PNNL is developing a new approach for creating alloys

Researchers at Pacific Northwest National Laboratory are designing new types of metallic alloys that can better withstand the extreme conditions of heat, radiation, and mechanical stress inside nuclear reactors. Led by materials scientist and principal investigator Osman El Atwani, the team uses an approach termed robust alloy design (RAD) that has been described in the journal Materials & Design.

El Atwani and his colleagues are using their eight-step computational RAD method to systematically identify, evaluate, and create unique combinations of elements designed to meet the environmental and manufacturing requirements of new reactors. They developed the method to help narrow the search for the most suitable alloys and to save time and resources by avoiding the fabrication and testing of alloys that will ultimately prove unsuitable.

RAD screening and scores: The RAD approach-which is essentially an advanced type of computational screening of potential element combinations-led to the initial identification of 724 potential alloy compositions. Further evaluation then narrowed the number of candidates for experimental validation in the laboratory.

That additional evaluation involved the assignment of RAD scores based on a holistic scoring framework for the most promising candidates. According to PNNL, a RAD score "combines multiple nuclear-relevant criteria into a single score for comparing and downselecting alloy candidates prior to experimental evaluation."

This evaluation process led the researchers to select an alloy that they call V555 to use for validation of their RAD approach in the laboratory. They fabricated the V555 alloy and then examined the details of its structure and mechanical properties through a series of tests.

The initial tests, which were conducted at room temperature, estimated that V555 has a yield strength (the maximum amount of stress that the alloy can withstand before it starts to permanently warp in shape) of about 500 to 600 megapascals, offering an encouraging estimate of its mechanical properties under laboratory conditions.

The next step in the validation process, as noted by the researchers, is to evaluate the properties and responses of V555 under conditions of temperature, radiation, and pressure that could be seen in reactors. Beyond the V555 tests, El Atwani's team is also planning to test other alloy candidates that have been identified through the RAD method.

Practical applications: The PNNL alloy research, which is being funded by the Department of Energy Office of Nuclear Energy's Innovative Nuclear Materials Program, ultimately may find practical applications in the development and deployment of advanced nuclear reactors. El Atwani said, "The work has developed into a pathway for the nuclear materials community to explore and evaluate a broader range of materials for future nuclear systems."