Increasing the radiation safety of nuclear power plants using the method of controlling the tightness of fuel elements
The problem of monitoring the tightness of fuel elements at the stage of their manufacture to improve the radiation safety of nuclear power plants is considered. A vibration method is proposed for non-destructive testing of the tightness of cylindrical fuel rods. The method makes it possible to perf...
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irk-123456789-1959522023-12-08T16:16:31Z Increasing the radiation safety of nuclear power plants using the method of controlling the tightness of fuel elements Mamontov, О. Nevliudov, I. Stytsenko, T. Belikov, A. Tokarieva, О. Thermal and fast reactor materials The problem of monitoring the tightness of fuel elements at the stage of their manufacture to improve the radiation safety of nuclear power plants is considered. A vibration method is proposed for non-destructive testing of the tightness of cylindrical fuel rods. The method makes it possible to perform accelerated testing of a batch of fuel rods and remove samples with gross leakage under conditions of mass production. A description of the method is given, a mathematical model of free vibrations of a fuel element is developed. The time dependences of the pressure and the period of free oscillations of the fuel element were obtained by calculation. The assessment of the influence of the inhomogeneity of the fuel element structure on the test result is carried out. Inhomogeneity causes an error in measuring the oscillation period up to 1%, which can lead to a false result. Three-dimensional plots were constructed, reflecting the main form of free vibrations of a homogeneous and inhomogeneous section of a fuel element. On the basis of the performed assessment, recommendations were given for conducting fuel rod tightness control, excluding a false result. Розглянуто проблему контролю герметичності твелів на етапі їх виготовлення для підвищення радіаційної безпеки АЕС. Запропоновано вібраційний метод неруйнівного контролю герметичності твелів циліндричної форми. Метод дозволяє виконати прискорений контроль партії твелів і видалити зразки з грубими порушеннями герметичності в умовах серійного виробництва. Наведено опис методу, розроблена математична модель вільних коливань твела. Розрахунковим шляхом отримані залежності тиску і періоду вільних коливань твела від часу. Виконано оцінку впливу неоднорідності конструкції твела на результат контролю. Неоднорідність викликає похибку вимірювання періоду коливань до 1%, що може привести до помилкового результату. Побудовано тривимірні графіки, що відображають основну форму вільних коливань однорідної і неоднорідної ділянок твела. На підставі виконаної оцінки дані рекомендації з проведення контролю герметичності твелів, які виключають помилковий результат. Рассмотрена проблема контроля герметичности твэлов на этапе их изготовления для повышения радиационной безопасности АЭС. Предложен вибрационный метод неразрушающего контроля герметичности твэлов цилиндрической формы. Метод позволяет выполнить ускоренный контроль партии твэлов и удалить образцы с грубыми нарушениями герметичности в условиях серийного производства. Представлено описание метода, разработана математическая модель свободных колебаний твэла. Расчетным путем получены зависимости давления и периода свободных колебаний от времени. Выполнена оценка влияния неоднородности конструкции твэла на результат контроля. Неоднородность вызывает погрешность измерения периода колебаний до 1%, что может привести к ошибочному результату. Построены трехмерные графики, отражающие основную форму свободных колебаний однородного и неоднородного участков твэла. На основании выполненной оценки даны рекомендации по проведению контроля герметичности твэлов, исключающих ложный результат. 2022 Article Increasing the radiation safety of nuclear power plants using the method of controlling the tightness of fuel elements / О. Mamontov, I. Nevliudov, T. Stytsenko, A. Belikov, О. Tokarieva // Problems of Atomic Science and Technology. — 2022. — № 2. — С. 68-72. — Бібліогр.: 14 назв. — англ. 1562-6016 DOI: https://doi.org/10.46813/2022-138-068 http://dspace.nbuv.gov.ua/handle/123456789/195952 621.039.546.3 en Вопросы атомной науки и техники Національний науковий центр «Харківський фізико-технічний інститут» НАН України |
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Thermal and fast reactor materials Thermal and fast reactor materials |
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Thermal and fast reactor materials Thermal and fast reactor materials Mamontov, О. Nevliudov, I. Stytsenko, T. Belikov, A. Tokarieva, О. Increasing the radiation safety of nuclear power plants using the method of controlling the tightness of fuel elements Вопросы атомной науки и техники |
