Combined calculation of radiation from large-sized ground RW storage facilities on the basis of Monte Carlo method
A technique to reduce the dose rates, produced by large-sized ground-based radiation sources with dozens of radiating elements of the same geometry arranged along the perimeter, is developed. The radiating elements represent the concrete rectangular casks into which cylindrical barrels filled with c...
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| Опубліковано в: : | Вопросы атомной науки и техники |
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Національний науковий центр «Харківський фізико-технічний інститут» НАН України
2019
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| Цитувати: | Combined calculation of radiation from large-sized ground RW storage facilities on the basis of Monte Carlo method / V.G. Rudychev, N.A. Azarenkov, I.O. Girka, D.V. Rudychev, Y.V. Rudychev // Problems of atomic science and technology. — 2019. — № 5. — С. 69-74. — Бібліогр.: 10 назв. — англ. |
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Rudychev, V.G. Azarenkov, N.A. Girka, I.O. Rudychev, D.V. Rudychev, Y.V. 2023-12-03T15:31:29Z 2023-12-03T15:31:29Z 2019 Combined calculation of radiation from large-sized ground RW storage facilities on the basis of Monte Carlo method / V.G. Rudychev, N.A. Azarenkov, I.O. Girka, D.V. Rudychev, Y.V. Rudychev // Problems of atomic science and technology. — 2019. — № 5. — С. 69-74. — Бібліогр.: 10 назв. — англ. 1562-6016 https://nasplib.isofts.kiev.ua/handle/123456789/195218 621.039.546 A technique to reduce the dose rates, produced by large-sized ground-based radiation sources with dozens of radiating elements of the same geometry arranged along the perimeter, is developed. The radiating elements represent the concrete rectangular casks into which cylindrical barrels filled with compacted RW are loaded. The spatial distribution of the radiation around the cask is calculated by the Monte Carlo method. The radiation is assumed to be produced by the definite radionuclides of RW. Shielding by neighboring containers and the presence of an additional biological shielding are taken into account. Different options of the container arrangement are considered. Розроблено методику зменшення дозових навантажень, створюваних приповерхневими джерелами випромінювань великих розмірів, на периметрі яких знаходяться десятки випромінюючих елементів однакової геометрії. Випромінюючі елементи являють собою бетонні прямокутні контейнери, в яких розміщені циліндричні ємності з пресованими РАВ. Виконано розрахунки просторових характеристик випромінювання методом Монте-Карло навколо контейнера, створюваного окремими радіонуклідами РАВ, з урахуванням екранування сусідніми контейнерами при різних варіантах їх розміщення, а також наявності додаткового біозахисту. Разработана методика уменьшения дозовых нагрузок, создаваемых приповерхностными источниками излучений больших размеров, на периметре которых находятся десятки излучающих элементов одинаковой геометрии. Излучающие элементы представляют собой бетонные прямоугольные контейнеры, в которых размещены цилиндрические емкости с прессованными РАО. Выполнены расчеты пространственных характеристик излучения методом Монте-Карло вокруг контейнера, создаваемого отдельными радионуклидами РАО, с учетом экранирования соседними контейнерами при разных вариантах их размещения, а также наличия дополнительной биозащиты. en Національний науковий центр «Харківський фізико-технічний інститут» НАН України Вопросы атомной науки и техники Problems of modern nuclear power engineering Combined calculation of radiation from large-sized ground RW storage facilities on the basis of Monte Carlo method Комбінований розрахунок випромінювань від поверхневих сховищ РАВ великих розмірів на основі методу Монте-Карло Комбинированный расчет излучений от поверхностных хранилищ РАО больших размеров на основе метода Монте-Карло Article published earlier |
| institution |
Digital Library of Periodicals of National Academy of Sciences of Ukraine |
| collection |
DSpace DC |
| title |
