CESK� VYSOK� UCEN� TECHNICK� VP RAZE by c9t0f87l

VIEWS: 9 PAGES: 32

									CZECH TECHNICAL UNIVERSITY IN PRAGUE




       ABSTRACT OF PHD THESIS
                  Czech Technical University in Prague
          Faculty of Nuclear Sciences and Physical Engineering
                     Department of Nuclear Reactors




                          Ing. Ondřej Svoboda




  EXPERIMENTAL STUDY OF NEUTRON PRODUCTION AND
               TRANSPORT FOR ADTT




       Postgradual study program: Application of Natural Sciences
                    Study field: Nuclear Engineering




Abstract of PhD thesis for acquirement of the academic degree “Doctor”, in
                            abbreviation “Ph.D.”




                           Prague, April 2011


                                    2
3
The dissertation thesis was done in the internal and combined forms
of postgradual study at the Department of Nuclear Reactors at the Faculty of
Nuclear Sciences and Physical Engineering at Czech Technical University
in Prague.
Aspirant: Ing. Ondřej Svoboda
          Department of Nuclear Spectroscopy
          Nuclear Physics Institute
          Academy of Sciences of the Czech Republic
          250 68 Řež near Prague
Supervisor: RNDr. Vladimír Wagner, CSc.
            Department of Nuclear Spectroscopy
            Nuclear Physics Institute
            Academy of Sciences of the Czech Republic
            250 68 Řež near Prague

Opponents: Prof. Ing. Zdeněk Janout, CSc.
           Department of Experimental Physics
           Institute of Experimental and Applied Physics
           CTU Prague
           Horská 3a/22, 128 00 Prague 2

            Ing. Miloslav Hron, CSc.
            Nuclear Research Institute, plc
            Husinec-Řež, č.p. 130
            250 68 Řež




                                     4
The date of the abstract distribution: ...............................

The thesis defence takes place on ................................ at ………. at the
Board for PhD Theses Defence in the study field of Nuclear Engineering in
the room No. ........ at the Faculty of Nuclear Sciences and Physical
Engineering at Czech Technical University in Prague.

It is possible to acquaint with the thesis at the department for science and
research activity at the Faculty of Nuclear Sciences and Physical Engineering
at Czech Technical University in Prague, Břehová 7, Prague 1.

                                        prof. Tomáš Čechák, CSc.
                              The head of the Board for PhD Theses Defence
                                in the study field of Nuclear Engineering
                               FNSPE CTU in Prague, Břehová 7, Praha 1
Contents

1. State-of-the-art of spallation research ........................................................ 7
    1.1. Spallation reaction ............................................................................... 7
    1.2. Usage of spallation reaction ................................................................ 8
    1.3. Motivation ........................................................................................... 8
2. The aim of the thesis .................................................................................10
3. Methodology .............................................................................................11
    3.1. Energy plus Transmutation setup .......................................................11
    3.2. High energy neutron measurements in the E+T setup........................12
    3.3. MCNPX simulations ..........................................................................12
    3.4. Cross-section measurements of used threshold reactions ..................13
4. Results ......................................................................................................14
    4.1. Beam properties during E+T deuteron irradiations ............................14
    4.2. Experimental results of E+T deuteron irradiations ............................14
    4.3. MCNPX simulation of the E+T deuteron irradiations .......................17
    4.4. The (n,xn) cross-section measurements .............................................21
5. Conclusion ................................................................................................22
Bibliography ..................................................................................................24
List of author’s publications ..........................................................................26
List of co-author’s publications: ....................................................................28
Summary ........................................................................................................31
Resumé ..........................................................................................................32
1. State-of-the-art of spallation research
         Spallation reaction as a perspective source of neutrons is studied
with increased interest in last decade. These studies are motivated with the
need of high neutron fluxes for material research, transmutation of nuclear
waste or production of nuclear fuel from thorium. New spallation sources are
planed (European Spallation Source) or already commissioned (American
Spallation Neutron Source) to fulfill scientist requirements. With advances in
accelerator technology Accelerator Driven Systems seems thanks to its high
safety and unique properties to be a perspective energy source for future.

1.1. Spallation reaction
          Spallation reaction is a process, in which a relativistic light ion
(proton, deuteron or heavier nuclei) interacts with a massive heavy metal
target, resulting in the breakup of the heavy nucleus and in production of
wide range of new particles. Substantial parts of these particles are neutrons
with relatively high energy. Number of these neutrons depends on the energy
and mass of the interacting ion and on the target material.
          Spallation reaction can be divided into few stages. Spallation starts
with the accelerated proton (for example) interacting with the target nucleus
of heavy element (e.g. Pb). The proton penetrates the target nucleus, and
distributes its energy to the nucleons of the nucleus. This stage is called intra-
nuclear cascade. Target nucleus is afterwards in highly excited state and
undergoes a pre-equilibrium emission of particles and photons. Particles are
at this stage of process emitted unisotropicaly, most of them in the forward
direction. After this emission, energy is in the nucleus uniformly distributed,
but the nucleus is still highly excited. Such a nucleus can than disintegrate or
massively evaporate particles to lower its energy. Particle production is
isotropic at this phase.
          Neutrons produced in spallation reaction can have a wide range of
energies. Highest energy of the neutrons can reach up to the beam energy. At
the low energy part of the spectrum number of neutrons decrease
significantly under the energy one MeV.
          Most effective energy for the spallation reaction is 800-1000 MeV,
where the neutron production per MeV per particle has its maximum. Most
widely used particles for induce the spallation are protons, because proton
beams are the most intensive one. Tantalum, wolfram, lead, and bismuth in
solid phase are the most common target materials. Liquid targets with
lead/bismuth eutectics or mercury were tested at targets with high power
load [1].


