Neutron Background of Composite Low-Enriched Uranium Fuel of the IVG.1M Research Reactor

Abstract

In 2010, within the framework of the Kazakhstan USA cooperation under the auspices of the IAEA, the IVG.1M reactor was included in the program for converting research reactors cores to low enriched uranium fuel.After the conversion to low enriched uranium is completed, the IVG.1M reactor operation will continue, while the duration of its operation will be determined by the availability of fresh fuel to replace the core after the next campaign and the ability to ensure safe storage of SNF removed from the core. Safe storage conditions are assessed in terms of nuclear and radiation safety.Radiation safety of storage of SNF from research reactors is primarily achieved by solving the problems of protection against γ radiation, and neutron radiation is generally not considered due to its significantly lower intensity in comparison with γ radiation. Concerning the new low enriched uranium fuel of the IVG.1M reactor, which is characterized by a set of elements with low and medium atomic mass, where the (α, n) reaction is possible, the assessment of the neutron component is a necessary procedure to ensure the safe fuel storage.The goal of this research is to estimate the neutron radiation level of fresh and irradiated fuel of the IVG.1M reactor and to develop recommendations for safe long term SNF storage.To achieve this goal, the authors of the article created a full scale computational 3D model of the reactor, carried out neutron characterization of the reactor core and studies of the evolutionary fuel composition, and calculated the neutron radiation levels of fresh and irradiated fuel.The research was carried out using verified computational codes MCNP5 and Sources 4C, high precision experimental EXFOR and computational ENDSF data, as well as evaluated nuclear data libraries.