The amount of greenhouse gas emissions mitigation required to prevent the most dramatic climate change scenarios postulated in the 2014 IPCC Synthesis Report is substantial. Prior analyses have examined the potential for nuclear energy to play a role in decarbonizing the energy sector, one of the largest contributors to emissions worldwide. However, advanced, non-light water reactors, while often touted as a viable alternative for development, have languished. Large light water development projects have a repeated history of extended construction timelines, re-work delays, and significant capital risk. With few exceptions, large-scale nuclear projects have demonstrated neither affordability nor economic competitiveness, and are not well suited to nations with smaller energy grids, or to replace fossil generation in the industrial process heat sector. If nuclear power is to play a role in decarbonization, new policy and technical solutions will be needed. In this manuscript, we examine key aspects of past performance across the nuclear enterprise and explore the future potential of nuclear energy worldwide, focusing on policy and technical solutions that may be needed to move nuclear power forward as a part of a low-carbon energy future. We do so first at a high level, examining the history of nuclear power research and development in the United States, the nation that historically has led the way in the development of this generating technology. A significant portion of our analysis is focused on new developments in this technology – advanced non-light water reactors and small modular reactors. We find that while there are promising technical solutions available, improved funding and focus in research and new models of deployment may be needed if nuclear is to play a continuing or future role. We also find that in examining potential new markets for the technology, a continuing focus on institutional readiness is critical.

Around the world, countries are increasingly considering carbon-free energy generation options as the threat of climate change grows. Small modular reactor designs, promising such carbon-free energy generation, are thriving worldwide with novel and innovative technologies that improve safety as well as economic performance. Canada is also considering small modular reactors (SMRs) as a means of achieving net zero carbon emissions by 2050. Some of these reactor designs utilize pressurized water for cooling and moderator. Reactors with pressurized water have been subjected to steam generator tube ruptures in the past, and a detailed investigation into the possible consequences of such incidents in SMRs should be conducted. In this research, a model for one of the newer designs, the NuScale Integrated Small Modular Reactor, was developed with the RELAP5-3D code for assessing safety related transients. The NuScale Small Modular Reactor incorporates helical coil steam generators within its reactor pressure vessel, which are more efficient in terms of heat transfer than the U-tube steam generators that are widely used in nuclear reactors. In the first part of the research, a detailed model is created and used to obtain steady state conditions with parameters collected from NuScale’s Final Safety Analysis Report (FSAR). The Steam Generator Tube Rupture event is analyzed in the second part of the work. Slight differences in the broken and intact steam generator pressures as well as decay heat removal system flow rates are seen in the comparison of reference values and calculated results. Among the reasons for those differences could be that the correlations used by the RELAP5-3D code for heat transfer coefficient and pressure drop in the helical coil steam generators are different than those of the NuScale proprietary code NRELAP5, with which the analyses have been performed in the FSAR. Also, post-dryout heat transfer at the exit of helical coil steam generators and evaporator sections could cause differences in the outlet conditions of the steam, resulting in different mass flow rates as well. The final section of the research simulates a comparable but more severe tube rupture incident without the availability of decay heat removal systems in order to assess the reactor’s emergency core cooling system reaction. Passive decay heat removal systems are crucial components for removing heat after reactor shutdown through heat exchangers that are submerged in the reactor pool and connected to steam generators by a closed loop. The containment pressures, the containment wall temperatures, and the peak fuel clad temperatures are considered to be the key design constraints that must be observed. Future work on this subject could include modifying the source code, adding specific correlations for helical coil steam generators, and comparing the results, as well as quantifying uncertainties in the SGTR event. Main parameters in the quantification of uncertainties would be reactor power, single phase and two-phase discharge coefficients from the break, trip signals and delays as well as break size and location. / Thesis / Master of Applied Science (MASc)

