Nuclear energy is a tremendous technological success story for the United States. The first full-scale nuclear-powered electrical production plant at Pennsylvania's Shippingport Atomic Power Station was online in 1957, just 25 years after English physicist James Chadwick established the neutron’s existence. However, in recent years, accelerated and translational R&D from fundamental discovery to commercialized technology has proven challenging for nuclear energy; innovations have been few and far between in the inherently conservative and regulatory-driven industry.
To accelerate nuclear energy modeling and simulation R&D, the U.S. Department of Energy (DOE) established the Consortium for Advanced Simulation of Light Water Reactors (CASL) as its first DOE Energy Innovation Hub in July 2010. DOE Energy Innovation Hubs focus on a single topic, with the objective of rapidly bridging the gaps between basic research, engineering development, and commercialization.
Modeling and simulation (M&S) technology is a mainstay in the nuclear industry. It informs consequential nuclear power operational and safety decisions. The slow evolution of commercial nuclear technology and its strong dependence on M&S are driven by the industry’s limited ability to perform frequent full-scale irradiated experiments due to cost, safety and feasibility, and economic uncertainties. Even advanced light water reactors (e.g., ESBWR, AP1000, EPR, SMR) rely on the current nuclear industry M&S technology, which, though continuously improved and central to the industry’s evolution, has not sufficiently capitalized on the benefits that more precise predictive simulation and fundamental understanding offer. Opportunities for reduced uncertainties in design and operating margins, as well as operating cost reductions and plant lifetime extension, are lost due to the lack of technology progression and leadership in the industry’s M&S. CASL’s mission is to recapture the benefits of leadership in M&S for nuclear technology by providing coupled, high fidelity, usable capabilities needed to address light water reactor (LWR) operational and safety performance-defining phenomena.
Today, with access to the nation’s leading supercomputing facilities, CASL has the virtual capability to look closely at reactor core models operating with 193 fuel assemblies, nearly 51,000 fuel rods, and about 18 million fuel pellets. These elements exist in a high-temperature, high-pressure, high-radiation environment for 3 to 5 years, and our software can simulate these conditions and predict performance.
The simulation legacy at Oak Ridge National Laboratory was established during the Manhattan Project in the 1940s. Modeling and simulation is a backbone in the nuclear industry, perhaps more than in most other science and engineering fields, towards the requiring the construction of costly beta/proto-type facilities for proof of concept and initial licensing. CASL's Energy Innovation Hub is sustained by ten founding partners and supported by many additional partners. The CASL lead institution is Oak Ridge National Laboratory (ORNL), which was founded to develop the world’s first nuclear fuel cycle and today is DOE’s largest science and energy laboratory. ORNL has world-leading capabilities in computing and computational science and substantial programs and assets in nuclear energy R&D, as well as a record of accomplishment in leading large-scale scientific collaborations. The participation of Idaho National Laboratory (INL), Los Alamos National Laboratory (LANL), and Sandia National Laboratories (SNL) as CASL partners provides exceptional strengths in fundamental science, nuclear energy R&D, transformational HPC technology, and development of models and algorithms for the solution of complex problems. Academic partners North Carolina State University (NCSU), the University of Michigan (UM), and the Massachusetts Institute of Technology (MIT) are leaders in nuclear engineering R&D and education. The Electric Power Research Institute (EPRI) conducts R&D to ensure that nuclear power remains a safe and economically feasible generation option and provides CASL with connections to nuclear power plant operators, regulatory agencies, and other research organizations. Westinghouse Electric Company (WEC), a pioneer in nuclear power, has a long and successful history of supplying leading-edge nuclear technology. The Tennessee Valley Authority (TVA) operates six reactors (3 PWRs and 3 boiling water reactors (BWRs)) that provide more than 6,900 MW of electricity to the grid.
CASL leverages a broad range of industry and science advisors through implementation of an independent Science Council and Industry Council to review and advise on quality and relevance of its science and technology. CASL’s Board of Directors (BoD) provides oversight and advice on management, plan, and science and technology strategy; the CASL BoD was chaired during its first two years by Ernest Moniz, current Secretary of Energy, and is currently chaired by Dale Klein, former Chairman of the NRC.”
Nuclear energy is by far the largest clean-air energy source in the U.S. and the only source that produces large amounts of electricity around the clock. It is a secure source not subject to changing weather conditions, unpredictable fuel cost fluctuations, or over-dependence on foreign suppliers. Nuclear energy facilities produce no air pollution and do not emit greenhouse gases. As the U.S. moves toward a clean-energy, low-carbon economy, nuclear energy must continue to be a part of the energy mix. And yet many challenges remain for nuclear energy—both for the existing U.S. fleet as well as for new reactors; improvements must be made in economics and performance. The future of the commercial nuclear power industry hinges upon furthering power uprates, realizing higher fuel burnup, and operating the existing plants for longer lifetimes—all while providing higher confidence in enhanced nuclear safety.
CASL’s ModSim technology, the Virtual Environment for Reactor Applications (VERA), provides higher-fidelity results than the current industry approach by incorporating coupled physics and science-based models, state-of-the-art numerical methods, modern computational science, integrated uncertainty quantification (UQ) and validation against data from operating pressurized water reactors (PWRs), single-effect experiments, and integral tests.CASL's Virtual Environment for Reactor Applications (VERA) includes the major physical phenomena within an operating commercial power reactor (neutronics, thermal-hydraulics, thermo-mechanics, coolant chemistry) and implements modern computing infrastructure to achieve higher fidelity solutions.
CASL's focus is on challenges that originate within commercial power reactor vessels (i.e. the reactor core, the reactor vessel itself, and the in-vessel components) of pressurized water reactors (PWR), the most common type of light water reactors (LWR) in the United States. The set of specific problems, termed "Challenge Problems," that CASL technology is built to address encompass the key phenomena currently limiting the performance of pressurized water reactors.
To be considered as a Challenge Problem, the problem must be important to the nuclear industry and amenable to, or enabled by, modern M&S techniques. The problems, with specific R&D objectives and metrics, target the predictive simulation and fundamental understanding of specific PWR phenomena present in both normal reactor operations (quasi-steady state) and design basis accidents (transients).
Given the technologies broad range, it is likely that much of the capability developed by CASL will be applicable to other types of nuclear reactors. The Challenge Problems are selected to provide the nuclear power industry with tools for delivering improved performance with enhanced safety. CASL’s focus on high-precision predictions of the onset and evolution of fuel damage directly supports the analysis of accidents like the one that took place at Japan’s Fukushima Daiichi reactors in 2011.