Herein, an investigation of a deeply subcritical uranium assembly irradiated by a high-energy deuteron beam is presented. The determination of the total number of fission events is a key task in these investigations. Thus, this study is focused on the investigation of the number of fission events induced by deuterons, neutrons, and protons inside the deuteron beam volume. To measure the number of fission products in uranium activation detectors, germanium gamma detectors have been used. Furthermore, the total number of fission events has been measured by applying Solid State Nuclear Track Detectors (SSNTDs). The new method for determining the number of fissions using activation detectors is compared with the SSNTD and Monte Carlo (MC) methods. The method estimates the total number of fission events and agrees with the results obtained using the SSNTD and MC methods. The experiments were conducted at JINR, Dubna, Russia.

The fission rates of natural uranium and thorium were measured in the particle field of Quinta, a 512 kg natural uranium target–blanket sub-critical assembly. The Quinta assembly was irradiated with deuterons of energy 4 GeV from the Nuclotron accelerator of the Joint Institute for Nuclear Research (JINR), Dubna, Russia. Fission rates of uranium and thorium were measured using Gamma spectroscopy and fission track techniques. The production rate of 239Np was also measured. The obtained experimental results were compared with Monte Carlo predictions using the MCNPX 2.7 code employing the physics and fission–evaporation models of INCL4–ABLA, CEM03.03 and LAQGSM03.03. Some of the neutronic characteristics of the Quinta are compared with the “Energy plus Transmutation (EpT)” subcritical assembly, which is composed of a lead target and natU blanket. This comparison clearly demonstrates the importance of target material, neutron moderator and reflector types on the performance of a spallation neutron driven subcritical system.

A. Wojciechowski, Y.C. Lim, V. Stepanenko, M. Bidus, I. Zhuk, K. Husak, S. Korneev, A. Potapenko, A. Safronova, V. Voronko, V. Sotnikov, M. Artiushenko National Center for Nuclear Reaserch, 05-400 Otwock-Swierk, Poland Laboratory of Information Technologies, JINR, Russia Institute of Atomic Energy, Pyongyang, DPRK University of Science and Technology, Krakow, Poland JIENR Sosny near Minsk, Belarus KIPT, Kharkov, Ukraine (for collaboration ”Energy & Transmutation of Radioactive Wastes”)

A. Wojciechowski, Y.C. Lim, I. Zhuk, K. Husak, S. Korneev, A. Potapenko, A. Safronova, V. Voronko, V. Sotnikov, M. Artiushenko National Center for Nuclear Reaserch, 05-400 Otwock-Swierk, Poland Laboratory of Information Technologies, JINR, Russia Institute of Atomic Energy, Pyongyang, DPRK JIENR Sosny near Minsk, Belarus KIPT, Kharkov, Ukraine (for collaboration ”Energy & Transmutation of Radioactive Wastes”)

Calibration factors w, for determination of fission rate in metallic foils of nat U, 235 U, 232 Th, nat Pb and 197 Au were determined for foils in contact with synthetic mica track detectors. Proton-induced fission at proton energies of 0.7 GeV and 1.5 GeV were used. Using our experimental results as well as those of the other authors, w for different foil-mica systems were determined. Two methods were used to calculate w, relative to the calibration factor for uranium-mica system, which has been obtained in a standard neutron field of energy 14.7 MeV. One of these methods requires the knowledge of the mean range of the fission fragments in the foils of interest and other method needs information on the values of the fission cross-sections at the required energies as well as the density of the tracks recorded in the track detectors in contact with the foil surfaces. The obtained w-values were compared with Monte Carlo calculations and good agreements were found. It is shown that a calibration factor obtained at low energy neutron induced fissions in uranium isotopes deviates only by less than 10% from those obtained at relativistic proton induced fissions.

