Dynamic modeling and simulation of the GAMA-AHR

The GAMA-AHR is an aqueous fueled nuclear reactor designed to produce 2000 six-day Ci per week of ⁹⁹Mo at thermal power of 200 kW. In this study, the dynamic behavior of the GAMA-AHR was demonstrated. A point reactor dynamics model consisting of point kinetics, heat balance, and reactivity feedback equations was developed to represent the primary system of the GAMA-AHR This reactor dynamics model was implemented in C++, and solved numerically with adaptive Runge Kutta method. Numerical simulation to show the reactor's steady state and transient behavior is reported in this paper. The transient conditions were simulated for the detection of perturbations caused by a reactivity contribution from the reactivity control system and a reduction in the secondary cooling system's performance. The model was validated by steady-state simulation at 100 power, and the results agreed well with previous research and therefore demonstrated its suitability for predicting the reactor's dynamic behavior. The simulation results showed that reactor power decreased with increasing temperature and decreasing heat transfer capability. It was able to safely operate (without fuel boiling) at 90 reduced heat transfer capability and power lower than 100 kWh. The simulation results also showed that reactor power can be controlled by adjusting the control rod insertion or the fuel level and the reactor can be independently shut down by the full insertion of the control rod or by full draining of fuel into the fuel drain tank. Thus, the temperature reactivity feedback characteristic and reactivity control systems ensures the inherent safety of the GAMA-AHR. © 2025 Elsevier B.V.