Research on Key Technology of Thermal Hydraulic Experiment of Pressurized Water Reactor Steam Generator

Abstract

Both the new PWR steam generator and thermal hydraulic analysis software need to carry out experiment to verify the performance before engineering application. Onedimensional and threedimensional thermal hydraulic software of steam generator were used to obtain the distribution of key parameters, such as temperature, void fraction, pressure drop of support plate, etc., and optimize the design of the test simulator and the arrangement of measuring points. Following the simulation criterion of equal height, equal physical properties, and similar resistance, the steam generator simulator was designed, and the design of downcomer tube with full bore ball valve was used to realize the precise control and measurement of the circulating rate. The circulating rate was measured and calculated by the flow method and the thermodynamic method, and the relative deviation between the two methods is less than ±5%. The armored thermocouple sealing structure was designed to pass through the two layers of pressure boundaries to obtain the primary side temperature distribution along the heat transfer tube. The secondary side temperature distribution of steam generator and the height of the boiling start point were obtained. The guided wave radar liquid level gauge and the liquid level measurement by differential pressure were used to measure the water level of the steam generator with good followup, and the relative deviations of the two methods under steadystate and transient conditions do not exceed ±15%. The point, line and volume void fraction of the secondary side of steam generator were obtained by the optical fiber probe, gammaray method and differential pressure methods respectively. The relative deviation between the threedimensional calculation and test measurement results in the region of high void fraction does not exceed ±10%. For the central area of the tube bundle, the measurement value of the optical fiber probe is the highest. For the tube gallery area, the measurement values of the three methods are close, and reasons for the deviation of the measurement results among the three methods were analyzed. Considering that the pressure difference method needs to eliminate the error caused by frictional pressure drop, it is recommended to use the ray method to measure void fraction. The steam wetness (<002%) under different power loads of a new steam generator was measured by the tracer element method based on steam condensation at full flow rate. The comprehensive performance of various new steam generators were successfully assessed by applying the abovementioned key technologies on the 30 MW steam generator comprehensive performance test platform of Research Institute of Nuclear Power Operation.

Keywords

• steam generator
• thermal hydraulics
• void fraction
• gamma-ray
• steam wetness