Operation Of Nuclear Facilities Research Articles

Relevance of monitoring residual stresses and the need to reduce them

The objective of the study is to show the significant impact of taking into account the actual values of residual stresses on the strength and resource of safe operation of nuclear power facilities. Generally accepted approaches of strength physics and fracture mechanics were used to determine strength and service life. The degree of influence of residual stresses on the strength and service life of pipeline elements in the case of a cyclically acting load, under static load, when there is a danger of brittle fracture, and in the case of corrosion is investigated. The objects of the study were pipelines of nuclear power plants. It is noted that the current state of science and technology has made it possible to create a technique for non-destructive testing of mechanical stresses acting in metal structures based on the use of the acoustoelasticity method. Currently, on the basis of this method, a method for measuring residual welding and installation stresses in pipelines has been developed and certified for use in the field of atomic energy use. The measurement technique provides for the determination of membrane and bending stresses in annular sections located on rectilinear sections of pipelines. The values of stresses in the structural elements of pipelines and residual welding stresses in the deposited metal of welded joints are determined using ratios based on the use of the balancing principle. The relevance of introducing into the procedure for monitoring the technical condition of pipelines and equipment of nuclear power plants the procedure for determining the actual level of residual stresses, which significantly increases the reliability of the assessment of their strength and service life, is shown. It is proved that in order to implement the procedure for determining the actual level of residual stresses, it is necessary to use a non-destructive testing system for residual welding and installation stresses using the acoustoelasticity method based on a measurement technique that allows determining the actual values of residual stresses with established error characteristics.

Legal instruments for deterring nuclear conflict in the current military and political geo-environment

The relevance of this study lies in the need to consider the legal instruments for deterring a nuclear conflict in connection with the crisis of nuclear safety and instability in the current military-political geo-environment. The purpose of this study was to examine international experience in the field of legal consolidation of prohibitive norms of deterrence necessary to prevent nuclear threats. The following general scientific and special methods were employed in the study: analysis, synthesis, deduction, induction, generalisation, as well as formal legal, legal hermeneutics, logical- legal, comparative legal, and historical-legal methods. The study examined the specialised international legal framework of regulatory documents in the field of nuclear safety, safe operation of nuclear facilities and nuclear deterrence, as well as nuclear deterrence strategies and their development depending on the geopolitical situation. Based on the results of the study, it is determined that the legal regulation of nuclear conflict containment is in the form of prohibitory orders consolidated in the relevant international treaties in the field of nuclear and radiation safety. The study highlighted the main international treaties positioned as legal means of nuclear deterrence. The interaction of “soft” and “hard” law in nuclear and radiation safety agreements was considered, as well as the specific features of consolidating such norms in municipal law. The study provided generalising conclusions in terms of nuclear deterrence strategies, specifically, a vision of a new concept in this area, based on technological superiority in non-nuclear means of repelling nuclear strikes and massive precision non-nuclear retaliatory strikes. It was also concluded that attention should be paid to the development of a new international treaty that would combine all the rules prohibiting the use of nuclear energy for military purposes, as well as the rules governing nuclear and radiation safety as integral components of global nuclear security. The practical significance of this study is that its materials can be used for further development of the concepts of non-nuclear or legal nuclear deterrence

Analytical study and real simulation for improving the safety of ageing nuclear facility using UPFC

This paper aims to increase the performance and improve the safety of an ageing Nuclear Facility (NF). Good power quality extends the life of electrical equipment at NF and thus protects it from premature aging. The first stage of this paper presents a measurement and analysis of various power quality events for a real-world case of a NF under different conditions of operation. In the previous work for this group, a new proposed technique based on partial swarm optimization is presented to find the allocation of the UPFC to enhance the power quality within the specified limit. The technique is tested by IEEE33 bus. This step is to assess system performance and find the best solutions to ensure the normal and safe operation of NF. In this paper, the simulink-matlab programme was used to simulate a real NF based on a new vision of UPFC. The results indicate that the strategy is an effective way to improve the safety of power quality and ageing NF using UPFC.

