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7EARTH SCIENCES
DETERMINATION OF SITE AMPLIFICATION IN THE SOUTH UKRAINIAN NPP
Semenova Yu.
Candidate of Physical and Mathematical Sciences, doctoral student, senior researcher, Subbotin Institute of Geophysics of the National Academy of Sciences of Ukraine, Kyiv
Kendzera O.
Corresponding Member of NAS of Ukraine, Deputy Director, Subbotin Institute of Geophysics of the National Academy of Sciences of Ukraine, Kyiv
Abstract
The main goal of the article is to analyze possible seismic effects in soils of different zones of the territory of the South Ukrainian NPP and to discuss the influence of local geology on the amplification of seismic vibrations. This paper presents the results of modeling the amplification of seismic vibrations by soils at the site of the South Ukrainian Nuclear Power Plant.
Keywords: seismic microzoning, nonlinear analysis, frequency characteristic, amplification factor
Introduction. According to UN data, seismic disaster forms about 51% of the total number of cataclysms and prevails among different natural catastrophes. Citizens of the country have the right to protection of life and health against effects of natural and anthropogenic disasters, including earthquakes. This right must be secured, within their competence, by all subjects of state authority and economic agents in the country territory. However, for their successful performance, seismologists have to provide them with information on parameters of the design seismic effects. Basing on this information, design engineers and builders must provide the seismic stability of housing and industrial structures, using technical actions of seismic protection adequate to the current hazard level.
An important requirement in the design and operation of nuclear power plants (NPPs) is to ensure and maintain nuclear and radiation safety guarantees during seismic impacts.
The seismic stability of nuclear power plant structures during seismic oscillations depends on the interaction of the structure and the soil base. At the same time, the soil stratum of the territory where the main NPP facilities are located serves as a frequency converter of the amplitude of seismic vibrations. At some frequencies, the amplitude of the oscillations decreases, at others it increases.
All buildings also have their own oscillation period or resonance factor, in which the wave energy, summed in a few seconds, enhances the oscillation amplitude of the building. If the period of vibration of the soil corresponds to its own period of the building, it will undergo the greatest possible fluctuations and may receive the most damage.
Thus, the seismic hazard parameters at the site depend not only on the strength of the earthquake and the distance from the epicenter of the earthquake, but also on surface geology.
The decision of the National Security and Defense Council, which was enacted by Decree of the President of Ukraine No. 585/2011 of May 12, 2011, noted the need for an in-depth reassessment of the safety status of
the power units of Ukrainian NPPs, taking into account the lessons learned from the Fukushima-1 accident, including verification of their earthquake resistance. The purpose of the reassessment of the seismic safety of power units is to understand the real state of structures, systems and elements, based on their required safety function and withstand seismic impact, and, as a result, assess the seismic safety margin of the installation [1].
To study the seismic characteristics of local soil conditions and to predict the quantitative parameters of soil vibrations in case of a possible earthquake at a particular site, work is being done on seismic microzoning.
When determining the level of seismic impact, a parameter is widely used - peak ground acceleration. However, technicians know that the ability of seismic movement of soil to cause damage to structures, systems and elements with a plastic reaction does not correlate well with the level of peak soil acceleration. It is recognized that other parameters, such as velocity, displacement, duration of significant displacement, spectral acceleration, spectral energy density and cumulative absolute velocity, should play an important role in the sound assessment of the effects of seismic ground motion on structures, systems and elements [1]. Another example is the effects caused by earthquakes of low intensity in the near field (i.e., with M<5.5). Most of these events have a high-frequency composition and create high levels of peak soil acceleration, but do not lead to serious damage to structures and mechanical equipment. However, if the high-frequency components of the spectrum created by such near-field earthquakes are transmitted to the structures, this can cause problems for the operability of certain types of equipment.
Using the frequency response of the soil stratum allows us to evaluate the effect of the soil stratum on the transformation of the initial seismic impact.
