Central Research Institute of Electric Power Industry
Recent publications
In April 2011, the International Commission on Radiological Protection recommended reducing the occupational equivalent dose limit for the lens. Such a new occupational lens dose limit has thus far been implemented in many countries, and there are extensive discussions toward its regulatory implementation in other countries. In Japan, discussions in the Japan Health Physics Society (JHPS) began in April 2013 and in Radiation Council in July 2017, and the new occupational lens dose limit was implemented into regulation in April 2021. To share our experience, we have published a series of papers summarizing situations in Japan: the first paper based on information available by early 2017, and the second paper by early 2019. This paper (our third paper of this series) aims to review updated information available by mid-2022, such as regarding regulatory implementation of the new occupational lens dose limit, recent discussions by relevant ministries based on the opinion from the council, establishment process of safety and health management systems, the JHPS guidelines on lens dose monitoring and radiation safety, voluntary countermeasures of the licensees, development of lens dose calibration method, and recent studies on exposure of the lens in nuclear workers and biological effect on the lens.
Current–voltage characteristics of an n-type 4H-silicon carbide (SiC) epilayer containing a stacking fault (SF) were analyzed using a technology computer-aided design (TCAD) simulation. In the simulation, the SF was modeled by a quantum well (QW) formed in the conduction band, which traps electrons and induces a potential barrier. The simulation analysis clarified that the electron conductance in the n-type epilayer containing a SF was dominantly determined by the potential barrier height. Based on this insight and the experimental results obtained from our previous study, the energetic depth and width of the QW in the conduction band were deduced for four types of SFs. The temperature dependence of the experimental current–voltage characteristics of Schottky barrier diodes (SBDs), containing the SF, was effectively reproduced by adopting the deduced QW depth and width, proving the feasibility of the proposed simulation model quantitatively predicting the impacts of SFs on SiC unipolar device performances.
Purpose: Increasing epidemiological and biological evidence suggests that radiation exposure enhances cancer risk in a dose-dependent manner. This can be attributed to the "dose-rate effect," where the biological effect of low dose-rate radiation is lower than that of the same dose at a high dose-rate. This effect has been reported in epidemiological studies and experimental biology, although the underlying biological mechanisms are not completely understood. In this review, we aim to propose a suitable model for radiation carcinogenesis based on the dose-rate effect in tissue stem cells. Methods: We surveyed and summarized the latest studies on the mechanisms of carcinogenesis. Next, we summarized the radiosensitivity of intestinal stem cells and the role of dose-rate in the modulation of stem-cell dynamics after irradiation. Results: Consistently, driver mutations can be detected in most cancers from past to present, supporting the hypothesis that cancer progression is initiated by the accumulation of driver mutations. Recent reports demonstrated that driver mutations can be observed even in normal tissues, which suggests that the accumulation of mutations is a necessary condition for cancer progression. In addition, driver mutations in tissue stem cells can cause tumors, whereas they are not sufficient when they occur in non-stem cells. For non-stem cells, tissue remodeling induced by marked inflammation after the loss of tissue cells is important in addition to the accumulation of mutations. Therefore, the mechanism of carcinogenesis differs according to the cell type and magnitude of stress. In addition, our results indicated that non-irradiated stem cells tend to be eliminated from three-dimensional cultures of intestinal stem cells (organoids) composed of irradiated and non-irradiated stem cells, supporting the stem-cell competition. Conclusions: We propose a unique scheme in which the dose-rate dependent response of intestinal stem cells incorporates the concept of the threshold of stem-cell competition and context-dependent target shift from stem cells to whole tissue. The concept highlights four key issues that should be considered in radiation carcinogenesis: i.e., accumulation of mutations; tissue reconstitution; stem-cell competition; and environmental factors like epigenetic modifications.
While power shortages during and after a natural disaster cause severe impacts on response and recovery activities, related modeling and data collection efforts have been limited. In particular, no methodology exists to analyze long-term power shortages such as those that occurred during the Great East Japan Earthquake. To visualize a risk of supply shortage during a disaster and assist the coherent recovery of supply and demand systems, this study proposes an integrated damage and recovery estimation framework including the power generator, trunk distribution systems (over 154 kV), and power demand system. This framework is unique because it thoroughly investigates the vulnerability and resilience characteristics of power systems as well as businesses as primary power consumers observed in past disasters in Japan. These characteristics are essentially modeled by statistical functions, and a simple power supply-demand matching algorism is implemented using these functions. As a result, the proposed framework reproduces the original power supply and demand status from the 2011 Great East Japan Earthquake in a relatively consistent manner. Using stochastic components of the statistical functions, the average supply margin is estimated to be 4.1%, but the worst-case scenario is a 5.6% shortfall relative to peak demand. Thus, by applying the framework, the study improves knowledge on potential risk by examining a particular past disaster; the findings are expected to enhance risk perception and supply and demand preparedness after a future large-scale earthquake and tsunami disaster.
