Part 2 of 3 Parts (Please read Part 1 first)
Terrani and his team at ONRL recently finalized the preliminary design for the 3D-printed core at the center of their Transformational Challenge Reactor, or TCR. Most of the reactor will be constructed from conventional components. Only the core will be entirely 3D printed of silicon carbide which is an extremely rugged material that is almost impossible to melt. The core is the operational heart of a nuclear fission reactor. It holds the uranium and/or plutonium fuel assemblies where nuclear fission occurs. The new core at ORNL is less than eighteen inches tall. The reactor that contains it will only be a little bigger than a keg of beer. Terrani says that when their first prototype comes online in 2023, it will generate as much as three megawatts of energy which would be enough to supply the power needs of about a thousand average homes.
The ORNL TCR reactor is an advanced gas-cooled reactor design that utilizes hydrogen as a coolant. Most operational nuclear fission power reactors in the U.S. today utilize water as a coolant. Gas-cooled reactor are very fuel efficient because of the high temperatures that they operate at. The TCR will operate about at one thousand two hundred degrees Fahrenheit. Terrani says that the 3D printed core of the TCR will make the efficiency even higher. Traditional machining techniques now employed in the manufacture of a nuclear fission reactor core constraint the design of the core. There is a complex network of cooling channels in the TCR core that are too small and complex for any conventional machining techniques. Because of the capabilities of 3D printing, engineers can now construct components that would have been impossible before.
Terrani says, “We’re no longer stuck with boring geometries. Instead of an array of things that all look the same, you can change the design across the core and get your system to respond to the environment.”
3D printing will also permit nuclear engineers to keep better track of what is happening inside the core once the reactor is operational. In conventional nuclear fission reactors, the behavior inside of the core has to be monitored from the outside. The new designs made possible by 3D printing will allow the engineers to embed sensors in the core during the printing process that will provide information about conditions in the core after it is in operation.
3D printing will also give nuclear engineers greater control over the manufacturing process. Individual parts of the TCR core can be printed in under twenty-four hours. The entire core can be completely printed in a few weeks. While a part is being printed, a machine vision algorithm is acquiring data from infrared cameras and other types of sensors that will help it determine whether or not any defects occurred during the printing process.
Terrani says that the next step in his project will be the real nuclear industry game changer. When a component for a nuclear fission reactor is manufactured in the conventional way, it is subjected to an expensive and slow certification process before it can be used. Terrani cites the example of a bolt that cost a few cents to make but was sold for twenty thousand dollars because it had been certified for nuclear systems.
Please read Part 3 next