Combined calculation of radiation from large-sized ground RW storage facilities on the basis of Monte Carlo method |
| spellingShingle |
Combined calculation of radiation from large-sized ground RW storage facilities on the basis of Monte Carlo method Rudychev, V.G. Azarenkov, N.A. Girka, I.O. Rudychev, D.V. Rudychev, Y.V. Problems of modern nuclear power engineering |
| title_short |
Combined calculation of radiation from large-sized ground RW storage facilities on the basis of Monte Carlo method |
| title_full |
Combined calculation of radiation from large-sized ground RW storage facilities on the basis of Monte Carlo method |
| title_fullStr |
Combined calculation of radiation from large-sized ground RW storage facilities on the basis of Monte Carlo method |
| title_full_unstemmed |
Combined calculation of radiation from large-sized ground RW storage facilities on the basis of Monte Carlo method |
| title_sort |
combined calculation of radiation from large-sized ground rw storage facilities on the basis of monte carlo method |
| author |
Rudychev, V.G. Azarenkov, N.A. Girka, I.O. Rudychev, D.V. Rudychev, Y.V. |
| author_facet |
Rudychev, V.G. Azarenkov, N.A. Girka, I.O. Rudychev, D.V. Rudychev, Y.V. |
| topic |
Problems of modern nuclear power engineering |
| topic_facet |
Problems of modern nuclear power engineering |
| publishDate |
2019 |
| language |
English |
| container_title |
Вопросы атомной науки и техники |
| publisher |
Національний науковий центр «Харківський фізико-технічний інститут» НАН України |
| format |
Article |
| title_alt |
Комбінований розрахунок випромінювань від поверхневих сховищ РАВ великих розмірів на основі методу Монте-Карло Комбинированный расчет излучений от поверхностных хранилищ РАО больших размеров на основе метода Монте-Карло |
| description |
A technique to reduce the dose rates, produced by large-sized ground-based radiation sources with dozens of radiating elements of the same geometry arranged along the perimeter, is developed. The radiating elements represent the concrete rectangular casks into which cylindrical barrels filled with compacted RW are loaded. The spatial distribution of the radiation around the cask is calculated by the Monte Carlo method. The radiation is assumed to be produced by the definite radionuclides of RW. Shielding by neighboring containers and the presence of an additional biological shielding are taken into account. Different options of the container arrangement are considered.
Розроблено методику зменшення дозових навантажень, створюваних приповерхневими джерелами випромінювань великих розмірів, на периметрі яких знаходяться десятки випромінюючих елементів однакової геометрії. Випромінюючі елементи являють собою бетонні прямокутні контейнери, в яких розміщені циліндричні ємності з пресованими РАВ. Виконано розрахунки просторових характеристик випромінювання методом Монте-Карло навколо контейнера, створюваного окремими радіонуклідами РАВ, з урахуванням екранування сусідніми контейнерами при різних варіантах їх розміщення, а також наявності додаткового біозахисту.
Разработана методика уменьшения дозовых нагрузок, создаваемых приповерхностными источниками излучений больших размеров, на периметре которых находятся десятки излучающих элементов одинаковой геометрии. Излучающие элементы представляют собой бетонные прямоугольные контейнеры, в которых размещены цилиндрические емкости с прессованными РАО. Выполнены расчеты пространственных характеристик излучения методом Монте-Карло вокруг контейнера, создаваемого отдельными радионуклидами РАО, с учетом экранирования соседними контейнерами при разных вариантах их размещения, а также наличия дополнительной биозащиты.
|
| issn |
1562-6016 |
| url |
https://nasplib.isofts.kiev.ua/handle/123456789/195218 |
| citation_txt |
Combined calculation of radiation from large-sized ground RW storage facilities on the basis of Monte Carlo method / V.G. Rudychev, N.A. Azarenkov, I.O. Girka, D.V. Rudychev, Y.V. Rudychev // Problems of atomic science and technology. — 2019. — № 5. — С. 69-74. — Бібліогр.: 10 назв. — англ. |
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ISSN 1562-6016. PASТ. 2019. №5(123), p. 69-74.
