Fukushima-1 NPP Research Articles

Assessment of Pollution of the Waters in the South Kuril Fishing Zone of Russia by Radioactive Waters from the Fukushima-1 NPP Based on Lagrangian Modeling

The study investigates the potential hazard arising from the actions taken by the Japanese government regarding the discharge of technical radioactive water from the Fukushima-1 nuclear power plant storage facilities. The contamination of the South Kuril Fishing Zone (SKFZ), which is one of the most promising fishing areas for the Russian Federation, with radioactive particles, is considered. Based on the modeling of passive markers simulating radioactive contamination, the study analyzes the pathways and mechanisms of pollution transfer into the SKFZ. The research is conducted using altimetric data on geostrophic currents for the period from August 24, 2022, to August 24, 2023. The pollution transfer into the SKFZ is determined by a set of conditions related to the current development regime of the First Kuril Meander and the local vortex system with varying characteristics, both near the discharge site and at the SKFZ border. A seasonal dependence of the speed and quantity of polluted water infiltration toward the Russian Federation’s shores is established. The possibility of rapid pollution advection into the SKFZ within 13 days has been discovered. This speed is due to the entrainment of contamination by the Kuril Meander and its further transport by the mesoscale vortex system to the SKFZ border. The study reveals periodicity in the influx of pollution into the SKFZ. Graphs depicting the distribution of the quantity of “dirty” markers over their release times and the arrival of polluted water at the SKFZ border have been created.

Assessment of Pollution of the Waters in the South Kuril Fishing Zone of Russia by Radioactive Waters from the Fukushima-1 NPP Based on Lagrangian Modeling

Assessment of Pollution of the Waters in the South Kuril Fishing Zone of Russia by Radioactive Waters from the Fukushima-1 NPP Based on Lagrangian Modeling

Ensemble of Below-Cloud Scavenging Models for Assessing the Uncertainty Characteristics in Wet Raindrop Deposition Modeling

This work is devoted to the development of an ensemble of below-cloud scavenging models of pollutant aerosol transport into the atmosphere. Among other factors contributing to the uncertainty of the forecasts of the dispersion and deposition of technogenic gas-aerosol releases in the atmosphere, precipitation scavenging is one of the least studied and, in case of precipitation, can be the dominant mechanism for aerosol deposition. To form the ensemble of below-cloud scavenging models, appropriate experimental data, raindrop-aerosol capture models, raindrop terminal velocity parameterizations, and raindrop size distributions were chosen. The pool of models was prepared and then evaluated to adequately describe the experimental data using statistical analysis. Rank diagrams were used to analyze the adequacy of meteorological ensembles; together with the ensemble distribution construction, they allowed selecting the groups of models with such properties as to produce unbiased estimates and dispersion corresponding to the dispersion of the experimental data. The model calculations of the concentration fraction deposited due to below-cloud scavenging were performed using a log-normal distribution with characteristics corresponding to those observed during the accidents at the Chernobyl NPP and Fukushima-1 NPP. The results were compared with those obtained using the models of the NAME and FLEXPART codes. The results of this work can be used to improve the current approaches applied for modelling the distribution of pollutants in the atmosphere in the case of emergency, enhancing the reliability of forecasts by taking into account uncertainties in the results. The formed multi-model ensemble will be included in the decision support system used in responding to releases of radioactive substances into the atmosphere.

Забортный теплообменник система пассивного отвода тепла от реакторной установки

After the accident at the Fukushima-1 NPP, the requirements for the safety of reactor facilities became more stringent, which led to the improvement of safety systems due to the transition from active principles of operation to safety systems with passive principles. An example of such a system is a passive heat removal system (hereinafter PHRS), which should transfer heat from the core of a nuclear steam generating unit to the final absorbers (sea water and/or atmospheric air) during normal and emergency cooling down, as well as when operating at low power static modes. without the participation of a steam turbine unit. Moreover, the process of heat removal should be carried out without using additional energy sources. This means that the PHRS must convert part of the removed heat energy into work on moving the coolant in it. Without the cost of electricity, this process can be carried out using natural circulation (EC) and/or steam-water jet devices (PVSA).

