EPZ（防災対策を重点的に充実すべき地域の範囲）の再検討 ＜４＞

風向き・原子炉の状態によって時々刻々と変化する放射性物質の拡散を考慮しながら、どこに住んでいる人間が、どのようなルートでどこへより安全に避難できるのか、またその指示をどのように出していくのか。参考までにアメリカ合衆国原子力規制委員会（NRC）がEPZについて簡潔に示したものを引用します。

"Emergency Planning Zones

For planning purposes, the NRC defines two emergency planning zones (EPZs) around each nuclear power plant. The exact size and configuration of the zones vary from plant to plant due to local emergency response needs and capabilities, population, land characteristics, access routes, and jurisdictional boundaries."

と前置きしたうえで１０マイル圏内と５０マイル圏内に分けて説明しています。

"The two types of EPZs are:

The plume exposure pathway EPZ extends about 10 miles in radius around a plant. Its primary concern is the exposure of the public to, and the inhalation of, airborne radioactive contamination.

The ingestion pathway EPZ extends about 50 miles in radius around a plant. Its primary concern is the ingestion of food and liquid that is contaminated by radioactivity."

さらに避難のあり方に関連して放射性物質の放出と風向きの関係についても以下の言及があります。

"Evacuation does not always call for completely emptying the 10-mile zone around a nuclear power plant. In most cases, the release of radioactive material from a plant during a major incident would move with the wind, not in all directions surrounding the plant. The release would also expand and become less concentrated as it travels away from a plant. Therefore, evacuations should be mapped to anticipate the path of the release. Generally as a minimum, in the event of a General Emergency, a two-mile ring around the plant is evacuated, along with people living in the 5-mile zone directly downwind and slightly to either side of the projected path of the release. This “keyhole” pattern (Figure 1) helps account for potential wind shifts and fluctuations in the release path (Figure 2). Evacuation beyond 5 miles is assessed as the accident progresses. Also in response to a General Emergency, people living in the remainder of the 10-mile zone will most likely be advised to go indoors to monitor Emergency Alert System broadcasts. "

"Backgrounder on Emergency Preparedness at Nuclear Power Plants", Nuclear Regulatory Commission (NRC), 2009.
http://www.nrc.gov/reading-rm/doc-collections/fact-sheets/emerg-plan-prep-nuc-power-bg.html
＊上記で言及されている図（Figure 1, 2）は、このNRCのページ下部に掲載されています。また"Emergency Alert System"は、米国の緊急警報放送のことです。

＜資料＞
・独シュピーゲル誌（電子版）の記事（２０１１年３月１５日付）に掲載されたオーストリア気象地球力学中央研究所（ZAMG）のモデル計算値。
２０１１年３月１２日−１７日間の放射能雲の大気中拡散シュミレーションです（CG動画）。
http://www.spiegel.de/wissenschaft/natur/bild-750835-191816.html

・「IAEAからの要請と当庁が作成した資料」（気象庁）
２０１１年３月１１日〜５月２３日＜計算値＞
http://www.jma.go.jp/jma/kokusai/eer_list.html

・「緊急時迅速放射能影響予測ネットワークシステム（ＳＰＥＥＤＩ）の計算結果について」（原子力安全・保安院）
２０１１年３月１１日〜＜計算値＞
http://www.nisa.meti.go.jp/earthquake/speedi/speedi_index.html