The Tennessee Valley Authority (TVA) provides operational experience and validation information to CASL. Many of the CASL staff are highly skilled in their nuclear energy-relevant area of expertise, but not necessarily operational experience typified by the day-to-day issues encountered in commercial reactors. For example, the physical process of removing the fuel from the core, inspecting it, and then repacking it for the next cycle, which for TVA is planned for months in advance and the fuel inspections are crucial for ensuring the next cycle operates optimally. The videos captured by TVA during these inspections have provided information to the CASL staff about current fuel performance and may also help validate some of the codes produced; for example, CRUD (Chalk River Unidentified Deposits) predictions with the virtual reactor can be validated through these inspection videos.
TVA also provides cycle design information and core performance information that allows CASL to benchmark the new codes. Right now, the CASL Advanced Modeling Applications (AMA) Focus Area is simulating Watts Bar cycles 1 through 3. The simulation will include tightly coupled neutron transport and fluid flow calculations that should allow for a very good comparison between the code results and the actual power and temperature readings taken in the reactor during those cycles. Once the fuel rod mechanics tools are coupled with the neutron transport and fluid flow, the virtual reactor will be able to very accurately simulate local conditions anywhere in the core.
One of TVA’s primary roles in the CASL project is to ensure that the broad nuclear energy industry benefits from the program - not just CASL industry partners, but the commercial nuclear industry in general. Towards that end, TVA continues to reach out to other nuclear utilities, EPRI, and the domestic fuel vendors. TVA, for example, recently hosted a meeting to discuss fuel-related limitations to power uprates. The discussion identified several specific physics-based models that, if developed by CASL and included in the virtual reactor, could facilitate future reactor power uprates. The CASL plan is to schedule a follow up meeting with a wider utility participation to validate these and other CASL activities.
TVA and several other utilities also participate in CASL’s Industry Council. This council is led by EPRI and provides a direct conduit for feedback and suggestions. The council has suggested that CASL launch some pilot projects as a useful demonstration of the virtual reactor’s capabilities, and we are hoping to begin our first pilot simulation this summer. Since the pilot projects are focused on current issues, the industry should receive immediate benefits. With ORNL’s Jaguar supercomputing capability (insert URL here), CASL has the computer power it takes to provide insights and solutions on these very large simulations.
Today, industry does the majority of its calculations in a non-coupled methodology, and this results in some inaccuracy due to the application of conservative assumptions and boundary conditions. With the coupled capability, these inaccuracies can be identified and quantified. It is likely that the better understanding of the system uncertainties and sensitivities afforded by the virtual reactor will identify improvements in both the operation and design of the fuel that will benefit utilities, fuel vendors and consumers.
TVA’s experience with the hub collaboration has been very positive. There were some significant hurdles to overcome at the beginning of the project related to intellectual property agreements, but the resulting integrated team has the talent and the resources to make a significant contribution to the nuclear industry. The inclusion of the industry ensures that the technology developed is both useful and transferable. In fact, there are several other opportunities where the hub concept would enhance and expedite DOE research. One example is the advanced nuclear fuel development effort. There is a lot of basic R&D that is needed, along with irradiation in test reactors, and DOE has the expertise and facilities for that type of work. However, eventually the advanced fuel must be manufactured and operated in a commercial power plant, and for those activities industry must be involved. It makes good sense to have industry and DOE collaborating early on to get the right development plan and focus.