Dosimetry of external population exposure: a comparison of the Chernobyl and Fukushima accidents

The paper is devoted to comparing the models and the doses of the population external exposure from radioactive fallout after the accident at the Chernobyl and Fukushima-1 NPPs estimated with their help. In the case of the Fukushima-1 accident, the model proposed by the UNSCEAR was used. Both the values of the doses of gamma radiation in the environment and the values of the effective doses of external exposure of comparable population groups normalized to the same surface activity of radionuclides were close for both accidents. The reasons for this are both the similarity of the isotopic compositions of the radioactive fallout and the fact that the “Japanese” model of external exposure was based on the “Chernobyl” model up to using the same numerical values for some parameters, due to the lack of specific Japanese post-accident data for the moment of the first dose estimates for the inhabitants of Japan. For a more accurate comparison of the external exposure of residents after two accidents it is necessary to verify the values of the parameters of the Japanese model using the results of measurements of gamma radiation dose rates in the environment and individual external doses of the residents after the accident at the Fukushima-1 NPP.

Results of the fourth combined scientific expedition for the radition monitoring in the Kurily-Kamchatka region of the Pacific ocean

This paper continues the series of publications on evaluation of the consequences of the Fukushima-1 nuclear power plant accident and the impact of the emergency radionuclide discharges on the contamination of the sea biota and coastal areas of the Far-East regions. In autumn 2019, the fourth scientific expedition of the Russian geographic society on the monitoring of the radiation situation in Kurily-Kamchatka region was performed on the training vessel «Professor Khlyustin». The expedition included 9 specialists from noncommercial organization «Polar research Fund «Polar Fund», «Russian state hydrometeorological institute», «Radium institute after V.G. Khlopin» of the State Corporation «Rosatom», «Kurchatov institute», «SaintPetersburg research institute of radiation hygiene after prof. P.V. Ramzaev» and «Marine state university after admiral G.I. Nevelsky». The aim of the fourth expedition was to evaluate the radiation situation in the Sea of Japan and Kurily-Kamchatka region after the Fukushima-1 NPP accident as a continuation of the similar marine expeditions in 2011, 2012 and 2014. The survey was performed in the water area of the sea of Japan and Okhotsk sea. The results indicate that the concentration of 137Cs and 90Sr in sea water, hydrobionts, soil, ground and sea vegetation is still on the baseline level due to the global fallouts.

Estimation of the air kerma rate from <sub>137</sub>Cs and <sub>134</sub>Cs deposited on the ground in the Sakhalin region of Russia after the Fukushima accident

Previous studies conducted by the Federal Service for Surveillance on Consumer Rights Protection and Human Well-Being (Rospotrebnadzor) in Sakhalin Region, Russia in 2011–2012 have shown that soils on the southern Kuril Islands were contaminated with 137Cs and 134Cs due to the accident at the Fukushima-1 NPP. In this study, we evaluated the air kerma rate from 137Cs and 134Cs using earlier published data on the vertical distribution of Fukushima-derived radiocaesium in the soil at grasslands on the islands of Kunashir, Shikotan and Iturup. The air kerma rate due to gamma-rays from pre-Fukushima 137Cs was estimated as well. In the period from May 2011 to September 2012, the air kerma rate due to the fresh fallout of radioactive caesium varied from 0.31 to 0.84 nGy h−1. On average, the contribution of the radiation from Fukushima-derived 134Cs and 137Cs to the total air kerma rate from radioactive cesium was 35% in the fall of 2011 and 25% in the fall of 2012. The mean normalized kerma rate from Fukushima-derived 137Cs was estimated at a level of 1.63 nGy h−1 per kBq m−2 in mid-May 2011, 1.53 nGy h−1 per kBq m−2 in autumn 2011 and 1.45 nGy h−1 per kBq m−2 in autumn 2012. The mean normalized air kerma rate from pre-Fukushima 137Cs at reference undisturbed grasslands was estimated as 0.77 nGy h−1 per kBq m−2. The results of our calculations of the air kerma rate from Fukushima-derived 137Cs were in good agreement with the forecast of the 2013 UNSCEAR model, which was used to estimate the external doses of the Japanese population after the Fukushima accident. For pre-Fukushima 137Cs, the UNSCEAR model underestimated the calculated normalized air kerma rates in Sakhalin Region by approximately 40%. Our calculations showed that, overall, the aboveground biomass of herbaceous plants had practically no effect on the air kerma rate from radioactive cesium contained in the soil. The fallout of 134Cs and 137Cs after the accident at the Fukushima-1 NPP did not lead to any significant increase in the gamma dose rate in the air at grasslands on Kuril Islands. In 2019–2020, the contribution of radiocaesium to the total gamma dose rate in air will not exceed 5%.