Evaluation of radiation damage exposure for low alloy steel in J-9 irradiation channel of Argonauta reactor

The operation of nuclear facilities must satisfy the nuclear safety requirements. An analysis of the components of these facilities focuses on the structural materials. In this scenario, several types of alloys are employed in their construction. The nuclear fuel burn-up will result in damage caused by ionizing radiation. Due to continuous operation, radiation damage will build up and may result in the manifestation of macroscopic radiation effects. Such effects may change the mechanical, physical and chemical properties of structural alloys. Thus, it is verified the importance of the material behavior predictability to avoid reduction in performance or failure in these types of facilities. In order to study these effects, it’s necessary to calculate the displacement per atom (dpa) in the material. This calculation was estimated for the reactor Argonauta’s irradiation channel J-9 for low alloy steel. An ideal situation with a harder neutron spectrum was calculated to analyze the results. The dpa rate calculated in that facility was attributed to the low neutron energy fluence.

Justification of obtaining fine-grained structure of welded joints at high-intensity impulse effect on welding circuit

An effective method of improving the reliability of operation of thermal and nuclear power facilities is to improve the quality of manufacture, installation and repair of their thermal and generating power equipment. One of the ways to improve the quality, technological and service properties of welded joints in the process of their implementation is to influence the structure of the crystallizing metal by thermal, electric high-intensity impulse effect for its grinding. This work proposes the results of an experimental study to substantiate the production of a fine-grained structure of welded joints obtained using manual arc welding with coated electrodes at a high-intensity impulse effect (QPS) with a fi.g.= 40×103 Gts frequency, voltage Ui.g.= 80.0 V, on the welding circuit. The energy characteristics of the process can be used to assess the effect of high-intensity impulse action on the welding circuit, including the arc plasma and the structure of the resulting weld. As the energy characteristics of the welding process, the welding current Iwd, the voltage on the arc discharge Ud, the power Rp. Oscillograms of the specified characteristics were obtained, as well as the values of the maximum (peak) and average power released in the welding circuit when QPS is exposed to it and without its use were determined. Energy evaluation of input of additional high-intensity pulse effect on welding circuit as ultrasonic energy for cavitations of surface layer of welding bath at QPS was performed. Direct current arc discharge at application of high-intensity pulse effect with frequency of fi.g.= 40×103Gts (QPS) is source of cavitations of liquid phase of metal of welding bath in limited surface layer of preset thickness. It can be assumed that the crystallization of the bath takes place in layers when the welding circuit is subjected to high-intensity pulse exposure with a frequency of fi.g.= 40×103 Gts (QPS). In this case, the growing crystals break when the liquid phase oscillates due to friction forces arising between the moving liquid phase and the growing crystal. At the site of crystal fracture, zones of dynamically super cooled metal are formed, which leads to the appearance of new crystallization centers, and a fine-grained structure of the weld appears.

Electronic effects of aryl groups in modified polysilane liquid scintillator on its fluorescence-scintillation properties

Radiation detection plays a crucial role in the construction and safe operation of nuclear facilities. Liquid scintillator is widely used in this field but its fluorescence-scintillation properties still require improvement to achieve high sensitivity detection at present. In this paper, a new liquid scintillator system is developed, which selects polysilane as the matrix, and aryl with electron repulsing/withdrawing groups as the grafting substituents. The conjugated structure between the Si–Si chain and the aryl scintillating group enables electron delocalization transfer, resulting in improved fluorescence emission spectra and scintillation sensitivity. Three aryl-grafted polysilanes with typical electron repulsing and withdrawing group are successfully synthesized by Grignard routes. The optical properties of the materials are evaluated through both molecular simulation and experimental measurements, to determine the electronic effect of aryl groups on the electron delocalization in modified polysilane scintillators. The scintillation count performance is also evaluated. In conclusion, polysilanes grafted with aryl groups can be utilized as a new type of liquid scintillator, and electron repulsing substituents could enhance the fluorescence-scintillation properties more effectively, which providing meaningful guidance for the further optimization of liquid scintillation composition.

Investigation of environmental radioactivity levels and human health risk around San'ao Nuclear Power Plant (China) before operation

