This article is devoted to an overview of the conducted work and the current status of decommissioning of the world’s first BN-350 industrial fast neutron reactor. The reactor was put into operation on 16 July 1973 in Aktau. In 1999, the government of Kazakhstan decided to shut down the reactor, and from that moment to the present, it has been in the decommissioning stage. All work on decommissioning the reactor facility was grouped into five stages. The first stage was completed in 2010 when the spent fuel of the BN-350 reactor was placed for long-term storage. The second stage is nearing completion. Research is currently underway to develop technologies for processing radioactive sodium. The goal of the third and fourth stages of the BN-350 reactor decommissioning is the comprehensive processing of liquid and solid radioactive waste. Now such waste is stored in special storage directly on the territory of the nuclear power plant.

This study presents the radiological characterization of 15 solid radioactive waste samples originating from the BN-350 sodium-cooled fast reactor (Kazakhstan) during its decommissioning phase. The studied materials include components of ventilation and wastewater treatment systems, pipeline elements and various operational tools. The objective of the study was to determine the activity levels of the samples and to assess appropriate pathways for their subsequent management and processing. The results indicate that all studied materials fall within the category of low-level radioactive waste. Gamma spectrometric analysis shows that Cs-137 is the dominant and only identified gamma-emitting radionuclide contributing to the activity of the studied samples.

The processing and decontamination of metallic radioactive waste is one of the pressing challenges associated with the utilization of nuclear energy. One of the methods used for the treatment and purification of metallic waste is electroslag remelting. This paper discusses the modeling of the thermophysical state of the crystallizer in an electroslag remelting facility using the ANSYS FLUENT software package. A geometric model and a computational model were developed, and calculations of the crystallizer thermophysical behavior were performed under conditions corresponding to previously conducted experimental runs. The simulation results illustrate the thermal behavior of the crystallizer during the cooling of the metallic melt formed within it. The obtained results confirm the physical consistency of the adopted boundary conditions and heat transfer parameters.

The paper presents experimental findings on the temperature measurement of structural material samples exposed to radiation heating during pulsed irradiation at the IGR research reactor. To record the temperature, an in-pile experimental device was specifically designed, consisting of a protective ampoule with an ultra-low-pressure environment to house the test samples. Thermocouples were embedded directly into the sample structures to enable precise temperature measurements within the materials. Temperature responses in 12 materials have been examined, including refractory metals, high-alloy steels, and aluminum alloys. Distinct heating patterns were identified that influenced by their physical and radiation properties of the materials. These results provide valuable data for refining thermal engineering models and enhancing the accuracy of calculations in the design of equipment for nuclear installations.

Modern nuclear energy faces the problem of the accumulation, storage, and management of radioactive waste. For radioactive metal waste (RMW), one of the main tasks is to reduce its volume, carry out partial or complete decontamination, and convert it into a compact and stable form that can be safely stored. In this regard, remelting methods are of great interest as they enable volume reduction in radioactive metal waste, redistribute radioactive impurities, and produce a compact metal product that is convenient for further handling. This study presents the development and experimental testing of an electroslag remelting (ESR) facility designed for investigations of RMW processing. The operability of the facility was initially confirmed using a stainless-steel pipe as an RMW simulator. The experiment showed that the developed facility can successfully remelt metal pipes and produce a compact metal product of a required shape, suitable for further handling and storage. Further experiments were performed using real radioactively contaminated 12Cr18Ni10Ti steel pipes from the IVG.1 reactor technological channel. Gamma-spectrometric measurements showed a significant reduction in radionuclide activity in the remelted metal ingots compared with the initial materials. Thus, the obtained results demonstrate the applicability of the developed ESR facility for experimental investigations of RMW processing.

To model thermal processes that occur in the core of the Impulse Graphite Reactor (IGR), the Institute of Atomic Energy of the RSE NNC RK uses a designed three-dimensional thermophysical model. This model has a high degree of detail and allows for thermophysical calculations of the core parameters in various modes of operation, including at maximum energy release and in the event of emergency situations. The input data are multidimensional arrays with the distribution of energy release in the core, obtained after neutronic calculations. The result of the modeling is an array of data containing the temperature values of each unit of the model at each moment in time. When designing the thermophysical model, new non-standard approaches were implemented that were not previously used. This paper shows the features of modeling the IGR core in the ANSYS Mechanical APDL environment, which made it possible to obtain a high-quality tool for studying the temperature modes of the reactor.