My understanding is that because of the relatively low reactor...

My understanding is that because of the relatively low reactor temperature (800-900 C) they believed that they could get greater longevity from a high temperature alloy steel rather than a conventional refractory which requires periodic replacement. The difficulty in fabrication of the Chinese reactor and it subsequent failure led them back to a more conventional refractory solution which we are still to receive. I believe that this is testament to Hazer's willingness to be bold enough to try a world first state of the art solution, yet also being prepared to change tack. All part of the design process, which takes time.