Objective To systematically review and perform a meta-analysis of radiation associated risks of cardiovascular disease in all groups exposed to radiation with individual radiation dose estimates. Design Systematic review and meta-analysis. Main outcome measures Excess relative risk per unit dose (Gy), estimated by restricted maximum likelihood methods. Data sources PubMed and Medline, Embase, Scopus, Web of Science Core collection databases. Eligibility criteria for selecting studies Databases were searched on 6 October 2022, with no limits on date of publication or language. Animal studies and studies without an abstract were excluded. Results The meta-analysis yielded 93 relevant studies. Relative risk per Gy increased for all cardiovascular disease (excess relative risk per Gy of 0.11 (95% confidence interval 0.08 to 0.14)) and for the four major subtypes of cardiovascular disease (ischaemic heart disease, other heart disease, cerebrovascular disease, all over cardiovascular disease). However, interstudy heterogeneity was noted (P<0.05 for all endpoints except other heart disease), possibly resulting from interstudy variation in unmeasured confounders or effect modifiers, which is markedly reduced if attention is restricted to higher quality studies or those at moderate doses (under 0.5 Gy) or low dose rates (under 5 mGy/h). For ischaemic heart disease and all cardiovascular disease, risks were larger per unit dose for lower dose (inverse dose effect) and for fractionated exposures (inverse dose fractionation effect). Population based excess absolute risks are estimated for a number of national populations (Canada, England and Wales, France, Germany, Japan, USA) and range from 2.33% per Gy (95% confidence interval 1.69% to 2.38%) for England and Wales to 3.66% per Gy (2.65% to 4.68%) for Germany, largely reflecting the underlying rates of cardiovascular disease mortality in these populations. Estimated risk of mortality from cardiovascular disease are generally dominated by cerebrovascular disease (around 0.94-1.25% per Gy), with the next largest contribution from ischaemic heart disease (around 0.30-1.20% per Gy). Conclusions Results provide evidence supporting a causal association between radiation exposure and cardiovascular disease at high dose, and to a lesser extent at low dose, with some indications of differences in risk between acute and chronic exposures, which require further investigation. The observed heterogeneity complicates a causal interpretation of these findings, although this heterogeneity is much reduced if only higher quality studies or those at moderate doses or low dose rates are considered. Studies are needed to assess in more detail modifications of radiation effect by lifestyle and medical risk factors. Systematic review registration PROSPERO CRD42020202036.
There are two failure criteria in seismic probabilistic risk assessment of a nuclear power plant to define component failure caused by an earthquake. The first is in terms of peak ground acceleration and peak ground acceleration capacity. The second is in terms of seismic response and component capacity. These criteria are closely related, but they are not equivalent. One can derive a different fragility curve from the second criterion. First, this study analytically shows the relation of these failure criteria, pointing out that a fragility curve may not represent the uncertainty of a failure probability derived from the second criterion. In addition, we propose a probability density function of a failure probability based on the second criterion using the transformation of a random variable method applied to probability density functions of seismic response and component capacity. Then, we derive a new fragility curve based on the derived probability density function. Also, we show that the derived probability density function links to a likelihood function based on a mean fragility curve used in the literature. Finally, we discuss the non-identifiability of uncertainties of response and capacity, and we propose a Bayesian model utilizing a local response to overcome the non-identifiability.
Battery energy storage systems (BESSs) play extremely important roles in managing power supply and demand in a microgrid. The BESSs, on the other hand, have problems of high initial investment costs and limited lifetime. In this paper, a problem formulation and its solution are presented for sizing an aggregated BESS in a microgrid that minimizes the sum of initial costs of the aggregated BESS and operational costs of the microgrid. The target problem is originally categorized into a bilevel optimization because it comprises two optimization problems: the sizing of aggregated BESS and the operational scheduling of microgrid’s components. The authors, however, apply the Karush–Kuhn–Tucker approach and reformulate the target problem as a single-level optimization problem. This reformulation enables us to treat the problem as if it was a type of operation scheduling problems. That is, the solution techniques developed to obtain the optimal operation scheduling are applicable by the problem reformulation. As the basis for the solution method, an algorithm combining binary particle swarm optimization and quadratic programming is applied in this paper. To verify the validity of the proposal, numerical simulations are performed, and their results are discussed.