UDC 621.039.546
COMBINED CALCULATION OF RADIATION FROM LARGE-SIZED
GROUND RW STORAGE FACILITIES ON THE BASIS
OF MONTE CARLO METHOD
V.G. Rudychev
1
, N.A. Azarenkov
1
, I.O. Girka
1
, D.V. Rudychev
1
,Y.V. Rudychev
2
1
V.N. Karazin Kharkiv National University, Kharkiv, Ukraine;
2
National Science Center ”Kharkov Institute of Physics and Technology”, Kharkiv, Ukraine
E-mail: rud@pht.univer.kharkov.ua
A technique to reduce the dose rates, produced by large-sized ground-based radiation sources with dozens of
radiating elements of the same geometry arranged along the perimeter, is developed. The radiating elements
represent the concrete rectangular casks into which cylindrical barrels filled with compacted RW are loaded. The
spatial distribution of the radiation around the cask is calculated by the Monte Carlo method. The radiation is
assumed to be produced by the definite radionuclides of RW. Shielding by neighboring containers and the presence
of an additional biological shielding are taken into account. Different options of the container arrangement are
considered.
INTRODUCTION
During operation of all the types of nuclear power
plants (NPPs), liquid and solid radioactive waste (RW)
is produced. For the long-term operation of NPPs in
Ukraine, a significant amount of RW has been
accumulated. To reduce the RW volume at the NPPs, it
is preprocessed. The liquid waste is evaporated (it turns
to “salt melt”), solid combustible waste is burned and
pressed, non-combustible waste is pressed. The
resulting conditioned RW is placed into cylindrical
barrels with the volume of 200 to 280 l. One of the
options for the further handling of the conditioned waste
is loading it into the reinforced concrete rectangular
casks, which either are transported to the permanent
storage site or may be temporarily (up to 50 years)
stored at the site area of the NPP. The RW storage
efficiency is achieved at the capacity of over 1000
rectangular casks that can be arranged in several tiers
[1].
Such a storage facility represents a radiation source
with the size of tens of meters, consisting of radiating
elements of the same geometry but of different activity
and isotopic composition. Storage of the conditioned
RW at the NPP site, whose area is limited, requires
adherence to the radiation safety standards for the NPP
personnel who are working at the territory adjacent to
the storage facility. Ensuring the radiation safety
standards is possible either by building up a protective
wall of concrete around the storage site, or by making a
disciplinary fence outside the security zone. One cannot
calculate the external radiation, which varies both at
sequential filling of the storage site and due to changes
in the isotopic composition subject to the RW storage
time, by traditional methods. The correct calculation of
the radiation generated by only one rectangular cask, in
which cylindrical barrels filled with conditioned RW are
placed, is currently possible only by Monte Carlo
methods.
The objective of this work is:
to develop a combined method of calculation for
the external radiation from a large source, consisting of
radiating elements of the same geometry, on the basis of
the calculation of the radiation from the reinforced
concrete rectangular casks, loaded by barrels with RW
of different activity and isotopic composition, by using
the Monte Carlo method;
to minimize the dose rates on the NPP personnel
due to arranging the sources of different radiation dose
along the storage area perimeter.
1. INITIAL DATA
At present, nonreturnable reinforced concrete
protective casks (NCPC)-150-1.5P are used to pack up
the conditioned radioactive waste [1]. The NCPC casks
are designed for loading them with radioactive waste of
low and intermediate level and its safe long-term
storage. The shape and dimensions of the cask comply
with the conditions of arrangement of four 200 liter-
barrels containing mainly “salt melt”. Characteristics of
the NCPC-150-1.5P are given in Table 1, and its outer
view is shown in Fig. 1.
