Experimental research on thermal transient flow characteristics of control rod hydraulic drive system

As a new internal control rod drive technology, control rod hydraulic drive system (CRHDS) shortens the control rod driving line and prevents control rod ejection accident. The transient flow experiments of CRHDS had been carried out under different working conditions. The mechanisms in the pressurization and depressurization processes of CRHDS were revealed. The characteristic parameters were extracted based on the experimental results, and the variation rules with major CRHDS operation parameters such as driving pressure and fluid temperature were summarized and analyzed. The results show that the pressurization process contains two water hammer processes, and the depressurization process contains one water hammer process. With the increase of driving pressure, the pressurization inflection point time decreases gradually, while the stable pressure and water hammer pressure peaks increase. The depressurization inflection point time changes a little, and the water hammer pressure valley value decreases. With the increase of fluid temperature, the pressurization inflection point time, water hammer pressure peaks and depressurization inflection point time all decrease gradually, and the water hammer pressure valley value increases. The research results can provide guidance for the design and the operation parameters optimization of the control rod hydraulic drive system.