April 9th, 2011 – Summary of Naval Reactors “Warm” and “Hot” Zones around Fukushima Daiichi
[link to enformable.com]

[snip]

The military has established a radiological warm zone and hot zone around the Fukushima Daiichi nuclear station. The hot zone extends out to 25 miles from the plant. The warm zone extends out an additional 125 miles from the plant.

One consideration for looking at the possibility of reducing the zone sizes would be to reduce the dosimetry needs for personnel; personnel entering into these zones are required to have dosimetry.