Relationship between development of cracks, changes of substructure and strains state of tungsten irradiated by plasma heat loads relevant to ITER transient events
A paper reported the results of changes of structure and stressed state in tungsten targets irradiated by hydrogen plasma in quasi-stationary accelerator QSPA Kh-50 with heat loads relevant to ITER Edge Localized Modes (ELM). The pulsed plasma heat loads with duration of 0.25 ms and energy density u...
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Bazdyreva, S.V. Makhlaj, V.A. Malykhin, S.V. Pugachоv, A.T. 2015-05-13T15:19:23Z 2015-05-13T15:19:23Z 2014 Relationship between development of cracks, changes of substructure and strains state of tungsten irradiated by plasma heat loads relevant to ITER transient events / S.V. Bazdyreva, V.A. Makhlaj, S.V. Malykhin, A.T. Pugachоv // Вопросы атомной науки и техники. — 2014. — № 6. — С. 48-51. — Бібліогр.: 16 назв. — англ. 1562-6016 PACS: 52.40.Hf https://nasplib.isofts.kiev.ua/handle/123456789/81194 A paper reported the results of changes of structure and stressed state in tungsten targets irradiated by hydrogen plasma in quasi-stationary accelerator QSPA Kh-50 with heat loads relevant to ITER Edge Localized Modes (ELM). The pulsed plasma heat loads with duration of 0.25 ms and energy density up to 0.45 MJ m-2 was applied. Maximum number of irradiating pulses achieved 150. The correlation between the structure, substructure the stressed state of the surface layers changing and cracking processes occurring as results of plasma irradiation was studied. The effect of excess vacancies and vacancy complexes in formation of the crack nucleation at the stage of the residual compressive macro-stress annealing in the initial structure was evaluated. The initial dislocation density is determined by the development of internal stresses and the cracking process in the target surface layers. PACS: 52.40.Hf Представлены результаты изменения структуры, субструктуры и напряжённого состояния вольфрамовых мишеней, облученных водородной плазмой на квазистационарном ускорителе КСПУ Х-50, с тепловыми нагрузками, близкими к ИТЭР ELM. Применялась импульсная плазменная тепловая нагрузка с длительностью импульса 0,25 мс и плотностью энергии до 0,45 МДж/м2. Максимальное число облучающих импульсов достигало 150. Изучена взаимосвязь между изменением структуры, субструктуры, напряжённого состояния поверхностных слоёв и процессов растрескивания в них, происходящих вследствие плазменного облучения. Установлена определяющая роль избыточных вакансий и вакансионных комплексов в образовании зародышей трещин на стадии отжига остаточных макронапряжений сжатия исходной структуры. Определен вклад исходной плотности дислокаций в развитие внутренних напряжений и процессов растрескивания поверхностных слоёв мишеней. Представлено результати зміни структури, субструктури та напруженого стану вольфрамових мішеней, опромінених водневою плазмою на квазістаціонарному прискорювачі КСПУ Х-50, з тепловими навантаженнями, близькими до ІТЕР ELM. Застосовувалось імпульсне плазмове теплове навантаження з тривалістю імпульсу 0,25 мс і густиною енергії до 0,45 МДж/м2. Максимальне число імпульсів опромінення становило 150. Вивчено взаємозв'язок між зміною структури, субструктури, напруженого стану поверхневих шарів і процесів розтріскування в них, що відбуваються внаслідок опромінення. Встановлена визначальна роль надлишкових вакансій і вакансійних комплексів в утворенні зародків тріщин на стадії відпалювання залишкових макронапружень стиснення вихідної структури. Визначено внесок вихідної густини дислокацій в розвиток внутрішніх напружень і процесів розтріскування поверхневих шарів мішеней. en Національний науковий центр «Харківський фізико-технічний інститут» НАН України Вопросы атомной науки и техники ИТЭР и приложения для термоядерного реактора Relationship between development of cracks, changes of substructure and strains state of tungsten irradiated by plasma heat loads relevant to ITER transient events Взаимосвязь между развитием трещин, изменениями характеристик субструктуры и напряженного состояния вольфрама, облучённого плазменными потоками, соответствующими переходным явлениям в ИТЭР Взаємозв'язок між розвитком тріщин, зміною характеристик субструктури і напруженого стану вольфраму, опроміненого плазмовими потоками, відповідними до перехідних явищ в ITEР Article published earlier |
