Radioactivity:

There are 4 forms of uranium in the game, each with its own radiation range, with the lowest range being on Uranium ore, and the highest range being on Uranium block.

This radiation can be blocked by placing Lead Blocks around it, just like you can do with the sculk sensor. Place a lead block on one of the faces of the Uranium block in question, and it will block all radiation from going in that direction.

Armor:

As you saw in the screenshot, there is an armor set in the mod. It's made of Lead, and a full set of it can be used to block radiation, making you not take damage from any and all Uranium blocks. But this armor is not very strong, with armor levels between iron and copper but more towards the iron side.

Reactors:

As you say in the screenshot that, there was a reactor there. Well, that is not the only reactor that this mod adds, as there also exist portable reactors.

The Reactor Block can be placed down and fuel any furnace, blast furnace, and smoker on top of it, but only when it's running. The reactor requires a boron rod, a boron ingot, and either a Uranium ingot or a Uranium block, and both the ingot and the block last for a long time. AND DO NOT REMOVE THE BORON INGOT UNTIL THE REACTOR SHUTS OFF!

The portable reactors, specifically the portable uranium reactor and the portable uranium block reactor, both can be placed in the fuel slot of the furnace, and that powers the furnace until the reactor runs out of heat, so it will not get used up until it runs out of uranium fuel.

Ingot fuel does not last as long as Block fuel, but ingots are cheaper then blocks so use at your own risk.

Building a reactor requires:

• A core with an exception to the Reactor Block which does not need a pre-made core.
• A boiler.
• A body (of course).
• And specifically for the Reactor Block it requires a Reactor Controls.

Ores:

Uranium, Boron, and Lead can be found in caves in their ore forms, both in stone and deepslate layers, but spawn more in the deepslate layer, and can be mined with an Iron, Diamond, or Netherite pickaxe.

Be careful while you are moving through caves; you might not know when you get close to Uranium ore and get hit with radiation!