Calvert Cliffs Nuclear reactor approx 90 km from Takoma Park

Total of Seven Japanese Reactors Now Face Coolant Problems, Core Damage Possible at Two  http://bit.ly/feI8wk 

None of the Calvert Cliffs reactors are of the same design so whew!
http://on.msnbc.com/g2v0tv

Calvert Cliffs reactors are 90 km from Takoma Park: way outside the evacuation zone of 20 km used in Japan but still it causes some concern. How close is enough?