A two-step system identification is presented to estimate modal properties of a base-fixed model from ambient vibration records on a multi-story building with soil-structure interaction (SSI). In the first step the output-only identification of the stochastic subspace method is employed for estimating modal properties with SSI. In the second step the modal properties of the base-fixed model are modified from the first estimates, by using theoretical relations between the multi-degree-of-freedom model with SSI and its equivalent base-fixed model derived in the paper. Two examples in numerical and real-world tests are demonstrated to show applicability in the two-step system identification.
In this chapter, we will discuss how to utilize the new systems approach, taking as an example the electric power infrastructure, which is currently undergoing a major transformation, among the social infrastructures. First, we will show the issues of the current power infrastructure, and then present the specific utilization method of the new systems approach described in this book. Next, we will present the purpose and outline of typical markets, including new markets that are expected to open in Japan in the future to realize smarter distributed market mechanism to optimally operate power systems with collaborating among many electric companies, distributed energy resources, and consumers.
This paper reports demonstration results of non‐contact out‐of‐plane vibration energy harvesting using an electric‐double‐layer electret (EDLE). Unlike contact types or non‐contact in‐plane types, the proposed operation type can be useful in terms of expanding the operating frequency range and simplifying the device structures. A demonstration system is developed, and power generation is confirmed using an EDLE with a surface potential of −1 V under an atmospheric condition. © 2023 Institute of Electrical Engineers of Japan. Published by Wiley Periodicals LLC.
UC (unit commitment) for grid operation has been attracting increasing attention due to the growing interest in global warming. Compared to other methods, MILP, which is one of the calculation methods for UC, has the disadvantage of a long calculation time, although it is more accurate in considering constraints and in finding solutions. However, RLCs (representative load curves) require a more accurate clustering method to select representative dates because the calculation results vary greatly depending on the clustering method. DBSCAN, one of the clustering methods, has the feature that the clustering accuracy varies depending on two parameters. Therefore, this paper proposes two algorithms to automatically determine the two parameters of DBSCAN to perform RLCs using DBSCAN. In addition, since DBSCAN has the feature of being able to represent different data as two-dimensional elements, a survey of the data to be used as clustering was conducted. As a result, the proposed algorithms enabled a more accurate clustering than the conventional method. It was also proved that clustering including temperature and load demand as clustering classification factors enables clustering with higher accuracy. The simulation with shorter time was also possible for the system including storage batteries as a demand response.
There is concern among the general public that information technology (IT) innovations may make existing jobs redundant. This may be perceived to pose a greater problem to future generations because new technologies, not limited to IT innovations, will be sophisticated in the future. Our previous work revealed that messages reminding people of familial support as a nudge can moderate risk-averse attitudes toward risks that are perceived to threaten future generations, which could be effective for other kinds of risks. Therefore, we conducted a randomized controlled trial to examine the message effects for information provision on IT innovations. The study was conducted via an online questionnaire survey in January 2020, before the COVID-19 pandemic, and more than 3,200 samples were collected from respondents aged 20 years or older living in Japan. The treatment groups received basic information supplemented with additional text or additional text and an illustration that highlighted IT innovations as support from previous generations. The control group received only the basic textual information. The effects of the intervention were evaluated by comparing changes in average subjective assessment of IT in the treatment groups with those in the control group. The intervention effect was statistically significant, and the sense of familial support after receiving the intervention messages was significantly increased in the treatment group that viewed the illustration compared with the control group. Additionally, we discuss how each component of the HEXACO personality traits influences responses to the intervention messages. Through a series of surveys, we demonstrated the potential of our framework for a wide variety of applications involving information provision perceived to involve future generations.
Paddy fields in the agricultural landscape have become alternative habitats for natural wetland species. Habitat degradation, including habitat loss and fragmentation, is a major threat to members of Amphibia, which is a good indicator species for the Satoyama landscape. Recently, linear artificial structures, such as roads and railways, were recognized as factors inhibiting amphibian population persistence. Thus, irrigation canals and cement-walled streams may also affect amphibian movement and dispersal in the rural agricultural landscape termed Satoyama, which is now the main habitat for lowland wetland amphibians. However, there is limited information on such effects. Here, we focused on the Japanese brown frog (Rana japonica), which is an indicator species of the ecosystem health of the Satoyama landscape, to investigate the effects of irrigation canals on population structure. The barrier effects of roads and irrigation canals on gene flow between breeding sites were evaluated. We constructed a resistance map of the limiting factors to gene flow based on land use and frog movement and tested for correlations between cost and genetic distances. The habitat resistance values alone were insufficient to explain the genetic distances among breeding sites. Thus, we hypothesize that irrigation canals and roads have barrier effects on gene flow among amphibians in the Japanese Satoyama landscape.
