Corrosion Study of Simulated Evaporator Components.

摘要

At the Los Alamos Plutonium Facility, ion exchange effluents and precipitation filtrates containing discardable levels of transuranic elements are concentrated using a thermosiphon evaporator before cement fixation for waste disposal. Because of changing process feed streams and scrap recovery requirements, trace amounts of free chloride ions Cl- are being introduced into the stainless steel (SS) evaporator, potentially increasing corrosion rates and thereby reducing its useful life. This study was performed to determine the effects of Cl- in simulated evaporator feed solutions that contain significant amounts of ferric ions Fe3+ in nitric acid HNO3. A simulated environment was produced by heating 316 SS cans that contained various tests solutions. The surface was monitored for signs of pitting or stress cracking, and vessel weight loss was measured on a daily basis to establish a rough corrosion rate. The final conclusion is that the nitric acid solution provides enough free nitrate ions NO3- to maintain minimal corrosion in a dilute ferric chloride environment. 3 refs., 5 figs., 10 tabs.