                                        7
1.2. Usage of spallation reaction
         The first usage of spallation reaction was proposed in the late 1940’s
at the Lawrence Livermore National Laboratory in California, the USA.
A subcritical nuclear reactor driven by and external spallation neutron source
was studied with the aim of production of fissile material. Origins of the
practical usage of spallation reaction can be found in the works C. D.
Bowman, who proposed accelerator transmutation of waste (ATW) [2], and
C. Rubia, who was the father of the idea of accelerator driven energy
production (ADEP) [3].
         Nowadays, the main application of the spallation reaction is in
material science and related branches. Neutron scattering is namely one of
the most effective ways to obtain information on both, the structure and the
dynamics of condensed matter. A wide scope of problems, ranging from
fundamental to solid state physics and chemistry, and from materials science
to biology, medicine and environmental science, can be investigated with
neutrons. Aside from the scattering techniques, non-diffractive methods like
imaging techniques can also be applied with increasing relevance for
industrial applications.
         World leading countries plane, build or commission their spallation
neutron sources. European spallation source (ESS) is in the preconstruction
phase with commissioning at 2019 [4], American spallation neutron source
(SNS) with the beam power 1.4 MW and current in beam 1.4 mA is already
commissioned [5]. In Japan, spallation neutrons are used at Material & Life
Science Experimental Facility. China started to build its spallation neutron
source at 2010 and India is in the phase of planning.
         Rising amount of the spent fuel together with the non-proliferation
efforts push forward the studies of accelerator driven subcritical reactors and
transmutations. Transmutation is, generally said, every reaction, in which the
composition of the atom nucleus is changed. A single neutron capture can
change a long-lived nuclide to a short-live or stabile, or convert a non-fissile
nuclide to a fissile one. Transmutation can be thus used for stabilization of
radioactive fission products, conversion and fission of plutonium and minor
actinides, or for production of new fuel from thorium. In combination with
safe accelerator driven system, which is under all circumstances subcritical
and can be switched off with the switch off of the accelerator, this can be
an energy source for future yielding from broad public acceptance.

1.3. Motivation
        Practical usage of accelerator driven systems and transmutation must
be forgone by research in various branches. Simple experiments are used to
measure the cross-sections of GeV down to MeV, and to study the spallation

                                       8
reaction and high energy neutron transport in more detail. More complex
setups verify neutron multiplication, transmutation rates, heat production,
long-term stability and overall suitable concepts for future eXperimental
Accelerator Driven Systems (XADS).
          There is also rising motivation towards improving the precision of
predictions of the codes used to simulate production and transport of high-
energetic spallation products in material. More realistic simulations will help
to design more effective spallation neutron sources, subcritical blankets or
better radiation shielding. But for code development and improvements, a lot
of real experimental data is needed for comparisons and benchmark tests.




                                      9
2. The aim of the thesis
          My research on the field of accelerator driven systems involves both
simple and complex experiments. The simple experiments are represented by
the neutron cross-section measurements of the (n,xn) threshold reactions, that
can be used for high energy neutron measurements. To the complex
experiments belong spallation experiments on the Energy plus Transmutation
(E+T) setup. In the E+T setup I have studied high energy neutron field by
means of threshold activation detectors.
          Thesis further develops studies performed within the international
project Energy and Transmutation of Radioactive waste (E&T RAW), see
e.g. [6], [7], or [8]. Experimental devices are located in Joint Institute for
Nuclear Research (JINR) Dubna, Russia. Main tasks of the thesis were to:
    prepare, perform and evaluate 1.6 GeV and 2.52 GeV deuteron
     experiments on the E+T setup,
    study and routinely apply spectroscopic corrections needed for data
     evaluation,
    measure beam intensities, positions and shapes and give the results to
     whole E&T RAW collaboration,
    compare experimental results between itself and with previous proton
     experiments performed on the E+T setup,
    MCNPX simulation of the experiment and comparison between
     experimental and simulated data,
    prepare, perform and evaluate cross-section measurements of (n,xn)
     threshold reactions used for high energy neutron measurements in the
     E+T setup.

          Thesis was written with respect to its possible users from the Energy
and Transmutation community as well as to students from Nuclear Physics
Institute of the ASCR, who are interested in this field of physics. In the work
there are maybe more detail descriptions and examples than it would be
necessary for a PhD work, but I tried to present a clear description of all
aspects of my work in order to enable easier continuation in these studies.
With the constituency of the readers is connected also the choice of used
language – I have selected English.




                                      10
3. Methodology
3.1. Energy plus Transmutation setup
         Energy plus Transmutation setup consists of a cylindrical lead target
(diameter 84 mm, total length 480 mm) and a surrounding subcritical
uranium blanket (206.4 kg of natural uranium). Target and blanket are
divided into four sections. Between the sections there are 8 mm gaps for
user’s samples. Each section contains target cylinder 114 mm long and 30
identical natural uranium rods, which are secured in a hexagonal steel
container. The front and back of each section are covered with hexagonal
aluminum plate 6 mm thick. The four target-blanket sections are mounted
along the target axis on a wooden plate, which is moreover covered with 4
mm thick steel sheet. Uranium rods are hermetically encapsulated in
aluminum coverage of thickness 1 mm, respectively 2 mm at the bases. Each
rod has a outside diameter of 36 mm, a length of 104 mm, and a weight of
1.72 kg. Density of the uranium is considered to be 19.05 g·cm-3.




Figure 1: Cross-sectional side view (left) and front view (right) of the
"Energy plus Transmutation" setup. All dimensions are in millimeters.
Around the blanket, there is a radiation shielding consisting of a wooden box
with cadmium plates and polyethylene ((CH2)n) in the box walls. Wooden
box has approximately cubic shape and volume 1 m3. Cadmium plates have


                                     11
thickness of 1 mm and are mounted on the inner walls of the box.
Polyethylene has a density 0.8 g·cm-3 and is granulated.

3.2. High energy neutron measurements in the E+T setup
I have measured high energy neutron field produced in spallation reactions
inside the E+T setup. I used a method of neutron activation analysis –
I placed a known amount of chosen isotope into unknown neutron field.
Activation samples were made from aluminum, gold, tantalum, indium,
cobalt, bismuth, and yttrium foils. Chemical purity of the materials was better
than 99.99 %.




Figure 2: Activation materials used in the E+T experiments for study of the
high energy neutron field.
         I used products of (n,xn) threshold reactions in activation materials
to study high energy parts of neutron spectrum. Non-threshold (n,) reactions
were suitable for neutron multiplicity studies. I have measured irradiated foils
on HPGe detectors and I have used DEIMOS32 code [9] to analyze gained
gamma spectra. I have studied and routinely used wide set of spectroscopic
corrections to correct raw data.