| description |
The problem of monitoring the tightness of fuel elements at the stage of their manufacture to improve the radiation safety of nuclear power plants is considered. A vibration method is proposed for non-destructive testing of the tightness of cylindrical fuel rods. The method makes it possible to perform accelerated testing of a batch of fuel rods and remove samples with gross leakage under conditions of mass production. A description of the method is given, a mathematical model of free vibrations of a fuel element is developed. The time dependences of the pressure and the period of free oscillations of the fuel element were obtained by calculation. The assessment of the influence of the inhomogeneity of the fuel element structure on the test result is carried out. Inhomogeneity causes an error in measuring the oscillation period up to 1%, which can lead to a false result. Three-dimensional plots were constructed, reflecting the main form of free vibrations of a homogeneous and inhomogeneous section of a fuel element. On the basis of the performed assessment, recommendations were given for conducting fuel rod tightness control, excluding a false result. |
| format |
Article |
| author |
Mamontov, О. Nevliudov, I. Stytsenko, T. Belikov, A. Tokarieva, О. |
| author_facet |
Mamontov, О. Nevliudov, I. Stytsenko, T. Belikov, A. Tokarieva, О. |
| author_sort |
Mamontov, О. |
| title |
Increasing the radiation safety of nuclear power plants using the method of controlling the tightness of fuel elements |
| title_short |
Increasing the radiation safety of nuclear power plants using the method of controlling the tightness of fuel elements |
| title_full |
Increasing the radiation safety of nuclear power plants using the method of controlling the tightness of fuel elements |
| title_fullStr |
Increasing the radiation safety of nuclear power plants using the method of controlling the tightness of fuel elements |
| title_full_unstemmed |
Increasing the radiation safety of nuclear power plants using the method of controlling the tightness of fuel elements |
| title_sort |
increasing the radiation safety of nuclear power plants using the method of controlling the tightness of fuel elements |
| publisher |
Національний науковий центр «Харківський фізико-технічний інститут» НАН України |
| publishDate |
2022 |
| topic_facet |
Thermal and fast reactor materials |
| url |
http://dspace.nbuv.gov.ua/handle/123456789/195952 |
| citation_txt |
Increasing the radiation safety of nuclear power plants using the method of controlling the tightness of fuel elements / О. Mamontov, I. Nevliudov, T. Stytsenko, A. Belikov, О. Tokarieva // Problems of Atomic Science and Technology. — 2022. — № 2. — С. 68-72. — Бібліогр.: 14 назв. — англ. |
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Вопросы атомной науки и техники |
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2025-07-17T00:17:38Z |
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| fulltext |
ISSN 1562-6016. ВАНТ. 2022. №2(138) 68
https://doi.org/10.46813/2022-138-068
UDC 621.039.546.3
INCREASING THE RADIATION SAFETY OF NUCLEAR POWER
PLANTS USING THE METHOD OF CONTROLLING THE TIGHTNESS
OF FUEL ELEMENTS
О. Mamontov, I. Nevliudov, T. Stytsenko, A. Belikov, О. Tokarieva
1Kharkiv National University of Radio Electronics, Kharkiv, Ukraine
E-mail: olena.tokarieva@nure.ua;
2PSACEA “Prydniprovska State Academy of Civil Engineering and Architecture”,
Dnipro, Ukraine
The problem of monitoring the tightness of fuel elements at the stage of their manufacture to improve the
radiation safety of nuclear power plants is considered. A vibration method is proposed for non-destructive testing of
the tightness of cylindrical fuel rods. The method makes it possible to perform accelerated testing of a batch of fuel
rods and remove samples with gross leakage under conditions of mass production. A description of the method is
given, a mathematical model of free vibrations of a fuel element is developed. The time dependences of the pressure
and the period of free oscillations of the fuel element were obtained by calculation. The assessment of the influence
of the inhomogeneity of the fuel element structure on the test result is carried out. Inhomogeneity causes an error in
measuring the oscillation period up to 1%, which can lead to a false result. Three-dimensional plots were constructed,
reflecting the main form of free vibrations of a homogeneous and inhomogeneous section of a fuel element. On the
basis of the performed assessment, recommendations were given for conducting fuel rod tightness control, excluding
a false result.
