Corrosion studies of a stainless steel structure for the ITER aqueous lithium salt blanket concept

Abstract

The aqueous lithium salt blanket (ALSB) employs water, with a dissolved lithium compound, as both the coolant and tritium breeding medium. The ALSB concept is one of three blanket options currently being examined for breeding tritium in the International Thermonuclear Experimental Reactor (ITER). To provide data and recommendations for materials and chemistry selection relevant to application of the ALSB in ITER, corrosion studies have been initiated, focusing on type 316 stainless steel in lithium hydroxide and lithium nitrate solutions. This paper presents the preliminary results of these corrosion studies. The results to date, while preliminary, suggest that even at 90°C, a blanket utilizing 10% LiOH (the current lithium salt of choice for ITER ALSB applications) will not cause catastrophic failure of 316 stainless steel by either stress corrosion cracking or localized corrosion; that the general corrosion rate will not exceed about 40 μm/y and transport of material will certainly be much less than this value since most of the corrosion product will be included in the strong adherent surface film; and that, although hydrogen may be evolved due to electrolysis, the maximum amount of hydrogen is small compared to that expected to be produced by radiolysis. These observations are predicated on the assumption that the blanket will be completely deaerated, and that the corrosion potential of the alloy will be similar to that observed in the laboratory.