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Atomic energy has played an important role in international relations as a means of state power. From 1945 to 1959, Japan was significantly influenced by developments in atomic energy as a result of the Anglo-American "special relationship." During World War II, Britain and the United States cooperated to develop atomic weapons to use against Japan. In the ensuing Cold War era, the two countries advanced peaceful uses of atomic energy for Japan to counter the influence of the Soviet Union through psychological warfare. The U.S. Atomic Energy Peace Mission visited Japan in May 1955. However, the Japanese government altered its nuclear policy to solicit support from Britain because the United States was falling behind in atomic energy development. A British nuclear reactor was used as the first commercial nuclear power station, in 1959, whereby Britain earned parity with the United States in the context of nuclear power. [ABSTRACT FROM AUTHOR]

The medical situation during disasters often differs from that at usual times. Disasters can lead to significant mortality that can be difficult to monitor. The types of disaster-related deaths are largely unknown. In this study, we conducted a survey to categorize the disaster-related deaths caused by a radiation disaster. A total of 520 people living in Minamisoma City, Fukushima Prefecture, at the time of the Fukushima Daiichi Nuclear Power Plant accident, who were certified to have died due to disaster-related causes were surveyed. We divided the participants into those who were at home at the time of the earthquake and those who were in hospitals or facilities when the disaster struck and conducted a hierarchical cluster analysis of the two groups. Disaster-related deaths could be divided into seven groups for those who were at home at the time of the disaster and five groups for those who were in hospitals or facilities at the time of the disaster. Each group showed different characteristics, such as "the group with disabilities," "the group receiving care," and "the group with depression," and it became evident that not only uniform post-disaster support, but support tailored to the characteristics of each group is necessary. [ABSTRACT FROM AUTHOR]

The Fukushima Daiichi Nuclear Power Plant accident, triggered by the Great East Japan Earthquake and the tsunami, has had a major impact on societies across the world. The subsequent focus on decommissioning efforts has attracted worldwide attention. It has been consistently asserted since the aftermath of the accident that the decommissioning of the Fukushima Daiichi Nuclear Power Plant will take approximately 30 to 40 years. The promotion of decommissioning work means that we will continue to face the problems with uncertainties in the work, as sometimes referred to as Unknown Unknowns. Typical elemental technologies required in remotely operated robotic systems for decommissioning include mobile mechanisms and their control, handling mechanisms and their control, information communication, operation interface (information presentation and command input), shielding (radiation resistance) and so on. Although many tasks using remotely operated robotic systems have been carried out with noteworthy results, there are lingering issues yet to be clarified. To ensure the safe and effective execution of various types of decommissioning tasks over a period of several decades, continuous research and development of each elemental technology are imperative, and these technologies must be integrated into a system appropriately to the assumed tasks. In addition, human resource development and the transfer of knowledge and experience are also important issues. From such viewpoint, this special issue is titled "Robotic, Mechatronic and Information Systems for Decommissioning." It contains papers and development reports on robotics, mechatronics, information processing, and information systems technologies relevant to decommissioning work. It also features recent activities of nuclear emergency response organizations. We hope this special issue will acquaint readers with the latest research and development results and organizational activities related to decommissioning. At the same time, we hope that we were able to provide readers interested in robots, mechatronics, and information technology with an opportunity to become aware of the issues and necessary perspectives related to decommissioning and nuclear disasters. Lastly, we would like to thank the editorial board of the Journal of Robotics and Mechatronics, the editorial team of Fuji Technology Press, and the reviewers for their support in the planning and publication of this special issue. Their dedicated efforts are deeply appreciated. [ABSTRACT FROM AUTHOR]

Improper operation leading to an emergency shutdown in a nuclear power plant can result in significant energy loss and have a substantial impact on the economy. This study focuses on a sodium-cooled fast reactor (SFR) nuclear power plant, analyzing system characteristics under different accidents through feedwater system simulation and improving control system performance. The results show that the single module accident will affect the whole feedwater system, and the influence of faulty SG on the loop signal should be eliminated. The improved control system reduces sodium temperature fluctuation by 3%–41.5%, shortens adjustment time by 57.9%, and ensures standby pump activation within 10 s after the feedwater pump trips or when the system stabilizes. Although the feedforward of mass flowrate ratio can improve the response of the system to flow disturbance, it resists the temperature feedback. However, considering inlet temperature's impact on feedwater demand, this confrontation can be effectively avoided, and a good control effect can be maintained during accidents. • The third circle accident of sodium-cooled fast reactor is simulated. • An improved feedwater control system, based on energy balance, is proposed. • Recommendations for addressing different types of accidents in the third circuit are provided. • The performance of feedwater system under accident has been significantly improved. [ABSTRACT FROM AUTHOR]

