Nuclear Science


Small Modular Reactors

Nuclear Science research supports the Department of Energy (DOE) Office of Nuclear Energy and the Nuclear Regulatory Commission (NRC) in understanding research and development, technical, and regulatory issues for near-term Small Modular Reactors (SMRs) based on light-water reactor technologies and longer-term SMRs based on advanced reactor technologies. Research on SMRs involves expertise in materials science, instrumentation and controls, reactor technology, reactor operations and safety, and reactor licensing and regulation to help develop and deploy SMRs as a major source of energy for the future.


ORNL provides technical leadership and performs research in support of the DOE Advanced SMR program in several areas.  ORNL develops and evaluates new materials for higher temperature applications through understanding the long-term degradation mechanisms. This knowledge may eliminate unnecessary conservatism and provide more flexibility in the design and operation of SMRs. Research is also underway to develop advanced instrumentation for critical temperature measurements in extremely harsh conditions because sensors and instruments will operate much closer to the core in small reactors. Scientists are formulating advanced control methodologies to enable higher levels of automated operation and control of multi-module plants with an optimized number of staff. Complex engineering economic analyses is being conducted to model the effects of modular fabrication and the learning curve effect of “nth” of a kind fabrication of SMRs in a factory setting to illustrate the anticipated economic advantages of SMRs. Geographic Information Systems (GIS) and spatial modeling tools are being used to perform initial SMR site suitability analyses and evaluate options for deployment of SMRs in the future. Finally, a set of flexible, re-configurable models is being developed to provide the capability to dynamically simulate and evaluate new advanced SMR concepts by creating a common modeling platform and environment.


SmAHTR - ORNL's Advanced High- Temperature SMR Concept

ORNL has been instrumental in supporting NRC in the development and demonstration of a new regulatory framework for licensing SMRs that relies on risk-informed processes that are to be used by the NRC staff in review of SMR design certification applications. This approach more fully integrates the use of risk insights into pre-application activities and the review of SMRs and is a significant change from the NRC current review process. Specifically, this new approach involves the categorization of SMR systems, structures, and components (SSCs) as safety-related and non-safety-related. The NRC is taking a graded approach with the most detailed, in-depth review conducted for SSCs determined to be both safety-related and risk-significant, and a progressively less detailed review applied to SSCs determined to be non-safety-related or not risk-significant.

ORNL has also developed an advanced SMR concept based on the Fluoride High-temperature Salt-cooled Reactor (FHR) technology. The Small modular Advanced High-Temperature Reactor (SmAHTR) is a 125 MWt, integral primary, liquid salt cooled, coated particle-graphite fueled, low-pressure system operating at 700 °C that employs passive decay heat removal. This reactor can be used for scalable electricity generation or as a source of high-temperature process heat.

For More Information, Contact:

Group Leader, Advanced Reactor Systems and Safety
Gary Mays

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