Highly Available Nuclear Power in a Microgrid Configuration for the ORNL Distribution System

A previous study concluded that the robust, multimodule design of the NuScale small modular reactor plant can provide power at an unprecedented level of availability to mission critical facilities. This study extends the analysis to include a microgrid power distribution and delivery system to demonstrate the increased availability of power delivered to a customer. A hypothetical 12-module NuScale plant located on the Clinch River site in Tennessee is assumed to supply power from three modules to Oak Ridge National Laboratory (ORNL) through the Tennessee Valley Authority (TVA) transmission system. Combinations of transmission and power generation equipment failures that might interrupt power, and the associated frequency and duration of these failures, are identified and the potential for power interruption to ORNL is evaluated. The analysis first evaluates the existing transmission infrastructure and availability of power to ORNL to establish a baseline availability. Then, a connection from the NuScale plant through the local TVA transmission system (option 1) and a direct connection from the NuScale plant to the ORNL distribution system (option 2) are evaluated, as well as three sensitivity cases. The existing power distribution and delivery system at ORNL is already highly reliable resulting from multiple diverse power generators feeding a robust power delivery system. The primary driver of macrogrid power unavailability is the existing power generation sources, which includes two coal plants and two hydroelectric generators, rather than transmission equipment. Adding a 12-module NuScale plant to the system further reduces the unavailability of power to ORNL by over two orders of magnitude in both cases of considering only local power sources and the macrogrid as a whole. When considering only local generators, the inclusion of a NuScale plant improves the average availability of power to ORNL from three-nines to over five-nines. If the large-scale macrogrid is also included, average availability is increased to nine-nines.