3.3. MCNPX simulations

         I have used MCNPX (Monte Carlo N-Particle transport code –
eXtended) [10] to calculate various aspects of the E+T experiments. I have
worked with the version 2.7.a and combination of models INCL4/ABLA.
         I have calculated deuteron, proton, neutron, and pion spectra in the
volumes representing the foils in E+T setup irradiated by deuteron beams.
I have done a manual folding of calculated spectra with cross-sections
calculated in TALYS [11] and MCNPX. I have also used MCNPX to
determine yields of non-threshold (n,) reactions and the multiplicity of the
setup. Last but not least I have studied various spectroscopy problems using

                                      12
MCNPX (HPGe detector response on non-homogenous and non-point-like
source, change of the detector efficiency due to the sample dimensions).

3.4. Cross-section measurements of used threshold reactions
         Almost no experimental cross-section data exist for most of used
threshold reactions over 40 MeV or “n” higher than four. I have used quasi-
monoenergetic neutron sources at The Svedberg Laboratory (TSL) [12] at
Uppsala, Sweden, and at Nuclear Physics Institute (NPI) [13] at Řež. These
sources are based on 7Li(p,n)7Be reaction with half of the neutron intensity in
the peak with FWHM = 1 MeV (corresponds to the ground state and first
excited state at 0.43 MeV in 7Be) and half of intensity in a continuum in
lower energies (corresponds to higher excited states, multiple-particle
emission etc.). Neutron intensities were up to 5.105 cm-2s-1 at TSL,
respectively 108 cm-2s-1 at NPI. I have used the same types of foils as in E+T
experiments. I have measured irradiated foils on HPGe detectors and I have
used the same evaluation methods as at E+T experiments. I have developed a
method for neutron background subtracting - I made a manual folding
between neutron spectra and cross-sections calculated in TALYS. Then I
have calculated ratio between the isotope production in neutron peak and by
the whole neutron spectrum.




                                      13
4. Results
          From the year 2005 up to now, there were three deuteron
irradiations of the E+T setup. Irradiations took place at the Nuclotron
accelerator of the JINR Dubna, Russia. Beam energies were 1.6 GeV,
2.52 GeV, and 4 GeV. I have prepared activation samples, placed them into
the setup and measured them after the irradiation. I have completely
evaluated first two experiments, at the 4 GeV experiment I have done a beam
analysis, calibration of the detectors and MCNPX simulations.

4.1. Beam properties during E+T deuteron irradiations
          I have used 10x10 cm2 Al beam monitor to measure deuteron beams
intensity. Cross-section of used 27Al(d,3p2n)24Na reaction is the only one
known for deuterons in used energy region. I have tried to use also other
observed reactions and I have recalculated their cross-sections from the
proton ones according to the method proposed by J. Blocki [14].
          I have used square Cu foils placed directly in front of the target to
measure beam position and shape. For evaluation I have chosen only those
reactions that were not influenced by backscattered neutrons from the
spallation target. Using another shapes and positions of Cu foils I have
determined the number of beam particles going out of the target and
parallelism of the beam to the target axis.
          Results of my beam measurement were combined with the beam
data from other groups and a common report was published for every
experiment.

4.2. Experimental results of E+T deuteron irradiations
          I have observed yields of reactions with threshold from 5 MeV up to
80 MeV. In longitudinal direction yields have their maxima near to the first
gap (~12 cm from the target beginning) for all three beam energies. In radial
direction the yields of threshold reactions quickly (almost exponentially)
decrease. Typical example of the yields of Au isotopes produced during
1.6 GeV deuteron experiment are displayed on Figure 3 and Figure 4. The
uncertainty bars in the figures are only from the Gauss fit in the DEIMOS32
and are hardly visible in the logarithmic scale (are only a few percent). Lines
in the graphs are to guide reader’s eyes.




                                      14
                             10-2

                                         198Au     196Au          194Au            192Au     24Na
                             10-3
 Yield [1/g*deuteron]




                             10-4



                             10-5


                             10-6


                             10-7
                                    -5    5          15              25              35          45
                                                  Position along the target [cm]
Figure 3: Yields of the isotopes produced in Au and Al activation detectors in
longitudinal direction, 3 cm over the target axis, 1.6 GeV deuteron
experiment.

                             10-2
                                         198Au       196Au           194Au           192Au       24Na
                             10-3
      Yield [1/g*deuteron]




                             10-4


                             10-5


                             10-6


                             10-7
                                    2         4            6                8               10          12
                                                  Radial distance from the target axis [cm]
Figure 4: Yields of the isotopes produced in Au and Al activation detectors in
radial direction, first gap of the E+T setup – 12.2 cm from the target
beginning, 1.6 GeV deuteron experiment.

                                                             15
         Products of non-threshold 197Au(n,)198Au reaction visible in the
Figure 3 and Figure 4 are caused by the epithermal and resonance neutrons
coming from the biological shielding. Field of epithermal and resonance
neutrons inside the biological shielding is disturbed only on the beginning
and at the end of the setup due to the holes in the shielding. Using a new form
of the water bath method [15] and data from MCNPX calculation, I have
determined neutron multiplicity of the E+T setup, see Figure 5.

                                         80
                                                  protons - exp
                                         70
Neutrons per beam particle per GeV [-]




                                                  deuterons - exp - Au
                                                  deuterons - exp - Ta
                                         60
                                                  protons - sim
                                         50       deuterons - sim

                                         40

                                         30

                                         20

                                         10

                                         0
                                              0                1            2                3   4
                                                                         Beam energy [GeV]
Figure 5: Neutron multiplicities for E+T setup normalized per GeV (proton
experimental points overtaken from the PhD thesis of A. Krása, [16]).

          I compared experimental yields of reactions with different threshold
(here e.g. 196Au and 192Au). I have observed a spectrum hardening at the end
of the target. Spectrum hardening is specific for the spallation reaction and is
caused by different origin of the neutrons. Neutrons with higher energies
comes from the intranuclear phase of the spallation reaction and are emitted
more forward, in contradiction to the neutrons below 20 MeV, which comes
from evaporation and fission phase of the spallation reaction and are emitted
isotropicaly. Additional complication of neutron spectrum comes from the
high energy fission in uranium blanket and neutron scattering and
moderation. Thus, neutron field inside the E+T setup is a complicated
mixture of spallation, fission, moderated and back-scattered neutrons.
                                                                              16
                                                            0.4




                                                                  Spectral index 192Au/196Au [-]
                                                            0.3


                                                            0.2


                                                           0.1
          3 cm
             6 cm                                          0.0
              8.5 cm
                                                      48
               10.7 cm                           36
                                            24
                                  12
                            0


Figure 6: Neutron spectra hardening along the target in 1.6 GeV deuteron
experiment (ratio between 192Au and 196Au).