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Digital Library of Periodicals of National Academy of Sciences of Ukraine |
| collection |
DSpace DC |
| title |
Relationship between development of cracks, changes of substructure and strains state of tungsten irradiated by plasma heat loads relevant to ITER transient events |
| spellingShingle |
Relationship between development of cracks, changes of substructure and strains state of tungsten irradiated by plasma heat loads relevant to ITER transient events Bazdyreva, S.V. Makhlaj, V.A. Malykhin, S.V. Pugachоv, A.T. ИТЭР и приложения для термоядерного реактора |
| title_short |
Relationship between development of cracks, changes of substructure and strains state of tungsten irradiated by plasma heat loads relevant to ITER transient events |
| title_full |
Relationship between development of cracks, changes of substructure and strains state of tungsten irradiated by plasma heat loads relevant to ITER transient events |
| title_fullStr |
Relationship between development of cracks, changes of substructure and strains state of tungsten irradiated by plasma heat loads relevant to ITER transient events |
| title_full_unstemmed |
Relationship between development of cracks, changes of substructure and strains state of tungsten irradiated by plasma heat loads relevant to ITER transient events |
| title_sort |
relationship between development of cracks, changes of substructure and strains state of tungsten irradiated by plasma heat loads relevant to iter transient events |
| author |
Bazdyreva, S.V. Makhlaj, V.A. Malykhin, S.V. Pugachоv, A.T. |
| author_facet |
Bazdyreva, S.V. Makhlaj, V.A. Malykhin, S.V. Pugachоv, A.T. |
| topic |
ИТЭР и приложения для термоядерного реактора |
| topic_facet |
ИТЭР и приложения для термоядерного реактора |
| publishDate |
2014 |
| language |
English |
| container_title |
Вопросы атомной науки и техники |
| publisher |
Національний науковий центр «Харківський фізико-технічний інститут» НАН України |
| format |
Article |
| title_alt |
Взаимосвязь между развитием трещин, изменениями характеристик субструктуры и напряженного состояния вольфрама, облучённого плазменными потоками, соответствующими переходным явлениям в ИТЭР Взаємозв'язок між розвитком тріщин, зміною характеристик субструктури і напруженого стану вольфраму, опроміненого плазмовими потоками, відповідними до перехідних явищ в ITEР |
| description |
A paper reported the results of changes of structure and stressed state in tungsten targets irradiated by hydrogen plasma in quasi-stationary accelerator QSPA Kh-50 with heat loads relevant to ITER Edge Localized Modes (ELM). The pulsed plasma heat loads with duration of 0.25 ms and energy density up to 0.45 MJ m-2 was applied. Maximum number of irradiating pulses achieved 150. The correlation between the structure, substructure the stressed state of the surface layers changing and cracking processes occurring as results of plasma irradiation was studied. The effect of excess vacancies and vacancy complexes in formation of the crack nucleation at the stage of the residual compressive macro-stress annealing in the initial structure was evaluated. The initial dislocation density is determined by the development of internal stresses and the cracking process in the target surface layers.
PACS: 52.40.Hf
Представлены результаты изменения структуры, субструктуры и напряжённого состояния вольфрамовых мишеней, облученных водородной плазмой на квазистационарном ускорителе КСПУ Х-50, с тепловыми нагрузками, близкими к ИТЭР ELM. Применялась импульсная плазменная тепловая нагрузка с длительностью импульса 0,25 мс и плотностью энергии до 0,45 МДж/м2. Максимальное число облучающих импульсов достигало 150. Изучена взаимосвязь между изменением структуры, субструктуры, напряжённого состояния поверхностных слоёв и процессов растрескивания в них, происходящих вследствие плазменного облучения. Установлена определяющая роль избыточных вакансий и вакансионных комплексов в образовании зародышей трещин на стадии отжига остаточных макронапряжений сжатия исходной структуры. Определен вклад исходной плотности дислокаций в развитие внутренних напряжений и процессов растрескивания поверхностных слоёв мишеней.
