|Fig. 1: Enrico Fermi and the Via Panisperna boys in the courtyard of Rome University's Physics Institute in Via Panisperna, circa 1930. From left to right: Oscar D'Agostino, Emilio Segrè, Edoardo Amaldi, Franco Rasetti and Enrico Fermi. (Source: Wikimedia Commons)|
From the early 1960s to the late 1980s, nuclear energy in commercial applications developed at an accelerated pace. This was partly due to the 1973 oil crisis and a global movement towards a more independent energy infrastructure. As the 1990s turned around, the continuous research in the field stagnated for political reasons and technological safety concerns after disastrous accidents took place, including those in Chernobyl and Three Mile Island. Due to major government funding cuts, several companies filed for bankruptcy and the field of nuclear energy became much less popular for young engineers. 
Today, the popularity of nuclear energy in the US is picking up the pace again. Oakridge Institute for Science and Education reports that the number of B.S. degrees granted in 2013 was 7 percent higher than in 2012 and 25 percent higher than in 2011 in 32 U.S. universities with nuclear engineering programs.  Participation from the academic domain can play a critical role in the development of nuclear technology. An example of such fruitful research groups is observed in Fig. 1 showing Enrico Fermi and the Via Panisperna boys, whose contribution to the science are often considered the founding basis for nuclear development. This momentum pickup could potentially be attributed to a combination of reasons which include but are not limited to: an increasing energy demand, a security of supply of cheap uranium, climate change mitigation, tighter safety policies and improvements in grid stability.
The world's first large-scale nuclear power plant at Shippingport, Pennsylvania, was owned by the US Atomic Energy Commission, but built and operated by the Duquesne Light and Power Company in 1958.  Today, almost all the commercial reactors in the USA are owned by private companies.  Fifty years later, a new surge of nuclear companies, popularly referred to today as the Nuclear Renaissance, has created a market for many new scientist and engineers to take their startup ideas to the market. I discuss below two examples of such companies: one in nuclear fission and the other in nuclear fusion which have claimed breakthrough technologies in the field.
Helion Energy is an American company based in Redmond, WA founded by Dr. David Kirtley who currently serves as the company's CEO.
The primary fusion technology was developed by Dr. John Slough, a research professor at the University of Washington. It operates on the concept of Magneto-Inertial Fusion and makes use of the stability of steady magnetic fusion and the heating of pulsed inertial fusion. Some of its innovative features include a self-supplied deuterium fuel extracted from water and helium from the exhaust as well as a method of magnetically compressing and heating the fuel with modern solid state electronics so as to avoid expensive equipment such as lasers, piston and beam techniques. [5,6]
The engine operates in the following manner: The fuel is injected into the reactor on opposite ends of the reactor and heated until a plasma is formed. Pulsed magnetic fields at 20 Tesla are used to accelerate the plasma into a chamber at over 1 million miles per hour. A strong magnetic field compresses the merged plasma to fusion temperature and pressures. Charged particle formed from the deuterium and helium nuclei fusion push back on the compressing magnetic field, directly converting the expanding plasma into electricity. The Fusion engine is designed to produce 8 times as much energy from this push-back mechanism as what is put in for the heating and compression of the plasma. [5,6]
Transatomic Power is an American startup based in Kendall Square, Massachusetts founded by Leslie Dewan and Mark Massie in 2010. Leslie Dewan, a Ph.D graduate in nuclear engineering, currently serves as the CEO of the company.
Transatomic Power is developing a molten-salt nuclear plant. This technology was first developed in the 1960s and was famous for its safety mechanism including: passive shutdown ability, low pressure piping, negative void and temperature coefficients, and chemically stable coolants.  What Transatomic has claimed that sets it apart from the older generations of molten salt reactors is a metal hydride moderator and an LiF-(Heavy metal)F4 fuel salt, which allows for a more compact reactor model. Furthermore, the reactor can operate on fuel enriched to a minimum of 1.8% U-235, or light water reactor waste instead of the historical 33 % enriched U-235 used at the Oak Ridge Molten Salt Reactor Experiment.  This is done through a 50 % reduction in the size of the core reactor, allowing for a five-fold increase in fuel salt for the same core. 
The reactor makes use of a zirconium hydride as a moderator. The fuel is liquified by dissolving the uranium in a molten fluoride salt for higher thermal transfer efficiencies. The majority of fission products are claimed to be continuously removed via an off-gas system whilst small amounts of low enriched fuels are continuously added. This however is a task that is exceedingly difficult to do. If achieved, it would maintain a constant fuel mass, and allow the reactor to remain critical for decades. One of the safety mechanism of this molten salt reactor is that it operates at about half of the salt's boiling point, i.e. 700 degrees Celsius. So if the reactor temperature were to climb rapidly, the freeze valves would melt and the fuel would be drained from the reactor into a high surface area region for faster cooling. 
The company has so far been planning the design of a 500 MW molten salt reactor that can be manufactured economically at a central location and transported by rail to the reactor site. The overnight cost of the reactor is predicted to be on the order $2 billion. 
© Marc Khalaf. The author grants permission to copy, distribute and display this work in unaltered form, with attribution to the author, for noncommercial purposes only. All other rights, including commercial rights, are reserved to the author.
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 "Nuclear Engineering Enrollments and Degrees Survey, 2013 Data," Oak Ridge Institute for Science and Education, 2014.
 J. C. Clayton, "The Shippingport Pressurized Water Reactor and Light Water Breeder Reactor," Westinghouse Electric Corporation, WAPD-T-3007, October 1993.
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 G. Votroubek et al., "Formation of a Stable Field Reversed Configuration through Merging," J. Fusion Energy 27, 123 (2008).
 J. Slough, G. Votroubek, and C. Pihl, "Creation of a High-Temperature Plasma Through Merging and Compression of Supersonic Field Reversed Configuration Plasmoids," Nucl. Fusion 51, 053008 (2011).
 Technical White Paper," Transatomic Power, March 2014.
 J. Freed, Back to the Future: Advanced Nuclear Energy and the Battle Against Climate Change (Brookings Institute Press, 2014).