According to the regulatory document SBS V.1.1-12: 2014 [2], As a rule, calculation methods are used to analyze the features of the soil behavior of the studied area under strong seismic influences. For calculations,
detailed mathematical models are used that most accurately describe the response of the soil to seismic effects, including possible local effects.
Site amplification in the South Ukrainian NPP. The studies performed are due to a reassessment of the seismic hazard and seismic resistance of the site of the South Ukrainian NPP in order to increase the operational reliability and safety of the NPP. The basis is nuclear safety requirements, IAEA recommendations SSG-9.
According to the results of seismic micro-zoning, the territory of the South Ukrainian NPP was divided
into 3 zones, where the seismic effect can be different. For each zone, separate frequency characteristics and a set of calculated accelerograms were calculated.
To assess the influence of the thickness of sedimentary rocks, we used one-dimensional (horizontally layered models of the environment), which is quite acceptable when the boundaries between the main geological elements are close to the horizontal. The layered composition of seismic-soil models of three zones of the territory of the South Ukrainian NPP are presented in Tables 1-3.
Table1
Properties of soil profile of zone 1 of the territory of the South Ukrainian nuclear power plant.
Soil Type Shear-wave Velocity (Vs), m/s Mass Density (p), g/cm3 Thickness, m
Surface soil 200 1.69 2.5
Loamy loam 230 1.83 1.0
Clay 260 1.88 2.0
Indigenous clays 260 1.88 1.7
Indigenous sands 300 1.90 3.0
Kaolins (loam) 300 1.90 2.3
Woody soil and woody sand 350 2.00 1.5
Rock 2000 2.60 -
Table2
Properties of soil profile of zone 2 of the territory of the South Ukrainian nuclear power plant.
Soil Type Shear-wave Velocity (Vs), m/s Mass Density (p), g/cm3 Thickness, m
Surface soil 200 1.69 1.5
Loamy loam 230 1.83 1.0
Clay 260 1.88 2.0
Indigenous clays 260 1.88 2.5
Woody soil and woody sand 350 2.00 1.5
Rock 2000 2.60 -
Table3
Properties of soil profile of zone 3 of the territory of the South Ukrainian nuclear power plant.
Soil Type Shear-wave Velocity (Vs), m/s Mass Density (p), g/cm3 Thickness, m
Surface soil 200 1.69 4.0
Loamy loam 230 1.83 1.3
Indigenous clays 300 1.90 1.7
Indigenous sands 300 1.90 1.0
Kaolins (loam) 300 1.90 7.0
Woody soil and woody sand 350 2.00 1.5
Rock 2000 2.60 -
From Tables 1-3 it follows that Mean shear wave velocity of sedimentary layers varying from 200m/sec to 350m/s in all zones. Shear wave velocity of the bedrock equal to 2000m/s.
The calculations used an equivalent linear model of the soil response to seismic effects. Equivalent linear site response analyses were performed using Proshake software [3]. The behavior of each layer was specified by the Kelvin-Voigt model (viscoelastic). The nonline-arity of soil stress-strain behavior means that the shear modulus of the soil is constantly changing. For each layer, the shear modulus reduction and damping ratio
curves were chosen in order to take into account the nonlinearity.
The equivalent linear method has two big advantages in the engineering practice. The first one is the stability of the numerical integration, and the other is the preparation of the input data on the mechanical property [4].
In fig. 1 shows the calculated frequency characteristics of the three zones of the site of the South Ukrainian NPP.
Figure 1 The calculated frequency characteristics of the three zones of the site of the South Ukrainian NPP.
From the results presented in fig. 1, it can be seen that the frequency response of the soil in zone 1 of the South Ukrainian NPP is characterized by the frequency range of resonant amplification of seismic oscillations from 2.06 to 4.0 Hz with a maximum gain of 4.93. In the indicated frequency range, one clear maximum is observed at a frequency of 3.26 Hz. The frequency response of the soil stratum of zone 2 is characterized by the frequency range of resonant amplification of seismic oscillations from 6.14 to 8.14 Hz with a maximum gain of 9.76. In the specified frequency range, one clear maximum at a frequency of 7.26 Hz. The frequency response of the soil stratum of zone 3 is characterized by the frequency range of resonant amplification of seismic oscillations from 2.82 to 4.3 Hz with a maximum gain of 7.79. In the specified frequency range, one clear maximum at a frequency of 3.68 Hz. Comparing the frequency characteristics of the soil strata of the three zones allocated within the territory of the South Ukrainian NPP, it can be seen that zone 1 is characterized by lower natural oscillation frequencies compared to zones 2 and 3.