Baseline study on environmental radioactivity levels and public health conditions are crucial before the operation of nuclear facilities. Our goal is to establish a baseline database before the operation of San'ao Nuclear Power Plant (SNPP). To achieve this, water and food samples collection was carried out around the SNPP from 2021 to 2022 for laboratory analysis to determine the radioactivity levels. Thereafter, annual effective dose (AED) to local residents were evaluated by the analysis results and cancer incidence rates were analyzed by health data of local residents. Our results showed that the gross α and β activity concentrations in water varied within < 0.016–0.023 Bq/L and 0.031–0.080 Bq/L, respectively. The 90Sr and 137Cs activity concentrations range from 3.1 to 9.7 mBq/L and 0.11–0.42 mBqg/L in water, and range from 0.037 to 0.95 Bq/kg and 0.015–0.38 Bq/kg in food. All obtained results of gross α and β, 90Sr and 137Cs were below the thresholds of World Health Organization (WHO) and Chinese national standard. The AED induced by ingestion of food or drinking water were below the thresholds of WHO or Chinese national standard, indicating that radiation exposure was at a safe level. The incidence rate of all cancer sites combined among the residents around the SNPP was slightly higher than other regions, but still remained at the same scale. However, the incidence rate of thyroid cancer stood out to be significantly higher than the national average value in China, presumably due to excessive iodine intake in the study region.

Highly efficient removal of radioactive iodine anions by nano silver modified activated carbon fiber

Radioactive iodine anion wastewater is generated during the operation of nuclear facilities. Efficiently adsorbing and removing radioactive iodine is crucial for the sustainable development of nuclear energy. A potential adsorbent, nano silver-loaded activated carbon fiber (Ag@ACF), was prepared through hydrothermal synthesis and high-temperature vacuum reduction for the efficient removal of iodide anions. The as-prepared Ag@ACF composite has been comprehensively characterized, with silver nanoparticles uniformly distributed on the surface and pore walls of the Ag@ACF, enhancing the adsorption sites for iodine anions. The adsorption performance of Ag@ACF towards iodine anions was evaluated through column and batch experiments, varying silver concentration, adsorbent dosage, pH, contact time, and competing anions. Ag@ACF demonstrated high water stability and a low desorption rate of iodine anions. At a pH of 2, Ag@ACF exhibited a maximum adsorption capacity for iodine anions of 372 mg/g, surpassing most other adsorbents and showing promise for engineering applications. Adsorption kinetics and isotherm analysis indicated that the adsorption process of Ag@ACF primarily involved monolayer homogeneous chemisorption, resulting in the formation of stable AgI. These results suggest that Ag@ACF could serve as a potential adsorbent for removing iodine from radioactive wastewater.

Problems of safe operation of Zaporizka NPP in the conditions of war in Ukraine

Among the specified types of terrorist threats, the most dangerous today is the nuclear threat, which has moved from the realm of the probable to a real military-terrorist attack on the Zaporizhzhia NPP and its capture by the occupiers. Therefore, the issue of determining the level of nuclear and environmental safety of Ukraine's nuclear power plants in extreme war conditions, using the example of the situation that developed at the Zaporizhzhia Nuclear Power Plant (ZNPP), the largest in Europe, is extremely urgent, precisely because of the station's location in the war zone.During the period of the full-scale war, there have already been dozens of warheads hitting the objects of the critical infrastructure of the ZNPP, the external and emergency power supply of the ZNPP (transformer equipment, power supply systems to consumers, the premises of diesel generators, the industrial site of the station, and others). There have been corresponding emergency shutdowns of the power units of the ZNPP due to the blackout of the station and due to the forced disconnection of consumers as a result of the destruction of various objects in the power grid systems. These events cause great alarm and concern of the world public regarding the possibility of new global nuclear-ecological disasters due to nuclear-radiation accidents at the ZNPP. Many years of global experience in the operation of nuclear power reactor facilities (NPRF) and their safety regulation, as well as lessons from the largest nuclear and radiation accidents at NPPs, have revealed the insufficient validity of traditional probability indicators and safety criteria for NPPs, including the Zaporizhzhya plant. Probabilistic approaches to assessing the objective level of safety of the Zaporizhzhya NPP in extreme conditions of war are insufficiently substantiated, taking into account, among other things, the need to predict the possibility of the occurrence of unlikely emergency events and their combinations, which will have catastrophic consequences.Therefore, conducting an objective assessment of the level of nuclear and radiation safety at the ZNPP due to the station's location in the war zone, as well as substantiating practical recommendations for preventing nuclear and environmental disasters at the NPPs of Ukraine, is an extremely urgent issue for the entire nuclear energy industry of Ukraine.

