Development of a low background pulsed generator of intermediate energy range neutrons for remote detection of fissile materials
A structure of radiation shielding for a low background pulsed generator of intermediate energy range neutrons was developed on the basis of calculations and the data obtained in the model experiments, and limit parameters for remote detection of fissile materials using this generator were determi...
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| Date: | 2004 |
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Національний науковий центр «Харківський фізико-технічний інститут» НАН України
2004
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| Cite this: | Development of a low background pulsed generator of intermediate energy range neutrons for remote detection of fissile materials / V. Chornyi, A. Frolov, G. Tsepilov, V. Dubina, A. Chornyi, V. Solovyov // Вопросы атомной науки и техники. — 2004. — № 2. — С. 24-26. — Бібліогр.: 5 назв. — англ. |
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Digital Library of Periodicals of National Academy of Sciences of Ukraine| _version_ | 1859907190877323264 |
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| author | Chornyi, V. Frolov, A. Tsepilov, G. Dubina, V. Chornyi, A. Solovyov, V. |
| author_facet | Chornyi, V. Frolov, A. Tsepilov, G. Dubina, V. Chornyi, A. Solovyov, V. |
| citation_txt | Development of a low background pulsed generator of intermediate energy range neutrons for remote detection of fissile materials / V. Chornyi, A. Frolov, G. Tsepilov, V. Dubina, A. Chornyi, V. Solovyov // Вопросы атомной науки и техники. — 2004. — № 2. — С. 24-26. — Бібліогр.: 5 назв. — англ. |
| collection | DSpace DC |
| container_title | Вопросы атомной науки и техники |
| description | A structure of radiation shielding for a low background pulsed generator of intermediate energy range neutrons
was developed on the basis of calculations and the data obtained in the model experiments, and limit parameters for
remote detection of fissile materials using this generator were determined and are presented in this paper. The magnetically insulated diode structure and the radiation shielding geometry were optimized in accordance with the performed calculations.
У даній роботі представлено конструкцію радіаційного захисту для низькофонового імпульсного
генератора проміжних енергій, розробленого на основі комп'ютерних розрахунків і даних модельних
експериментів, а також приведені граничні параметри дистанційного виявлення подільчих матеріалів за
допомогою цього генератора. Конструкція магнітно-ізольованого діода і геометрія радіаційного захисту
були оптимізовані відповідно до проведених обчислень.
В данной статье представлено описание конструкции радиационной защиты для низкофонового импульсного генератора промежуточных энергий, разработанного на основе компьютерных вычислений и данных модельных экспериментов, а также приведены предельные параметры дистанционного обнаружения делящихся материалов с использованием этого генератора. Конструкция магнитно-изолированного диода и
геометрия радиационной защиты были оптимизированы в соответствии с проведенными вычислениями.
|
| first_indexed | 2025-12-07T16:01:00Z |
| format | Article |
| fulltext |
DEVELOPMENT OF A LOW BACKGROUND PULSED GENERATOR
OF INTERMEDIATE ENERGY RANGE NEUTRONS FOR REMOTE
DETECTION OF FISSILE MATERIALS *
V. Chornyi, A. Frolov, G. Tsepilov, V. Dubina, A. Chornyi, V. Solovyov
The V.N. Karazin Kharkov National University, PO Box 2096, 61108, Kharkov, Ukraine
E-mail: chorny@pht.univer.kharkov.ua
A structure of radiation shielding for a low background pulsed generator of intermediate energy range neutrons
was developed on the basis of calculations and the data obtained in the model experiments, and limit parameters for
remote detection of fissile materials using this generator were determined and are presented in this paper. The mag-
netically insulated diode structure and the radiation shielding geometry were optimized in accordance with the per-
formed calculations.
PACS: 28.50.Ma
1. INTRODUCTION
Topicality of solving the problems of fissile material
reliable detection demands some new active methods to
be developed. One of such active methods is the tech-
nique of pulsed illumination of an object with neutrons
of intermediate energy range. Examples of sub-MeV
neutron utilization for 235U and 239U detection and recog-
nition were described in a number of papers [1,2]. How-
ever, in all the described experiments the source, object,
and detector of the induced radiation were positioned
close to one another. But the use of a high-power pulsed
source allows to position it at some distance from the
object under examination and to use the time-of-flight
technique for the object recognition.