Automated System for Monitoring the Radiation Situation at NPP and Environs: a Safety Security Tool

This article is devoted to an automated system for monitoring the radiation situation at NPP and environs. The tasks of the system in accord with the domestic documents and IAEA norms as well as the directions of further development of the system taking account of the experience gained in operating similar systems abroad, specifically, the SPEEDI decision-making support system at the Fukushima-1 NPP (Japan) are formulated. An approach to protecting the general population using the automated system for monitoring the radiation situation at NPP and environs (ASMRS) in accord with the documents of the Rosenergoatom Concern and the IAEA standards is described. Recommendations are presented for formulating a measurement problem in order to fulfill the basic functions of ASMRS as a decision-making support system. The effectiveness of using gamma-spectrometric measurement channels is evaluated by comparing the sensitivity of the dosimetric and spectrometric methods based on two models of the origin of the radioactive cloud above a detector.

Composition of Radioactive Aerosols in the Shelter Construction of the Chernobyl Nuclear Power Plant in 2000–2015

The results of the physicochemical studies of radioactive aerosols inside and outside the Shelter construction at the Arch construction stage of the Chernobyl Nuclear Power Plant (ChNPP) in 2000–2015 were presented. The dominant isotopes were shown to be cesium, strontium, americium, plutonium, and uranium. They are carried by disperse particles of 2–7 μm. In subreactor rooms, in particular, 012/7, the composition of aerosols is affected by the erosion of the fuel-containing mass formed in 1986. Submicron cesium carrier aerosols appear as a result of evaporation and condensation during fires and welding works. Radiocesium is a well-soluble component of aerosols, while plutonium isotopes are not readily soluble components. In several rooms, the contents of radon, thoron, and their daughter products exceeded the permissible values. In April–June 2011, the intake of radionuclides from the accident at the Japanese Fukushima-1 NPP, which had AMAD of ~0.5 μm, was detected and tracked using Petryanov multilayer filters. The productivity of filtration units under the dusty conditions in the exclusion zone of ChNPP and in fogs and haze was investigated. Hydrophilic prefilters with 7–10 μm fibers were recommended.

Distribution and migration of radiocesium in sloping landscapes three years after the Fukushima-1 nuclear accident

The results of the study are presented on the distribution and migration of radiocesium in mountainous (580–620 m a.s.l.) landscapes in the northeast of Honshu Island (Tohoku Region, Miyagi Prefecture) subjected to radioactive contamination after the nuclear accident at Fukushima-1 NPP. In July 2014, the average contamination density with radiocesium (134Сs and 137Сs) over the territory (150 km to the northwest from NPP) was equal to 16 kBq/m2. This contamination is estimated at the acceptable level according to both Japanese and Russian standards and legislation. Three years after the accident, radiocesium is found to be unevenly distributed by the biogeocenosis components, i.e. 45% in litter, 40% in plants, 10% in soil, and 5% in roots. As for the distribution of total radiocesium (Cs tot = 134Сs + 137Сs) by the profile of volcanic podzolic-ocherous soil (Dystric Aluandic Andosols), its maximal content (about 80%) was found in the surface layer (0–2.5 cm), with the specific activity ranging from 250 to 10070 Bq/kg and sharply decreasing with the depth. Radiocesium amount in the soils of forest ecosystems was on average by 20% higher than in meadow ecosystems. Accumulation of radionuclides in soils of lower and middle parts of a slope with an insignificant vertical migration was found to be the most general regularity. The air dose rate did not exceed the maximal permissible level, and the snow cover acted as an absorbing and scattering screen.

Radiation Safety for Incineration of Radioactive Waste Contaminated by Cesium

Problems in the treatment of radioactive waste contaminated by cesium nuclides are considered in the paper. Chornobyl experience in the management of contaminated soil and contaminated forests is analyzed in relation to the accident at Fukushima-1. The minimization of release of cesium aerosols into atmosphere is very important. Radiation influence of inhaling atmosphere aerosols polluted by cesium has damage effect for humans. The research focuses on the treatment of forests contaminated by big volumes of cesium. One of the most important technologies is a pyro-gasification incineration with chemical reactions of cesium paying attention to gas purification problems. Requirements for process, physical and chemical properties of treatment of radioactive waste based on the dry pyro-gasification incineration facilities are considered in the paper together with the discussion of details related to incineration facilities. General similarities and discrepancies in the environmental pollution caused by the accidents at Chornobyl NPP and Fukushima-1 NPP in Japan are analyzed.

