Estimations of high-temperature diffusion in Chernobyl’s concrete construction
The content of isotopes Ti, Ni, Zr, Cs and U in the cores, which was taken from the concrete construction of ChAPS, was studied by the gamma-activation analysis. It has been developed a numerical model to analyze heat and mass transfer in concrete at high temperatures accompanying incident of 1986...
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Національний науковий центр «Харківський фізико-технічний інститут» НАН України
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irk-123456789-812432015-05-14T03:01:50Z Estimations of high-temperature diffusion in Chernobyl’s concrete construction Dikiy, N.P. Dedik, A.N. Dovbnya, A.N. Uvarov, V.L. Применение ядерных методов The content of isotopes Ti, Ni, Zr, Cs and U in the cores, which was taken from the concrete construction of ChAPS, was studied by the gamma-activation analysis. It has been developed a numerical model to analyze heat and mass transfer in concrete at high temperatures accompanying incident of 1986. Comparison of the measured isotope distributions with the simulation data has enabled to estimate some attendant circumstances of the incident. Методом гама-активаційного аналізу вимірювався зміст ізотопів Ti, Ni, Zr, Cs та U у кернах, відібраних з бетонної конструкції ЧАЕС. Розроблено числову модель для аналізу переносу тепла та маси у бетоні при високих температурах, що супроводжували катастрофу 1986 року. Порівняння виміряних ізотопних розподілів з результатами модельних розрахунків дало можливість зробити оцінки деяких характеристик інциденту, що стався. Методом гамма-активационного анализа измерялось содержание изотопов Ti, Ni, Zr, Cs и U в кернах, отобранных из бетонной конструкции ЧАЭС. Разработана численная модель для анализа тепло- и массопере- носа в бетоне при высоких температурах, сопровождавших катастрофу 1986 года. Сравнение измеренных изотопных распределений с результатами модельных расчетов дало возможность сделать оценки некоторых характеристик происшедшего инцидента. 2005 Article Estimations of high-temperature diffusion in Chernobyl’s concrete construction / N.P. Dikiy, A.N. Dedik, A.N. Dovbnya, V.L. Uvarov // Вопросы атомной науки и техники. — 2005. — № 6. — С. 127-129. — Бібліогр.: 7 назв. — англ. 1562-6016 PACS: 28.41.Te, 02.60.Cb, 07.05.TP, 68.35.Fx, 44.35.+c http://dspace.nbuv.gov.ua/handle/123456789/81243 en Вопросы атомной науки и техники Національний науковий центр «Харківський фізико-технічний інститут» НАН України |
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Digital Library of Periodicals of National Academy of Sciences of Ukraine |
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Применение ядерных методов Применение ядерных методов |
| spellingShingle |
Применение ядерных методов Применение ядерных методов Dikiy, N.P. Dedik, A.N. Dovbnya, A.N. Uvarov, V.L. Estimations of high-temperature diffusion in Chernobyl’s concrete construction Вопросы атомной науки и техники |
| description |
The content of isotopes Ti, Ni, Zr, Cs and U in the cores, which was taken from the concrete construction of
ChAPS, was studied by the gamma-activation analysis. It has been developed a numerical model to analyze heat and
mass transfer in concrete at high temperatures accompanying incident of 1986. Comparison of the measured isotope
distributions with the simulation data has enabled to estimate some attendant circumstances of the incident. |
| format |
Article |
| author |
Dikiy, N.P. Dedik, A.N. Dovbnya, A.N. Uvarov, V.L. |
| author_facet |
Dikiy, N.P. Dedik, A.N. Dovbnya, A.N. Uvarov, V.L. |
| author_sort |
Dikiy, N.P. |
| title |
Estimations of high-temperature diffusion in Chernobyl’s concrete construction |
| title_short |
Estimations of high-temperature diffusion in Chernobyl’s concrete construction |
| title_full |
Estimations of high-temperature diffusion in Chernobyl’s concrete construction |
| title_fullStr |
Estimations of high-temperature diffusion in Chernobyl’s concrete construction |
| title_full_unstemmed |
Estimations of high-temperature diffusion in Chernobyl’s concrete construction |
| title_sort |
estimations of high-temperature diffusion in chernobyl’s concrete construction |
| publisher |
Національний науковий центр «Харківський фізико-технічний інститут» НАН України |
| publishDate |
2005 |
| topic_facet |
Применение ядерных методов |
| url |
http://dspace.nbuv.gov.ua/handle/123456789/81243 |
| citation_txt |
Estimations of high-temperature diffusion in Chernobyl’s concrete construction / N.P. Dikiy, A.N. Dedik, A.N. Dovbnya, V.L. Uvarov // Вопросы атомной науки и техники. — 2005. — № 6. — С. 127-129. — Бібліогр.: 7 назв. — англ. |
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Вопросы атомной науки и техники |
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2025-07-06T05:43:40Z |
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| fulltext |
ESTIMATIONS OF HIGH-TEMPERATURE DIFFUSION IN CHER-
NOBYL’S CONCRETE CONSTRUCTION
N.P. Dikiy, A.N. Dedik, A.N. Dovbnya, V.L. Uvarov
National Science Center “Kharkov Institute of Physics and Technology”,
Kharkov, Ukraine
e-mail: ndikiy@kipt.kharkov.ua
The content of isotopes Ti, Ni, Zr, Cs and U in the cores, which was taken from the concrete construction of
ChAPS, was studied by the gamma-activation analysis. It has been developed a numerical model to analyze heat and
mass transfer in concrete at high temperatures accompanying incident of 1986. Comparison of the measured isotope
distributions with the simulation data has enabled to estimate some attendant circumstances of the incident.
