Advances of the AC-DC code, a coupled computational tool to perform thermalhydraulic modeling of fuel bundles with annular fuel elements

• Published in: Nuclear engineering and design 2020-01, Vol.356, p.110360, Article 110360
• Main Authors: Nava Dominguez, A., Rao, Y.F., Beuthe, T.
• Format: Article
• Language: English
• Subjects: Bundles; Bundling; Computer applications; Computer simulation; Fuels; Heavy water; Heavy water reactors; Modular systems; MOX; Nuclear fuel elements; Nuclear fuels; Power reactors; Reactors; Silicides; Software; Thorium; Two phase flow
• ISSN: 0029-5493; 1872-759X
• DOI: 10.1016/j.nucengdes.2019.110360

•Development of a thermalhydraulics algorithm to model fuel bundles containing annular fuels.•Thermalhydraulics assessment of fuel bundles using annular fuel for CANDU type reactors.•Geometry optimization for annular fuel elements.•Improved heat transfer characteristics and potentially safety margins. A new computational tool, the AC-DC code, is presented that couples the two well-established two-phase thermalhydraulic codes ASSERT (a subchannel thermalhydraulics code) and CATHENA (a system thermalhydraulics code). The AC-DC code can be used to model, evaluate, and optimize the thermalhydraulic performance characteristics for advanced fuel bundle concepts involving the use of annular-type fuel elements that are cooled both internally and externally. Such innovative concepts may be potentially implemented in various research and power reactors, including small modular reactors (SMRs), Generation-IV systems, and pressure tube heavy water reactors (PT-HWRs). In this study, AC-DC code is used to simulate the performance of proposed 24-element and 18-element internally-cooled annular fuel (ICAF) bundles in single-phase and two-phase flows. Such ICAF bundle concepts could potentially be implemented in PT-HWRs, in conjunction with the use of high-burnup and advanced fuels, such as (Pu, U)O2 (MOX), thorium-based fuels, metal alloys, nitride fuels, silicide fuels and others. The use of ICAF-type fuels have the potential advantage of reduced fuel temperatures, and enhanced thermalhydraulic margins. The AC-DC code simulation results show excellent agreement with available single-phase experimental results. Two-phase simulations highlight the usefulness of the coupled code to help optimize the performance of proposed ICAF concepts. The results show encouraging performance characteristics for ICAF concepts even using relatively conservative assumptions.