Is there any way to stop the radiation?
Either wear the Radiation Hazard Suit or build it further away from your Stuff. Those are the only ways, sorry.
Any plan to add some blocks made by lead and other materials which are able to block the radiation?
That is very unlikely. GT6 is finished, Greg will only do some bugfixes now and focus on his own game. It’s however very likely that some updated from other people or an unofficial version, like with GT5, will add this feature, but that will take some time.
I myself plan to maybe expand the reactors a bit (neutron sensor, critical fuels, moderation, breeding), but can’t promise if or when I will find the motivation to do so.
Remember, even though GT6 is ‘done’, Greg will still work with and accept PR’s if they fit well. And from my understanding he’s pretty open to such things.
Yes I am indeed. I may be busy playing Factorio right now (which is the sole reason for lack of progress on my game right now, though I already get the feeling that I’m gonna be done with Factorio soon. XD), but I can always look at PRs and stuff. ^^