Radionuclides from the reactor accident Fukushima Daiichi nuclear power plant were observed in the airborne aerosols at CTBT International Monitoring System (IMS) stations (MRP43, CMP13) in Africa. The maximum activity concentrations in the air measured in Mauritania were 186.44 10−6 Bq.m−3, 264.16 10−6 Bq.m−3 and 1269.94 10−6 Bq.m−3 for 134Cs, 137Cs and 131I respectively, and in Cameroon 16.42 10−6 Bq.m−3, 25.53 10−6 and 37.58 10−6 Bq.m−3 respectively for 134Cs, 137Cs and 131I. The activity ratio of 134Cs/137Cs is almost constant throughout the period of time relevant to this study due to their long half-lives of 30.2 years for 137Cs and 2.06 years for 134Cs. Whereas the 131I/137Cs activity ratio varies in time according to the radioactive decay with a half-live of 8.06 days for 131I and different removal rates of both radionuclides from the atmosphere during transport. The EMAC atmospheric chemistry-general circulation was used to simulate the emission and transport of the isotope 137Cs and map the deposition of the 137Cs deposition over Africa. • IMS stations in Africa (MRP43, CMP13) detected first 131I, caesium isotopes appearing with a delay of 6 days in Cameroon and 4 days for 134Cs in Mauritania. • The highest activity concentrations of fission products were found in Mauritania. • The EMAC atmospheric chemistry-general circulation was used to simulate the emission and transport of the isotope 137Cs and map the deposition of the 137Cs deposition over Africa. [ABSTRACT FROM AUTHOR]

Since 2018, the use of AP1000 nuclear technology has been growing due to its advantages in terms of nuclear safety and security. Knowing that the occurrence rate of the serious nuclear reactor accidents has increased due to the natural disasters that the world has encountered in recent decades, such as earthquakes, floods, tsunamis, etc., we propose to carry out an impact study and analyze the consequences of these accidents, with the aim of avoiding exposure of the public and workers to ionizing radiation. This work is divided into two sections: firstly, calculate the source term by using the ORIGEN-JR depletion code, and compare the obtained results with those published in the document AP1000 Design Control. The obtained results are in agreement with the literature. Secondly, starting from the results of the source term calculation, we have evaluated the atmospheric dispersion using health HotSpot code. The Total Effective Doses (TED) is estimated over two meteorological periods: the first period, from April to August, and the second one, from September to March. The simulation results showed that the TED was higher, around 27 Sv at 0.6 km from the source during the April–August period. However, for the second period, the TED is about 8 Sv at 2 km from the source. Generally, the TED of all radionuclide groups exceeds the IAEA annual regulatory limits, which are one millisievert per year (1 mSv/year) for public exposure and twenty millisieverts per year (20 mSv/year) for occupational exposure of workers. Therefore, the probability of risks to workers, the public, and the environment rises. There are generic criteria for acute doses, according to which preventive actions must be taken in all circumstances in order to minimize the serious effects of radionuclides on the population. • Computing the source term of eight radionuclide groups using the ORIGEN JR code for an AP1000 reactor. • Predicting the early atmospheric dispersion of radionuclides using the HotSpot code in the event of a hypothetical accident. • Compare the obtained results of the source term with those published in the document AP1000 Design Control. • The TED, GD, Different pathways of exposure and CEDE for some human body organs are estimated. • The results provide important information for severe accident management and safety assessment. [ABSTRACT FROM AUTHOR]

• Assessment of the acute and chronic exposure situations in a hypothetical accident of long term station black out at the proposed Buyende nuclear site in Uganda. • Total effective dose equivalents and thyroid dose at the exclusion are boundary and emergency protection zone were within the regulatory limits. Uganda's energy policy of 2023 and Vision 2040 plans to address the country's electricity shortage by introducing nuclear power of 24,000 MW capacity by 2040. The pioneer nuclear power plants with a generation capacity of 8,400 MW will be built in Buyende District. This study focused on assessing the radiological consequences of potential nuclear accident on any of the four technologies of APR1400, VVER1200, HPR1000, and APR1000. Evaluation of acute and chronic radiation effects from a long-term station blackout accident using RASCAL and GENII codes identified the order of minimum health risks to the public as APR100, HPR1000, VVER1200, and APR1400 if single units are constructed. The total effective dose equivalents and thyroid doses at the exclusion area boundary and emergency protection zone were within the regulatory limits of 250 mSv and 3,000 mSv, respectively for all the reactor technologies. [ABSTRACT FROM AUTHOR]

