There has been a prototype built of this reactor. If you look at the advanced reactors, many prototypes have been built and operated. The interesting thing about this technology comes from asking why these technologies were never brought to market.
There were some very good reasons when you look back 30, 40, or 25 years ago. If you look in the context of market needs 25 years ago, yes, it's clear why they didn't progress to market. It was because the current product was good enough, and we didn't have an existential threat from climate change. When you now revisit that decision in the context of today's market needs, in the context of where the current product is, it is too expensive and too complex to build. That's the principal problem with conventional nuclear: it's become too complicated, too risky, and too costly to build. When you revisit those decisions, you realize that the better product is advanced nuclear, for which there are many different types of designs and technologies.
These technologies have been proven at the national lab level. The commercial opportunity is to recognize that their commercial time has arrived. That's the interesting insight.