Jitka Vrzalova

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.

Study of cross-sections of yttrium (n,xn) threshold reactions

Currently the development of the nuclear systems is heading to systems with fast neutrons instead of thermal ones. Such systems are mainly fast reactors of gen eration IV family and accelerator driven systems. Unfortunately the possibilities of monito ring fast neutrons are limited. One of the possible principles is to use activation detectors. It h as shown up that yttrium is very good candidate to act as the activation detector of the fast neutr ons. The advantages of yttrium are namely its (n, xn) threshold reactions and the fact that its only one natural ly occurring isotope. To be possible to use yttrium as the activation detector it is ne cessary to know the cross-sections of the (n,xn) reactions sufficiently good. This condition is fulfilled o nly in case of the89Y(n,2n)88Y reaction. For higher orders of reactions there are almost no experimental data. For this reason a series of experiment were made using quasi m ono-energetic neutron source based on the reaction of protons with 7Li target at Nuclear Physics Institute of ASCR in Rez. Special attention was paid to the 89Y(n,3n)87Y reaction. In this case the nuclei are produced both in the ground state and in the isomeric state. The half-lives ar 79.8 hours for the ground state and 13.38 hours for the isomeric state. The isomeric state decay s m inly through the gamma transition to the ground state. The beta decay of the isomeric state is wi thin our accuracy negligible. The cross-sections of both cases of products were analyzed and c ompared with existing experimental data, calculated models and evaluated values.

Studies of neutron cross-sections important for spallation experiments using the activation method

A series of experiments devoted to studies of neutron cross-sections by activation method was carried out. The cross-sections of various threshold reactions were studied by means of different quasi-monoenergetic neutron sources with energies from 14 MeV up to 100 MeV. Threshold reactions in various materials are among other used to measure fast neutron fields produced during accelerator driven system studies. For this reason our measurements of neutron cross-sections are crucial. At present, neither experimental nor evaluated data above 30 MeV are available for neutron threshold reactions in Au, I and In published in this proceedings. We studied materials in the form of thin foils and compared our data with the calculations preformed using the deterministic code TALYS 1.4.