"The sudden loss in pressure causes the super-heated water to flash almost entirely to steam, which raises the chamber pressure even more.
I'm starting to think you're just making this stuff up off the top of your head.
As I understand it, normally the fluid is brought up to a high temperature and pressure, just short of the burst pressure. At the same time, a capacitor bank is charged, the dumped into a resistor bank inside the pressure vessel. That sudden charge of energy bursts the disk, and the fluid rushes out.
By the way, I have a hyper-sonic wind tunnel burst disk. I's about 8" X 8", made our of 3/8" SS plate. I occasionally bring it to work and ask the other engineers if they can figure out what it is.