Experimental research of the air permeability of concrete in the compressed zone of the containment for power units no. 1, 2 of the South-Ukrainian NPP
Authors:   SE “State Scientific and Engineering Center for Control Systems and Emergency Response”, Zhygalov Ia. A. , Inyushev V. V. ,   SE “State Scientific and Engineering Center for Control Systems and Emergency Response”, Posokh V. O. ,   SE “State Scientific and Engineering Center for Control Systems and Emergency Response”, Vyzhva S. A. ,   Research Laboratory of Theoretical and Applied Geophysics of the Educational and Scientific Institute “Institute of Geology” of Taras Shevchenko National University of Kyiv, Onyshchuk I. I. ,   Research Laboratory of Theoretical and Applied Geophysics of the Educational and Scientific Institute “Institute of Geology” of Taras Shevchenko National University of Kyiv
Published: June 2021

The determination of the air permeability of concrete in the compressed zone of NPP’s containment under conditions of excessive air pressure in the subshell space of the reactor compartment under a maximum design basis accident is necessary to confirm the localizing functions of the containment when extending the lifetime of power units. Approaches to determining the localizing ability (air permeability) of concrete in the compressed zone of the containment of NPPs with WWER-1000 type reactors under the impact of excessive air pressure under conditions of maximum design basis accident are discussed in the article. The designed testing installation for experimental studies of the air permeability of concrete by the method of stationary radial filtration is described and the results of experimental researches of the air permeability on the installation are presented for samples simulating the composition of concrete used under construction of the containment for Power Units No. 1, 2 (series B-302 and B-338, respectively) SD “South-Ukrainian NPP”. A comparative analysis of the results of abovementioned experimental researches with the results of experimental and theoretical work on the study of air permeability of the similar samples-imitators of concrete by the method of stationary linear filtration, as well as the results of measurements for samples of concrete sampled directly from the compressed zone of containment for Power Unit No. 2 of SD “South-Ukrainian NPP” was fulfilled. The results are explained by processes of compaction of the concrete structure under a complex stress state that occurs under specific hardening conditions and during longtime compression by pre-stressed reinforcing ropes, which takes place under conditions of real containment operation. It was concluded that the simulators made according to the currently accepted technology cannot provide a correct determination of the localizing ability of the NPP’s containment, since the conditions and time of containment concrete hardening, as well as the longtime constant compressive action of reinforcing ropes, cannot be correctly modeled in full under the formation of samples-imitators. The issue of the containment concrete samplesimitators creating in laboratory conditions requires additional study, improvement of technology and the development of new approaches with maximum physical modeling of the conditions characteristic of the operation of the NPP containment.