4.3. MCNPX simulation of the E+T deuteron irradiations
         I have used MCNPX to calculate neutron, proton and deuteron
spectra inside the setup. In the Figure 7 we can see an example of a neutron
spectrum inside the first target cylinder. In this case I have studied
dependence between the presence of various parts of E+T setup and produced
neutron spectrum. Difference between bare Pb target and target with all
constructions (Al and Fe support structures, U-rod cover from Al etc.) is
almost negligible, support structures add some more high energy neutrons
due to the spallation induced on them by scattered neutrons. Addition of
natural uranium causes more neutrons in the region between 1 keV and
1 MeV due to the high energy fission. Biological shielding adds further
neutrons to the low energy region bellow 10 keV and also a second maximum
of the neutron spectrum around 0.025 eV. Addition of the cadmium layer on
the inner walls of the biological shielding suppresses this thermal energy
peak. In all cases, a small peak can be seen close to the highest neutron
energies. These neutrons come from the deuteron disintegration.




                                       17
                                       100

                                                     Pb          Pb+const          Pb+U+const       without Cd   whole E+T
Number of neutrons [deuteron-1.cm-2]



                                       10-2




                                       10-4




                                       10-6




                                       10-8
                                              10-8        10-6              10-4          10-2          100      102         104
                                                                                   Neutron energy [MeV]
Figure 7: Spectrum of the neutrons in the first target cylinder irradiated with
2.52 GeV protons, log-log scale, various parts of the setup are omitted.
Uncertainties are on the level of 1 percent.
         I compared results of experimental and simulated yields by
evaluating experiment/simulation ratios. Most of the experiment/simulation
ratios are parallel within the DEIMOS32 uncertainty, other uncertainties
stated separately are from beam intensity (at least 10%), foil placement (up to
20% at 5 mm displacement, proven by M. Majerle in his PhD [17]),
spectroscopic corrections (1%) and detector calibration (2%).
         Absolute values of the experiment/simulation ratio are strongly
dependant on the beam intensity determination. To see clearly the shape of
the ratio I normalized it to the most intensive foil in the set. I got values
which are close to the one, see e.g. Figure 10. No serious differences in the
experiment/simulation ratios were found, so the INCL4/ABLA models seem
to be generally precise in the case of deuteron beams. This can be confirmed
also by the comparison between the figures with experimental yields, where a
maximum can be seen both in longitudinal and radial direction, and in the
figures of experiment/simulation ratios, where these maximum are missing
(the simulation describes well the shape of yield curves).




                                                                                       18
                              2.5

                                        198Au           196Au           194Au           192Au        24Na

                              2.0
Exp. yield / sim. yield [-]




                              1.5



                              1.0



                              0.5



                              0.0
                                    2       4                   6                 8             10          12
                                                Radial distance from the target axis [cm]
Figure 8: Ratio between experiment and simulation in radial direction for
2.52 GeV deuteron experiment, Au and Al samples in the first gap.


          Summarizing MCNPX results from previous proton experiments we
have observed an increasing difference in the radial direction between
experiment and simulation for proton energies higher than 1.5 GeV, see
Figure 9. For deuteron experiments there is a good agreement for all three
measured energies (from 1.6 GeV up to 4 GeV), see Figure 10. This result
prefers the hypothesis that in proton experiments the problem is rather in the
experimental part than in the simulations.




                                                                   19
                                2.5
                                              2.0 GeV           1.5 GeV           1.0 GeV             0.7 GeV

                                2.0
 exp. yield / sim. yield [-]




                                1.5



                                1.0



                                0.5
                                                                       194Au


                                0.0
                                          2   4           6             8          10           12           14
                                                      Radial distance from the target axis [cm]
Figure 9: Ratio between experiment and simulation for different proton beam
energies and 194Au (overtaken from A. Krása [18]). Samples were placed in
radial direction in the first gap of the setup.

                               2.5

                                                      1.6 GeV               2.52 GeV                 4 GeV
                               2.0
 Exp. yield / sim. yield [-]




                               1.5



                               1.0



                               0.5

                                                                        194Au


                               0.0
                                      2           4               6                 8               10            12
                                                          Radial distance from the target axis [cm]
Figure 10: Ratio between experiment and simulation for different deuteron
beam energies and 194Au. Samples were placed in radial direction in the first
gap of the setup.

                                                                       20
4.4. The (n,xn) cross-section measurements
         I have studied cross-sections of (n,xn) threshold reactions for totally
11 energies in the energy region 17 - 94 MeV. I have completely evaluated
five measurements and at another six I have helped or I have done a partial
evaluation. Highest order of measured reaction was (n,10n).
         I used well-known cross-sections for low threshold reactions to
check if I got appropriate results. I made a comparison between the data from
EXFOR library [19], results of the calculations I have done in deterministic
code TALYS and experimental data from NPI and TSL. For most of the
isotopes I observed good agreement. For energies higher than 40 MeV and
reactions higher than (n,4n) no data are available in EXFOR (except
bismuth). My cross-section data are in this sense unique and I presented them
on international conferences (Baldin 2009 [20], ND2010 [21], EFNUDAT
meetings [22], [23], AER meetings…) with positive response.

                        3
                                                                           EXFOR
                       2.5
                                                                           NPI experiments

                                                                           TSL experiments
Cross-section [barn]




                        2
                                                                           TALYS 1.0
                       1.5
                                                                        197Au(n,2n)196Au


                        1


                       0.5


                        0
                             0   10   20   30        40      50    60     70      80       90   100
                                                Neutron energy [MeV]

        Cross-section values of the 197Au(n,2n)196Au reaction, comparison
Figure 11:
between EXFOR, TALYS 1.0, my values and data of J. Vrzalová1 (NPI
experiment at 30 and 36 MeV).



