Nefedov S.S.
Nefedov S.S.

Nefedov S.S.


Publications

Analysis of Kinematics of the Earthquake at the «Kashivazaki-Kariva» Nuclear Power Plant
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In present article are considered seismic acceleration data (accelerogramms) recorded at the site of the NPP Kashivazaki-Kariva (Japan) at the earthquake of 16.07.2007 with epicenter in Japan see. As a result of the earthquake some buildings, structures and infrastructure objects of NPP were damaged. As marked in the report of the mission of International Atomic Energy Agency (IAEA), significant part of these damages was caused by big displacements of the soils.

Site of NPP was provided by the net of accelerometers located at different levels and oriented at three cardinal directions. At the time of earthquake the accelerometers were in operating state, and the records of accelerations (accelerogramms) were obtained. In present work evaluation of the velocities of seismic oscillations and evaluation of seismic displacements of soils were fulfilled on the base of analysis of three-component accelerogramm recorded at the free surface of the soil. 

STRENGTH CRITERIA OF NPP CONTAINMENT UNDER EXTERNAL ACTIONS
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The code of practice in the field of atomic energy establishes the safety targets for NPPs. One of these safety targets regulate the yearly probability of large emergency radioactive release into the air. Accident with reactor pipelines rupture can occur in the case of earthquake. In this case the containment serves as a barrier against radioactive release into the environment. The purpose of this work was to define the strength criteria for containment to ensure the safety targets of yearly probability of large emergency release at seismic and other external events. The results of the work show that in the case of external events the containment strength criteria provide correspondence with safety targets if they are defined with account of yearly probability of the action assumed and with due account of probability of failure (rupture) of reactor pipelines under this action. The strength criteria for containment should be defined with overconsevative reserves, the more is the yearly probability of the action assumed and the more is the probability of reactor pipelines failure under this action. It is shown that at small yearly probability of the action and small probability of the reactor pipelines failure the strength criteria of containment, defined due to the safety target of a yearly probability of large accidental release, became less conservative then civil and erection strength criteria.

Seismic damages of electric grid facilities
Issue: #1-2022
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Electric grid facilities (EGF) are the part of life support system of territories. About of 30% of EGF of RF lay in the zone of 7 and more units of 12-units seismic scale MSK-64. Experience shows the damageability of EGF at earthquakes. In conditions of earthquake EGF objects show less seismic resistance than objects of electric generation (electric stations). Equipment of EGF objects shows less seismic resistance than civil structures, in which it is installed.

The object of this work is to create the recommendations for improvement of seismic resistance of main EGF objects – electric transmission lines (ETL) and transformer substations (TSS) – on the base of analysis of typical damages of these objects.

Analysis shows that main reasons of seismic damages of air ETL are elastic oscillations of transmission towers as well as their opposite mutual movement if occurs in different phases of seismic wave. Elastic oscillations cause deformation of truss angles due to shear force, damage of foundation and rupture of earth conductors. Opposite mutual movements cause dynamic changes of tension of line of air ETL, rupture of line conductors and rupture of cables of cable ETL

Main equipment of TSS includes power transformers, switching equipment and apparatus of relay defense and automatics (RDA). Seismic damages of power transformers are mainly caused by their displacements at earthquake. As a result of the displacements occur jerks and damages to electrical connections - flexible (wires) or rigid (bushing), which cause increase in the forces transmitted to the transformer insulators (porcelain) and lead to breakage of the latter, short circuits and fires. Main damages of switching equipment at earthquakes are connected with the cracking and break of porcelain insulating columns which are often used as a support of switching apparatus. This causes damage and fall of apparatus. Damages of RDA are mainly connected with deformation and fall of electric cabinets and also with fault or false action of contact elements with not enough seismic resistance.

On the base of analysis of seismic damages of equipment of EGF objects the recommendations for improvement of their seismic resistance are proposed.