ANS Winter Meeting: Universities to host a new generation of advanced reactors

December 13, 2021, 12:00PMNuclear News

A screen shot from the “Research Reactors in Support of Advanced Reactor R&D” session at the 2021 ANS Winter Meeting and Technology Expo.

First-of-a-kind research reactors, demo reactors, and research facilities are being developed and sited on university campuses to support the broader deployment of advanced reactors. At the 2021 ANS Winter Meeting and Technology Expo, during a December 2 panel session titled “Research Reactors in Support of Advanced Reactor R&D,” several of these planned projects were discussed in detail—including a molten salt reactor in Texas and a high-temperature gas–cooled reactor in Illinois.

The session was sponsored by the Reactor Physics Division and organized and chaired by Pavel Tsvetkov, of Texas A&M University. A video of the session is available to registered Winter Meeting attendees.

The plan to site a molten salt research reactor on the campus of Abilene Christian University (ACU) in Texas was represented by Douglass Robison, of Natura Resources, a for-profit company that provided the funding needed to jumpstart the Nuclear Energy eXperimental Testing Research Alliance (NEXTRA), and professors from each of the four universities that are part of the consortium: Tsvetkov, of Texas A&M; Rusty Towell, of ACU; Steve Biegalski, of the Georgia Institute of Technology; and Derek Haas, of the University of Texas at Austin.

Robison, a self-described “third-generation oil and gas guy,” said he was inspired to direct funds to molten salt reactor research after watching Towell deliver a talk on the subject at ACU in 2017. “I tell people I'm recycling oil and gas profits into nuclear,” he quipped.

One of the first questions faced was, how are we going to have a commercial entity fund a research reactor? I don't think that had ever been done before,” Robison said. “But the Department of Energy was excited about that whole scenario, so we took about a year to form what is now referred to as NEXTRA, a research alliance of the four universities involved in this project.”

ACU plans to have a molten fluoride salt reactor featuring a dissolved, liquid fuel in its NEXT Lab by 2025. The design of the molten salt research reactor (MSRR), Towell explained, is very similar to the Molten Salt Reactor Experiment (MSRE), built and operated at Oak Ridge National Laboratory in the 1960s, with some notable differences. The MSRR, a 1-MWt reactor, will be fueled with high-assay low-enriched uranium instead of high-enriched uranium, will have a lower power and power density than the MSRE, and will not require external cooling water.

“A lot of what we know about the MSRE applies to MSRR,” Towell said. “We are trying to simplify it. We're trying to make it as easy as possible for the Nuclear Regulatory Commission to license something they've never licensed before.”

Towell said the NEXTRA consortium is seeking “all the things that we wish we could find in some old MSRE report. . . . That's the reason to build this reactor. Clearly the question is not, will the reactor go critical? or does the physics work? That was all demonstrated in the 1960s at Oak Ridge. The reason to do this today is to license it and collect data from it so that we can make engineering improvements. . . . Anytime we can reduce the uncertainties in terms of design makes the business case much more straightforward, so that this can be deployable technology and not something that just stays in the lab.”

UIUC plans a gas-cooled microreactor: Caleb Brooks, of the University of Illinois at Urbana-Champaign (UIUC), described the university’s plans to site a Micro-Modular Reactor (MMR) from Ultra Safe Nuclear Corporation next to the university’s Abbott power plant where it will provide both electricity and steam to meet the campus’s substantial power needs.

“It's great to build another reactor in a desert, and I don't mean that in a negative way at all,” Brooks said, adding that in a university setting, “we can demonstrate their safety and put them down where people can witness, experience, and see the benefits of nuclear technology.”

UIUC had operated a TRIGA reactor for 38 years, but it was shut down in 1998 and the site returned to greenfield status in 2012. Now, the university’s Nuclear, Plasma, and Radiological Engineering Department wants to host something quite different.

“We aren't planning to play with neutrons and gamma rays,” Brooks said. “That hasn't been our focus here. We're interested in the research that's necessary to see a distributed energy source like a microreactor become widely adoptable and widely economic. So, we're looking at operations, instrumentation and controls, and the enabling and synergistic technologies that are necessary. . . . We do plan to integrate our unit with our existing power production infrastructure for the campus to distribute electricity, district heat, do some hydrogen production demonstration and maybe other high-value product processes.”

