NPP Site Research Articles

Erratum to: Statistical Evaluation of the Tritium Content of Aquatic Ecosystems at NPP Sites

Erratum to: Statistical Evaluation of the Tritium Content of Aquatic Ecosystems at NPP Sites

POSSIBLE CONSTRUCTION FEATURES OF EQUIPMENT FOR RADONOMETRY OF BOTTOM SEDIMENTS ON THE SEA SHELF DURING RESEARCH AT SHORE NPP SITES

Problem statement. Along with other natural gases that are freely discharged into the atmosphere in tectonic fault zones in Earth’s crust, the best-known one is the radioactive gas Radon (²²²Rn). The properties of this gas, namely inertness, short half-life period (up to 3.8 days) and availability of progeny distinguish it from other gases, such as methane, hydrogen, helium, etc. Another problem is determining the activity of tectonic faults identified by seismic exploration works in the waters near sites of future shore NPPs or those under construction. All the existing devices for offshore works were analyzed. Their advantages and disadvantages, as well as their suitability for radon research, have been revealed. Purpose of the article. In the paper, the need is substantiated to introduce radonometry for seismotectonic studies at shore NPP sites located in the sea and ocean shelf zones. Conclusions and results. As a result of analyzing the systems available for these purposes, it was deemed necessary to develop new types of devices different from the already existing ones and, for good measure, experimental prototypes. Moreover, there have been proposed their possible layout schemes. Layout schemes of specialized devices for radon research on the shelf, just as the need for such research, have been proposed and justified for the first time. Offshore radonometry conducted to identify the tectonic activity of revealed fault zones can become another additional factor that increases the operational reliability of future NPPs and, first of all, their hydraulic structures.

Erratum to: Statistical Evaluation of the Tritium Content of Aquatic Ecosystems at NPP Sites

Erratum to: Statistical Evaluation of the Tritium Content of Aquatic Ecosystems at NPP Sites

Factors influencing the increased 90Sr radioisotope migration in highly alkaline groundwater at Chornobyl NPP site

This paper analyses the formation of high Sr2+ concentration in strong alkaline (pH = 9.5–12.5) groundwater using data of the 27 years of observations around the destroyed Chernobyl NPP Unit 4. It appears that the formation of strong alkaline groundwater in different monitoring wells is consistent with the distribution of 90Sr, pH and main ions.The reason for the increase in 90Sr concentrations is the process of its migration from the sources of contamination - leaks of highly active water localized in certain premises inside the «Shelter » object.These computational experiments showed that for the groundwater in pH range 9.5–12.4, the concentration of strontium in the form of SrOH + increases and in the form of Sr2+ - decreases. In addition, the fraction of 90Sr in the form of a soluble neutral complex compound SrCO30, which is not sorbed, reaches 14–35%. Increased fractions of 90Sr in forms of SrOH+ and SrCO3 are factors which reduce the isotope ability to be sorbed by soils and therefore increase its migration ability. In strongly alkaline groundwater a sharp increase in 90Sr volumetric activity may also be caused by ionic strength (IS) increase above 5 mmol/L. Thus, the factors that influence the increase in 90Sr volumetric activity in strongly alkaline groundwater are the formation of its complex compounds and an increase in ionic strength (IS), which reduces the thickness of the double electric layer and, as a result, reduces the sorption capacity of soils.

Status and future prospects of nuclear industry development in Bulgaria

This paper presents a study of nuclear energy development in Bulgaria and its contribution to the country's energy sector. Current status and future prospects of the nuclear power industry have been discussed.Currently, two 1000 MW nuclear power units – Units 5 and 6 with WWER-1000 reactors are in operation at Kozloduy NPP site. Nuclear energy is one of the main pillars of the electricity producing sector with 32, 6 % of current national energy mix.Energy strategy and vision for the development of the power sector in Bulgaria envisage nuclear energy to be supported institutionally as a promising resource for generation of emission-free electricity and to ensure a sustainable energy mix. Extending the operational lifetime of the available capacities, as well as, the construction of new nuclear capacities have been considered to be of strategic importance for preserving energy security, reducing greenhouse gas emissions and reducing dependence on imports of energy resources in a cost-effective and competitive manner.In addition, this investigation is focused on the efforts that have been invested toward current nuclear reactors lifetime extension, thermal power uprate and diversification of fresh nuclear fuel supplies, as well as, construction of new nuclear capacities to ensure the future development of the nuclear industry in Bulgaria.Some key drivers and challenges in nuclear power sector for future development were analysed.Large size nuclear reactors and SMRs in Bulgarian context were considered and the outcomes indicatesthat SMRs and large reactors generation III/III+ should not be opposed but SMRs could be considered as a complementarity technology to the existing large-scale reactors.Many of the currently developed SMRs conceptual designs meet the expectations for Generation IV reactors safety level but in-depth knowledge of the specific technology is required to assess and ensure safety in accordance with the Bulgarian regulatory framework which is oriented towards light water reactors.

