Nuclear Fuel Cycle Facilities Research Articles

Artificial radionuclides in the plant cover around nuclear fuel cycle facilities.

This paper presents research on the assessment of the radioecological state of plant cover surrounding two research reactor facilities located within the Semipalatinsk Test Site (STS) as examples of nuclear fuel cycle facilities (NFC). Source data on the concentrations of artificial radionuclides in the plant cover were obtained. Quantitative values for 137Cs, 241Am, and 239+240Pu activity concentrations were determined in plants across the perimeters of the facilities, indicating that these compounds may be present in the associated media from the perspective of accumulative bioindication. The values determined for artificial radionuclides in the 'soil‒plant' system around the researched NFC facilities were attributed to radioactive contamination of the STS territory.

Study on radiological environmental impact assessment of nuclear fuel cycle facilities

The radiological assessment model REIA 1.0 is established to assess the radio-logical environmental impact of radioactive airborne effluents released from nuclear fuel cycle facilities. It is based on the double Gaussian probability distribution function model and considers the wind pendulum effect of the long-term diffusion factor. The simulation results of the REIA 1.0 model are compared with those of the AERMOD-VIEW model and radiation environmental monitoring results of nuclear fuel cycle facilities. The results are: using the REIA 1.0 and AERMOD-VIEW models, the relative deviations of simulation results are less than 33.33% in 192 subregions. Except for three points, the relative deviations are less than 20%, the simulated results are consistent with the radiation environmental monitoring results in seven sites using the REIA 1.0 model, and the REIA 1.0 model can characterize the incremental contribution of radionuclide concentration in the air caused by the radioactive airborne effluents from nuclear fuel cycle facilities. It can effectively assess the radiological environmental impact of nuclear fuel cycle facilities.

Simple and Complex Substrates (Sugar, Acetate and Milk Whey) for In Situ Bioremediation of Groundwater with Nitrate and Actinide Contamination

The complex contamination of groundwater near radioactive waste repositories by nitrates and actinides is a common problem for many nuclear fuel cycle facilities. One of the effective methods to remove nitrates and reduce actinide migration activity is bioremediation through the activation of native microbial communities by soluble electron donors and carbon sources. This work evaluated the effectiveness of using simple and complex electron donors to remove nitrate in the microbial community in an aquifer near the B2 storage of the Siberian Chemical Combine (Seversk, Siberia). The addition of sugar and milk whey led to the maximum efficiency of nitrate-ion removal and a decrease in the redox potential of the system, creating optimal conditions for the immobilization of actinide. Special attention was paid to the behavior of uranium, plutonium, neptunium, and americium under conditions simulating groundwater when sugar, acetate, and milk whey were added and when microbial metabolic products were formed. Neither microbial metabolites nor organic solutions were found to have a significant effect on the leaching of neptunium. At the same time, for plutonium, a decrease in yield was observed when rocks were treated with organic solutions were compared to groundwater treatment without them. Plutonium leaching is significantly affected by rock composition. In rocks with a low clay fraction content, its yield can reach 40%. At the same time, microbial metabolites can increase americium (Am) desorption from rocks with a low clay fraction content. Additionally, particle size analysis was performed using a step-by-step filtration approach, aiming to evaluate the risks that are associated with colloidal phase formation. It was shown that microbiological stimulation resulted in particle enlargement, substantially diminishing the presence of actinides in the form of dissolved or sub-50 nm nanoparticles. This outcome significantly reduced the potential for colloidal and pseudocolloidal transfer, thereby lowering associated risks.

Experimental Study on Aerosol and Gas Emission of Solvent Fire Accident in Nuclear Fuel Cycle Facility

In the nuclear fuel cycle, 30 vol % tributyl phosphate/kerosene is always used as the major actinide extractant. However, there is a risk of fire accident during the usage of the solvent solution. It is necessary to investigate solvent fire because of the release of radioactive materials and possible overheating and blocking of ventilation filters. This paper discusses several tests of solvent solution combustion that were carried out to analyze the safety of solvent fire. Parameters such as gas emission of solvent burning, mass loss rate, and production of aerosol were obtained and analyzed. The experimental data obtained in this paper can be useful to develop a method of solvent fire assessment and evaluate a solvent fire accident in a nuclear fuel cycle facility.

