The article presents the results of a radiation survey carried out on the liquid radioactive waste disposal system of decommissioned MR and RFT research reactors. The system is located in the buildings adjacent to the dismantled reactor building on the territory of the Kurchatov Institute national research center. The results of the visual and radiation survey carried out on the equipment and premises of the disposal system for liquid radioactive waste will inform the development of design documentation for its elimination. Following the removal of liquid radioactive waste from storage tanks, the equipment and building structures at this location should be dismantled. The carrying out of recommended works will complete the decommissioning of MR and RFT research reactors. Further, the site of the reactor buildings and their auxiliary systems will be rehabilitated to achieve a radiation situation that meets the sanitary and hygienic standards for the group B personnel.

To study the spatial distribution of the intensity of an X-ray source of electric discharge plasma, a new-type coded aperture, which is a structure of intersecting mutually perpendicular transparent and opaque strips with the widths selected using a random number generator, has been used. The radiation passed through the coded aperture has produced a complex pattern of the coded image, which has been recorded on a Fuji TR fluorescent imaging plate without a protective coating. A mathematical procedure based on the iterative method of solving an incorrectly posed problem given by the Fredholm integral equation of the first kind has been applied to reconstruct the spatial distribution of plasma radiation intensity from this pattern. It has been shown that the use of the coded aperture not only has increased significantly the light intensity of the recording system in comparison with a pinhole camera, but also has made it possible to obtain a spatial resolution of the discharge plasma no worse than the resolution of the pinhole camera. The applicability of the developed iterative method for both sources close to point ones and extended emitting objects has been demonstrated.

The article describes a method for determining the methodological error in measuring the activity of radioactive waste in containers of various types. Within the framework of the mathematical model, which takes into account the uniformity of the distribution of nuclides in the container, an assessment was made of the value of methodological error when choosing measurements using various methods using a spectrometric system with a collimated detector. The obtained results can be used in development of methods for measuring containers before sending radioactive waste for disposal to specialized organizations.

To study the spatial distribution of the soft X-ray radiation intensity of a laser-produced plasma, a new type of coded aperture was used. This aperture is a structure with a mutually perpendicular arrangement of opaque strips, the distances between which and their widths were calculated with the use of a random number generator. The radiation transmitted through such aperture gives an intricate pattern of the encoded image, which was recorded on a Fuji TR imaging plate without a protective coating. To reconstruct the spatial distribution of the plasma radiation intensity from this pattern, a mathematical algorithm was developed that is an iterative method for solving an ill-posed problem—the Fredholm integral equation of the first kind. It has been shown that the use of the coded aperture not only enhances the efficiency of the registration system by many times but also allows one to get a spatial resolution no worse than in the case of the use of a pinhole camera. It is established that the developed iterative method can be used both for sources which differ little from point sources and for spatially extended objects.

The paper presents a method for obtaining images in the study of the spatial structure of X-ray radiation of laser plasma with a new type of coded masks. In these experiments, a special type of self-supporting structure was chosen for the coded aperture. The shadow image created by the radiation passing through the aperture was recorded with a fluorescent imaging plate. An iterative algorithm based on a probabilistic approach to solving ill-posed problems was used to reconstruct the source image. The stability of the solution of the iterative method for masks of the considered type is studied, the results of applying the method for processing experimental data are presented, and the obtained images are compared with the images recorded with a pinhole camera. It has been established that the coded aperture used makes it possible to increase the sensitivity of the recording system by 2–3 orders of magnitude, while its use in combination with the developed mathematical algorithm allows one to obtain a higher spatial resolution than with a pinhole camera.

The article presents the results of a survey carried out at a storage facility for intermediate- and high-level waste established during the operation of MP and RFT research reactors at the site of the Russian Research Center Kurchatov Institute. Relevant survey methods were selected based on the personnel safety requirements for measurements, permissible individual and collective annual exposure of personnel and the population, standards for contaminated environmental objects. All RW containers held in the storage cells were certified and handled properly to ship them from the site of the RRC Kurchatov Institute. The decommissioning designs for this storage facility will be developed based on the data obtained.

Methods of determining the mass of the burned 235 U from the thermal energy released by the reactor and from indirect measurements of fission product activity are considered. A description of the Romashka nuclear reactor is given. The mass of the burned fuel is estimated. A scheme for performing measurements and an implementation of a spectrometric method for determining the mass of the burned fuel are described.

