It's over 20 years since I finished my degree, and I've never worked in the industry, but I spent sufficient hours poring over the ISO standard document for pre

It's over 20 years since I finished my degree, and I've never worked in the industry, but I spent sufficient hours poring over the ISO standard document for pressure vessels as part of my final year project that I can still remember the sorts of things it covers. Effectively, they test things to destruction, then publish minimum requirements. So if you want to pressurise your reactor vessel to reactor vessel to 30 atmospheres, you can pretty much look up a table that'll tell you precisely how thick the reactor walls need to be for each of the commonly used materials. If you want to use something uncommon, then you need to pay somebody to test it. If it fails in a catastrophic fashion, you can expect to be asked to show that you did your due diligence, and there are extenuating circumstances a reasonable engineer could not have been expected to foresee and plan for. Or that you did foresee it, and somebody else chose to accept the (clearly defined) risk.