Diffusion Coefficients of Metallic Impurities in High Temperature Lead-Bismuth Eutectic

Abstract

One of the most crucial issues in development of the lead-bismuth cooled fast reactors (LFR), and the accelerator-driven system (ADS) is the compatibility of structural steels with liquid lead-bismuth eutectic (LBE) at high temperature range from 500°C to 650°C. In the primary circuit of LBE, metallic impurities such as Fe, Cr and Ni dissolve from structural steels into LBE at high temperature region, are transported to low temperature region, and precipitate as solid metals on channel wall. In this circulation, the data bases of diffusion coefficients of the metallic impurities are required for the estimate of mass transfer rates. In order to investigate the characteristics of diffusion of metallic impurities, the measurement of diffusion coefficients of Ni and Fe in liquid LBE was carried out using a capillary method. The concentrations of the diffusing species in LBE were determined by means of the inductively coupled plasma mass spectrometry (ICP-MS). From the measured axial distribution of Ni and Fe concentration in the LBE, the diffusion coefficient of Ni and Fe were obtained. The results are expressed by DNi=1.7×10-3exp⁡-3.63×10-4/RT500°C≤T≤650°Ccm2/sDFe=3.5×10-3exp⁡-4.15×10-4/RT550°C≤T≤650°Ccm2/s It was found that the value of diffusion coefficient of Ni is similar to the diffusion coefficient of Fe in liquid LBE.