Building nuclear fallout shelter?

Hi all, im bored and with world war 3 looming i want to build a nuclear fallout shelter in my back garden, but obviously i dont want to advertise the fact i have a shelter in my garden cos when theres a strike i dont want all the neighbours heading my way hoping i can accomodate them..of course this is even if we survive an attack.. also how would i go about getting planning permission for one? problem is i live in a council estate and will have trouble building one in secret.
Answer
A septic tank is about the right size?http://www.bombshelters.com/index.php