1
         I was a consultant on her diploma work and helped with the data analysis.

                                                        21
5. Conclusion

          As a member of the international project Energy and Transmutation
of Radioactive Waste I have studied production and transport of high energy
neutrons in the setup called Energy plus Transmutation. This setup consists
of thick, lead target surrounded with natural uranium blanket and
polyethylene biological shielding. Setup was irradiated with 1.6 GeV,
2.52 GeV, and 4 GeV deuterons. I prepared foils for all three experiments; I
was present during the irradiation and I measured irradiated foils at
JASNAPP laboratory of the Joint Institute for Nuclear Research, Dubna,
Russia. I have completely evaluated first two experiments.
          I used neutron activation detectors from Al, Au, Bi, Co In, Ta, and Y
in the form of thin foils to measure spatial distribution of the neutrons inside
the setup. I have observed threshold (n,xn), (n,p), and (n,) reactions in the
samples in order to distinguish energies of the neutrons. Maximum order of
these reactions was (n,11n), that means a threshold of ~ 80 MeV. I have
observed maximal neutron flux in the first gap of the setup that means 12 cm
from the target beginning in longitudinal direction. In radial direction the
maximum was in the centre of the target and then it decreased almost
exponentially. Spectral indexes showed a hardening of the neutron spectra in
longitudinal as well as radial direction. Comparison among deuteron
experiments and also with the previous 0.7 GeV experiment with protons
resulted in nice dependence between beam type or energy and intensity of the
neutron flux inside the setup.
          Polyethylene biological shielding in combination with non-threshold
reactions enabled me to calculate total number of produced neutrons. In the
case of deuterons experiments neutron multiplicity was up to 152 ± 16 at
4 GeV irradiation.
          I have measured deuteron beam properties in detail. I have used Al
foil for beam intensity measurement and Cu foils for beam position, profile
and direction determination. Results of my beam analysis are used by whole
Energy and Transmutation collaboration.
          I made MCNPX simulations of deuteron experiments and I
compared it with experimental data. MCNPX describes relatively well the
shape of the neutron distribution in radial and longitudinal directions,
however the absolute exp/sim differences are much bigger than they should
be at future ADS systems, so a further MCNPX development and benchmark
tests are needed. I have not observed any serious discrepancies in the number
of neutrons emitted to backward angles like it was observed at previous
proton experiments.

                                      22
         Further, I obtained unique data about cross-sections of used
threshold reactions for neutron energies above 40 MeV. With the support
from EFNUDAT I used quasi-monoenergetic 7Li(p,n)7Be neutron source at
TSL Uppsala, Sweden. In 2008, I performed three irradiations with neutron
energies 22, 47, and 94 MeV. These measurements were supplemented with
measurements at NPI Řež with neutron energies 17, 22, 30, and 35 MeV. In
the meantime I prepared a proposal on second cross-section measurement at
Uppsala and in 2010 I participated on irradiations at neutron energies 59, 66,
73, and 89 MeV. I was involved in all experiments and I analyzed the data
completely except the 30 and 35 MeV irradiations at NPI and the second TSL
experiment. I have developed a procedure how to subtract the neutron
background, which was applied on most of measured cross-sections. Using
two different neutron sources and various spectroscopic equipments I got the
same results within the uncertainties, so all important sources of uncertainties
seems to be under control. I have compared measured cross-sections with the
data from EXFOR where possible. I used deterministic code TALYS to
calculated neutron cross-sections of all reactions and I compared them with
measured data.
         I have already presented the data discussed in this work on 15
international workshops and conferences. I am co-author of four articles in
peer reviewed journals, I am the first author of 11 proceedings (three of them
are peer reviewed), one internal report and co-author of another five
proceedings and four internal reports.




                                      23
Bibliography

[1] Megawatt Pilot Target Experiment, project web pages
http://megapie.web.psi.ch/ (5.1.2011)
[2] C.D. Bowman et al.: Nuclear Energy Generation and Waste
Transmutation Using an Accelerator-driven Intense Thermal Neutron Source,
Nuclear Instruments and Methods in Physics Research, A320 (1992) p. 336-
367
[3] C. Rubbia et al.: Conceptual design of a fast neutron operated high power
energy amplifier, European Organization for Nuclear Research/AT/94-44
(ET)
[4] European Spallation Source web page, http://ess-scandinavia.eu/
(4.1.2011)
[5] Spallation Neutron Source, http://neutrons.ornl.gov/facilities/SNS/
(4.1.2011)
[6] J. Adam et al.: Transmutation studies with GAMMA-2 setup using
relativistic proton beams of the JINR Nuclotron, Nuclear Instruments and
Methods - A, V. 562, Iss. 2 (2006) p. 741-742
[7] W. Westmeier et al.: Transmutation experiments on 129I, 139La and
237Np using the Nuclotron accelerator, Radiochimica Acta, V. 93 (2005)
p. 65-73
[8] A. Krása et al.: Neutron production in a Pb/U-setup irradiated with 0.7-
2.5 GeV protons and deuterons, Nuclear Instruments and Methods in Physics
Research, Section A, 615 (2010) p. 70-77, ISSN: 0168-9002
[9] J. Frána: Program DEIMOS32 for Gamma-Ray Spectra Evaluation,
Journal of Radioanalytical and Nuclear Chemistry, V.257, No. 3 (2003) p.
583-587
[10] MCNPX (Monte Carlo N-Particle eXtended), http://mcnpx.lanl.gov/
(19. 11. 2010)
[11] A. J. Koning et al., “TALYS-1.0.”, Proceedings of the International
Conference on Nuclear Data for Science and Technology - ND2007, (2007)
p. 211-214
[12] A. V. Prokofiev et al.: The TSL Neutron Beam Facility, Radiation
Protection Dosimetry, 126 (2007) p. 18-22
[13] P. Bém et al.: The NPI cyclotron-based fast neutron facility, Proceedings
of the International Conference on Nuclear Data for Science and Technology
- ND2007, (2007) p. 555-558
                                     24
[14] J. Blocki et al.: Proximity forces, Annals of Physics, Vol. 105, Issue 2,
(1977) p. 427-462
[15] K. van der Meer et al., Spallation yields of neutrons produced in thick
lead/bismuth targets by protons at incident energies of 420 and 590 MeV,
Nuclear Instruments and Methods in Physics Research B 217 (2004) p. 202-
220
[16] A. Krása: Neutron Emission in Spallation Reactions of 0.7 – 2.0 GeV
Protons on Thick, Lead Target Surrounded by Uranium Blanket, Dissertation
Thesis, FJFI – ČVUT, Prague (2008)
[17] M. Majerle: Monte Carlo methods in spallation experiments,
Dissertation Thesis, FJFI – ČVUT, Prague (2009)
[18] A. Krása: personal communication
[19] Experimental Nuclear Reaction Data (EXFOR/CSISRS),
http://www.nndc.bnl.gov/exfor, (4.12.2010)
[20] O. Svoboda et. al.: Measurements of Cross-sections of the Neutron
Threshold Reactions and Their Usage in High Energy Neutron Measurements
at "Energy plus Transmutation", XIX. International Baldin Seminar on High
Energies Physics Problem, Dubna, Russia, September 25 -29 (2008),
Relativistic Nuclear Physics and Quantum Chromodynamics series, p. 136 –
141, ISBN: 978-5-9530-0203-5
[21] O. Svoboda et al.: Cross-section Measurements of (n,xn) Threshold
Reactions, ND2010 conference, Jeju (2010) South Korea – in print
[22] O. Svoboda et al.: Three years of cross-section measurements of (n,xn)
threshold reactions at TSL Uppsala and NPI Řež, EFNUDAT user and
collaboration workshop „Measurements and Models of Nuclear Reactions“,
Paris, France, EPJ Web of Conferences, vol. 8 (2010) p. 7003/1-6, ISBN.
978-2-7598-0585-3
[23] O. Svoboda et al.: Cross-section Measurements of (n,xn) Threshold
Reactions in Au, Bi, I, In, and Ta - Proceeding of the 2nd EFNUDAT
workshop – Slow and Resonance Neutrons, Special Scientific Issue of
Institute of Isotopes – Hungarian Academy of Science, Budapest, Hungary, p.
155-161, ISBN: 978-963-7351-19-8




