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We investigated the effects of exogenous sodium pyruvate (SP) on adipocyte differentiation, lipid accumulation, and the mRNA expression levels of adipogenesis-related genes in 3T3-L1 pre-adipocytes. Differentiation of pre-adipocytes was induced by MDI (3-isobutyl-1-methylxanthine: IBMX, dexamethasone: DEX, and insulin), in the presence or absence of SP. Adipogenesis was stimulated by SP in a concentration-dependent manner. SP also induced the expression of genes encoding aP2, GLUT4, and adiponectin, but had no effect on cell proliferation. Exogenous glucose did not promote adipogenesis or lipid accumulation. 2-deoxy-D-glucose inhibited adipogenesis initiated by MDI, but failed to influence the effects of SP on adipogenesis, whereas 3-bromopyruvate inhibited adipogenesis regardless of whether SP was present. The pro-adipogenic properties of SP were limited to the early events of adipogenesis. To determine whether SP mimics the adipogenic action of dexamethasone or insulin, we examined the effects of SP on adipogenesis with combinations of IBMX, DEX, and insulin. SP did not improve incomplete lipid accumulation observed in cells grown under IBMX-, DEX-, or insulin-free conditions. Insulin-stimulated ERK1/2 phosphorylation was diminished by SP, while phosphorylation of Akt was increased, correlating with increased glucose uptake in response to insulin. We also observed that SP stimulated immediate early expression of C/EBPβ and C/EBPδ. The PPARγ antagonist GW9662 inhibited adipogenesis. Our findings highlight the adipogenic function of exogenous SP by stimulating early events of adipogenesis.

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Since the fuel is always exposed to turbulent flow, the grid strap shows flow induced vibration characteristics that impact on the nuclear fuel soundness. The dynamic behavior of grids in nuclear fuels is quite complex, since two pairs of spring and dimple support are contacted with rods by friction in the limited space. This paper focuses on investigation of the grid strap(test fuel strap, TFS) vibration in one cell. TFS consists of a single spring and double dimples. To identify the grid strap vibration, modal analysis of the strap is performed using finite element method(FEM). Modal testing on a 5×5 grid structure without rods is performed. The modal testing results are compared to analytic results. In addition, random test considering rod effect is performed about a 5×5 grid with rods under real contact condition in the air. Finally, the strap vibration of a 5×5 fuel bundle in inves-

Spent nuclear fuel (SNF) integrity evaluation related to its handling and transportation for mid-/long-term dry storage is a regulatory requirement. Especially, a drop event is the most fatal failure mode among regulatory conditions. For SNF drop accidents, it is required that the mechanical integrity of the SNF be evaluated using test results or analytic methodologies. The SNF mechanical test, however, takes much time and cost, and there are safety issues related to the release of radioactive materials. Thus, finite element analysis is used as an alternative to the experimental test method to solve this problem. In this study, a three dimensional (3D) finite element model was developed using ABAQUS software to simulate the structural behaviors of a fresh fuel assembly (FA) prior to applying SNF properties because of a lack of SNF test results. Static and dynamic mechanical behaviors were simulated with this model and compared with the fresh FA test results. The analysis results are in good agreement with the test results. Therefore, the analysis model consistent with the test results will be applied to the evaluation of the FA drop integrity reflecting the specific SNF characteristics.