PACS: 28.41.Te, 02.60.Cb, 07.05.TP, 68.35.Fx, 44.35.+c
1. INTRODUCTION
The major scientific and technical problem of atomic
engineering is reliable isolation of radioactive and toxic
materials and substances from possible penetrate into an
environment. Therefore there are actual the researches,
able to give the helpful information for a material choice
and development of building designs of the future atom-
ic power stations or storehouses for radioactive waste
disposal. In this connection, there is especial interest to
studying the samples taken from elements of an environ-
ment of reactor ChAPS, undergone to extreme influence
as a result of accident 1986.
2. DESCRIPTION OF SAMPLES AND MEA-
SUREMENTS
The samples were taken in 2000 from a concrete
wall of the reactor technological channel, which was
filled by the fused magma after a time after explosion of
a reactor were investigated. Our interest in the present
work is concentrated on studying of traces of magma ef-
fect on the channel walls while it has not flowed out
through the burnt bottom of the channel after 83 hours
[3]. The position of test selection was located on 0.5 m
above a level of magma. Researched samples represent-
ed section of a core 5 cm long received by consecutive
drilling the concrete wall in a direction outside to its ax-
is. The upper crumbled core about 2.5 cm long adjoi-
ning to the surface was inaccessible to measurements.
The selected samples were irradiated with brems-
strahlung radiation at the electron accelerator [1,2,4]
which had the top energy spectrum border 20.2 MeV;
the magnitude of absorbed in samples doze was
2·106 Gr. There was used the reactions: 49Ti(γ,p)48Sc,
238U(γ,n)237U, 90Zr(γ,n)89Zr, 58Ni(γ,n)57Ni. The gamma-ra-
diation of the activated isotopes was measured by means
of spectrometer with Ge(Li) detector. The cesium con-
tent profile was estimated at isotope 137Cs activity.
3. MODEL FEATURES
For simulation of dynamic characteristics of diffu-
sion of researched isotopes the numerical model using a
finite difference method [5] and taking into account se-
ries of concrete important features, exhibiting under the
influence of high temperature has been developed.
Concrete represents the complex porous multiphase
system, which at a local level is in thermodynamic bal-
ance with body interstice, filled by liquid water and a
gas phase. Heat and mass transfer processes in concrete
structures at high temperatures are accompanied by a
number of the accompanying nonlinear phenomena.
Along with heat conductivity, such phenomena also in-
clude propagation of vaporized and liquid water, the
pressure caused by gradients, capillary effects, just as
the latent heat of the phase transitions caused by change
water (evaporation, desorption in pores, dehydration)
and solid phase. Furthermore with change of porous
structure at high temperature permeability of concrete
sharply grows.
The model consists of the four basic balance equa-
tions. The thermal balance equation for whole medium
includes heat effects of the phase change and dehydra-
tion process. The balance of weight of dry air includes
the diffusion and pressure forced flows. The mass bal-
ances of the liquid water and of the vapor have been
summarized together to eliminate the source term con-
cerning to phase changes (evaporation or condensation).
The diffusion equation was accepted in the form, which
is not taking into account possible mutual influence of
isotopes, participating in process. The carried out simu-
lations have been executed within the framework of one-
dimensional model and in the assumption of medium
uniformity. The full model allows simulating by means
of the finite difference method the evolution of tempera-
ture, moisture content and impurities distribution in
view of phase transitions in a concrete matrix, which
commonly can be described by means of experiments.