Principal feasibility as well as the advantages of us-
ing the technique of an object illumination with a high-
power pulse of sub-MeV neutrons for fissile material re-
mote detection is discussed in [3].
Preliminary modeling experiments carried out at the
High-Current Electronics Laboratory of Kharkiv Na-
tional University have shown especial promise of the
proposed technique [4]. The technique provided effec-
tive recording of the signals induced by scattering neu-
trons of the model probing pulse, simulating fission
neutrons, at the distance of some meters.
The factors limiting the technique potentialities that
were found out during the experiments may be account-
ed mainly for the radiation background effect on the de-
tectors produced by the neutron generator. The neutron
generator operation was accompanied by intensive radi-
ation background resulting from both the
bremsstrahlung radiation of electron component of the
ion diode current and the nuclear reactions induced by
an ion beam and neutrons.
To achieve effective remote probing a high-power
pulsed neutron source with low radiation background is
required. This paper is devoted to the problem con-
cerned with the research and development of a sub-MeV
neutron generator of this kind.
2. NEUTRON GENERATOR
The generator of high-power neutron illumination
pulses can be built on the basis of a high-current pulsed
proton accelerator with using Li7(p,n)Be7 and T(p,n)3He
reactions. For the comparable neutron yields from these
reactions, realization of the generator based on the use
of the first (Li7(p,n)Be7) reaction has some disadvan-
tages:
to build a 2.2-MeV magnetically insulated diode is
more difficult;
to attenuate bremsstrahlung background at a higher
quantum energy is more difficult;
the neutron pulse spectrum is more spread-out than
when the generator operates using the second
(T(p,n)3He ) reaction.
Therefore, the neutron generator under development is
based on the T(p,n)4He reaction. Some other nuclear re-
actions allowing to generate neutron pulses may also be
used at the stage of the facility adjustment and model
experiments.
The T(p,n)3He reaction-based neutron generator op-
eration is accompanied by essential (of the order of
0.035%) γ-quanta yield at the energy of 20 MeV from
the T(p,γ)4He reaction [5]. It is known as well, that deu-
terium natural occurrence is 0.01%, and so, the
T(d,n)4He reaction may yield 107 neutron/pulse with the
energy of 14 MeV at the proton beam current of 50…
100 kA.
The greater portion of the generated neutron flow
may also cause background when directly hitting the de-
tector or being converted into γ-quanta of radiation cap-
ture on the device structural units (see Fig.1, curve 2).
Depending on the scintillator irradiation dose rate
the scintillator luminescence intensity may be strong
enough and prevent the response signal from being
recorded (see Fig.1 curve 1).
Various versions of radiation shielding were tried in
the experiments. As a rule it was made of alternate lay-
ers of paraffin, lead, and polyethylene.
Operation efficiency of shielding of this kind may be
seen from comparison of curves 2 and 3 in Fig.1.
* Supported by US DTRA and EU through the Science and Technology Center in Ukraine under Project # 329
___________________________________________________________
PROBLEMS OF ATOMIC SIENCE AND TECHNOLOGY. 2004. № 2.
Series: Nuclear Physics Investigations (43), p.24-26. 24
mailto:chorny@pht.univer.kharkov.ua
Fig.1. Shapes of the scintillation detector response sig-
nals: 1 – signal measured without shielding;
2 – signal detected after the lead shielding between the
detector and the generator had been mounted;
3 – neutron response signal clearly seen after the back-
ground neutron shielding had been mounted
The following requirements to the neutron generator
were worked out on the grounds of the accumulated ex-
perimental data:
Maximally narrow neutron energy range
(En ≈ 350 keV)
Neutron output per pulse should be no less than
109 neutron/pulse;
The levels of radiation background and
bremsstrahlung must not exceed the response signal
value at the points where the response signal detec-
tors are placed.