Представлено результати зміни структури, субструктури та напруженого стану вольфрамових мішеней, опромінених водневою плазмою на квазістаціонарному прискорювачі КСПУ Х-50, з тепловими навантаженнями, близькими до ІТЕР ELM. Застосовувалось імпульсне плазмове теплове навантаження з тривалістю імпульсу 0,25 мс і густиною енергії до 0,45 МДж/м2. Максимальне число імпульсів опромінення становило 150. Вивчено взаємозв'язок між зміною структури, субструктури, напруженого стану поверхневих шарів і процесів розтріскування в них, що відбуваються внаслідок опромінення. Встановлена визначальна роль надлишкових вакансій і вакансійних комплексів в утворенні зародків тріщин на стадії відпалювання залишкових макронапружень стиснення вихідної структури. Визначено внесок вихідної густини дислокацій в розвиток внутрішніх напружень і процесів розтріскування поверхневих шарів мішеней.
|
| issn |
1562-6016 |
| url |
https://nasplib.isofts.kiev.ua/handle/123456789/81194 |
| citation_txt |
Relationship between development of cracks, changes of substructure and strains state of tungsten irradiated by plasma heat loads relevant to ITER transient events / S.V. Bazdyreva, V.A. Makhlaj, S.V. Malykhin, A.T. Pugachоv // Вопросы атомной науки и техники. — 2014. — № 6. — С. 48-51. — Бібліогр.: 16 назв. — англ. |
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ISSN 1562-6016. ВАНТ. 2014. №6(94)
48 PROBLEMS OF ATOMIC SCIENCE AND TECHNOLOGY. 2014, №6. Series: Plasma Physics (20), p. 48-51.
RELATIONSHIP BETWEEN DEVELOPMENT OF CRACKS, CHANGES
OF SUBSTRUCTURE AND STRAINS STATE OF TUNGSTEN
IRRADIATED BY PLASMA HEAT LOADS RELEVANT TO ITER
TRANSIENT EVENTS
S.V. Bazdyreva
1
, V.A. Makhlaj
2
, S.V. Malykhin
1
, A.T. Pugachоv
1
1
National Technical University “Kharkiv Polytechnical Institute”, Kharkiv, Ukraine;
2
Institute of Plasma Physics NSC KIPT, Kharkov, Ukraine
E-mail: malykhin@kpi.kharkov.ua; makhlay@kipt.kharkov.ua
A paper reported the results of changes of structure and stressed state in tungsten targets irradiated by hydrogen
plasma in quasi-stationary accelerator QSPA Kh-50 with heat loads relevant to ITER Edge Localized Modes (ELM).
The pulsed plasma heat loads with duration of 0.25 ms and energy density up to 0.45 MJ m
-2
was applied. Maximum
number of irradiating pulses achieved 150. The correlation between the structure, substructure the stressed state of
the surface layers changing and cracking processes occurring as results of plasma irradiation was studied. The effect
of excess vacancies and vacancy complexes in formation of the crack nucleation at the stage of the residual
compressive macro-stress annealing in the initial structure was evaluated. The initial dislocation density is
determined by the development of internal stresses and the cracking process in the target surface layers.
PACS: 52.40.Hf
INTRODUCTION
One of the important issues determining the life-time
the components and safety of tokamak-reactor ITER is
performance of plasma-facing materials and
components under repetitive plasma loads to the first
wall and divertor of fusion reactor. Tungsten has been
chosen as the plasma-facing material for ITER divertor
due to high melting and sputtering thresholds. Behavior
of tungsten under plasma heat loads relevant to ITER
current disruption and edge localized modes (ELMs)
still requires comprehensive experimental study [1].
The formation of surface cracks and development of
specific morphology on the surface of tungsten targets
under the repetitive plasma heat loads relevant to ITER
conditions can be influenced by the structural state of
exposed targets [2-4]. The size of the crystallites and
their shape, the density and distribution of defects in the
crystal structure, the presence of texture, lattice spacing
should be considered as the characteristics of the perfection
of target structure. In addition, the stresses can play an
important role in damage of exposed targets [5-8].
In this work, the analysis of relationship between
formation of surface cracks, the evolution of internal
macro- and micro- strains, initial structural, stressed
state of the tungsten have been carried out for a large
number of targets. The main aim of this paper is
determination of structural parameters and their
influence on surface cracks formation. The evolution of
the internal stresses and correlation between stress level
and cracking threshold are also discussed.
1. SAMPLES AND EXPERIMENTAL
EQUIPMENT
Pure tungsten (W) samples (99, 99 %) have been
exposed by hydrogen plasma in the quasi-stationary
plasma accelerator QSPA Kh-50 [9]. Main parameters
of plasma streams were as follows: energy of particles
up to 400 eV, the maximum plasma pressure 0.32 MPa,
the pulse duration 0.25 ms. Plasma heat load to the
samples surface did not exceed 0.45 MJ/m
2
. The
samples were kept at room temperature before each
plasma pulse. Maximum number of exposed pulses was
150. The rolled, sintered, single forged, double forged
targets have been used in these experiments [6, 7, 10, 11].
