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 particles encased in a tungsten matrix. To prevent excessive fuel loss from reaction with the hot hydrogen gas passing through the cooling channels, both the internal surfaces of the cooling channels and the exterior of the fuel element must be clad with a hydrogen compatible material such as tungsten. To reduce the potential for uranium hydride formation that can lead to grain boundary separation and cracking, the diffusion of hydrogen into the cermet must be minimized. Therefore, fine-grained tungsten claddings are needed. Recently, advanced electrochemical processing techniques (EL-Form?) have been developed that enable the tailoring of refractory metal microstructures through process parameter manipulation and/or alloy additions. Therefore, these innovative electrochemical forming techniques will be used to produce fine-grained, hermetic tungsten claddings for both the internal and external surfaces of cermet based nuclear fuel elements.