Multiple nuclear power plants investment scenarios: Economy of Multiples and Economy of Scale impact on different plant sizes

“Deliberately small” nuclear reactors are making their way on the market, not as a mere shift backwards to the small scale of first commercial reactors, but as concepts designed to foster modularization, simplification and serial production. They are proposed by manufacturers worldwide (SMART, 4S, SSTAR, mPower, Nuscale, etc.) and are also intended to address developed electricity markets. The idea of an economic attractiveness of Small and Medium sized Reactors (SMR) is counterintuitive, due to the loss of Economy of Scale on a capital intensive investment. Nevertheless a broader understanding of capital costs drivers has shaped a new concept of Economy of Multiples, that applies on multiple NPP deployment. It relies on learning accumulation to mitigate construction costs of later NPP units; design modularization to exploit the benefits of “serial” production; co-siting economies to decrease the incidence of fixed and site-related costs. We assume that smaller NPP size fosters design modularization and simplifications, with related cost savings. While the effect of modularization on construction costs has been modeled, the estimation of design-based savings may be the upmost arbitrary and controversial, but the underlying assumption is that the lower the plant size, the higher may be the “Design cost-saving factor”. The dynamic and benefits of the Economy of Multiples of SMR have already been investigated on a case study of a stand-alone Large Reactor (LR) against four SMR deployed on a single site. The two alternative investment projects have been evaluated on their economic performance and profitability. But Economy of Multiples is not a privilege of SMR. This work aims to analyze at what extent and conditions the Economy of Multiples holds against the Economy of Scale, when NPP of different sizes are deployed in multiple units, considering that the Economy of Multiples smoothes its benefits with the increase in number of units installed and that the maximum size of the sites is a limit to its application on LR. The limit case-study of “Very Small Reactors” (VSR) is investigated, representing a massive NPP deployment and a huge loss of Economy of Scale. Our analysis is performed by mean of INCAS (INtegrated model for the Competitiveness Analysis of Small-medium modular reactors) Polimi’s proprietary simulation code. Scenario simulations are run managing the Design cost-saving factor of each SMR fleet size as a parameter; its value is calculated in order to achieve the same level of economic performance of LR investment scenario. In other words we have determined the required design simplification effort needed by each NPP size, in order to attain the economic performance of the equivalent LR deployment scenario. Our results show that the Economy of Multiples holds as a competitive edge for Medium and Small Reactors even when nuclear site may host multiple LR: 8-9% design cost saving is able to grant the same economic performance of a fleet of LR, even with higher construction cost estimates. On the contrary, VSR need to achieve more stretching degree of design simplification and related cost savings (up to 15%) in order to be competitive with LR.