Fig. 1. The outer view of NCPC-150-1,5P casks
The problem of the RW centralized storage is still
unsolved in Ukraine. That is why the possibility to store
the products of preprocessing the solid radioactive
waste (SRW) and liquid radioactive waste (LRW) in the
universal reinforced concrete protective cask (UCPC) is
under consideration. It is supposed to place four barrels
with a volume of 200 or 280 l containing compacted
RW into the UCPC, therefore its inner volume is
increased to 2.25 m
3
. As long as it is supposed to store
compacted ash with a rather high activity, the UCPC
walls are thicker than those of the NCPC, what makes
20 cm of concrete (see Table 1).
Table 1
Properties of the reinforced concrete protective casks
Name
NCPC-150-
1.5P
UCPC
(Ukraine)
Capacity, m
3
1.5 2.25
Wall thickness, cm 15 20
Overall dimen-
sions, cm 165×165×137 195×195×150
After placing of four primary barrels into the UCPC,
the remaining free space inside this cask is filled with
lightweight concrete with the density of ~ 1.6 g/cm
3
.
This leads to a decrease in the level of gamma-radiation
dose rate outside the UCPC and an improvement of
safety while handling of the UCPC, i.e. when a cask
falls down, the primary packages remain inside the cask
and are not destroyed. The schematic view of the UCPC
in which four primary packages are placed is presented
in Fig. 2.
Fig. 2. Schematic of UCPC
It is supposed to provide an interim storage of the
compacted RW in the storage facility on the NPP site
area in a light-type hangar, where more than
1000 UCPCs are arranged in four tiers (Fig. 3.)
Fig. 3. Arrangement of UCPCs in four tiers
Consequently, the storage facility represents a
source of radiation of large size (tens of meters),
composed of “cubes” of UCPCs with different
characteristics of the external radiation. The radiation
features outside the cask are determined by the activity,
spectral and elemental composition of the RW loaded
into the primary packages.
To determine the thickness of the walls of the light-
type hangar storage, ensuring the radiation protection,
and to determine the dose rates on personnel and the
environment (both with biological shielding and without
it) it is necessary to calculate the superposition of the
radiation fields produced by the UCPCs arranged along
the storage facility perimeter.
The following radionuclides determine more than
90% of the total activity of solid and liquid RW of the
NPPs equipped with WWER reactors:
54
Mn,
60
Co,
110m
Ag,
134
Cs,
137
Cs. Their half-life is more than half a
year. The averaged content of these isotopes for
different types of RW is given in Table 2 [2, 3]. From
the above data it follows, that the RW isotopic
composition significantly changes with an increase of
storage time due to the decrease in the content of the
isotopes with a short decay period. Taking into account
the specific activity of the casks (RW is low or
intermediate activity level), heating due to beta decay
can be neglected [4, 5].
Table 2
Nuclide content in the salt melt, pressed SRW, and ash
produced after burning of SRW and radioactive oil
# Isotope
Average
energy
of -
quanta,
MeV
T1/2,
year
Content of isotopes
χj, %
Ash SRW
Salt
melt
1
54
Mn 0.83 0.858 24 28.60 –
2
60
Co 1.25 5.27 59 22.10 20
3
110m
Ag 0.86 0.685 – 22.10 –
4
134
Cs 0.70 2.06 12 3.80 15
5
137
Cs 0.66 30 5 23.40 65
After preprocessing, the density of the compacted
RW reaches 3 g/cm
3
for SRW (SRW by 70%
consists of concrete and contains up to 30% of iron),
2.2 g/cm
3
for the pressed ash, and from 1.7 to 2.1 g/cm
3
for the salt melt. The elemental composition of salt melt
and ash is close to that of concrete.