Накопление Cs–137 и Sr–90 культурой салата на почвах основных радиоактивно-загрязненных участков бывшего Семипалатинского испытательного полигона

Under conditions of a simulated pot experiment in the case of salad (Lactuca sativa), quantitative parameters of Cs-137 and Sr-90 (Tf) accumulation by plants on soils from the former Semipalatinsk Test Site territory were obtained. The variation range of Tf values derived for soil samples from different STS areas was 2 orders of magnitude for Cs-137 and 1 order of magnitude for Sr-90. Using nonparametric statistical analytical techniques, determinants of the transfer of Cs-137 and Sr-90from soil to plants for STS soils with various natures of radioactive contamination were identified. The content of biologically available species of radionuclides has a significant effect on the accumulation of Cs-137 and Sr-90by salad. Values derived for Kendall correlation coefficients showed a complete functional dependence (r=1, n=4, p<0,05) between accumulation parameters and the content of biologically available species of Cs-137 and Sr-90in soil from radioactively contaminated test site areas. The use of partial correlation coefficients allowed identification of key soil contributors to the content of available speciation and, respectively, the accumulation of Cs-137 and Sr-90by the experimental crop: for 137Cs, the common content of K (rxy-z = -0,81); for Sr-90 — the common content of Ca (r xy-z = — 0,64). Findings reveal the main mechanisms of Cs-137 and Sr-90transfer from soil to plants, which are of great practical importance in the radio ecological monitoring and planning of rehabilitation measures taken in radioactively contaminated STS areas as well as in areas impacted by nuclear fuel cycle facilities (NFC) located under similar soil and climatic conditions.

Investigation of the Transfer Rate of Radioactive Materials in a Hydrogen Explosion Accident at a Reprocessing Plant

As an explosion of radiolitically generated hydrogen is listed as a type of severe accident in the new regulation for nuclear fuel cycle facilities, it is important to evaluate the realistic source term of this type of accident. The airborne release fraction (ARF) is a key parameter in evaluating the source term of a hydrogen explosion. Therefore, a pressurization experiment and a hydrogen explosion experiment that induced a hydrogen explosion have been performed. As a result, the ARFs obtained from the pressurization experiment and hydrogen explosion experiment were approximately 1 × 10−5 and 1 × 10−6, respectively. There was no marked difference in the pressure dependency and liquid droplet particle size between the pressurization and hydrogen explosion experiments.

IMPLEMENTATION OF IAEA SAFEGUARDS IN A STATE WITH AN IMPORTED FAST REACTOR AND A CLOSED NUCLEAR FUEL CYCLE

The implementation of the IAEA safeguards in the non-nuclear weapon state party to the NPT (Non-Proliferation Treaty) that has imported the fast-neutron reactor with nuclear fuel cycle facilities is considered. The features of fast reactors that should be taken into account when preparing them for export together with CNFC technologies considering the implementation of IAEA safeguards in the importing state, are noted. These include high mass fraction of plutonium in fresh fuel loads and handling of a large amounts of fissile materials in the technological cycles of reprocessing spent nuclear fuel. It is concluded that it is possible to implement the effective IAEA safeguards in the state importing such reactor and nuclear fuel cycle facilities considering their physical and design features and innovative technologies, including those used in the IAEA safeguards implementation.

Export prospects of fast reactors desined in Russia with closed nuclear fuel cycle facilities

The inevitability of switching to carbon-free energy to withstand the climate change is no longer disputed by anyone today. There is no alternative to this, and the scientific community is forming an appropriate understanding of the need for the development of nuclear energy as carbon free energy source. Solutions are already being discussed at the level of the President and the Government of Russia. In this regard, the article shows that such a solution is possible only based on a new technological platform – two-component nuclear power with the development of technologies of fast reactors with a closed fuel cycle. At the same time the prevailing view in the public opinion of Russia, and not only in it, is that climate change problem can be solved only at the expense of solar and wind energy. This attitude needs to be changed, because without the understanding and support of society, it is impossible to achieve a wide spread of fast reactors with closed fuel cycle technologies. It is concluded that in order to promote a new technological platform in commercial energy and ensure the export prospects of fast reactors of Russian design with closed nuclear fuel cycle facilities, it is necessary to attract representatives of business circles and large energy businesses to the number of supporters of such development by demonstrating the profitability of solutions in the medium and long term, implemented in the case of the use of Russian technologies of fast reactors with the closure of the nuclear fuel cycle.

