Lukas Zavorka

Studies of deuteron and neutron cross-sections important for ADS research

The collaboration Energy and Transmutation of Radioactive Waste uses different setups consisting of lead, natural uranium and graphite irradiated by relativistic protons and deuterons to study transmutation of radioactive materials by produced neutrons. The activation samples are used to determine integral of proton or deuteron beams and also produced neutron flux in different places of experimental set-ups. Unfortunately almost no experimental cross-section data for deuterons with GeV energies are available. The similar situation is also for threshold (n,xn) reactions of neutrons with higher energies. Therefore we carried out series of experiments devoted to determination of deuteron reactions on copper during uranium target QUINTA irradiations by deuterons with energies from 1 GeV up to 8 GeV. The cross-sections of various threshold reactions were studied by means of different quasi-monoenergetic neutron sources with possible energies from 14 MeV up to 100 MeV. Knowledge of such cross-sections is very important for all Accelerator Driven System studies.

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 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.

Reaction rates of residual nuclei produced of 59 Co at the target QUINTA

In December 2013, an experiment with the natural uranium spallation target QUINTA was performed at the Joint Institute for Nuclear Research (JINR). The mass of the QUINTA setup is 512 kg. It consist of five hexagonal sections. The experimental samples of Co have been irradiated in the field of secondary neutrons generated by the deuteron beam at the Nuclotron accelerator at JINR. Energy of the deuteron beam was 4 AGeV. During the experiment, samples were situated in different positions inside the assembly and after irradiation they were measured at the high-purity germanium semiconductor detectors. Experimental reaction rates of residual nuclei were determined and compared with reaction rates calculated with the MCNPX code.

A summary of experimental results on the reactions in uranium samples irradiated with a deuteron beam of energies up to 8 GeV at the QUINTA target

Natural uranium samples have been irradiated in a neutron field generated via spallation reaction at the QUINTA target (500 kg of U). The dependence of the reaction rates of residual nuclei produced inside the samples on the incident deuteron energy of the maximum value of 8 GeV has been investigated. Both the activation measurement technique and the gamma-ray spectrometry have been used. A comparison with MCNPX calculation is enclosed. Nevertheless, the results are still preliminary and also need to be verified by providing further experiments.