INTRODUCTION
The issues of improving the safety and energy
efficiency of nuclear power plants remain one of the
highest priorities in the nuclear power industry. The
increase in the energy efficiency of nuclear power plants
is associated with an increase in the unit capacity of
power units and the duration of fuel campaigns. This is
possible due to a high level of fuel burnup, an increase in
energy intensity, and a tightening of the operating
conditions for fuel elements. These reasons intensify the
leakage of radionuclides outside the cladding of the fuel
elements, and tighten the technological requirements for
their tightness.
An increase in the content of radionuclides in the
primary coolant is permissible up to the operational limit.
The violation of this condition has serious medical,
environmental and social consequences. Prevention of
these problems is a complex organizational and technical
task. Its solution leads to the objective need to improve
the reliability of fuel cells at the stage of their
manufacture.
The relevance of this work is dictated by the need to
improve the radiation safety of nuclear power plants.
Safety is based on the control and removal of leaky fuel
rods at the stage of their manufacture.
LITERATURE ANALYSIS AND PROBLEM
STATEMENT
Non-destructive methods of tightness control are
known to be used in the technological process of
manufacturing fuel elements. These include radiation,
ultrasonic, optical, electromagnetic, thermal and mass
spectrometric methods. However, they all have
drawbacks, as a result of which there is no single
universal method. Radiation methods are based on the
interaction of ionizing radiation with the fuel element
cladding [1, 2]. Ionizing radiation negatively affects the
working personnel as a harmful production factor.
Radiation is absent in ultrasonic [3, 4] and optical
methods [5–7] non-destructive testing. However,
ultrasound is also a harmful production factor that
adversely affects the human being. Optical methods are
divided into visual measuring and electronic measuring.
In the first type of optical methods, workers experience
increased stress on the visual analyzer. Both varieties are
characterized by a relatively low reliability of detecting
defects, which is limited by the analysis of the outer
surface of the shell. Information on the internal state of
the shell material can be obtained by electromagnetic
[2, 6] and thermal methods [8, 9]. Electromagnetic
methods are based on the analysis of the interaction of an
external electromagnetic field with the electromagnetic
field of eddy currents excited by an electrically
conductive shell. This study also becomes harmful to
humans, especially in the microwave range. Thermal
methods are based on the registration and analysis of
temperature field inhomogeneity on the surface of a
heated shell.
The presence of a defect inside the shell material
(delamination, cavity, foreign inclusions) is not a
quantitative indicator of helium pressure, tightness or
leakage. Thus, all considered methods provide limited
information on the state of the fuel element cladding and
characterize its state indirectly. Leaks can be found with
time-consuming helium leak detectors [1].
In addition to the indicated disadvantages, the
considered methods are associated with the processing of
large amounts of information. This limits the speed of
control, even with automation tools.
Measurements of the helium pressure inside the fuel
elements can be carried out by passing through
ultrasound in the region of the compensation volume [1].
The intensity of ultrasonic vibrations that passed through
69 ISSN 1562-6016. ВАНТ. 2022. №2(138)
the inner cavity of the fuel element is proportional to the
square of the gas pressure. It is also possible to measure
the pressure inside the fuel element using normalized
local heating of the shell in the area of the compensation
volume [9]. The internal gas pressure is determined from
the temperature field on the shell surface. The speed of
control operations is significantly limited by the
performance of auxiliary actions.
