United States Scientists Tender

Its a new type of nuclear reactor core.And the materials that will make it up are novel products of Oak Ridge National Laboratorys advanced materials and manufacturing technologies.With a tight timeline researchers are tasked with ensuring the novel materials can stand up to the intense heat pressure and neutron bombardment inside a reactor core. How will they make sure these materials can do everything they need to do as crucial parts of the Transformational Challenge ReactorBy testing them in an experimental reactor built in the 1960s.The research team will irradiate three components in ORNLs High Flux Isotope Reactor 3D-printed silicon carbide 3D-printed 316L stainless steel and yttrium hydride the building blocks of the gas-cooled reactor core. Together these materials will drive what ORNL envisions as the reactor of the future.This project aims to demonstrate how advanced manufacturing can be applied to nuclear power by combining 3D-printed materials and an innovative reactor design and then making it go critical in less than five years said Kory Linton of ORNLs Nuclear Fuels and Materials Group.HFIR is distinctly suited to aiding with this task he said.A lot of the test reactors that are available would not lend themselves to an agile project like this with a tight timeline Linton said. ORNL is uniquely positioned for irradiation testing in support of the Transformational Challenge Reactor because HFIR is such a powerful reactor capable of fast-turnaround small standardized experiments.Within a year we can have materials in HFIR. Within another year we can have data. For the irradiated materials community thats a very quick turnaround time.The fuelThe fuel matrix for the Transformational Challenge Reactor will be made of silicon carbide a chemical compound of carbon and silicon that produces a high-quality durable ceramic thats also an excellent conductor of heat.Silicon carbides durability and versatility have already ensured its usefulness in numerous technical applications including nuclear projects and a lot of data exist on its performance. But ORNLs silicon carbide or SiC is different because its 3D printed.Using a type of additive manufacturing in which powder is layered with a binding agent to form a solid matrix SiC can be printed in unusual shapes and sizes.You can put it into geometries that historically you would not even consider Linton said.Linton and his team already have completed irradiating thin discs of 3D-printed SiC at different temperatures. A holder containing these discs is placed in a sealed capsule with very tight design tolerances that provide small gas gaps to manage the temperature during irradiation. The capsule is then inserted into the center of HFIR for irradiation.After irradiation at target temperatures ranging from 400 to 900 degrees Celsius the discs are being checked for strength and swelling and analyzed to determine how quickly the 3D-printed SiC transfers heat. Those parameters will be used to inform TCRs core design ensuring the most relevant materials property data are captured.The core structure3D-printed 316L-grade austenitic stainless steel an alloy shown to withstand high temperatures for long periods without corrosion will be used for the lattice structure inside TCRs core. This structure will hold the fuel rods in place. The stainless steel will also be used for some bristles and springs.ORNLs 316L stainless steel is made by printing layers of powder that are fused together as they are created. It has undergone neutron irradiation along with samples of traditionally wrought 316L to compare how they perform in temperatures ranging from 300 to 600 degrees Celsius and at varying doses of radiation.But printing it layer by layer could also produce variations in density chemistry porosity and other characteristics Linton said. Thats why when he cuts a sample for testing hes very careful to note its exact location within the original printed geometry.Learning which printing patterns produce the most desirable material will in theory allow researchers to teach a computer the ideal traits. Then through artificial intelligence it will compute the best methods for printing them.Each print provides a rich amount of data that can be used to continually improve the printing process he said.If additively manufactured 316L performs as well as or better than wrought steel Linton said it will save time and money in fabrication of parts and it will also allow for additional design flexibility.The promise of advanced manufacturing is that youre going from a slower and less-flexible environment to where you can come up with a design prototype it see how it performs make adjustments and try again Linton said. Youre moving through and testing ideas very quickly.The moderatorYttrium hydride a compound of a transition metal and hydrogen will be used in TCRs nuclear core as a moderator which is the substance that slows down neutrons during fission.The idea that YHx could be an effective core moderator dates back to early gas-cooled reactor designs but data on the compound are scarce as it was not widely commercially available in the past.Now that yttrium is more readily available YHx has been selected for TCR because of its high hydrogen atom density and exceptional ability to withstand high temperatures without changing its chemical composition.TCR is a ripe opportunity to go back to a material that the market has changed on Linton said.Capsules of YHx will be irradiated in HFIR at 600 and 900 degrees Celsius at three different radiation doses. In addition specimens will contain varying amounts of hydrogen so that researchers can see if that makes a difference in heat capacity durability expansion and how quickly it transfers heat.