A new energy learning support system for higher education was the object of this experiment. The aim of this learning support system is to support students within an integrative study environment in which various personal skills and general knowledge on energy related issues are to be developed. The main goals of this learning tool for the students are to stimulate their interest and creativity, to enhance awareness, to increase capability of researching on the subject and to improved problem-solving skills on energy related issues. The salient feature of this learning support system is that it is used for group learning by which each learner can develop the ability to reflect on the subject through mutual discussion. Moreover, in order to keep the attention of the students on the topic and provide them with a better assimilation of the curriculum, a personified agent is used as a cooperative associate who assists learners through natural communication, using voice conversation function in Japanese language. Then, the subject experiment has been conducted. Also, means of effective energy education are discussed in this research. As a conclusion, this learning support system is proven to be effective and the use of it for energy education is recommended.
A stress relaxation measurement method has been developed by using C-ring specimens, and a specimen size effect has been evaluated taking radiation-induced stress relaxation into consideration. C-ring specimens were stressed by forcing a wedge in the gap. Giving an appropriate eccentric configuration in the half of the ring opposite the gap, the stress gradient along the circumference was eliminated in the section and the stress level could be varied by changing the gap spacing. The validity of the C-ring test method was confirmed by thermally stress relaxation experiments at annealing temperatures from 300 to 600°C for 1min to 200h in carbon steel: considerable stress relaxation could be measured for all levels of applied stress even at relatively low annealing temperatures. The relaxation results obtained from the C-ring test were in good agreement with those from a uniaxial tensile stress relaxation test. The smaller C-ring specimen with about 40mm diameter, which is required for radiation-induced stress relaxation test, also showed adequate accuracy on stress relaxation at 600 to 830°C in stainless steel, compared with the large size C-ring specimen test.
The Nuclear Waste Management Organization of Japan (NUMO) is implementing a high-level radioactive waste (HLW)disposal project. One of the most difficult challenges facing the project is selecting a site for the disposal facility. The experiences of the HLW-related projects in Japan and abroad suggest that a framework of site selection should be developed based on careful consideration of social factors. The present study examines a strategy to improve the current framework of site selection. It focuses on the public perception of justice, both procedural and distributional. An analysis in terms of procedural justice, which includes transparency, neutrality/objectivity, and the involvement of local communities, shows that the following five factors are essential: (1) a well-defined phased approach for site evaluation, (2) a robust base for applying site evaluation criteria, (3) review of site evaluation by an entity which is sufficiently independent from interests in promoting the project, (4) exclusion of unsuitable areas through a substantial survey of existing geological data, and (5) shared decision making to adapt the site evaluation approach to public concerns. A discussion of distributional justice concludes that NUMO and the government should make substantial efforts to mitigate the risk perceived by local communities in addition to making efforts aimed at compensation and incentive.
Currently, a reactor core for boiling water reactors (BWRs) which improves a conversion ratio to about 1 is being examined. Since the gap between fuel rods must be narrowed to about 1.3mm, it is expected that the fuel cooling performance would deteriorate. However, there are few thermal-hydraulic measurement data for tight lattice rod bundle. Therefore, the thermal-hydraulic tests using the tight lattice bundle were carried out under the BWR operating condition. As a result, the boiling transition behavior was similar to the liquid film dryout, which is the boiling transition mechanism of the conventional BWR fuel bundle. Moreover, the tendency of thermal-hydraulic performance for the flow condition parameters was the same as for the conventional BWR. Next, the applicability of the correlation developed by Arai et al. was examined to evaluate the critical power. These test data could be predicted accurately by Arai's correlation. Arai's correlation is based on the measurement data obtained by LeTouneau et al. Thus, Arai's correlation is expected to have wide applicability for various tight lattice bundles.
The conventional reactor internal pumps (RIPs) in the ABWR have an inertia moment coming from the shafts and Motor-Generator sets, enabling the RIPs to continue running for a few seconds, when a trip of all RIPs event occurs. It is possible to simplify the RIPs' power supply system without affecting the core flow supply when the above event occurs by eliminating M-G sets, if the rotating inertia is increased. This inertia increase due to an additional flywheel, which leads to gains in weight and length, requires the larger diameter nozzle with the thicker sleeve. However, too large a nozzle diameter may change the hydraulic performance. In authors' previous study, the optimum nozzle diameter (492mm) was selected through 1/5-scale test. In this study, the 492mm nozzle and the inertia-increased RIP were verified through the full-scale tests. The rotating inertia time constant on coastdown characteristics (behavior of the RIP speed in the event of power loss) for the inertia-increased RIP doubled compared with the current RIP. The casing and the shaft vibration were also confirmed to satisfy the design criteria. Moreover, hydraulic performance and heat increase in the motor casing due to the flywheel were evaluated. The inertia increased RIP with the 492mm nozzle maintained good performance.
It is recognized that social and political perspectives are crucial for decision-making of the high-level radioactive waste (HLW) disposal. Understanding and addressing value judgments involved in decision-making becomes the essential part of the efforts to gain public acceptance of HLW disposal. This study discusses policy issues raised by the change of the concept of intergenerational equity, which is one of the most important principles for the value judgments concerning HLW disposal. This principle is widening its scope: in addition to the obligation of the current generation to minimize risk, cost and burden for the future generation, the obligation to maintain equal opportunities for the future generation is recently emphasized. Serious consideration of retrievability is regarded as a symbol of this change. This study focuses on the implications of the above change in the strategy of disposal technology development. It points out that comprehensive consideration including the viewpoints of ensuring retrievability and gaining confidence in robustness of the disposal system is required to optimize the methodology of HLW disposal and that the optimized methodology should be evaluated from the social perspective to ensure high level public consensus. Moreover, this study makes suggestions on development of technology elements to provide a firm basis for optimization.