Pavel Tichy

Future usage of quasi-infinite depleted uranium target (BURAN) for benchmark studies

T he development of advanced nuclear systems needs reliable and accurate simulation codes. Significant necessity are benchmarks of Monte Carlo simulation programs (e.g. MCNPX), which are important for studies of neutron production, transport and transmutatio n of radioactive materials by produced neutrons. Experiments with various setups consisting of lead, natural uranium and graphite irradiated by relativistic protons and deuterons are used for such purposes at JINR Dubna. Experiments with new setup called „ Buran“ should start soon. Preliminary calculations (in MCNPX code) of proton and deuteron beam transport through this setup and neutron production and fluxes in different places of such setup have been made. Representative results are shown and discussed

Monte Carlo simulations and experimental results on neutron production in the uranium spallation target QUINTA irradiated with 660 MeV protons

The activation experiment was performed using the accelerated beam of Phasotron accelerator at the Joint Institute for Nuclear Research (JINR). The natural uranium spallation target QUINTA was irradiated with protons with energy 660 MeV. Monte Carlo simulations of neutron production were performed using the Geant4 code. The number of leakage neutrons from the sections of the uranium target surrounded by the lead shielding and the number of leakage neutrons from lead were determined. The total number of fissions in the setup QUINTA was determined. Experimental values of reaction rates for the produced nuclei in the 127I sample were obtained and several values of reaction rates were compared with the results of simulations. Experimentally determined fluence of neutrons in energy interval 10-175 MeV using the (n,xn) reactions in the 127I(NaI) sample was compared with the results of simulations. Possibility of transmutation of the long-lived radionuclide 129I in the QUINTA setup was estimated.

Determination of the neutron flux by the temperature differences at the massive spallation uranium target QUINTA

There are several possibilities of the neutron flux determination inside of the facility. The most using one method is the determination of the neutron flux by threshold foils (detectors). This method is complicated to analyze. Irradiated foils need to be measured by gamma spectrometry and it usually takes a few weeks to get results of the neutron flux determination. Other methods are also available. One of them is the determination of the neutron flux by measuring of released heat inside of the facility. This method allows online measuring and is greatly variable to measure an unlimited number of positions in the facility with a low accrual of the cost. The research project to the topic of this type of neutron flux determination is led by Dzhelepov Laboratory of Nuclear Problems (DLNP) at the group of J. Adam. The temperature differences are measured by high accuracy thermocouples. Two experiments took place during 2015 at the massive spallation uranium target QUINTA at the facility Phasotron at JINR. Another four experiments are planned during 2016.

Neutron Flux Determination By High Accuracy Temperature Measurement

This paper is focused on the description of developing a method to determine neutron flux by high-accuracy temperature measurement. The paper deals with the procedure of sophisticated measurement, its analyzation and brings part of reached results. The method is in development in the research group aimed at ADS in the DLNP, JINR. Since the first experiment in November 2015, another 5 experiments have been performed and due to progress, the future experiment seems to be closer to reach relatively cheap probe with the ability to determine the neutron flux online.

Determination And Monte Carlo Simulations Of Neutron Flux Inside Spallation Target Quinta

This paper deals with experiments performed with natural uranium spallation target QUINTA irradiated by 4 GeV and 8 GeV deuteron beam from Nuclotron accelerator and by 660 MeV proton beam from Phasotron accelerator. Reaction rates for Na-24, Co-57, Co-58, Bi-205 and Bi-206 production in Al, Co and Pb threshold radioactivation foils were determined. The data served for calculation of the experimental neutron flux inside the QUINTA target for the Phasotron experiment. Simulations in Monte Carlo code MCNPX 2.7 were performed and compared to the experimental data. In the current state of research, the data evaluation and simulations are preliminary.

Current research on ADS at the Joint Institute for Nuclear Research

The research on Accelerator Driven Systems (ADS) has more than 20 years tradition at the Joint Institute for Nuclear Research. Since 2010, the most experiments have been performed with a~spallation target composed of 512 kg of natural uranium. This target called QUINTA was irradiated with proton and deuteron beams of high energies. Currently, final preparations of a new spallation target BURAN consisting of 21 tons of depleted uranium are under way. The main tasks of the project are experimental investigation of neutron production inside the spallation target, possibility of natural thorium utilization and transmutation of the minor actinides and long-lived fission products. The supplementary field of interest is a measurement of nuclear data and verification of nuclear codes and theoretical models related to the ADS technologies.

Determination of the neutron flux inside spallation target with the use of threshold activation detectors

Neutron flux is an important parameter for Accelerated Driven Systems. Density of the neutron flux is different in various positions inside a spallation target. The neutron flux can be obtained with the use of threshold activation detectors. An experiment with the spallation target made of 512 kg natural uranium and deuteron beam with energy 8 GeV was performed at the Joint Institute for Nuclear Research. Ten samples of Co-59 were irradiated of the secondary neutrons inside the spallation target at different positions. The reaction rates were determined by the gamma-ray spectroscopy with threshold activation detectors. The neutron flux was calculated by reaction rates. The experimental results were compared with Monte Carlo simulations.

Nuclear data for advanced nuclear systems

The development of advanced nuclear systems as generation IV reactors, accelerator driven systems and fusion reactors needs new reliable high quality nuclear data. The relativistic proton and light ion accelerator Nuclotron at JINR Dubna was used to study cross-sections of deuteron reactions on copper. The obtained excitation functions of different radionuclide productions by relativistic deuterons on copper were used for determination of beam integral during last experiment with E+T set-up using copper foil. The discrepancy which we had between beam integral values obtained by means of two aluminium foil monitors was resolved by this new analysis. The accurate cross-sections of neutron reactions in wide energy range and relativistic light ion reactions are the most important part of the experimental studies. We used two quasi mono-energetic neutron sources for studies of neutron reaction cross-sections on broad set of materials. The first facility is the neutron source based on the cyclotron at the Nuclear Physics Institute of ASCR, Řež. It provides neutron beams in the energy range from 14 MeV up to 35 MeV. The second neutron source is built around the cyclotron at TSL Uppsala. This facility provides neutron beam in the energy range from 14 MeV up to 200 MeV. Both facilities are open for European users within the framework of project CHANDA.

Studies of relativistic deuteron reaction cross-sections on copper by activation method

The cross-sections of relativistic deuteron reactions on natural copper were studied by means of activation method. Lack of such experimental cross-section values prevents the use of copper foils from beam integral monitoring. The copper foils were irradiated during experiments at the Joint Institute for Nuclear Research (JINR) in Dubna, Russia. The deuteron beams produced by the JINR Nuclotron accelerator had energies ranging from 1 GeV up to 8 GeV. Residual nuclides were measured using the gamma spectrometry. The copper monitors can help us to improve the beam integral determination during further accelerator-driven system studies. Another goal of our studies is the assessment of nuclear spallation models in comparison with the experimental data.