Reactor and Nuclear Systems Division

Advanced Reactor Systems & Safety Group

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The Advanced Reactor Systems & Safety (ARSS) Group supports the design, operation, control, and safety of nuclear systems focusing on the development of next generation reactors for terrestrial and space power applications. We also identify the requisite technologies requiring further R&D to evolve these advanced concepts. The ARSS group's capabilities include both analysis and modeling of reactor power systems combined with technology development and validation of such systems through unique experimental facilities. We are currently supporting DOE's Generation IV (Gen IV) initiative and the Nuclear Regulatory Commission's activities in licensing new plants and the evaluation of operations and license amendments for the existing fleet of commercial nuclear power plants.

The ARSS staff has considerable modeling, analytical, and measurement capabilities for evaluating and optimizing nuclear systems.  The group is capable of system-level modeling as well as larger-scale integrated plant modeling.  The group is adept at performing dynamic response analysis of a plant design by integrating numerous individual modeling codes using tools such as Simulink and Matlab and has developed the Graphite Reactor Severe Accident Code (GRSAC) that can be used to analyze both pebble-bed (PBMR) and prismatic (GT–MHR) designs. Key staff also perform economic assessments including life-cycle costs, cost/benefit, initial facility capital costs, alternative cost comparisons, and production cost simulation.

Members of the ARSS Group are internationally recognized experts in I&C technology. Relevant experience has included the development and assessment of emerging I&C technologies, development and qualification of sensors for harsh operating environments, development of temperature measurement techniques, and implementation of wireless technologies.  We develop hardware for in-loop demonstrations for ultimate integration into an overall system architecture. The group collaborates internationally with experts from South Korea, Japan, Brazil, South Africa, and the IAEA and supports the Nuclear Regulatory Commission (NRC) in evaluating I&C systems.

ARSS staff conducts safety assessments for commercial nuclear plants, advanced reactors, research reactors, and nuclear support facilities including probabilistic risk assessments (PRAs) and failure modes and effects analyses (FMEA). Our staff pioneered the use of PRA techniques to evaluate precursors to potential core damage accidents for NRC. We have also evaluated, through PRA models, the risk attributes of an advanced CANDU reactor (the ACR-700) for NRC. We have developed a tool for applying PRA techniques during the design phase for reactor systems, the Risk-Based Design Optimization Tool (RBOT), and have considerable experience with the SAPHIRE and Fault Tree+ PRA codes.

At ORNL, ARSS staff is involved in testing and experimental activities that complement our analytical capabilities. Two key areas include our Reactor Technology Lab (RTL) and I&C Sensor Development Lab (SDL). The focus of the RTL is to conduct R&D in a flexible bench-scale mode for liquid metals related to the production of electrical power at high temperatures and low pressures for terrestrial and space power reactor applications. Work at this scale is then evolved to larger facilities to perform larger-scale, forced-flow testing. Incorporated within the RTL is an I&C test bed to support the development and assessment of new I&C control systems and algorithms. Here, signals identical to those produced from plant sensors are generated to simulate acquisition and processing by representative control systems. In the SDL, new measurement and detection techniques are developed and tested. Novel detector materials for measuring temperature, level, and radiation are developed. The SDL is designed to support testing and experiments that involve high temperatures, high voltages, use of lasers, use of sealed radiation sources, and fabrication of detector materials.