The FACTS are here;
http://eq.wide.ad.jp/files_en/110328...ty_1900_en.pdf
They are updated regularly and there is other information and the latest radiation levels by prefecture here;
Important Information from Japanese Government
Go down to "All Prefectures" to get the English language version and be aware that Narita airport is in Chiba prefecture.
You will find current radiation levels, whilst slightly elevated, (0.077 microsieverts per hour) are still much lower than many places in the world have each day every day and well within exposure limits for the year if you stayed there full time.
So if JQ crews are refusing to fly or overnight Narita then sack them; they are not behaving rationally at all. The actual flight itself each way will expose them to radiation equivalent to many days stopover in Narita.