The application of thermal images for visualization of small-sized, masked sources of radioactive radiation by the heating of objects caused by them as a result of heat release during radioactive decay is considered. The acquisition of IR images of a thermal imitator of a radioactive source is simulated. Known applications of thermal imagers for remote visualization of radioactive sources are analyzed. IR images of fragments of irradiated fuel elements are presented.

A method of finding the distribution of γ-emitters with the aid of gamma-scanner, using the anti-collimator principle, is examined. The operating principle of the system, a scheme for performing measurements, and a method for reconstructing gamma-images are described. An example is given of the practical application of the developed device for finding the distribution of contamination of a pipeline on decommissioning of nuclear facilities.

The experience of using various portable gamma cameras during decommissioning and remediation of nuclear facilities at the NRC Kurchatov Institute is summarized. Typical examples of the use of cameras are given, directions for improving their functionality are proposed, prospects for the method of obtaining gamma images and possible new applications of portable gamma cameras are considered.

In the first years of its operation, the Mayak Production Association, a facility part of the Soviet nuclear weapons program in the Southern Urals, Russia, discharged large amounts of radioactively contaminated effluent into the nearby Techa River, thus exposing the people living at this river to external and internal radiations. The Techa River Cohort is a cohort intensely studied in epidemiology to investigate the correlation between low-dose radiation and health effects on humans. For the individuals in the cohort, the Techa River Dosimetry System describes the accumulated dose in human organs and tissues. In particular, organ doses from external exposure are derived from estimates of dose rate in air on the Techa River banks which were estimated from measurements and Monte Carlo modelling. Individual doses are calculated in accordance with historical records of individuals’ residence histories, observational data of typical lifestyles for different age groups, and age-dependent conversion factors from air kerma to organ dose. The work here describes an experimentally independent assessment of the key input parameter of the dosimetry system, the integral air kerma, for the former village of Metlino, upper Techa River region. The aim of this work was thus to validate the Techa River Dosimetry System for the location of Metlino in an independent approach. Dose reconstruction based on dose measurements in bricks from a church tower and Monte Carlo calculations was used to model the historic air kerma accumulated in the time from 1949 to 1956 at the shoreline of the Techa River in Metlino. Main issues are caused by a change in the landscape after the evacuation of the village in 1956. Based on measurements and published information and data, two separate models for the historic pre-evacuation geometry and for the current geometry of Metlino were created. Using both models, a value for the air kerma was reconstructed, which agrees with that obtained in the Techa River Dosimetry System within a factor of two.

A method for visualizing γ-radiation sources is described based on scanning an object of study (emergency radioactively contaminated premises or objects using atomic energy) using a gamma scanner with an anticollimator. Gamma scanner with anticollimator is designed to search for sources of γ-radiation in an inspected object in automatic mode. In contrast to the traditional scheme of a scanner with a shield and a detector collimator, the use of an anticollimator makes it possible to create a device with a mass of less than 5 kg. When using the procedure for reconstructing images of radiation sources using the maximum-likelihood method, a high angular resolution of approximately 5° is provided. A prototype of such a system and the principle of its operation are described and examples of the method for processing the measurement results are given.

A method was developed for measuring the specific activity of 90Sr in the field and a portable apparatus with the following characteristics was built: range of measurement of the activity of analytical soil samples 0.1–3000 kBq/kg and range for determining the overall activity of thin samples, for example, aerosol filters 0.05–100 kBq. A brief description of the method of radiometric measurement of 90Sr activity and its analytical verification are given, and examples of its use in the field are presented.

The work shows the ability to visualize radiotracers used in SPECT with a system based on a coded aperture mask and a hybrid pixel Timepix detector with the CdTe sensor. Characterization of the system using X-rays and radioactive sources confirms that the spatial resolution of less than 1 mm with a field of view 3 cm x 3 cm can be achieved. The results of a simulation study to determine the expected spatial resolution of the system in the focal plane for the various radionuclides is presented. The possibility of using this system with a thin (1 mm) coded aperture mask for reconstructing images of gamma emitters with the energy up to 180 keV is demonstrated.

The history and current state of CORAD method for non-destructive measurement of soil and concrete contamination characteristics by collimated spectrometric detectors with minimal assumptions about the spatial contamination distribution are considered.