                                     25
List of author’s publications

 O. Svoboda, J. Adam, Z. Dubnička, A. Krása, A. Kugler, M. I.
  Krivopustov, M. Majerle, V. M. Tsoupko-Sitnikov, V. Wagner: Setup
  consisting of a Pb/U assembly irradiated by 2.52 GeV deuterons,
  Relativistic Nuclear Physics and Quantum Chromodynamics volume 1,
  (2006) p. 222-227, ISBN: 5-9530-0190-8
 O. Svoboda: Produkce neutronů v tříštivých reakcích a jejich využití pro
  transmutaci radionuklidů, Jaderná energetika v pracích mladé generace –
  2006, Sborník 6. Mikulášského setkání sekce mladých při České nukleární
  společnosti, VÚT Brno (2007) p. 66-70, ISBN: 978-80-02-01883-4
 O. Svoboda, A. Krása, F. Křížek, A. Kugler, M. Majerle, V. Wagner, V.
  Henzl, D. Henzlová, Z. Dubnička, M. Kala, M. Kloc, J. Adam, M. I.
  Krivopustov, V. M. Tsoupko-Sitnikov: Neutron Production in Pb/U
  Assembly Irradiated by Protons and Deuterons at 0.7–2.52 GeV,
  ND2007, Nice (2007) DOI: 10.1051/ndata:07737, p. 1197 - 1200
 O. Svoboda, A. Krása, M.Majerle, V. Wagner: Neutron production in
  Pb/U assembly irradiated by deuterons at 1.6 and 2.52 GeV, NEMEA-4 -
  Proceedings of the CANDIDE workshop, Prague (2007) p. 87 – 90, ISBN
  978-92-79-08274-0,
 O. Svoboda, A. Krása, A. Kugler, M. Majerle, V. Wagner: Cross-section
  measurements of the (n,xn) threshold reactions, NEMEA-5 - Proceedings
  of the CANDIDE workshop (2011) p. 103-106, ISBN: 978-92-79-19067-
  4
 O. Svoboda, A. Krása, A. Kugler, M. Majerle, V. Wagner: Measurements
  of cross-sections of neutron threshold reactions and their usage in high
  energy neutron measurements, recenzovaný sborník 16. konference
  českých a slovenských fyziků, Hradec Králové (2009), ISBN: 80-86148-
  93-9
 O. Svoboda, A. Krása, M. Majerle, V. Wagner: Study of Neutron
  Production and Transmutation in ADTT, sborník k IGS workshopu,
  Prague (2009), ISBN 978-80-01-04286-1
 O. Svoboda, A. Krása, M. Majerle, V. Wagner: Measurements of Cross-
  sections of the Neutron Threshold Reactions and Their Usage in High
  Energy Neutron Measurements at "Energy plus Transmutation",
  Relativistic Nuclear Physics and Quantum Chromodynamics series,
  Dubna (2008), p. 136 – 141, ISBN: 978-5-9530-0203-5
 O. Svoboda, J. Vrzalová, A. Krása, M. Majerle, V. Wagner: Cross-
  section Measurements of (n,xn) Threshold Reactions in Au, Bi, I, In, and
  Ta, - Proceeding of the 2nd EFNUDAT workshop – Slow and Resonance
  Neutrons, Special Scientific Issue of Institute of Isotopes – Hungarian
                                   26
  Academy of Science, Budapest (2009) p. 155-161, ISBN: 978-963-7351-
  19-8
 O. Svoboda, J. Vrzalová, A. Krása, M. Majerle, V. Wagner: Cross-
  section Measurements of (n,xn) Threshold Reactions, ND2010, Jeju
  (2010) South Korea – accepted, in print
 O. Svoboda, A. Krása, M. Majerle, V. Wagner: Study of Spallation
  Reaction, Neutron Production and Transport in Thick Lead Target and
  Uranium Blanket Irradiated with 0.7 GeV Protons, Joint Institute for
  Nuclear Research – Preprint E15-2009-177
 O. Svoboda, J. Vrzalová, A. Krása, A. Kugler, M. Majerle, V. Wagner:
  Three years of cross-section measurements of (n,xn) threshold reactions
  at TSL Uppsala and NPI Řež, EPJ Web of Conferences, vol. 8, Paris,
  (2010) p. 7003/1-6, ISBN. 978-2-7598-0585-3