Influence of oxygen equivalent on molten salt oxidation efficiency of mixed resin in Li2CO3-Na2CO3-K2CO3 melt

The disposal of spent radioactive ion exchange resin generated during the operation of nuclear facilities has always been a conundrum. The molten salt oxidation (MSO) for the treatment of mixed resin (MR) shows obvious superiority. In this work, ternary carbonate (Li2CO3-Na2CO3-K2CO3) and MR was used as the molten salt system and the oxidation target, respectively. The oxidation behavior of MR was analyzed by varying the temperature and oxygen equivalent during the MSO process. By studying the effect of different oxygen equivalents on the oxidation efficiency, the oxygen equivalent of 125% could make the oxidation efficiency of MR reach 99.99% at 800 °C. The composition of C, N and S containing exhaust gas produced through MSO process of MR with temperature were almost consistent with the simulation results. The exhaust gas was successfully adsorbed by molten carbonate to produce nitrate and sulfur compounds. The carbonate has good absorption to harmful gases such as SO2, CO, NO, etc. The content of SO2 from the highest 0.32% to 0, and 71.23% of sulfur in MR was trapped by molten carbonate as the form of sulfate. This work has important implications for reducing the potential harm of radioactive waste resin to the environment.

Education, training and mobility, knowledge management: towards a common effort to ensure a future workforce in Europe and abroad

Continuous and future-oriented education and training as well as knowledge management for young talents are required for the safe and reliable operation of nuclear reactors and nuclear facilities in Europe. A dedicated line of collaborative projects addresses the specific needs, such as lack of personnel (project ENEN+: “attract, retain and develop new nuclear talents beyond academic curricula”). State-of-the-art approaches and in-depth knowledge are provided when it comes to reactor physics (project GRE@T-PIONEeR: “graduate education alliance for teaching the physics and safety of nuclear reactors”) or nuclear radiochemistry (project A-CINCH: “augmented cooperation in education and training in nuclear and radiochemistry”). A highly skilled nuclear engineer must undergo experimental work to better observe theoretical principles at work. Following the ENEEP (European nuclear experimental educational platform) initiative, a network of research reactors and special laboratories is made available for performing such activities. Another issue found is that the results of Euratom-funded research activities are spread across multiple platforms and websites making it difficult to find relevant information within a reasonable timeframe. Such a situation requires the application of knowledge management actions. The PIKNUS project aims to define a concept of a knowledge management method and tool to improve the sharing and availability of Euratom research results. All projects successfully demonstrate that European collaboration could address certain needs to attract, develop and retain young talents in future-oriented nuclear fields.

New setup for measurement of prompt gammas from neutron interactions

Prompt gamma radiation from neutron interactions is an important issue as it affects the operation of nuclear facilities (radiation protection or gamma heating issues) or has various uses (non-destructive identification of elements). Despite of importance, its production is inaccurately described in present nuclear data libraries. Therefore, a set of experiments have been carried out focusing on this radiation - prompt gamma from neutron inelastic scattering on oxygen and prompt gamma from radiative capture on manganese, both present the form of an aqueous solution. The gammas were induced by the Am-Be neutron source (for oxygen) and 252Cf spontaneous fission neutron source (for manganese). In the case of oxygen, the present libraries can be used, but all the libraries tested overestimated the experiment by 20–30%, considering the experimental uncertainty of 6-9%. INDEN-4.0 library is giving the best results. In the case of manganese, none of the libraries tested give acceptable results. The INDEN updated data for gamma production on manganese give usable results, but there is still a discrepancy from -36% to 55% with uncertainties from 6-15%.

Overview of temporary radioxenon background measurement campaigns conducted for the CTBTO between 2008 and 2018