Current state of development of industrial power complexes with fast neutron reactors

The report provides the description of the main demands, approaches and results of the design of the industrial energy complex (IPC) with fast nuclear reactors. A conceptual design (‘outline design’) of the IPC has been developed, which combines industrial reactor units with power output of 1200 MW and closed nuclear fuel cycle facilities. The main solutions and technical and economic indicators are defined. To get higher results with minimum resource spend, we implemented the way of consideration of different solutions, extensive use of digital technologies in designing, applying better solutions well-known both in the nuclear and other industries. The issue of the influence of preferred type of nuclear reactor on IPC design solutions was discussed. The perspective ways of further developments were defined.

Monitoring of atmospheric emission of alpha emitters radionuclides at a nuclear fuel cycle facility in RJ, Brazil

The Indústrias Nucleares do Brasil S/A (INB) in Resende, state of Rio de Janeiro, operate with open sources containing alpha emitters. This operation produces particulate material in the air. To reduce this impact, the plant operates with negative pressure using an exhaust equipment. Exhaust air is sent to an absolute filter system. In the exhaust stack, there is an alpha emitter detection module that operates monitoring the releases. Following the dose calculation model established by the National Commission for Nuclear Energy (CNEN), the authorized limit is fixed at 1.2∙107 Bq.y-1 of alpha emitters by Nuclear Fuel Factory (FCN). The present work aims to evaluate the alpha-emitting radionuclides released by FCN in terms of total release (Bq) and activity concentration (AC, Bq∙m-3). In 2018, FCN released 1.41∙106 Bq.y-1(i.e. 34% of the 2016 releases). The largest mean for AC was 2.04 mBq∙m-3. The release data was almost an order of magnitude lower than the annual release limit, proving the adequation of the atmospheric effluents to the licensing requirements.

Development and Studies on FBG Temperature Sensor for Applications in Nuclear Fuel Cycle Facilities

This paper presents the novel results on fiber Bragg grating temperature sensor deployment in high radiation and hazardous chemical environment of nuclear fuel recycle facility. The sensor is developed using thermally regenerated grating obtained from the thermal annealing of seed type-I grating inscribed in telecommunication fiber. The studies on the operating life time and average sensitivity of regenerated grating were carried out upto 900 °C. For the remaining reflectivity of $\sim 5$ % at 900 °C, the predicted lifetime of the grating was around 4 year. The radiation hardness of the packaged FBG sensor was tested in high radiation environment upto 1 MGy. Bragg wavelength shift of $\sim 35$ pm was observed after 1 MGy accumulated gamma radiation dose. Developed and characterized FBG sensor was finally deployed for temperature monitoring of nuclear fuel recycling chamber. Reliable and accurate temperature measurement helped to precisely control the process and to avoid the spill over of uranium, plutonium nitrate solution in the microwave heated process chamber.

Model design of a deuterium-deuterium neutron generator moderator and evaluation for delayed gamma-ray nondestructive assay for safeguards verification

ABSTRACT The Japan Atomic Energy Agency is evaluating delayed gamma-ray spectroscopy as an active interrogation nondestructive assay technique to quantify the fissile composition of nuclear materials for improved safeguards verification in nuclear fuel cycle facilities. In this paper, we optimize a moderator to thermalize the 2.5 MeV neutrons emitted from a deuterium–deuterium (D–D) neutron generator. The moderator is optimized to maximize the thermal neutron flux, maintain a high moderator quality factor, and be compact for easy installation in the analytical laboratories of reprocessing facilities. With the objective of applying our system to high-radioactivity nuclear materials (e.g. spent fuel solution), we applied this moderator’s flux to an interrogation using delayed gamma-ray spectroscopy for various sample sizes and timing patterns. The results indicate that our 78-cm3 system is sufficiently able to use commercially available D–D neutron generators with neutron emission rates less than 109 n/s for 25- and 100-ml solutions under specific interrogations.