An analysis of the calculated frequency characteristics showed that they differ depending on the ground conditions of each zone. Soil amplification of seismic waves in zone 2 is greater than in zone 1 and zone 3. This phenomenon can be explained by the fact that the thickness of sedimentary deposits in the context of the soil thickness of zone 2 is the smallest. The thickness of sedimentary deposits in zone 2 is 8.5 m, and in zone 1 - 14 m, and in zone 3 - 16.5 m. In the context of the soil stratum of the territory of the South Ukrainian NPP, the depth of bedrock changes quite sharply. This leads to a shift of the resonance maxima in a wide range of frequencies. Zone 1 differs from zone 3 in lower shear wave velocities, which explains the greater absorption of seismic energy and a decrease in amplification of seismic vibrations. Comparing the frequency characteristics of the soils of the three zones of the territory of the South Ukrainian NPP, a classic picture is observed: softer, friable soils have lower frequency vibrations than dense clay or coarse clastic ones.
The obtained frequency characteristics were used to generate calculated accelerograms simulating design earthquakes from the Vrancea zone and from zones of local focal zones.
Conclusions. Destruction and damage to earthquake-resistant structures during earthquakes is associated not only with poor construction quality, but also with unfavorable soil conditions of their sections and the coincidence of natural frequencies of structures with maximum spectral density of the frequency characteristics of soil layers (resonance effects). There may also be a thinning of the soil base or a partial loss of its bearing capacity (non-linear effects). The rheological properties of the soil stratum affect the reaction of the surface layer under seismic loading.
This paper presents the results of modeling the amplification of seismic vibrations by soils at the site of the South Ukrainian Nuclear Power Plant. The territory of the South Ukrainian NPP was divided into 3 zones according to the results of seismic microzoning. For each zone, the resulting frequency response and a set of calculated accelerograms were calculated separately. The influence of the rheological properties of the soil on the amplification of the site and the resonance frequency is analyzed for each zone. Under the conditions of the site of the South Ukrainian NPP, the roof of the ore stone changes quite sharply. This leads to a shift of the resonance maxima in a wide range of frequencies.
Comparing the frequency characteristics of the soil of the three zones visualized on the territory of the South Ukrainian nuclear power plant, it was found that zone 1 is characterized by lower natural oscillations frequencies compared to zones 2 and 3.
Accounting for seismic vibrations in the low frequency range is especially necessary for the seismic resistance of objects. Since objects located on the territory of Ukraine can be damaged by strong earthquakes from the Vrancea zone. Seismic effects from these earthquakes are characterized by low-frequency long-term oscillations and spread over long distances without significant attenuation, which can cause dangerous resonance phenomena.
In general, all three zones on the territory of the South Ukrainian nuclear power plant will have a different soil response to seismic effects. Although the zones are located very close to each other.
Therefore, in each case, it is necessary to calculate the own frequency response of the soil and a set of designed accelerograms.
REFERENCES:
1. NS-G-2.13 "Seismic hazard assessment of existing nuclear facilities." Safety guide. A series of safety standards. IAEA, Vienna, 2014
2. Building in seismic regions of Ukraine: SBS V.1.1-12: 2014, (2014). Kiev: Building Ministry of Ukraine, 84 p. [in Ukrainian]
3. ProShake Ground Response Analysis Program, version 1.1. User's Manual, EduPro Civil Systems, Washington, USA, 1998, 54 p.
