Energy Security with Advanced High Temperature Reactors

by Gordy Slack


Per Peterson’s designs would take the excess heat produced by reactors and put it to use converting nearby domestic raw materials like tar sands into liquid fuel.

Three of America’s biggest problems may be addressed by one of the country’s most controversial technologies: nuclear power. Climate-altering carbon emissions, the politically destabilizing dependence on foreign oil, and an ever-increasing need for electricity are tangled together in a tight knot known as the energy crisis. Per Peterson, UC Berkeley Professor of Nuclear Engineering thinks the smaller, hotter, safer, and more versatile nuclear power plants he is developing may be able to loosen that knot, and perhaps begin to tease the strands apart.

The popularity of nuclear power took a nosedive in the US two decades ago with accidents at Three Mile Island and Chernobyl plants. But several things have changed since then, causing even many environmentalists to embrace nuclear power, notes Peterson. One huge difference is the rise of human-caused climate change as perhaps the world’s most pressing environmental problem. Nuclear power is one of the most promising technologies on the horizon that could replace the carbon-intensive energy sources now fueling that crisis.


Per Petersen, UC Berkeley Professor of Nuclear Engineering.

Peterson’s designs would place new Advanced High-Temperature Reactors (AHTRs) near chemical facilities and refineries that would employ the “process heat” discarded by existing nuclear plants. Instead of cooling the plant by releasing that heat into the atmosphere or water, the heat could be put to use converting various raw materials into liquid fuels. This could aid the process of converting corn into ethanol, for example, which consumes such large amounts of natural gas so that its environmental benefits are heavily clouded by the environmental costs. By using the process steam (steam created as a byproduct) from nuclear plants instead of burning natural gas, says Peterson, we could cut the carbon intensity of manufacturing conventional ethanol almost in half.

“Using nuclear process heat and hydrogen, we can convert tar sand, coal, and even bio-mass into transportation fuels with negligible emission of carbon,” he says. “All the carbon in these resources ends up in the fuel that goes into the vehicles.”

The process heat from AHTRs would also make the conversion of tar sand into liquid fuel both economical and relatively clean. Opening up North America’s vast tar sand fields (Canada’s fields “dwarf the oil fields of Saudi Arabia,” says Peterson) could loosen America’s dependency on foreign oil.

The small-footprint AHTRs would be cooled with liquid fluoride salts, which have outstanding heat transport properties, says Peterson. The new cooling method would allow the plants to run at much higher temperatures than today’s plants, which are generally cooled with water. In addition, because they are much smaller than traditional plants, AHTRs can be located adjacent to chemical facilities and to sources of natural materials that could be converted into liquid fuels. The valuable steam heat generated by the nuclear reactors is hard to transport long distances, as are the heavy raw materials. But unlike today’s huge reactors, the new plants themselves are small and versatile enough to be built near the material sites.


Finally, the smaller, lower-pressure-but-hotter plants are safer than their predecessors, Peterson says. The most vulnerable parts of conventional nuclear power plants are their elaborate cooling systems, which employ pumps, emergency diesel generators, and piping that transfers fluids out to some heat sink such as the ocean. If these cooling systems either malfunction or are the targets of sabotage, a plant can overheat, causing a catastrophic meltdown. The efficiency of the AHTR’s liquid coolants require far less elaborate and vulnerable equipment and thus make much smaller, more intrinsically secure targets, says Peterson.

“There is much less to attack and less that can go wrong with these systems,” says Peterson. “You do not need a large security force to protect them.”


The new generation of reactors would be cooled with liquid fluoride salts, which have outstanding heat transport properties and would allow for much simpler, safer, and more efficient cooling systems than today’s nuclear plants.

The new liquid-cooled plants, Peterson says, “are 10-to-100-times safer than the older light-water-cooled designs.” The AHTRs would also operate at atmospheric pressure, which boosts their safety. And the new plants would employ structural engineering innovations such as seismic base isolation, which allows the building to remain nearly stationary even when the ground moves underneath due to an earthquake.

Peterson believes the new designs could be commercially available in 12 to 20 years. He suspects that as the country takes to heart its need for new clean, safe sources of power and fuel, it will grow eager to embrace new technologies like the AHTR. He imagines a day when zero-emission electric cars will run off of carbon-free nuclear generated power, and airplanes will burn liquid fuel made from tar sands, coal, and bio mass that are created using excess heat from the same nuclear power plants that energize America’s cities and towns.