194: Small scale nuclear reactors


95% of the hydrogen produced in the world today comes directly from fossil fuels, with the biggest supply coming from steam methane reforming, where a mixture of steam and methane gas is put under high pressure while in contact with a nickel catalyst, to produce hydrogen, carbon monoxide and a small amount of carbon dioxide.


Modular nuclear reactors.

Working at the Idaho National Laboratory, a team led by Dr José Reyes, an internationally recognized expert on passive safety system design, testing and operations for nuclear power plants, has developed a passively-cooled small nuclear reactor to produce hydrogen.

Water is heated to a temperature of 300 °C (572 °F) by the reactor and then the temperature of the steam is increased to 860 °C (1,580 °F) using two percent (around 1.8 MW) of the reactor’s electrical output.

This is then put through a high-temperature steam electrolysis system that works like a fuel cell in reverse. By pumping thermal energy into the system, the water breaks up into hydrogen and oxygen rather than combining the gases into water to get out energy.

Encouraged that a single small Nuclear Power Module (NPM) could economically produce almost 50 tonnes of hydrogen fuel per day, Reyes and Paul G. Lorenzini founded NuScale Power in Tigard, Oregon to take the solution from laboratory to working plant.

Each NuScale reactor vessel would measure 9 feet (2.7 m) in diameter and 65 feet (20 m) tall, weighing 650 short tons (590 metric tons). The modules would be pre-fabricated, delivered by railcar, barge or special trucks and assembled on-site.

The units were designed to produce 60 megawatts of electricity each and require refueling with standard 4.95 percent enriched uranium-235 fuel every two years.

In addition, a single NPM would reduce carbon dioxide emissions by 168,000 tonnes per year.

NuScale says that its nuclear modules are designed to scale up by adding as many of the factory-built nuclear reactors as needed at a site. One, five, a dozen, or more such reactors could be installed on a site smaller than a conventional power station and located almost anywhere.

In August 2020, the NRC issued a final safety evaluation report for NuScale’s small modular reactor design, certifying the design as having met the NRC’s safety requirements. NuScale plans to apply for a standard design approval of a 60-megawatt-per-module version of the design in 2022, which if accepted will allow the company to pursue its first reactor deployment in the mid-2020s.

Discover Solution 195: Towing icebergs

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