Surface analysis was carried out with an optical
microscope MMR-4 equipped with a CCD camera and
Scanning Electron Microscopy (SEM) JEOL JSM-6390.
X-ray diffraction (XRD) has been used to study
structure, substructure and stress state of W targets.
-2 scans were performed using a monochromatic Cu-
Kα radiation [12-15]. Computer processing of the
experimental diffraction patterns was performed using
the New profile 3.5 software package. The analysis of
diffraction peaks intensity, profiles, width (В) and
angular positions (2 ) was applied to evaluate texture,
coherent scattering region size.
Residual macro-stresses (σ) and the lattice parameter
in the stress free state (a0) were determined using а-
sin
2
ψ -plots by the peaks (400) or (321) located in the
precision area of angles (Fig. 1). Dashed line showed
the stress free cross section according to which a0 was
determined. If lattice parameter in the stress free state
(a0) is less than the corresponding reference value
(aref=0.3165 nm) then a lot of vacancies presents in
structure. If a0>aref the surplus interstitial atoms are
observed in structure.
The asymmetry of the profile was also determined.
The asymmetry parameter (δВ) was given for
quantitative characteristics of asymmetry as:
B = ( Bleft Bright )/( Bleft+Bright ), where Bleft. – left part
of width at half-height, Bright - right part of width at half-
height (Fig. 2).
mailto:malykhin@kpi.kharkov.ua
mailto:makhlay@kipt.kharkov.ua
ISSN 1562-6016. ВАНТ. 2014. №6(94) 49
0.6 0.80.40.2
0.3168
0.3164
0.3156
5 4
3
a
0
,
n
m
sin
2
1
2
0.3160
0.0
Fig. 1. Example of а-sin
2
ψ-plots for the sample in
the initial state single forged sample (1) and after
irradiation by 5 plasma pulses of 0.45 MJ/m
2
different
samples: double forged (2), single forged (3), rolled
single forged (4) and rolled (5)
According to the theory of scattering [15] the
diffraction peak should be symmetrical. Asymmetrical
profile can be considered as superposition of two
symmetrical peaks. One of them is the theoretical main
peak and second diffusion maximum is associated with
defects of the structure (Fig. 3). Generally, the width (B)
of the profile is proportional to the number of line
defects (dislocations) in the structure. The asymmetry
(δВ) is attributed by the presence of complexes of point
defects. The sign of В is caused by the type of defects:
vacancies ( В>0) or interstitial atoms ( В<0).
153 154 155
0
100
200
B
right
in
te
n
s
it
y
,
p
u
ls
./
s
2 , deg.
B
left
1/2 I
max
Fig. 2. The example of the definition of asymmetry
parameter ( В) for diffraction line (400)
Analysis of the average coherence length (associated
with the density of dislocation in the walls of grains)
and the value of the average micro strain (density of
chaotically distributed dislocations inside the coherence
length) has been carried out by the approximation
method [12-14]. Fine-grained diamond powder was
used as a reference sample for exception of instrumental
and physical broadening. Since tungsten is among
isotropic materials, we used from 4 till 6 -reflections for
calculations.
2. EXPERIMENTAL RESULTS
The value of the residual macro stresses, the lattice
period in stress free state, the half-width (B) of peak,
and asymmetry were rather different for the samples
obtained by different technologies [6, 7, 10, 11].
2.1. INITIAL STATE
In initial state the samples have different dependence
of residual macro stresses ( init) and parameter В
versus averaged density of linear defects (B) in the
sample (Fig. 4). At low density of defects, residual
compressive macro stresses achieved 300 MPa. The
dependence init(В) is near to the linear. The tensile
stresses up to 100 MPa are registered at high density of
linear defects.
a
b
b
Fig. 3. Diffraction peak asymmetry with additional
diffuse maximum before irradiation (a)and after plasma
irradiation (b); experimental diffraction peak (1), main
diffraction peak after computer processing(2),
additional diffuse maximum (3)
6 8 10 12 14 16
-300
-200
-100
0
100
in
it
.,
M
P
a
B*10
3
, rad
0
5
10
15
B
,%
1
2
3 4 5
Fig. 4. Dependences of initial macro stresses and the
averaged asymmetry parameter v.s. width of the
diffraction profile (400) for different samples
The dependence В(В) is not monotonic. Maximal
asymmetry ( В 15 %) is observed at the intermediate
values of compressive stresses ( 200 MPa) and
relatively small density of dislocations (B 9×10
3
rad).