4. Yoshida, N. (2015), Seismic Ground Response Analysis. Springer, 365 p.
INTEGRAL ASSESSMENT OF ANTHROPOGENIC INTRODUCTION OF WATER OB'KTIV IN
CHERKASK REGION
Shutak K.
Post-graduate student, Department of Ecology and Life Safety Uman National University of Horticulture Uman, Ukraine
1НТЕГРАЛЬНА ОЦ1НКА АНТРОПОГЕННОГО ЗАБРУДНЕННЯ ВОДНИХ ОБ'СКТ1В
ЧЕРКАСЬКО!ОБЛАСТ1
Шутак К.В.
астрантка кафедри екологН та безпеки життeдiяльностi Уманський нацюнальний утверситет садiвництва
Умань, Украша
Abstract
The integrative indexes of anthropogenic pollution water objects of the largest river basins situated on the territory of Cherkasy region are elaborated and calculated. The evaluation of the hydroecological state of water objects is realized. A schematic map of the hydroecological situation in Cherkasy region is created.
Анотащя
Розроблено й обчислено штегральш показники антропогенного забруднення водних об'екпв найб№-ших pi4TOBm басейшв на територи Черкасько! обласп. Проведено оцшку пдроеколопчного стану водних об'екпв. Створено картосхему пдроеколопчно! ситуацп в Черкаськш обласп.
Keywords: integrative index, anthropogenic pollution, water objects, river basin, Cherkasy region.
Ключовi слова: штегральна ощнка, антропогенне забруднення, водш об'екти, рiчковий басейн, Чер-каська область.
Для проведення iнтегральноi характеристики й оцiнки екологiчного стану водних об'екпв Черкасько! областi ми беремо до уваги такi окремi показники, як скидання зворотних спчних вод, уза-гальнений показник забруднення шюдливими ре-човинами (який ми одержуемо, перемножуючи обсяги скидiв, виражеш в т/рiк, на об'еми скидання, обчислюваш в млн. м^рш1, мiнералiзацiю та гiдробiологiчну оцiнку [3]. Ще двома показниками могли би бути рiвень бiологiчного забруднення гiдрооб'ектiв та забрудненосп пiдземних вод, але бюлопчне забруднення на Черкащинi нiде не пере-вищуе допустимi норми, а рiвень забруднення пiдземноi гiдросфери е приблизно однаковим у межах обласп.
Вважаемо за необхiдне визначити вагу кожного з перелiчених чиннишв формування пдроеко-логiчноi ситуацii шляхом присвоення !м числових коефiцiентiв. Найб№ш значущим на нашу думку, е узагальнений показник забруднення водних об'екпв, який отримуе коефiцiент - 3. Згаданий параметр характеризуе пдрооб'екти й цiлi рiчковi ба-сейни достатньо комплексно, враховуючи значення обсяпв скидiв та об'емiв скидання речовин. Показник скидання зворотних спчних вод одержуе
коефiцieнт - 2. Решта показникiв, у тому чи^ при-рости забруднення водних об'екпв зворотними стiчними водами та рiзноманiтними речовинами, мають коефiцieнт - 1.
Формула штегрального оцiнювання антропогенного забруднення водних об'екпв у межах рiч-кового басейну виглядае таким чином:
I=2V,3ce+AV3ce+3Py+APy+M+HB, (1) де I - штегральний показник пдроеколопчного стану, V3ce - об'ем виквдв зворотних спчних вод, AV3ce - прирiст показникiв забруднення водних об'екпв зворотними водами, Ру - узагальнений показник забруднення шюдливими речовинами, АРу -прирют показнишв надходження до гiдрооб'eктiв забруднюючих речовин, М - мiнералiзацiя вод, НВ - гвдробюлопчна оцiнка.
За формулою (1) ми розраховуемо значення ш-тегральних показникiв екологiчного стану водних об'екпв кожного з рiчкових басейшв.
Зокрема, басейн Дшпра одержуе 39 балiв, оскiльки вiн мае п'ятибальш показники забруднення водних об'екпв зворотними спчними водами та шшдливими речовинами з урахуванням числових коефщенпв, а також приросту ввдповщних
