Study on the start-up characteristics of a 100kWe-level nuclear silent heat pipe cooled reactor based on cascaded control

Heat pipe cooled reactors are a recent hotspot of research in energy systems due to their high energy density, simple structure, and inherent safety. These reactors, operating at near 1000K, require high-temperature heat pipes with alkali metals, which freeze under cold conditions, posing start-up challenges. This work proposes a cascaded control method for heat pipe cooled reactors, integrating neutron physics and thermal-hydraulic models into a coupled control framework. The heat pipe model was improved with a wick structure flow model, achieving a relative error below 9.76 %. The framework was used to analyze the start-up characteristics of a 100kWe-level reactor. Simulations indicate that the start-up process involves two power peaks and depends heavily on the heat pipes. Activating the energy conversion system quickly is crucial, overcoming an initial control dead zone. A constant start-up rate of 0.01 % FP/s extends the start-up time to 12,000 s. However, a variable rate strategy, shifting from 0.01 % to 0.05 % FP/s, reduces this to 5500 s. The steady-state velocity in the central heat pipe wick is approximately 0.0155 m/s with a pressure drop of about 9140 Pa, displaying a trapezoidal velocity profile.