The Performance Analysis of a Reactor Coolant Pump Hydro-Static Seal in Different Operating Conditions by Reynolds Equations

Abstract

The reactor coolant pump is the key equipment of the first loop in nuclear power plant, and the shaft seal is the most important component. The reliability of the shaft seal under various operating conditions directly affects the safe operation of the reactor coolant pump and the plant. At present, the large shaft diameter No.1 shaft seal used in the nuclear power plant is mostly in a hydro-static type with single taper. In order to analyze the No. 1 seal performance which is impacted by the pressure, temperature and speed of the reactor coolant pump, the simplified Reynolds equations is used to calculate the fluid domain of No. 1 seal by the numerical method. The analysis obtains the No. 1 seal surface pressure distribution, then the No. 1 sealing film thickness, leakage rate and other performance parameters under different pressure, temperature and speed conditions are analyzed and results obtained. In the analysis, the deformation of the sealing surface influenced by the temperature is not considered, but the high temperature impact under SBO condition is analyzed and predicted. The influence of speed variation with the increase of centrifugal force in the calculation is considered. The results show that the leakage increases with the increase of pressure, and is more sensitive under low pressure. The leakage quantity increases with the increase of temperature, below 100°C, the leakage is basically in near linear change trend, but in the high temperature about 300°C in SBO condition, the leakage rate increases obviously. For the large diameter hydro-static seal, due to the large rotating radius, the circumferential velocity is relatively high; under the action of centrifugal force the leakage rate is lower when the speed is higher. The calculation results of hydro-static pressure under different pressure level are compared with the experimental results, the calculation results of the trend is consistent with the experimental result, and when the pressure becomes larger, the calculation results and the experimental results are more different. The results also show that although the direct use of the Reynolds equation cannot reflect the interaction influence of fluid, solid and heat transfer, but compared with the test results, the trend of the calculation and the test is the same. In conclusion, the calculation method by Reynolds equations can be used in the guide of reactor coolant pumps No.1 seal design, but the design detailed should be corrected by the real test data.