Цифровая коррекция показаний измерительных каналов уровня жидких сред с областью нечувствительности датчиков на атомных электрических станциях

Abstract

The introduction and development of computerized digital systems in modern power engineering has led in Russia to a full modernization of domestically produced nuclear power plant measurement systems. In particular, digital methods for correcting the readings of hydrostatic level sensors have been widely put in use since 2013. The experience gained from putting them in use was generalized in the reference and organizational and methodological literature in 2017. However, the subsequent results of preoperational adjustments carried out at newly designed nuclear power units and at those under construction have shown that some issues still remain unresolved in this application field. In particular, there is a need is to develop digital methods for correcting the readings produced by channels measuring the level of liquid media in pressurized process tanks if there occurs a sensor dead zone. \nThe complexity of this problem is stemming from the fact that it is not possible to take the sensor dead zone into account by introducing a constant correction to the measurement channel readings in view of the technological process peculiarities. Thus, during the operation of nuclear power units, the water density in pressurized process tanks and vessels decreases from 980 to 590 kg/m3, and the vapor density increases from 0 to 100 kg/m3. Such changes give rise to complex thermal and physical interphase processes that occur under the conditions of large mass transfers of the vapor--water mixture. As a result, the sensor s dead zone boundary undergoes an essential change in the tank longitudinal section depending on the current values of the working fluid thermal and physical characteristics. \nTo solve this problem, digital methods for online correction of measured level readings are proposed that take into account changes in the two-phase working medium (vapor--water) in the course of a continuous technological process. \nNowadays, the introduction of digital methods for correcting the hydrostatic level sensor readings is especially relevant in connection with the development of industry programs aimed at increasing the capacity of newly designed and operating nuclear power units, which pose more demanding requirements to the accuracy of thermal and physical measurements and operational safety as a whole.