The Comprehensive Nuclear-Test-Ban Treaty (CTBT) specifies that an overall network of at least 40 International Monitoring System (IMS) stations should monitor the presence of radioxenon in the atmosphere upon its entry into force. The measurement of radioxenon concentrations in the air is one of the major techniques to detect underground nuclear explosions. It is, together with radionuclide particulate monitoring, the only component of the network able to confirm whether an event originates from a nuclear test, leaving the final proof to on-site inspection.Correct and accurate interpretation of radioxenon detections by State Signatories is a key parameter of the verification regime of the Preparatory Commission for the Comprehensive Nuclear-Test-Ban Treaty Organization (CTBTO). In this context, the discrimination between the highly variable radioxenon background generated by normal operations of nuclear facilities and CTBT-relevant events is a challenging, but critical, task. To this end, the radioxenon background that can be expected at IMS noble gas systems must be sufficiently characterized and understood. All activities conducted to study the global radioxenon background are focused on the calibration and performance of the verification system as described in the Treaty.The unique CTBTO noble gas system network is designed to optimally covering the globe. By the end of 2019, 31 systems were put in operation, 25 of which being already certified. It took two decades from the first experimental setup of noble gas system in the field to reach this stage of maturity. In the meantime, it was an urgent need to gain empirical evidence of atmospheric radioxenon concentrations with the full spectrum of characteristics that IMS noble gas systems may be observing. This experience was significantly advanced through temporary measurement campaigns. Their objective was to gain the additional necessary knowledge for a correct understanding and categorization of radioxenon detections. The site selection for these campaigns put emphasis on regions with low coverage by the initially few experimental noble gas systems at IMS locations or where potential interferences with normal background might be observed.Short-term measurements were first initiated in 2008. Sites of potential interest were identified, and campaigns up to few weeks were performed. Based on the findings of these short campaigns, transportable systems were procured by the CTBTO. Longer temporary measurement campaigns were started afterwards and operated by local hosts in different regions of the globe. Site selections were based on purely scientific criteria. Objectives of the measurement campaigns were continually reassessed, and projects were designed to meet the scientific needs for radioxenon background understanding as required for nuclear explosion monitoring.As of today, several thousands of samples have been collected and measured. Spectra of temporary measurement campaigns were (and are still) analysed in the International Data Centre (IDC). As they are not part of the CTBT monitoring system, no IDC product is generated. Analysis results are stored in a non-operational database of the CTBTO and made available, together with raw data, to authorized users of States Signatories through a Secure Web Portal (SWP) and to scientific institutions for approved research projects through a virtual Data Exploitation Centre (vDEC) after signing a cost-free confidentiality agreement (https://www.ctbto.org/specials/vdec).This paper aims at providing an overview of the temporary measurement campaigns conducted by the CTBTO since the very first field measurements. It lays out scientific results in a systematic approach. This overview demonstrates the asset of radioxenon background measurement data that have been collected with a wide variety of characteristics that may be observed at IMS stations. It bears a tremendous opportunity for development, enhancement and validation of methodologies for CTBT monitoring.In 2018, a campaign started in Japan with transportable noble gas systems in the vicinity of the IMS station RN38 in Takasaki. It will be described separately once the measurements are completed.

Development of a numerical model for sector-average plume gamma dose and its validation with dose rate measurements at Kalpakkam NPP site, India

A Gaussian Plume based simple numerical model, named DIFFUSE is developed to simulate the long-term sector-average plume gamma dose due to radioactive plume released during normal operation of nuclear facilities. DIFFUSE calculates site specific joint frequency distributions of wind speed, wind direction and atmospheric stability using micrometeorological observations. It performs the finite sector-average dose integration for any stack height and gamma energy using Simpson's 1/3rd method with sufficient computational efficiency within the site boundary up to 2 km. Plume dose contribution to the main plume sector from nearest and next nearest side plume sectors is also calculated. DIFFUSE is validated with a 3-month long, starting from February 2021 to April 2021, dose rate observation data during operational releases from 100 m stack of Madras Atomic Power Station, Kalpakkam, India. Meteorological data from onsite 50 m tower and continuous dose rate observation from two sets of Autonomous Gamma Dose Logger (AGDL) detectors, namely n-AGDLs and r-AGDLs, placed in two different configurations along the geometric arcs of wind sectors around the stack are used. Simulated doses are compared with look-up table based dose estimates by Hukkoo et al. (1988). Linear spatial averaging of cumulative AGDL doses on a sector arc is used as measured sector-average dose for model validation. Simulations performed for both n-AGDL and r-AGDL configurations show DIFFUSE estimated doses are ∼37% lower and Hukkoo estimated doses are at least ∼50% lower than the measured doses. Statistical analysis of DIFFUSE simulated doses shows a statistical correlation of R2∼98.3%, slope of the fit ∼1.36 for n-AGDL setup and R2∼75.3%, slope of the fit ∼1.57 for r-AGDL setup. Overall, DIFFUSE produces conservative doses compared to look-up table based doses as required by regulatory bodies.

