Coal-to-nuclear (C2N) repowering, which replaces coal-fired units with nuclear reactors while reusing existing site infrastructure, offers a unique solution to the challenge of large-scale coal retirement in China’s low-carbon transition. However, the availability of suitable sites, which fundamentally determines C2N potential, remains insufficiently quantified at high spatial resolution, and the key factors constraining siting suitability remain poorly understood. This study develops a unit-level C2N siting model integrating a database of coal-fired units with multi-source geospatial constraint layers at 1-km resolution. A four-dimensional framework encompassing geological stability, cooling water availability, population distribution, and unit capacity is applied to screen candidate sites for large reactors (LRs) and small modular reactors (SMRs). Results show that 44 units (30.80 GW) pass the geospatial screening criteria for LRs, while 1,657 units (718.36 GW) pass the criteria for SMRs in China, indicating SMRs may represent a potentially suitable option under geospatial constraints. Shapley-value decomposition quantitatively attributes each constraint’s contribution to site exclusion, identifying population as the dominant factor. Plant capacity is the second-largest contributor for LRs, whereas cooling water and geological conditions are the next most influential factors for SMRs. Regional Shapley analysis reveals pronounced spatial heterogeneity in binding constraints across China’s seven power regions. Sensitivity analyses across alternative population regulatory frameworks and cooling-water distance thresholds confirm the robustness of SMR siting advantages while showing that shifts in these standards can substantially reshape regional technology mix and siting patterns. These findings provide high-precision spatial inputs for power system planning and differentiated policy design toward decarbonization of coal-fired power plants in China.

Advancing power sector decarbonization represents one of the most direct and effective measures in carbon emissions reductions and climate change mitigation. Replacing to-be-retired coal fired power generation with nuclear ones, also known as coal-to-nuclear conversion (C2N), has been recently discussed as an economical technology pathway in this regard. The provincial development potential of C2N in China, which may vary by natural conditions and the establishment of future standards, remains to be determined. This study analyzed this potential using a multistep process. This study newly established a comprehensive database of China's coal-fired power plants and designed an evaluation system for C2N with constraints from dimensions including earthquake geology, population density, and water availability. This is followed by a multi-scenario analysis of the potential, based on China's actual conditions and different C2N approaches. The results show that: C2N is a feasible pathway in China's low-carbon transition, with population density being the primary influencing factor on the total potential available. Under the considered constraints, the site potentials for conversion into Large Reactors (LRs) and Small Modular Reactors (SMRs) is approximately 56 and 979 GW, respectively, if China could expand inland nuclear deployment. With the continuation of current policy and inland nuclear development constrained, there would be no potential remaining for LRs, while potentials for SMRs would reduce by 94% to 55 GW, illustrating the decisive impact of inland nuclear policy on China's prospects of C2N. Further, under the two conversion approaches of complete replacement and partial replacement, the potential sites for LRs would be 6 and 10 GW, respectively, while the potential sites for SMRs would be 502 and 244 GW, respectively, suggesting major development potential of SMRs in China if C2N is allowed. This study is valuable for the early quantification of the provincial C2N development potential in China.