Voronina A.V., Pavlov S.V.
Dimitrovgrad Engineering and Technological Institute, National Research Nuclear University MEPhI, Dimitrovgrad, Russia
Engineering formulas are presented for calculating the value of methodological error in measuring the distances from the ultrasonic sensor to the surface of the irradiated fuel assembly of WWER-1000 caused by decay heat from the fuel assembly. The methodical error arises due to the water temperature gradient along ultrasonic wave path. This is due to the presence of natural convection at the surface of the fuel assembly discharged from the reactor into cooling pool at nuclear power plant. The paper presents a methodology for calculating the methodical error. It is assumed that the water temperature between the sensor and the surface of the fuel assembly is determined by convective heat transfer between the fuel assembly and the water in cooling pool at nuclear power plant. The surface of VVER-1000 fuel assemblies is modeled by a flat vertical plate with a uniform surface heat flux. The propagation of an ultrasonic wave in a medium between the surface of a fuel assembly and an ultrasonic sensor is described in the approximation of geometric acoustics. The results of numerical calculations according to the presented method are executed in the form of nomograms. Engineering formulas for calculating the value of methodological error are obtained by processing an array of calculated data. The obtained formulas are used in the development of measuring systems for monitoring the deformation of fuel assemblies of WWER-1000 in cooling pond of nuclear power plant.
1. Pavlov S.V. Metodologiya materialovedcheskikh issledovaniy TVS i TVELov VVER dlya operativnogo soprovozhdeniya vnedreniya novogo topliva na AES [Methodology of Material Testingfor VVER Fuel Assemblies and Fuel Rods to Support Introduction of New Fuel at NPPS]. Izvestiya vuzov. Yadernaya energetika – Proseedings of Universities. Nuclear Power Engineering, 2014, no. 3, pp. 25–34.
2. Gorbatov A.A., Rudashevskiy G.E. Akusticheskie metody izmereniya rasstoyaniy i upravleniya [Acoustic Distance Measurement and Control Methods]. Moscow, Energoizdat Publ., 1981. 207 p.
3. Pavlov S.V. Nerazrushayushchie ul'trazvukovye metody issledovaniy obluchennogo topliva yadernykh reaktorov [Non-destructive Ultrasonic Methods for Studying Irradiated Fuel of Nuclear Reactors]. Dimitrovgrad, RIAR Publ., 2013. 256 p.
4. Xu Yuanhuan, Nie Yong. Distortion Measurement for Fuel Assemblies with Ultrasonic Technique. Post-Irradiation Examination and In-Pile Measurement Techniques for Water Reactor Fuels. Vienna: IAEA, 2009. IAEA-TECDOC-CD-1635.
5. Voronina A.V. Analiz effektivnosti, nadezhnosti i bezopasnosti metodov opredeleniya formoizmeneniya TVS VVER-1000 na AES [Analysis of the Efficiency, Reliability and Safety of Methods for Determining the Shape Change of VVER-1000 Fuel Assemblies at NPP]. Trudy Vserossiyskoj molodezhnoj konferentsii “Nauchnye issledovaniya i tekhnologicheskie razrabotki v obespechenii razvitiya yadernykh tekhnologiy novogo pokoleniya” [Proc. All-Russian Youth Conference “Scientific Research and Technological Development in Supporting the Development of New Generation Nuclear Technologies”]. Dimitrovgrad, 2018, pp. 62–64.
6. Dvoretskiy V.G., Ivanov V.B., Glushak N.S. Metodiki izmereniya geometricheskiy razmerov i formy chekhla TVS [Methods for Measuring the Geometric Dimensions and Shape of the Fuel Assembly Cover]. Dimitrovgrad, RIAR, 1991. 19 p.
7. Vliet G.C., Liv C.K. An Experimental Study of Turbulent Natural Convection Boundary Layers. Journal of Heat Transfer, 1969, no. 4, pp. 73–96.
8. Brazhnikov N.I. Ul'trazvukovye metody [Ultrasound methods]. Moscow, Leningrad, Energiya Publ., 1965. 248 p.
9. Pavlov S.V., Shalaginova T.M., Mikhaylov S.V., Prokudanov D.L. Issledovanie vliyaniya estestvennoy konvektsii na rezul'taty izmereniya geometricheskikh kharakteristik tvelov i teplovydelyayushchikh sborok ul'trazvukovymi metodami v usloviyakh basseynov vyderzhki [Investigation of the Influence of Natural Convection on the Results of Measuring the Geometric Characteristics of Fuel Elements and Fuel Assemblies by Ultrasonic Methods in the Conditions of Cooling Pools]. Dimitrovgrad, RIAR Publ., 1991. 28 p.
10. Voronina A.V., Pavlov S.V. Metodika i programma rascheta skorosti zvuka v vode v usloviyakh estestvennoy konvektsii u poverkhnosti teplovydelyayushchikh sborok yadernykh reaktorov [Method and Program for Calculating the Sound Speed in Water under Conditions of Natural Convection at the Surface of Fuel Assemblies of Nuclear Reactors]. Vestnik natsional'nogo issledovatel'skogo yadernogo universiteta “MIFI” – Bulletin of the National Research Nuclear University “MEPhI”, 2019, vol. 8, no. 5, pp. 465–472. doi: 10.1134/S2304487X19050080.
11. Dzhaluriya I. Estestvennaya konvektsiya. Teplo- i massoobmen [Natural convection. Heat and mass transfer]. Moscow, Mir Publ., 1983. 399 p.
12. Lykov A.V. Teplomassoobmen. Spravochnik [Heat and Mass Transfer: Handbook]. Moscow, Energiya Publ., 1978. 480 p.