In order to further clarify the fire safety evaluation of nuclear grade activated carbon, thermal analysis combined with pore structure and phase analysis was adopted for coal-based activated carbon and coconut shell activated carbon used in nuclear power plants. On the basis of establishing the relative fire safety evaluation model by using four important parameters: activation energy (E), maximum mass loss rate (DTG p), maximum mass loss rate temperature (T p) and rapid reaction percentage (A 12), the O/C ratio and enthalpy (H) were further introduced into the evaluation model to calculate the relative fire safety factor (RFSF). The results show that O/C ratio and enthalpy have greater influence on the fire safety of activated carbon than porosity characteristics. The RFSF values of coal-based and coconut shell activated carbon are 1.33 and 1.08, indicating that fire safety is higher than that of impregnated coconut shell activated carbon. • A relatively perfect fire safety evaluation model of nuclear grade activated carbon was successfully established. • The O/C ratio and enthalpy have greater influence on the fire safety of activated carbon than porosity characteristics. • RFSF of CBAC and CSAC are 1.33 and 1.08, indicating that fire safety is higher than that of ICSAC. • The introduction of O/C ratio and enthalpy will further improve the evaluation model of relative fire risk. [ABSTRACT FROM AUTHOR]

Regulators around the world have devised practical methods for evaluating the safety of nuclear power plants (NPPs) and increasing public awareness of plant safety. One essential approach is the regulatory safety-related inspection, which plays a crucial role in confirming the safety of power plants to prevent and mitigate accidents. In recent years, many developed countries have adopted a risk-informed methodology, which, similar to the conventional deterministic approach, prioritizes various aspects of regulatory inspection which relies on PSA insights for decision-making, rather than being rooted in a deterministic approach. In the United Arab Emirates, where three nuclear units are in operation, the regulatory inspection focuses on reducing the likelihood of incidents through a defense-in-depth (DiD) concept and the insights gained from risk analysis. To strengthen accident prevention oversight, both deterministic and probabilistic approaches are utilized, including probabilistic risk assessments (PRA) aimed at identifying safety improvements. This study aims to develop a preliminary safety inspection methodology using AIMS-PSA as an analysis tool. It involves constructing event trees and fault trees to understand how to secure the success path of Loss of Coolant Accidents (LOCAs) transients, block potential failure paths, and assess their impact on Core Damage Frequency (CDF) by analyzing the generated cut sets. This study will offer quantifiable insights into key risk factors, improving our capacity to anticipate and prevent accidents, maintain high reliability, and conduct effective risk assessments for the continued operability of safety systems. While previous investigations have explored nuclear accident frequencies, often with limitations, this research aims to provide a more comprehensive perspective on nuclear power plant safety, addressing a wide range of accident scenarios and their implications. • Regulatory safety inspections are crucial for verifying nuclear power plant safety. • The UAE's focus on minimizing incident probability using a defense-in-depth approach. • AIMS-PSA is used to analyze LOCA transient success and failure paths. • The study identifies core contributors to risk and aids in accident anticipation. • The methodology enhances safety, reliability, and long-term accident mitigation. [ABSTRACT FROM AUTHOR]

• Anaerobic wet fermentations were conducted for treating genuine radioactive grass. • Alkaline-heat and ultrasonic methodologies were used to pre-treat the grass. • Alkaline-heat-treated grass showed an optimal anaerobic conversion efficiency. • Pre-treatments and wet fermentations barely leached Rad-Cs from grass. • Soil with high cesium affinity mixed with grass limited the Rad-Cs leaching. Persistent concerns regarding environmental hazards arise from the difficulty in disposing of radioactive plant-based wastes originating from the nuclear accident at the Fukushima Daiichi Nuclear Power Plant (FNPP) in Japan in 2011. In this study, three anaerobic digestion (AD) strategies were proposed: Sole anaerobic wet fermentation, and wet fermentations with either alkaline-heat or ultrasonic pre-treatment, which were employed for long-term anaerobic treatment of a genuine radioactive grass stemming from the FNPP accident. The objectives of this work are to investigate the effects of pre-treatments on biomass conversion efficiency and to gain insight into the leaching behavior of radiocaesium (Rad-Cs) within AD processes. Experimental results indicate that by introducing alkaline-heat and ultrasonic pre-treatments to AD systems, the removal efficiencies of total solids (TS) from the raw grass increased by 60.8 % and 42.5 %, respectively, compared to sole wet fermentation. Pre-treatments have been shown to enhance the stability of AD systems, both in terms of enhancing methane production and mitigating pH fluctuations triggered by the accumulation of organic acids. Remarkably, even though the Rad-Cs leaching rate was highest when the AD system was fed with the alkaline-heat pre-treated grass, it remained unsatisfactory at only 5.77 %. We inadvertently isolated a soil-like component from the raw grass, and analyzed both its proportion in the raw grass and the radioactivity intensity. The results indicate that although the soil constituted only 9.51 % TS of the raw grass, it accounted for a significant 81.35 % of the total radioactivity. The soil, which has a pronounced affinity for ionic Cs, being mixed into the raw grass, was identified as the primary factor limiting the leaching efficiency of Rad-Cs throughout both the pre-treatment and wet fermentation phases. [Display omitted] [ABSTRACT FROM AUTHOR]

