Study on the decelerating mechanism of the new control rod hydraulic decelerator for the CRHDS based on numerical simulation and experiment

Highlights: • CRHDS is a new type of built-in control rod drive technology and CRHD is the key component of it. • The theoretical model of the rod drop process was developed and verified by tests. • The full scale rod drop tests were carried out to get the new CRHD dynamic data. • The theoretical model was applied to analyze the key parameter influence on CRHD dynamic characteristics. - Abstract: Control rod hydraulic drive system is a new type of internal control rod drive technology for the nuclear heating reactor. Control rod hydraulic decelerator is one of the major components of the CRHDS. The CRHD performs the rod drop speed control function to reduce the rod drop impact force and prevent the control rod cruciform blade from being deformed or damaged. The composition and working principle of the new CRHD are analyzed. The theoretical model of the rod drop dynamic process was developed and the flow field analysis of the CRHD flow channels was carried out to close the model. The full scale rod scram tests have been conducted to get the rod drop dynamic data. The theoretical results agree well with the experimental results, which verify its correctness. The rod drop theoretical model was then used to analyze the influence of the reactor coolant operating temperature and the hydraulic deceleration cylinder sidewall flow area on the dynamic characteristics of the new CRHD. The research results lay the base for the design and further optimization of the CRHD.