Clyde Burnett, Peak to Peak.  Question: What is nuclear fusion and what are its advantages for power generation?

Answer:  Nuclear fusion is the reaction of two light nuclei into a larger stable nucleus, again with the release of energy and a decrease in mass. The absence of radioactive product nuclei is an obviously important advantage over fission power. The reaction requires that the combining nuclei be moved close together for the short range nuclear force reaction to occur.

Those positively charged nuclei must approach at high speed to overcome the repulsion of positive charges. (Our solar energy is from nuclear fusion with the high temperature constituents confined by the enormous gravity of the sun. The hydrogen bomb tests beginning at Bikini 1952 were triggered by the high temperatures of a fission explosion).

Laboratory controlled fusion experiments produce a high-temperature, electrically ionized gas (plasma) confined by magnetic fields. The triple engineering character of a successful power reactor must demonstrate a high-density plasma, with high temperature, and with long confinement time. This procedure has safety advantages over fission in that there is no risk of chain reaction or runaway explosion; any deviation from the high temperature or confinement will end the fusion reactions. An extremely important distinction over fission reactions is that the product nuclei are not radioactive. We may hope for successful fusion power characterized by unlimited hydrogen isotopes fuel (deutron H2, tritium H3).

I was actively involved in the fusion experiments at Princeton in 1957-58 while on leave from the Penn State Physics Dept. My experience with high spectral resolution spectroscopy helped determine the plasma temperatures and detect impurities from the container wall if the plasma was not confined. Lyman Spitzer, chairman of the astronomy department and director of this research, confided to me that he was inspired while on a skiing vacation to propose this experiment with a twisted figure eight magnetic field which he called the Stellarator. Initially there was hope for successful fusion power in about 20 years, but we soon discovered that a high temperature plasma was unstable and difficult to confine. Research shifted to elaborate magnetic fields designed with high speed computers followed by expensive experiments for design confirmation.

A December 2015 announcement stated that, after 19 years of construction, a new German Stellarator (with twisted magnet field added to a toroid) has just confirmed this successful confinement design with a helium plasma, and a February announcement featured the presence of Chancellor Merkel (PhD Physics) to initiate the continued research with a hydrogen plasma. It is hoped that the lengthy confirmation of a successful design will lead to eventual fusion power production.

The Chinese have also announced progress on their Experimental Advanced Superconductor Tokomak (EAST).

There is also a large experiment under construction in France called the ITER (International Thermal Experimental Reactor) with token US support. The Russian physicist Andrei Sakharov is credited with the design of the Tokomak. (He was also credited with design of the first Russian thermonuclear bomb and was awarded a Nobel prize for his work against nuclear bomb testing). The ITER Tokomak is designed to produce many times more fusion power than it consumes. Its large volume also decreases the likelihood that the plasma will strike the confining walls. While there is great hope for fusion power success, the ITER is far from complete and suffers delays due to funding.

In conclusion, I must note that the time scale and experimental uncertainties in the development and construction of nuclear fission and fusion power indicate a continued urgent environmental need for immediate solar and wind power replacement of fossil fuel power production.