Statistical Evaluation of the Tritium Content of Aquatic Ecosystems at NPP Sites

Statistical Evaluation of the Tritium Content of Aquatic Ecosystems at NPP Sites

Preliminary assessment of derived concentration guideline level (DCGL) for a hypothetical contaminated site planned for Ninh Thuan 1 nuclear power plant project in Vietnam by using RESRAD-ONSITE code

RESRAD-ONSITE v7.2 code is used to assess the radiation effects on a farmer resident located in a hypothetical contaminated site planned for the first nuclear power plant project in Vietnam, namely Ninh Thuan 1, after decommissioning. Derived concentration guideline levels are preliminarily calculated for 17 radionuclides that are assumed to remain on a contaminated surface soil with an initial concentration of 1 pCi/g in the protected area of NPP site. For a reliable estimation, the site-specific conditions regarding the geological, hydrological, climate, and occupancy data gathered from the Feasibility Study Report (FSR) and relevant literatures for the Ninh Thuan 1 NPP site is employed as input parameters. The calculation results indicate that the peak of total exposure dose is estimated to be ca. 0.191 mSv/yr at the time of decommissioning, and then decrease over time. Furthermore, the protected site is assessed to be released at ca. 6.71 years after decommissioning under the regulation on radiation protection in Vietnam. Through this study, a radiation exposure model for residents living near the Ninh Thuan 1 NPP is preliminarily established by using the RESRAD-ONSITE code, which are expected to be useful for future implementation of the Ninh Thuan 1 NPP project in Vietnam.

Порівняння майданчиків розміщення АЕС методом експертного оцінювання параметричних критеріїв

The article presents a method for comparing NPP siting sites using methods of expert evaluation of parametric criteria. For a generalised assessment of sites, the following factors with corresponding criteria are proposed: economic factor: criteria — “Energy transmission networks”, “Operating costs», “Impacts on the economy»; social factor: criteria — “Transport network”, “Legal aspects”, “Impact of tourism”, “Land ownership rights”, “Historical sites”, “Public recognition”: safety factor: criteria — “Geology and seismology”, “Population density”, “Impacts on the location area”, “Cooling water”, “Meteorology”, “Hydrology”, “Topography”, “Land use”, “Proximity to wetlands”, “Evacuation routes”, “Proximity to hazardous facilities”. In this case, the expert assessment is carried out by each expert using the method of pairwise comparison of preferences, the criteria of alternatives are considered by experts comprehensively and taken into account in the pairwise comparison. This method allows for the assessment and comparison of new nuclear objects siting sites in a short time without significant financial costs. The example of the AP1000 new reactor construction project shows the process of comparing sites out of three proposed ones. The article presents an approach to comparing NPP siting sites using methods of expert evaluation of parametric criteria. At the initial stage of comparison, the proposed method is used for a generalised analysis of alternatives, without a detailed consideration and comparison of all criteria by relevant groups of factors — technical, technological, socio-economic, etc. At the same time, each expert makes an expert assessment by the method of pairwise comparison of preferences, the criteria of alternatives are considered by experts comprehensively and taken into account in the pairwise comparison. This method allows conducting a preliminary generalised comparative expert analysis and formulating recommendations for the assessment of new reactor siting sites in a short time without significant financial costs, based on numerical characteristics. Using the example of the AP1000 new reactor construction project, the paper demonstrates the comparison process based on numerical assessments of three proposed sites. The analysis shows that alternative A1, the Khmelnytskyi NPP site, is the best option.

Wind influence on the spent nuclear fuel safety in dry cask storage

This article examines the effect of wind load on the safety of spent fuel storage in a naturally ventilated building. To assess the influence of wind influences characteristic of the Akkuyu NPP site on the temperature of fuel rod cladding, a CFD model of the spent fuel storage building was developed. Reynolds-averaged governing equations of motion (RANS model) with a k-ε turbulence model were used. Computational grid included about 17 million cells. The CFD model allowed us to study different directions and intensities of wind loads, estimate the temperature around the containers and identify stagnant zones. Based on the modeling results, the dependences of the influence of wind load on the thermal fields in the building were obtained. These dependencies allowed for design decisions to be made that guaranteed safety and ensured the continuation of construction of the building.