This report conducts an in-depth examination of the potential for Small Modular Reactor (SMR)-based hydrogen production in Sweden's emerging nuclear market. Aligned with Sweden's ambitious targets of achieving carbon dioxide neutrality by 2045 and transitioning its steel and industry sectors to fossil-free production by 2035, the report explores the unique value proposition that a focal company can offer. This strategic positioning centres on supplying large volumes of hydrogen to the steel and iron industry while ensuring reliability and stability in production. To safeguard its competitive edge, the focal company leverages lock-in effects, capitalizing on the geographical placement of its facility and the establishment of a long-term Hydrogen Purchase Agreement (HPA) with its customers. Key findings highlight the levelized cost of hydrogen (LCOH) of 3.46 €/kg to 8.27 €/kg in the SMR-based production process. It reveals that transitioning from natural gas-based hydrogen is cost-intensive, resulting in a green premium (GP) ranging from 257% to 1134%. However, when compared to renewable energy sources and other fossil-free competitors, the LCOH proves competitive in every case except for HYBRIT’s, which is relying on low grid electricity prices in Sweden. When stipulating a HPA with a customer and using a real discount rate (RDR) of 3 % and a profit margin (PM) of 50 % over a 20-year analysis period, the project can reach a net present value (NPV) of 920 MEUR and discounted payback time (DPB) of 12 years in the most profitable case. In a more realistic scenario with a RDR of 7% and a PM of 30% the NPV becomes 497 MEUR with a DPB of 13 years. The economic feasibility is in general given at other, less favourable terms as well. This proves that the focal company’s business strategy is feasible. In conclusion, this report offers a strategic pathway for SMR-based hydrogen production in Sweden's evolving nuclear landscape. While feasibility is theoretically established, the presence of uncertainties cannot be overlooked. The report provides valuable insights for influential stakeholders in their decision-making processes and recognizes the substantial challenges and promising opportunities that lie ahead. / Denna rapport genomför en djupgående undersökning av potentialen för vätgasproduktion baserad på små modulära reaktorer (SMR) på den framväxande kärnkraftsmarknaden i Sverige. I linje med Sveriges ambitiösa mål att uppnå koldioxidneutralitet år 2045 och övergå sina stål- och industrisektorer till fossilfri produktion år 2035 utforskar rapporten det unika värdeerbjudandet som ett fokalföretag kan erbjuda. Denna strategiska positionering fokuserar på att leverera stora volymer av vätgas till stål- och järnindustrin samtidigt som tillförlitlighet och stabilitet i produktionen säkerställs. För att skydda sin konkurrensfördel utnyttjar det fokala företaget inlåsningseffekter genom att dra nytta av den geografiska placeringen av sin anläggning och etableringen av ett långsiktigt avtal om vätgasköp (HPA) med sina kunder. De viktigaste resultaten lyfter fram den utjämnade kostnaden för vätgas (LCOH) från 3.46 €/kg till 8.27 €/kg i produktionsprocessen baserad på SMR. Det visar att övergången från naturgasbaserad vätgas är kostnadsintensiv och resulterar i en grön premie (GP) som varierar från 257% till 1134%. Men när den jämförs med förnybara energikällor och andra fossilfria konkurrenter visar LCOH sig vara konkurrenskraftig i varje fall förutom i HYBRIT’s fall, vilket är beroende av låga elnätspriser i Sverige. När ett HPA stipuleras med kunden och man använder en verklig diskonteringsränta (RDR) på 3 % och en vinstmarginal (PM) på 50 % över en 20-års analysperiod, kan projektet nå ett nettonuvärde (NPV) på 920 MEUR och en diskonterad återbetalningstid (DPB) på 12 år i det mest lönsamma fallet. I ett mer realistiskt scenario med en RDR på 7 % och en PM på 30 % blir NPV 497 MEUR med en DPB på 13 år. Den ekonomiska genomförbarheten ges i allmänhet även på andra mindre förmånliga villkor. Det bevisar att det fokala företagets affärsstrategi är genomförbar. Sammanfattningsvis erbjuder denna rapport en strategisk väg för vätgasproduktion baserad på SMR i det svenska utvecklande kärnkraftslandskapet. Även om genomförbarheten teoretiskt är fastställd kan närvaron av osäkerheter inte bortses från. Rapporten ger värdefulla insikter för inflytelserika intressenter i deras beslutsprocesser och erkänner de betydande utmaningar och lovande möjligheter som ligger framöver.