Mini Nuclear Reactor to Solve the E-Truck Recharging Dilemma

First, the system is flexible; it adjusts as demand swings when trucks come and go — even as the reactor’s power output remains steady. When the rest stop is empty, the reactor produces power in the form of heat, which is transferred and stored in a separate tank of inert heat-transfer fluid. When trucks crowd the rest stop, the system taps that heated fluid to produce steam, generate electricity and recharge batteries. (To learn more about this, see ​“How this design transfers and stores heat” on the right.)

Second is the rest stop reactor’s safety-forward design; the team chose a special type of nuclear fuel that secures all radioactive material. The fuel is made of Tri-structural ISOtropic (TRISO) pellets, developed from 60 years of research at DOE National Laboratories. The pellets contain low-enriched uranium covered by layers of carbon and ceramics. Those protective layers ensure the reactor’s safety.

Third, the Argonne team aimed to keep the cost of the rest-stop reactor low — under $3,000 per kilowatt-hour for capital costs — by choosing proven, practical approaches. The team, for example, picked a thermal reactor design — the same type that powers all 95 nuclear plants in the U.S.— because of its 70-plus-year track record of safety and reliability. The system, said Kultgen, works at relatively low temperatures (about 700 degrees Fahrenheit) to reduce costs and promote rapid development.

The decision to go with a temperature lower than many advanced designs require came, in part, from Kultgen’s four years of managing Argonne’s Mechanisms Engineering Test Loop (METL) Facility. There, a team of engineers gauge the durability of equipment by dunking it in liquid sodium at 1,200 degrees Fahrenheit for months or years.

Sticking to lower temperatures may sacrifice efficiency for cost and safety, but Kultgen accepts that tradeoff.

“Cost is one of the biggest challenges to constructing and operating a facility to withstand these extreme temperatures,” he said.

Design within Reach
To design the system, the team turned to Nicolas Stauff, a principal nuclear engineer who had already designed microreactors for startup companies and the Department of Energy. Stauff used modeling software, including the laboratory’s award-winning System Analysis Module (SAM) Reactor Analysis Code, to pick the best reactor size, fuel amount and heat-transfer fluid type. With these tools, Stauff also designed the reactor core and simulated how the whole system would operate.

At that point, everything clicked. ​“We realized we could put this together,” Kultgen said. ​“The system could be standardized, mass produced on an assembly line and loaded on trucks to ship to installation sites across the country.”

The Road Ahead
The team has shown that the approach could fill a gap in infrastructure for electric long-haul, 18-wheel trucks. But they stress that much work remains.

“We plan to go much further in the analysis of this reactor,” said Stauff. Over the next year, he plans to examine the tradeoff between the reactor core’s size and its longevity, while exploring the reactor core’s behavior with tools that offer high-fidelity, multi-physics simulations.

Stauff is an expert user of these tools as he leads the microreactor area within the DOE Office of Nuclear Energy’s Nuclear Energy Advanced Modeling and Simulation (NEAMS) program.