Integrated Multi-Physics and Advanced Diagnostics for NTR Development

Historically, designing a nuclear thermal rocket engine and determining fuel performance has been a refractory and anfractuous process. Typically, fuel forms would be developed and tested in separate tests of mechanical, radiation and thermal testing, and, in the NERVA program, the fuel elements were assembled in a rocket engine and tested. The fuel did not perform to expectations, and the engine needed to be disassembled, the fuel examined and fixed needed to be determined; then the process would repeat itself. In the Space Nuclear Thermal Propulsion Program, individual fuel elements were tested, but they could not be tested to full power density due to test reactor limitations. Nevertheless, this was a far less expensive approach that full engine testing to determine whether the fuel elements in particular would withstand the rigors of the NRE (Nuclear Rocket Engine) mission. This proposal outline how LPS and its team members plan to integrate the latest in multi-physics model to simulate a fuel element based on a particular NRE design built up from designer parameters. The multi-physics modules can determine fuel integrity and fission product retention as a function of temperature and operating times, determine micro-structure evolution including cracking and grain growth. The fuel element parameters are derived from high level NRE requirements via the integration of the IROC (Integrated Rocket Optimization Code), linked with PHOENIX, a program linking multi-physics modules through MOOSE (Multi-physics Object-Oriented Simulation Environment) Ultimately, detailed safety related information including results of impact analyses through extensive hydro-codes such as PRONTO/SPH and radiation transport codes such as MACCS2. This enables safety to be integrated in from the very beginning of the design process resulting in a much more optimized safety based nuclear rocket engine.