Proceedings of the conference

Khairetdinov V.U. Saratov A.Yu. 

Experimental and calculational justification of seismic resistance of VVER-1000/1200 RP equipment by the results of commissioning tests and measurements

At the present time, the regulatory documentation on the safety of NPP requires the obligatory studying of dynamic characteristics (natural frequencies, modes and decrements of attenuation) important to safety of RP systems and components by the method of dynamic tests in the actual conditions of fastening and binding at the object during commissioning of each NPP Unit to assure seismic resistance of VVER-1000/1200 reactor plant (RP).

The necessity to determine the natural dynamic characteristics, important to safety of RP main equipment (steam generator, reactor coolant pump set (RCP set), main coolant pipeline, pressurizer, etc.) in the actual on-site conditions is caused by the resonance character of seismic response when seismic disturbances can change by the order and more dependent on ratios of frequencies of natural dynamic characteristics and load.

Accuracy of the only calculation assessments of natural dynamic characteristics at the stage of designing of RP main equipment (without experimental verification, confirmation and correction of design values of dynamic characteristics by the actual data) does not meet the practical needs.

Tests and measurements as a part of commissioning measurement system (CMS) are performed for experimental determination of natural dynamic characteristics of the main equipment of RP in the actual fastening conditions. Excitation of the structure takes place with the help of vibroimpact (impulsive) method of vibration assignment. Excitation is made by a local impact using a special hammer. Selection of the places of placing the vibration measurement converters for registration of attenuating responses is made by the geometrical mesh in the areas where the maximum or the minimum amplitude of damping vibrations is expected. Application of the independent software-hardware complex with the Fourier conversion allows to perform a modal analysis of the studied structures with the post-processing for determination of natural frequencies and attenuation decrements.

Tests are performed at different states of the main equipment of RP: with the empty and filled circuit, and during single startup of RCP sets with the parameters of “cold” and “hot” run of RP.

The calculation-analytical model of the studied structures is developed and applied on the basis of design drawings and specified data on fastening and binding in the actual conditions to provide the complete justification of seismic resistance of RP equipment together with the measurements and tests in the actual conditions. The calculation-analytical model enables to get the insight on the natural modes and frequencies of the examined objects in convenient and evident form.

The studies and tests are performed at Leningrad-2 NPP, Unit 1, and TNPS, Unit 3, and enable to carry out a comparative analysis for different design versions of RP with VVER-1000/1200.

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