The 5–10 MWe, 15–30 MWt helium-cooled MMR is designed with an integrated molten salt loop that can be used for energy storage in a commercial deployment. Brooks explained that the molten salt loop would help decouple the operation of the reactor for research and training from the usability of the energy to provide steam to the Abbott power plant.

In May 2021, UIUC submitted a letter of intent to the NRC. The university’s schedule anticipates a construction permit in 2024, an operating license in 2026, and operations in 2027.

“I am confident about the schedule,” Brooks said, in response to a question from the audience. “It is ambitious, and I think we need to be ambitious.”

Brooks added, “For microreactors and for a lot of advanced reactors, the Section 104c license pathway through the university research test reactor precedent provides a very clear path for licensure compared to a first commercial deployment. You also need fuel, and fuel is a big problem for advanced nuclear on the commercial side, but universities have access to fuel through the research reactor infrastructure program where you don't have the same bottleneck. So, I think that university demonstration can be done quicker than commercial deployment.”

MIT investigates salt reactors: Charles Forsberg, of the Massachusetts Institute of Technology, described the work being performed under a three-year DOE Integrated Research Project in MIT’s research reactor and at North Carolina State University to understand molten salts in irradiation conditions.

“There are many reactors, including fusion machines, that use clean fluoride salts,” Forsberg said. “There is a set of reactors, such as [ACU’s MSRR], that uses fuel dissolved in the fluoride salt, and there's a third category of molten salt reactors that use chloride salts dissolved in the fuel. There are lots of different concepts that have a lot of commonalities. We need to understand the salts under irradiated conditions, and that's what's happening at MIT and at North Carolina State University.”

MIT is building a “general purpose” instrumented flowing salt loop, first with a non-radioactive loop for education and testing, and then with a “hot” neutron irradiation loop with a fluoride-based salt in the reactor. The hot loop is to come on line in 2022, according to Forsberg.

Motivations for installing the loop include having strong interactions with industry and national laboratories; providing experimental data on tritium and fission product retention, diffusion, and transport; and providing an experimental testbed for chemistry control, salt cleanup, and tritium control. Part of the same IRP project will involve real-time testing of molten salt off-gas in NCSU’s Pulstar reactor, Forsberg said, while a separate project at MIT is gathering critical irradiation data to enable the modeling of MSRs through digital twinning.

Fast neutron source at UTK

Wes Hines, of the University of Tennessee at Knoxville, described the Fast Neutron Source (FNS) nearing completion in UTK’s new nuclear engineering building that uses a neutron-generator–driven “highly flexible subcritical core to replicate the neutron spectrum of any fast reactor.”

The flexibility of the FNS is achieved by loading 6-inch by 6-inch square plates of different materials, including uranium and lead, into cassettes to generate a specific neutron spectrum. The half-inch-thick plates are loaded into 10-inch-long cassettes, described by Hines as “shoeboxes,” that hold a total of 20 plates. The cassettes can be reconfigured to suit the needs of different research projects.

UTK researchers have applied genetic algorithms to organize the plates to optimize both the high flux and the neutron spectrum. “We've been working on that for two or three years,” Hines said. “It's been the most exciting academic project that I've worked on in the 26 years that I've been at the university.”

While the FNS was initially planned to use high-assay low-enriched uranium, UTK researchers have decided to begin operations with natural uranium instead.

Collaborate and deliver: Session participants agreed that every project described has a role to play in supporting advanced reactor deployment.

“I always leave a conference very disappointed when all I hear is bickering about which project is more important,” Towell said. “I clearly think that all of these projects fill different niches. Whether it's a subcritical facility, existing reactors, or new reactors, I think they all have something to bring to the table, and I think we’re better when we're collaborating across all these efforts.”

Looking beyond the university community, Brooks added a note of urgency. “If advanced nuclear can't be done on budget and on time, we will lose the public on it,” he said. “If we don't capitalize on the alignments in D.C. and the windfall of funding for nuclear right now, I think enrollment numbers at the universities will drop drastically again. . . . This is the time that we need to go, and we need to deliver on the promise of advanced nuclear. I think we're running out of time.”