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| Fig. 1: Integral Molten Salt Reactor. (Source: Wikimedia Commons) |
The nuclear energy sector has been plagues by a plethora of challenges in recent decades in regard to sufficiently and safely supplying the clean energy that first drove its expansion. The conventional water- cooled reactors of the past half-century have proven volatile to a variety of safety standards. Whether it is storage of high-level waste, or an ability to prevent a meltdown, conventional nuclear reactors employed in the United States today are not cutting it. Thus, the high amount of nuclear plant shutdowns and failed attempts at constructing new reactors has risen recently. Attempts to solve these problems in the form of new reactor technology have been in the works since the 1970s with the first nuclear meltdown at Three Mile Island. This is where Terrestrial Energy, and its Integral Molten Salt Reactor (IMSR) aims to break the mold. Terrestrial Energy brought together business and technological leaders to create this new technology, that in their view is vastly superior to any other technology. The reliability and cost-competitiveness of their IMSR is what separates itself from other nuclear reactor technologies.
The innovation of the IMSR is its nuclear fuel, molten salt. The IMSR unit is capable of producing 195 megawatts of electricity per unit. [1] Although, the developers at Terrestrial Energy are designing three separate versions of the IMSR (See Fig. 1), which produces three different power levels, 32.5, 141, and 291 megawatts of electricity. The Terrestrial Energy IMSR is a graphite-moderated MSR burner, with the main difference between Terrestrials IMSR and other MSRs being the absence of a fuel salt drain tank. The molten salt plays a key role in this reactors advantage over conventional water-fed nuclear reactors. The possibility of a meltdown is drastically decreased using the molten salt, rather than water. [1] The molten salt used has a melting point just over the operating temperature of the vessel, with the frozen buffer salt liner having a heating capacity high enough to passively cool down the vessel for days in case of a secondary cooling failure. The fuel used in the IMSR contains a mixture of low enriched uranium fluoride and a primary cooling salt. Spent fuel has become a sticking point for nuclear reactors as the ability to properly dispose of high-level waste for the long-term future is not currently available. [1] The IMSR's spent fuel is a salt already enclosed in a circular cylinder can, compared to conventional pressurized water reactors (PWR) which store their spent fuel in long right square cylinder assemblies. The PWRs spent fuel must be stored in storage containers, while IMSR's spent fuel can be geologically stored in a simpler and cheaper fashion.
The IMSR reactor design put forth by Terrestrial Energy promises to be an interesting new foray into the nuclear reactor industry; an industry in desperate need of modern technological advances to spurn its current drawbacks, which are numerous. The difficulty in employing the IMSR design in the United States with any speed is the regulation process needed for a new nuclear reactor design to pass. Recognizing the need to find some alternative energy to fossil fuels should put people on notice to advance a new type of nuclear reactor as fast as possible.
© Erik Miller. The author warrants that the work is the author's own and that Stanford University provided no input other than typesetting and referencing guidelines. 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.
[1] L. Samalova, O. Chvala, and G. I. Maldonado, "Comparative Economic Analysis of the Integral Molten Salt Reactor and an Advanced PWR using the G4-ECONS Methodology," Ann. Nucl. Energy 99, 258 (2017).