The efficiency analysis methods of decontamination of Fukushima Prefecture territory (Japan)

The article deals with the problems of radiological and economic efficiency of decontamination procedures as a measure of eliminating radioactive contamination in scarcely populated residential areas of Fukushima Prefecture (Japan). The objective of the research was to identify and compare with officially declared results the real effects of the decontamination measures on improving the radiation situation and reducing radiation doses for the population in Fukushima region. There was another objective of estimating the expected decontamination expenditure for these territories and the economic efficiency of this measure in accordance with the official international recommendations. The results of such kind of survey for Japan and actual values of the prevented doses due to the decontamination have not been published before. The key objective of this research was to assess the need for decontamination in sparsely populated areas of Fukushima Prefecture taking into account relatively low radiation background in these areas and significant associated financial losses. The initial data for the research have been taken from the Environment Ministry (Japan) reports on the restoration progress in the NPP area. The data on the current radiation situation in Japan have been taken from the Japan Nuclear Regulatory Commission Internet publications. A mathematical modeling of the radiation situation in remediation territories near Fukushima-1 NPP was carried out in the research taking into account the simultaneous impact of several natural and anthropogenic factors. This mathematical model is described in the article. Some empirical dependencies obtained after the Chernobyl accident were also used in it. As the results of the research, the estimated values of actual, predicted and prevented by the decontamination and the resettlement measures doses to residents in one specific Fukushima prefecture municipality were presented. The total and average financial costs per unit of prevented exposure dose for different emergency measures scenarios were estimated, including longterm and short-term evacuation and decontamination. The estimated values of the decontamination and the resettlement effectiveness were presented based on the comparison of the public costs and benefits. The author goes on argue that radiological effectiveness of the decontamination measures was very low. He noted that the measures were inconsistent with the principles of cost optimization in the world radiation protection standards. However, at the same time, the decontamination measures made it possible to prevent possible high costs to the government, and some positive social effects were finally achieved.

Application of sorption-reagent materials in the technology of liquid radioactive waste treatment

Some examples of sorption-reagent materials and variants of their application in the practice of treating liquid radioactive waste have been considered. The data on the strontium sorption on samples of a sorption-reagent material under dynamic conditions at different degrees of dilution and different concentrations of seawater have been presented. These data demonstrate that the most efficient practical applications of sorption-reagent materials consist of decontaminating of seawater concentrates of strontium radionuclides. This task is stated during treatment of liquid radioactive waste (LRW) streams at the Fukushima-1 NPP (Japan), where reverse osmosis concentrates constitute the main problem of localization of the aftermath of the disaster that occurred in 2011.

Prediction of Self-Decontamination of Contaminated Territory Near the Fukushima-1 NPP (Japan)

A method is proposed for analyzing and evaluating the dynamics of self-decontamination of the region of the Fukushima-1 NPP contaminated by radioactive substances. The activity flux into the sea and average self-decontamination time of the territory due to decay and wash-off of the radionuclides 137 Cs and 134 Cs in the region of the NPP are obtained. The wash-off time constant of 137 Cs for the contaminated territory is determined from the experimental data. It is significantly greater than for the basins of the other rivers studied. This is due to the hydrological particularities of the rivers in Japan. It is shown that the maximum dose rate in the region of contamination will decrease to the background level in approximately 200 years. It is determined that the 137 Cs concentration in suspension does not depend on the water flow rate in the river; the 137 Cs flux is proportional to this flow rate, including in floods. Accidents at objects using nuclear power which are accompanied by the emission of radioactive substances, as a rule, lead to long-time contamination of the environment, which ultimately determines the radioactive effect on humans. In this connection, it is important to make a well-grounded quantitative prediction of the redistribution of radionuclides between different natural objects and the associated changes in the strength of the effect. The results of such a prediction for the region of radioactive contamination near the Fukushima-1 NPP are presented in this article. The prediction takes account of specific features, the main one being the intense wash-off of radionuclides by surface runoff from a river basin into the sea. The most complete data on the radioactive contamination of the region of the Fukushima-1 NPP are presented in [1], where the discharge into the atmosphere, deposition on the soil, density of the soil contamination by 137,134 Cs, 131 I, 129m Te, 110m Ag, 90 Sr, and 238‐240 Pu are indicated. For some of these isotopes, the depth distribution in the soil, the concentration in the water along the sea coast and the banks of the Abukuma River, flowing through the contaminated territory in the region of the NPP, as well as the bottom deposits in the sea and river are presented. Compared with the Chernobyl accident, the discharge and maximum density of the 137 Cs contamination were almost 10 times less, 22% of the 137 Cs discharged was on dry land, and the remainder was carried into the ocean [1]. The high level of radioactive contamination raises the question of the need to predict the reduction in the density of radioactive contamination and the total content of radioactive elements on this territory. The reduction in the radioactive contamination of the territory in time is due to decay and wash-off of the radionuclides by the surface run-off into the river and then into the sea. In [1, 2], the question of the need to solve such problems is raised, but steps to solving it are not mentioned. Methodological Basis of Prediction. A prediction of contamination can be based on a model of the transport of radionuclides in the river‐river-basin system as described in [3] by an equation for the density of the radioactive contamination of the basin σ = σ(y, t), which is a function of the time t and the coordinate y measured from the external boundary or a section of it:

