南相馬市長のSOS on YouTube
参考ページ:Nuclear and radiation safety:
Guidance for emergency response
Sheltering means staying in buildings to reduce exposure to airborne contamination and surface deposits, and closing doors and windows and turning off ventilation systems to reduce inhalation of radioactive material from outside air. Sheltering can also facilitate staging for evacuation and the prophylactic use of iodine. Because of the small penalties, sheltering may be justified at low dose levels. However, its effectiveness decreases rapidly with time for most structures (typically reducing doses to airborne particulates by a factor of two or three in a few hours) and is low for lightweight structures or those with high air exchange rates. Further, there is a limit to the time that populations can remain indoors without undesirable complications.
The generic intervention level for sheltering is 10 mSv. This value was selected based on the maximum anticipated period of sheltering (2 days). Sheltering may be advised at lower levels for shorter periods or to facilitate other protective actions.
Sheltering can be effective if the exposure is of short duration and buildings are of dense structure and well sealed, as in some northern countries. In many warm countries, however, most houses are made of light materials, and people cannot stay indoors in sealed houses for long periods. These factors must be considered when choosing between protective action through sheltering versus evacuation.