The generator must provide stable neutron pulse
characteristics during a long period of its operation.
According to the requirements to the neutron pulse
the tritium target should contain no less than 1.69⋅
1019 nuclear/сm2. The proton beam energy is to be
1.2 MeV, its current – 50 kA, and pulse duration
~100 ns.
High-performance ion diode insulated by the exter-
nal magnetic field will provide parameters specified for
the proton beam.
3. RADIATION BACKGROUND
CALCULATION
To reduce the electron escape in the diode, which
can induce bremsstrahlung, diode fields were calculated,
and electrode geometry was determined, as well as de-
mands to the insulating field producing coils were de-
fined.
Simulation of electron trajectories in the ion diode
allowed determining the most probable places for the
electrons to hit the structural units. Because of the ne-
cessity to reduce the bremsstrahlung background these
parts of the diode must be made of low-Z materials.
Moreover, all the unfilled places in the diode must be
filled with materials that would efficiently decrease the
radiation background, i.e., borated polyethylene and
lead. The gamma-background produced in the process
of the unused neutron interaction with the generator
units, most of all with those made of copper and iron,
was calculated.
The calculations were performed using the following
parameters:
the model fissile material mass – 200 grams;
the distance from the neutron generator to the mod-
el – 5 meters;
scintillator with dimensions of 100×100×20 cm was
used as a detector and was arranged at the distance
of 2 meters from the model;
neutron yield per pulse – Y = 109.
The signal value calculation results are given in Ta-
ble 1 in energetic units. The first column presents the
values of signals from the generator without radiation
shielding. In the second column the values of signals de-
tected when 4-cm thick moderator (polyethylene) was
mounted around the neutron generator are given. The
last column presents the values of the model response.
Increase of γ-radiation signal (second column) is deter-
mined by increase of the radiation capture reaction
cross-section (Fe(n,γ)) due to the neutron moderation in
polyethylene. Here the neutron signal decreases insuffi-
ciently. Further increasing of the moderator thickness up
to 8 cm results in sharp reduction of the neutron signal
and not great decrease of the γ-radiation signal level (the
third column in Table). When a radiation shielding in
the form of 16-cm thick moderator plus 16-cm thick
lead is mounted around the neutron generator the back-
ground signal value (the forth column in the Table) be-
comes smaller than the model response signal value (the
last column in Table).
Re
sp
on
se
ty
pe Thickness of Moderator, cm
hn=0 hn=4 hn=8 hn=16 +
hPb=16
M
od
el
re
sp
on
se
N
eu
tro
n
re
sp
on
se
[M
eV
]
3.2e4 2.9e3 241 1.5 12
G
am
m
a-
re
sp
on
se
[M
eV
]
2.3e4 3.78e4 9e3 1.16 12.65
Complete suppression of gamma-background is im-
possible because of the necessity to leave the channel,
meant for protons to drift towards the target, open,
whereas the neutron output from the target forward can
be effectively collimated.
To solve the problem of the forward neutron flow
collimation one must study carefully the neutron flow
transformation in space. So careful studying is neces-
sary to achieve optimum between the neutron flow den-
___________________________________________________________
PROBLEMS OF ATOMIC SIENCE AND TECHNOLOGY. 2004. № 2.
Series: Nuclear Physics Investigations (43), p.24-26.25
sity and the irradiated area size, because the additional
area irradiated by a neutron flow in the region of the ob-
ject position is an additional background source.
The obtained values of γ-radiation background en-
abled to determine minimal and maximal distances for
remote detection (see Fig.2.). Minimal distances are de-
termined by the necessity to separate the γ-radiation re-
sponse in time from scattering neutrons and fission neu-
trons. Maximum distances are correlated as signal/back-
ground ratio.
Fig.2. Calculations of limit detection distances depen-
dence on neutron output per pulse (Y), and 235U mass
(m)
4. SUMMARY
The conception for the neutron generator radiation
shielding presented in this paper has been designed for
specific geometry of the experiment on fissile material
detection simulating a stationary detecting complex. In
our case there are no strict limitations as for the com-
plex overall dimensions and weight that are generally
determined by the generator and radiation shielding
structure.