On the basis of the analysis, it should be noted that
there is no method of accelerated control and detection of
leaking fuel elements. This explains the expediency of
developing a vibration method for non-destructive testing
of fuel rod tightness, which has an increased response
rate [10]. The introduction of this method will make it
possible to reduce the process of inspection of a
technological batch of fuel elements by accelerating the
identification and removal of leaky samples.
PURPOSE AND OBJECTIVES OF THE
RESEARCH
The aim of the study is to prove the possibility of
using the vibration method to control the tightness of
cylindrical fuel elements.
To achieve the goal it is required to solve the
following tasks:
– provide a description of the proposed method for
non-destructive testing of fuel elements;
– to develop a mathematical model of fuel rod
vibrations in case of gas leakage;
– to determine the dependence of the holding time
between measurements of the oscillation period on the
permissible leak, taking into account the metrological
accuracy of the frequency meter;
– to evaluate the influence of fuel element
inhomogeneity on the control result.
DESCRIPTION OF THE VIBRATION
METHOD OF NON-DESTRUCTIVE
CONTROL OF TIGHTNESS OF FUEL
ELEMENTS
The method is based on the dependence of the free
vibration period on the gas pressure inside the shell.
The period of oscillation of the non-hermetic fuel
element is reduced over time due to the decrease in the
gas pressure and the reduction of the tension of the shell.
The method is implemented as follows. The
monitored fuel element 1, after helium injection and
sealing, is installed on the supports of stand 2 and fixed
with clamps 3, Fig. 1. The exhilaration of free damped
vibrations similar to the vibrations of a string is activated.
The free vibration period (main tone) is measured using
sensor 4 and frequency meter 5.
Fig. 1. Fuel element at the control and test stand
Then the fuel element is removed from the stand, held
for a given time Δt, and the period of free oscillations is
re-measured. If there is a leak during this time, the gas
will flow out from under the shell, the tension will
decrease and the oscillation period will increase. The
holding time Δt depends on the permissible leak rate. It
should be sufficient for reliable registration of the change
in the oscillation period taking into account the
metrological accuracy of the frequency meter. The
temperature of the fuel elements at which the periods of
oscillations are measured before and after holding must
be the same. Therefore, before measuring the periods of
oscillations of the fuel elements, the specified
temperature is adjusted. For sealed fuel elements, the
oscillation periods do not differ.
Thus, an express control method has been proposed
which makes it possible to identify and remove leaking
fuel elements. Exposure of fuel rods can be carried out in
a group manner in storage facilities. It does not require
additional material costs or the time spent. The speed of
direct control in manual mode is not less than 150 pcs/h.
This makes it possible to use this method in automated
complexes for non-destructive testing of fuel elements.
The rest of the fuel elements can be monitored by
traditional methods [1–9]. This will significantly reduce
the total time for testing the tightness of a technological
batch of fuel elements.
This method can be applied in the areas of final
inspection of fuel rod manufacturers. It can also be used
in the areas of incoming inspection of nuclear power
plants.
DEVELOPMENT OF A MATHEMATICAL
MODEL OF FREE VIBRATIONS OF A FUEL
ELEMENT WITH A GAS LEAK
The mathematical model of cylindrical fuel rod
vibrations is based on the one-dimensional wave
equation of vibrations of a homogeneous string fixed at
two points [11]:
𝜕2𝑌
𝜕𝑡2
= с2
𝜕2𝑌
𝜕𝑥2
=
𝐹
𝜌𝑥
⋅
𝜕2𝑌
𝜕𝑥2
,
(1)
where Y is the vertical displacement of a point on the fuel
element surface relative to the equilibrium position (see
Fig. 1); t – time; c – coefficient depending on tension and
inertia; x – horizontal coordinate of a point on the 0x axis;
F is the shell tension along the 0x axis; 𝜌𝑥 – linear
density.
