When you reveal a spoiler the black rectangles go away and it then renders the text in white, but on a white background (light coloured theme) The text renders is exactly the same colour as the background and so you can not see it unless you highlight the post, this renders the background of the post as light grey and there is just about enough contrast difference to now read the text.
When spoiler text is revealed it should render in the same colour as normal text. I'm not sure why it's white.
See images below for demonstration.
You're thinking of fusion bombs. They're absolutely not zero radiation they just don't release as much as you would expect given these size of the explosion. But they absolutely do release radiation.
Much of the destruction from fusion bombs comes from the implosion rather than the explosion. Not that the initial explosion isn't highly also destructive. In an airbus situation it basically picks things off the ground and flings them into the air that several times the speed of sound. Any oil rig that is already in place is going to get violently ripped out of the ground along with a lot of the underground piping. At the very least that is going to cause a massive leak and probably catch fire. The last time a gas fire like that happened the Russians actually had to use a nuke to put it out.