50 ISSN 1562-6016. ВАНТ. 2014. №6(94)
The low positive asymmetry ( В ~ 5%) is associated
with maximum of compressive stresses ( init -300 MPa)
and the small density of dislocations (B 9×10
3
rad).
The profile asymmetry is absent ( В 0) at high density
of dislocations (B>1.2×10
4
rad) and at tensile stresses.
According to [15] the positive sign of В (i.e.
Bleft> Bright, as it shown in Fig. 3,a.) indicates the excess
of vacancy complexes in the structure of sample.
Thus, tensile stresses accompanied by high density
of linear defects led to the migration of vacancy
complexes. Those complexes are stable at presence of
compressive stresses and low dislocation density
It should be mentioned, that the average size of
coherent area is practically the same (from 150 to
200 nm) for different samples. For such size the density
of dislocations in boundaries varies in the range of
(0.8…2.0)·10
10
cm
-2
.
2.2. PARAMETERS OF STRUCTURE AFTER
PLASMA IRRADIATION
The initial compressive stresses annealed as a result
of irradiation. The tensile residual stresses of different
value are appeared in exposed surface [6, 11, 16]. The
sign of asymmetry parameter changes from positive to
negative (Fig. 4.). The value of В rises with increasing
of number of irradiation pulses.
The level of stresses caused by plasma irradiation
depends on the density of chaotically distributed
dislocations (Fig. 5). The maximal density of
dislocations inside of the crystallites (up to
ρ 6×10
9
cm
-2
) is observed at higher level of residual
tensile macro stresses ( 800 MPa).
0 4 8 400 800
200
400
600
800
,
M
P
a
*10
-7
,cm
-2
Fig. 5. Dependence of residual tensile macro stresses
v.s. the density of initial chaotically distributed
dislocations after irradiation
It should be noted that the lattice spacing a0 is less
than reference lattice spacing a0 of pure tungsten aref
[14]. This fact is caused by the presence of excess
vacancies in the structure. The a0 rises with increasing
of irradiation dose that indicates to annealing of vacancy
on dislocation sinks (see Fig. 1). The level of lattice
spacing increasing is proportional to dislocation density
in the initial state.
For target with highest density of line defects, the
profile width is noticeably decreased after plasma
irradiation. Such changes in the peak width could be
attributed by improvement of substructure. For samples,
which have low density of line defects, width B
increases (up to 30 %) as result of plasma exposures.
2.3. CORRELATION BETWEEN PARAMETERS
OF STRUCTURE AND APPEARING OF CRACKS
The analysis of correlation between sign of initial
asymmetry, residual macro stresses and appearance of
first surface cracks has been performed for different
number of plasma pulses. For small number of
irradiation pulses (1…5) , appearance of the first cracks
is observed in sample with structural state corresponds
to point 1 in Fig. 3. In this case, many vacancy complex
( B 15 %) and compressive stresses ( 250 MPa)
are observed.
The slightly incising of irradiation pulses number is
necessary for the crack formation in the samples with
the structural state corresponding to point 2 (see Fig. 4).
For the samples with high dislocation density and
tensile stresses without point defects complexes ( В =
0), that corresponds to points 4 and 5 (see Fig. 4.), the
cracks are not observed at all or they appeared for rather
large number of exposed pulses (N 100).
Thus, it should be noted that crack occurs mainly in
the samples with high content of excess vacancies and
vacancy complexes. The last are particularly stable
under action of compressive macro stresses. The
relaxation of the initial compressive stress and the
formation of tensile stress occur after 1…2 pulses of
plasma exposure with a load of more than 0.2 MJ / m
2
as it is shown in previous studies [6, 10, 11]. We assume
that the thermal effect on the surface layers promotes
coalescence of vacancy complexes, annealing of
vacancies and nucleus of crack, which also can be
considered as a mechanism of compressive stresses
relaxation. Small quantity of internal vacancy sinks as
dislocations and dislocation loops contributes to this
process. High dislocation density, the absence of
vacancy complexes and initial tensile stresses prevent
formation of cracks. The dislocation density ρ 10
8
сm
-2
is sufficient for the effective absorption of excess
vacancies and stress annealing by moving dislocations.