Model (1) does not take into account vibration
damping. This is due to the insignificant influence of this
factor on the period of natural oscillations, and,
consequently, on the control result.
Natural fluctuations are possible with strictly defined
periods:
𝜏𝑛 =
2𝐿
𝑛 ⋅ 𝑐
=
2𝐿
𝑛
√
𝜌𝑥
𝐹
,
(2)
where L is the distance between the clamping points, m;
n is an integer corresponding to the waveform.
Equation (2) assumes fuel element uniformity (quasi-
uniformity), in which the mass is evenly distributed along
its length. Also, equation (2) does not take into account
ISSN 1562-6016. ВАНТ. 2022. №2(138) 70
the damping of oscillations. This condition is quite
acceptable for linear systems due to the insignificant
influence of damping on the frequency (period) of
scillations. Due to this, mathematical calculations are
greatly simplified.
The design of the fuel element used in WWER-1000
reactors [1, 12] was taken as a basis, subject to quasi-
uniformity. The following data were taken as an
example: the mass of the moving part of the fuel element
was 1.4 kg, the distance between the fixation points was
2 m. The initial tension of the cladding under normal
conditions before helium injection was 1120 N. After
helium injection, the pressure inside the cladding was
25105 Pa. Helium inside the shell was considered as an
ideal gas. Its volume was 610-5 m3.
The decrease in the shell tension over time is
explained by the drop in gas pressure, which is similar to
transient processes in electrical circuits:
𝛥𝐹(𝑡) = 𝛥𝑃(𝑡) ⋅ 𝑆 = 𝛥𝑃(𝑡) ⋅
𝜋 ⋅ 𝑑2
4
,
(3)
where t – the gas outflow time, s; 𝛥𝑃(t) – time
dependence of pressure decrease, Pa; S and d – the area,
m2, and diameter, m, of the cross section of the inner
cavity of the fuel element, respectively.
𝛥𝑃(𝑡) = 𝛥𝑃0 ⋅ 𝑒
−
𝑡⋅𝑄
𝑉⋅𝛥𝑃0 ,
(4)
where 𝛥𝑃0 – initial overpressure, Pa (Fig. 2); V – volume,
m3; Q – leak, Pa ∙ m3 ∙ s−1.
Fig. 2. Graph of the dependence of the excess pressure
inside the fuel element on time
The dependence of the period of the fundamental tone
of natural vibrations of a fuel element on time (duration
of exposure) is presented by formula (5) and is shown in
Fig. 3:
𝜏(𝑡) = 2𝐿 ⋅ √
𝜌𝑥
𝐹0 + 𝛥𝐹(𝑡)
.
(5)
Fig. 3. Graph of the dependence of the period of natural
oscillations of a fuel element on time
Equations (1)–(5) represent a mathematical model of
fuel rod vibrations during gas leakage.
An important condition for this control is the required
holding time 𝛥𝑡 of the fuel elements between the
measurements of the vibration periods. The holding time
depends on the amount of leak that is allowed for the
given control method. This time should be sufficient to
reliably record changes in the oscillation period, taking
into account the metrological accuracy of measuring the
oscillation period. The measurement accuracy of the
oscillation period is limited by a number of destabilizing
factors (temperature fluctuations, vibration damping,
frequency meter error), and is
± 0.0001 s.
Fig. 4 shows the dependence of the holding time 𝛥𝑡
(represented by a logarithmic scale) on the value of the
permissible leak Q.
Fig. 4. Dependence of the logarithm of the holding time
on the magnitude of the permissible leak
The dependence in Fig. 4 is necessary for making a
decision on the use of the method in specific conditions.
ESTIMATION OF THE INFLUENCE
OF FUEL INHOMOGENEITY
ON THE CONTROL RESULT
The design of a cylindrical fuel element is shown in
Fig. 5,a. The design is a heterogeneous structure in which
the mass is unevenly distributed.
