Examining sheltering-in-place operations in radiation protection facilities under compound disaster scenarios: A case study from the 2024 Noto peninsula earthquake

Disasters have a wide range of effects on society. Nuclear disasters require a multifaceted response that considers the direct health effects of radiation exposure and indirect health consequences associated with evacuation. In recent years, the development and evaluation of practical nuclear disaster preparedness measures have become critical challenges for regions hosting nuclear power plants due to the growing risk of increasingly complex natural hazards. This study aimed to clarify the operational challenges of radiation-shielded shelter facilities used for sheltering during disasters by investigating the damage sustained by such facilities in Shika Town, Ishikawa Prefecture, where a seismic intensity of 7 was recorded during the 2024 Noto Peninsula Earthquake. The study was conducted through interviews and analysis of official damage reports by the Cabinet Office, targeting 12 radiation-protective facilities equipped with positive-pressure systems located within the Precautionary Action Zone and the Urgent Protective Action Planning Zone of the Shika Nuclear Power Plant. The results identified two major operational issues: (1) a lack of shared understanding regarding the target pressure differentials for positive-pressure systems and (2) a decline in building airtightness due to structural damage caused by the earthquake. In addition, insufficient sharing of knowledge and operational criteria between administrative authorities and on-site personnel has emerged as a challenge for the practical use of these facilities. These findings underscore the need for standardised criteria for seismic resistance and airtightness that assume the occurrence of compound disasters, as well as the importance of strengthening information-sharing systems during normal times. Furthermore, the study highlights that even within the Precautionary Action Zone, older individuals and persons requiring special care may face difficulties in executing immediate evacuation, potentially making sheltering-in-place the only feasible option. Therefore, it is necessary to reconsider the institutional position of sheltering as a realistic form of evacuation.