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.

NASA applications that would directly benefit from this technology include Nuclear Thermal Propulsion (NTP) and Nuclear Electric Propulsion (NEP). Initial NTP systems will have specific impulses roughly twice that of the best chemical systems, i.e., reduced propellant requirements and/or reduced trip time. The proposed Phase I and Phase II efforts would greatly assist NASA with achieving the goals of the NCPS project. Potential NASA missions include rapid robotic exploration missions throughout the solar system and piloted missions to Mars and other destinations such as near earth asteroids.

Commercial sectors that will benefit from this technology include medical, power generation, electronics, defense, aerospace, chemicals, and corrosion protection. Specific applications include protective coatings for gamma detectors, x-ray targets, valves, non-eroding throats and thrusters for propulsion, crucible/furnace components, and electrochromic glass.

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