4. DISCUSSION OF RESULTS
The measured dependences of the isotope content on
core depth are shown in Fig. 1. The concentration level
indicates that these isotopes cannot represent compo-
nents of concrete in the starting state. The liquid sprays
of raging magma likely got on the channel walls and
have penetrated inside under the action of high tempera-
PROBLEMS OF ATOMIC SCIENCE AND TECHNOLOGY. 2005, № 6.
Series: Nuclear Physics Investigations (45), p. 127-129. 127
ture. There is content reduction in the top core parts is
appreciably for majority of elements. It can be consequence
0.0 0.1 0.2 0.3 0.4 0.5
10-1
100
101
102
103
Zr
Ni
Cs, Bk/g
Ti
U
C
on
te
nt
, p
pm
Depth, m
Fig. 1. Measured isotope content on depth of the
core taken from the concrete wall
0.0 0.1 0.2 0.3 0.4 0.5
0
500
1000
1500
0.0 0.1 0.2 0.3 0.4 0.5
0.0
0.2
0.4
0.6
0.8
1.0
T
T
em
pe
ra
tu
re
, °
C
Ti
Ni
N
or
m
al
iz
ed
c
on
te
nt
Depth, m
Fig. 2. Normalized penetration profile Ti and Ni
combined with simulated temperature distribution in
concrete
0.0 0.1 0.2 0.3 0.4 0.5
0
500
1000
1500
0.0 0.1 0.2 0.3 0.4 0.5
0.0
0.2
0.4
0.6
0.8
1.0
T T
em
pe
ra
tu
re
, °
C
Zr
U
Cs
N
or
m
al
iz
ed
c
on
te
nt
Depth, m
Fig. 3. Normalized penetration profile Zr, U and Cs
combined with simulated temperature distribution in
concrete
of element leaching from surficial region as a result of
probable penetration of moisture into the channel till
sampling time.
For thermo diffusion process simulation in the pre-
sented work the model in iterative process has been used
to determine parameters, describing in the best way ex-
perimentally measured element contents. At that, taking
into account that accessible physical characteristics of
concrete in such extreme conditions carry a significant
share of uncertainty, it was justified some simplifica-
tions in model [6].
The magma temperature magnitude in the channel
remained a constant and held out, by different estima-
tions [3], from 1700°C up to 2400°C, owing to its big
weight. Therefore we accepted temperature of a con-
crete surface not smaller, than 1700°C.
At calculation of temperature evolution in concrete,
it in the general way is necessary to take into account a
number of the complex phase transformations occurred
in concrete. For example, hydration (near 95°C) and de-
hydration (at 120°C) processes removal chemically
bound water from concrete crystalline hydrates at tem-
peratures 300…400°C, rising compression and expan-
sion deformations in cement paste and aggregate at
500…800°C, recrystallization of calcium hydro alumi-
nates to corresponding aluminates are higher than 800°С
and the beginning of concrete physical destruction, in
general, demand power expenses [7]. In our calculations
we have combined these processes as two main phase
transitions: connected to water evaporation and to phase
changes of concrete solid components.
Fig. 2 shows the diagram of the simulated concrete
temperature profile, imposed on graph of the normalized
contents Ti and Ni, which, obviously, represent captured
by liquid melt components of constructional materials.
On the temperature diagram the breaks corresponding to
the main phase transitions are visible.
From Fig. 2 one can see that penetration profiles for Ti
and Ni reveal the similar behavior and break up on a
background of temperature distribution to two obvious
parts: the determined by high-temperature diffusion area
and a zone, apparently, connected with active participa-
tion of diffusing metal ions in concrete crystalline hy-
drate reorganization.
Fig. 3 shows the similar diagram combinations for
isotopes Zr, U and Cs, representing components actually
reactor materials. One can see, that Cs penetration has
quite habitual character when it is isomorphic replaced
in crystal components of solid medium. Apparent ab-
sence of connection of its content with areas of phase
changes can account for its gaseous state (boiling tem-
perature 951.6 K) and consequently could not be appre-
ciably involved to interactions with participation of a
liquid phase. It is worthy of notice negative correlation
of Cs and Zr contents in high temperature region, con-
nected, probably, with their competitive participation in
diffusion processes.
The profile characters of penetration into concrete
matrix for Zr and, especially, for U shows their raised
migration in the high temperature region, which proba-
bly connected with calcium hydroaluminate recrystal-
lization zone in cement paste. One also can see some
signs of increase of U ion mobility in the average tem-
peratures zone.
In attempts of more adequate simulation of experi-
mentally measured penetration profiles of isotopes of in-
128
terest, various kinds of boundary conditions have been
tested. However, we did not manage to reveal substan-
tial improvement of fitting quality in the assumption of
variable concentration or presence mass exchange at
surface, owing probably to the limited experimental data
volume. Therefore we have confined within constant el-
ement concentration at the concrete surface.
