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Fact Sheet
 Mission Focus
The Advanced Reactor Systems & Safety (ARSS) Group is working on the design, operation, control, and safety of the next generation nuclear systems focusing on terrestrial and space power applications. Also, we are working to identify the requisite R&D and technologies to develop these advanced concepts. The ARSS group’s capabilities include both analysis and modeling of reactor power systems and also technology development and validation of such systems through unique experimental facilities.
Reactor Systems Engineering
 The ARSS staff has considerable design analysis, 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. GRSAC is a 3-D, 3000-node model for evaluating accidents. The group also has mechanical design capabilities using tools such as Autocad, Pro-E, and VectorWorks.
Instrumentation and Controls
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 in evaluating I&C systems.
Facility Safety Assessment
ARSS staff are experienced in conducting a variety of safety assessments for commercial nuclear power plants, advanced reactors, research reactors, and nuclear support facilities including probabilistic risk assessments (PRAs) and failure modes and effects analyses (FMEAs). Our staff pioneered the use of PRA techniques to quantify the significance of events considered to be precursors to potential core damage accidents for NRC. We recently provided support to NRC in evaluating the PRA as submitted as part of a preapplication licensing review of an advanced CANDU reactor, the ACR-700. We have developed a tool for applying PRA techniques during the design phase for reactor systems, the Risk-Based Design Optimization Tool (RBOT), that has been applied to make design improvements relative to safety and reliability for both space fission power systems and Westinghouse’s IRIS small reactor design.
We have and continue to be integrally involved in assessing safety issues for lunar fission power systems as well as nuclear thermal propulsion systems for NASA.
Regulatory Support
ARSS staff has been supporting NRC for over 25 years in its regulation and oversight of commercial nuclear power plants. This support has included the development of key data systems and performance indicators as part of our efforts in performing operating experience reviews. We continue to have the core staff in place who, for the past 20 years, have analyzed event data and documented lessons learned from commercial nuclear power plant operations. Our analysis tool (PRINCE—the system formerly known as SCSS) has 5 million plus operating experience records developed from the analysis of 50,000 LERs. Our analysts have worked in the commercial nuclear industry and possess a keen understanding of plant operations and safety to be able to develop insights and identify trends based upon evaluations of operating experience including nonconformance reports, plant start-ups, operational readiness reviews, LERs, etc. Our staff is currently supporting NRC in updating selected Standard Review Plan (SRP) sections, including such topics as overpressure protection for PWRs, ESBWR isolation condensers, reactor core isolation cooling (RCIC) system, standby liquid control system, I&C, and ITAAC. ARSS staff also have licensing experience based upon commercial nuclear power plant experience as well as supporting DOE in its efforts to obtain a license in the United States for a mixed-oxide (MOX) fuel fabrication facility and its efforts to assist Russian regulatory entities to identify the necessary changes to license a comparable MOX facility in Russia as well as various reactor types to be modified to use MOX fuel. An ARSS staff member is currently a member of a DOE team examining the licensing issues and strategies for burner reactors that are a part of DOE's Global Nuclear Energy Partnership (GNEP).
Engineering Economics
ARSS staff has an extensive background in performing economic assessments including life-cycle costs, cost/benefit, initial facility capital costs, alternative cost comparisons, and production cost simulation. We have developed cost estimates for various size reactors, fuel cycle facilities, and fission systems for space reactors. Currently, an ARSS staff member is participating as part of DOE’s economic evaluation team for its Global Nuclear Energy Partnership (GNEP) program and its Generation IV program on advanced reactors.
Generation IV Nuclear Program Support
 ARSS is supporting the Department of Energy's Gen IV program in developing a dynamic systems model for the Liquid Salt–Very High Temperature Reactor (LS–VHTR) to support design analysis reviews to evaluate candidate coolant-salts, design requirements for components, control system options, and passive safety systems. The LS–VHTR, an ORNL design concept, is considered a variant of the VHTR. For the VHTR, we are developing simulation models and methods to support thermal hydraulic and safety analyses.
Space Power Program Support 
The ARSS Group provides ongoing support to the Department of Energy’s (DOE) Space Reactor Technology Program that is supporting NASA’s Vision for Space Exploration (VSE). Conceptual reactor designs for surface power applications for both the moon and Mars have been developed as well as conducting analyses of reactor concepts for nuclear thermal propulsion (NTP) and nuclear electrical propulsion (NEP). ARSS staff has developed specialized techniques for performing design optimization and design alternative reviews. In addition to design support, the group has developed independent cost estimates, power system mass estimates, preliminary integrated test plans, and reactor prototype testing plans.
Experimental Facilities
 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 evolving 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.
Key Capabilities
The group has advanced degrees in nuclear, mechanical, chemical, and industrial engineering as well as having operational reactor experience from the U.S. Navy, commercial reactors, and research reactors. Specifically, we have experience in
- reactor design evaluation,
- reactor control system design and operation,
- probabilistic risk assessments using analysis tools such as SAPHIRE and Fault Tree+,
- space power systems
- operating experience assessments,
- engineering economics, and
- gas-cooled reactor safety.
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