Prediction of the Material Composition of the VVER-type Reactor Burned Pellet with Use of Neutron-Physical Codes

The purpose of neutron-physical calculations is typically isotopic composition of the fuel elements. However, in solving materials science problems related to nuclear fuel, researchers are usually interested in elemental composition of the fuel pellets, because the chemical and thermal physic properties are the same for differentisotopes of one chemical element. Nevertheless, for modeling of the elemental composition one should perform calculation of the isotopic composition and carry out the summation over all isotopes of a given chemical element. The development of computational tools allows the use of improved methods and codes, which held the consequent solution of tasks of heat conduction, neutron transport, and kinetics ofnuclides transformation. Thus the calculations take into account the dependence of the thermal conductivity from the changing isotopic composition and fuel burnup. This allows to perform neutron-physical and thermal-physical calculations of the reactor with detailed temperature distribution, taking into account temperature dependence of thermal conductivity and other characteristics. This approach was applied to calculations of the fuel pellet of the VVER type reactor and calculation of its elemental composition. Keywords: materials science, elemental composition, fuel pellet

COVID-19 Features in Patients with Multiple Sclerosis: Main Approaches to Their Management, Treatment, and Vaccination

The COVID-19 pandemic calls for correct and evidence-based decisions regarding management and treatment of patients with multiple sclerosis. Information on researches, clinical cases, and recommendations for treatment of such patients during the pandemic should be classified. We report COVID-19 features in patients with multiple sclerosis, risk factors for infection and development of severe disease. We also describe management strategies for multiple sclerosis: from relapse treatment to the selection of disease-modifying therapies focusing on patients safety. We analyze the latest observational and comparative studies, clinical cases of multiple sclerosis patients vaccination and demyelinating disease onset after COVID-19 or vaccination

Modeling of Analytical-Experimental Benchmark on Irradiation of Nitride Fuel in BN-600 Reactor in the SCALE6 Code

In this work was carried out the simulation in the SCALE6 code of an experiment on the BN-600 reactor on irradiating of fuel assemblies, containing samples of mixed nitride uranium-plutonium fuel. A comparison of the results for SCALE6 on the results of other codes is presented. The results of an estimation of uncertainties in the calculated data connected with uncertainties of an irradiation of an experimental sample and used neutron cross-sections library. Discussion of possible differences between analytical and experimental results is given