While 500C is a lot when compared to the average process in a kitchen, on an industrial scale it's not really even all that impressive. Any steel mill deals with temperatures over twice as high. Never mind that a steel mill does a lot of moving around of steel in crucibles and such which is the main danger, which I don't reckon would be required for this process. The local trash incineration facility gets hot enough to melt copper, which is over twice as hot as this molten salt process.

Heck, the inside of your average wood stove gets up to these temperatures.

Painting 500C as some sort of very high temperature that's hard and dangerous to contain isn't quite fair, seeing as there are myriad industrial processes that are generally considered safe that run at much much higher temperatures.