Ok so I recently watched a video that went into some of this, and I had know idea how crazy some of these nuclear fuels are in terms of physical requirements.

Ok so I recently watched a video that went into some of this, and I had know idea how crazy some of these nuclear fuels are in terms of physical requirements. If I recall the video correctly, solid metal oxide fuel produces offgas at a 50:1 ratio, while being insanely dense. This produces pretty insane internal pressures if the goal of the fuel design is to keep everything contained. Like strong enough to eventually cause mechanical failure of the fuel. I think there's a lot of really difficult constraints intersecting in these fuel assembly designs, and something that seems obviously simple probably isn't.