Effective diffusion constants in the high temperature
zone and surface contents evaluated within the frame-
work of iterative fitting of accepted model to received
experimental data are resulted in the table.
Diffusion constants and surface contents estimates
evaluated at data in the high temperature region
Isotope Diffusion constant,
10-8 m2/s Surface content, %
49Ti 1,8 0.9
58Ni 1,1 0.04
90Zr 3 0.02%
137Cs 0,6 110 Bk/g
238U 8 0.018
Though, owing to high fitting errors, one can only
speak about estimations of the received values, it does
not cause doubts a high factor of diffusion for U and a
big Ti content at the concrete surface.
5. CONCLUSIONS
The technique for thermo diffusion parameter defini-
tion in a concrete matrix is offered by comparison of
simulated dynamic diffusion process characteristics with
results of experiment.
The received estimations should be considered, as
the initial stage in necessary studying consequences of
accident. Nevertheless, it is necessary to note the catas-
trophic U leaching, in comparison with other isotopes,
in region, where permeability of concrete is sharply in-
creased owing to destruction of its structure at high tem-
perature influence. In view of U properties are similar to
other actinium series elements, its behavior features im-
pose special requirements of characteristics of the con-
crete used in construction of nuclear objects.
The problem in computing sense is complex and de-
mands the further regular calculations on the basis of ac-
cumulation of an experimental material and expansion
of databases with use of powerful algorithms and com-
puter equipment.
The work is executed within the framework of Pro-
gram ЯМРТ-2010, Project X866.
REFERENCES
1. N.P. Dikiy, S.Yu. Sayenko, V.L. Uvarov,
E.P. Shevyakova. The nuclear-physical methods
application for a radionuclide transport in a granite
rocks studies // Problems of Atomic Science and
Technology. Series: Nuclear Physics Investiga-
tions. 2000, №2(38), p. 54-57.
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jacent regions // Problems of Atomic Science and
Technology. Series: Nuclear Physics Investiga-
tions. 2003, №2(41), p. 25-29.
3. V.N. Geras’ko, A.A. Kljuchnikov, A.A. Korne-
jev, V.I. Kupnyi, A.V. Nosovskiy, V.N. Scherbin. The
object “Cover”. History, state and prospect. Kiev:
“Intergraphica”, 1997, 224 p. (in Russian).
4. N.P. Dikiy, A.N. Dovbnya, N.A. Skakun,
V.L. Uvarov, M.A. Khazhmuradov, B.I. Shra-
menko B.I. Use of accelerators in geology,
medicine, isotopes production and atomic power
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ИССЛЕДОВАНИЕ ВЫСОКОТЕМПЕРАТУРНОЙ ДИФФУЗИИ В ОБРАЗЦАХ
БЕТОННОЙ КОНСТРУКЦИИ ЧАЭС
Н.П. Дикий, А.Н. Дедик, А.Н. Довбня, В.Л. Уваров
Методом гамма-активационного анализа измерялось содержание изотопов Ti, Ni, Zr, Cs и U в кернах,
отобранных из бетонной конструкции ЧАЭС. Разработана численная модель для анализа тепло- и массопере-
носа в бетоне при высоких температурах, сопровождавших катастрофу 1986 года. Сравнение измеренных
изотопных распределений с результатами модельных расчетов дало возможность сделать оценки некоторых
характеристик происшедшего инцидента.
ДОСЛІДЖЕННЯ ВИСОКОТЕМПЕРАТУРНОЇ ДИФУЗІЇ У ЗРАЗКАХ
БЕТОННОЇ КОНСТРУКЦІЇ ЧАЕС
М.П. Дикий, А.М. Дедик, А.М. Довбня, В.Л. Уваров
Методом гама-активаційного аналізу вимірювався зміст ізотопів Ti, Ni, Zr, Cs та U у кернах, відібраних з
бетонної конструкції ЧАЕС. Розроблено числову модель для аналізу переносу тепла та маси у бетоні при
високих температурах, що супроводжували катастрофу 1986 року. Порівняння виміряних ізотопних
129
розподілів з результатами модельних розрахунків дало можливість зробити оцінки деяких характеристик
інциденту, що стався.
130
N.P. Dikiy, A.N. Dedik, A.N. Dovbnya, V.L. Uvarov
National Science Center “Kharkov Institute of Physics and Technology”, Kharkov, Ukraine
REFERENCES
Н.П. Дикий, А.Н. Дедик, А.Н. Довбня, В.Л. Уваров
М.П. Дикий, А.М. Дедик, А.М. Довбня, В.Л. Уваров
|