The broader impact/commercial potential of this Small Business Innovation Research (SBIR) Phase I project is to enable safer and more economical nuclear power. This project will help increase the safety of nuclear power plants by reducing radiation damage to reactor components and reducing radiation exposure to power plant workers and personnel. In addition, it will reduce overall plant life cycle costs by reducing the cost of spent fuel management and decommissioning. By these means, this project will support the public benefit from continued and expanded use of nuclear power as a clean energy source. This Small Business Innovation Research (SBIR) Phase I project goal is to reduce the thermal expansion properties of a lightweight, high-temperature neutron shielding material. The key value proposition provided by this material over existing products is the unique increase in the operating temperature without producing a notable increase in weight or reduction in neutron stopping power. However, to enable its practical use, the material must be further adapted to reduce the coefficient of thermal expansion to meet reactor design requirements. With success, the proposed project will overcome the technical hurdle of reducing the coefficient of thermal expansion without altering other key material properties such as neutron stopping power, radiation resistance, density, and maximum operating temperature. Three approaches applied separately and in combination, if necessary, will be explored for reducing the coefficient of thermal expansion. These strategies may also be applicable for reducing the coefficient of thermal expansion in other neutron shielding materials with design limitations. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.