2. CALCULATION TECHNIQUE FOR
RADIATION OUTSIDE THE UCPC CASKS
In atomic energy, the gamma-radiation from vessels
of various shape filled with RW are usually calculated
using the method of volume integration of radiation
point sources, which is realized in MicroShield [6] and
VOLUME [7] codes. In our case, the biological
shielding comprises the walls of the UCPC cask and
lightweight concrete within the free space between the
primary sources. Therefore, the biological shielding is
characterized by a sufficiently large thickness. As a
result, mentioned above codes cause a big error when
calculating the characteristics of radiation in different
directions around the UCPCs. Probably, this is due to
the fact that the models in these codes have little in
common with the real geometry of the UCPC.
At present, the characteristics of the external
radiation from the sources with complex geometry are
calculated with a high degree of accuracy by using the
Monte Carlo method. Fig. 2 shows the geometric model
of the reinforced concrete protective cask with four
cylindrical sources of radiation, which was developed in
the MCNP code [8]. The following radiation features
are calculated at specified distances from the UCPC
surface on the basis of this model: spectral composition,
angular distribution, dose rate, etc. These radiation
features are determined by the main RW isotopes:
54
Mn,
60
Co,
110m
Ag,
134
Cs,
137
Cs. Such an approach makes it
possible to determine these features subject to the
specified initial isotopic composition of radionuclides in
the radioactive waste, as well as the variation of these
features depending on the storage time [9]. The
distribution of the dose rate (DR), produced by the
compacted RW (SRW), radionuclide
60
Co, in the
horizontal (X, Y) and vertical (X, Z) planes around the
UCPC is shown in Fig. 4. The density of the compacted
SRW, loaded into the primary packages with a volume
of 280 l, is chosen to be 3 g/cm
3
. Similar radiation
features are calculated for the rest of the main isotopes:
54
Mn,
110m
Ag,
134
Cs,
137
Cs. The type of the DR
dependencies for these isotopes is similar to that for
60
Co. However, the DR values are lower due to the fact,
that the average energy of -quanta, emitted by the
radionuclides
54
Mn,
110m
Ag,
134
Cs,
137
Cs, is lower than
the energy of
60
Co -quanta (see Table 2). From the data
given in Fig. 4 it follows, that the radiation spatial
distribution around the UCPC is non-uniform in both
horizontal and vertical planes. The spatial distribution of
the radiation, produced by the UCPCs group, obviously
depends on the relative position of the casks.
a
b
Fig. 4. DR distribution in the horizontal (a) and in the vertical (b)
plane around the UCPC
In the following two main options for ensuring the
radiation safety of the storage facility in which the
UCPCs with RW are located at the NPP site or in the
limited area, where the personnel, not engaged in the
RW handling, can be present, are considered. The first
option foresees building of a radiation protective wall
(biological shielding). The second option foresees
determining the size of the security zone and the
installation of a disciplinary fence.
Fig. 5. Options of placing the UCPC in the
horizontal plane
The personnel radiation safety requires that the dose
rate does not exceed the allowable one at a certain
distance from the radiation protective wall or at the
security zone perimeter. It is obvious, that the largest
contribution to the dose rate is made by the radiation
sources located along the boundaries of the storage
facility. Different options of the UCPC arrangement
along the storage facility perimeter in the horizontal
plane are shown in Fig. 5. At the distances between the
casks L1 = 10…50 cm, the DR is determined by RW
placed in the primary packages (1, 2, 1’, 2’), which are
nearest to Detect-1 and Detect-2. The radiation from the
sources (3, 4, 3’, 4’) is considerably shielded by the
primary packages (1, 2, 1’, 2’) filled with compacted
RW of a rather high density and by an additional
protection made of lightweight concrete. At the
distances between the casks L2 = 50…100 cm, the DR
is increased due to the radiation from the source 4’. The
UCPCs are arranged at the storage facility in four tiers.
In the case of standard arrangement of the detectors at
the height of 1 m from the ground level, at the distances
comparable with the size of the cask, the maximum DR
is produced by the casks, placed in the first tier. At the
distances over 10 m, the contribution to the DR of all
tiers is almost the same.
