuel cycle. Specifically, the LIFE concept looks to use the spent nuclear fuel from fission reactors and weapons-grade plutonium in the fission blanket. This approach can dramatically improve the burnup of fission fuels, by as much as a factor of 100. Thus the possibility exists to reduce the rate of production of nuclear waste by a factor of 100, eliminate the stockpiles of weapons-grade plutonium, and pursue the utilization of cheap and abundant fuels: hydrogen and natural uranium or thorium.

The fusion ignition, likely to be demonstrated on NIF in the next several years, will be a momentous event in fusion research, one that will again shift public attention to this pathway to energy production with nearly unlimited potential. Envisioned as the stepping stone from the fission economy to fusion economy, the LIFE program’s central advantage will be the advanced hybrid fuel cycle, resulting in minimal nuclear waste production and the minimization of the current stockpiles of spent nuclear fuel.