**5. Conclusions**

This analysis explored the economics of dispatching a nuclear-IS cogeneration unit. The results demonstrate the economic potential of such a system when compared to only selling electricity. These results highly depend on input assumptions, specifically the magnitude and distribution of electricity prices. Historical input electricity price data model runs show that a 98.1 JPY/m3 LCOH was needed to break even under the specified conditions. Model runs with synthetically produced electricity price data for stochastic optimization found that an LCOH of 67.5 JPY/m3 was required.

The LCOH in this report should not be taken as a final value for the HTTR-GT/H2's profitability, but as an exploration of the impacts of input assumptions on the final answer. Special care should be taken in this type of dispatch analysis to produce a host of meaningful electricity price time histories that represent possibilities for the evaluation years. In this regard, the FARMA approach shows great potential.

This study also serves as another indicator that dispatching hydrogen and electricity could be more economically advantageous than just selling electricity under the right conditions. Much of the nuclear hydrogen production and dispatch work focuses on light water reactors and U.S. electricity markets while focusing on electrolysis hydrogen production technology. This study performs the economic dispatch on a unique reactor, hydrogen production system, and electricity market and shows the breakeven price of hydrogen. Performing this analysis at different locations and with different technologies is important for understanding the economic competitiveness of producing hydrogen from nuclear energy.

Efforts to further this research could include running a larger stochastic optimization case aimed at optimizing the size of the IS unit on a commercial reactor or at optimizing different sensitivities (e.g., capital cost).

**Author Contributions:** Conceptualization, J.R. and C.R.; methodology, J.R. and C.R.; software, J.R.; validation, J.R. and C.R.; formal analysis, J.R.; investigation, J.R.; resources, C.R.; data curation, J.R.; writing—original draft preparation, J.R.; writing—review and editing, J.R., C.R., N.A., H.S. and X.L.Y.; visualization, J.R.; supervision, C.R., H.S. and N.A.; project administration, C.R., H.S. and N.A.; funding acquisition, C.R., H.S., X.L.Y. All authors have read and agreed to the published version of the manuscript.

**Funding:** Prepared for the U.S. Department of Energy Office of Nuclear Energy under DOE Idaho Operations Office Contract DE-AC07-05ID14517.

**Data Availability Statement:** Restrictions apply to the availability of these data. The data were obtained from the Japan Atomic Energy Agency and are available from the authors with the permission of JAEA and INL.

**Acknowledgments:** This manuscript has been authored by a contractor of the US Government for the U.S. Department of Energy, Office of Nuclear Energy (DOE-NE), under DOE-NE Idaho Operations Office contract DEAC0705ID14517.

**Conflicts of Interest:** The authors declare no conflict of interest.

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