How will nuclear fusion develop in a carbon-free world?

On December 5, Dr. Stephen. P. Obenschain was awarded the 2012 Fusion Power Associates’ (FPA) Leadership Award for his leadership qualities in accelerating the development of fusion. Dr. Obenschain is the branch-head of the U.S. Naval Research Laboratory Plasma Physics Division.

Dr. Obenschain’s most significant contributions to the field are concerned with the development and deployment of inertial fusion facilities. Specifically, inertial fusion involves the focusing of high-power lasers into a really small capsule containing deuterium, forcing the atomic nuclei to fuse to produce helium and release large amounts of energy.

There is one other way to induce fusion called magnetic containment. This is the more ubiquitously adopted technique in global attempts to generation power from fusion reactions. A magnetic containment system also resides at the heart of the International Thermonuclear Reactor Experiment (ITER) in Cadarache, France, that seeks to produce more power than it consumes while in operation ere the decade is out.

I got in touch with Dr. Obenschain and asked him a few questions, and he was gracious enough to reply. I didn’t do this because I wanted a story but because India stands to become one of the biggest beneficiaries of fusion power if it ever becomes a valid option, and wanted to know what an engineer at the forefront of fusion deployment thought of such technology’s impact.

Here we go.

What are your comments on the role nuclear fusion will play in a carbon-free future?

Nuclear fusion has the potential to play a major long term role in a clean, carbon free energy portfolio. It provides power without producing greenhouse gases. There is enough readily available fuel (deuterium and lithium) to last thousands of years. Properly designed fusion power plants would produce more readily controllable radioactive waste than conventional fission power plants, and this could alleviate long term waste disposal challenges to nuclear power.

Inertial confinement has seen less development than its magnetic counterpart, although the NIF is making large strides in this direction. So how far, in your opinion, are we from this technology attaining break-even?

Successful construction and operation of the National Ignition Facility (NIF) at Lawrence Livermore National Laboratory has demonstrated that a large laser system with the energy and capabilities thought to be required for ignition can be built. NIF is primarily pursuing indirect drive laser fusion where the laser beams are used to produce x rays that drive the capsule implosion.

The programs at the Naval Research Laboratory (NRL) and the University of Rochester’s Laboratory for Laser Energetics (LLE) are developing an alternate and more efficient approach where the laser beams directly illuminate the pellet and drive the implosions. Technologies have been invented by NRL and LLE to provide the uniform illumination required for direct drive. We believe that direct drive is more likely to achieve the target performance required for the energy application.

Many of the key physics issues of this approach could be tested on NIF. Following two paths would increase the chances of successful ignition on NIF.

Both the ITER and NRL/NIF are multi-billion dollar facilities, large and wealthy enough to create and sustain momentum on fusion research and testing. However, because of the outstanding benefits of nuclear fusion, smaller participants in the field are inevitable and, in fact, necessary for rapid innovation. How do you see America’s and the EU’s roles in this technology-transfer scenario panning out?

The larger facilities take substantial time to build and operate, so they inherently cannot reflect the newest ideas. There needs to be continued support for new ideas and approaches, that typically result in substantial improvements, and that often will come from the smaller programs.

Most research in fusion is published in the open scientific and technological journals so there is already a free flow of ideas. The main challenge is to maintain funding support for innovative fusion research given the resources required by the large facilities.

What are the largest technical challenges facing the development of laser-fusion?

Development of laser fusion as an energy source will require an integrated research effort that addresses the technological and engineering issues as well as developing the laser-target physics. We need efficient and reliable laser drivers that can operate at 5 to 10 pulses per second (versus the few shots per day on NIF). We need to develop technologies for producing low-cost precision targets. We need to develop concepts and advanced materials for the reaction chamber.

We (NRL laser fusion) have advocated a phased approach which takes advantage of the separable and modular nature of laser fusion. For example the physics of the laser target interaction can be tested on a low repetition rate system like NIF, while the high repetition laser technology is developed elsewhere.

In the phased plan sub-full scale components would be developed in Phase I, full scale components would be developed in Phase II (e.g. a full-scale laser beamline), and an inertial Fusion Test Facility built and operated in Phase III. The Fusion Test Facility (FTF) would be a small fusion power plant that would allow testing and development of components and systems for the full-scale power plants that would follow.

Use of NRL’s krypton fluoride (KrF) laser technology would increase the target performance (energy gain) and thereby reduce the size and cost of an FTF. This research effort would take some time, probably 15 to 20 years, but with success we would have laid the path for a major new clean energy source.


(This blog post first appeared at The Copernican on December 16, 2012.)