Following the accident at the Fukushima Dai-ichi Nuclear Power Station, radiocaesium concentrations were specifically elevated in rockfish species compared to other fish species. To clarify the likely reasons, a caesium metabolic rate in the Japanese rockfish Sebastes cheni was derived by an aquarium experiment of live fish collected from the area off Fukushima. Stable caesium and 137Cs concentration in prey organisms, stomach contents and muscle of rockfish were measured and the bioavailable fraction in prey organisms was evaluated. Using derived transfer parameters, 137Cs radioactivity levels in S. cheni and prey organisms were simulated by a model, and verified by the measured radioactivity concentrations of biota in coastal waters south of the Fukushima Dai-ichi Nuclear Power Station. As a result, slow caesium metabolism in S. cheni was confirmed with the biological half-life (Tb 1/2) of 190 d. The determining factor for the initial 137Cs radioactivity levels in S. cheni , was the maximum radioactivity levels in surrounding seawater which was constrained by the sedentary nature of rockfish. Controlling factors of depuration rate of 137Cs levels in S. cheni were slow caesium metabolism, enhanced 137Cs radioactivity level of prey organisms, and survival of older contaminated individuals due to a long life-span. During the study period 2017–2021, 137Cs radioactivity concentrations in seawater decreased close to the level measured before 2010, whereas those in prey organisms and rockfish in southern Fukushima waters were still above the levels that existed before 2010. An additional source for enhancing 137Cs radioactivity in rockfish and biota of the food chain was indicated by the greater 137Cs/133Cs atom ratios in rockfish compared to those in the surrounding seawater, however it was considered to be radiologically insignificant in relation to seafood safety limits. • Very slow radiocaesium excretion confirmed in rockfish. • Depuration in rockfish was delayed by 137Cs transfer from prey. • 137Cs excretion in contaminated old fish completed after 10 years. • 137Cs transfer among rockfish and adjacent ecosystems reached equilibrium after 2019. [ABSTRACT FROM AUTHOR]

[Display omitted] • Two cationic flexible COFs have been synthesized by post-functionalization method. • The I 2 uptake capacities of cationic flexible COFs are higher that of neutral ones. • The segregative bromides and iodides can induce I 2 to engender polyiodides. • The iodine adsorption amounts and the rates increase with temperature. With the incresing development of nuclear power plants, the radioactive iodine produced from nuclear waste and nuclear accidents poses increasing threat to the human health and environment. The iodine adsorption behavior of the neutral flexible covalent organic skeleton has been somewhat studied, but to our knowledge, there are no reports of iodine capture by ionized flexible COFs. Herein, we apply a post-functionalization process to construct two cationic flexible COFs (iCOFs-AB-1 and iCOFs-AB-2) for the first time. The iCOFs-AB-1 and iCOFs-AB-2 exhibit I 2 uptake capacities of 3.36 and 4.26 g g−1 at 77 °C, which are improved 1.19 and 1.14 times compared to that of neutral flexible COFs. The promotion of ionic groups on iodine adsorption and the iodine valence states adsorbed at diverse sites have identified by experiments. The adsorption mechanism studies show that the segregative bromide and iodide anions in iCOFs-AB-1 and iCOFs-AB-2 can induce molecular iodine to engender polyiodide anions, and the quaternary ammonium salt cations in iCOFs-AB-1 and iCOFs-AB-2 can come into being the Coulomb interaction force with the aforementioned polyiodide anions. This study demonstrates an efficient method to synthesize cationic flexible COFs and further use them as adsorbents for capturing iodine. [ABSTRACT FROM AUTHOR]