Catálogo de publicaciones - libros

After the severe accident in Fukushima Daiichi Nuclear Power Station, safety improvement and enhancement have been installed. In midterm and long term, continuous efforts to improve and enhance safety are required, and technical basis and fundamentals are needed to achieve them.

Probabilistic Risk Assessment for seismic event (seismic PRA) is an effective measure to consider the countermeasures and improvement plans to secure the further safety of nuclear power plants regarding to seismic risk for the earthquake exceeding the design basis earthquake ground motion. However, the application of seismic PRA has not been utilized sufficiently so far. One of the reasons is that there is not enough agreement among stakeholders regarding to the evaluation methodology and consideration of uncertainty for decision-making.

This study proposes the mathematic framework to treat the uncertainty properly related to the evaluation of core damage frequency (CDF) induced by earthquake, the methodology to evaluate the fragility utilizing expert knowledge, the probabilistic model to cope with the aleatory uncertainty as well as the development of analysing code including these considerations for the improvement of the reliability of the methodology and enhancement of utilization of the products of seismic PRA.

This paper presents current status and some results from scoping calculations.

It was found that many deficits of nuclear risk governance in Japan before and after the Fukushima accident. Not only were they created and embedded before the Fukushima disaster, but it has been remained or even worsened even after many accident reports were published and pointed out many problems and suggested ideas to remedy them.

In this paper, the author would analyze such remained problems found in the postaccident “on-site management” policy and measures, taking the case of contaminated water management at the Fukushima Daiichi Nuclear Power Plant. Firstly, the development of contaminated water management policy measures and institutional framework would be described in a chronological manner, which is one of the most typical and difficult tasks of “on-site management.” Then, the cause of their failure trajectory would be analyzed by using a sociological concept “structural disaster” to understand the malfunctions which are continuously repeated not by identifiable particular factors but by inappropriate design of the socio-technical interface. This conceptual standpoint would suggest that the problems are not solvable by each of technical improvement, superficial institutional reform, nor prosecution and punishment of relevant individuals or organizations but by the redesign of that interface as a whole. Finally, based on this perspective, the author would discuss the ideas to remedy the deficits that might lead to further continuation of “structural disaster” in nuclear field.

A community-based risk communication approach for risk and risk-related factors regarding low-dose radiation has been started in 2013. In this approach, three groups that consist of local citizens, health nurse, midwife and nutritionist, and media reporters have been coordinated, and they discuss and examine a guidebook of health effects on low-dose radiation prepared by experts. Then they will revise the contents and expressions of the guidebook under expert’s support by themselves. An improved guidebook implementing stakeholders’ input will be expected through this process. In parallel to the community-based risk communication, an opinion survey has been conducted for the inhabitants of Tsuruga City in the Fukui prefecture to obtain people’s cognition about ionizing radiation and risk on health effects. The inhabitants of about 43 % show strong anxiety for radiation. They also show strong requirement for the risk criteria that should be specified by government/specialists. The current status and progress of the community-based risk communication approach are discussed, and a necessity of risk education regarding trans-science problem is presented.