The helium-cooled high temperature reactor (HTR) and Very High Temperature Reactor (VHTR) designs operate at exit temperatures ranging from 873 – 923 K and 1,123 – 1,223 K, respectively. The high exit temperatures and the low heat capacity of helium require operating at a high flow velocity (> 70 m/s). The high temperature and flow velocity of the helium jets exiting the coolant channels in the prismatic reactor’s lower plate in the lower plenum (LP) cause “hot spots” (“hot streaking”) and stratification. To minimize or eliminate hot streaking and enhance mixing, this work investigated using static, quadruple helicoid inserts at the exit of the coolant channels. The helicoid inserts introduce radial and azimuthal momentum flow components, which with the extensive entrainment and mixing of the surrounding gas, significantly reduce the impingement onto the lower plate, thereby minimizing hot streaking and stratification in the LP. The present analysis was conducted using FUEGO, Sandia National Laboratories’ 3D, finite element, incompressible, reactive flow, massively-parallel code with state-of-the art turbulence models. We used helium at 1,273 K and the dynamic Smagorinsky turbulence model.
On Eliminating ‘Hot Streaking’ and Stratification in the VHTR Lower Plenum Using Helicoid Inserts
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Rodriguez, SB, & El-Genk, MS. "On Eliminating ‘Hot Streaking’ and Stratification in the VHTR Lower Plenum Using Helicoid Inserts." Proceedings of the Fourth International Topical Meeting on High Temperature Reactor Technology. Fourth International Topical Meeting on High Temperature Reactor Technology, Volume 1. Washington, DC, USA. September 28–October 1, 2008. pp. 783-791. ASME. https://doi.org/10.1115/HTR2008-58292
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