Use of an ejector to reduce the time of air injection during testing of the containment system at nuclear power plants

Abstract

The containment system (CS) is the last barrier to the release of radioactive substances into the environment in the event of a nuclear accident. After each overload, this system is tested for its ability to perform its functions by determining the integral leakage, which should not exceed a certain value. The tests are performed at an overpressure in the CS of 0.72 kgcm–2, which is achieved by injecting air with a compressor. The paper considers the use of an ejector to accelerate the injection process, which has a positive effect on the technical and economic performance of a nuclear power plant (NPP) power unit by increasing the amount of electricity generated, which is very important today, when the NPPs provide the maximum share of electricity generated in the country. Previous studies have evaluated the use of an ejector for this purpose, but they did not consider the need to install filters on the intake air stream. In addition, they used numerical methods that generate an error. The present work uses a mathematical apparatus that provides a more accurate result. The obtained calculated compressor injection time coincides with the actual injection time for the Rivne NPP power units. The design of the ejector ensures the minimum injection time is determined. The optimal ejector module is equal to 8.6 (the ratio of the cross-sectional area of the cylindrical mixing chamber to the critical cross-sectional area of the working air nozzle). This reduces the injection time by 38.8%. The suction air must be free of dust and moisture. Suitable filters have a total aerodynamic resistance of 0.2 bar. Taking these air filters into account slightly reduces the efficiency of the ejector. The final time of air injection using the ejector is 2.56 h, which reduces the time of air injection for testing by 35.5%.