Spatial distribution of the DR, produced by one
UCPC at L1 = 20 cm, along the perimeter is determined
for the following two options. First is the protective wall
at the distance of 3 m from the UCPC, which is 40 cm
thick wall of concrete with the density of 2.3 g/cm
3
. The
second is the security zone with the distance of 30 m
from the UCPC. Here, the main radionuclides,
contained in the SRW, are taken into account. The
maximum DR from the UCPC is produced in both cases
by
60
Co isotope, then, down going, by radionuclides:
110m
Ag,
134
Cs,
54
Mn,
137
Cs. The spatial distribution of the
DR produced by one UCPC along the perimeter of the
storage facility is shown in Fig. 6. Activity of
radionuclides
60
Co,
54
Mn, and
137
Cs, is assumed to be
1 Bq. Quantum yield for each isotope is taken into
account. The DR distributions are normalized to the DR,
produced by
60
Co radionuclide.
Presented in Fig. 6 distributions are used to calculate
the total DR produced by UCPC arranged along the
storage facility perimeter and filled with RW of
different isotopic composition and activity.
Fig. 6. Spatial distribution of DR produced by one
UCPC along the storage facility perimeter. Activity of
60
Co,
54
Mn, and
137
Cs
is 1 Bq
The intermediate values of the DR dependences on
the distance along the storage facility perimeter are
determined by spline interpolation of discrete data,
calculated in the MCNP code. The DR at the given
distance from the casks arranged along the storage
facility perimeter, produced by i-th isotope from one
UCPC (in our case i = 1…5 for nuclides
54
Mn,
60
Co,
134
Cs,
137
Cs,
110m
Ag, respectively) with 1 Bq activity, is
determined by spline function Dri(x), x coordinate is
measured from the center of the cask. The DR from all
Dri(x) isotopes reads as:
i
( ) ( ) ,i iDR x Dr x A (1)
where Ai is the activity of the i-th isotope contained in
the UCPC.
The total DR at point x along the storage facility,
produced by N casks arranged along the storage facility
perimeter, is determined as follows:
1
( ) (| |) ,
N
J J
J
D x DR x X Q
(2)
where XJ is the coordinate of the J-th cask, QJ is the
relative activity of the J-th cask if DR(х) are the same,
i.e. isotopic composition is identical, but the activities
are different. Appropriate DR(х) are used in the case of
different RW isotopic compositions.
Since the UCPCs, loaded with RW, have different
activities, then, by using the least square technique [10],
which we developed earlier, it is possible to reduce the
DR at the disciplinary fence of the security zone due to
the optimal arrangement of casks along the storage
facility perimeter. The solution of this problem is
carried out by minimizing the mean-square deviation of
DR from its average value at the distance of 0 x Хр
along the storage facility perimeter. The average value
of DR reads as:
1 0
1
(| |) .
XpN
J J
J
Dav Q DR x X dx
Xp
(3)
The mean-square deviations of DR from their mean
values are:
2
10
(| |) .
N
J J
J
Xp
DR x X Q Dav dx
(4)
The mean-square deviation Δ reaches its minimum
for the UCPC activity values QJ, which are determined
from the solution of the following system of N linear
equations:
2
10
(| |) 0.
N
J J
JJ
Xp
d
DR x X Q Dav dx
dQ
(5)
The right-hand side of all N linear equations with
QJ unknown quantities is equal to zero, therefore the
system of equations (5) has the trivial solution QJ = 0.
Since the sum of all the UCPC activities QJ is nonzero,
then the sequential addition of the equation
N
J
J constQ
1
instead of one of the N linear equations
of system (5) results in a system of equations having a
non-trivial solution.
In [1], it was proposed to arrange the primary
packages with RW with a shift towards one of the
corners of the NCPC cask (asymmetric loading)
(Fig. 7). In this case the DR from two faces of the filled
NCPC cask decreases. To reduce the DR we propose to
load two UCPC casks asymmetrically and to arrange
them in pairs on the storage facility perimeter (see
Fig. 7).
