US nuclear reactor startup Transatomic Power announced on 25 September that it is shutting down operations, after deciding that it can see no viable path to bringing its molten salt reactor designs to scale. However, it still wants its technology to play a role in the future of advanced nuclear reactors. Transatomic’s CEO and co-founder Leslie Dewan, noted: “We haven’t been able to scale up the company rapidly enough to build our reactor in a reasonable timeframe. It is therefore with a heavy heart that I must announce that Transatomic is suspending operations.” He added that the company will be “open-sourcing our intellectual property, making it available for any researchers — private, public or nonprofit — who want to continue the work we’ve started.”

Transatomic is in discussions with the Department of Energy’s (DOE’s) Gateway for Accelerated Innovation in Nuclear (GAIN) initiative to open its work to the public domain. This will include its work with DOE’s national laboratories, as well as the patents on its zirconium hydride-based molten salt reactors. “We’re going to be working with the Department of Energy to make sure we’re complying with export controls for all of this,” Dewan noted.

She added that Transatomic is also releasing its patents in the European Union, Russia and China for its particular version of liquid-fuelled reactor designs. “We’re going to be putting up all of our white papers, all of our technical reports we’ve done in conjunction with the national labs, all the patents that have been granted, and those that are still in process,” she said.

This work centres on Transatomic’s research into “spectral shift reactor design”, which alters the amount of moderator, or material used to slow down neutrons to speeds capable of sustaining fission, as a function of time over the course of the reactor’s fuel cycle, she explained. Transatomic’s patents deal with the use of zirconium hydride as a moderator, combined with its particular version of molten salt-based reactor design, based on work done at Oak Ridge National Laboratory. It also holds patents on the manufacture of cladding, she said.

Its current work does not include Transatomic’s initial goal of using used nuclear fuel to power reactors. Dewan and co-founder Mark Massie launched the company in 2011, while they were doctoral candidates at the Massachusetts Institute of Technology, intending to develop a reactor that could recycle used fuel rods. On this basis, Transatomic raise $2 million in 2014 from Peter Thiel's Founders Fund, and a further $2.5 million in 2015 from Acadia Woods Partners, Founders Fund, and Daniel Aegerter, chairman of the Swiss fund Armada Investment AG.

However, in 2016, the company has to retract previous claims, after an informal review by MIT professors found errors in its calculations, including a claim that its design could produce "75 times more electricity per ton of mined uranium than a light-water reactor” of typical design. This figure was subsequently reduced to “more than twice” the usual reactor’s output per unit of uranium in a company report of November 2016.

Dewan said the decision to move away from a design that would consume used fuel “was a real blow to me personally”. But investors supported the company’s post-2016 work on its molten salt and zirconium nitride design, because “for them, the main value proposition was the safety case of these molten salt reactors and their low cost compared to fossil fuels”.

She noted that the number of advanced nuclear reactor projects have increased since Transatomic was founded to about 70 worldwide today. “Some are doing incredibly well,” she noted. These include TerraPower, a startup backed by Bill Gates, which has partnered with DOE’s GAIN programme and Southern Company to develop its molten chloride fast reactor design. This is expected to invest $20 million in a test facility planned to open next year. Terrestrial Energy, a startup using an integral molten salt reactor design, won $8 million in funding in 2016, and has announced a two-year R&D project with DOE and Southern Company. NuScale Power, a startup with a small modular reactor design, in May won Phase 1 approval of its design from the Nuclear Regulatory Commission, and recently selected BWX Technologies to begin manufacture its units.