When natural disasters hit in Japan, it is customary to report the number of people killed, injured, and/or missing. For smaller-scale disasters, the word for 'missing' is usually 行方不明 yukue fumei 'whereabouts unknown' (lit. 'movement-direction not-clear'). This term for 'missing' seems to imply that rescuers have searched the site of the disaster but failed to find any trace of some of the people they hoped to find there.
But in the widespread aftermath of the Great Tohoku Earthquake and tsunami, the word for 'missing' that now appears in Japanese news broadcasts is 安否不明 anpi fumei 'safety unknown' (lit. 'safe-or-no not-clear'). This term for 'missing' suggests that rescuers have in most cases not yet arrived on the scene or not yet completed their investigations to determine the condition and whereabouts of all the people they hope to find there.
This distinction between a sort of preliminary ('unaccounted for') and postmortem determination of who might be 'missing' has not always made it into the English-language headlines about the multiple disasters affecting so many people in Japan right now.
Speaking of which, the term 原発 genpatsu 'nuclear reactor' was also new to me, despite having lived in Hiroshima, where I early on learned the term 原爆 genbaku 'nuclear explosion', short for 原子爆発 lit. 'primitive-child (= atom) burst-discharge'.
The character 原 is read hara when it occurs in so many native Japanese proper names, where it means 'field, plain, prairie, tundra, moor, wilderness'. The 'wilderness' sense seems primary in the Sino-Japanese usage of 原 gen to mean 'original, primitive, fundamental, raw', as in 原因 gen'in 'root cause', 原色 genshoku 'primary color', 原油 gen'yu 'crude oil', and 原発 genpatsu 'nuclear reactor' (or 'atomic discharge').