Fig. 7. Asymmetric arrangement of the UCPC and
their mirror placement in pairs along the storage
perimeter
3. NUMERICAL RESULTS
The radiation from the casks arranged in four tiers
has been calculated for two options: with a protective
wall and with a security zone (see Fig. 6). Dose rates as
a function of the distance along the storage facility are
determined with account for the partial contribution of
radionuclides in accordance with the SRW isotopic
composition in the form of splines (see Table 2). The
spatial distribution of the DRs produced by 27 rows of
the UCPCs arranged in four tiers, along the storage
facility, at the distance of 1 m from the protective wall
(at the height of 1 m from the ground, 40 cm thick wall
of concrete) is presented in Fig. 8. The DR maximum
value for the option under consideration is equal to one.
The activity of four-tier cask block placed at the
perimeter is assumed to be QJ = 1 (curve Identical
Q = 1). Correspondingly, the sum of the activities along
the row is 27. Optimal values of the activities QJ are
determined from the eqs. (2)–(5) and the condition, that
the sum of the activities is equal to 27. These values are
presented by the curve Wall in Fig. 11. The difference
between the spatial distribution of the DR, produced by
the casks with optimum activities (see curve Optimum
activities in Fig. 8), and that of the DR from the casks
with the same activity is quite insignificant (less than
3.5%). This is due to the rapid decrease of the DR
produced by a single container. The DR from one
UCPC is shown in Fig. 8 for containers No. 6, 11, 19,
and 27, whose activities are equal to 1, 0.8, 1.1, and 1.3,
respectively.
Fig. 8. Spatial distribution of the DR produced by
28 rows of UCPC along the storage facility at the
distance of 1 m from the protective wall
To calculate the radiation from casks on the
disciplinary fence of the security zone without a
protective wall, the arrangement of four-tier blocks in
pairs along the perimeter of the storage facility is
considered. This scheme allows comparing the DR with
both symmetric (see Fig. 5) and asymmetric (see Fig. 7)
loading of the UCPC. The arrangement of UCPCs in
pairs assumes the distance between the casks in a pair
L1 = 10 cm, and between the pairs of casks L2 =
100 cm. Fig. 9 shows the DR at the distance of 30 m,
produced by one UCPC with the symmetric and
asymmetric cask loading, subject to the distance along
the storage facility. The DR is calculated with the partial
contribution of radionuclides with account for the SRW
isotopic composition (see Table 2).
Fig. 9. Dependencies of the spline functions of the DR
from one UCPC on the distance along the storage
facility. Symmetric and asymmetric cask loading
From the above data it follows, that due to the
radiation shielding by the neighboring cask (see option
V1 Fig. 5), the DR at greater distances in this case is
lower than for the option V2.
The spatial distribution of the DRS, produced by 27
rows of UCPC in four tiers, along the storage facility,
are calculated for the asymmetric and symmetric cask
loading using the data presented in Fig. 9. For the
symmetric loading of the UCPC, the optimum values of
the QJ activities (see curve Air in Fig. 11) are
determined using the ratios (2)–(5) and the condition,
that the sum of the cask activities is 27. The spatial
distribution of the DR along the storage facility at the
distance of 30 m from the UCPCs arranged along
perimeter is shown in Fig. 10.
Fig. 10. The spatial distribution of the DR along the
storage facility, produced by 27 rows of the UCPCs
arranged along the perimeter at the distance of 30 m
from the storage facility perimeter
From the above data it follows that the arrangement
of the casks along the storage facility perimeter with the
optimal distribution of activities taken into account
allows reducing the DR maximum value on the
disciplinary fence of the security zone by ~ 20%. The
asymmetric loading of the UCPC with primary
cylindrical barrels filled with compacted SRW reduces
the DR at the disciplinary fence by ~ 2.5 times as
compared to the symmetrical, and by 2 times as
compared to the optimal loading.
