THE TRANSMUTATION MODELING FOR PLUTONIUM AND MINOR ACTINIDES IN THE TWO-ZONE SUBCRITICAL REACTOR

The investigations directed to plutonium and minor actinides transmutations for two-zone subcritical reactor is considered in present paper. The distributions of thermal and fast neutrons in the subcritical system were obtained. The distributions of fission and capture reaction rates for 237Np and 243Am were analyzed from viewpoint of minor actinides transmutation. The transmutation simulations for different distributions of pin targets were carried out within the scope of this paper. The obtained modeling results for different nuclear waste isotopes were analyzed and discussed.

A Possibility of Detecting Fast Neutrons in a 10B Solid-gas Detector

The possibility of detecting thermal and fast neutrons in 10B solid-gas detector is considered. The simulation of the neutron detection process shows a significant difference in the detector signals caused by neutrons of different energies. An experimental verification of the detector’s operation was performed using W-Be photoneutron source with different ratio of fast and thermal neutrons incident on the detector. The measured amplitude spectra of the signals for different neutron energies were compared with the simulation results. The qualitative agreement between experimental and calculated data indicates the possibility of using this detector for recording thermal and fast neutrons.

Irradiation Creep of Uranium-Plutonium Nitride Fuel and Serviceability of Fuel Element

Article discusses experimental data on creep of (U,Pu)N and other uranium compounds, and possible mechanism of mass-transfer. Proposed equation describes the following creep features: weak temperature dependence at T < 1000°C, creep acceleration in a fuel with micron-sized grains, and acceleration with the content of second phases formed by impurities and fission products. The difference in creep behavior in reactors with thermal and fast neutrons environmentsis discussed. Comparison of irradiation creep of nitride fuel and properties of cladding materials shows that under parameters of fast reactors and typical design of fuel element it is impossible to implement restraining of external nitride swelling. As initial porosity in the fuel will not compensate the nitride swelling, the cladding of fuel element will work in a mode of following the changing of fuel size. Some suggestions on the cladding material properties are done.

Response Functions of a Cs2LiYCl6 Scintillator to Neutron and Gamma Radiation

A new scintillator, CLYC, has been investigated for possible use in neutron spectrometry. This sensor provides neutron detection for both thermal and fast neutrons from the reactions 6Li(n,α) and 35Cl(n,p), respectively. This work primarily focuses on the detection of fast neutrons since there is currently no sensor that can accurately and efficiently provide information about their incident neutron energy. Conventional methods of fast neutron detection have been based on utilizing materials that use the elastic scattering process of neutrons on 1H to create recoil protons or by thermalizing and capturing these neutrons at thermal energies. Both approaches have drawbacks and are complex in deriving the energy spectrum through the unfolding process. The CLYC scintillator uses a distinct proton peak, whereby the position on the spectrum is proportional to the energy of the incident neutron. The response function of this detector has been simulated using Monte Carlo N-Particle eXtended code (MCNPX) for gamma-rays and neutrons of different energies. The obtained data has been discussed and analyzed.

TIME-PROJECTION-CHAMBERS WITH OPTICAL READOUT FOR DARK MATTER, DOUBLE BETA DECAY, AND NEUTRON MEASUREMENTS

In recent years, there have been impressive advances in the technology of cameras using charged coupled devices (CCD's) and electron multiplying charged coupled devices (EMCCD's) that make possible a number of applications for the detection of ionizing radiation. The new cameras have quantum efficiencies exceeding 90%, effective noise levels less than one electron per pixel, and can be made to detect light ranging from the ultraviolet to the infrared. When combined with photomultiplier tubes (PMT's), and when used with Time-Projection-Chambers (TPC's) that contain narrow gap mesh charge amplification stages and scintillating gas compositions, these cameras can be used to provide three-dimensional images of particle tracks. There are many applications for such devices, including direction sensitive searches for dark matter, measurements of thermal and fast neutrons, and searches for double-beta-decay. I will describe the operation of optical TPC's and their various applications in this review article.