Microbiome variability in invasive coral (Tubastraea aurea) in response to diverse environmental stressors

The Indo-Pacific native azooxanthellate Tubastraea (Scleractinia) has been identified as an invasive marine species with substantial environmental, economic, and social implications worldwide. Despite their exceptional invasive capacity, our understanding of the role of their symbiotic microbiota in host resilience, as well as their response to ambient environmental conditions, remains limited. In this study, we analyzed the symbiotic bacterial communities found in the tissue and mucus of Tubastraea aurea from different habitats along the northeastern coast of Taiwan. These habitats included two extreme sites (a hydrothermal vent [HV] and a copper mining [CM] site) and two normal environments (inlet of a nuclear power plant [NPP] and a habitat adjacent to a conservation zone [CZ]). We employed full-length 16S rRNA sequencing (~1.5 kilobases) to determine coral-associated microbiome responses to local environments. Results showed significant variations in bacterial communities between corals from extreme and normal habitats. Chemoheterotrophic Endozoicomonas bacteria dominated the tissue samples from the HV and CM sites, whereas phototrophic Synechococcus cyanobacteria dominated the NPP and CZ sites. Hydrographic parameters such as pH, salinity, biological oxygen demand, turbidity, and concentration of heavy metals (e.g., Cu and Fe) increased at the HV and CM sites compared with those at the NPP and CZ sites. This difference created more stressful conditions at the HV and CM sites. The microbial assemblages associated with T. aurea exhibited a prevalence of diverse symbiotic bacteria that could potentially contribute to the host’s ability to adapt and survive in challenging ecological conditions. Therefore, these advantageous microorganisms, along with the host’s physiological mechanisms of dispersion, range expansion, and invasiveness, may enhance the resilience and ability of T. aurea to thrive in extreme environments.

Operational Experience in Degradation (Ageing Effects) and Implementation of Ageing Management Programmes for Dry Storage Systems in Ukraine

The Coordinated Research Projects (CRPs) of International Atomic Energy Agency (IAEA) is a power tool to engage simultaneously a lot of different countries that operate Spent Fuel Storage Facilities for solving important safety issues at a deep level of competence and expertise. One of the topics that needs thorough research is behavior and state assessment of spent fuel assemblies and fuel rods during long/very long term storage in spent fuel storage facilities. It is naturally that over a long period, special attention is drawn to degradation mechanisms, ageing effects and ageing management programs that should be implemented in order to avoid and mitigate the impact of degradation mechanisms on spent fuel elements. This article describes the first step of implementing new IAEA CRP project “T13019. Performance Assessment of Storage Systems for Extended Durations (PASSED)” with contribution from the State Scientific and Technical Center for Nuclear and Radiation Safety (SSTC NRS), which conducts research regarding the “Operational experience on degradation (ageing effects) of dry storage systems” during the first stage” at the first stage. The overall objective of the research proposed by the SSTC NRS is to strengthen technical knowledge, experience and understanding of the long-term behavior of the dry spent fuel storage systems, and of the currently applied inspection and monitoring technologies. At the same time, a specific objective of involving the SSTC NRS in this project was not only to present national experience and practices, but also to study the existing experience of the participating countries, which also joined the CRP proposed by the IAEA. The article considers the existing storage systems for spent nuclear fuel at the Chornobyl and Zaporizhzhya NPP sites, provides examples of the aging management system for components and structures, as well as examples of the issues that require development, implementation and maintenance of aging management programs.

Derivation of dose constraint for the general public around nuclear power plants with operational data of radioactive effluent releases

For radiation protection optimization, ICRP proposed dose constraint as quantitative value for planned exposure situation based on representative person concept. The objective of this study is to derive dose constraints for the general public around nuclear power plants in Korea by applying representative person concept. The dose constraints for the general public around NPPs were derived through a total of six steps. The steps consisted of setting source terms, setting exposure pathways and scenarios, setting candidate groups for a critical group decision, setting habit data, calculating radiation doses, and proposing dose constraints. Through these steps, the radiation dose distribution of the general public around the NPPs was obtained, and dose constraints were proposed using the dose distribution. Radiation doses to the general public around all the Korea NPP sites ranged 1.63 × 10−2 to 1.32 × 10−1 mSv/y. Using the dose distribution, 0.15 mSv/y, 0.10 mSv/y, and 0.08 mSv/y were proposed as dose constraints. The dose constraint values derived in this study are proposals. Therefore, it is judged that the dose constraints should need furthermore discussion with regulators, licensees, and radiation protection experts considering societal and economic factors for radiation protection. The proposal for dose constraints developed in this study can be used to optimize radiation protection for the general public around the NPPs.