Detection of fission and spallation–evaporation residues resulting from interaction of relativistic protons with uranium, lead and gold targets in mica track detectors is investigated by the Monte Carlo method and using experimental data available in literature. It is shown that the contribution of spallation–evaporation residues to total track density is strongly dependent on target thickness and is the least for thick targets. This contribution in the case of thick target materials with Z≥79 is less than or is within the statistical uncertainty of a typical track density measurement. Although our results on registration and detection of the spallation residues in mica are based on the interactions of uranium and lead with protons at 1AGeV and gold with protons at 0.8AGeV, they are applicable to all targets with Z≥79 and for proton energies much higher than 1GeV.

Recently new ADS scheme was proposed aimed at energy production and transmutation of radioactive wastes. Main physical idea of this approach is to use deep subcritical and quasi-infinite (negligible neutron leakage) multiplying target of natural (depleted) uranium or thorium combined with similar to 10 GeV incident beam. In accordance with semi-phenomenological estimations such ADS provides large enough beam energy gain and extremely hard neutron spectrum inside of subcritical core that can ensure effective burning of core material as well as spent reactor fuel added to the initial core.During 2009-2011 the experiments with massive (315 kg and 500 kg) natural uranium targets irradiated by deuteron beam from JINR NUCLOTRON with energy from 1 to 6 GeV have been carried out. Preliminary data on the energy spectra of prompt neutrons within the targets and the time spectra of delayed neutrons after fission of the target nuclei were obtained. Beside that there were measured spatial distributions of fission rates and Pu-239 production. Obtained results confirm a validity of basic ideas of proposed ADS scheme and provide solid grounds for planning of future experiments with quasi-infinite (22 tons) target of depleted uranium available for the " Energy and Transmutation RAW" collaboration at JINR.

Prompt and delayed neutrons (DN) from pulsed irradiation of geometrically identical natural uranium and lead targets by 1 and 4 GeV deuterons were measured at NUCLOTRON facility of Joint Institute for Nuclear Research. The massive hexagonal shaped targets were surrounded by 10 cm lead blanket. Neutrons were measured by the assembly of He-3 counters embedded in moderator and by threshold activation detectors. The DN decay curves were analysed for both targets and information on fission properties for massive (similar to 315 kg) uranium target was extracted. The obtained experimental information could be useful for verification of INC and transport codes. The results of this experiment are important for development of advanced ADS systems and other applications.

Calibration factors w, for determination of fission rate in metallic foils of natU, 235U, 232Th, natPb and 197Au were determined for foils in contact with synthetic mica track detectors. Proton-induced fission at proton energies of 0.7GeV and 1.5GeV were used. Using our experimental results as well as those of the other authors, w for different foil–mica systems were determined. Two methods were used to calculate w, relative to the calibration factor for uranium–mica system, which has been obtained in a standard neutron field of energy 14.7MeV. One of these methods requires the knowledge of the mean range of the fission fragments in the foils of interest and other method needs information on the values of the fission cross-sections at the required energies as well as the density of the tracks recorded in the track detectors in contact with the foil surfaces. The obtained w-values were compared with Monte Carlo calculations and good agreements were found. It is shown that a calibration factor obtained at low energy neutron induced fissions in uranium isotopes deviates only by less than 10% from those obtained at relativistic proton induced fissions.

Experiments with a U/Pb assembly (lead target with a natural uranium blanket) were carried out using the nuclotron accelerator of the Joint Institute for Nuclear Research (JINR). The profile of the deuteron beam (E=1.26GeV/nucleon) and the spatial distribution of high-energy neutrons (En>30MeV) were determined using deuteron and high-energy neutron induced fission in natural lead. Artificial mica track detectors were used to register the fission tracks from natPb(d,f) and natPb(n,f) reactions. The MCNPX 2.5e code was used to simulate the influence of the beam profile and the position of the beam centroid on the target, on the spatial distribution of the secondary particles around the target. Results of the experiment and its simulation are presented.

The new method of experimental investigation of porous media behavior under intense heating is proposed. The experimental results are compared to numerical and analytical simulation. Application of the supposed experimental approach to the inertial confinement target design is discussed.