I have a colony of semi-post-apocalyptic survivors who have created a deterrence scenario involving their access to both a nuclear reactor and some body(s) of water.
Ideally, I'd like the water to be the ocean, but I don't think I can justify the amount of work it would take to irradiate an entire ocean. I'm pretty sure it would take more pollution than is feasible to transport. Also, nuclear power plants aren't typically near oceans.
I got this idea from watching Chernobyl, and the body of water which was threatened in Russia was quite large. But I still don't know how large is too large, or if there's a more clever way to go about claiming an area.
In terms of the story: their deterrence scenario is essentially "we can ruin this entire plot of land so don't mess with us." The conflict is between them and a world dominating super power, so I'd really like the plot of land to be as large and long lasting as possible.
EDIT: the super power has no reason to fear the colony, they just want them to die so they can have their land. They own the rest of the world in a sort of Atlas Shrugged gone viral sort of way. They are not reliant on dirty energy (ie oil), and are not religious.
EDIT: Changed "mutual destruction" to "deterrence"