Experimental investigation of alumina coating as tritium permeation barrier for molten salt nuclear reactors

• Published in: Nuclear engineering and design Vol. 353; no. C; p. 110232
• Main Authors: Zheng, Guiqiu, Carpenter, David, Dolan, Kieran, Hu, Lin-wen
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier B.V 01.11.2019; Elsevier BV; Elsevier
• Subjects: Alumina coating; Aluminum oxide; Austenitic stainless steels; Coatings; High temperature nuclear reactors; Lithium; Molten salt; Molten salt nuclear reactors; Neutron flux; Nuclear reactors; Reactors; Salts; Stainless steel; Steel tubes; Thermal neutrons; Transition layers; Tritium; Tritium permeation barrier; Alumina coating; Tritium permeation barrier; Molten salt
• ISSN: 0029-5493; 1872-759X
• DOI: 10.1016/j.nucengdes.2019.110232

•Approximately 11,540 µCi/m3 of tritium generated from molten FLiBe salt.•Measured tritium permeation through bare and alumina-coated SS316 tubes.•Tritium permeability SS316 was significantly reduced by alumina coating.•Alumina coating via plasma thermal spray has excellent thermal stability. This study experimentally investigates the reduction efficiency of tritium permeation through 316 stainless steel tubing coated with alumina as a tritium permeation barrier (TPB) in support of the development of molten salt nuclear reactors, particularly for fluoride salt-cooled high-temperature nuclear reactors (FHRs). The TPB coatings composed ofan intermediate bond layer of NiCr, a transition layer of NiCr + alumina, and a pure alumina layer were successively added onto the outer surface of commercial 316 stainless steel tubing via plasma thermal spray. In order to generate a continuous gaseous tritium source, 35 g of purified natural-lithium FLiBe salt was irradiated by thermal neutron flux at 620 °C in the Massachusetts Institute of Technology Research Reactor (MITR). The preliminary results suggest that the TPB coatings on tube surfaces significantly reduced the tritium permeation rate at 700 °C. To get a better understanding of the TPB, the microstructure of the coated tubes was characterized with various techniques.