ORNL is a global leader in neutron sciences and operates two of the world’s most powerful neutron sources. HFIR provides one of the highest steady-state neutron fluxes of any research reactor in the world and is used for cold and thermal neutron scattering, isotope production, materials irradiation, and neutron activation analysis. SNS is an accelerator-based system that provides an intense source of neutrons to world-class instruments for neutron scattering applications. In concert with supplementary ORNL world-leading research facilities and modeling and simulation expertise, HFIR and SNS provide a diverse set of tools and expertise needed for neutron-based experiments across a wide range of scientific and engineering disciplines.
Safe, reliable operation of a nuclear facility requires facility-specific modeling and analysis tools and expertise. Nuclear modeling and analysis tools are used for many facility needs, including but not limited to establishing, maintaining, and implementing the safety basis; redesigning components; designing, optimizing, and qualifying experiments; and upgrading instruments. Nuclear facilities must adhere to SQA requirements as a means of preventing defects or mistakes when delivering software to a customer. A configuration-controlled process is required to ensure that the computing software and hardware utilized are appropriately pedigreed. The rigor of SQA required is often dictated by the facility’s regulatory body, the facility’s hazard category level, the software categorization (i.e., safety, research, general software), the software grading level, and the software type (i.e., commercial off the shelf, custom developed).
Software verification is always performed during the SQA process to confirm that the code is working as intended by the original code developers. This typically consists of executing a set of developer-supplied inputs and comparing the results with known solutions. Validation is performed during or after the SQA process to compare calculation results to operating data, experiments, tests, or analytical data to confirm that the code solutions are simulating the phenomena to a reasonable degree of accuracy. Validating methods such as software, models, assumptions, and data are important to ensure that each method is accurate within the facility’s operating conditions and to establish any potential biases.
Nuclear facilities require established production tools (i.e., for neutron and gamma transport, depletion, thermal hydraulics, transient analysis) such as those discussed on the “Production Tools” page for safety-basis
and research needs. ORNL has a very strong background in developing, applying, and deploying modeling and simulation tools. These tools have a high pedigree, a large user base, and their own quality assurance programs, thus providing increased confidence in the software’s ability to support the facility.
Off-the-shelf production tools and data are not always adequate for modeling and simulating unique systems or experiments. Custom-developed tools and data sets such as those described on the “Custom-Developed
Tools and Data” page are thus required to model and analyze these unique and challenging systems. For example, HFIR can be considered a complex reactor because of its unique geometry consisting of involute-shaped fuel plates containing fuel that is contoured across the arc of the involute. The HFIR safety-basis employs the HFIR steady-state heat transfer code (HSSHTC) that was developed for and tailored to analyze HFIR. ORNL is also actively developing HFIRCON, an automated, integrated, flexible, parallel performance–tuned depletion tool for HFIR analysis. This tool is being developed and tested with the commodity computing resources provided by CADES, as described on the “Computing Resources” page. ORNL has also developed a design- and safety-basis thermal-hydraulics model of HFIR in COMSOL for the existing highly enriched uranium core and for the proposed designs of LEU cores to support its conversion in the future.
Most operating facilities have access to small-scale computational clusters that limit an analyst’s ability to perform high-fidelity, computationally intensive calculations. This often results in the analyst making conservative assumptions and simplifications so the computations can complete in a reasonable time. However, making use of state-of-the-art production or custom tools that can accurately model the facility of interest and that can be performance-tuned to large-scale computational clusters results in efficient, high-fidelity modeling and simulation. In turn, more realistic results are calculated which can be advantageous for many reasons, such as reducing conservatism in the facility’s safety basis or increasing the amount of material that can be loaded into an irradiation experiment.
ORNL’s world-class teams provide support and technical analyses to partners and facilities around the globe. A nuclear facility may be constrained by a lack of staff or computational resources or a lack technical expertise in a nuclear field that requires updates or development. With its broad range of expertise, ORNL can provide facility support in many technical areas such as those described on the "Analysis Expertise" page. ORNL provides specialized workshops and software training courses as discussed in “Workshops and Training.” Staff development is important to nuclear facilities to ensure that staff members are informed of ongoing advances in their technical fields, and participation in workshops and training courses is an effective means of continuous training and skills development.
We invite facility operators to learn more about the rich resources available at ORNL through ONRAMP.