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The paper presents calculations of the thermal power distribution in the reactor core (RC) of the WWR-SM research nuclear reactor of the Institute of Nuclear Physics of the Academy of Sciences of the Republic of Uzbekistan, settlement Ulugbek, Tashkent, both for all fuel assemblies loaded into the core and for each fuel element of a separate fuel assembly. These calculations were carried out for RC configurations with a different number of fuel assemblies – 18, 20, and 24. The power distribution reactor core was performed using the IRT-2D code. A detailed simulation of the power distribution in the fuel element was performed using the MCNP4C code, while the fuel elements were modeled as square pipes with straight angles without rounding. The power distribution was calculated for each side of each fuel tube and divided into 15 axial nodes. The results of modeling of the thermal-hydraulic state were obtained using the PLTEMP code for various RC configurations. In the calculations, it was assumed, that the inlet water temperature is 45 and 48 °C for all RC configurations, the heat hydraulic parameters were taken from the calculation of the flow rate of the first circuit through the core 1250 m3/h. An analysis of the thermal power distribution of nuclear fuel in the reactor core of the WWR-SM research reactor showed that even with a conservative approach, permissible operating modes are not exceeded. During the operation of the three main circulation pumps, which provide the coolant flow through the core at the level of 1250 m3/h, the heat exchange crisis does not occur in the most energy-stressed fuel assemblies, namely, the temperature of the fuel rod clad and coolant remains below the permissible limits.

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In this paper, the physical inventory taking of nuclear materials (NM) (under safeguards application) at the nuclear fuel research laboratory at Inshas, Egypt has been considered. NM with different forms and sizes were verified. The verification method based on non-destructive measurements of gamma radiation emitted from NM was tested. Monte Carlo method (MCNP5) and Multi-Group Analysis software (MGAU Genie 2000, version 3.2) were used to estimate 235U mass content in the studied forms. Some of the parameters which affect NM mass estimation were also investigated. The proposed procedure covers different forms found at the nuclear fuel research laboratory such as pellets, sludge, and rods. The average accuracies for the estimated 235U masses ranged between -0.351 and -1.005 %, while the precision was about 2.065 and 7.45 % for MCNP5 and MGAU respectively. These results are found to be acceptable within the limits of the International Target Values.

, (Carassius gibelio), 8 -10 . 137 Cs 8 -10 (5 22 ) . 137 Cs 5 (T 1/2 = 433 162 ) 5,6 , 22 (T 1/2 = 78 4 ) . 137 Cs () 22 , 137 Cs ( -1 ) 1,8 (0,0089 0,0005 -1 0,016 0,002 -1 ) - .

Using the X-ray diffraction method, the phase content of brown ceramics of lava-like fuel-containing materials of the “New Safe Confinement – Shelter Object” Complex was investigated. Their type was identified and crystalline phase composition was estimated. Characterization of the silicate glass phase was also carried out. Uranium oxide is a derivative of “initial” reactor materials before the Chornobyl accident, cubic and tetragonal zirconium oxide and silicate zirconium were produced during the accident, and some silicium oxides, uranium, aluminum, and calcium silicates were formed during the glass matrix crystallization in the course of 33 years after the accident. Uranium oxide in the inclusions oxidized to UO2.34, it has cubic lattice, which is metastable under such oxygen content. These inclusions exist due to their compaction in the glass matrix. Their increased volume, due to oxidation of uranium oxide, is the cause of cracks in the material. Under degradation of brown ceramics, 20 - 25 % of uranium oxide from inclusions transfer into U3O8 oxide with grain degradation to micron and submicron levels. Currently, the crystallization of the glass matrix is at the stable development stage. A range of silicium oxides and uranium, aluminum and calcium silicates were formed during crystallization. There are typical and non-typical phases in the viewpoint of crystallization of industrial silicate glass.

Herein we present the results of studying the effects of different isotopes of magnesium, magnetic 25Mg and nonmagnetic 24Mg, upon the post-radiation recovery of yeast cells, S. cerevisiae, irradiated by short-wave UV light (240 - 260 nm) or ionizing radiation (300 Gy). The recovery process of the cells enriched with the magnetic 25Mg proceeds two times faster than the post-radiation recovery of the cells, enriched with the nonmagnetic 24Mg. After gamma-irradiation, the fraction of the irreversible damages in the cells enriched with 25Mg was 50 - 60 % less than in the cells enriched with 24Mg. Thus, the magnetic isotope effect has been detected, i.e. – the acceleration of post-radiation recovery of the cells by the magnetic isotope’s nuclear spin of magnesium (nuclear spin catalysis). Obtained results demonsrate the fundamental possibility of creating new radioprotectors and radiomitigators based on stable magnetic isotopes.

A new statistical interpretation of the nuclear collective states is suggested and applied recently in rare earths and actinide nuclei by the two-neutron transfer reactions in terms of the nearest neighbor-spacing distributions (NNSDs). Experimental NNSDs were obtained by using the complete and pure sequences of the collective states through an unfolding procedure. The two-neutron transfer reactions allow to obtain such a sequence of the collective states that meets the requirements for a statistical analysis. Their theoretical analysis is based on the linear approximation of a repulsion level density within the Wigner-Dyson theory. This approximation is successful to evaluate separately the Wigner chaos and Poisson order contributions. We found an intermediate behavior of NNSDs between the Wigner and Poisson limits. NNSDs turn out to be shifted from a chaos to order with increasing the length of spectra and the angular momentum of collective states. Perspectives for the statistical analysis of the symmetry breaking of states with the fixed projection of angular momenta $K$ are discussed.

Radiogenic changes in the blood system of Myodes glareolus inhabiting the sites of the 30-km ChNPP zone with different levels of radiation contamination were studied. It is shown that the chronic ionizing radiation exposure results in disorders in the animals' hemopoiesis. The imbalance in all blood cell lineages, especially erythroid one, was revealed. Animals inhabiting highly contaminated areas and exposed to the higher radiation doses had more steady changes in blood parameters, in particular their significant decrease. In all groups of the examined animals, in addition to radiation induced effects, compensatory repair processes were observed. They were manifested in the intensification of organism self-protection by activating the lymphoid components of immune system.