Elemental mapping of structural materials for a nuclear reactor by means of LA-ICP-MS

Abstract

Laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) was applied to the study of the interaction of molten LiF–NaF salts with candidate structural materials for a nuclear reactor-transmutor cooling circuit. At a working temperature of 680 °C structural materials of heat exchangers are attacked and the melt–alloy interaction provokes microstructural and composition changes of the contact surface. The resulting corrosion-influenced zones were studied by LA-ICP-MS and the maps of elemental distribution were created on the semiquantitative level using the procedure based on the normalization of particular isotopic signals to the sum of signals of all isotopes present in the examined zone. Consequently, LA-ICP-MS signals were measured for structural material constituents (Ni, Cr, Fe, W, Mo, Ti, and Mn) and for cationic constituents of the cooling medium (Li and Na). The hypothetical fluorine signal was calculated as a sum of Li and Na signals. Corrosion products in the exposed cooling medium were determined by ICP-OES after dissolution. Of the three examined candidate structural materials (pure nickel, nickel-based alloy A071EV and nickel-coated iron) pure nickel exhibits the best resistance.