Fig. 5. Inhomogeneity of the fuel element structure:
1 – shell; 2 – spring; 3 – fuel pellets
Fig. 5,b shows a graph of the approximate
dependence of the linear density of an inhomogeneous
section of a fuel element on the x coordinate. This
dependence is represented by the empirical formula (6):
𝜌𝑥
∗ = 0.7(
𝑠𝑔𝑛( 𝑥 − 𝑙)
4
+ 0.75),
(6)
where l is the length of the section with reduced density,
m.
To assess the effect of fuel element inhomogeneity on
the oscillation period, it is required to solve the wave
71 ISSN 1562-6016. ВАНТ. 2022. №2(138)
equation (1) taking into account dependence (7). An
analytical solution is difficult. To solve this problem, the
finite difference method was applied, in which the
derivatives are represented by finite difference
approximations [13, 14]. Dividing the region of
integration into a finite number of steps, we rewrite
equation (1) in finite-difference form:
𝑌𝑗,𝑖+1 − 2𝑌𝑗,𝑖 + 𝑌𝑗,𝑖−1
ℎ2
= 𝑐2
𝑌𝑗+1,𝑖 − 2𝑌𝑗,𝑖 + 𝑌𝑗−1,𝑖
𝑘2
=
=
𝐹
𝜌𝑥
∗
⋅
𝑌𝑗+1,𝑖 − 2𝑌𝑗,𝑖 + 𝑌𝑗−1,𝑖
𝑘2
,
(7)
where j and i are the numbers of steps (grid nodes) along
the 0x and 0t axes, respectively; k and h are the lengths
of steps along the 0x and 0t axes, respectively.
We transform expression (7), reflecting the
dependence of the wave function at the next time step
i + 1 on the previous steps i and i - 1:
𝑌𝑗,𝑖+1 =
1
𝑎2
𝑌𝑗+1,𝑖 + 2𝑌𝑗,𝑖(1 −
1
𝑎2
) − 𝑌𝑗,𝑖−1
+
1
𝑎2
𝑌𝑗−1,𝑖 ,
(8)
𝑎 =
𝑘
𝑐 ⋅ ℎ
= √
𝜌𝑥
𝐹
⋅
𝑘
ℎ
.
Fig. 6 shows 3-D plots using equation (8). They
reflect free vibrations of a fuel element in the form of a
standing wave with one antinode (fundamental tone). In
Fig. 6,a – vibrations of a homogeneous section of a fuel
element (l = 0) with a linear density ρx=0.7 kg/m and a
length L = 2 m. In Fig. 6,b – vibrations of a non-uniform
area. For the sake of clarity, the length of the lightweight
part was conventionally taken equal to
l = 1m. The linear density corresponded to the graph in
Fig. 5,b. Both options were considered under the same
(normal) conditions under which the tensile force did not
change.
a
b
Fig. 6. Basic form of free vibrations (Mathcad):
a – a homogeneous section of a fuel element,
b – heterogeneous area
The comparison of the graphs shows that the
inhomogeneity of the fuel element leads to a change in
the period of free oscillations. Under the conditions
considered, the oscillation period of the inhomogeneous
section of the fuel element has noticeably decreased (by
about 12%). This is due to a decrease in the mass of the
vibrating element with a constant tension force. Taking
into account the real length of the inhomogeneous section
(l = 0.2 m), the oscillation period decreases by about 1%
(0.001 s). This value exceeds the measurement error of
the oscillation period. Obviously, when testing fuel
elements, this factor will cause a false result
(measurement error). To prevent it, when measuring the
oscillation period before and after holding, it is required
to fix the fuel element in the same places.
Oscillations with more than one antinode were not
considered due to significant damping caused by friction.
CONCLUSIONS
The article describes an express method and a test
bench for identifying and removing leaking cylindrical
fuel rods.