Analysis of site operating state contributions for multi-unit PSA with Korean NPP Sites

Analysis of site operating state contributions for multi-unit PSA with Korean NPP Sites

Comparative analysis of the results of simulation of the consequences of a serious accident at a Belarusian NPP with the use of J-RODOS and RECASSEXPRESS software complexes

Using the J-RODOS and RECASS-EXPRESS software packages, modeling of the radiological and radiation-ecological consequences of a severe beyond design basis accident at the power unit of the Belarusian NPP with a VVER-1200 reactor was carried out. The simulation results showed that if radionuclides were released from the reactor containment at the level of 2.15·1015 Bq, the maximum values of the fallout from the atmosphere to the surface 1 day after the accident will be 2.98∙105 Bq/m2 for I-131 (J-RODOS) and 7∙105 Bq/m2 (RECASS-EXPRESS), and for Cs-137 − 1.11∙104 Bq/m2 and 1.3∙105 Bq/m2, respectively. The difference in the values of the radionuclide fallout, modeled by these software packages, increases with the distance from the release source and at a distance of more than 10 km reaches 1 order of magnitude. The predicted values of the equivalent thyroid dose for adults and children for the first 7 days after the accident, obtained using J-RODOS calculations, are 3–4 times higher than using RECASS-EXPRESS software product. At a distance of 3–5 km from the NPP site, doses ranged from 3.7 to 14.8 mSv for adults and 16.2 to 32.5 mSv for children. The values of the total effective dose with the J-RODOS simulation are 2 times higher than those with RECASS-EXPRESS at a distance of 3 km from the site (0.60 and 0.32 mSv, respectively) and 1.5 times higher at a distance of 5 km from the site (0.30 and 0.21 mSv respectively). As the distance from the NPP increases, the convergence in the obtained evaluation results of total effective dose increases. None of the obtained prediction results exceeds the established emergency response criteria and do not indicate the need for protective measures for the public.

Обзор зарубежного опыта и результаты испытаний материалов на основе цемента для обеспечения долговременной безопасности хранилищ радиоактивных отходов

In-depth analysis of proposed materials should always precede the construction of purpose designed facilities. These studies primarily demonstrating their feasibility, performance, service life, when applied in aggressive environments, are basically seeking to validate the timeframes of their safe operation. This article analyses the studies that have been implemented at the Canadian Nuclear Research Center (Chalk River Laboratories), at a radioactive waste storage facility at the Dukovany NPP site in the Czech Republic, at the El Cabril radioactive waste storage facility (E1 Carbil facility) in Spain, as well as the results obtained within the framework of the international CRP project.

Radiological Impact Assessment for hypothetical accident scenarios of a proposed pressurized water reactor using HotSpot code

The radiological risks following two severe hypothetical accidents at a proposed pressurized water reactor (PWR) in Umm Huwayd in the Eastern Coast of Saudi Arabia, have been determined using the health physics code HotSpot 3.1.2, developed by Lawrence Livermore National Laboratory, USA. In this paper the general plume dispersion code was used, the Total Effective Dose Equivalent (TEDE) were estimated and the direction of propagation was included the two accident scenarios for various stability classes A, B, C, D, E and F. At a closer distance to the release point the TEDE peaked faster for class A in both accident scenarios. The maximum TEDE values received by the NPP site workers, member of public and the permanent resident were estimated for both accident scenarios at a distance of 0.12 km, 4 km and 80 km from the released source point, respectively. For the two accident scenarios at two distances (0.10 km and 80 km) from the release point, the TEDE values were evaluated for different pathways (inhalation, submersion, ground shine and resuspension). The outcomes showed that for both scenarios, at 0,10 km, the submersion pathway is the dominant intake followed by inhalation and at 80 km distance, the most dominant pathway was found to be (inhalation) followed by (submersion). The effective release height of 10 m, 20, 30 m and 40 m was simulated and found to have inverse relation with TEDE and the ground deposition. Inversion layer height also was evaluated.

