Fine Grained Tungsten Claddings for Cermet Based NTP Systems

In October 2011, NASA initiated the Nuclear Cryogenic Propulsion Stage (NCPS) program to evaluate the feasibility and affordability of Nuclear Thermal Propulsion (NTP). A critical aspect of the program is to develop a robust, stable nuclear fuel. One of the nuclear fuel configurations currently being evaluated is a cermet-based material comprised of uranium dioxide (UO2) particles encased in a tungsten matrix (W). To prevent excessive fuel loss from reaction with the hot hydrogen gas and uranium hydride formation, dense, fine-grained tungsten claddings are needed. Recently, advanced additive manufacturing techniques (EL-Form and Vacuum Plasma Spray Forming) have been developed that enable the deposition of coatings and near-net-shape refractory metal components with high density and tailored microstructures. The Phase I investigation produced fine-grained W claddings using EL-Form and VPS processing techniques. Testing showed the W claddings were well bonded to surrogate nuclear fuel element materials, and the W claddings were vacuum tight. During Phase II, the techniques developed during Phase I will be optimized, and W claddings on full size cermet fuel elements will be developed and characterized. Subscale and full-size test articles will be produced and delivered to NASA-MSFC for hot hydrogen testing in the Compact Fuel Element Environment Test (CFEET) facility and the Nuclear Thermal Rocket Element Environment Simulator (NTREES).