Active Neutron Monitoring of Nuclear Fuel Cycle Fissile Materials

A decommissioning of nuclear fuel cycle facilities is inseparable from the problems of radioactive waste disposal. One of these problems is the categorization of a waste according to the content of beta- and alpha-emitters. Beta-emitters can be identified by existing technologies; however, the trouble arises when detecting alpha-emitting elements, primarily the long-lived members of the actinium chain with the specific activity of kBq/kg when they are spread inside a structural material. The report considers an application of an active neutron method-a differential die-away technology for reliable control of small quantities of FM. The essence of this method consists in sounding the interrogated item by pulsed thermal neutrons and recording the induced fission neutrons. The ratio of the number of fission neutrons to the number of source neutrons gives the normalized number of fission neutrons that is linked to the FM mass in the interrogated object. The work presents the scheme and principle of operation of an experimental device, as well as the results of measurement of concrete structures that contain internal traces of fissile materials. Analysis of the results shows that the proposed method allows the detection of ~ 6 mg of fissile material per kg of concrete with possible localization (cartogram) of the contaminated area.

Heralds of global transparency: Remote sensing, nuclear fuel-cycle facilities, and the modularity of imagination.

How has commercial remote sensing influenced the framing of public narratives about nuclear programs and weapons of mass destruction? This article examines an early and formative case: In 2002, a Washington-based nongovernmental organization used commercial satellite images to publicly identify the Natanz nuclear facility in Iran. The episode helped inaugurate the 'Iran nuclear crisis' as we have known it since. But it also played a role in fomenting a commercial market for remote sensing, adjusting the role of 'citizen scientist' in the nuclear arms-control community, visualizing a new television journalism beat of 'covering the intelligence community', legitimizing a transforming role of nuclear safeguards inspectors at the International Atomic Energy Agency, and solidifying Iran's nuclear program as 'clandestine'. This article follows the images as they pass through these social worlds and examines how heterogenous actors incorporated remote sensing into their identities and commitments to global transparency.

Prospects of creation of the two-component nuclear energy system

Possible options of organization of two-component energy system with closed nuclear fuel cycle (CNFC) and new business potential associated with provision of CFC services to foreign customers are examined. Dominating role in the development of nuclear power generation is assigned to VVER reactors with gradually increasing fraction of sodium-cooled fast breeder reactors (FR) incorporated within the joint nuclear fuel cycle operated on MOX-fuel. Components of such energy system perform the following functions: 1. Fast reactors: Generate electric power in base-load mode (possibility of fine tuning of reactor power within limited range (100 – 75 – 100%) is assumed); Utilize waste and/or regenerated uranium for re-fueling power reactors, produce plutonium applicable to the maximum extent for manufacturing MOX-fuel for VVER reactors; Incinerate long-lived highly radioactive wastes – minor actinides separated during reprocessing spent nuclear fuel of FR and VVER reactors. 2. VVER reactors: Generate electricity in compliance with manoeuvrability requirements imposed by the utility company operating the energy system; Utilize MOX-fuel instead of UO2 fuel; Are offered for export with the option of returning SNF back to Russia; Plutonium extracted from VVER spent fuel is used for manufacturing MOX-fuel for SFR. 3. Nuclear fuel cycle facilities: Provide reprocessing of SNF from VVER and SFR with extraction of nuclear materials for recycling; Use depleted or reprocessed uranium and plutonium extracted from spent nuclear fuel for manufacturing MOX-fuel; Provide partitioning of RAW for subsequent utilization of minor actinides and reduction of risks of proliferation of nuclear materials, conditioning and disposal of RAW. Russia possesses capacities for establishing the two-component system with CNFC, as well as the new business approach to rendering CNFC services to foreign customers.

