Assessment of the reliability of the npp liquid radioactive waste concentration system

Abstract

The calculation of the reliability indicators of the system for the concentration of liquid radioactive waste at a nuclear power plant. The special wastewater treatment (NWT-3) of units with VVER reactors was adopted as a basic scheme. The aim of the work is to estimate the reliability of NWT -3 as a technological system. The goal is achieved by transforming the technological scheme of the system into a structural one and determining the quantitative values of the parameter of the flow of failures, the duration and probability of failure-free operation. A structural model of the system was built taking into account redundancy and suspended elements. The characteristic ways of connecting elements in the system are considered: sequential, one- and two-fold permanent redundancy, under the same loading conditions of the main and reserve elements and performing the same functions. Data on the parameters of the failure flow of the equipment that makes up the technological scheme are borrowed from reference sources. Communication means present in the diagram (valves, flanges, pipelines, etc.) are taken into account as connected serial elements of the main equipment. The probabilities of failure-free operation of equipment are calculated and the most problematic ones are identified: pumps, evaporators and heat exchangers. The probabilities of failure-free operation of the system as a whole are determined for a number of specified intervals of operation as the corresponding products of the probability of failure-free operation of the elements that make up the system. It is shown that if the parameter of the flow of failures remains unchanged, the probability of failure-free operation of the system, ensuring its effective functioning, will remain within one year of operation. The results obtained allow predicting the intervals of operational and recovery measures, highlighting the most problematic elements of the system.