Modelling nuclear power in energy system models – assumptions and methodology

This ETSAP report reviews how nuclear power, both conventional reactors and Small Modular Reactors (SMRs), is currently represented in TIMES energy system models and proposes best modelling practices. Based on a survey of 11 TIMES models and a dedicated workshop among ETSAP members, the report shows considerable variation in how nuclear technologies are modelled, particularly regarding costs, operational flexibility, lifetime extensions, and co-generation options.

The findings highlight that modelling results for nuclear power are highly sensitive to assumptions about investment costs and the surrounding energy system context. While most models include new investments in conventional nuclear power and SMRs endogenously, a limited number of the ETSAP participants capture detailed operational constraints, fuel cycle effects, or material and supply chain limitations. Significant uncertainty remains, especially for SMRs, due to heterogeneous technologies, early-stage cost estimates, and policy and regulatory risks.

The involved ETSAP members recommend that nuclear power modelling in TIMES should clearly reflect uncertainty in investment costs (for example by using ranges and sensitivity analyses), account for the diversity of SMR technologies and apply assumptions consistently across all electricity generation technologies to avoid bias.