Description: I've checked a couple of pages in the suggestion forums, but I've found nothing, and i don't know whether this is planned or not, so here goes:
Radioactivity. Right now, you can swim in uranium or get close to a fully functional nuclear reactor without even a itch, and i was thinking if that couldnt change. At first radioactivity would start having simple effects, like miner fatigue, weakness, e.t.c, evolving to heavier symptoms with excessive exposure like blindness, combat weakness. At extreme levels it would start subtracting hp from the player/mob.
Things like uranium cells or ores wouldnt have much of a effect, but a full-fledged nuclear reactor could kill in a few minutes.
A nuclear explosion or a meltdown would leave fallout in a large area.
To protect yourself there are several methods. To contain things like uranium ore, a small box (radioactive container?) wich worked sort of like the toolbox, but would only keep uranium cells, ores and other alike. To protect yorself from environmental radioactivity like a nuclear reactor, you would need a HazMat suit, or a NBC suit (higher combat resistance), but you need the full set to protect yourself. The hazmat breaks very easily under combat, unlike the NBC.
Every block has a "radioactivity resistance" value, wich determines wheter the block can or not allow radioactivity trough (hiding in a dirt shelter wouldnt be the best vs a nuclear fallout. There could be a "fallout shelter" block, with a high radioactivity resistance, but few explosion resistance (you still need reinforced stone to survive a nuclear attack.
To detect the radioactivity level, you could use a Geiger counter, wich would make those "sounds", the faster= more radioactivity, showing a screen where you would see if the radiactivity levels are too high or low enough
I haven't thought much about this, but the container should be made from a derivation of refined iron and maybe coal dust. The Hazmat and the NBC, well, im clueless . The geigher counter would involve copper, iron and redstone. and the fallout shelter could involve construction foam and stone/ gravel/ reinforced stone. Ill leave the dev team to decide.