Izvestiya vuzov. Yadernaya Energetika

The peer-reviewed scientific and technology journal. ISSN: 0204-3327

Ultrasonic Monitoring of the VVER-1000 FA Form Change

3/20/2021 2022 - #01 Global safety, reliability and diagnostics of nuclear power installations

Voronina A.V. Pavlov S.V. Amosov S.V.

DOI: https://doi.org/10.26583/npe.2022.1.06

UDC: 621.039.546.8

A procedure has been developed to determine the geometrical parameters of fuel assemblies (FA) by an ultrasonic pulse-echo technique used for all types of light-water reactor FAs. The measurement of geometrical parameters is achieved through the pairwise installation of ultrasonic sensors opposite the FA spacer grid faces at a distance of not more than a half of the sensor acoustic field near-region length such that the acoustic axes of the pairwise sensors are parallel to each other. The advantages of the presented technique is that it enables monitoring of any FA modifications, including the VVER reactor assemblies with a different number of spacer grids.

The paper presents a mathematical model of the acoustic path developed in a geometrical acoustics approximation and its verification results. The model was used for computational and experimental studies of the ultrasonic test technique, and engineering formulas have been developed to calculate the errors of the sensor measurement of the distance to the FA surface. A software package has been developed to simulate the FA form change monitoring and can be used to design new monitoring systems.

The developed technique to determine the VVER-1000 FA geometrical parameters was introduced at units 1 and 2 of the Temelin NPP, the Czech Republic, for the TVSA-T FA form change monitoring. The successful use of the proposed technique makes it possible to recommend it for use in inspection benches at other NPPs


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ultrasonic technique fuel assembly form change model natural convection