When the detecting complex on a mobile platform is
designed the probing neutron source and the response
signal detector should be placed close to one another.
But, if even being so, merely increase of the moderator
or absorber thickness cannot solve the problem of the
radiation background suppression because of limitations
as to the complex overall dimensions and weight. Some
other ways to solve the problem of the radiation back-
ground suppression are required for this case. For in-
stance, to use the proton accelerator units as shielding –
with water and oil in the forming line as a moderator,
and the metallic components in combination with boron,
cadmium, and lead as an absorber.
REFERENCES
1. V.V.Frolov. Nuclear-Physical Methods of Fission
Material Monitoring. 1989, M: Energoizdat, p.93
(Rus.).
2. V.P.Kovalev. Secondary Emissions of Electron Ac-
celerators. 1979. M: Atomizdat, p.166 (Rus.).
3. I.I.Zaliubovsky, A.A.Lomako, O.N.Morgun, V.V.-
Chorny. Method for Active Remote Detection of
Nuclear Warheads // Atomnaya Energia (Rus.).
1993, v.74, No.6, p.497-502.
4. V.V.Chornyi, A.I.Frolov, G.V.Tsepilov, V.N.Dubi-
na, A.V.Chornyi, S.A.Pis’menetskyi, V.S.Solovy-
ov, I.V.Ushakov. Employment of the Pulsed-Ion
Accelerator as a High-Power Intermediate Energy
Neutron Generator for Remote Detection of Nucle-
ar Explosives // IEEE Trans. Plasma Sci. 2002,
v.30, No.5, p.1827-1832.
5. V.M.Pasechnik. Dozimetry of moderate energy
neutrons (0.01...10 MeV). Kiev: Naukova Dumka,
1972, p.178.
РАЗРАБОТКА НИЗКОФОНОВОГО ИМПУЛЬСНОГО ГЕНЕРАТОРА НЕЙТРОНОВ ПРОМЕЖУ-
ТОЧНЫХ ЭНЕРГИЙ ДЛЯ ДИСТАНЦИОННОГО ОБНАРУЖЕНИЯ ДЕЛЯЩИХСЯ МАТЕРИАЛОВ
В. Черный, Г. Цепилов, А. Фролов, А. Черный, В. Дубина, В. Соловьев
В данной статье представлено описание конструкции радиационной защиты для низкофонового им-
пульсного генератора промежуточных энергий, разработанного на основе компьютерных вычислений и дан-
ных модельных экспериментов, а также приведены предельные параметры дистанционного обнаружения де-
лящихся материалов с использованием этого генератора. Конструкция магнитно-изолированного диода и
геометрия радиационной защиты были оптимизированы в соответствии с проведенными вычислениями.
РОЗРОБКА НИЗЬКОФОНОВОГО ІМПУЛЬСНОГО ГЕНЕРАТОРА НЕЙТРОНІВ ПРОМІЖНИХ
ЕНЕРГІЙ ДЛЯ ДИСТАНЦІЙНОГО ВИЯВЛЕННЯ ПОДІЛЬЧИХ МАТЕРІАЛІВ
В. Чорний, Г. Цепілов, О. Фролов, А. Чорний, В. Дубіна, В. Соловйов
У даній роботі представлено конструкцію радіаційного захисту для низькофонового імпульсного
генератора проміжних енергій, розробленого на основі комп'ютерних розрахунків і даних модельних
експериментів, а також приведені граничні параметри дистанційного виявлення подільчих матеріалів за
допомогою цього генератора. Конструкція магнітно-ізольованого діода і геометрія радіаційного захисту
були оптимізовані відповідно до проведених обчислень.