                                   27
List of co-author’s publications:
 V. Wagner, A. Krása, F. Křížek, A. Kugler, M. Majerle, O. Svoboda,
  J. Adam, M. I. Krivopustov: Experimental Studies of Spatial Distributions
  of Neutrons inside and around the Setup Consisted from a Thick Lead
  Target and a Large Uranium Blanket Irradiated by Relativistic Protons,
  Relativistic Nuclear Physics and Quantum Chromodynamics, vol. II,
  Dubna (2005) p. 111-116, ISBN: 5-9530-0055-3
 A. Krása, M. Majerle, F. Křížek, V. Wagner, A. Kugler, O. Svoboda, V.
  Henzl, D. Henzlová, J. Adam, P. Čaloun, V. G. Kalinnikov, M. I.
  Krivopustov, V. I. Stegailov, V. M. Tsoupko-Sitnikov: Comparison
  between experimental data and Monte-Carlo simulations of neutron
  production in spallation reactions of 0.7-1.5 GeV protons on a thick, lead
  target, Journal of Physics: Conference Series 41 (2006) p. 306-314
 V. Wagner, A. Krása, M. Majerle, F. Křížek, O. Svoboda, A. Kugler, J.
  Adam, V. M. Tsoupko-Sitnikov, M. I. Krivopustov, I. V. Zhuk, W.
  Westmeier: The Possibility to Use „Energy plus Transmutation“ Setup
  for Neutron Production and Transport Benchmark Studies, PRAMANA –
  Journal of Physics vol. 68 (2007) p. 297-306
 M. I. Krivopustov, A. V. Pavliouk, A. D. Kovalenko, I. I. Mariin, A. F.
  Elishev, J. Adam, A. Kovalik, Yu. A. Batusov, V. G. Kalinnikov, V. B.
  Brudanin, P. Chaloun, V. M. Tsoupko-Sitnikov, A. A. Solnyshkin, V. I.
  Stegailov, S. Gerbish, O. Svoboda, Z. Dubnicka, M. Kala, M. Kloc, A.
  Krasa, A. Kugler, M. Majerle, V. Wagner, R. Brandt, W. Westmeier, H.
  Robotham, K. Siemon, M. Bielewicz, S. Kilim, M. Szuta, E. Strugalska-
  Gola, A. Wojeciechowski, S. R. Hashemi-Nezhad, M. Manolopoulou, M.
  Fragopolou, S. Stoulos, M. Zamani-Valasiadou, S. Jokic, K. Katovsky, O.
  Schastny, I. V. Zhuk, A. S. Potapenko, A. A. Safronova, Zh. A.
  Lukashevich, V. A. Voronko, V. V. Sotnikov, V. V. Sidorenko, W.
  Ensinger, H. D. Severin, S. Batsev, L. Kostov, Kh. Protokhristov, Ch.
  Stoyanov, O. Yordanov, P. K. Zhivkov, A. V. Kumar, M. Sharma, A. M.
  Khilmanovich, B. A. Marcinkevich, S. V. Korneev, Ts. Damdinsuren, Ts.
  Togoo, H. Kumawat and Collaboration “Energy plus Transmutation:
  About the first experiment on investigation of the 129I, 237Np, 238Pu and
  239
      Pu transmutation at the Nuclotron 2.52 GeV deuteron beam in neutron
  field generated in Pb/U-assembly Energy plus Transmutation>>, Dubna
  Preprint E1-2007-7
 V. Wagner, A. Krása, F. Křížek, A. Kugler, M. Majerle, O. Svoboda, Z.
  Dubnička, J. Adam, M.I. Krivopustov: Spatial distribution of neutrons in
  the Pb/U assembly irradiated by relativistic protons and deuterons -
  systematics of experimental results, Relativistic Nuclear Physics and

                                    28
    Quantum Chromodynamics vol. 1, Dubna (2006) p. 228-233, ISBN: 5-
    9530-0190-8
   M. Oden, A. Krása, M. Majerle, O. Svoboda, V. Wagner: Monte-Carlo
    Simulations: Fluka vs. MCNPX, Nuclear Physics Methods and
    Accelerators in Biology and Medicine, AIP Conference Proceedings,
    Prague (2007) p. 958
   V. Wagner, A. Krása, M. Majerle, O. Svoboda: Systematic studies of
    neutrons produced in the Pb/U assembly irradiated by relativistic protons
    and deuterons, NEMEA-4 - Proceedings of the CANDIDE workshop,
    Prague (2007) p. 95 -98, ISBN 978-92-79-08274-0,
   M. I. Krivopustov, A. V. Pavliouk, A. D. Kovalenko, I. I. Mariin, A. F.
    Elishev, J. Adam, A. Kovalik, Yu. A. Batusov, V. G. Kalinnikov, V. B.
    Brudanin, P. Chaloun, V. M. Tsoupko-Sitnikov, A. A. Solnyshkin, V. I.
    Stegailov, Sh. Gerbish, O. Svoboda, Z. Dubnicka, M. Kala, M. Kloc, A.
    Krasa, A. Kugler, M. Majerle, V. Wagner, R. Brandt, W. Westmeier, H.
    Robotham, K. Siemon, M. Bielewicz, S. Kilim, M. Szuta, E. Strugalska-
    Gola, A. Wojeciechowski, S. R. Hashemi-Nezhad, M. Manolopoulou, M.
    Fragopolou, S. Stoulos, M. Zamani-Valasiadou, S. Jokic, K. Katovsky, O.
    Schastny, I. V. Zhuk, A. S. Potapenko, A. A. Safronova, Zh. A.
    Lukashevich, V. A. Voronko, V. V. Sotnikov, V. V. Sidorenko, W.
    Ensinger, H. D. Severin, S. Batsev, L. Kostov, Kh. Protokhristov, Ch.
    Stoyanov, O. Yordanov, P. K. Zhivkov, A. V. Kumar, M. Sharma, A. M.
    Khilmanovich, B. A. Marcinkevich, S. V. Korneev, Ts. Damdinsuren, Ts.
    Togoo, H. Kumawat: First results studying the transmutation of 129I,
    237Np, 238Pu, and 239Pu in the irradiation of an extended natU/Pb-
    assembly with 2.52 GeV deuterons, Journal of Radioanalytical and
    Nuclear Chemistry, vol. 279 (2009) p. 567-584
   A. Krása, V. Wagner, M. Majerle, F. Křížek, A. Kugler, O. Svoboda, J.
    Adam, M. I. Krivopustov: Neutron production in a Pb/U-setup irradiated
    with 0.7-2.5 GeV protons and deuterons, Nuclear Instruments and
    Methods in Physics Research, Section A, vol. 615 (2010) p. 70-77, ISSN:
    0168-9002
   M. Majerle, J. Adam, A. Krása, S. Peetermans, O. Sláma, Stegailov, O.
    Svoboda, Tsoupko-Sitnikova, V. Wagner: Monte Carlo method in
    neutron activation analysis, Joint Institute for Nuclear Research Preprint
    E11-2009-178
   T. Bílý, J. Frýbort, L. Heraltová, O. Huml, O. Svoboda, M. Vinš:
    Citlivostní analýza MCNP modelu školního reaktoru VR-1 Vrabec,
    technical report KJR FJFI ČVUT
   J. Adam A. Baldin, N. Vladimirova, N. Gundorin, B. Guskov, V.
    Dyachenko, A. Elishev, M. Kadykov, E. Kostyuhov, V. Kransov, I.

