2026/03/26 by Taylor Benson, Joseph Seo, Brent Hollrah +3
Engineering · Materials Science · #Nuclear Engineering Thermal-Hydraulics #Nuclear Materials and Properties #Nuclear reactor physics and engineering
paper · doi:10.1080/00295450.2026.2631245
crossref issued 2026/03/26 · crossref published 2026/03/26 · crossref published-online 2026/03/26 · openalex publication_date 2026/03/26 · crossref created 2026/03/26 · crossref deposited 2026/03/26 · openalex created_date 2026/03/27 · crossref indexed 2026/07/30 · openalex updated_date 2026/07/30
The reactor vessel auxiliary cooling system (RVACS) of the PRISM (Power Reactor Innovative Small Module) provides a passive means for decay heat removal, primarily through radiative and convective heat transfer. We assess experimental scalability using a reduced-order one-dimensional (1D) nodal heat transfer model and validate it against higher-fidelity two-dimensional (2D) and three-dimensional (3D) simulations. The models solve heat flux by balancing radiative, conductive, and convective heat transfer along the reactor vessel (RV) wall, guard vessel wall, air flow in the riser, and duct wall under steady-state conditions representative of post-scram or reactor shutdown operations.Dimensional analysis and similarity laws, mainly utilizing Richardson number scaling, are applied to ensure consistency between the buoyancy-driven flow behavior between the full-height reactor and that of the experimental scaled-down systems. Using the RV inner wall temperature of 922 K as the primary metric, the 1D model underpredicts the 2D and 3D simulation heat flux values for full-reactor height by 6.05% and 17.36%, respectively. The deviation increases to 17.59% for 2D and 25.29% for 3D at 1/6 height scaling, which is attributable to the inlet and outlet effects and the flow structures of the 2D and 3D models. Both the 2D and 3D scaled models follow the Richardson number scaling trends, with heat flux relative errors reaching maximum values of 14.00% and 10.61% at 1/6 scaling, confirming the strong agreement with the scaling temperature value calculated from the 1D model.The findings demonstrate the ability for a reduced-order 1D nodal framework to sufficiently model the early-stage design and experimental scaling of the RVACS for configurations dominated by radiative heat transfer, shown for geometric scaling of 1/6 or greater, providing an efficient and cost-effective tool for assessing passive decay heat removal performance with a reduction in computational costs.The approach assumes fully developed axial behavior, as it does not explicitly resolve the inlet and outlet effects, which become increasingly pronounced at smaller scale ratios. The methodology is broadly applicable to other passive decay heat removal systems, such as reactor cavity cooling systems and other air-cooled safety designs governed by radiative and natural convection heat transfer.