Discussion
Conclusions
The question is whether it is really worth coupling an HTE system to an HTGR and achieving such a low theoretical gain of efficiency:
- Hydrogen has to be kept separated from the nuclear plant to avoid hydrogen explosion hazard. This will be on the expense of losses in the heat exchanger, which will lower the global efficiency of the system, and of increasing investment cost for security reasons. It has been suggested to increase the number of water recirculating with hydrogen to avoid hydrogen explosion; but doing so will reduce the final efficiency of the process because the heat of vaporization of water can not fully be recovered.
- HTE systems are supposed to be very fragile, especially under thermomechanical cycling conditions. Repeated maintenance of HTGR systems will lower their lifetime and their availability.
- Allothermal instead of autothermal operation of HTE will increase the number of cells required, therefore directly impacting the already high investment cost.