Experimental Investigation of Hfir Fuel Plate Deflections Induced by Temperature and Pressure Differentials.

3D COMSOL Simulations for Thermal Deflection of HFIR Fuel Plate in the "Cheverton-Kelley" Experiments

“…Transverse (or radial) deflections follow a parabolic profile with peak deflection occurring in midspan of the plate. As shown, longitudinal deflection (along the direction of plate's length) retains its uniform parabolic shape throughout the plate's length with steep gradients at the top and bottom ends [19]. …”

“…A total of 13,000 gal of water passes through the HFIR core every minute. Even then there is a possibility of developing unwanted hot regions within the HFIR fuel elements [17,19,20] for the following reasons: manufacturing tolerances in fuel plate dimensions, thermal expansion of plates due to radially and axially varying time-dependent heat generation rates, possible local segregation of fuel and nonbonds with cladding, extension of fuel-bearing material beyond its nominal boundaries, pressure-and turbulence-induced structural deflections, buildup of oxide layers on the plate surfaces, etc.…”

“…The critical buckling stress depends upon several system parameters, including plate temperature (material properties), initial geometry, the means of edge attachments to side plates, and temperature distribution in both the fuel plate and the side plate. Due to this possibility, in 1968 Cheverton and Kelley experimentally investigated [19] the differential thermal expansion of a HFIR fuel plate with a viewpoint that it could buckle under HFIR operating conditions. However, buckling was never observed in their tests and has not occurred at any time during HFIR's long history of operation.…”

“…To investigate the possibility of buckling in HFIR fuel plates, Cheverton and Kelley designed an experiment [19] in 1968 to generate thermal stresses in a HFIR fuel plate and measure its differential thermal expansion (see Figs. 3 through 6).…”

“…In SSHTC, thermal structural interaction (TSI) physics is incorporated via empirical correlations derived from the experimental thermal deflection data produced by Cheverton and Kelley in 1968 [19] (called the "Cheverton-Kelley" tests). The correlations were developed for the HEU fuel plate in a convectively heated environment and may not be directly applicable for the U-Mo LEU plate.…”