                                     29
Marin, V. Pronskikh, A. Rogov, A. Solnyshkin, V. Stegailov, S.
Stetsenko, S. Tyutyunikov, V. Furman, V. Tsoupko-Sitnikov, E. Belov,
M. Galanin, V. Kolesnikov, N. Ryazansky, S. Solodchenkova, B.
Fonarev, V. Chilap, A. Chinenov, E. Baldina, A. Balabekyan, G.
Karapetyan, I. Zhuk, S. Korneev, A. Potapenko, A. Safronova, V. N.
Sorokin, V. V. Sorokin, A. Khilmanovich, B. Marcynkevich, T. Korbut,
Ch. Stoyanov, L. Kostov, P. Zhivkov, O. Yordanov, S. Batzev, Ch.
Protohristov, A. Kugler, V. Wagner, M. Majerle, A. Krasa, O. Svoboda,
K. Katovsky, O. Schasny, A. Tuleushev, K. Gudima, M. Baznat, R.
Togoo, D. Otgonsuren, Ts. Tumendelger, Ts. Damdinsuren, M. Shuta, E.
Strugalska-Gola, S. Kilim, M. Bielevicz, A. Wojeciechowsky, V.
Voronko, V. Sotnikov, V. Sidorenko, I. Haysak, S. R. Hashemi-Nezhad,
Y. Borger, W. Westmeier, H. Robotham, W. Ensinger, D. Severin, M.
Rossbah, B. Thomauske, M. Zamani, M. Manolopoulou, St. Stoulos, M.
Fragopolou, St. Jokic, H. Kumawat, V. Kumar, M. Sharma („E&R RAW“
collaboration): Study of deep subcritical electronuclear systems and
feasibility of their application for energy production and radioactive
waste transmutation – Joint Institute for Nuclear Research Preprint
Preprint E1-2010-61




                                30
Summary
          High energy neutron production in spallation reactions and their
transport in the system of massive lead target and uranium blanket were
studied within the international project Energy and Transmutation of
Radioactive Waste. Setup called Energy plus Transmutation placed in Dubna,
Russia, was irradiated with 1.6 GeV up to 4 GeV deuterons. Threshold
reactions on activation detectors from Al, Au, Bi, Co, In, Ta, and Y were
used for neutron measurements. Activated foils were measured on HPGe
detectors. Spectroscopic corrections were applied during data analysis to find
the yields of produced isotopes. Experimental results were compared with
MCNPX calculations. These experiments are a continuation of previous
research of above mentioned setup with relativistic protons. No serious
disagreement in neutron production to backward angles was observed for
deuteron experiments contrary to proton ones.
          Cross-sections of used threshold reactions were measured on quasi-
monoenergetic neutron sources at Nuclear Physics Institute in Řež and at The
Svedberg Laboratory in Uppsala, Sweden. Totally eleven irradiations were
done in the energy range 17 – 94 MeV. Threshold reactions were measured
up to (n,10n), results were compared with the data from EXFOR, EAF, and
with calculated values from TALYS code with good agreement. Cross-
sections for reactions over 40 MeV and (n,4n) are unique and were measured
for the first time. Part of the data has been already published and presented on
international conferences.




                                      31
Resumé
          Produkce vysokoenergetických neutronů ve spalačních reakcích a
jejich transport v systému masivního olověného terče a uranového blanketu
byly studovány v rámci mezinárodního projektu „Energy and Transmutation
of Radioactive Waste“. Sestava nazvaná „Energy plus Transmutation“
umístěná v Dubně, Rusko, byla ozářena deuterony o energiích 1,6 GeV až
4 GeV. Pro měření neutronů byly použity prahové reakce na aktivačních
detektorech z Al, Au, Bi, Co, In, Ta a Y. Aktivované fólie byly měřeny
pomocí HPGe detektorů. Při analýze získaných dat byla aplikována řada
spektroskopických korekcí za účelem nalezení výtěžku sledovaných isotopů.
Experimentální data byla nakonec porovnána s výsledky simulací sestavy v
MCNPX. Tyto experimenty navázaly na předchozí výzkum zmíněné sestavy
pomocí relativistických protonů. Pro deuteronové experimenty nebyla na
rozdíl od protonových pozorována žádná výraznější neshoda v produkci
vysokoenergetických neutronů do zpětných úhlů.
          Účinné průřezy užitých prahových reakcí byly změřeny pomocí
quasi-monoenergetických neutronových zdrojů v Ústavu jaderné fyziky, Řež,
a ve Svedbergově laboratoři, Uppsala, Švédsko. Bylo provedeno celkem 11
ozařování v energetickém rozpětí 17 až 94 MeV. Prahové reakce byly
změřeny až do (n,10n), výsledky byly porovnány s daty z databází EXFOR,
EAF a s hodnotami vypočtenými pomocí programu TALYS. Byla
pozorována dobrá shoda. Účinné průřezy pro reakce nad 40 MeV a (n,4n)
jsou unikátní a byly změřeny vůbec poprvé. Část naměřených dat již byla
publikována a prezentována na mezinárodních konferencích.




                                   32

								
To top