Reconstruction of the North-West Radioactive Track During the Accident at the Fukushima-1 Npp (Japan) Using Sokrat/V3 and Prolog Software

The radioactive track formed on March 15, 2011 during the accident at the Fukushima-1 nuclear power plant (Japan) is reconstructed using the PROLOG–SOKRAT/V3 software system. The emission of radionuclides into the atmosphere and the radiation conditions are estimated taking account of the complex relief of the location. Comparing the computed activity, radionuclide composition and fallout density showed satisfactory agreement with actual measurements.

BWR-4 safety systems serviceability during blackout at the Fukushima-1 NPP (Japan)

During the serious accident at the Fukushima-1 NPP (Japan), the cores of the Nos. 2 and 3 units were cooled for a long period of time by safety systems which were not designed for operation under prolonged power loss. The serviceability of BWR-4 high-head makeup systems and the reasons for their failure are analyzed. It is shown that taking dc losses in the No. 2 unit into account the makeup system remained serviceable in the unanticipated regime. The shutdown of the makeup systems in both units could have been due to the maximum backpressure being reached at the turbine outlets or by cavitation in the turbopumps. It is shown that it is important to make a realistic assessment of the depletion time of the storage batteries in the No. 3 unit.

Observation of radioactive aerosols in chernobyl after the accident at the fukushima-1 npp

The results of a determination of the concentration and dispersity of radioactive aerosols in the local zone of the Cover in spring 2011 are presented. Aside from aerosols ‐ products of the accident at the Chernobyl NPP in 1986, technogenic 131,132 I, 132 Te, and 134,136 Cs contained in the emissions from the damaged units of the Fukushima-1 NPP and spreading in the Northern Hemisphere were found. It was determined that technogenic 131 I and 134 Cs and naturally occurring 7 Be and 210 Pb were present on the carriers of similar activity median aerodynamic diameter <1 μm. It is shown that the content of radioactive aerosols ‐ products of the accident at the Fukushima-1 NPP did not exceed the admissible concentration of radionuclides in air for the population and did not make a substantial additional contribution to the dose load to workers at the site of the Cover.

Estimation of radionuclide emission during the march 15, 2011 accident at the fukushima-1 npp (japan)

Transport of radioactive substances in the atmosphere was modeled on the basis of the Lagrangian stochastic model of the dispersion of radionuclides in the atmosphere. The WRF-ARW regional hydrodynamic model was used to reproduce the change of atmospheric conditions. Radiation monitoring data showed that the main radioactive contamination of the territory of Japan occurred on March 15, 2011. For the rest of the time the radioactive cloud was carried by the wind, mainly in the direction of the Pacific Ocean. Estimates of the equivalent dose rate at the points where the radiation conditions were monitored on the territory of Japan were obtained by modeling the transport of radioactive substances taking account of actual atmospheric conditions. The computed equivalent dose rate differs by a factor of 2–3 from the results of aerial gamma surveys. The computed 137Cs content differs from the measured value by not more than 50 %.

Analysis of the effect of radiation criteria for population evacuation on the socioeconomic consequences of the npp accident in fukushima prefecture (japan)

The social and economic consequences of the March 11, 2011 radiation accident at the Fukushima-1 NPP in Japan are analyzed. Data on the contamination of the territory and the expected dose load to the population are presented. The number of inhabitants who as a result of the accident were present on contaminated territory and the economic losses due to the evacuation measures as estimated by the Technical Crisis Center at IBRAE RAN are given. The results are compared with data obtained by foreign specialists.

Actionable analysis of the accident at the fukushima-1 nuclear power plant (japan) and prediction of its consequences

The work done by the Technical Crisis Center at the Institute of Problems in the Safe Development of Nuclear Energy of the Russian Academy of Sciences on providing scientific-technical support to the National Control Center for Crisis Situations of the Russian Ministry of Emergency Situations and Crisis Situation Center at Rosatom during the first few days and subsequent period after the accident at the Fukushima-1 NPP in Japan in March 2011 is described. The results of computer calculations of possible development of the situation in the power-generating units of the damaged NPP, predictions of the dynamics of the change of the radiation conditions near and at large distances from the NPP, right up to the Far East territory of our country as well estimates of the irradiation dose to the population are presented.