Moltex, Elysium reactors to put used fuel to work

Recycling and reprocessing spent nuclear fuel (SNF) can be expensive and stokes proliferation concerns, but advanced reactor developers Moltex and Elysium say their technology will change how the industry deals with nuclear waste.

Work on molten salt reactors (MSRs) first appeared in the United States while nuclear power was in its infancy in the 1960s through to the 1970s at an experimental 7.34 MW (thermal) MSR at Oak Ridge National Laboratory.

Commercially, though, MSRs slipped by the wayside and the light water reactos became the default.

MSRs, as the name implies, uses molten salts in the reactor core instead of water, which grants them enhanced efficiency, load following, enhanced safety characteristics, and the ability to operate at high temperatures.

As new technology ushers in a range of Generation IV advanced reactors, designs such as those being developed by Elysium and Moltex have the added benefit of running on SNF and both, say the developers, can do so safely and at a competitive cost.

“Typically, other attempts at recycling haven’t been economical, which is why they’ve not carried on, but we do seem to have big margins on our economic case. It seems to be really, very viable and makes a lot of economic sense,” says Moltex CEO Rory O’Sullivan.

The so-called ‘social license’, or public acceptance of the technology, is also a major driver for both developers.

“There’s still a lot of social opposition to nuclear waste; that it shouldn’t be disposed of, and it shouldn’t even exist in the first place, so we really see that the biggest advantage to this reactor is dealing with, and destroying, long-lived nuclear waste,” says O’Sullivan.

(Source: World Nuclear Association) 

Chlorinating SNF

The Elysium is a fast-spectrum molten salt reactor that runs on chopped up SNF that is poured into molten sodium and potassium chloride, or table and road salt, at over 500 Celsius, explains Chief Technology Officer and Founder of Elysium Ed Pheil.

Much of the SNF – remaining uranium, plutonium, minor actinides, and fission products – becomes chlorinated leaving only some noble metals, which are filtered out as particulates, and noble gases, which are collected.

This is not reprocessing as defined by the Department of Energy’s National Nuclear Security Administration (NNSA), says Pheil.

“We are recycling the waste without any associated separations other than what naturally occurs – the off gassing and the particulates,” Pheil says. “But that’s not enough to run the reactor. You also need an additional fissile.”

In the United States, that additional fissile is weapons-grade plutonium, of which there is an excess of some 61.5 tons. 

The Elysium reactor would use ten parts stored fuel to one part plutonium, Pheil explains, adding that his reactor would denature the weapons grade plutonium, before sending it to the reactors for start up, thus rendering it unusable in any kind of weapon, rather than diluting it and storing it in casks, which is the current U.S. government plan.

Pheil says Elysium can reduce the pyro-processing method from seven distinct chemical steps to just one, bringing costs to below that of enriching uranium.

“We would like to have a pilot fuel production facility start by 2025 and, at which point, since we’re destroying weapons grade plutonium, that begins our revenue stream by getting rid of plutonium and spent fuel,” says Pheil.

Moltex in Canada

The British/Canada-based Moltex Energy’s Stable Salt Reactor – Wasteburner (SSR-W) design, which uses low-purity molten salt fuel in conventional fuel pins rather than pumping fuel salts around the system – comes with its own recycling process WAste to Stable Salt (WATSS).

The company has said the Levelized Cost of Energy (LCOE) of its SSR is estimated at $44.64/MWh for a nth-of-a-kind 1GW plant based on conservative estimates for Operations and Maintenance (O&M), far below the EIA’s cost projections for new coal and gas-fired units, with LCOEs of $95/MWh and $75/MWh respectively.

The reactor completed the first of three phases of Canadian Nuclear Safety Commission’s (CNSC) pre-licensing vendor design review (VDR) in May, a process to verify how acceptable a proposed reactor design is against Canadian regulatory requirements.

In March, Moltex was granted $50.5 million in funding from Canada’s Strategic Innovation Fund and Atlantic Canada Opportunities Agency to advance the technology.

The company has entered into collaboration agreements with Ontario Power Generation’s Center for Canadian Nuclear Sustainability and New Brunswick Power and hopes to leverage Canada’s interest in developing small modular reactors (SMR), its nuclear power supply chain, and stockpiles of Canada Deuterium Uranium (CANDU) waste to start up its power plant.

Moltex Energy plans to build the first 300 MW SSR-W and WATSS facility in Saint John, New Brunswick by the early 2030s.

For all the advances into the Canadian market, the project has not been without controversy.

In May, a group or U.S. non-proliferation experts and former government officials and advisors wrote an open letter to Canadian Prime Minister Justin Trudeau to voice their worries about the government’s financial support for Moltex.

“Our main concern is that, by backing spent-fuel reprocessing and plutonium extraction, the government of Canada will undermine the global nuclear weapons nonproliferation regime that Canada has done so much to strengthen,” they said in the letter.

Moltex responded that, while conventional SNF reprocessing could have proliferation issues, their WATSS process would bypass these problems.

“The authors quite rightly express concerns around the risks of conventional reprocessing programs which can lead to weapons usable materials. This process is complex and very expensive, and would not be acceptable in Canada, nor would it make economic sense,” Moltex said in a response.

“The authors are not aware of our WATSS process as only high-level details are made public. It has been designed without the ability to produce weapons grade material,” it said.

By Paul Day