CERIUM MODIFIED CONVERSION COATINGS TO PROTECT ALUMINUM CLADDING OF SPENT NUCLEAR FUEL DURING EXTENDED WET STORAGE

摘要

Pitting of Al-clad spent nuclear fuel in wet storage facilities could lead to cladding breach and contamination. Maintenance of water parameters within specified limits does not prevent pitting due to synergism between many water parameters that affect corrosion of aluminum alloys. Five types of coatings for Al alloys have been studied: (i) lanthanide oxides (Ce, La and Pr); (ii) boehmite; (iii) cerium modified boehmite; (iv) hydrotalcite (HTC); (v) cerium modified HTC. This paper will present: (a) preparation of and characteristics of the these coatings on alloys AA 1100 and AA 6061; (b) corrosion resistance of coated alloys in NaCI solutions; (c) results of field tests in which un-coated and coated Al alloy coupons were exposed to a spent fuel storage basin for a year. The cerium modified HTC coatings imparted the highest corrosion resistance. The mechanism of corrosion protection of Al alloys by these coatings and the rOle of cerium is discussed.