Ensuring Information Disclosure and Environmental Impact on Nanoradioactive Operation of Civil Nuclear Facilities in China

Japan was struck by a massive earthquake that triggered a tsunami in March 2011, which led to a severe nuclear accident at the Fukushima Daiichi Nuclear Power Plant of the Tokyo Electric Power Company. Now, more than 10 years later, it is widely acknowledged that the civil nuclear industry is of great importance in reducing greenhouse gas emissions, improving natural environmental quality, and safeguarding national energy security. Nanomaterials and nanotechnologies, which have gained wide consideration in recent years, have shown a wide variety of application potentials in the future nuclear energy system. Thus, China has been developing its civil nuclear industry throughout the years, despite the nuclear accident in Fukushima, Japan. As a result, China is currently one of the countries with the most nuclear power plants. However, due to the potential radioactive risk, the public has an instinctive fear of civil nuclear development. To alleviate the public’s antinuclear sentiment, the Nuclear Safety Law was formally implemented in 2018, and Measures for Disclosure of Nuclear Safety Information were issued by the Ministry of Ecology and Environment of China in 2020, both stipulating that the public has the right to obtain information about nuclear safety and be involved in related activities. The purpose of such legislation is to eliminate the public’s doubts and phobia about the development of the civil nuclear industry. However, challenges still exist. Although such suggestions have been proposed, such as information disclosure and social involvement should begin as early as the siting of such nuclear facilities, mechanisms to provide sufficient compensation to the public living near nuclear facilities should be established, and these suggestions still have not been applied in the law of China and either not been practiced exactly so far. So, even though all the suggestions have strong feasibility themselves under today’s circumstances in China, it is not easy to judge the effectiveness of these suggestions until they are fully practiced. It is the biggest problem of existing works in this paper. To highlight the serious problems in information disclosure and public involvement in the siting and construction of civil nuclear facilities, several case studies were investigated as the major methodology in this research. Moreover, a legislation study was used to analyze the current content of related legislation and regulations. A qualitative methodology was also adopted to summarize the legal problems surrounding information disclosure and social involvement during the siting and construction of civil nuclear facilities. Information disclosure and public participation still face several obstacles in China, even though laws and regulations guarantee people the right to access available information and take part in pertinent decision-making. This is particularly true when it comes to the siting and construction of civil nuclear facilities. Thus, in the last several years, several antinuclear incidents have been initiated by the public due to a lack of information and mechanisms to participate. According to the examined cases, information disclosure and public involvement are still not sufficient during the siting of nuclear facilities. A relevant compensation mechanism for people living around nuclear facilities has not been established, and public education on basic nuclear safety is lacking. Therefore, public involvement cannot be completely realized. To ensure information disclosure and public involvement in civil nuclear facilities, this article proposes that information disclosure and social involvement begin as early as the siting of such facilities. Furthermore, operators of nuclear facilities and local governments should establish mechanisms to provide sufficient preventive compensation to the public living near nuclear facilities and attempt to popularize the science of nuclear safety to avoid public misunderstanding.

Adsorption Studies of Radionuclides by Turkish Minerals: A Review

Hazardous radionuclides are produced during normal operation of nuclear power plants and research facilities. They can also spread to the environment due to fallout from nuclear accidents and nuclear weapon tests. The removal of hazardous radionuclides and the safe management of radioactive waste are of vital necessity. Natural minerals have been widely used for the removal of heavy metals and radionuclides because of their low cost, high capacity and radiation resistance properties. Turkey has an abundant natural mineral deposits. These deposits include clinoptilolite, bentonite, montmorillonite, kaolinite, vermiculite, illite, red clay, sepiolite, diatomite, perlite and volcanic tuff. Within the scope of this review, Turkish minerals were classified as three main groups as; zeolites, clay minerals and other minerals. The review consists of sections on the general properties of natural minerals such as zeolites and clays, the characteristics of Turkish minerals, and the adsorption performance of these minerals against some radionuclide ions (Sr, Cs, U, Th and Po).

An Unsupervised Spectrogram Cross-Correlation Method to Assess ELM Triggering Efficiency by Pellets