An Analysis of Water Characteristics of Shiddhirganj 210MW Steam Power Plant, Sirajganj 225MW Combined Cycle Power Plants and Rooppur 2400MW Nuclear Power Plant in Bangladesh: A Comparative Study of Power Plant Grade Water

Water quality has long been an important part of the operation of nuclear and thermal power plants. Water is used as a working and cooling fluid in power plants. The quality of source water to be used in the power plants after treatment should conform to the prescribed values of Physico-Chemical properties like pH, EC, TDS, Alkalinity, Hardness, presence of Chloride content, Silica, and Heavy metals as recommended by technical guidelines. To analyze the water characteristics, water samples were collected from various sources. Two river water samples and a groundwater sample (marked as PP1, PP2, and NPP site) were tested to determine the water properties. The Physico-chemical properties of the water samples were determined using various analytical tests. Heavy metals were also investigated using the Atomic Absorption Spectrophotometric (AAS) process. The Physico-chemical properties of investigated samples were so good as to the recommended values of the World Health Organization (WHO), United States of Public Health (USPH), and Bangladesh Environmental Department. But the values were very far from the recommended values for thermal power plants operation. So, it needs to treat to use in the boilers. Gravitation, Carbon filtration, Ion exchange method, and Reverse Osmosis (RO) are good ways to treat the water before use in power plants. The Padma River water is better than the other two samples when the Physico-chemical characteristics of the sample waters were analyzed to the prescribed levels for the boiler water of a thermal power plant and the secondary water circuit of a third-generation nuclear PWR reactor. The aim of this work is to explore the difference between the source water quality parameters values and those of the recommended values of technical guidelines. To minimize the water treatment cost, a new site for the installation of a power plant project in Bangladesh can be advocated depending on the availability of good quality water.

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.

SPECIAL RESEARCHES OF CLAY SOILS WHICH ARE NOT REGULATED ON NPP SITES

Problem statement. The article presents the results of special non-normative research for saline clay soils sampled from excavations during the nuclear power plants’ construction at different times and in different countries. Of the NPP sites located in the arid climate zone, only the Crimean NPP, which is not yet under construction, the planned NPP in Uzbekistan and possibly the NPP in Egypt are close to the engineering and geological conditions relative to the described NPP site to a large extent. The purpose of the article. The researches’ purpose is to estimate the degree of leakages impact from technological pipelines for production water of different composition and temperature, which affect the soil properties of the foundations for responsible buildings and structures of NPPs and other critical energy facilities. The need for such research is obvious to ensure the safe operation of nuclear power plants, especially when NPP are located in difficult seismotectonic and geological conditions. Conclusions. The non-regulated method for investigating the plastic properties of clay soils proposed in this article is a combination of several already tested research methods. The essence and difference of this indirect method is to investigate the soils plastic properties only after their pretreatment at different times with ground water of different temperatures. The test process partially simulates the impact on soil bases of possible short-term (instantaneous) or long-term leakages from technological thermal water supply communications, which would result in significant ground water warming. As a work result, the upper horizons of the soils for some NPP sites were prone to soaking, including at elevated temperatures, but no fundamental differences from these impacts have yet been found. The results of these researches correlate quite well with the previously performed investigations on soils leaching in the upper part of the geological section of the NPP sites. As a result, the upper soil horizons of some NPP sites were prone to soaking, including at elevated temperatures, but no fundamental differences from these effects have yet been identified. The results of the conducted research correlate quite well with the previously performed studies on soil leaching in the upper part of the NPP sites geological section.

Coupling of ASTEC V2.1 and RASCAL 4.3 Codes to Evaluate the Source Term and the Radiological Consequences of a Loss-of-Cooling Accident at a Spent Fuel Pool

Abstract This paper deals with a general methodology to evaluate the Source Term (ST) and the Radiological Consequences (RC) of a hypothetical Severe Accident (SA) at a Fukushima-like Spent Fuel Pool (SFP) by coupling ASTEC 2.1 and RASCAL 4.3 SA and consequence projections (CP) codes, respectively. The methodology consists of the following sequential steps: the ST provided by a prior simulation performed by ASTEC V2.1 code was used as input to RASCAL 4.3 code to make a RC analysis. This approach was developed as a preparatory study for the Management and Uncertainties in Severe Accident (MUSA) H2020 European Project, coordinated by CIEMAT, where the ENEA's Nuclear Installations safety laboratory is committed to performing an analysis on a Fukushima-like SFP with the aim to apply innovative management of SFP accidents (WP6) to mitigate the RC of the accident itself. To perform the RC studies that could have an impact on Italy, a Fukushima-like SFP was assumed located in one of the Italian cross-border NPP sites. The weather data adopted are both standard and real hourly meteorological data taken from more than one geographical location. The results of the RC for 96 h of ST release in a range of 160 km from the emission point are reported in terms of Total Effective Dose Equivalent (TEDE), Thyroid dose, and Cs-137 total ground deposition. The mitigating effect on ST and on RC of the cooling spray system (CSS) actuated with several pH values (i.e., 4,7,10) was also investigated.