Abstract
The scientific and practitioner literature suggests that building large and complex nuclear reactors is frequently associated with major cost increases that undermine project completion and discourage investors. Small modular reactors (SMRs) target a distinct market segment by shifting from traditional economies of scale to economies achieved through multiple units, typically up to 300 MWe. However, modularisation, design simplification and co-siting economies—key SMR features—are often insufficiently represented by conventional topdown cost estimation models. These models are generally calibrated on large pressurised water reactors (PWRs) and tend to overestimate SMR costs by emphasising the loss oi economies of scale. To address this limitation, this paper introduces a bottom-up cost estimation approach that explicitly incorporates SMR-specific design and construction characteristics. The method uses itemised cost equations for each cost item defined by the Energy Economic Data Base (EEDB) Code of Accounts developed by the US Department of Energy. The resulting model has an estimated accuracy of -30%/+50% and is applied to two SMR concepts: IRIS (335 MWe per unit) and NuScale (77 MWe per unit). Using a large PWR as reference (100% overnight capital cost, OCC), the Nth-of-a-kind (NOAK) twin-unit IRIS plant is estimated at 94% OCC, while a 12-module NuScale plant is estimated at 105% OCC. In contrast, topdown scaling yields 163% OCC for IRIS and 294% OCC for NuScale. The results suggest that NOAK SMRs can be cost-competitive with large NOAK PWRs when assessed through bottom-up modelling.
Highlights
Bottom-up cost model for SMRs capital cost estimation.
Main cost items validated through interviews with Italian manufacturers.
Focus on unique challenges and advantages of SMRs compared with larger reactors.
Valuable insights for the discourse on small nuclear power plant construction economics