The method is based on the dependence of the period
of free oscillations of a fuel element on the gas pressure
inside the cladding. The period of oscillation of a leaky
fuel element decreases with time due to a decrease in gas
pressure and a decrease in cladding tension. The
detection of leaking fuel elements is carried out on the
basis of registration of a decrease in the period of free
oscillations during the holding time.
On the basis of the studies carried out, a mathematical
model has been developed that reflects the dependence of
the period of free oscillations of a fuel element on time.
The model is based on the one-dimensional wave
equation of oscillations of a homogeneous string and the
method of the analogy of transient processes in electrical
circuits.
The dependence of the holding time between the
measurements of the oscillation period on the value of the
permissible leak is obtained. This dependence is
necessary for making a decision on the use of the method
in specific conditions.
Using the finite difference method, the influence of
fuel element inhomogeneity on the test result was
estimated. It has been established that heterogeneity can
lead to a false result. To prevent it, when measuring the
oscillation period before and after holding, it is required
to fix the fuel element in the same places.
As a result of the studies carried out, the possibility of
monitoring the tightness of fuel rods using the proposed
express method was confirmed. The introduction of this
method in combination with the existing control methods
will improve the radiation safety of nuclear power plants.
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Article received 11.02.2022
ПІДВИЩЕННЯ РАДІАЦІЙНОЇ БЕЗПЕКИ АТОМНИХ ЕЛЕКТРОСТАНЦІЙ
ЗА ДОПОМОГОЮ МЕТОДУ КОНТРОЛЮ ГЕРМЕТИЧНОСТІ ТВЕЛІВ
О.В. Мамонтов, І.Ш. Невлюдов, Т.Є. Стиценко, А.С. Беліков, О.В. Токарєва
Розглянуто проблему контролю герметичності твелів на етапі їх виготовлення для підвищення радіаційної
безпеки АЕС. Запропоновано вібраційний метод неруйнівного контролю герметичності твелів циліндричної
форми. Метод дозволяє виконати прискорений контроль партії твелів і видалити зразки з грубими
порушеннями герметичності в умовах серійного виробництва. Наведено опис методу, розроблена
математична модель вільних коливань твела. Розрахунковим шляхом отримані залежності тиску і періоду
вільних коливань твела від часу. Виконано оцінку впливу неоднорідності конструкції твела на результат
контролю. Неоднорідність викликає похибку вимірювання періоду коливань до 1%, що може привести до
помилкового результату. Побудовано тривимірні графіки, що відображають основну форму вільних коливань
однорідної і неоднорідної ділянок твела. На підставі виконаної оцінки дані рекомендації з проведення
контролю герметичності твелів, які виключають помилковий результат.
ПОВЫШЕНИЕ РАДИАЦИОННОЙ БЕЗОПАСНОСТИ АТОМНЫХ ЭЛЕКТРОСТАНЦИЙ
С ПОМОЩЬЮ МЕТОДА КОНТРОЛЯ ГЕРМЕТИЧНОСТИ ТВЭЛОВ
О.В. Мамонтов, И.Ш. Невлюдов, Т.Е. Стиценко, А.С. Беликов, О.В. Токарева
Рассмотрена проблема контроля герметичности твэлов на этапе их изготовления для повышения
радиационной безопасности АЭС. Предложен вибрационный метод неразрушающего контроля
герметичности твэлов цилиндрической формы. Метод позволяет выполнить ускоренный контроль партии
твэлов и удалить образцы с грубыми нарушениями герметичности в условиях серийного производства.
Представлено описание метода, разработана математическая модель свободных колебаний твэла. Расчетным
путем получены зависимости давления и периода свободных колебаний от времени. Выполнена оценка
влияния неоднородности конструкции твэла на результат контроля. Неоднородность вызывает погрешность
измерения периода колебаний до 1%, что может привести к ошибочному результату. Построены трехмерные
графики, отражающие основную форму свободных колебаний однородного и неоднородного участков твэла.
На основании выполненной оценки даны рекомендации по проведению контроля герметичности твэлов,
исключающих ложный результат.
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