NRT website has current updates
 

Don't know how long they'll keep doing this but folks travelling to/via NRT might find http://www.narita-airport.jp/en/ useful. They even publish sampled radiation levels based on measuring devices they have around the airport.

I'll be doing SEA-NRT-PVG this Sunday (coach, yuk!). Not expecting anything out of the ordinary though not looking forward to the TPAC segment in coach.