The observed stress saturation (see Fig. 5), is in
agreement with this result.
CONCLUSIONS
The studies of structure changes and stressed state in
tungsten targets irradiated by hydrogen plasma in quasi-
stationary accelerator QSPA Kh-50 with heat loads
relevant to ITER ELMs have been carried out. The
plasma heat loads have pulse duration of 0.25 ms and
the energy density deposited to the surface up to
0.45 MJ •m
-2
.
The determining role of excess vacancies and
vacancy complexes was evaluated for formation of
cracks at the stage of annealing the residual compressive
macro-stress that presented in the initial structure.
The contribution of initial dislocation density to
development of internal stresses and the cracking
process is found to be determining for tungsten surface
layers exposed by powerful plasma streams. It was
revealed that the level of tensile macro-stresses is
ISSN 1562-6016. ВАНТ. 2014. №6(94) 51
proportional to initial density of linear defects and it
inversely proportional to the content of vacancies and
vacancy complexes. The crack development reduces
such stresses.
The sorption properties of structural linear defects
with regards to initial excess vacancy depend on the
orientation of dislocations with regards both to the
surface and to the axes of the residual stresses, and also
on their value and sign.
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Article received 17.10.2014
ВЗАИМОСВЯЗЬ МЕЖДУ РАЗВИТИЕМ ТРЕЩИН, ИЗМЕНЕНИЯМИ ХАРАКТЕРИСТИК
СУБСТРУКТУРЫ И НАПРЯЖЕННОГО СОСТОЯНИЯ ВОЛЬФРАМА, ОБЛУЧЁННОГО
ПЛАЗМЕННЫМИ ПОТОКАМИ, СООТВЕТСТВУЮЩИМИ ПЕРЕХОДНЫМ ЯВЛЕНИЯМ В ИТЭР
С.В. Баздырева, В.А. Махлай, С.В. Малыхин , А.Т. Пугачев
Представлены результаты изменения структуры, субструктуры и напряжённого состояния вольфрамовых
мишеней, облученных водородной плазмой на квазистационарном ускорителе КСПУ Х-50, с тепловыми
нагрузками, близкими к ИТЭР ELM. Применялась импульсная плазменная тепловая нагрузка с
длительностью импульса 0,25 мс и плотностью энергии до 0,45 МДж/м
2
. Максимальное число облучающих
импульсов достигало 150. Изучена взаимосвязь между изменением структуры, субструктуры, напряжённого
состояния поверхностных слоёв и процессов растрескивания в них, происходящих вследствие плазменного
облучения. Установлена определяющая роль избыточных вакансий и вакансионных комплексов в
образовании зародышей трещин на стадии отжига остаточных макронапряжений сжатия исходной
структуры. Определен вклад исходной плотности дислокаций в развитие внутренних напряжений и
процессов растрескивания поверхностных слоёв мишеней.
ВЗАЄМОЗВ'ЯЗОК МІЖ РОЗВИТКОМ ТРІЩИН, ЗМІНОЮ ХАРАКТЕРИСТИК
СУБСТРУКТУРИ І НАПРУЖЕНОГО СТАНУ ВОЛЬФРАМУ, ОПРОМІНЕНОГО ПЛАЗМОВИМИ
ПОТОКАМИ, ВІДПОВІДНИМИ ДО ПЕРЕХІДНИХ ЯВИЩ В ITEР
С.В. Баздирєва, В.O. Махлай, С.В. Малихін, А.Т. Пугачов
Представлено результати зміни структури, субструктури та напруженого стану вольфрамових мішеней,
опромінених водневою плазмою на квазістаціонарному прискорювачі КСПУ Х-50, з тепловими
навантаженнями, близькими до ІТЕР ELM. Застосовувалось імпульсне плазмове теплове навантаження з
тривалістю імпульсу 0,25 мс і густиною енергії до 0,45 МДж/м
2
. Максимальне число імпульсів опромінення
становило 150. Вивчено взаємозв'язок між зміною структури, субструктури, напруженого стану поверхневих
шарів і процесів розтріскування в них, що відбуваються внаслідок опромінення. Встановлена визначальна
роль надлишкових вакансій і вакансійних комплексів в утворенні зародків тріщин на стадії відпалювання
залишкових макронапружень стиснення вихідної структури. Визначено внесок вихідної густини дислокацій
в розвиток внутрішніх напружень і процесів розтріскування поверхневих шарів мішеней.
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