Development and preliminary verification of a transient analysis code PANES-Tran for Nuclear thermal propulsion

The Nuclear Thermal Propulsion (NTP) boasts advantages such as high specific impulse, substantial thrust, and extended operating time, giving it a clear edge in deep space exploration and orbital maneuvers. To fully harness the potential of NTP, transient analysis is crucial to ensure reliability, safety, and performance under various operational conditions. In this paper, a transient version of NTP analysis code PANES-Tran (Program for Analyzing Nuclear Engine Systems - Transient) was developed for the 110kN expander cycle particle bed reactor (PBR) nuclear thermal propulsion (NTP) system. The code is based on the one-dimensional thermal-hydraulics (TH) framework and its fixed-point iteration expressions, coupled with the point reactor kinetics (PK) model. Under the framework, a turbopump model incorporating characteristic curves was constructed, and a PBR fuel element model involving porous media and fuel particle heat transfer procedure was also established. The basic models and methods were preliminary verified using AMESim for fluid flow and heat transfer and, RELAP5 for PK/TH coupling scheme. Moreover, the integrated effect of PANES-Tran was also verified by the design parameters of the 110 kN PBR-NTP system. Subsequently, a transient process triggered by +0.2$ step reactivity introduction under rated conditions was studied, which indicated that the NTP system could stably transition to a new steady state with a thrust of 125 kN. This study could provide a powerful tool for subsequent research on transient characteristics and operation strategy for NTP systems.