The high confinement mode (H-mode) is considered the optimal regime for the production of energy through nuclear fusion for industrial purposes since it allows to increase the energy confinement time of the plasma roughly by a factor of two. Consequently, it has been selected at the moment as the standard scenario for the next generation of devices, such as ITER. However, pressure-driven edge instabilities, known as edge localized modes (ELMs), are a distinct feature of this plasma regime. Their extrapolated thermal and particle peak loads on the plasma-facing components (PFC) of the next generation of devices are expected to be so high as to damage such structures, compromising the normal operations of the reactors themselves. Consequently, the induced loads have to be controlled; this can be achieved by mitigating ELMs. A possibility then lays in increasing the ELMs frequency to lower the loads on the PFCs. As already demonstrated at JET, the pellet pacing of ELMs is considered one of the most promising techniques for such scope, and its optimization is therefore of great interest for present and future operations of nuclear fusion facilities. In this work, we suggest a method to access primary pieces of information to perform statistics, assess and characterize the pacing efficiency. The method, tested on JET data, is based on the clustering (k-means) of convoluted signals, using so-called spectrogram cross-correlation, between the measured pellets and ELMs time traces. Results have also been obtained by taking advantage of a new type of diagnostic for measuring the ELMs dynamic, based on synthetic diamond sensors, faster than the standard spectroscopic cameras used at JET.

РАСЧЁТНАЯ МОДЕЛЬ ВОЗДЕЙСТВИЯ НА ЧЕЛОВЕКА РАДИАЦИОННОГО ОБЛУЧЕНИЯ

Purpose: The aim of the work is to assess the output of stochastic and deterministic effects depending on the effective dose. Material and methods: To construct a model for estimating the probability the output of stochastic and deterministic effects depending on the effective dose of radiation, the literature experimental data were used and the probabilistic-statistical method and the least squares method were used. Results: A mathematical model is developed for estimating the yield of stochastic and deterministic effects depending on the effective radiation dose. A probabilistic mathematical model allows you to convert the risks of deterministic effects due to acute exposure of a person at a high dose and with a small exposure, measured in minutes, to the risks of stochastic effects due to exposure to a small dose during a long exposure (traced or fractionated exposure). The excellent convergence of the predicted (calculated) value EAR1 = 0,000607 and statistical EAR0 = 0.000724 is due to the fact that the reference points LD10 = 2 Gy, LD50/60 = 4 Gy, LD90 = 6 Gy are based on repeatedly verified statistical data on radiation accidents and deaths of more than 1000 people in radiation accidents. This indicates that the mathematical model adequately reflects the output of stochastic and deterministic effects observed in the operation of nuclear facilities both in normal mode and in radiation accidents. Conclusion: The probability of the yield of stochastic and deterministic effects depending on the dose of radiation received by a person is presented. The threshold of the stochastic effect for humans is in the vicinity of the equivalent dose of 10 mSv at a dose rate of 10 mSv / year for radiation with low linear energy transfer. Moreover, the probability of a stochastic effect coming out is 3×10–6 on average after 15 years.

Ispitivanje vazduha i padavina u blizini nuklearnih objekata kao deo praćenja zračenja životne sredine

Public company "Nuclear Facilities of Serbia" is the only operator of nuclear facilities and holder of licenses to perform nuclear activities in the country. By the current legislation, environmental radiation monitoring in the vicinity of nuclear facilities is performed to assess the level and control the external exposure of the population and environment to ionizing radiation due to the operation of nuclear facilities. This paper presents an overview of the representative environmental radiation monitoring results regarding radioactive contamination level and ambient gamma dose rate equivalent in air and precipitation for the year 2021. The obtained results show that there is no adverse influence on the population and environment and the radiation risk for individuals in the population is negligible.

Результати діяльності Інституту проблем безпеки атомних електростанцій НАН України у 2021 році

For the second year in a row, the Institute for Safety Problems of Nuclear Power Plants of the National Academy of Sciences of Ukraine (ISP NPP, NAS of Ukraine), as well as other scientific institutions in Ukraine and around the world, continues its work in the context of a pandemic. Additional difficulties are also caused by economic and political factors. However, despite the limitations and the need to significantly adjust the format of the tasks, the scientists of the Institute continued to make the necessary efforts to carry out planned research, implement their results and present them in publications and research activities. The main results of scientific and scientific- organizational activities of the Institute for Safety Problems of Nuclear Power Plants in 2021 are presented in the article. Despite the difficult economic situation due to the epidemic, the staff of the Institute obtained important results in studies of nuclear and radiation safety of the Shelter object, and in works aimed at improving the reliability and safety of existing Ukrainian and foreign nuclear power plants. The results of works in the field of the Shelter object transformation into an ecologically safe system, safe operation of nuclear facilities, decommissioning of nuclear facilities, spent nuclear fuel and radioactive waste management are presented in the article. These results are implemented and used in the legislative activity of Ukraine, in production, in the power industry and during the educational process.