KONBiN’03 The 3-rd Safety and Reliability International Conference RELIABILITY ASSESSMENT AND CONTROL OF SYSTEM DESIGNED FOR MEASUREMENT OF COOLANT FLOW THROUGH FUEL CHANNELS IN RBMK-1500 REACTOR JUOZAS AUGUTIS, VAIDAS MATUZAS, ROBERTAS ALZBUTAS, EUGENIJUS UŠPURAS Lithuanian Energy Institute j.augutis@if.vdu.lt, eugeniju@isag.lei.lt, vaidas@mail.lei.lt, robertas@mail.lei.lt Abstract: The reliability of a system, which is designed for measurement of coolant flow through fuel channels in Ignalina nuclear power plant RBMK-1500 reactors, is considered. It is developed a strategy for replacement of measurement equipment, which ensure the required reliability for whole system. According to forecasting of measurement equipment failures, the new methodology for preventive replacement of measurement equipment is developed. Key words: measurement system, flowmeter, statistical analysis, and reliability control. 1. INTRODUCTION Special measurement system SHADR is used for measurement of coolant flow rate through the fuel channels volume in RBMK-1000 and RBMK-1500 nuclear power plants [1]. Out of 1661 coolant flowmeters, 240 flowmeters are connected to the emergency protection system, and they are primarily related to the reactor operation safety. A ball type flowmeter, called SHADR, measures flow rates using mechanical and magneto-electrical detection equipment. Coolant flow in SHADR becomes rotated. Rotated flow affects the sensitive part of the flowmeter – a ball, which is forced to rotate. Thus, the ball rotation speed is proportional to the coolant flow rate. For the fixing of the ball rotation speed, by the rotation path, at the outside of hull magnet-induction sensor is fastened. When the ball rotates through it, this generates an electrical impulse and in such a way, angular ball rotation speed is transferred into a set of electrical impulses. The reliability of the flowmeter system is important for reactor safety as well as for economical reasons. When one channel flowmeter fails, the channel operation and energy production in this channel is stopped until the planned future maintenance. When 10 or more flowmeters fail in one quarter of the core, the reactor is shut down immediately.