Flow-Accelerated Corrosion (FAC) is a pipe wall thinning phenomenon to be monitored and managed in the power plants with high priority. Its management has been conducted with conservative evaluation of thinning rate and residual lifetime of piping based on wall thickness measurements. However, in the actual plants, noticeable case of the wall thinning occurred in branch and junction piping (T tube). There is a problem to manage the wall thickness of the part covered by reinforcing plate of the T tube, because measurement of this area is difficult to be conducted with ordinary ultrasonic testing devices due to the presence of the reinforcing plate. In this study, numerical flow analysis for the T tube was conducted, and the wall thinning profile due to the FAC was evaluated by calculating the mass transfer coefficient. It was found that a localized wall thinning distribution occurs in the area where the reinforcement plate of the T tube exists. And this tendency is affected by pipe geometry and Reynolds number. In previous studies, a model that functionalized by pipe geometry and Reynolds number was introduced to predict this wall thinning trend. In this paper, the effectiveness of the proposed decay function was confirmed by comparing it with measurements taken in actual plants. It was shown that the maximum wall thinning rate at the T tube junction, including below the reinforcing plate, can be evaluated conservatively within an appropriate range by making corrections to the proposed decay function that take into account the causes of variation in the actual data.
In order to obtain knowledge regarding damage mechanisms of building located above surface of the 2016 Kumamoto earthquake fault, the residual deformations of the building were investigated with 3D point cloud data obtained by a laser scanner. The 3D point cloud data contain noise due to measurement error and diffuse reflection. Residual deformations were grasped accurately with method reducing the influence of measurement error by using RANSAC algorism which is one of robust estimations. The validity of the obtained results is also confirmed by comparing other research and evaluating the error.
This study evaluated the multiaxial creep properties and creep rupture life of Super304H using a welded miniature cruciform specimen. The material to be evaluated was used only for the central gauge part of the cruciform specimen, and separately prepared parts were welded to the loading griping part to minimize the size of the evaluated material. Deformation in the central gauge part of the weld-type cruciform specimen was larger at the SUS316 gripping area than at the Super304H gripping area. However, there was no significant effect of the different gripping materials on the creep rupture life under the testing conditions of 973 K and 180 MPa equivalent stress. Under the unequal biaxial tensile condition, the creep strain in the direction of minimum principal stress was significantly smaller than the strain in the direction of maximum principal stress. It is suggested that von Mises equivalent stress is effective for creep rupture life correlation. Although the multiaxial creep rupture lives show a tendency to be slightly longer than the uniaxial creep rupture lives, the equivalent stresses indicate that they can be correlated within a factor of 2.
Front Cover. Antifouling agents with low toxicity are in high demand for sustaining marine industries and the environment. Fifteen isothiocyanates derived from β‐citronellol were synthesized, and their antifouling activities and toxicities were evaluated against the cypris larvae of barnacles. The isothiocyanates with an amide or isocyano group exhibited great potential as effective antifouling agents. They are therefore expected to be useful for further research on the development of environmentally friendly antifouling agents, as reported by Kitano et al. in their research article at 10.1002/cbdv.202200953.
Corrosion hidden under opaque anticorrosion coatings is hazardous for outdoor installation. This type of corrosion can be visualized using radio waves, which are familiar to electrical engineers with field case experience.
While epidemiological data are available for the dose and dose-rate effectiveness factor (DDREF) for human populations, animal models have contributed significantly to providing quantitative data with mechanistic insights. The aim of the current review is to compile both the in vitro experiments with reference to the dose-rate effects of DNA damage and repair, and the animal studies, specific to rodents, with reference to the dose-rate effects of cancer development. In particular, the review focuses especially on the results pertaining to underlying biological mechanisms and discusses their possible involvement in the process of radiation-induced carcinogenesis. Because the concept of adverse outcome pathway (AOP) together with the key events has been considered as a clue to estimate radiation risks at low doses and low dose-rates, the review scrutinized the dose-rate dependency of the key events related to carcinogenesis, which enables us to unify the underlying critical mechanisms to establish a connection between animal experimental studies with human epidemiological studies.
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287 members
Koichi Asano
  • Energy Transformation Research Laboratory
Shin-nosuke Hashida
  • Environmental Science Research Laboratory
Daisuke Tsumune
  • Environmental Research Laboratry
Taku Noda
  • Energy Innovation Center
Masahiro Furuya
  • Nuclear Technology Research Laboratory
Tokyo, Japan