Assessment of thermal neutron scattering in a heavy paraffinic molecular material

Base oil lubricants are prevalent in many mechanical systems and can have a wide range of chemical compositions. Their carbon numbers generally span from C20–40, and they are often classified by their predominant molecular species (e.g., paraffinic, naphthenic). These heavy, viscous fluids are of interest when used in or around nuclear fuel cycle facilities, where they may influence the local neutronic environment. Furthermore, variations in molecular structure impact the oil’s dynamic properties and render the modeling process a challenging endeavor. In this work, a model for a specific paraffinic oil was developed for obtaining the vibrational/translational density of states (DOS) for hydrogen and carbon, the primary and secondary scattering species, respectively. The DOS was subsequently used to generate the thermal scattering law (TSL). The molecular ensemble, constructed using the MedeA material design platform, was benchmarked using available static and dynamic properties (i.e., density, viscosity, viscosity index, diffusivity). All simulations were performed using the LAMMPS code, and the COMPASS force field, a semi-empirical molecular potential, was selected as a suitable representation of the system dynamics. Additionally, a modified version of the nuclear data processing code, NJOY, was employed to more accurately treat a viscous fluid. Through this investigation, the viscous behavior characteristic of a heavy paraffinic oil was captured and was found to minimally impact the TSL when compared to the solid approximation.

SYSTEM APPROACH TO GEODYNAMIC ZONING BASED ON ARTIFICIAL NEURAL NETWORKS

In this research are presented methodological aspects of the using of artificial neural networks for the tasks of geodynamic zoning of territories are considered when choosing locations for environmentally hazardous objects (using the example of nuclear fuel cycle facilities). To overcome the uncertainty caused by the complexity of analyzing information about the properties, processes and structure of the geological environment, a systematic information analysis approach is used. The geological environment is represented as a system of interacting anthropogenic object and environment, between which connections are organized. In assessing the safety of operation of this type of system, it is important to monitor indicators of the state of the environment. According to modern regulatory requirements of international and domestic organizations, one of the main, and at the same time, difficult to determine indicators of the state of sites for the nuclear fuel cycle facilities are modern movements of the earth's crust. In this paper, we outlined a method for predicting modern movements of the earth's crust based on artificial neural networks. On the basis of the predicted kinematic characteristics of the earth's crust, it is possible to identify dangerous zones by the manifestation of geodynamic processes: zones of tension, compression, zones of accumulation of elastic energy, and so on. Preliminary results obtained on the presented neural network architecture have shown a positive outlook for the application of this methodology for geodynamic zoning tasks.

Elaboration of approach to nuclear energy systems assessment by criterion of sustainable development

The paper describes the approach to the assessment of nuclear energy systems based on the integral indicator characterizing the level of their sustainability and results of comparative assessment of several nuclear energy system options incorporating different combinations of nuclear reactors and nuclear fuel cycle facilities. The nuclear energy systems are characterized by achievement of certain key events pertaining to the following six subject areas: economic performance, safety, availability of resources, waste handling, non-proliferation and public support. Achievement of certain key events is examined within the time interval until 2100, while the key events per se are assessed according to their contribution in the achievement of sustainable development goals. It was demonstrated that nuclear energy systems based on the once-through nuclear fuel cycle with thermal reactors and uranium oxide fuel do not score high according to the integral sustainable development indicator even in the case when the issue of isolation of spent nuclear fuel in geological formation is resolved. Gradual replacement of part of thermal reactors with fast reactors and closing the nuclear fuel cycle results in the achievement of evaluated characteristics in many subject areas, which are close to maximum requirements of sustainable development, and in the significant enhancement of the sustainability indicator.

Development of Gadolinium (neutron poison) monitoring system for fuel reprocessing facilities: Computational model and validation with experiments

Gadolinium, a strong neutron absorber is a good choice of material for use as soluble neutron poison for nuclear criticality control in nuclear fuel cycle facilities. During operation, it's availability has to be ensured in order to maintain the sub-critical state of the system. Towards this, periodic monitoring of presence of Gadolinium, a monitoring system was developed. The technique used is based on thermal neutron attenuation characteristics of the medium considered under study. As the design involves, choice of neutron source, moderator assembly and neutron detector sensitivity, Monte Carlo simulation was employed to optimize the design parameters. The details of simulation and experiments carried out to study the feasibility of the method is described. Results of measurements and comparison with computational model developed are also presented in detail. The results indicate that the proposed system can be successfully deployed for remote online monitoring of neutron poison in Fuel Reprocessing.

Assessment of Ventilation and Air Cleaning System Design Approaches for Nuclear Safety Requirement during Accidental Conditions in Nuclear Fuel Cycle Facilities

Assessment of Ventilation and Air Cleaning System Design Approaches for Nuclear Safety Requirement during Accidental Conditions in Nuclear Fuel Cycle Facilities