26
Supported by US DTRA and EU through the Science and Technology Center in Ukraine under Project # 329
The V.N. Karazin Kharkov National University, PO Box 2096, 61108, Kharkov, Ukraine
E-mail: chorny@pht.univer.kharkov.ua
CALCULATION
REFERENCES
|
| id | nasplib_isofts_kiev_ua-123456789-79319 |
| institution | Digital Library of Periodicals of National Academy of Sciences of Ukraine |
| issn | 1562-6016 |
| language | English |
| last_indexed | 2025-12-07T16:01:00Z |
| publishDate | 2004 |
| publisher | Національний науковий центр «Харківський фізико-технічний інститут» НАН України |
| record_format | dspace |
| spelling | Chornyi, V. Frolov, A. Tsepilov, G. Dubina, V. Chornyi, A. Solovyov, V. 2015-03-31T08:44:03Z 2015-03-31T08:44:03Z 2004 Development of a low background pulsed generator of intermediate energy range neutrons for remote detection of fissile materials / V. Chornyi, A. Frolov, G. Tsepilov, V. Dubina, A. Chornyi, V. Solovyov // Вопросы атомной науки и техники. — 2004. — № 2. — С. 24-26. — Бібліогр.: 5 назв. — англ. 1562-6016 PACS: 28.50.Ma https://nasplib.isofts.kiev.ua/handle/123456789/79319 A structure of radiation shielding for a low background pulsed generator of intermediate energy range neutrons was developed on the basis of calculations and the data obtained in the model experiments, and limit parameters for remote detection of fissile materials using this generator were determined and are presented in this paper. The magnetically insulated diode structure and the radiation shielding geometry were optimized in accordance with the performed calculations. У даній роботі представлено конструкцію радіаційного захисту для низькофонового імпульсного генератора проміжних енергій, розробленого на основі комп'ютерних розрахунків і даних модельних експериментів, а також приведені граничні параметри дистанційного виявлення подільчих матеріалів за допомогою цього генератора. Конструкція магнітно-ізольованого діода і геометрія радіаційного захисту були оптимізовані відповідно до проведених обчислень. В данной статье представлено описание конструкции радиационной защиты для низкофонового импульсного генератора промежуточных энергий, разработанного на основе компьютерных вычислений и данных модельных экспериментов, а также приведены предельные параметры дистанционного обнаружения делящихся материалов с использованием этого генератора. Конструкция магнитно-изолированного диода и геометрия радиационной защиты были оптимизированы в соответствии с проведенными вычислениями. Supported by US DTRA and EU through the Science and Technology Center in Ukraine under Project # 329. en Національний науковий центр «Харківський фізико-технічний інститут» НАН України Вопросы атомной науки и техники Сильноточные импульсные ускорители Development of a low background pulsed generator of intermediate energy range neutrons for remote detection of fissile materials Розробка низькофонового імпульсного генератора нейтронів проміжних енергій для дистанційного виявлення подільчих матеріалів Разработка низкофонового импульсного генератора нейтронов промежуточных энергий для дистанционного обнаружения делящихся материалов Article published earlier |
| spellingShingle | Development of a low background pulsed generator of intermediate energy range neutrons for remote detection of fissile materials Chornyi, V. Frolov, A. Tsepilov, G. Dubina, V. Chornyi, A. Solovyov, V. Сильноточные импульсные ускорители |
| title | Development of a low background pulsed generator of intermediate energy range neutrons for remote detection of fissile materials |
| title_alt | Розробка низькофонового імпульсного генератора нейтронів проміжних енергій для дистанційного виявлення подільчих матеріалів Разработка низкофонового импульсного генератора нейтронов промежуточных энергий для дистанционного обнаружения делящихся материалов |
| title_full | Development of a low background pulsed generator of intermediate energy range neutrons for remote detection of fissile materials |
| title_fullStr | Development of a low background pulsed generator of intermediate energy range neutrons for remote detection of fissile materials |
| title_full_unstemmed | Development of a low background pulsed generator of intermediate energy range neutrons for remote detection of fissile materials |
| title_short | Development of a low background pulsed generator of intermediate energy range neutrons for remote detection of fissile materials |
| title_sort | development of a low background pulsed generator of intermediate energy range neutrons for remote detection of fissile materials |
| topic | Сильноточные импульсные ускорители |
| topic_facet | Сильноточные импульсные ускорители |
| url | https://nasplib.isofts.kiev.ua/handle/123456789/79319 |
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