Fig. 11. The optimum values of QJ activities for
protective wall and for the security zone (curve Air)
CONCLUSIONS
The technique is developed to calculate the external
radiation from a large-size source consisting of dozens
of radiating elements of the same geometry. The
radiating elements have the shape of concrete
rectangular cask into which cylindrical barrels filled
with compacted SRW are loaded. The Monte Carlo
method is used to calculate the spatial characteristics of
the radiation around the casks, produced by the definite
RW radionuclides, for different options of their
arrangement. Shielding by neighboring casks and
presence of an additional biological shielding is taken
into account.
The storage facilities are considered to be arranged
in the following way. More than one hundred casks are
assumed to be arranged in four tiers along the perimeter
of the storage facility. The DRs for these facilities are
determined using the data obtained by Monte Carlo
method. If the concrete casks with the same activity are
arranged along the perimeter of the storage facilities, the
DR along the perimeter of the storage facility with
biological shielding is shown to be almost uniform. For
the storage facility without shielding the DR has the
shape of an inverted parabola with its maximum in the
center. The DRs along the perimeter of the storage area
is minimized via variation of radiation rate from
different casks. For the storage without protection, the
arrangement of the sources with optimized activities
reduces the DR by ~ 20%. For the storage facility with
biological shielding, such an arrangement causes
negligible effect on the DR. The latter decreases only by
~ 3.5%. The most efficient method of reducing the DR
from a large-sized storage facility is a combination of
two actions. First, the casks should be arranged in pairs
with mirror placement along the perimeter of the cask
storage facility. Second, the primary barrels with RW
should be loaded into the casks with a shift towards one
of the corners (asymmetric loading). This method
reduces the DR by ~ 2.5 times.
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Article received 04.03.2019
КОМБИНИРОВАННЫЙ РАСЧЕТ ИЗЛУЧЕНИЙ ОТ ПОВЕРХНОСТНЫХ ХРАНИЛИЩ
РАО БОЛЬШИХ РАЗМЕРОВ НА ОСНОВЕ МЕТОДА МОНТЕ-КАРЛО
В.Г. Рудычев, Н.А. Азаренков, И.А. Гирка, Д.В. Рудычев, Е.В. Рудычев
Разработана методика уменьшения дозовых нагрузок, создаваемых приповерхностными источниками
излучений больших размеров, на периметре которых находятся десятки излучающих элементов одинаковой
геометрии. Излучающие элементы представляют собой бетонные прямоугольные контейнеры, в которых
размещены цилиндрические емкости с прессованными РАО. Выполнены расчеты пространственных
характеристик излучения методом Монте-Карло вокруг контейнера, создаваемого отдельными
радионуклидами РАО, с учетом экранирования соседними контейнерами при разных вариантах их
размещения, а также наличия дополнительной биозащиты.
КОМБІНОВАНИЙ РОЗРАХУНОК ВИПРОМІНЮВАНЬ ВІД ПОВЕРХНЕВИХ СХОВИЩ
РАВ ВЕЛИКИХ РОЗМІРІВ НА ОСНОВІ МЕТОДУ МОНТЕ-КАРЛО
В.Г. Рудичев, М.О. Азаренков, І.О. Гірка, Д.В. Рудичев, Є.В. Рудичев
Розроблено методику зменшення дозових навантажень, створюваних приповерхневими джерелами
випромінювань великих розмірів, на периметрі яких знаходяться десятки випромінюючих елементів
однакової геометрії. Випромінюючі елементи являють собою бетонні прямокутні контейнери, в яких
розміщені циліндричні ємності з пресованими РАВ. Виконано розрахунки просторових характеристик
випромінювання методом Монте-Карло навколо контейнера, створюваного окремими радіонуклідами РАВ,
з урахуванням екранування сусідніми контейнерами при різних варіантах їх розміщення, а також наявності
додаткового біозахисту.
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